[{"content":" Daily Overview: Dear readers, today\u0026rsquo;s rapid overview of the nickel-based superconductivity field presents a core research advance: using ultralow-temperature scanning tunneling microscopy/spectroscopy, researchers have for the first time observed an energy-symmetric flat-bottomed U-shaped superconducting gap in (La,Pr)₃Ni₂O₇ thin films, confirming its nodeless gap nature. This gap exhibits zero density of states at extremely low temperatures, evolves into a V-shape as temperature increases, and is suppressed by magnetic fields, behaving consistently with conventional superconducting gaps. This discovery reveals a new mechanism for high-temperature superconductivity in double-layer nickelates, offering insightful clues for achieving even higher-temperature superconductivity under ambient or zero pressure. Apart from this closely related paper, the remaining articles do not involve nickel-based superconductivity.\n1. Observation of flat-bottom U-shaped energy gap in high-Tc nickelate (La,Pr)3Ni2O7 thin films Relevance Score: 5.9407 Authors: Zhen Liang, Tianheng Wei, Wei Ren, Haoran Ji, Zheyuan Xie, Yanzhao Liu, Ziqiang Wang, Jian Wang Affiliations: Boston College, Hefei National Laboratory, Quantum Science Center of Guangdong-Hong Kong-Macao Greater Bay Area, Collaborative Innovation Center of Quantum Matter, Peking University Link: http://arxiv.org/abs/2605.15703v1 Summary: Using ultra-low-temperature scanning tunneling microscopy/spectroscopy and electrical transport measurements, this study reports for the first time the observation of an energy-symmetric flat-bottom U-shaped gap with zero residual density of states near the Fermi level in high-temperature superconducting nickelate (La,Pr)₃Ni₂O₇ thin films grown on SrLaAlO₄ substrates. The films exhibit zero-resistance superconducting behavior both before and after measurements, with an onset superconducting transition temperature above 40 K and a zero-resistance temperature above 20 K. The temperature evolution of the tunneling spectra reveals unconventional features: as the temperature increases from 60 mK to 10 K, the U-shaped gap rapidly fills and evolves into a V-shaped gap; meanwhile, the U-shaped gap is suppressed under a 14 T magnetic field applied along the c-axis. The symmetry of this U-shaped gap and its dependence on temperature and magnetic field are consistent with superconducting gap behavior, indicating a nodeless gap function at extremely low temperatures. This discovery reveals new characteristics of bilayer nickelate high-temperature superconductivity and provides inspiring clues for realizing localized superconductivity above the boiling point of liquid nitrogen under ambient or zero pressure.\n2. Effective increase of a superconducting critical temperature in a high-entropy electron mixture Relevance Score: 3.9902 Authors: Viktoriia Kornich Link: http://arxiv.org/abs/2605.15834v1 Summary: This paper proposes a theoretical method to effectively enhance the superconducting critical temperature through high-entropy electron mixtures. The authors consider a solid solution composed of two types of atoms, where one type provides conduction band electrons and the other provides valence band electrons, forming a randomly distributed mixture of conduction and valence band electrons with mixing entropy. To incorporate mixing entropy into the dynamics of the superconducting phase, they suggest using metal traps to absorb quasiparticle excitations in the superconductor, thereby making the concentration of Cooper pairs a dynamic variable of mixing entropy. This mechanism modifies the Ginzburg-Landau functional of the superconductor, effectively reducing the first expansion coefficient, which is equivalent to raising the critical temperature. Parameter evaluations show that when the electron density and temperature satisfy certain conditions, the entropy correction term can become comparable to the original coefficient, thereby significantly influencing the critical temperature. Furthermore, the authors analyze the superconducting equilibrium process and indicate that the energy gap of the Higgs mode can serve as a direct probe of this effect, while physical quantities such as the London penetration depth can also be used for detection. Based on the Ginzburg-Landau phenomenological theory, this approach is universal and may be applicable to a variety of materials.\n3. A practical Laser-Heated Diamond Anvil Cell synthesis technique and recovery workflow for metastable MnSb2 and YbZn2 phases Relevance Score: 3.9601 Authors: S. Huyan, R. F. S. Penacchio, D. Zhang, Z. Li, S. L. Morelhão, Raquel Ribeiro, P. C. Canfield, S. L. Bud\u0026rsquo;ko Affiliations: University of Chicago, University of São Paulo, Iowa State University Link: http://arxiv.org/abs/2605.16039v1 Summary: This paper presents an integrated laser-heated diamond anvil cell (LHDAC) synthesis and recovery workflow capable of stabilizing and retrieving metastable intermetallic phases for subsequent structural and transport studies. Using this approach, high-pressure MnSb₂ and YbZn₂ phases were successfully synthesized at moderate pressures, with synchrotron X-ray diffraction and spatial mapping confirming the dominant formation of the target phases, while laboratory refinement quantified the phase fractions. High-pressure transport measurements on the recovered samples reveal pressure-tunable electronic instabilities in both systems: in MnSb₂, pressure suppresses two high-temperature magnetic ordering anomalies within 5 GPa, and higher pressures induce a low-temperature feature that strengthens with increasing pressure; in hexagonal high-pressure YbZn₂, an electronic reconstruction occurs at approximately 11 GPa, characterized by semiconducting-like behavior from about 30 K to 300 K and a broad low-temperature coherence crossover near 30 K. These results demonstrate that LHDAC synthesis serves not only as a structural discovery tool but also as an experimental platform for studying correlated quantum states stabilized far from thermodynamic equilibrium.\n4. Long-range magnetic ordering and structural phase transition in disordered high-entropy spinel chromites Relevance Score: 3.7350 Authors: Sushanta Mandal, Koushik Chakraborty, Isha, Arvind Kumar Yogi, S. D. Kaushik, Sourav Marik, Tirthankar Chakraborty Link: http://arxiv.org/abs/2605.16106v1 Summary: The structural and magnetic evolutions with temperature of two Cr-based high-entropy spinel oxides, (Mn0.2Co0.2Ni0.2Cu0.2Zn0.2)Cr2O4 and (Mg0.2Co0.2Ni0.2Cu0.2Zn0.2)Cr2O4, were systematically investigated using X-ray diffraction, neutron diffraction, and magnetization measurements. The results show that both crystallize in the cubic Fd3̄m structure at room temperature, and exhibit antiferromagnetic ordering at low temperatures of 49 K and 35 K, respectively, with long-range helical spin arrangements confirmed by neutron diffraction. Additionally, structural phase transitions from cubic Fd3̄m to orthorhombic Fddd occur at approximately 55 K and 85 K for the two systems, respectively. Despite significant chemical disorder at the A-site, these phase transition behaviors are similar to those in low-entropy spinel systems, indicating that high configurational entropy can promote overall structural stability under local chemical disorder, thereby preserving the long-range order and characteristic symmetry-breaking transitions of the parent spinel.\n5. Layer-dependent Landé $g$-factors of electrons, holes, and excitons in two-dimensional Ruddlesden-Popper lead halide perovskites Relevance Score: 3.6354 Authors: Nataliia E. Kopteva, Dmitri R. Yakovlev, Mikhail O. Nestoklon, Carolin Harkort, Evgeny A. Zhukov, Dennis Kudlacik, Erik Kirstein, Scott A. Crooker, Oleh Hordiichuk, Ole F. Dressler, Maksym V. Kovalenko, Manfred Bayer Link: http://arxiv.org/abs/2605.15807v1 Summary: By utilizing spin-flip Raman scattering and time-resolved Kerr rotation magneto-optical techniques, the Zeeman splitting of electrons and holes in (PEA)₂MAₙ₋₁PbₙI₃ₙ₊₁ (n=1 to 8) two-dimensional Ruddlesden-Popper lead halide perovskites was measured. Combined with the exciton Zeeman splitting in reflectivity under pulsed magnetic fields up to 55 T, the evolution of the Landé g-factor with inorganic layer thickness was systematically investigated. The experiments revealed that both electron and hole g-factors exhibit a significant layer-number dependence: the electron g-factor decreases with decreasing layer number (increasing effective band gap), while the hole g-factor monotonically increases. This trend deviates from the universal relationship between the g-factor and band gap energy in bulk materials but aligns with the quantum confinement behavior observed in perovskite nanocrystals. The anisotropy of the g-factors was also quantified through different magnetic field orientations. The experimental results are in qualitative agreement with empirical tight-binding calculations. This study elucidates the modulation of spin energy level structures by quantum confinement in two-dimensional lead halide perovskites, providing a tunable platform for engineering spin-related phenomena in quantum-confined semiconductors.\n6. Thermodynamic signatures of a field-induced ordered intermediate phase in Na$_2$Co$_2$TeO$_6$ Relevance Score: 3.5720 Authors: Prashanta K. Mukarjee, Sebastian Erdmann, R. Kalaivanan, R. Sankar, Kwang-Yong Choi, Alexander A. Tsirlin, Philipp Gegenwart Link: http://arxiv.org/abs/2605.15829v1 Summary: Through high-field thermodynamic studies of Na₂Co₂TeO₆ single crystals down to 1 K, the phase diagram was constructed using magnetization, specific heat, and magnetocaloric effect measurements. A weak residual magnetic moment was observed at zero field, and three field-induced phase transitions with critical fields of approximately 6 T, 7.8 T, and 10.4 T were identified under in-plane magnetic fields (B ∥ a*). The magnetic Grüneisen parameter and specific heat indicate that these continuous phase transitions enclose two intermediate phases. Contrary to the expectation of a field-induced quantum spin liquid, the phase between 7.8 T and 10.4 T does not exhibit enhanced magnetic entropy but instead shows characteristics of an ordered state. No additional anomalies appear above 10.4 T, suggesting a crossover to a conventional spin-polarized state. These results impose strict thermodynamic constraints on the quantum spin liquid hypothesis in Na₂Co₂TeO₆, and further microscopic studies are required to clarify the nature of the field-induced phases.\n7. Reversible nanoscale patterning of WTe$_2$ with a scanning tunneling microscope Relevance Score: 3.5603 Authors: Kevin Hauser, Danyang Liu, Berk Zengin, Jens Oppliger, Samuel Mañas-Valero, Catherine Witteveen, Fabian O. von Rohr, Jennifer E. Hoffman, Fabian D. Natterer Link: http://arxiv.org/abs/2605.15387v1 Summary: This study demonstrates the reversible writing and erasing of nanoscale patterns on the surface of WTe₂ using current pulses applied by a scanning tunneling microscope (STM). Experimental results reveal that these patterns consist of picometer-scale in-plane and out-of-plane atomic displacements accompanied by changes in local density of states. The out-of-plane displacements modulate the intrinsic Peierls distortion in WTe₂, while the in-plane displacements indicate ferroelectric switching behavior. Through spatially resolved lock-in analysis, the displacement amplitudes along crystallographic axes were quantitatively obtained, comparable to the interlayer sliding magnitudes required for ferroelectric flipping and topological phase transitions. Scanning tunneling spectroscopy shows enhancement or suppression of the density of states near the Fermi level and at predicted Weyl point energies within the patterned regions. The patterns can be repositioned and erased, demonstrating the ability to achieve persistent and reversible manipulation of ferroelectric properties in WTe₂ at the nanoscale, providing a new avenue for engineering ferroelectric and topological orders.\n8. Charge-sensitive vibrational modes in BEDT-TTF salts: Signatures of charge ordering and site charge Relevance Score: 3.4359 Authors: Savita Priya, Martin Dressel, Jesse Liebman, Natalia Drichko Link: http://arxiv.org/abs/2605.16012v1 Summary: This paper systematically reviews the application and limitations of C=C stretching vibrational modes in characterizing charge-ordered states and molecular site charges in BEDT-TTF-based organic conductors. By analyzing infrared and Raman spectral data of known BEDT-TTF^+0.5 salts, it is found that the shifts of the ν₂₇(b₁u) and ν₂(a_g) modes with charge transfer in the charge-ordered state are 141 cm⁻¹/e and 98 cm⁻¹/e, respectively, while the distribution range of frequencies among different compounds exceeds 20 cm⁻¹. For compounds with a nominal charge of +0.5, the vibrational peak positions also exhibit a broadening of about 20 cm⁻¹, leading to a considerable uncertainty of approximately ±0.045e in the absolute site charges inferred from the frequency–charge relationship, mainly due to the influence of minor structural differences. Thus, although C=C vibrational modes can effectively identify the presence of charge order and the degree of charge disproportionation, they incur significant errors when used to precisely determine the absolute charge on a molecule, making them more suitable for qualitative or semi-quantitative estimation of charge ordering rather than absolute site charges.\n9. Equidistant resonance jumps in superconducting coplanar resonators driven by Abrikosov vortices Relevance Score: 3.4132 Authors: Dmitrii S. Kalashnikov, Denis Yu. Vodolazov, Ruslan I. Kinzibaev, Andrei G. Shishkin, Vasily S. Stolyarov Link: http://arxiv.org/abs/2605.15751v1 Summary: This study systematically measured the transmission parameter S21 of niobium-based quarter-wavelength coplanar resonators under a vertical magnetic field (up to 40 Oe) and at low temperatures (18 mK to 5 K) using high-resolution magneto-spectroscopy. Beyond the reversible Meissner region, the entire resonance peak exhibited steep step-like jumps as the magnetic field varied; upon reversing the magnetic field sweep direction, these jumps formed nearly equidistant sequences with a spacing of 1.7–1.8 Oe. Combined with theoretical estimates, these equidistant jumps are interpreted as a direct signature of successive entry and exit of multiple Abrikosov vortices into and out of the superconducting thin film. Additionally, the resonance frequency and internal quality factor showed a non-proportional response, indicating a complex contribution of vortex and antivortex configurations to the device performance. The study suggests that these results will stimulate further theoretical and experimental investigations into the discrete nature of large-scale vortex-antivortex systems.\n10. Tunable Crossed Andreev Reflection in Bipolar Magnetic Semiconductors Relevance Score: 3.4032 Authors: Polireddi Naveen, Abhiram Soori Link: http://arxiv.org/abs/2605.15939v1 Summary: By combining a bipolar magnetic semiconductor (BMS) with a superconductor, a purely electrical method for controlling crossed Andreev reflection (CAR) is proposed. Utilizing the opposite spin polarizations of the conduction and valence bands in the BMS, the chemical potentials on both sides are independently tuned so that the carrier spins at the Fermi level are opposite, thereby completely suppressing local Andreev reflection and elastic tunneling, and making CAR dominate the transport. Calculations show that under this pure CAR dominance, the nonlocal conductance is negative and equal in absolute value to the local conductance; the CAR probability exhibits an exponentially decaying oscillatory behavior with the length of the superconducting region, originating from Fabry–Pérot-type interference of Bogoliubov–de Gennes quasiparticles. This method requires no external magnetic field, eliminating stray field disturbances in conventional ferromagnetic systems, and provides a simple and efficient electrostatic control pathway for scalable superconducting spintronic devices.\n11. Transport signatures of valley polarization in graphene multilayers: In-plane linear magnetoconductivity vs anomalous Hall effect Relevance Score: 3.3475 Authors: Fernando Peñaranda, Fernando de Juan Link: http://arxiv.org/abs/2605.16061v1 Summary: In two-dimensional materials, valley polarization accompanied by time-reversal symmetry breaking can form orbital magnets, traditionally probed via the anomalous Hall effect (AHE). This paper proposes that in-plane linear magnetoconductivity (LMC) serves as an alternative transport probe of valley polarization, remaining observable even when the AHE vanishes. Through symmetry analysis, multilayer graphene heterostructures are classified into three types: those with neither LMC nor AHE, those exhibiting only in-plane LMC, and those showing both. Focusing on two representative systems—twisted bilayer graphene (TBG) and rhombohedral graphene (RG)—we find that in TBG, in-plane LMC is finite, but the AHE requires additional substrate-induced symmetry breaking to emerge; in RG, both LMC and AHE correspond to valley polarization, but only occur in the quarter-metal state. Using self-consistent Hartree-Fock and semiclassical transport calculations, we predict in detail the LMC behavior of both systems and analyze implications of recent experiments. The study reveals that in-plane LMC originates from the in-plane orbital moment and Berry curvature induced by interlayer tunneling, dominating the spin response, thus providing an alternative and robust experimental means to detect valley polarization.\n12. Unveiling Magnetic Frustration via the Elastocaloric Effect Relevance Score: 3.3035 Authors: Eric C. Andrade, Pedro M. Cônsoli, Matthias Vojta Link: http://arxiv.org/abs/2605.15274v1 Summary: This study explores the ability of the elastocaloric effect to detect magnetic frustration by calculating the elastic Grüneisen ratio η for the Ising and Heisenberg models on an anisotropic triangular lattice, as well as for the Ising model on a kagome lattice. Methodologically, the entropy as a function of temperature and strain is obtained through analytical solutions and exact diagonalization, from which η is derived. The key findings are as follows: for the Ising model, near the point of maximum frustration (the isotropic point), η can increase exponentially at low temperatures, a universal signature of classical spin liquids with extensive ground-state entropy; in contrast, for the spin-1/2 Heisenberg model, although a similar entropy maximum appears at intermediate temperatures, at low temperatures η is dominated by quantum phase transitions away from the isotropic point rather than by classical frustration effects. The conclusion indicates that η can effectively reflect frustration-induced entropy accumulation, but it cannot directly infer thermal phase transitions at low temperatures, necessitating a distinction between classical and quantum origins. These results provide a theoretical framework for strain-tuning experiments on materials such as triangular lattice organic magnets.\n13. Non-Relativistic Spin-Orbit Interaction in Triplet Superconductors: Edelstein Effect and Spin Pumping by Electric Fields Relevance Score: 3.2857 Authors: Ping Li, G. A. Bobkov, I. V. Bobkova, Tao Yu Link: http://arxiv.org/abs/2605.15610v1 Summary: This study reveals a nonrelativistic spin-orbit coupling effect induced by the triplet order parameter itself in triplet superconductors: the triplet order parameter endows Bogoliubov quasiparticles with a wave-vector-dependent spin structure, thereby entangling spin with orbital motion. Even in the complete absence of relativistic spin-orbit coupling, an electric field can generate spin polarization in p-wave superconductors through this mechanism, realizing the Edelstein effect. Based on this, the authors propose an efficient scheme for generating direct spin currents via near-electric-field nonlinearity, driving spin pumping through the coupling of alternating spin polarization and electron velocity. Calculations using the LaAlO₃/KTaO₃ interface as an example show that the spin current generated by this mechanism is comparable to the spin Hall current in systems with high spin Hall conductivity, and the efficiency is high. This work provides a new avenue for generating and manipulating spin currents in unconventional superconductors and may serve as an all-electrical spin transport fingerprint of triplet pairing symmetry.\n14. Local distortions as a source of piezoelectric/stiffness decoupling in B-doped AlScN Relevance Score: 3.2745 Authors: Laszlo Wolf, Geoff L. Brennecka, Vladan Stevanović Link: http://arxiv.org/abs/2605.15568v1 Summary: This study employs first-principles calculations based on density functional theory-relaxed 100-atom special quasirandom structures to systematically analyze the correlation between local structural distortions and macroscopic properties of pseudo-ternary wurtzite-phase (Al,Sc,B)N alloys over a wide composition range. Using pair distribution function analysis, it is found that boron atoms spontaneously shift from tetrahedral cation sites upon doping, forming a threefold-coordinated planar configuration preferentially oriented along the c-axis, and this process is revealed to be activated by scandium atoms. By defining an atom-specific axial asymmetry ratio (AAR) to quantify the coordination symmetry of each cation along the c-axis, the results indicate that the introduction of boron progressively symmetrizes the local environment of scandium. Further correlating AAR with Born effective charges confirms that this symmetrization is the microscopic mechanism enhancing the piezoelectric response (e33), while maintaining relative stiffness (C33), thereby achieving a decoupling of piezoelectricity and stiffness. This finding elucidates why boron co-doping can break the conventional negative correlation between piezoelectricity and stiffness in AlScN, providing a structural-level theoretical basis for designing nitride thin films with both high stiffness and high piezoelectric response.\n15. Chemical Origins of Non-Bonded Interactions Within and Between Solids Relevance Score: 3.2718 Authors: Paul J. Robinson, Adam Rettig, Hieu Q. Dinh, Anton Z. Ni, Joonho Lee Link: http://arxiv.org/abs/2605.15381v1 Summary: This study extends the absolutely localized molecular orbital energy decomposition analysis (ALMO-EDA) to periodic systems, enabling quantitative dissection of non-covalent interactions within and between solids at the density functional theory level. For three types of materials—molecular crystals, twisted bilayer heterostructures, and layered perovskite heterostructures—the method decomposes lattice formation energies, interlayer binding energies, and band structure variations into three chemically intuitive contributions: frozen interactions, polarization, and charge transfer. The analysis reveals that in pharmaceutical crystals, dispersion forces dominate the stability differences among aspirin polymorphs; in MoS₂/WSe₂ moiré heterostructures, local stacking patterns modulate interlayer band gaps and excitonic properties by altering polarization and charge transfer; and in layered perovskite heterostructures, substitution of alkali metal cations (Li⁺ vs. Na⁺) shifts the quantum well type from type I to type II by changing the relative contributions of frozen, polarization, and charge transfer terms. This framework establishes a chemically transparent connection between macroscopic properties of solids and microscopic interaction mechanisms, offering a systematic tool for understanding and designing complex materials.\n16. Benchmarking empirical and machine-learned interatomic potentials using phase diagram predictions for Lead Relevance Score: 3.2709 Authors: Tom Hellyar, Pascal T. Salzbrenner, Peter I. C. Cooke, Chris J. Pickard, Scott Habershon, Livia B. Pártay Link: http://arxiv.org/abs/2605.16018v1 Summary: This study employs nested sampling and replica exchange nested sampling methods to systematically compare three interatomic potential models for lead—the embedded atom model (EAM), modified embedded atom model (MEAM), and a neural network-based ephemeral data-derived potential (EDDP)—in predicting phase behavior up to 60 GPa. The results indicate that both the EAM and MEAM models predict the face-centered cubic (FCC) phase to remain stable below 60 GPa, whereas the EDDP model successfully captures the experimentally observed FCC-to-hexagonal close-packed (HCP) phase transition at approximately 15 GPa. This contrast highlights the critical roles of training data diversity and model flexibility in accurately describing high-pressure phase behavior. Additionally, the nested sampling method provides a robust framework for unbiased exploration of phase space, and combining machine learning potentials with near-ab-initio accuracy and nested sampling holds promise for truly predictive material phase diagram studies. In particular, the EDDP trained on non-equilibrium configurations demonstrates good transferability, making it suitable for discovering unknown phases.\n17. p-Wave Orbital Angular Momentum Texture in a Chiral Crystal Relevance Score: 3.2632 Authors: Dongjin Oh, Chiara Pacella, Xiangyu Luo, Chris Jozwiak, Aaron Bostwick, Eli Rotenberg, Mats Leandersson, Craig Polley, Angel Rubio, Domenico Di Sante, Riccardo Comin Link: http://arxiv.org/abs/2605.15544v1 Summary: Using circular dichroism angle-resolved photoelectron spectroscopy (CD-ARPES) to study the one-dimensional chiral crystal (TaSe₄)₂I, experiments reveal the existence of an orbital angular momentum (OAM) texture with p-wave symmetry in momentum space, accompanied by an OAM dipole structure. The polarity of this OAM texture reverses with the inversion of crystal chirality, indicating its tight coupling to and controllability by lattice chirality. Combining spin-resolved ARPES measurements with first-principles calculations, it is found that OAM polarization dominates over spin angular momentum (SAM) polarization in the low-energy electronic structure. This work experimentally confirms, for the first time, the presence of a p-wave OAM texture in a crystalline material, providing an ideal platform for the development of spinless orbitronics and laying the foundation for realizing the OAM counterparts of multipolar spin textures found in unconventional magnets (multipole OAM textures).\n18. Itinerant antiferromagnetism in the antagonistic pair compound Y$_4$Co$_3$Ag Relevance Score: 3.1999 Authors: Rafaela F. S. Penacchio, Nao Furukawa, Joanna M. Blawat, John Singleton, Zhouqi Li, Raquel A. Ribeiro, Sérgio L. Morelhão, Sergey L. Bud\u0026rsquo;ko, Paul C. Canfield, Tyler J. Slade Link: http://arxiv.org/abs/2605.15495v1 Summary: Using the concept of antagonistic pairs, the ternary compound Y₄Co₃Ag was successfully synthesized in the immiscible Co-Ag system by adding Y. This compound adopts a monoclinic I2/m structure, with channels formed by Y atoms that host one-dimensional zigzag and hexagonal Co chains extending along the b-axis, and there are no nearest-neighbor contacts between Co and Ag atoms. Transport, magnetic susceptibility, and specific heat measurements indicate that Y₄Co₃Ag undergoes antiferromagnetic ordering at TN = 14.9 K, with an effective magnetic moment of 1.4 μB/Co. However, the specific heat shows an entropy loss associated with magnetic ordering of only about 0.1 R ln2, and magnetization isotherms measured under both DC fields (1.8 K, 70 kOe) and pulsed fields (500 mK, 600 kOe) indicate that the ordered magnetic moment is less than 0.2 μB/Co. These results collectively suggest the presence of small itinerant magnetic moments and strong magnetic fluctuations in Y₄Co₃Ag, making it a candidate material for studying itinerant magnetic interactions in quasi-one-dimensional systems.\n19. Near-degenerate competing magnetic orders in EuAgAs: a tunable route to altermagnetism Relevance Score: 3.1662 Authors: Mohamed El Gazzah, Daniel Kaplan, Zachary Morgan, Abhijeet Nayak Resham Regmi, Sk Jamaluddin, Huibo Cao, Igor I. Mazin, Nirmal J. Ghimire Link: http://arxiv.org/abs/2605.16242v1 Summary: Neutron diffraction experiments reveal that the ground-state magnetic structure of EuAgAs is an in-plane ↑↑↓↓ antiferromagnetic order with propagation vector 𝐪=(0,0,1/2), rather than the altermagnetic order previously predicted by density functional theory. However, systematic first-principles calculations show that the ferromagnetic and altermagnetic states are only 0.11 and 0.40 meV per formula unit higher in energy than this antiferromagnetic ground state, respectively, indicating significant near degeneracy. Further theoretical analysis indicates that a model including only Heisenberg exchange interactions would predict a spin-spiral ground state, whereas the introduction of non-Heisenberg biquadratic coupling is necessary to stabilize the collinear antiferromagnetic phase observed experimentally. This near degeneracy renders the magnetic order of EuAgAs highly tunable: DFT predicts that under hydrostatic pressure of approximately 14 GPa, the system undergoes a transition from the antiferromagnetic phase to the altermagnetic phase. This work establishes EuAgAs as a controllable material platform for realizing topological altermagnetic order via external tuning parameters such as pressure, providing both experimental and theoretical foundations for exploring the synergistic effects of altermagnetism and band topology.\n20. Rapid Atmospheric Vapor Deposition of H:In2O3 Transparent Conducting Oxide Thin Films Relevance Score: 3.1504 Authors: Xiaoyu Guo, Hae-Jun Seok, Eilidh L. Quinn, Matthew K Sharpe, Callum. D. McAleese, Yi-Teng Huang, Xinjuan Li, Kexue Li, Chia-Yu Chang, Yongjie Wang, John O\u0026rsquo;Sullivan, Katie L. Moore, Caterina Ducati, Ruy Sebastian Bonilla, Han-Ki Kim, Abderrahime Sekkat, Robert L. Z. Hoye Affiliations: Sungkyunkwan University, University of Toulouse, University of Manchester, University of Oxford, National Taiwan University, University of Surrey, University of Cambridge Link: http://arxiv.org/abs/2605.16166v1 Summary: This study employs atmospheric pressure chemical vapor deposition (AP-CVD) to rapidly fabricate hydrogen-doped indium oxide (H:In₂O₃) transparent conductive oxide thin films at a mild temperature of 140 °C under ambient pressure, achieving a growth rate approximately 40 times higher than that of atomic layer deposition (ALD). By systematically comparing the effects of different oxidants (O₂/H₂O, N₂/H₂O, O₂, and O₂/N₂), it is found that using water vapor as the oxidant introduces hydrogen dopants from water, which effectively passivate oxygen vacancies that serve as carrier scattering centers, significantly increasing the Hall mobility from 40 ± 10 cm²/Vs to 160 ± 30 cm²/Vs. The resulting films exhibit a low sheet resistance of 7.20 ± 0.01 Ω/□ (resistivity of 0.50 ± 0.06 mΩ·cm) and a near-infrared transmittance as high as 89%, outperforming commercial sputtered indium tin oxide. This work establishes a fast, scalable, and cost-effective method for TCO fabrication, with mild growth conditions compatible with heat-sensitive materials, offering a new pathway for preparing high-performance transparent electrodes in optoelectronic devices.\n","permalink":"https://nickelates.uk/en/posts/2026-05-19-arxiv-daily/","summary":"\u003cblockquote\u003e\n\u003cp\u003e\u003cstrong\u003eDaily Overview\u003c/strong\u003e:\nDear readers, today\u0026rsquo;s rapid overview of the nickel-based superconductivity field presents a core research advance: using ultralow-temperature scanning tunneling microscopy/spectroscopy, researchers have for the first time observed an energy-symmetric flat-bottomed U-shaped superconducting gap in (La,Pr)₃Ni₂O₇ thin films, confirming its nodeless gap nature. This gap exhibits zero density of states at extremely low temperatures, evolves into a V-shape as temperature increases, and is suppressed by magnetic fields, behaving consistently with conventional superconducting gaps. This discovery reveals a new mechanism for high-temperature superconductivity in double-layer nickelates, offering insightful clues for achieving even higher-temperature superconductivity under ambient or zero pressure. Apart from this closely related paper, the remaining articles do not involve nickel-based superconductivity.\u003c/p\u003e","title":"arXiv Daily: nickelate superconductors 2026-05-19"},{"content":" Daily Overview: Today\u0026rsquo;s research in the field of nickelate superconductivity is characterized by a robust trend of experimental deepening and theoretical unification. On the experimental front, a study combining atomic-resolution scanning tunneling microscopy with spectroscopy has, for the first time, directly observed a nodeless U-shaped superconducting gap in (La,Pr)₃Ni₂O₇ superconducting thin films. It also reveals that precise control of oxygen content is an essential prerequisite for obtaining intrinsic spectra, providing key evidence for understanding the pairing symmetry of superconductivity. At the theoretical level, an important paper proposes a unified framework of \u0026ldquo;shear-stress-constrained superconductivity,\u0026rdquo; insightfully pointing out that non-hydrostatic pressure or epitaxial strain themselves are not the direct cause of superconductivity; rather, the key lies in the local Ni-O framework constraint deformation achieved through shear stress. This scenario offers a cross-scale unified quantitative perspective for understanding the fragility, heterogeneity, and reproducibility challenges of superconducting behavior in both high-pressure bulk and thin-film systems. Additionally, this week\u0026rsquo;s submissions also include several studies on strongly correlated electron systems closely related to superconductivity, such as a dynamical scaling analysis of the pseudogap-to-Fermi-liquid quantum critical point in the two-dimensional Hubbard model, and an ultrafast spectroscopy study of the rapid decoupling between quasiparticles and spin fluctuations in superconducting cuprates. These works, in mutual reflection with core issues in the nickelate field, collectively advance the understanding of unconventional superconductivity and strongly correlated electronic states.\n1. Atomically resolved intrinsic superconducting gap in (La,Pr)3Ni2O7 films Relevance Score: 5.9068 Authors: Xinxin Wang, Yaqi Chen, Cui Ding, Lizhi Xu, Jian-Jian Miao, Guangdi Zhou, Zhuoyu Chen, Yu-Jie Sun, Jin-Feng Jia, Qi-Kun Xue Affiliations: Southern University of Science and Technology, Quantum Science Center of Guangdong-Hong Kong-Macao Greater Bay Area, Tsinghua University, Shanghai Jiao Tong University Link: http://arxiv.org/abs/2605.14806v1 Summary: This study employs atomic-resolution scanning tunneling microscopy and spectroscopy to characterize the superconducting thin film of (La,Pr)₃Ni₂O₇ with 1.5 unit-cell thickness grown on SrLaAlO₄. By maintaining a well-ordered √2×√2 surface reconstruction through low-temperature ultrahigh vacuum sample transfer, highly reproducible U-shaped tunneling spectra were obtained in rapidly transferred samples, exhibiting two superconducting gap magnitudes (approximately 14 meV and 20 meV) and an extended zero-conductance plateau, indicating a nodeless superconducting gap in the system. In contrast, samples exposed to a relatively higher vacuum environment for an extended period without cooling during transfer, despite retaining surface reconstruction and a superconducting onset transition temperature above 40 K, displayed V-shaped spectra. Broad-energy-range spectra further revealed that oxygen loss introduces spectral weight associated with density waves. By comparing spectral variations under different transfer durations, this study demonstrates that oxygen content control is a prerequisite for obtaining the intrinsic superconducting gap. It provides direct atomic-scale observation of a nodeless superconducting gap in bilayer nickelate thin films, offering crucial experimental evidence for understanding the pairing symmetry of superconductivity in this system.\n2. Shear-stress-constrained superconductivity in Ruddlesden-Popper nickelates Relevance Score: 5.5793 Authors: Liling Sun, Shu Cai, Jinyu Zhao, Qi Wu, Yang Ding, Tao Xiang, Ho-kwang Mao Affiliations: Shanghai Advanced Research in Physical Sciences, Chinese Academy of Sciences, Center for High Pressure Science \u0026amp; Technology Advanced Research Link: http://arxiv.org/abs/2605.14265v1 Summary: This paper proposes the \u0026ldquo;Shear Stress-Confined Superconductivity\u0026rdquo; (SSCS) scenario to provide a unified understanding of the superconducting behavior in Ruddlesden-Popper (RP) nickelates under high-pressure bulk and epitaxial thin-film conditions. The core idea is that the metastable RP lattice enters a superconducting state only when the local constrained deformation of the Ni-O framework falls within a finite shear strain window. This deformation controls the rotation of NiO₆ octahedra, the interlayer Ni-O-Ni bond angle, and the hybridization between Ni dz² and dx²-y² orbitals. The SSCS scenario consistently explains a range of experimental phenomena, including the pressure threshold (~14 GPa) in bulk materials, the reversibility of superconductivity, spatial inhomogeneity and filamentary superconducting features, sensitivity to the pressure medium, the dependence of superconductivity in thin films on substrate quality, and poor reproducibility across different samples. The paper emphasizes that hydrostatic pressure or epitaxial strain alone is not the direct cause of superconductivity; rather, the key lies in the local structural confinement state achieved through shear stress. In bulk materials, intrinsic shear stress generated by non-hydrostatic pressure drives the structure into a favorable configuration; in thin films, the biaxial strain provided by the substrate already supplies this confinement, so additional pressure can further enhance Tc. The SSCS scenario also explains how chemical doping, mixed RP phases, and optimized pressure media enhance superconductivity by modulating the shear stress distribution. This framework underscores that the fragility and heterogeneity of nickelate superconductors are not extrinsic disturbances but intrinsic features of the superconducting state itself. Future directions for improving reproducibility include controlling the average local confinement and its spatial distribution width in samples, and employing local probes such as nitrogen-vacancy centers to correlate stress, stoichiometry, and superconducting response. In summary, SSCS provides a unified quantitative framework for understanding RP nickelate superconductivity across bulk materials and thin films.\n3. Transient superionic state in ultrafast-irradiated post-transition metal oxides Relevance Score: 4.2563 Authors: N. Medvedev, N. Nikishev, A. Artímez Peña Link: http://arxiv.org/abs/2605.14827v1 Summary: This study employs the multi-scale simulation code XTANT-3 to systematically analyze the conditions and mechanisms for generating transient superionic states in 12 post-transition metal oxides under ultrafast laser irradiation. Methodologically, the code integrates Monte Carlo methods to simulate light absorption and high-energy electron transport, Boltzmann equations to describe low-energy electron dynamics, a density-functional tight-binding method to compute electronic energy levels and interatomic potentials, and molecular dynamics to track atomic motion, thereby coupling electronic excitation with atomic response. The findings reveal that different oxides exhibit distinct pathways to superionic states: those with sparse metal sublattices (e.g., corundum-structured Al₂O₃, α-Ga₂O₃, Tl₂O₃, and Pb₂O₃) can form superionic states via nonthermal phase transitions (where electronic excitation directly alters atomic potentials) on sub-picosecond timescales. In contrast, In₂O₃, PbO, and β-Ga₂O₃ form superionic states via thermal processes (electron-phonon coupling heating the atoms) over longer timescales (picoseconds), manifesting as intermediate states prior to melting. Conversely, ZnO and CdO, due to their dense metal sublattices (zincblende structure), undergo only nonthermal melting, while Tl₂O undergoes only thermal melting, none exhibiting superionicity. SnO, Bi₂O₃, and BiO₂ display states that are difficult to classify definitively: oxygen sublattice diffusion is significantly faster than that of the metal sublattice, yet the latter is not fully solid, which can be regarded as a \u0026ldquo;superionic liquid.\u0026rdquo; The study indicates that the sparsity of the metal sublattice is an important correlating factor for the formation of nonthermal superionic states (e.g., corundum structures tend to yield this state), but it is neither a sufficient nor necessary condition. Additionally, the paper provides the damage threshold doses and corresponding fluences for each material, offering reference for experiments.\n4. Quantum criticality in the two-dimensional Hubbard model Relevance Score: 3.9708 Authors: Mathias Pelz, Gabriel Kotliar, Jan von Delft, Andreas Gleis Link: http://arxiv.org/abs/2605.15059v1 Summary: This paper employs the dynamical cluster approximation (DCA) combined with the numerical renormalization group (NRG) as a cluster solver to directly obtain real-frequency dynamical information near zero temperature. It systematically investigates the doping-driven normal-state phase diagram of the square-lattice Hubbard model in the cuprate-related parameter regime (U = 7t, t\u0026rsquo; = -0.3t). The main findings are as follows: There exists a critical doping p*, which marks a continuous quantum phase transition between a pseudogap metal and a normal Fermi liquid. This transition is identified by the continuously collapsing Fermi liquid scaling extracted from the charge, spin, and d_{x^2-y^2}-wave pairing susceptibilities. The collapse gives rise to non-Fermi liquid behavior at intermediate energy scales, and at p*, this behavior appears to extend down to arbitrarily low energies. As the doping crosses p* from the normal Fermi liquid (p \u0026gt; p*) into the pseudogap metal (p \u0026lt; p*), the low-energy coherent spectral weight in the antinodal region vanishes and is replaced by a narrow metallic pseudogap, while the nodal region evolves smoothly and remains relatively coherent. This results in a Fermi arc in the pseudogap metal, characterized by large zero-frequency spectral weight in the nodal region and strong suppression in the antinodal region. Additionally, two crossover lines, pL and p**, are identified at lower dopings, corresponding respectively to changes in the filling degree of the antinodal pseudogap and the crossing of the self-energy pole through the Fermi level. These are not quantum phase transitions but smooth crossovers within the pseudogap metal. The study confirms that this quantum critical behavior is robust within the parameter range.\n5. Ultrafast decoupling of quasiparticles and spin fluctuations in superconducting cuprates Relevance Score: 3.8692 Authors: Yuto Taniguchi, Ryo Kato, Tatsuya Amano, Hirotake Itoh, Yohei Kawakam, Yuto Nakamura, Hideo Kishida, Christian Bernhard, Jure Demsar, Takahiko Sasaki, Terukazu Nishizaki, Kenji Yonemitsu, Shinichiro Iwai Affiliations: Nagoya University, Chuo University, Kyushu Sangyo University, Johannes Gutenberg University Mainz, Tohoku University, University of Fribourg Link: http://arxiv.org/abs/2605.14238v1 Summary: By employing broadband (0.16–4.1 eV, ~100 fs) and near-single-cycle (6 fs) transient reflectivity spectroscopy, this study investigates the generation dynamics of photoexcited quasiparticles in the superconducting state of optimally doped YBa₂Cu₃O₆.₉₄ (T_c = 92 K). The experiments reveal that within the first few femtoseconds after photoexcitation, enhanced electron-electron Umklapp scattering dominates the transient response, indicating an eV-scale transient modulation of long-range Coulomb interactions. Subsequently, a rapid suppression of the absorption scattering rate associated with spin-fluctuation-modified carriers is observed in the mid-infrared region (0.1–1 eV), occurring on a time scale of approximately 90 femtoseconds, which is consistent with the inverse of the optical gap. The authors attribute this phenomenon to the ultrafast decoupling of quasiparticles from the spin fluctuation background. Additionally, photoinduced Hartree shifts of the Zhang–Rice singlet band and the charge-transfer band are detected. By comparing the transient reflectivity spectra of the superconducting and normal states (295 K) in conjunction with equilibrium optical data, this work reveals the correlated many-body dynamics involved in quasiparticle generation, providing new insights into the unconventional pairing mechanism of cuprate high-temperature superconductors.\n6. Biquadratic exchange coupling effect on the magnetic properties of (Fe/Ti) multilayers Relevance Score: 3.6489 Authors: Melissa Yactayo, H. S. Tarazona, O. Copie, J. -C. Rojas-Sánchez, J. Quispe-Marcatoma, C. V. Landauro Affiliations: Université de Lorraine, Universidad Nacional Mayor de San Marcos Link: http://arxiv.org/abs/2605.14545v1 Summary: This study investigates the static and dynamic magnetic properties of weakly antiferromagnetically coupled Fe/Ti superlattices, with a focus on elucidating the correlation between magnetic behavior and structural characteristics. Alternating Fe and Ti layers, along with interfacial roughness—particularly in the upper layers—were confirmed via high-resolution transmission electron microscopy and X-ray diffraction. Magnetic measurements revealed two-step hysteresis loops as well as temperature- and thickness-dependent interlayer exchange coupling (IEC). A macro-spin model incorporating both bilinear and biquadratic exchange coupling successfully reproduced the experimental data, and phase diagram analysis enabled the identification of non-collinear magnetic configurations. The results underscore the influence of structural defects on magnetic properties and highlight the critical role of biquadratic exchange coupling in Fe/Ti/Fe multilayers.\n7. The thermopower properties of interacting systems Relevance Score: 3.5553 Authors: M. A. Habitzreuter, Willdauany C. de Freitas da Silva, Rodrigo A. Fontenele, Natanael C. Costa, Thereza Paiva Link: http://arxiv.org/abs/2605.14225v1 Summary: This study systematically investigates the effects of various interactions beyond the on-site Hubbard interaction on the Seebeck coefficient, employing methods such as quantum Monte Carlo simulation, exact diagonalization, and cluster approximation. Specifically, cases including attractive interaction, nearest-neighbor interaction, sublattice potential, and electron-phonon coupling are considered. The results indicate that additional interaction scales can enhance the Seebeck coefficient and induce multiple anomalous sign changes during doping. This anomalous behavior is closely related to the opening of a ground-state gap. Furthermore, even in the absence of on-site repulsion, electron-phonon coupling can also trigger Seebeck anomalies. The study further links the sign changes of the Seebeck coefficient to the reconstruction and topological modification of the Fermi surface, an effect commonly observed in cuprate superconductors. By comparing the attractive and repulsive Hubbard models, it is found that the attractive model, due to its renormalization into a hard-core boson gas, exhibits a weaker dependence of the Seebeck coefficient on interaction at high temperatures. When nearest-neighbor interaction or electron-phonon coupling is included, changes in the system\u0026rsquo;s gap and Fermi surface topology significantly affect the thermoelectric response. This work provides new insights into understanding anomalous thermoelectric phenomena in strongly correlated systems and points toward directions for designing efficient thermoelectric materials.\n8. Revealing Hidden Correlations in a Fermi-Hubbard system via Interaction Ramps Relevance Score: 3.4701 Authors: Botond Oreg, Carter Turnbaugh, Jens Hertkorn, Ningyuan Jia, Martin Zwierlein Link: http://arxiv.org/abs/2605.14909v1 Summary: By rapidly enhancing the interaction strength (interaction quench), we observed a significant enhancement in the visibility of charge density wave (CDW) correlations in an attractive Hubbard model realized with cold atoms. This technique utilizes a Feshbach resonance to rapidly ramp the interaction from an initial value to the resonance point before imaging, causing initially nonlocal pairs (whose size is comparable to the interparticle spacing) to shrink into local doublons, thereby revealing hidden spatial order. The experiment was implemented in a two-dimensional optical lattice with single-atom-resolved imaging, measuring the density correlation function and structure factor at various interaction strengths. The results show that in the strongly correlated crossover regime (where the interaction strength is comparable to the bandwidth), the CDW signal enhancement after the quench is maximized, with the peak occurring in the region where the superfluid critical temperature is highest, demonstrating that CDW order due to nonlocal pairing originally existed but was masked. By analyzing the single-occupancy fraction and spin-charge correlations after the quench, we distinguish between unpaired Fermi liquids and the pseudogap phase with preformed pairs: in the crossover regime, nonlocal pairing dominates, and the quench transforms spin-dependent correlations into spin-independent correlations, reflecting inter-pair repulsion. This technique provides a new approach to studying exotic pairing in spin-imbalanced systems (such as the FFLO state) and stripe order in the doped repulsive Hubbard model, while also serving as a local thermometer, as the single-occupancy fraction after the quench directly probes entropy and temperature.\n9. Unified definition of ferroelectricity Relevance Score: 3.4390 Authors: Wei Luo, Shihan Deng, Hongjun Xiang, Laurent Bellaiche Affiliations: Tel Aviv University, Fudan University, University of Arkansas Link: http://arxiv.org/abs/2605.14328v1 Summary: This paper proposes a unified definition of ferroelectricity based on switchable polarization difference, replacing the traditional criterion that relies on polar space groups and spontaneous polarization. This definition naturally encompasses conventional ferroelectrics and quantum ferroelectrics (including integer and fractional quantum ferroelectrics) and emphasizes that the polarization difference is a physically measurable key quantity. Based on this definition, the authors developed a high-throughput screening workflow: experimentally synthesized materials were selected from the Materials Project database, energy-equivalent initial and final state structures were constructed via symmetry operations, the polarization difference was calculated using a point-charge model, and the switching barrier was evaluated using the solid-state elastic band method (combined with the UMA universal machine learning potential). Ultimately, 100 conventional ferroelectrics and 68 quantum ferroelectrics (with barriers below 400 meV/f.u.) were screened out. Among them, the quantum ferroelectrics include two types: one associated by rotational symmetry operations, and the other by pure translational operations. In particular, the authors discovered a new class of quantum ferroelectrics whose polarization quantization originates from arbitrary ionic displacements (rather than only fractional or integer lattice vector displacements), such as Cs₂PdC₂ and Ag₂I₂. A representative material, Ba₃I₆ (space group P-62m), exhibits integer quantum ferroelectricity: a half lattice vector translation of the Ba-1 atom along the c-axis results in a polarization difference of one polarization quantum (approximately 21.6 μC/cm²), with associated relaxation of iodine atoms. This work unifies conventional and quantum ferroelectrics, expands the range of explorable materials, and provides a practical roadmap for the experimental discovery of a new generation of ferroelectrics with advanced switchable functionalities.\n10. Dynamical scaling near the pseudogap quantum critical point of the two-dimensional Hubbard model Relevance Score: 3.4348 Authors: Mathias Pelz, Gabriel Kotliar, Jan von Delft, Andreas Gleis Link: http://arxiv.org/abs/2605.15060v1 Summary: We used the four-patch dynamical cluster approximation (DCA) combined with the numerical renormalization group (NRG) as a cluster impurity solver to investigate the dynamical scaling near the quantum critical point from a pseudogap metal to a Fermi liquid in the two-dimensional Hubbard model. By calculating the real-frequency dynamical response at different temperatures, we found that near the critical doping, the imaginary part spectra of the local spin and cluster current susceptibilities satisfy the scaling form ( x = \\omega/T ): ( \\chi\u0026rsquo;\u0026rsquo;(\\omega,T) \\sim \\tanh(x/2) ). Meanwhile, the cluster contribution to the optical conductivity exhibits a scaling behavior ( T\\sigma\u0026rsquo;_{\\mathrm{cl}}(\\omega,T) \\sim \\tanh(x/2)/x ), implying that the cluster DC conductivity scales as ( 1/T ). Within the scaling regime, the vertex contribution to the cluster optical response dominates over the bubble contribution, indicating that short-range current relaxation mechanisms are predominant. Additionally, we found evidence of a marginal Fermi liquid self-energy in the nodal region, whose imaginary part shows an approximately linear dependence on frequency and temperature. This self-energy behavior, together with the vertex-dominated ( 1/T ) conductivity, suggests the presence of strange metal optical transport characteristics in the quantum critical regime. Our calculations qualitatively reproduce several experimental observations in the strange metal regime of cuprates, including Planckian scaling of spin fluctuations, linear resistivity over a wide temperature range, and an electronic structure featuring nodal coherent Fermi arcs and antinodal pseudogaps. The results support the existence of a pseudogap quantum critical point and reveal non-Fermi liquid scaling behavior near this critical point.\n11. Strong electron correlations and ligand hybridization for altermagnetism Relevance Score: 3.4226 Authors: Byungkyun Kang, Anderson Janotti, Dai Q. Ho, Myoung-Hwan Kim, Chul Hong Park, Sangkook Choi, Mark R. Pederson, Eunja Kim Link: http://arxiv.org/abs/2605.14248v1 Summary: This study systematically investigates the effects of electronic correlation and ligand hybridization on altermagnetism in three typical altermagnetic candidate materials (MnF₂, MnTe, and RuO₂) using advanced quantum many-body frameworks, including fully self-consistent GW plus extended dynamical mean-field theory (FGW+EDMFT) and DFT+DMFT. For MnF₂, the calculations reveal strong local electronic correlation, with the Mn-3d states exhibiting clear Mott insulator characteristics and a Mott gap of approximately 2 eV in the visible light range arising from nonlocal screening effects. The strong correlation significantly localizes the Mn-3d electrons, narrowing the spin-resolved bandwidth and thereby suppressing spin-band splitting. In contrast, MnTe, which combines strong correlation and pronounced Mn 3d-Te 5p orbital hybridization, demonstrates substantial band spin splitting while maintaining a large local magnetic moment, making it an ideal platform for altermagnetism. RuO₂, despite having almost no local magnetic moment in its antiferromagnetic phase (behaving as a Pauli paramagnet), still exhibits significant spin-band splitting, indicating that it is an itinerant altermagnet. The study reveals that achieving altermagnetism in strongly correlated systems requires both strong local electronic correlation and the selection of appropriate ligands to facilitate orbital hybridization. These findings provide crucial guidance for the rational design and discovery of novel altermagnetic materials.\n12. High-Pressure Crystal Structure Database Relevance Score: 3.4151 Authors: Zhenyu Wang, Qingchang Wang, Junwen Duan, Heng Ge, Xiaoshan Luo, Pengyue Gao, Wei Zhang, Jian Lv, Yanchao Wang, Yanming Ma Affiliations: Jilin University, Zhejiang University Link: http://arxiv.org/abs/2605.14471v1 Summary: This paper presents a comprehensive data platform named the High-Pressure Crystal Structure Database (HPCSD), designed to address the dispersion of high-pressure structural information. The database integrates two complementary data sources: first, elemental high-pressure phases, comprising 467 experimentally and theoretically reported phases, all of which have been re-optimized within a unified density functional theory (DFT) framework, with continuous enthalpy curves systematically generated across their stability ranges; second, stable and metastable phases derived from the CALYPSO crystal structure prediction method, which, after rigorous screening and uniform DFT re-optimization, retain the 50 lowest-energy structures for each composition. The initial version contains 77,346 uniformly evaluated structural entries covering 89 elements. Analysis indicates that pressure-induced polymorphism is widespread and exhibits significant group-dependent trends: s-block, p-block, lanthanide, and actinide elements display rich phase diversity, while most transition metals and noble gases resist structural changes. Structural diversity is strongly influenced by the electronic adaptability of elements, with maximum structural complexity occurring at intermediate rather than the highest pressure ranges. This database provides a standardized and reusable data infrastructure for high-pressure materials research, capable of accelerating experimental phase identification, facilitating cross-study thermodynamic comparisons, and supporting the development of machine learning interatomic potentials and generative models for high-pressure systems.\n13. T-E formulation-based modeling of thin HTS shell magnetization Relevance Score: 3.4014 Authors: Leonid Prigozhin, Vladimir Sokolovsky Affiliations: Ben-Gurion University of the Negev Link: http://arxiv.org/abs/2605.14818v1 Summary: This work extends the T-E hybrid finite element method, originally developed for planar superconducting thin films, to the magnetization modeling of non-planar high-temperature superconducting (HTS) thin shells. The method is based on the T-E formulation, solving simultaneously for the current potential T and the electric field E. The computational domain is confined to the shell itself, eliminating the need to mesh the surrounding space. The thin shell approximation reduces the problem to two dimensions, and the influence of the metal substrate is taken into account. Nonconforming Crouzeix-Raviart elements are employed to approximate the current potential, while piecewise constant vector functions are used for the rotational electric field. The nonlinear system of equations is solved through implicit time discretization and an iterative approach. The accuracy of the method is validated through several axisymmetric test cases, including the magnetization of a spherical shell, with results compared against high-precision spectral method solutions. Subsequently, the method is applied to a realistic model of a cylindrical magnetic dynamic pump to compute the open-circuit voltage generated by rotating permanent magnets. This problem is non-axisymmetric and considers field-dependent critical current density as well as substrate conductivity. The results indicate that the proposed method effectively handles non-planar superconducting shells of complex geometry, yielding accurate current density and electric field distributions, thereby providing a powerful tool for computing AC losses or flux pump voltages.\n14. A DFT+DMFT study of the electronic structure of Samarium Relevance Score: 3.3803 Authors: Shengsong Xu, Zhenfeng Ouyang, Li Huang, Zhong-Yi Lu Link: http://arxiv.org/abs/2605.14638v1 Summary: This study employs density functional theory combined with single-site dynamical mean-field theory (DFT+DMFT) to perform first-principles calculations of the electronic structures of three phases of samarium (Sm) metal under ambient pressure: α, β, and γ phases. The investigation covers key electronic properties such as band structure, density of states, self-energy function, and valence histogram. The computational results indicate that the 4f electrons exhibit highly localized characteristics in all three phases, with the Kondo resonance peak being significantly suppressed and the hybridization between 4f electrons and conduction electrons being very weak. Analysis of the density of states shows that the density of states near the Fermi level mainly originates from conduction electrons, whereas the contribution of 4f electrons is primarily concentrated in the lower Hubbard band around -2.5 eV and the upper Hubbard band at approximately 5 eV. Matsubara analysis of the self-energy function reveals non-Fermi liquid behavior, and the effective mass of 4f electrons is relatively large (e.g., the effective mass for the j=5/2 orbital is approximately 26–48), reflecting the significant influence of strong correlation effects. The valence histogram shows that Sm 4f electrons primarily occupy the 5+ valence state (about 80%), further confirming their localized nature. The calculated density of states is in good agreement with experimental data from ultraviolet photoelectron spectroscopy and inverse photoelectron spectroscopy. This work provides a comprehensive picture of the electronic structure of samarium metal and offers a clear physical description of its strongly correlated f-electron characteristics.\n15. Spin Hall effect in electronic Lévy glasses: Enhanced spin current generation in the superdiffusive regime Relevance Score: 3.2966 Authors: Diego B. Fonseca, Luiz Felipe C. Pereira, Anderson L. R. Barbosa Link: http://arxiv.org/abs/2605.14214v1 Summary: This study investigates the spin Hall effect in electronic Lévy glasses, which are composed of graphene nanoribbons embedded with randomly distributed circular regions exhibiting strong spin-orbit coupling. By tuning the Fermi energy, both superdiffusive and diffusive transport regimes can be realized. Using the Landauer–Büttiker formalism in conjunction with numerically exact tight-binding simulations, the spin-resolved transmission coefficients were computed, enabling a systematic examination of the spin Hall current and spin Hall angle as functions of Fermi energy, spin-orbit coupling strength, and local electrostatic potential. The results demonstrate that in the superdiffusive regime (characterized by low Fermi energy, low resistivity, low magnetoresistance, and long spin diffusion length), a small longitudinal charge current can be efficiently converted into a significantly enhanced transverse spin Hall current, with a spin Hall angle reaching up to 30%. In contrast, in the diffusive regime (high Fermi energy, high resistivity, high magnetoresistance, and short spin diffusion length), the same charge current yields only a modest spin Hall current, corresponding to a spin Hall angle of merely 5%. Furthermore, applying a local electrostatic potential to the spin-orbit coupling clusters further improves the conversion efficiency. These findings indicate that electronic Lévy glasses achieve superdiffusive transport through the engineering of disordered geometries, providing a flexible platform for efficient charge-to-spin conversion. This offers important guidance for optimizing the spin Hall effect and designing next-generation spintronic devices.\n16. Switchable Surface Linear Photogalvanic Effect in the Magnetic Weyl Semimetal Co3Sn2S2 Relevance Score: 3.2671 Authors: Niket Shah, Aymen Nomani, Kai Chen, Hridis Pal, Pavan Hosur Affiliations: Indian Institute of Technology Bombay, University of Houston, Tongji University Link: http://arxiv.org/abs/2605.14107v1 Summary: This paper systematically investigates the linear photogalvanic effect (LPGE) on the surface of the magnetic Weyl semimetal Co3Sn2S2 using Green\u0026rsquo;s function and diagrammatic formalism. The study shows that although the LPGE vanishes in the bulk due to centrosymmetry, it is allowed on the surface where inversion symmetry is broken. Symmetry analysis and numerical calculations reveal that the surface crystal symmetry leads to a characteristic sign reversal of the total photocurrent at specific polarization angles upon magnetization reversal. The intrinsic contribution is strongly constrained by anti-unitary mirror symmetry, resulting in several zero nonlinear response tensor components; in contrast, the extrinsic contribution is not subject to this constraint and exhibits a large amplitude, attributed to the enhanced density of states associated with Fermi arc surface states. Furthermore, the photocurrent displays an approximately linear temperature dependence and a power-law scaling behavior at low frequencies, i.e., |j_y| ∝ ω^{-2.2}, with the scaling exponent showing weak temperature dependence. These results position Co3Sn2S2 as a promising platform for experimental studies of symmetry-controlled nonlinear transport in realistic systems, with potential applications in magneto-optoelectronic devices.\n17. Strain-Enhanced Hydrogen Evolution, Electrical, Optical, and Thermoelectric Properties of the Multifunctional 2D CrSi2N4 Monolayer Relevance Score: 3.2154 Authors: Rao Uzair Ahmad, Fahd Sikandar Khan, Nasir Javed Affiliations: Ghulam Ishaq Khan Institute of Engineering Sciences and Technology, National University of Science and Technology Link: http://arxiv.org/abs/2605.14408v1 Summary: Based on first-principles density functional theory (DFT), this paper systematically investigates the structural, electronic, optical, thermoelectric, and electrocatalytic properties of monolayer CrSi2N4. The material exhibits a symmetric N-Si-N-Cr-N-Si-N seven-layer structure, with dynamic, thermodynamic (at 300 K), and mechanical stability, and a high cohesive energy of -8.76 eV/atom. The PBE and HSE06 functionals reveal indirect band gaps of 0.58 eV and 2.16 eV, respectively, with the band gap primarily contributed by Cr-3d and N-2p states. Optically, the static dielectric constant is 15.57, and the maximum absorption coefficients in the visible and deep ultraviolet regions reach 0.9×10^6 cm⁻¹ and 1.4×10^6 cm⁻¹, respectively. Using semi-classical Boltzmann transport theory, the n-type thermoelectric power factor at room temperature is predicted to be as high as 3.5 mW/mK². For the hydrogen evolution reaction (HER), the hydrogen adsorption free energy (ΔGH) on the basal plane N sites is 1.05 eV; applying a +5% biaxial tensile strain significantly improves HER kinetics, reducing ΔGH to 0.46 eV, a performance enhancement of approximately 58%. Consequently, monolayer CrSi2N4 is a robust and tunable candidate material with potential applications in waste heat recovery, photodetection, and sustainable electrocatalysis.\n18. Carrier-density dependence of magnetotransport in correlated Dirac semimetal CaIrO$_3$ Relevance Score: 3.1943 Authors: Rinsuke Yamada, Jun Fujioka, Minoru Kawamura, Tatsuya Okawa, Yoshio Kaneko, Shiro Sakai, Motoaki Hirayama, Ryotaro Arita, Kiyohiro Adachi, Daisuke Hashizume, Yoshinori Tokura Link: http://arxiv.org/abs/2605.14180v1 Summary: In the low carrier density region (approximately 2.2×10^16 cm⁻³ at 2 K), the mobility of CaIrO₃ exceeds 1.0×10^5 cm²/Vs, and the transverse magnetoresistance reaches 2000% at 12 T. Through analysis of Shubnikov-de Haas oscillations and Hall conductance, it is found that the Fermi velocity is nearly independent of the Fermi surface cross-sectional area (i.e., carrier density), supporting the k-linear dispersion of Dirac nodes. The variation of magnetoresistivity with magnetic field is approximately B-linear in the moderate carrier density region (n_H ≥ 4×10^16 cm⁻³), but exhibits a nonlinear B^α (α \u0026gt; 2) behavior in the lower carrier density region. This change in magnetoresistivity may originate from enhanced long-range Coulomb interactions in the quantum limit, where Dirac electrons are subject to quasi-one-dimensional confinement by the magnetic field. By studying the carrier density dependence of differently doped samples, the origin of giant magnetoresistance in strongly correlated Dirac semimetals and its correlation with electronic correlation effects are revealed.\n19. Quantum Monte Carlo fermion spectroscopy of a non-compact CP$^1$ model Relevance Score: 3.1838 Authors: Xu Zhang, Nick Bultinck Link: http://arxiv.org/abs/2605.13945v1 Summary: This work employs the quantum Monte Carlo method to study a model coupling electrons with antiferromagnetic spin fluctuations. By suppressing hedgehog defects in the order parameter field, the bosonic part realizes a non-compact CP^1 theory, thereby obtaining a system with a deconfined U(1) gauge field. The authors strongly couple bosons with fermionic spins, define a sign-problem-free electron-boson model on a bilayer square lattice, and simulate its single-particle spectral properties using QMC. The rotating reference frame theory describes the system as fractionalized spinon and chargon excitations. The main findings are as follows: At half-filling, the system exhibits an insulating state with low-energy excitations being gapless photons. On this background, the gapped dispersion of electrons is strikingly similar to that of electrons in the antiferromagnetic mean-field theory, although the system fully retains translational and spin-rotational symmetries. However, upon doping, due to the strong interlayer pairing tendency, the system directly enters a superconducting state, hindering the numerical realization of a topological metallic state. On the other hand, the dispersion for electron doping indeed matches theoretical expectations, but that for hole doping does not. These results verify the predictions of the rotating reference frame theory regarding the single-electron doping dispersion in a U(1) spin liquid and suggest a possible analogous mechanism in high-temperature superconductors.\n20. Corner Charge Fluctuations in Higher Dimensions Relevance Score: 3.1522 Authors: Xiao-Chuan Wu, Pok Man Tam, Xuyang Liang, Zenan Liu, Dao-Xin Yao, Zheng Yan, Shinsei Ryu Link: http://arxiv.org/abs/2605.13971v1 Summary: This paper systematically investigates the angular contributions to subsystem charge fluctuations in high-dimensional spaces. In three dimensions, we derive the universal angle-dependent function corresponding to the trihedral angles of a general parallelepiped, and verify the theoretical predictions through Monte Carlo simulations of the O(3) quantum critical point. Furthermore, we identify a wedge-shaped angular contribution that directly probes the many-body quantum metric, supported by numerical calculations using a lattice Weyl semimetal model. More generally, we obtain the angular function for polyhedral angles of arbitrary parallelotopes in any dimension, and elucidate the scaling behavior of angular contributions in different phases: insulators and conformal critical points exhibit similar behavior across dimensions, while metals display characteristic odd-even dimensional effects. Methodologically, based on the definition of charge fluctuations under U(1) symmetry, we extract dimensionless angular contributions via a subtraction scheme and perform analytical calculations using the static structure factor; for three-dimensional systems, numerical simulations employ the columnar dimerized and bilayer cubic antiferromagnetic Heisenberg models. In arbitrary dimensions, we present a unified Gram matrix functional form and distinguish the distinct behaviors of insulators, conformal field theories, and metals. This work provides analytical tools for studying angular fluctuations in high-dimensional quantum many-body systems and establishes a direct connection between charge fluctuations and quantum geometry.\n","permalink":"https://nickelates.uk/en/posts/2026-05-16-arxiv-daily/","summary":"\u003cblockquote\u003e\n\u003cp\u003e\u003cstrong\u003eDaily Overview\u003c/strong\u003e:\nToday\u0026rsquo;s research in the field of nickelate superconductivity is characterized by a robust trend of experimental deepening and theoretical unification. On the experimental front, a study combining atomic-resolution scanning tunneling microscopy with spectroscopy has, for the first time, directly observed a nodeless U-shaped superconducting gap in (La,Pr)₃Ni₂O₇ superconducting thin films. It also reveals that precise control of oxygen content is an essential prerequisite for obtaining intrinsic spectra, providing key evidence for understanding the pairing symmetry of superconductivity. At the theoretical level, an important paper proposes a unified framework of \u0026ldquo;shear-stress-constrained superconductivity,\u0026rdquo; insightfully pointing out that non-hydrostatic pressure or epitaxial strain themselves are not the direct cause of superconductivity; rather, the key lies in the local Ni-O framework constraint deformation achieved through shear stress. This scenario offers a cross-scale unified quantitative perspective for understanding the fragility, heterogeneity, and reproducibility challenges of superconducting behavior in both high-pressure bulk and thin-film systems. Additionally, this week\u0026rsquo;s submissions also include several studies on strongly correlated electron systems closely related to superconductivity, such as a dynamical scaling analysis of the pseudogap-to-Fermi-liquid quantum critical point in the two-dimensional Hubbard model, and an ultrafast spectroscopy study of the rapid decoupling between quasiparticles and spin fluctuations in superconducting cuprates. These works, in mutual reflection with core issues in the nickelate field, collectively advance the understanding of unconventional superconductivity and strongly correlated electronic states.\u003c/p\u003e","title":"arXiv Daily: Nickelate superconductors 2026-05-16"},{"content":" Daily Overview: Today, there are no directly related new paper preprints on the field of nickelate superconductors. However, several works in this issue focus on superconductivity, strongly correlated electron systems, and unconventional pairing mechanisms, which are highly relevant to the core scientific questions of nickelate superconductors. For example, [1] presents direct evidence of quantum critical spin fluctuations in the strange metal phase of cuprates via nuclear magnetic resonance, and its spatial inhomogeneity and electronic phase separation characteristics offer valuable insights for understanding analogous phenomena in nickelates. [3] discovers a strongly correlation-driven Nagaoka supermetal state in the triangular-lattice Hubbard model; its sublinear resistivity behavior and band renormalization mechanism provide a new perspective for exploring non-Fermi liquid behavior in nickelates. [8] systematically analyzes superconducting pairing symmetries in multiorbital systems using the exactly solvable Hatsugai-Kohmoto model, offering a theoretical framework for understanding orbital-selective pairing in nickelates. [11] and [15] investigate symmetry-driven topological superconducting states in altermagnets and spin-filtering and nonreciprocal transport in altermagnet/Ising superconductor junctions, respectively; these synergistic effects of spin-orbit coupling and superconductivity are instructive for designing nickelate-based heterostructures. Although these studies do not directly address nickelates, the strongly correlated physics, pairing symmetries, and interface effects they reveal are expected to provide important references for exploring the mechanism and functional applications of nickelate superconductors.\n1. Singular spin fluctuations in the strange-metal phase of La2-xSrxCuO4 Relevance Score: 4.7002 Authors: B. Costarella, L. Soriano, I. Vinograd, H. Mayaffre, S. Li, J. Yang, J. Luo, R. Zhou, J. Yao, G. Gu, Q. Li, J. M. Tranquada, M. -H. Julien Link: http://arxiv.org/abs/2605.13573v1 Summary: This paper systematically investigates low-energy spin fluctuations in the overdoped strange metal phase of La₂₋ₓSrₓCuO₄ (x = 0.25) by exploiting high magnetic fields to suppress superconductivity and employing a 139La nuclear magnetic resonance (NMR) protocol optimized for electronic inhomogeneity. Measurements of the spin-lattice relaxation rate reveal that the low-energy dynamic spin susceptibility χ\u0026rsquo;\u0026rsquo;(q, ω) increases continuously as the temperature decreases to the lowest experimental temperature (1.34 K), exhibiting a divergent trend consistent with Curie-Weiss or power-law behavior, independent of the external magnetic field strength (20 T or 26 T). This anomalous temperature dependence aligns with the characteristics of quantum critical fluctuations, despite the doping level (x = 0.25) being far above the critical doping for spin stripe order (x ≈ 0.19), indicating the existence of quantum critical dynamics over a broader doping range. Further analysis unveils spatially inhomogeneous spin dynamics: the nuclear magnetization recovery curves deviate from a single-exponential form, and the distribution of relaxation rates can be described by a stretched exponential or a two-component model, with the fast component occupying approximately 25–30% of the sample volume. This suggests that nanoscale hole doping inhomogeneity prevents the freezing of local spin stripe regions, thereby sustaining persistent critical fluctuations. This study provides direct evidence that the strange metal phase originates from quantum critical-like spin fluctuations and underscores the crucial role of electronic inhomogeneity in understanding this phase.\n2. Yu-Shiba-Rusinov States in Ising Superconductors Relevance Score: 4.4719 Authors: Michael Hein, Juan Carlos Cuevas, Wolfgang Belzig Link: http://arxiv.org/abs/2605.12758v1 Summary: This paper theoretically investigates the Yu-Shiba-Rusinov (YSR) bound states induced by magnetic impurities in Ising superconductors to reveal their unconventional pairing characteristics. The authors construct a model for two-dimensional transition metal dichalcogenide superconductors incorporating Ising spin-orbit coupling (ISOC) and an in-plane magnetic field. The magnetic impurity is described using a single-impurity Anderson model in the classical spin limit, considering three hybridization scenarios: spin-polarized, spin-flip, and spin-independent. The bound state energy spectrum is obtained by solving the Dyson equation, and the Josephson current is also analyzed. The results show that, compared to conventional s-wave superconductors, the YSR energy spectrum in Ising superconductors exhibits two salient features: first, there exist two pairs of particle-hole symmetric subgap bound states (instead of one pair), which may cross or develop a gap at finite energies; second, the spectrum strongly depends on the orientation of the impurity magnetic moment relative to the ISOC and the in-plane magnetic field, leading to a shift and asymmetry of the zero-energy quantum phase transition point. These features originate from the combined effect of ISOC and the magnetic field, which breaks spin rotational symmetry and induces triplet pairing components. Moreover, the YSR states remain stable even under high in-plane magnetic fields far exceeding the Pauli limit, attributable to the spin-valley locking protection of Ising superconductors. This work demonstrates that magnetic impurities, as local probes, can sensitively distinguish Ising superconductors from conventional ones, and their bound state spectra and tunneling responses provide experimentally detectable signatures of unconventional superconductivity.\n3. Nagaoka supermetal in the particle-doped triangular Hubbard model Relevance Score: 4.4074 Authors: Rui Cao, Xiangyue Zhang, Hui Tan, Jian-Shu Xu, Yuan-Yao He, Jianmin Yuan, Yongqiang Li Link: http://arxiv.org/abs/2605.13837v1 Summary: This paper investigates the low-temperature properties of the triangular lattice Hubbard model with particle doping using the Dynamical Cluster Approximation (DCA), revealing an intrinsic quantum state driven by strong correlations—the Nagaoka supermetal (NS). This state exhibits a sublinear temperature dependence in the DC resistivity (e.g., ρ ~ T^α, α \u0026lt; 1), while the charge compressibility and zero spectral weight display power-law divergent behavior. To uncover its microscopic origin, the authors derive a low-energy effective model, demonstrating that strong correlations induce effective next-nearest-neighbor hopping via Nagaoka polarons, leading to band reconstruction and the emergence of a higher-order Van Hove singularity (HOVHS) near the Γ point. This results in a power-law divergence in the density of states (e.g., ρ(ω) ~ |ω - ω_0|^{-1/2}). The scaling behavior of this HOVHS is consistent with the power-law exponents of the charge compressibility and resistivity, validating the nature of the NS state. The study shows that the stability of the NS state is modulated by the interaction strength U, and its key features remain robust within experimentally accessible temperature and interaction ranges. This discovery provides new insights into non-Fermi liquid behavior in geometrically frustrated systems and can be directly verified in cold atom quantum simulation experiments.\n4. Reentrant behavior and possible $2/3$ magnetization plateau on the double-trillium langbeinite K$_2$Ni$_2$(SO$_4$)$_3$ Relevance Score: 4.2528 Authors: Matías G. Gonzalez, Yurii Skourski, Johannes Reuther, Ivica Živković Link: http://arxiv.org/abs/2605.13263v1 Summary: This paper systematically investigates the magnetization process of the double-tripleme langbeinite compound K₂Ni₂(SO₄)₃ by combining pulsed magnetic field experiments (up to 40 T) with classical Monte Carlo (cMC) calculations. The material is composed of interwoven strongly coupled tripleme sublattices (strong-TL) and weakly coupled tripleme sublattices (weak-TL), and its Heisenberg Hamiltonian exhibits high frustration. The experimentally measured magnetization curves show a rapid increase in the low-field region, followed by an approximately linear rise toward the saturation field, while the derivative curves reveal a series of low-field and intermediate-field phase transitions. The cMC simulations, using previously validated exchange coupling parameters, accurately reproduce both the saturation field and multiple phase transition peaks observed in experiments. In the intermediate magnetic field region, a pronounced \u0026ldquo;dome\u0026rdquo; structure is identified: the system tends to form a 2/3 magnetization plateau phase composed of a 1/3 magnetization phase of the strong-TL and a fully polarized phase of the weak-TL. Although a strict plateau is not expected in the classical limit, this dome structure leads to re-entrant behavior as the temperature increases—namely, the system restores the Hamiltonian symmetry with increasing magnetic field. Further studies indicate that such plateau-like phases also exist in the classical Heisenberg model of single tripleme and quadruple tripleme lattices, suggesting their universality in the family of double-tripleme langbeinite materials. This work provides strong motivation for exploring plateau phases in such materials under the quantum limit.\n5. Frustrated Magnetism of the $S = 1$ Trillium-Lattice Oxide Li$_2$NiGe$_3$O$_8$ Relevance Score: 4.1215 Authors: Yuya Haraguchi Affiliations: Tokyo University of Agriculture and Technology Link: http://arxiv.org/abs/2605.12962v1 Summary: This paper reports magnetic susceptibility and heat capacity measurements of the ordered spinel oxide Li₂NiGe₃O₈, in which Ni²⁺ ions (S=1) form a single three-dimensional hyperkagome lattice. Powder X-ray diffraction confirms a cubic ordered spinel structure with space group P4₁32 or P4₃32. Magnetic susceptibility measurements show that the inverse susceptibility H/M follows Curie-Weiss behavior above 50 K, with an effective magnetic moment μeff = 3.124(4) μB and a Weiss temperature θ_W = -0.21(1) K, but deviates smoothly below about 10 K. The magnetic specific heat C_mag/T exhibits a broad peak at around 3 K extending to about 10 K, and the recovered entropy between 2 and 40 K amounts to approximately 88% of R ln3. Comparison with Monte Carlo results for a local ferromagnetic Ising model on the hyperkagome lattice yields a characteristic energy scale J of about 7 K, while the inverse susceptibility only qualitatively resembles the theoretical curve. These results establish Li₂NiGe₃O₈ as a rare S=1 single hyperkagome oxide with frustrated magnetic correlations. This data provides an experimental platform for exploring the relationship between the Heisenberg-type and spin-ice-type regimes on the hyperkagome lattice.\n6. Reconfigurable chiral superconductivity Relevance Score: 4.0432 Authors: Surajit Dutta, Nadav Auerbach, Tonghang Han, Yaozhang Zhou, Gal Shavit, Niladri-Sekhar Kander, Yuri Myasoedov, Martin E. Huber, Kenji Watanabe, Takashi Taniguchi, Long Ju, Eli Zeldov Affiliations: Massachusetts Institute of Technology, California Institute of Technology, National Institute for Materials Science, University of Colorado Denver, Weizmann Institute of Science Link: http://arxiv.org/abs/2605.13303v1 Summary: This study employs a nanoscale SQUID-on-tip magnetometer to directly image isospin-polarized domains in rhombohedral pentalayer graphene and confirms time-reversal symmetry breaking through spatially resolved thermodynamic detection, thereby establishing the existence of a chiral superconducting state. The findings reveal that the density of domain walls proliferating at high temperatures coincides precisely with the onset of chiral superconductivity, indicating a transition in the parent state that simultaneously induces superconductivity and reduces domain wall energy. The chiral domain structure in the superconducting phase is inherited from the isospin-polarized parent state. Remarkably, the chiral superconducting phase exhibits diverse transport behaviors governed by the configuration of chiral domains separated by highly resistive domain walls. Experiments further demonstrate deterministic, ultra-low-current domain control enabling reversible switching between opposite chirality states—a hallmark feature of chiral superconductivity absent in other superconductors. These results establish rhombohedral graphene as a unique platform for reconfigurable chiral superconductivity and ultra-low-power electronic functionalities based on controllable isospin textures.\n7. Shubnikov-de Haas Characterization of Superconductor-Semiconductor Heterostructures Relevance Score: 3.9576 Authors: A. M. Zimmerman, Saeed Fallahi, Sergei Gronin, Tyler Lindemann, Patrick Sohr, Ray Kallaher, Alejandro Alcaraz Ramirez, Georg W. Winkler, Samuel M. L. Teicher, William Cole, Sebastian Heedt, Eoin O\u0026rsquo;Farrell, Gijs de Lange, Roman Lutchyn, Michael J. Manfra, John Watson Link: http://arxiv.org/abs/2605.13722v1 Summary: We have developed a new method for measuring superconductor-semiconductor heterostructures using Shubnikov-de Haas (SdH) oscillations. This method is performed in a two-dimensional electron gas (2DEG) in an InAs quantum well beneath an aluminum film, enabling the extraction of key material parameters without the need for nanofabrication or ultra-low temperatures (above 1 K suffices). By analyzing the full magnetoresistance data, we can simultaneously obtain the carrier density, Rashba spin-orbit coupling strength, and both transport and quantum scattering times of the quantum well. The key innovation lies in the fact that the scattering time measured in the 2DEG is directly influenced by the strength of the metal-semiconductor coupling, which determines the proximity-induced superconducting gap. Thus, by merely obtaining the scattering time from SdH oscillations, one can rapidly assess the size of the superconducting gap without the need to fabricate complex devices such as quantum point contacts. Experiments have validated the method’s sensitivity to variations in quantum well composition (e.g., introducing Sb) and changes in the metal-semiconductor coupling at the barrier layer. This technique provides a rapid feedback tool for material optimization in superconductor-semiconductor heterostructures, thereby accelerating research in areas such as Josephson junctions and Majorana qubits.\n8. Multiband Superconductivity in the Exactly Solvable Hatsugai-Kohmoto Model Relevance Score: 3.8896 Authors: Nico Hahn, R. Matthias Geilhufe Link: http://arxiv.org/abs/2605.13259v1 Summary: This paper investigates superconductivity in the multi-orbital Hatsugai-Kohmoto (HK) model. As an exactly solvable correlated electron model with momentum-local interactions, it provides a minimal framework for studying the interplay of strong correlations, orbital structure, and pairing symmetry. We focus on a two-orbital system with D₄h point group symmetry and systematically classify the symmetry-allowed superconducting gap structures in terms of spin, orbital, and momentum degrees of freedom. Within the mean-field approximation, we calculate the critical temperature and superconducting order parameters for several selected pairing channels as functions of interaction strength and pairing strength. The results show that in the weak interaction regime (below the Mott transition), the free energy exhibits conventional BCS behavior, with the global minimum transitioning continuously from a nonzero order parameter to zero below the critical temperature. In the Mott insulator regime, however, the free energy landscape becomes anomalous: the global minimum remains at a nonzero order parameter at low temperatures, but as temperature increases, this minimum is separated from the normal-state solution by a local maximum, leading to a discontinuous superconducting transition. Our results provide a systematic framework for analyzing superconductivity in orbital HK models and extend the symmetry-based approach to correlated multi-band systems.\n9. Magnetocaloric Effect in Nanostructured $La_{0.6}Sr_{0.4}Fe_{1-x}Co_{x}O_3$ Relevance Score: 3.7078 Authors: Fabiana N. Morales Alvarez, Mariano Quintero, Joaquín Sacanell Affiliations: CNEA, CNEA-CONICET Link: http://arxiv.org/abs/2605.13611v1 Summary: This study systematically investigates the magnetocaloric effect of nanostructured perovskite series La₀.₆Sr₀.₄Fe₁₋ₓCoₓO₃ (x = 0, 0.2, 0.5, 0.8, 1.0). The samples were synthesized via the pore wetting method using polymer membranes with pore sizes of 200 nm and 800 nm, followed by calcination at 1000°C. X-ray diffraction analysis confirmed that all samples formed a single rhombohedrally distorted perovskite phase without any impurity phases. Scanning electron microscopy observations revealed that as the cobalt content increased, the morphology gradually evolved from fine nanotubes and nanoparticles to coarser nanotubes and nanowires. Magnetic measurements indicated that cobalt substitution for iron enhanced ferromagnetic coupling, leading to a significant increase in saturation magnetization and Curie temperature. The magnetocaloric effect, calculated based on the Maxwell relation, showed that under an applied magnetic field of 3 T, the pure cobalt sample (x=1) exhibited the maximum magnetic entropy change of 1.13 J/(kg·K), and all samples displayed characteristics of a second-order magnetic phase transition. The results suggest that the magnetocaloric response of this system can be effectively optimized through the synergistic regulation of cobalt doping and nanostructured morphology, providing a new approach for designing efficient magnetocaloric materials.\n10. Correlation-driven tunability of altermagnetism in RuO$_2$ Relevance Score: 3.6744 Authors: Ina Park, Dongwook Kim, Jisook Hong, Beomjoon Goh, Bo Gyu Jang Link: http://arxiv.org/abs/2605.13559v1 Summary: This work employs density functional theory combined with dynamical mean-field theory (DFT+DMFT) to investigate the electronic correlation effects and their impact on altermagnetism in RuO₂. In contrast to previous studies based on static DFT, the DFT+DMFT method effectively captures dynamical correlation effects, yielding calculated spectral functions and optical conductivities in quantitative agreement with experiments, thereby confirming the applicability of this method for describing the system. The study reveals that the intrinsic ground state of RuO₂ lies near the phase boundary between the paramagnetic and altermagnetic phases, while simultaneously residing at the crossover between itinerant and localized electrons. This dual proximity renders the magnetic ground state highly sensitive to external perturbations. For instance, a tiny compressive strain of merely about 0.5% suffices to drive the system into the altermagnetic phase. By analyzing the phase diagrams for varying Coulomb interaction and Hund coupling parameters, the band renormalization induced by dynamical correlations is unveiled: flat bands approach the Fermi level, increasing the density of states and triggering magnetic instabilities. Meanwhile, the system exhibits Hund metal behavior, with the exchange energy showing non-monotonic variation as correlations strengthen near the itinerant-to-localized boundary. These results elucidate previously conflicting experimental observations, demonstrating that the magnetic ground state of RuO₂ is not a rigid altermagnetic order but is highly tunable, with dynamical correlation effects serving as the key driving force.\n11. Nodal Topological Superconductivity Driven by Crystalline Antiunitary Symmetry in Altermagnets Relevance Score: 3.5310 Authors: Xiao Xiao, Arun Bansil Link: http://arxiv.org/abs/2605.13656v1 Summary: This paper investigates how crystalline antiunitary symmetry constrains superconducting pairing and generates nodal topological superconducting states in fourfold rotation collinear altermagnets. Through group theory analysis, the authors find that this symmetry prohibits pure spin-singlet pairing and enforces the mixing of spin-singlet and spin-triplet (along the spin quantization axis component) states, resulting in a Bogoliubov-de Gennes (BdG) Hamiltonian with chiral symmetry. Using linearized gap equations and nearest-neighbor interactions, the authors determine the phase diagram of the dominant pairing channels, obtaining three robust topological nodal superconducting phases over a wide parameter range: a nodal point phase (with Majorana flat bands) and two distinct nodal loop phases (with chiral Majorana edge states). Notably, the nodal structures persist even when antiunitary symmetry is spontaneously broken, indicating that the topology originates from symmetry-constrained pairing rather than direct symmetry protection. Finally, the paper proposes distinguishing these nodal phases and detecting symmetry-breaking signals via tunneling spectroscopy experiments: the Majorana flat bands in the nodal point phase give rise to zero-bias conductance peaks; in the nodal loop phase preserving antiunitary symmetry, tunneling spectra from semi-metallic electrodes with different orientations are identical; in the nodal loop phase with spontaneously broken symmetry, the tunneling spectra exhibit anisotropy. This work provides a symmetry-driven intrinsic mechanism for realizing topological superconductivity in altermagnets, without requiring strong spin-orbit coupling or fine-tuning.\n12. Magnetic fields in monoclinic $α$-RuCl$_3$ reveal rhombohedral inclusions underlying apparent oscillations Relevance Score: 3.5033 Authors: Hamza Nasir Daniel Balazs, Muhammad Nauman, Ezekiel Horsley, Subin Kim, Young-June Kim, K. A. Modic Link: http://arxiv.org/abs/2605.13444v1 Summary: By studying nanoscale monoclinic α-RuCl₃ single crystals (approximately 35.9 ng) in conjunction with high-resolution magneto-optical measurements, the antiferromagnetic phase diagrams under different crystal planes, temperatures, and magnetic fields were systematically mapped. The experiments revealed that the antiferromagnetic phase diagram of the monoclinic phase is qualitatively similar to that of the rhombohedral structure, but shifted overall to higher temperatures (~8 K) and higher critical fields. Moreover, when the magnetic field is oriented along the a direction, a two-step suppression of the antiferromagnetic order is observed, corresponding to the ZZ₂ intermediate ordered phase analogous to that in rhombohedral samples. More importantly, in the high-field region for specific in-plane magnetic field directions (close to the a-axis), multiple oscillations appear in the magneto-optical signal, with a narrow angular range (within approximately 30°) and a close correlation with the antiferromagnetic boundary of the monoclinic phase. Analysis indicates that these oscillations do not originate from a new non-magnetic phase or a quantum spin liquid, but rather from additional antiferromagnetic phase boundaries introduced by a small number of rhombohedral stacking inclusions stabilized or enhanced by the magnetic field. Consequently, the transport oscillations previously attributed to quantum spin liquids are essentially a cascading effect of phase boundaries resulting from the coexistence of monoclinic and rhombohedral structures within the sample, rather than an intrinsic quantum state. This finding underscores the critical influence of structural symmetry and sample uniformity on the interpretation of field-induced phenomena in α-RuCl₃ and related two-dimensional quantum magnets, and suggests that incomplete structural phase transitions may serve as an important source of signals resembling those of quantum spin liquids.\n13. Incommensurate Spin-Density Waves in a Frustrated Maple-Leaf Lattice Ferromagnet Relevance Score: 3.4703 Authors: Paul L. Ebert, Yasir Iqbal, Alexander Wietek Link: http://arxiv.org/abs/2605.12592v1 Summary: This study systematically investigates the phase diagram of the spin-1/2 nearest-neighbor Heisenberg model with competing ferromagnetic and antiferromagnetic interactions on the maple-leaf lattice using exact diagonalization (ED) and tower state analysis. Methodologically, calculations are performed on clusters of various sizes using the XDiag library, with phases identified through energy spectra, irreducible representations, structure factors, and multi-level state spectra. The results indicate that no zero-field spin nematic phase exists near the ferromagnetic boundary; instead, a broad region of incommensurate spin density wave (SDW) appears, with its ordering vector evolving continuously. The phase diagram also includes collinear Néel antiferromagnetic, canted 120°, and hexagonal singlet (HS) phases, though certain regions remain difficult to classify definitively via ED. For these unresolved regions, variational Monte Carlo tests of fully symmetric Gutzwiller-projected Abrikosov-fermion U(1) and Z₂ spin liquid states yield no competitive description. However, between the collinear Néel and HS phases near the ruby lattice boundary, a projected Z₂ Ansatz accurately reproduces the finite-size energies and spin correlations. This study refutes previously assumed zero-field spin nematic and dimerized hexagonal singlet phases, suggesting that the instability of the ferromagnetic phase originates from incommensurate spin density waves rather than a magnon bound-state mechanism. The results reveal a distinct mechanism for ferromagnetic destruction in the maple-leaf lattice, offering new insights into related materials such as Na₂Mn₃O₇.\n14. Ultrafast Critical Slowing of Spin Dynamics and Emergent Nonequilibrium Fano Interference in Fe3GeTe2 Relevance Score: 3.4534 Authors: Anupama Chauhan, Sidhanta Sahu, Satyabrata Bera, Tuhin Debnath, Mintu Mondal, Anamitra Mukherjee, Siddhartha Lal, N. Kamaraju Link: http://arxiv.org/abs/2605.13121v1 Summary: This study systematically investigates the ultrafast coupling dynamics of electronic, spin, and lattice degrees of freedom near the magnetic phase transition in the van der Waals ferromagnet Fe₃GeTe₂ using two-color pump-probe reflection spectroscopy. The time-resolved reflectivity exhibits a triexponential relaxation behavior: the intermediate relaxation component (~7 ps) shows an anomaly near the Curie temperature (Tc ≈ 220 K), attributed to enhanced interlayer spin-lattice interactions; the slowest relaxation component (~300 ps) displays significant critical slowing down, with a dynamic critical exponent of approximately 0.3, which is below the universal value expected from standard magnetic models, revealing non-universal relaxation dynamics associated with intralayer spin correlations. Additionally, Fano asymmetry of the non-equilibrium A₁g optical phonon is observed: this asymmetry is suppressed in the ferromagnetic phase but anomalously enhanced in the paramagnetic phase. A microscopic model suggests that this phenomenon arises from thermally activated anharmonic decay processes that bridge the kinematic gap between the optical phonon and the hot electron continuum, thereby enhancing the quantum interference between the phonon and the electron continuum. Meanwhile, a significant enhancement of the acoustic strain pulse amplitude is observed near Tc, further confirming strong magnetoelastic coupling. These results elucidate how magnetic order regulates the intricate interplay among critical spin dynamics, electronic continuum excitations, and lattice responses in metallic van der Waals ferromagnets.\n15. Interface controlled spin filtering and nonreciprocal transport in Altermagnet/Ising superconductor junctions Relevance Score: 3.4401 Authors: Arindam Boruah, Saumen Acharjee, Prasanta Kumar Saikia Link: http://arxiv.org/abs/2605.13317v1 Summary: This paper investigates spin-resolved transport, spin filtering, and non-reciprocal effects in altermagnet/Ising superconductor (AM/ISC) junctions with a spin-active interface through theoretical calculations. Using a modified Bogoliubov-de Gennes framework and scattering formalism, the interplay among intrinsic spin–orbit coupling (ISOC), anisotropic AM spin texture, and spin-dependent interface scattering is analyzed. The results indicate that charge and spin conductances exhibit strong anisotropy: in the weak spin-mixing regime, transport predominantly maintains helicity conservation and is significantly modulated by the relative orientation between the AM spin texture and the interfacial magnetization; increasing ISOC enhances spin conductance and leads to spin-selective Andreev reflection, thereby enabling finite spin filtering. In the strong spin-mixing regime, angular anisotropy is further enhanced, achieving robust spin-polarized transport over a wide energy range, while conventional Andreev reflection is strongly suppressed. Non-reciprocal transport persists across the single-band, intermediate, and double-band ISC regimes. The spin polarization and spin filtering efficiency exhibit non-monotonic variations with system parameters, reaching up to approximately 86%, with their angular modulation characteristics determined by the AM spin texture. Spin selectivity is enhanced in the low-energy region but suppressed near the superconducting gap. These results establish AM/ISC junctions as a versatile platform for tunable superconducting spintronics and directional spin transport.\n16. Site-selective preparation of two-dimensional dipolar quantum gases in an optical beat-note lattice Relevance Score: 3.4153 Authors: Niclas Höllrigl, Marian Kreyer, Rudolf Grimm, Emil Kirilov Link: http://arxiv.org/abs/2605.13482v1 Summary: We propose an all-optical method for deterministically preparing single and double layers of cold dipolar atomic samples via spatially selective parametric heating in a superlattice. This method addresses the challenge of isolating individual atomic layers using standard magnetic gradient techniques in high-resolution two-dimensional dipolar quantum gas microscopy, particularly for strongly magnetic lanthanide atoms. By employing a high-resolution microscope objective as a common retroreflector for two optical frequency components, the lattice planes are passively stabilized, rendering their positions highly robust against experimental drifts and structural vibrations, while maintaining millimeter-scale distances without the need for active laser stabilization. Experimental validation demonstrates that one or two atomic layers can be robustly isolated, precisely coinciding with the focal plane of the objective. By measuring the local excitation frequency of the superlattice and characterizing the atomic distribution, we demonstrate the ability to remove atoms layer by layer to prepare isolated single or bilayer geometries, and confirm the alignment of the sample with the focal plane through contrast detection of the short-period optical lattice. This method relies entirely on far-detuned optical potentials, is applicable to different cold atom species, and does not depend on quantum statistics or internal state structure, providing a crucial tool for future studies of long-range interacting systems at the single-atom resolution level.\n17. From Film to Flakes: Electronic Properties and Magnetization Variations in Yttrium Iron Garnet Relevance Score: 3.3721 Authors: Pia M. Düring, Seema, Roman Hartmann, Sebastian Sailler, Michaela Lammel, Andrei Gloskovskii, Christoph Schlueter, Angelo Di Bernardo, Sebastian T. B. Goennenwein, Martina Müller Link: http://arxiv.org/abs/2605.13441v1 Summary: This study systematically compares the electronic structure and magnetic properties of bulk yttrium iron garnet (YIG) films and submicron YIG flakes. Hard X-ray photoelectron spectroscopy (HAXPES) analysis reveals that the YIG film exhibits only Fe³⁺ contributions, while the YIG flake shows an additional Fe⁰ metallic peak (binding energy 707.2 eV) in the Fe 2p spectrum, with an Fe³⁺ to Fe⁰ intensity ratio of approximately 2:1. The stronger Fe⁰ signal under surface-sensitive 2.8 keV incident light suggests that metallic iron is primarily concentrated on the flake surface. Further analysis of Y 3p and O 1s spectra indicates that Y in the flake remains in the Y³⁺ oxidation state, while the oxygen signal is interfered with by the SiO₂ substrate, making it difficult to definitively determine oxygen deficiency. Combining EDX data and literature on oxide formation energies, it is inferred that the flake contains oxygen defects, preferentially forming Y³⁺, which leads to the breaking of Fe–O bonds and the formation of Fe⁰. Magnetic domain observations were conducted using longitudinal Kerr microscopy. The YIG film exhibits a hysteresis loop with a coercive field of approximately 1.7 mT, but the domain wall contrast is weak. The hysteresis loop of the YIG flake shows shape anisotropy, with an enhanced coercive field after rotation, and the Kerr contrast amplitude is only about half that of the film, significantly lower than that of a Fe reference film. This study confirms that at the submicron scale, YIG flakes exhibit changes in Fe valence state and magnetic properties due to oxygen defects, and their mechanical transferability provides a new route for constructing compact spintronic devices, such as heterojunctions or superconducting applications.\n18. Imaging Interacting Two-Dimensional Anisotropic Electrons Relevance Score: 3.3366 Authors: Ziyu Xiang, Jianghan Xiao, Hongyuan Li, Woochang Kim, Tianle Wang, Zhihuan Dong, Takashi Taniguchi, Kenji Watanabe, Michael P. Zaletel, Steven G. Louie, Michael F. Crommie, Feng Wang Affiliations: Lawrence Berkeley National Laboratory, Kavli Energy Nano Sciences Institute, University of California at Berkeley, National Institute for Materials Science Link: http://arxiv.org/abs/2605.12761v1 Summary: This paper reports the direct observation of a two-dimensional anisotropic Wigner crystal and its quantum melting process in monolayer 1T\u0026rsquo;-ReSe₂ using a non-invasive scanning tunneling microscope. ReSe₂ exhibits anisotropic effective mass, with electron wavefunctions elongated along the light-mass direction to reduce kinetic energy. At low electron densities, these anisotropic electrons form an oblique Wigner lattice, in contrast to the triangular lattice observed in isotropic systems. By fitting the elliptical density distribution of individual electrons, the experiment directly determines, for the first time, the effective mass anisotropy ratio (heavy-to-light mass ratio ~8.4) and the slight deviation of the light-mass direction from the rhenium chain direction (~9°), which are consistent with density functional theory calculations. As the electron density increases, quantum fluctuations grow more rapidly along the light-mass direction, leading to one-dimensional melting of the Wigner crystal along that direction, while order is maintained along the heavy-mass direction. This partially melted state corresponds to a smectic electronic liquid crystal phase intermediate between an electron solid and a Fermi liquid. This study not only provides a direct imaging method for anisotropic correlated electron systems but also establishes a platform for exploring novel quantum phenomena such as coupled one-dimensional electron chains, sliding Luttinger liquids, and non-Fermi liquid behavior.\n19. High-Pressure XRD Study of Ti-3Al-2.5V Titanium Alloy: Intermediate Transition Pressure and Composition Trends in Ti-Al-V Alloys Relevance Score: 3.1857 Authors: D. Errandonea, R. Turnbull, P. Botella, R. Oliva, C. Popescu, S. MacLeod Affiliations: CELLS-ALBA Synchrotron Light Facility, CSIC, Universitat de València, AWE Link: http://arxiv.org/abs/2605.13658v1 Summary: Through high-pressure X-ray diffraction experiments on Ti-3Al-2.5V titanium alloy using three different pressure-transmitting media—methanol-ethanol, silicone oil, and MgO—the influence of alloy composition on structural stability was systematically investigated. The experiments revealed that the α→ω phase transition in Ti-3Al-2.5V occurs at 17–19 GPa, lying between that of pure titanium (5–10 GPa) and Ti-6Al-4V (approximately 30 GPa). Although non-hydrostatic conditions introduced by different pressure-transmitting media slightly affect the transition pressure, the overall trend is clear: as the Al and V content increases, the phase transition pressure systematically rises. Equation of state analysis indicates that the bulk modulus of each alloy composition remains nearly unchanged, suggesting a decoupling between elastic properties and phase stability. Thus, alloying primarily influences the phase transition pressure rather than compressibility. Additionally, the reversibility of the phase transition is affected by the pressure-transmitting medium: it is irreversible in methanol-ethanol but partially reversible in silicone oil and MgO. This study reveals the critical role of composition in regulating the high-pressure phase transition of Ti-Al-V-based alloys, providing experimental evidence for understanding the impact of alloying elements on structural stability.\n20. Negative Differential Resistance and Ultra-High TMR in Altermagnetic Tunnel Junctions Relevance Score: 3.1775 Authors: Sajjan Sheoran, Luke Keenan, Declan Nell, Stefano Sanvito Link: http://arxiv.org/abs/2605.12711v1 Summary: This study, using non-equilibrium Green\u0026rsquo;s function combined with density functional theory, predicts a significant low-bias negative differential resistance effect in magnetic tunnel junctions based on the orbitally ordered altermagnet KV2Se2O. The tunnel junction employs KV2Se2O electrodes and an MgO barrier, with its quasi-two-dimensional Fermi surface contributed by highly anisotropic d orbitals, forming a sheet-like Fermi surface. Under parallel magnetization configuration, the current first increases sharply with bias and is almost completely suppressed at approximately 0.14 V, resulting in a pronounced Λ-shaped negative differential resistance; in contrast, the current increases monotonically under the antiparallel configuration. This behavior arises from the perfect overlap in momentum space of the same-spin Fermi surfaces of the two electrodes in the parallel state, where the bias causes the Fermi surfaces to drift in opposite directions, leading to a rapid decrease in overlap area until it vanishes; in the antiparallel state, due to the orthogonal spin channels, the overlap remains essentially unchanged. On this basis, the tunneling magnetoresistance reaches up to ~2000% at zero bias and undergoes a sign reversal near 0.13 V, with its absolute value increasing again to ~6000%. The combination of zero net magnetization unique to altermagnets, ultrafast switching characteristics, and strong nonlinear response suggests that such tunnel junctions hold potential for applications in low-bias high-frequency electronic devices, multi-valued logic, and magnetic random-access memory.\n","permalink":"https://nickelates.uk/en/posts/2026-05-15-arxiv-daily/","summary":"\u003cblockquote\u003e\n\u003cp\u003e\u003cstrong\u003eDaily Overview\u003c/strong\u003e:\nToday, there are no directly related new paper preprints on the field of nickelate superconductors. However, several works in this issue focus on superconductivity, strongly correlated electron systems, and unconventional pairing mechanisms, which are highly relevant to the core scientific questions of nickelate superconductors. For example, [1] presents direct evidence of quantum critical spin fluctuations in the strange metal phase of cuprates via nuclear magnetic resonance, and its spatial inhomogeneity and electronic phase separation characteristics offer valuable insights for understanding analogous phenomena in nickelates. [3] discovers a strongly correlation-driven Nagaoka supermetal state in the triangular-lattice Hubbard model; its sublinear resistivity behavior and band renormalization mechanism provide a new perspective for exploring non-Fermi liquid behavior in nickelates. [8] systematically analyzes superconducting pairing symmetries in multiorbital systems using the exactly solvable Hatsugai-Kohmoto model, offering a theoretical framework for understanding orbital-selective pairing in nickelates. [11] and [15] investigate symmetry-driven topological superconducting states in altermagnets and spin-filtering and nonreciprocal transport in altermagnet/Ising superconductor junctions, respectively; these synergistic effects of spin-orbit coupling and superconductivity are instructive for designing nickelate-based heterostructures. Although these studies do not directly address nickelates, the strongly correlated physics, pairing symmetries, and interface effects they reveal are expected to provide important references for exploring the mechanism and functional applications of nickelate superconductors.\u003c/p\u003e","title":"arXiv Daily: Nickelate superconductors 2026-05-15"},{"content":" Daily Overview: Today\u0026rsquo;s rapid overview of the nickelate superconductor field focuses on an important review work. A collaborative team from Nankai University and Zhejiang University has systematically summarized the experimental progress of superconducting bilayer nickelate thin films (RA₃Ni₂O₇) under ambient pressure. The review points out that La₃Ni₂O₇ and (La,Pr)₃Ni₂O₇ thin films grown on substrates such as SrLaAlO₄ via epitaxial strain have achieved superconducting onset temperatures exceeding 40 K, successfully reproducing the key structural features of high-pressure bulk materials under ambient conditions. However, the maximum superconducting transition temperature in current thin films remains lower than that of high-pressure bulk materials, indicating room for optimization. The article discusses synthesis methods, oxygen stoichiometry control, substrate-induced strain, normal-state transport behavior, and doping phase diagrams, while identifying several unresolved key issues, including the reproducibility of phase-pure ultrathin films, the microscopic origin of the two-step superconducting transition, the roles of oxygen defects and substrate doping, the Fermi surface crossing position of the Ni 3d(_{z^2}) (\\gamma) band, and the pairing symmetry. This work provides a controllable platform for understanding the microscopic mechanism of nickel-based superconductivity and clarifies the direction for future establishment of quantitative relationships among crystal structure, orbital reconstruction, and superconductivity. Only this one paper is featured today, but its content encompasses the latest experimental landscape and core challenges in the field.\n1. Experimental Progress in Ambient-Pressure Superconducting Bilayer Nickelate Films Relevance Score: 6.0698 Authors: Meng Zhang, Xi Yan Affiliations: Nankai University, Zhejiang University Link: http://arxiv.org/abs/2605.11584v1 Summary: This review summarizes the experimental progress in superconducting bilayer nickelate thin films (RA₃Ni₂O₇) under ambient pressure. Through epitaxial strain, the films successfully reproduce key structural features of high-pressure bulk materials, enabling transport, spectroscopic, microscopic, and device measurements to be conducted directly at ambient pressure. The article focuses on synthesis methods (PLD, MBE, GAE), oxygen stoichiometry control, substrate-induced strain, normal-state transport behavior, superconducting properties, doping phase diagrams, and momentum-resolved electronic structure. It is found that compressive-strained substrates can partially simulate the structural conditions of high pressure, with La₃Ni₂O₇ and (La,Pr)₃Ni₂O₇ films grown on substrates such as SrLaAlO₄ exhibiting superconducting onset temperatures exceeding 40 K. However, the current maximum superconducting transition temperature of the films remains lower than that of high-pressure bulk materials, indicating room for optimization. The review also identifies several unresolved key issues: the reproducibility of phase-pure ultrathin films, the microscopic origin of the two-step superconducting transition, the roles of oxygen vacancies and substrate doping, the Fermi surface crossing position of the Ni 3dₓ₂₋γ₂ band, and the pairing symmetry. Finally, future experimental directions are proposed, aiming to establish a more quantitative link between crystal structure, orbital reconstruction, and superconductivity, thereby providing a controllable platform for understanding the microscopic mechanism of nickelate superconductivity.\n2. Outstanding TC Enhancement in 5d-3d Y2NiIrO6 by Compression Relevance Score: 4.6181 Authors: Zheng Deng, Yao Zhang, Sijia Zhang, Jing Song, Wanli He, Yuanzhe Li, Meilin Jin, Xiang Li, Guanghua Liu, Zhen Dong, Jinkai Bi, Wenmin Li, Jianfa Zhao, Jun Zhang, Yi Peng, Luchuan Shi, Junling Meng, Xiancheng Wang, Changqing Jin Affiliations: Jilin Normal University, Chinese Academy of Sciences, Henan Academy of Sciences, Beijing Institute of Technology Link: http://arxiv.org/abs/2605.11590v1 Summary: This paper systematically investigates the structural, electronic transport, and magnetic evolution of double perovskite Y₂NiIrO₆ (YNIO) through physical compression methods. At ambient pressure, YNIO is a ferromagnetic insulator exhibiting a 5d J_eff=1/2 Mott insulating state of Ir⁴⁺. Using in-situ synchrotron X-ray diffraction, resistivity, and magnetic susceptibility measurements combined with first-principles calculations, key changes under pressures up to 17 GPa are revealed. Structural analysis shows that pressure simultaneously compresses Ni–O and Ir–O bond lengths and the Ni–O–Ir bond angle, with anisotropic unit cell volume contraction and the b-axis being nearly incompressible. Resistivity measurements indicate a monotonic decrease of the band gap from 0.36 eV (0.6 GPa) to 0.26 eV (16.8 GPa), with an average reduction rate of about −0.006 eV/GPa. Magnetic measurements show a significant increase in Curie temperature from 192 K to approximately 240 K, with enhancement rates of about +6 K/GPa at low pressures and about +2 K/GPa at high pressures. Unlike the 5d systems Sr₂IrO₄/Sr₃Ir₂O₇, the rock-salt ordered Ni–Ir structure in YNIO naturally blocks long-range superexchange beyond nearest neighbors, suppressing magnetic frustration. Moreover, the orthogonal Ni e_g–Ir t₂g superexchange pathway in YNIO remains stable under lattice distortion, whereas in the similar electronic configuration La₂NiMnO₆, bond bending leads to weakened superexchange. Compared to chemical compression in Lu₂NiIrO₆ (which only alters bond angles), physical compression simultaneously shortens bond lengths, more effectively enhancing hybridization, reducing the band gap, and raising the magnetic ordering temperature. These findings establish an explanatory framework for the 5d-3d superexchange mechanism and provide guidance for tuning magnetism in iridium-containing systems through bond engineering.\n3. Anomalous spin-pumping behavior of half-metallic ferromagnet/d-wave superconductor heterostructures Relevance Score: 4.3347 Authors: Hadi H. Hassan, Santiago J. Carreira, M. Cabero, F. Martinet, Alexander Buzdin, Jacobo Santamaria, Javier E. Villegas Affiliations: Université Paris Saclay, University Bordeaux I, Universidad Complutense de Madrid Link: http://arxiv.org/abs/2605.12381v1 Summary: This study systematically investigates the anomalous spin pumping behavior in epitaxial heterojunctions composed of the half-metallic ferromagnet La₀.₇Sr₀.₃MnO₃ (LSMO) and the d-wave superconductor YBa₂Cu₃O₇₋δ (YBCO) using ferromagnetic resonance (FMR) experiments. Two sets of samples with different crystal orientations were prepared: c-axis-oriented YBCO (001) and (103)-oriented YBCO, and the temperature-dependent Gilbert damping coefficient α(T) was measured. The results show that in the (103)-oriented heterojunction, α(T) initially decreases upon entering the superconducting state (T \u0026lt; Tc), followed by a significant increase at lower temperatures, surpassing the normal-state value. This behavior is attributed to nodal quasiparticle transport in the d-wave superconductor—since the (103) orientation exposes the ab-plane of YBCO at the interface, nodal quasiparticles become the dominant channel for spin transport. In contrast, the c-axis-oriented heterojunction exhibits a distinctly different phenomenon: α(T) sharply increases below Tc, peaks at approximately 0.65–0.7Tc, and subsequently decays. This anomalous enhancement is interpreted as arising from interfacial bound Andreev states, which result from the local suppression of the superconducting order parameter induced by the proximity effect of LSMO. This study reveals the orientation dependence of the spin transport mechanism at the d-wave superconductor/half-metallic interface: nodal quasiparticles dominate in the (103) orientation, while Andreev bound states are dominant in the c-axis orientation. These findings provide important experimental evidence for understanding the interplay between spin dynamics and superconductivity in superconductor/ferromagnet heterojunctions.\n4. Superconductivity Reinforces Charge-Density-Wave Phase Coherence across Cuprates Relevance Score: 4.2149 Authors: H. Lee, C. -T. Kuo, M. Fujita, C. -C. Kao, J. -S. Lee Link: http://arxiv.org/abs/2605.11401v1 Summary: Conventional views hold that high-temperature superconductivity (SC) competes with charge density waves (CDW) by suppressing their amplitude and spatial extent. However, using resonant soft X-ray scattering (RSXS) combined with a coherence-sensitive analysis of the momentum profile, this study reveals that in La₁.₈₈₅Sr₀.₁₁₅CuO₄ (LSCO) single crystals, the full width at half maximum of the CDW peak decreases by approximately 21% in the superconducting state, accompanied by nearly complete wavevector locking, exhibiting BCS-like enhancement of phase coherence. By separating the contributions from domain size effects and intrinsic phase coherence, the study confirms that below the superconducting transition temperature, CDW phase coherence increases by about 30%, while the CDW volume fraction decreases by approximately 15%. Even after the introduction of strong disorder through five years of crystal aging (resulting in a 60% reduction in CDW volume), the SC-induced enhancement of phase coherence persists. Furthermore, by compiling published scattering data from Bi-, Hg-, Y-, and Nd-based cuprates, a nearly universal temperature dependence of the CDW peak width emerges, indicating that SC-enhanced CDW phase coherence is a common feature of the cuprate family. These results reveal a dual relationship between superconductivity and CDW: on one hand, they compete in amplitude; on the other hand, they cooperate through enhanced phase coherence. This finding extends the SC-CDW interaction from a purely competitive paradigm to one that includes mutual reinforcement at the phase level, offering new insights into the entanglement of multiple ordered states in cuprates, and suggesting that superconductivity may modulate CDW phase stiffness by reshaping low-energy responses and coupling to the lattice.\n5. Nematicity in LaFeAsO single crystals studied by elastoresistance, high-resolution thermal expansion and shear-modulus measurements Relevance Score: 4.1743 Authors: X. C. Hong, S. Sauerland, L. Wang, F. Scaravaggi, A. U. B. Wolter, R. Kappenberger, S. Aswartham, S. Wurmehl, S. Sykora, F. Caglieris, B. Büchner, C. Hess, R. Klingeler Link: http://arxiv.org/abs/2605.11955v1 Summary: Nematicity in LaFeAsO single crystals was investigated through high-resolution thermal expansion, shear modulus, and elastoresistance measurements. The shear modulus C66 was observed to soften near the structural phase transition temperature Ts, and both the nematic susceptibility χ_sh derived from the shear modulus and χ_er derived from elastoresistance exhibit Curie-Weiss-type divergence with temperature, providing evidence for an electronic origin of nematicity. The characteristic coupling energy between lattice and electronic degrees of freedom is approximately 30 K. Comparison with BaFe₂As₂ single crystals reveals that the temperature dependence of the shear modulus is very similar in the two materials, yet the behavior of χ_er is distinctly different: in BaFe₂As₂, χ_er diverges in the same manner as the decoupled nematic susceptibility derived from shear modulus data, consistent with Landau theory expectations; whereas in LaFeAsO, a significant difference in the Weiss temperatures of χ_er and χ_sh is observed, contradicting the common theoretical framework for resistivity anisotropy and electronic nematicity in iron-based superconductors. This study indicates that the nematicity in LaFeAsO has an electronic origin, but the discrepancy between the nematic susceptibilities extracted via different experimental methods reveals differences in the details of electron-lattice coupling compared to BaFe₂As₂, likely arising from distinct order-parameter coupling mechanisms in the two classes of systems.\n6. Phase-slip residual-order spin state in FeSe Relevance Score: 4.1372 Authors: Zhixin Liu, Jiyu Fan, Lei Zhang, Ma Chunlan, Yanda Ji, Zhongqin Yang, Yan Zhu Affiliations: Nanjing University of Aeronautics and Astronautics, Fudan University, Suzhou University of Science and Technology, Chinese Academy of Sciences Link: http://arxiv.org/abs/2605.12293v1 Summary: By combining PBE and r2SCAN hybrid exchange-correlation calculations with spectral-weighted simulations of the static spin structure factor S(q), this work reveals that the magnetic ground state of FeSe is not dominated by a single magnetic configuration but rather by a manifold of nearly degenerate phase slip defects embedded within a stripe antiferromagnetic background. The authors term this state a residual order spin state (ROSS): it preserves local stripe-like antiferromagnetic correlations but loses long-range phase coherence due to phase slips. Multiple slip configurations are compressed within an extremely narrow energy window of approximately 2 meV/Fe, comparable to the low-temperature soft spin gap of FeSe. Nonlocal magnetoelastic coupling redistributes the domain-wall formation energy through the lattice, significantly reducing its effective energy cost, while competing magnetic interactions truncate the real-space coherence length at an optimal scale of about ten magnetic moments. Based on density functional theory energy evaluations, the weighted superposition of structure factors from different slip configurations successfully reproduces the momentum-space lineshapes (including peak positions, linewidths, and relative spectral weight distributions) of both stripe-type and Néel-type spin fluctuations observed in inelastic neutron scattering experiments, thereby providing a microscopic real-space foundation for spin-fluctuation-based superconducting pairing models. This work demonstrates that the magnetic ground state of FeSe should be understood as a residual order spin state renormalized by quantum dynamical mixtures of slip defects, where the spectral weight in the Néel channel originates from short-range Néel segments generated by phase slip fluctuations in the stripe background, without requiring long-range Néel order.\n7. Discovery of a nonsymmorphic superconductor with spontaneous rotational symmetry breaking and nontrivial zero modes Relevance Score: 3.9938 Authors: Hui Guo, Zhixuan Li, Senhao Lv, Tianqi Gao, Zihao Huang, Kuanrong Hao, Lizhi Zhang, Ke Zhu, Siyu Li, Xianghe Han, Xiao Lin, Shengshan Qin, Wu Zhou, Haitao Yang, Hui Chen, Hong-Jun Gao Affiliations: Chinese Academy of Sciences, University of Chinese Academy of Sciences, Beijing Institute of Technology Link: http://arxiv.org/abs/2605.11395v1 Summary: This study reveals that the asymmetric superconductor PtPb₄ serves as a robust platform featuring spontaneous rotational symmetry breaking and nontrivial zero-energy modes. PtPb₄ crystals possess a frustrated Shastry-Sutherland lattice and an asymmetric space group, with electronic structures exhibiting strong topological properties. In-plane and out-of-plane resistivity measurements clearly show twofold symmetry (C₂) in both the superconducting state and upper critical field, indicating that superconductivity breaks the original fourfold rotational symmetry of the lattice. Scanning tunneling microscopy/spectroscopy further reveals twofold symmetric magnetic vortices, providing direct real-space evidence of rotational symmetry breaking. Notably, a robust zero-energy bound state is observed at the vortex core, which does not exhibit spatial splitting over extended distances, with behavior consistent with Majorana bound states. These results confirm PtPb₄ as a novel topological superconductor, offering an ideal platform for investigating topological superconductivity and superconducting quantum devices.\n8. First-principles real-space embedding theory of the superconducting proximity effect Relevance Score: 3.9804 Authors: Nicolas Baù, Mitra Dowlatabadi, Tommaso Chiarotti, Massimo Capone, Antimo Marrazzo Link: http://arxiv.org/abs/2605.11211v1 Summary: This paper proposes a Green\u0026rsquo;s function theoretical framework based on real-space dynamical embedding for first-principles simulations of the superconducting proximity effect in mesoscopic systems. Methodologically, the influence of the superconductor on the normal material is encoded into two dynamical local self-energies (embedding potentials)—the normal and anomalous types—and the proximity effect is diagrammatically described within the Dyson equation, thereby separating and quantifying different renormalization mechanisms arising from the coupling to the superconducting bath. Combined with a recursive scheme, this framework enables the calculation of local spectral functions and proximity lengths extending to hundreds of nanometers without simulating thick interface slabs. In terms of applications, the authors first validate the method using tight-binding models (the Qi-Hughes-Zhang and Fu-Kane-Mele models), analyzing the mixed-parity superconducting state induced by the proximity of a topological insulator to an s-wave superconductor. Subsequently, based on density functional theory and maximally localized Wannier functions, first-principles simulations are performed for NbSe₂/CrBr₃ van der Waals heterostructures, with results directly comparable to scanning tunneling spectroscopy experiments. The conclusions indicate that this work provides a scalable and conceptually unified framework that successfully bridges microscopic electronic structure and mesoscopic proximity physics, enabling predictive atomic-scale simulations of superconducting interfaces and filling a gap in the first-principles description of the proximity effect at realistic interfaces, which was previously hindered by excessive computational cost.\n9. Theory and Discovery of Electrides Relevance Score: 3.7200 Authors: Chengcheng Xiao, Nicholas Bristowe, Arash A. Mostofi Link: http://arxiv.org/abs/2605.11724v1 Summary: This paper proposes a theoretical framework based on multicenter bonding to explain the origin of electron localization at interstitial lattice sites in electrides. The study reveals that interstitial electronic states are essentially multicenter bonding orbitals formed by linear combinations of surrounding atomic orbitals, and their degree of localization depends on the ratio of the interstitial size to the atomic orbital radius. By analyzing typical electrides (such as layered Ca₂N and high-pressure hP4-Na), it is verified that this theory can successfully describe their electron localization behavior. Based on this theory, the authors developed a high-throughput screening descriptor: first, topological analysis of the electron localization function (ELF) is used to identify multicenter bonding sites in interstices; then, Bader charge integration is combined to quantify orbital occupancy; finally, an electride figure of merit (FOM) is constructed to evaluate the electride character of materials. After automated screening of approximately 52,000 crystal structures in the Materials Project database, about 10,000 candidates with interstitial ELF local maxima were obtained. Among them, most known electrides (such as Ca₂N, Y₅Si₃, etc.) exhibit high FOM values, while conventional non-electrides have no or extremely low FOM. Furthermore, this theory can be extended to high-pressure electrides and organic electrides, and provides new insights into understanding F-center defects and solvated electrons. This study provides systematic theoretical guidance for the rational design and experimental verification of electrides.\n10. $H$-linear magnetoresistance in NbSe$_2$ due to impeded cyclotron motion Relevance Score: 3.6038 Authors: A. Kool, D. Pizzirani, P. Tinnemans, S. Wiedmann, F. Flicker, J. van Wezel, N. E. Hussey, R. D. H. Hinlopen Affiliations: University of Bristol, Radboud University, University of Amsterdam Link: http://arxiv.org/abs/2605.12048v1 Summary: This study systematically investigates the linear magnetoresistance (LMR) in the prototypical charge density wave (CDW) compound 2H-NbSe₂ through a combination of experiments and theory. The research methods include magnetotransport measurements on five single-crystal samples with varying degrees of disorder (residual resistivity varying by a factor of four), conducted over a temperature range of 0.35–50 K and under magnetic fields up to 30 T. Additionally, quantitative simulations are performed using the Boltzmann transport model of interrupted cyclotron motion (ICM) based on the known ARPES Fermi surface. The experiments reveal that within the CDW phase (below 15 K), the magnetoresistance of NbSe₂ transitions from a quadratic field dependence at low fields to an H-linear behavior at high fields, with a temperature-independent linear slope (approximately 0.18 μΩcm/T) that remains stable across a fourfold variation in disorder. This LMR obeys Kohler scaling, and no quantum oscillations are observed in any sample even at the highest fields. Theoretical simulations show excellent qualitative and quantitative agreement with the experimental data. The study reveals that the origin of ICM lies in strong scattering \u0026ldquo;hot spots\u0026rdquo; formed by the connection of high-temperature Fermi cylinders through the CDW order, which severely impede the cyclotron motion of quasiparticles, leading to the transition from H² to H-linear magnetoresistance. This also explains the long-standing absence of quantum oscillations in the CDW state. These results provide strong evidence that ICM is a universal mechanism for LMR in certain correlated metals.\n11. Mechanical detection of sub-band mobilities of two-dimensional electron gas on reduced SrTiO$_3$(001) surface Relevance Score: 3.5818 Authors: Akash Gupta, Marcin Kisiel, Remy Pawlak, Ernst Meyer Affiliations: University of Basel Link: http://arxiv.org/abs/2605.12101v1 Summary: This study investigates the force and dissipation responses between a mechanical oscillator and the two-dimensional electron gas (2DEG) on a reduced SrTiO₃(001) surface by combining low-temperature atomic force microscopy (AFM) with scanning tunneling spectroscopy (STS). Scanning tunneling experiments reveal Rydberg-like image potential states, confirming the formation of the 2DEG; the dissipation spectra exhibit bias-dependent peaks associated with local electrostatic gating and charge redistribution within the energy subbands of the 2DEG. These features are quantitatively interpreted through the changes in quantum capacitance as the carrier density is modulated by electric fields. Under an applied perpendicular magnetic field, the dissipation peaks follow Kohler’s rule, enabling the extraction of carrier mobility in each subband. This study establishes a non-invasive AFM-based method for quantifying energy loss in quantum oxides, offering new insights into charge dynamics relevant to spintronics.\n12. Geometry-enabled magnetic resilience in superconducting nanowire single-photon detectors Relevance Score: 3.5703 Authors: Marinus C. van der Maas, Lin Jin, Ilhan Tunç, Raymond Vermeulen, Henri Ervasti, Ravi Gopie, Jan Riegelmeyer, Marco Colangelo, Ryoichi Ishihara, Carlos Errando-Herranz Affiliations: Northeastern University, Delft University of Technology Link: http://arxiv.org/abs/2605.10968v1 Summary: This paper systematically investigates the performance changes of NbTiN superconducting nanowire single-photon detectors (SNSPDs) under an applied magnetic field. Experimental results reveal that the magnetic field enhances the intrinsic detection efficiency (IDE) at low bias currents while suppressing it at high bias currents. This enhancement-suppression transition (EST) effect narrows or even eliminates the saturation plateau of the device, thereby degrading detection efficiency. By systematically varying the nanowire width (65 nm to 135 nm) and thickness (6 nm to 10 nm), and employing photon irradiation at different wavelengths (e.g., 520 nm), the authors find that the magnitude of the EST effect strongly depends on the nanowire width: narrow nanowires (e.g., 65 nm) exhibit nearly unaffected IDE under the magnetic field, whereas wide nanowires (e.g., 135 nm) show significant performance degradation. Both simulations and experiments indicate that the non-uniform distribution of screening current induced by the magnetic field within the nanowire is the root cause of the EST effect, and narrow nanowires, due to smaller differences in current density, effectively suppress this effect. Based on this, the authors demonstrate that width-optimized SNSPDs can achieve saturated near-100% IDE over a broad photon energy range even under an applied magnetic field (23 mT). This work establishes that geometrical design—particularly nanowire width—can significantly enhance the magnetic robustness of SNSPDs, paving the way for their application in magnetic field environments such as spin quantum processors, atomic quantum processors, high-sensitivity magnetometers, and quantum transduction.\n13. Contrasting structural reversibility and magnetic correlations in isostructural honeycomb magnets CrCl$_3$ and $α$-RuCl$_3$ Relevance Score: 3.5519 Authors: Zachary Morgan, Iris Ye, Jiasen Guo, Michael A McGuire, Jiaqiang Yan Affiliations: Next Generation Pathway to Computing Program Participant, Oak Ridge National Laboratory Link: http://arxiv.org/abs/2605.11106v1 Summary: This paper presents a comparative study of the structure and magnetism of layered honeycomb halides CrCl₃ and α-RuCl₃ via neutron single-crystal diffraction. Both compounds undergo a first-order structural phase transition from high-temperature C2/m to low-temperature R3, with a step-like change in the c-axis lattice. However, the in-plane lattice response is distinctly different: α-RuCl₃ exhibits a hysteretic abrupt change at the phase transition, accompanied by gradual crystal degradation upon thermal cycling, while CrCl₃ shows a smooth in-plane lattice evolution and excellent structural stability. In terms of magnetism, CrCl₃ exhibits A-type antiferromagnetic order (ferromagnetic intra-layer, antiferromagnetic inter-layer) at TN = 14 K, with significant magnetic diffuse scattering persisting up to approximately 40 K, indicating the existence of short-range spin correlations; whereas, for α-RuCl₃, no detectable magnetic diffuse scattering is observed above the zigzag antiferromagnetic ordering temperature of TN = 7.6 K. These comparative results indicate that the differences in structural and magnetic behavior between the two compounds arise from the interplay between interlayer sliding energetics and their distinct electronic configurations (isotropic Heisenberg exchange of Cr³⁺ 3d³, and anisotropic bond-dependent exchange from spin-orbit coupling in Ru³⁺).\n14. Euler Topology in Superconducting Honeycomb Lattices Relevance Score: 3.5500 Authors: Rasoul Ghadimi, Chiranjit Mondal, Bohm-Jung Yang Link: http://arxiv.org/abs/2605.11587v1 Summary: In systems with space-time inversion symmetry, electronic energy bands can host nontrivial Euler topology. This paper investigates the band topology of a superconducting honeycomb lattice with such symmetries, demonstrating that s-wave spin-singlet (SWSS) and f-wave spin-triplet (FWST) superconducting pairings give rise to valley Euler superconductors and Euler superconductors, respectively. By analyzing the Bogoliubov-de Gennes Hamiltonian and computing Euler-class topological invariants, we find that the Euler topology in both pairing states leads to mirror symmetry-protected helical domain wall modes. Further studies reveal that introducing anisotropic hopping in the FWST state causes the Euler topology to induce a non-Abelian braiding process of Dirac nodes in momentum space. This work suggests that superconducting electronic instabilities provide a natural route to realizing nontrivial Euler band topology in Dirac materials, offering new insights for experimental realization of related topological states.\n15. The Meissner effect does not require radial charge flow Relevance Score: 3.4718 Authors: A. V. Nikulov Link: http://arxiv.org/abs/2605.10945v1 Summary: This paper points out that the Meissner effect (the complete expulsion of magnetic flux from a superconductor) does not require radial charge flow, a phenomenon that has been fully explained by experiments and conventional superconductivity theories. Traditional theories, such as Ginzburg-Landau theory and BCS theory, hold that the emergence of persistent currents originates from the quantization of the orbital angular momentum of Cooper pairs, which serves as direct experimental evidence of macroscopic quantum phenomena. The article refutes Jorge Hirsch’s “hole superconductivity theory,” which claims that persistent currents arise from the Lorentz force acting on radial charge flow and uses this to explain the Meissner effect. The authors emphasize that angular momentum quantization is not only a theoretical assumption but also an experimental fact: in a hole-free cylinder, the angular momentum in the Meissner state is zero; in a cylinder with a hole or a ring, flux quantization is observed, and the angular momentum is an integer multiple of Planck’s constant. These phenomena cannot be explained by the Lorentz force. The article also analyzes the conflict between macroscopic quantum phenomena and the correspondence principle: although the energy level spacing of single particles approaches zero as the size increases, the collective behavior of a large number of Cooper pairs in a superconducting condensate (which cannot move independently) causes the energy level spacing to increase with volume, making quantization observable at the macroscopic scale. Therefore, the essence of the Meissner effect is angular momentum quantization, and no radial charge flow is required. The conclusion calls for a critical attitude toward both conventional and alternative theories.\n16. Unbiased large-$N$ approach to competing vestigial orders of density-wave and superconducting instabilities Relevance Score: 3.4400 Authors: Grgur Palle, Rafael M. Fernandes Affiliations: University of Illinois Urbana-Champaign Link: http://arxiv.org/abs/2605.11281v1 Summary: This paper proposes an unbiased large-N method to address the inherent ambiguity in the standard large-N method when studying vestigial orders. When the standard large-N method deals with composite order parameters in the Ginzburg-Landau action, redundant relations such as Fierz identities exist among different vestigial channels, leading to non-unique decoupling schemes that may artificially enhance or suppress certain vestigial instabilities. The author demonstrates that this ambiguity is a direct consequence of redundant relations, reflecting mutual interference among different vestigial channels that cannot be treated separately. To resolve this issue, the proposed unbiased large-N method simultaneously respects both the redundant relations and the underlying symmetry group structure, yielding unique values for the effective interactions in all vestigial channels. Using this method, it is found that there exist widespread regions in the parameter space of quartic Landau coefficients where no vestigial order is stable—contrary to the conclusions of the standard large-N method but consistent with weak-coupling and variational approaches. The author illustrates the application of this method with examples of charge density waves, spin density waves, and multicomponent superconductors in tetragonal, hexagonal, and cubic systems, revealing exotic vestigial phases such as spin quadrupoles, charge-4e superconductivity, and altermagnetic order. This work provides a unified and unambiguous theoretical framework for studying vestigial orders driven by fluctuations of multicomponent order parameters.\n17. Emergent Vortex Ordering in a Multiflavor Pyrochlore-Lattice Compound GeCo$_2$O$_4$ Relevance Score: 3.4367 Authors: Jiajun Mo, Otkur Omar, Shuangkui Guang, Kazuki Iida, Kazuya Kamazawa, Fabio Orlandi, Wenyun Yang, Xiaobai Ma, Xiquan Zheng, Yingying Peng, Yuan Xiao, Shunhong Zhang, Oksana Zaharko, Xuefeng Sun, Shang Gao Link: http://arxiv.org/abs/2605.12042v1 Summary: By combining comprehensive neutron scattering experiments with a regularization regression framework, this study experimentally confirms an emergent vortex lattice order in the frustrated pyrochlore lattice compound GeCo2O4. The research reveals a significant Kitaev interaction between nearest-neighbor Co²⁺ pseudo-spins, where this anisotropic coupling, in concert with geometric frustration, stabilizes a double-Q vortex lattice ground state. To precisely determine the Hamiltonian, a regularization regression technique based on effective parameter counting is employed. Through Pareto frontier analysis, a minimal model containing seven parameters is identified from anisotropic models, in which the Kitaev coupling strengths (for first and third nearest neighbors) are both significant and robust. This model successfully reproduces the diffuse scattering patterns in the paramagnetic region as well as the spin-wave spectra in the ordered state. Furthermore, field-dependent neutron diffraction experiments, with the magnetic field applied along the [111] direction, observe the intensity evolution of different propagation vector arms, confirming the double-Q vortex order rather than the previously assumed single-Q collinear order. This discovery unveils an unexpected route to realizing a vortex lattice in three-dimensional Kitaev frustrated magnets and demonstrates a regularization protocol for Hamiltonian determination in frustrated quantum materials.\n18. Universality of magnetic susceptibility in the conical state of kagome ferromagnet Fe$_3$Sn$_2$ Relevance Score: 3.3904 Authors: Lilian Prodan, Donald M. Evans, Lukas Puntigam, 1 István Kézsmárki, Vladimir Tsurkan Link: http://arxiv.org/abs/2605.11851v1 Summary: This study reports the universal behavior of differential magnetic susceptibility (DMS) in the conical phase of the Kagome ferromagnet Fe₃Sn₂. Within the temperature range of the spin reorientation (SR) transition (60–90 K), the DMS isotherms at different temperatures exhibit an extremely narrow crossing region, forming an isosbestic point. Through analysis of the isosbestic invariance, it is found that all isotherms can collapse onto a single temperature-independent curve, revealing a quadratic temperature correction to the magnetic susceptibility. As a complement, real-space imaging of the sample under varying magnetic fields was performed using magnetic force microscopy (MFM). The evolution of spin textures from stripe domains at low fields to isolated bubble domains near the isosbestic field (approximately 0.6 T) was observed—a phenomenon not previously reported in the conical phase of bulk Fe₃Sn₂. These findings indicate that the emergence of complex magnetic textures near the isosbestic point arises from the competition among magnetocrystalline anisotropy, dipolar interactions, and the external magnetic field, representing a universal mechanism. This work not only provides new insights into the spin reorientation phenomena in Kagome magnets but also identifies the crossing point and universal behavior of DMS as characteristic fingerprints of the conical phase. Moreover, it proposes a general route to stabilize nontrivial magnetic textures in centrosymmetric magnets through anisotropic competition.\n19. Magnon polaritons in a van der Waals ferromagnet coupled to a superconducting resonator Relevance Score: 3.3738 Authors: Alvaro Bermejillo-Seco, Luuk J. van der Goot, Matteo Arfini, Yaroslav M. Blanter, Gary A. Steele, Herre S. J. van der Zant Affiliations: Delft University of Technology Link: http://arxiv.org/abs/2605.12298v1 Summary: This study utilizes low-impedance superconducting lumped-element resonators to couple microwave cavity photons with magnons in the van der Waals ferromagnet Cr₂Ge₂Te₆ (CGT), successfully achieving magnon-photon hybridization in exfoliated flakes as thin as 30 nanometers. By designing resonators with a small mode volume, the microwave magnetic field is concentrated in the inductive region, maximizing spatial overlap with the spin ensemble and thereby enhancing the coupling strength. Clear avoided level crossings observed in six devices confirm the formation of hybridized excitations (magnon polaritons). The experimentally measured coupling strength scales with the square root of the flake thickness, consistent with theoretical predictions; extrapolation indicates that hybridization could be achieved even at the monolayer limit (approximately 0.7 nm) by further reducing magnon losses and achieving large-area monolayer fabrication. The study also reveals that the current devices exhibit a relatively large magnon linewidth (approximately 500 MHz), partly due to oxidation of CGT in air and the coexistence of multiple modes. This work represents a key step toward integrating two-dimensional van der Waals magnets into superconducting quantum circuits and provides a microwave probe for investigating magnon spectra and damping in the two-dimensional limit.\n20. Magnetism and spin dynamics of Na\\textsubscript{5}Yb(MoO\\textsubscript{4})\\textsubscript{4}: A weakly interacting rare-earth stretched diamond lattice Relevance Score: 3.3430 Authors: N. Rajeesh Kumar, J. Khatua, Changhyun Koo, Izumi Umegaki, C. -E. Yin, C. -W. Wang, A. M. Strydom, H. -T. Jeng, Kwang-Yong Choi, R. Sankar, W. -T. Chen Affiliations: University of Johannesburg, National Science and Technology Council, Academia Sinica, National Tsing Hua University, National Synchrotron Radiation Research Center, Sungkyunkwan University, National Taiwan University, KEK Link: http://arxiv.org/abs/2605.12045v1 Summary: A comprehensive study of the structure and magnetism of Na5Yb(MoO4)4 is presented. This compound belongs to the family of diamond magnet lattices under tensile strain. Neutron powder diffraction at 3.3 K confirms that it crystallizes in the tetragonal space group I4₁/a, with a minimum Yb–Yb distance of 6.33 Å, forming a three-dimensional diamond framework under tension. Magnetic susceptibility and specific heat measurements indicate no long-range magnetic order down to 60 mK. The low-temperature magnetic behavior is dominated by an effective J_eff = 1/2 Kramers doublet ground state, originating from the distorted dodecahedral oxygen coordination of Yb³⁺, which is well separated from the excited crystal-field levels. Density functional theory calculations within the DFT+U framework reveal negligible exchange interactions between Yb ions, consistent with long-range O–Mo–O super-superexchange pathways. The temperature dependence of the specific heat exhibits gapped spin excitations, likely arising from long-range dipolar correlations influenced by weak exchange and strong single-ion anisotropy of the Yb moments. Muon spin relaxation measurements reveal persistent low-energy spin dynamics, indicating that dipolar correlations remain dynamic and insufficient to stabilize static magnetic order below 50 mK. These results identify Na5Yb(MoO4)4 as a rare instance of a dipolar quantum paramagnet, where single-ion physics and long-range dipolar interactions dominate, while exchange interactions are suppressed down to the millikelvin energy scale.\n","permalink":"https://nickelates.uk/en/posts/2026-05-14-arxiv-daily/","summary":"\u003cblockquote\u003e\n\u003cp\u003e\u003cstrong\u003eDaily Overview\u003c/strong\u003e:\nToday\u0026rsquo;s rapid overview of the nickelate superconductor field focuses on an important review work. A collaborative team from Nankai University and Zhejiang University has systematically summarized the experimental progress of superconducting bilayer nickelate thin films (RA₃Ni₂O₇) under ambient pressure. The review points out that La₃Ni₂O₇ and (La,Pr)₃Ni₂O₇ thin films grown on substrates such as SrLaAlO₄ via epitaxial strain have achieved superconducting onset temperatures exceeding 40 K, successfully reproducing the key structural features of high-pressure bulk materials under ambient conditions. However, the maximum superconducting transition temperature in current thin films remains lower than that of high-pressure bulk materials, indicating room for optimization. The article discusses synthesis methods, oxygen stoichiometry control, substrate-induced strain, normal-state transport behavior, and doping phase diagrams, while identifying several unresolved key issues, including the reproducibility of phase-pure ultrathin films, the microscopic origin of the two-step superconducting transition, the roles of oxygen defects and substrate doping, the Fermi surface crossing position of the Ni 3d(_{z^2}) (\\gamma) band, and the pairing symmetry. This work provides a controllable platform for understanding the microscopic mechanism of nickel-based superconductivity and clarifies the direction for future establishment of quantitative relationships among crystal structure, orbital reconstruction, and superconductivity. Only this one paper is featured today, but its content encompasses the latest experimental landscape and core challenges in the field.\u003c/p\u003e","title":"arXiv Daily: Nickelate superconductors 2026-05-14"},{"content":" Daily Overview: Dear readers! Today marks an important theoretical advancement in the field of nickel-based superconductivity. Paper [1] systematically reveals the orbital-selective Fermi surface reconstruction driven by electronic correlations in the bilayer nickel oxide La₃Ni₂O₇, using cluster perturbation theory and density matrix renormalization group methods: under weak coupling, superconductivity is dominated by interlayer spin-singlet pairing from the d_{z²} orbital, while under strong coupling it transitions to dominance by the d_{x²-y²} orbital, yet always maintaining an s± pairing structure. This discovery elucidates the mechanism connecting the disappearance of the γ pocket with superconductivity, providing a key microscopic picture for understanding the origin of high-temperature superconductivity in this system. \u0026gt; Additionally, Paper [3] focuses on rare-earth nickelates RNiO₃, proposing a multi-orbital model that uniformly describes charge, spin, orbital, and lattice degrees of freedom, predicting a nonmagnetic charge-orbital ordered insulating phase induced by the Jahn-Teller effect. This provides a theoretical basis for explaining the anomalous experimental phenomenon where the metal-insulator transition temperature is higher than the magnetic ordering temperature in small-bandwidth systems. \u0026gt; This issue also includes other cutting-edge works in superconductivity and condensed matter physics, such as the transverse magnetic response of orbital-polarized Cooper pairs in elemental superconductors, the origin of apparent double Tc in anisotropic phase models, Ginzburg-Landau theory for confined superconducting thin films, and long-range magnetic coupling mediated by superconductivity, for your reference.\n1. Correlation-Driven Orbital-Selective Fermiology and Superconductivity in the Bilayer Nickelate La$_3$Ni$_2$O$_7$ Relevance Score: 5.3646 Authors: Yong-Yue Zong, Shun-Li Yu, Jian-Xin Li Link: http://arxiv.org/abs/2605.10101v1 Summary: Based on the time-dependent variational principle (TDVP) cluster perturbation theory (CPT) and large-scale density matrix renormalization group (DMRG) methods, we systematically investigate the two-orbital Hubbard model of the bilayer nickelate La$_3$Ni$_2$O$_7$. TDVP-CPT calculations (with cluster sizes up to 16 physical sites) reveal significant orbital-selective low-energy spectral reconstruction driven by electronic correlations: the spectral weight of the $d_{z^2}$ orbital is progressively depleted, the corresponding $\\gamma$ band sinks below the Fermi level, pseudogaps open on the $\\alpha$ and $\\beta$ bands, and the remaining states in the strong-coupling regime exhibit a Fermi arc dominated by the $d_{x^2-y^2}$ orbital. DMRG calculations (on a lattice of width 8 and length 40) show that the dominant superconducting pairing correlations evolve consistently with the Fermi surface reconstruction: from weak-coupling interlayer spin-singlet pairing dominated by the $d_{z^2}$ orbital to strong-coupling pairing dominated by the $d_{x^2-y^2}$ orbital, while retaining the $s_{\\pm}$ pairing structure throughout. Further analysis indicates that in the weak-coupling regime, interorbital hybridization plays a more critical role than Hund coupling in extending the superconducting coherence length; in the strong-coupling regime, the localization induced by electronic correlations establishes a stable interlayer antiferromagnetic exchange background, driving superconductivity jointly via Hund coupling and interorbital hybridization. Therefore, the disappearance of the $\\gamma$ pocket is not detrimental to superconductivity but instead signals a correlation-driven change in the pairing channel, mediated by interlayer antiferromagnetism, Hund coupling, and interorbital hybridization.\n2. Transverse Magnetic Response from Orbitally Polarized Cooper Pairs in Elemental Superconductors Relevance Score: 4.6049 Authors: Gabor Csire, Maria Teresa Mercaldo, Balazs Ujfalussy, Carmine Ortix, Mario Cuoco Link: http://arxiv.org/abs/2605.10700v1 Summary: This paper systematically investigates the generation of orbital-polarized Cooper pairs and their magnetic response in elemental superconductors such as vanadium (V) and niobium (Nb) using superconducting density functional theory (SCDFT). The study shows that applying strain to reduce the crystal symmetry from trigonal to (C_s) symmetry, which retains only a single mirror plane, activates inter-orbital pairing in both the bulk and on the (111) surface, with a significantly enhanced surface effect. These pairs form spin-singlet, orbital-polarized Cooper pairs with equal orbital angular momentum, and the key lies in the lattice symmetry breaking that enables previously forbidden inter-orbital pairing. Under an external magnetic field, this superconducting state exhibits a novel transverse magnetic response: when the in-plane magnetic field breaks the remaining mirror symmetry, it induces a substantial orbital magnetization perpendicular to the applied field direction. Calculations demonstrate that this effect directly originates from the existence of equal-orbital-momentum Cooper pairs, serving as an experimentally detectable signature of the orbital-polarized superconducting state. The study also finds that spin-orbit coupling (SOC) is not a prerequisite but can enhance the effect; on the surface, due to additional inversion symmetry breaking, the amplitude of orbital-polarized pairing is larger. This work establishes strained elemental superconductors as the minimal material platform for realizing superconducting orbitronics, providing a clear and feasible experimental protocol for detecting orbital-polarized Cooper pairs in simple systems.\n3. Non-magnetic insulating phase induced by Jahn-Teller effect in RNiO$_3$ Relevance Score: 4.6004 Authors: Sangeeta Rajpurohit, Liang Z. Tan, Tadashi Ogitsu, Peter E. Blöchl Link: http://arxiv.org/abs/2605.09713v1 Summary: Here we propose a three-dimensional multi-orbital tight-binding model for rare-earth nickelates RNiO₃, incorporating charge, spin, orbital, and lattice degrees of freedom within a unified framework. The model parameters—including on-site interactions U and J, as well as breathing-mode electron-phonon coupling—are extracted from the small-bandwidth nickelate LuNiO₃ via hybrid functional DFT calculations. Our study reveals that the model describes three competing insulating phases determined jointly by U−3J and the breathing-mode and Jahn-Teller (JT) electron-phonon couplings: when U−3J is large, local JT distortions on high-spin Ni³⁺ sites stabilize an insulating state; when U−3J is small, the system undergoes charge disproportionation (2Ni³⁺ → Ni²⁺ + Ni⁴⁺), yielding the experimentally observed spin-polarized charge-ordered state (which emerges below the Néel temperature). More critically, when the JT energy on Ni²⁺ sites exceeds the Hund exchange 3J, a distinct charge- and orbital-ordered insulating phase appears—where two e₉ electrons occupy the same orbital but with opposite spins. Self-consistent calculations on the full three-dimensional tight-binding model further confirm the stability of this phase. This newly predicted metastable state exhibits JT distortion features characteristic of nonmagnetic charge-ordered RNiO₃, suggesting that the metal-insulator transition in RNiO₃ can occur without magnetic ordering as a trigger. This work provides a theoretical basis for explaining the experimental observation that the metal-insulator transition temperature exceeds the magnetic ordering temperature in small-bandwidth RNiO₃.\n4. Freestanding GdBa2Cu3O7 Thin Films via Optimized Buffer Layer Design: Preserving Superconducting Properties Relevance Score: 4.1176 Authors: Kazumasa Iida, Kai Walter, Takafumi Hatano, Kose Morinaga, Manuela Erbe, Hongye Gao, Satoshi Hata, Jens Hänisch Link: http://arxiv.org/abs/2605.10703v1 Summary: This study successfully fabricated freestanding GdBa₂Cu₃O₇ (GdBCO) superconducting thin films using a water-soluble Sr₃Al₂O₆ (SAO) sacrificial layer combined with thermal release tape technology. An amorphous Al₂O₃ capping layer was introduced to suppress crack formation during the peeling process. The effects of different buffer layer designs between the GdBCO and SAO layers on the structural integrity and superconducting properties were systematically investigated. Various buffer layer structures, including single-layer SrTiO₃, single-layer LaAlO₃, LaAlO₃/SrTiO₃ bilayer, and reversed SrTiO₃/LaAlO₃ bilayer, were prepared by pulsed laser deposition. The results showed that only when the buffer layer adopted the LaAlO₃/SrTiO₃ bilayer structure could the freestanding film maintain epitaxial growth, with a superconducting transition temperature (Tc) of approximately 92 K, comparable to that of the as-grown film. In contrast, both the reversed bilayer and single-layer buffer layers led to a significant reduction in Tc. X-ray diffraction and scanning transmission electron microscopy analyses confirmed that the LaAlO₃/SrTiO₃ bilayer effectively suppressed interfacial reactions and the formation of secondary phases (such as SrLaAlO₄), maintaining sharp interfaces and epitaxial orientation between layers. Magnetization measurements of the peeled films showed a clear diamagnetic response, indicating that bulk superconducting properties were preserved. This study reveals the critical role of buffer layer sequence and provides an optimization strategy for preparing high-quality freestanding REBCO films with retained superconducting characteristics.\n5. Apparent double-$T_c$ from a single BKT transition in anisotropic phase-only models Relevance Score: 3.9928 Authors: Pei-Yuan Cai, Yi Zhou Link: http://arxiv.org/abs/2605.10226v1 Summary: This work investigates the origin of direction-dependent transport extraction temperatures (i.e., apparent “dual Tc”) in two-dimensional superconductors under both equilibrium and non-equilibrium conditions by studying a minimal model of an anisotropic pure-phase Josephson junction array. Equilibrium calculations, employing Wolff cluster updates and helicity modulus analysis, reveal that the system exhibits only a single Berezinskii–Kosterlitz–Thouless (BKT) transition temperature determined by the geometric mean of directional stiffnesses; anisotropy does not split the thermodynamic phase transition. Non-equilibrium simulations, utilizing resistively shunted junction dynamics and fluctuating-twist boundary conditions, analyze the linear resistance–temperature curves under finite-size and finite-current conditions. The results show that anisotropic Josephson coupling and anisotropic dissipation reshape the R–T curve in the crossover regime, leading to two apparent transition temperatures—i.e., the apparent dual Tc—when extracted using curve-shape-based criteria such as Halperin–Nelson fitting or fixed resistance thresholds. However, critical scaling criteria (nonlinear I–V exponent α = 3 and dynamic finite-size scaling) consistently align with the single equilibrium BKT temperature and remain unaffected by crossover effects. Thus, this apparent dual Tc does not arise from thermodynamic splitting but from crossover effects induced by finite size and finite current. If robust transport temperature splitting persists in nonlinear critical scaling (as recently reported at KTaO3 interfaces), it suggests underlying physics beyond this clean anisotropic BKT baseline, potentially involving novel mechanisms such as higher-order topological defects or inhomogeneities. This work provides a clear theoretical baseline for distinguishing intrinsic thermodynamic behavior from transport artifacts.\n6. Ginzburg\u0026ndash;Landau Theory for Confined Thin-Film Superconductors Relevance Score: 3.9149 Authors: Giovanni A. Ummarino, Alessio Zaccone Link: http://arxiv.org/abs/2605.10686v1 Summary: Based on microscopic BCS free energy and the confinement theory of metallic thin films, this paper develops a Ginzburg-Landau theory applicable to quantum-confined superconducting thin films. Through analytical derivation, explicit expressions for the Ginzburg-Landau coefficients, coherence length, penetration depth, electron mean free path, and Ginzburg-Landau parameter under confined geometry are obtained. The core conclusion is that quantum confinement directly renormalizes the intrinsic superconducting coherence length by modifying the electronic density of states and Fermi level—an effect absent in traditional thin-film transport theories that consider only surface scattering. Consequently, confinement simultaneously suppresses the coherence length and enhances the penetration depth, driving the superconductor toward stronger type-II behavior as the film thickness decreases. The theory predicts a crossover regime where confinement-induced renormalization of superconducting length scales strongly couples with transport scattering effects. By comparing with experimental measurements of the penetration depth in aluminum thin films, it is found that the observed enhancement of the penetration depth arises from the interplay between confinement-induced coherence length renormalization and the suppression of the effective mean free path due to surface and disorder scattering. This work establishes a direct link between quantum confinement and electrodynamic properties of superconducting confined metallic thin films.\n7. Layer-antisymmetric pair-phase resonance at the bonding-antibonding splitting in the AA-stacked bilayer attractive Hubbard model Relevance Score: 3.8869 Authors: Yogeshwar Prasad Link: http://arxiv.org/abs/2605.10387v1 Summary: In this paper, we systematically analyze the collective excitation behavior of the layer-antisymmetric pairing phase channel in a AA-stacked bilayer honeycomb lattice attractive Hubbard model, using Gaussian fluctuation theory and Bogoliubov–de Gennes numerical calculations. We find that this channel exhibits an intra-band collective resonance pole whose frequency is exactly equal to twice the single-particle interlayer hopping energy (2t_h), i.e., the bond–antibond band splitting. Mechanism analysis reveals that at this frequency, the antisymmetric phase Pauli function degenerates point-by-point in momentum space to the static symmetric phase Pauli function, thereby linking the interlayer antisymmetric phase response to the zero-frequency symmetric phase Goldstone mode. Consequently, the resonance energy is entirely determined by single-particle hybridization, rather than by the interaction-driven Josephson coupling that governs conventional two-band superconductors. This point-to-point identity holds exactly within the Gaussian theory framework for arbitrary chemical potential; at half-filling, the full amplitude–phase coupling pole coincides with it, and it tracks closely away from half-filling. Owing to lattice inversion symmetry, this excitation is Raman forbidden and requires a probe with layer odd parity. Numerical calculations verify the accuracy of this identity. Additionally, the layer imbalance drive exhibits a finite Gaussian fluctuation overlap with the pairing phase sector, suggesting that under typical optical lattice parameters, the layer bias response in cold-atom experiments may display observable characteristic peaks at the sub-kilohertz scale.\n8. Superconductivity Mediated Long Range Magnetic Coupling Relevance Score: 3.8813 Authors: Ming Yan Wang, Yi Liu, Yao Lu Link: http://arxiv.org/abs/2605.10139v1 Summary: This study investigates the long-range magnetic interaction when a ferromagnetic insulator (FI) is placed on a Rashba spin-orbit coupled superconductor thin film. The theoretical model is based on a microscopic framework of the magnetoelectric effect: the magnetization of the FI, together with the spin-orbit coupling, generates a local anomalous current that does not satisfy the continuity equation, thereby driving a spatial modulation of the superconducting phase and forming a conserved circular supercurrent. By solving the London-Maxwell equations in static and dynamic cases, the supercurrent distribution and interaction energy are obtained. In the static case, the supercurrent-mediated interaction between FIs is ferromagnetic and decays as a power law with distance () in the far-field region, which differs from the exponentially decaying antiferromagnetic coupling found in previous studies. In the dynamic case, the precession of FI magnetization generates a time-varying effective gauge field, and the supercurrent exhibits longitudinal (due to charge accumulation) and transverse (radiation mode) components. The transverse component decays as in the far field (where is the frequency), which is slower than the static decay, indicating that the dynamic mode enables longer-distance propagation of magnetic excitations; the longitudinal component contains contributions from two different decay modes. This long-range ferromagnetic coupling mechanism is based on supercurrents rather than triplet Cooper pairs, providing a new approach for long-distance spin control in superconducting spintronics.\n9. Anomalous and diode Josephson effect in junctions with inhomogeneous ferromagnetic barrier and interfacial Rashba spin-orbit coupling Relevance Score: 3.7808 Authors: Stevan Djurdjević, Zorica Popović Link: http://arxiv.org/abs/2605.10740v1 Summary: This paper theoretically investigates the anomalous Josephson effect and Josephson diode effect in planar two-dimensional Josephson junctions with non-uniform ferromagnetic barriers and interfacial Rashba spin-orbit coupling. The exchange field within the ferromagnetic layer is arbitrarily oriented, and the superconducting electrodes can be either s-wave or arbitrarily oriented d-wave. Through a systematic symmetry analysis of the junction Hamiltonian, the minimal conditions for simultaneously breaking time-reversal and spatial inversion symmetries are identified, which are essential for the emergence of the anomalous and diode Josephson effects. Based on symmetry, the junctions are classified into three categories, with particular attention given to junctions between superconductors with d_{x^2-y^2} and d_{xy} orientations. The current-phase relation is numerically calculated using the generalized Furusaki-Tsukada method, supporting the symmetry analysis. By tuning the orientation of the exchange field in the ferromagnetic layer, the interfacial Rashba spin-orbit coupling strength, and the orientation of the superconducting order parameter, non-reciprocity can be enhanced by over 40%. Furthermore, the phase-dependent Andreev bound state energy spectrum and its contribution to charge transport are analyzed, along with its manifestations in non-reciprocal transport characteristics. By comparing the current carried by Andreev bound states with the current obtained from the F-T technique, it is found that when the Andreev bound state spectrum exhibits zero-energy crossings, or for d-wave superconducting electrodes (whose narrower superconducting gap may be suppressed), the contribution of continuum states to the current becomes significant. In the non-reciprocal regime, the Andreev bound state energy spectrum displays asymmetric profiles with respect to phase reversal, indicating a finite current at zero phase difference and unequal critical currents for forward and backward directions. These results establish symmetry criteria and microscopic mechanisms for engineering non-reciprocal Josephson transport in hybrid superconducting structures.\n10. Local supersolid in moiré modulated Bose-Hubbard model using density-matrix renormalization group method Relevance Score: 3.7298 Authors: Siyu Xie, Qiang Xu, Qianqian Shi, Wanzhou Zhang Link: http://arxiv.org/abs/2605.10238v1 Summary: Based on the density matrix renormalization group method, this paper systematically investigates the localized supersolid phase in the extended Bose-Hubbard model under one-dimensional moiré potential modulation. By imposing a soft-core boson constraint with a maximum occupation number of 2, the ground-state phase diagram of the system is numerically solved. In the absence of nearest-neighbor repulsion terms, conventional superfluid phases, localized superfluid phases, Mott insulator phases, and moiré-induced insulator phases are identified. When nearest-neighbor repulsive interactions are introduced, a novel localized supersolid phase is discovered in the regime of strong moiré potential. This phase exhibits three key features: (1) within an isolated moiré supercell, local staggered density order coexists with local off-diagonal coherence; (2) the global off-diagonal correlation function decays exponentially; (3) in the thermodynamic limit, the global structure factor approaches zero while the local structure factor remains finite. These characteristics clearly distinguish it from conventional global supersolid phases, which exhibit algebraically decaying correlations and a finite global structure factor. The results provide a complete microscopic picture of localized quantum phases in moiré lattices and offer clear observable signals for detecting localized supersolid states in ultracold atom experiments.\n11. Orbital and Spin Nernst Effects in Monolayers of Transition Metal Dichalcogenides Relevance Score: 3.6927 Authors: Saikat Saha, Arnab Bose, Sayantika Bhowal Link: http://arxiv.org/abs/2605.10033v1 Summary: This paper demonstrates that monolayer transition metal dichalcogenides (TMDCs) are excellent platforms for observing the orbital Nernst effect (ONE). The ONE refers to the phenomenon of a temperature gradient inducing a transverse orbital current. Similar to the orbital Hall effect, its existence does not rely on spin-orbit coupling (SOC). Based on an analytical analysis of the low-energy valley model, the authors reveal the crucial role of electronic states near the Fermi level in generating the ONE. When SOC is introduced, a spin Nernst effect (SNE) also arises, with its magnitude proportional to SOC and vanishing in its absence. Using a full Brillouin zone tight-binding model, calculations are performed for insulating 2H-MoS₂ and metallic 2H-NbS₂. The results show that in MoS₂, electron or hole doping can induce both ONE and SNE, whereas in metallic NbS₂, these effects are intrinsic. The study indicates that orbital and spin Berry curvatures are the core drivers of these effects, and doping is an effective means of tuning the orbital/spin Nernst response. Finally, the paper proposes feasible experimental schemes for detecting these effects in monolayer TMDCs.\n12. Thermodynamic Approach for Deciphering Magneto-Structural Phase Transitions: Proof of Concept in Heusler Alloys Relevance Score: 3.6555 Authors: Eleonora Rusconi, Lorenzo Gallo, Victor A. L\u0026rsquo;vov, Anna Kosogor, Simone Fabbrici, Giovanna Trevisi, Francesco Cugini, Massimo Solzi, Thomas Schrefl, Franca Albertini Affiliations: University of Parma, University of Vienna, University for Continuing Education Krems, National Research Council, National Academy of Sciences of Ukraine Link: http://arxiv.org/abs/2605.08920v1 Summary: This study focuses on the Ni50Mn25-xCuxGa25 (x = 6.25, 6.5, 6.75, 7) and Ni50.5Mn18.5Cu6.5Ga24.5 series of alloys. By introducing subtle compositional variations, three types of magnetostructural phase transition behaviors are identified: martensitic transformation in the ferromagnetic phase, magnetostructural transformation from paramagnetic austenite to ferromagnetic martensite, and martensitic transformation in the paramagnetic phase. The temperature dependence of magnetization M(T) and magnetic susceptibility χ(T) was experimentally measured for each alloy, and a novel thermodynamic analysis method is proposed to determine the Curie temperature and the martensitic transformation temperature. The innovation of this method lies in considering the influence of structural transformation on spin exchange parameters, thereby revealing the coupling between the structural and magnetic properties of the alloys. Theoretical analysis indicates that this coupling results in a difference of more than 50 K between the Curie temperatures of the austenite and martensite states. By calculating the characteristic temperatures corresponding to the extrema of dM/dT and χ(T), it is found that the correlation between these characteristic temperatures and the Curie temperature or martensitic transformation temperature is not direct but strongly depends on the type of transition behavior. This work provides a robust framework for extracting characteristic temperatures that cannot be directly measured from standard magnetization data, which is applicable not only to ferromagnetic Heusler systems but also generally to the analysis of other multiferroic ferromagnetic materials.\n13. Oxygen vacancies beyond the dilute limit in doped CaMnO3 perovskites and implications for screening materials in thermochemical applications Relevance Score: 3.5846 Authors: Harender S. Dhattarwal, Colin M. Hylton-Farrington, Ian G. McKendry, Christopher Abram, Richard C. Remsing Link: http://arxiv.org/abs/2605.10636v1 Summary: This study systematically investigates the variation of oxygen vacancy formation energy with vacancy concentration in cubic CaMnO₃ perovskite using first-principles density functional theory (DFT), establishing the equilibrium vacancy concentration as a physically correct reference point. The results reveal that the formation energy of a single oxygen vacancy is negative, indicating that the stoichiometric phase is not the lowest-energy reference state at high temperatures; rather, the material inherently possesses intrinsic oxygen vacancies at operational temperatures. Traditional high-throughput screening based on single-vacancy formation energies directly excludes materials with negative values, which stems from an incorrect reference state selection and may overlook promising thermochemical energy storage candidates. By calculating formation energy curves at different vacancy concentrations and validating the framework against experimental reduction enthalpies, the reliability of this approach is confirmed. Furthermore, the differentiated mechanisms of A-site (Mg, Sr) and B-site (Fe, Al) doping in modulating vacancy formation are elucidated: A-site doping primarily influences vacancy formation energy through lattice strain relaxation and symmetry breaking, resulting in uniform effects; B-site doping reshapes the local redox environment, causing strong configuration dependence of vacancy formation energy and a wide distribution range. Finally, a thermodynamic model incorporating configurational entropy is developed, enabling accurate prediction of equilibrium oxygen stoichiometry under different temperatures and oxygen partial pressures, and demonstrating that selective reduction of Mn⁴⁺ and B-site dopant ions can regulate the onset temperature of vacancy formation. These results establish a high-throughput screening framework beyond the single-vacancy paradigm, providing practical guidance for the rational design of perovskite thermochemical energy storage materials.\n14. Laser-induced demagnetization in a MAX phase (Cr0.5Mn0.5)2GaC Relevance Score: 3.4536 Authors: Iaroslav Mogunov, Artyom Gorshkov, Mikhail Rautskii, Tatyana Andryushchenko, Alexandra Kalashnikova Affiliations: Federal Research Center KSC SB RAS, Ioffe Institute Link: http://arxiv.org/abs/2605.10483v1 Summary: This study systematically investigates the ultrafast demagnetization dynamics of a 40 nm thick epitaxial film of the magnetic MAX phase (Cr0.5Mn0.5)2GaC (with a magnetic ordering temperature of approximately 250 K) under femtosecond laser pulse excitation, using time-resolved magneto-optical Kerr effect (tr-MOKE) measurements. The experimental results reveal that the demagnetization transients exhibit a typical two-step type II demagnetization behavior—a characteristic feature of two-dimensional magnetic systems. In this process, the fast demagnetization component is relatively small at low temperatures and low excitation fluences, but becomes pronounced as temperature and fluence increase; the slow demagnetization component dominates, with a characteristic time of approximately 100 ps. By fitting the experimental data with a three-temperature model, the authors extract the electron-lattice, spin-lattice, and electron-spin coupling constants. The calculated spin heat capacity shows a weak temperature dependence, which explains the absence of significant demagnetization slowdown at high temperatures and high fluences. This work reports for the first time the ultrafast demagnetization dynamics of MAX phase materials, providing a starting point for optically manipulating magnetism in this broad class of materials in experiments, and introducing the MAX phase into the field of modern two-dimensional spintronics.\n15. Fokker\u0026ndash;Planck framework for stochastic octupole moment dynamics in chiral antiferromagnet Mn3Sn Relevance Score: 3.4235 Authors: Siyuan Qian, Shaloo Rakheja Affiliations: University of Illinois Link: http://arxiv.org/abs/2605.08531v1 Summary: This study proposes a reduced stochastic framework for random octupole dynamics in the chiral antiferromagnet Mn3Sn, by combining the reduced Landau-Lifshitz-Gilbert equation with the Fokker-Planck formalism. First, the reduced model is validated to accurately capture the fundamental switching behavior of the full three-sublattice octupole dynamics. The corresponding Fokker-Planck equation is then derived, and an efficient solver is implemented using CUDA acceleration. Analysis shows that due to the extremely fast rotation of the octupole moment governed by its minimal deviation relative to the basal plane, the solver is highly sensitive to the grid resolution in the out-of-plane direction. The solver is validated against Monte Carlo simulation results, including equilibrium distributions, relaxation trajectories, and switching times, confirming its accuracy. Finally, the method is applied to the thermally assisted field-driven switching process, successfully achieving efficient computation of extremely low error probabilities, a performance practically unattainable with direct Monte Carlo simulations. This approach provides an efficient numerical framework for studying random octupole dynamics in Mn3Sn, particularly well-suited for simulating low-probability events.\n16. First-Principles Study of the Temperature Dependence of Structural, Electronic, and Hyperfine Properties of the Cu(100) Surface Relevance Score: 3.3721 Authors: Germán N. Darriba, R. Faccio, Mario Rentería Affiliations: Universidad de la República, Universidad Nacional de La Plata Link: http://arxiv.org/abs/2605.09327v1 Summary: We employed first-principles methods based on density functional theory to systematically investigate the temperature-dependent structural, electronic, and hyperfine properties of the pure Cu(100) surface. By constructing a slab supercell containing seven inequivalent atomic layers and using experimentally measured temperature-dependent lattice parameters of bulk copper, we fully relaxed the \u0026ldquo;freshly generated surface\u0026rdquo; to obtain a \u0026ldquo;reconstructed surface,\u0026rdquo; repeating this process at each temperature point to simulate the heating effect. The electric field gradient (EFG) tensor, electron density, and partial density of states for Cu atoms from the topmost surface to the bulk layers were calculated. The study reveals that after surface reconstruction, the nearest-neighbor distances of the topmost Cu1 atoms exhibit anisotropic relaxation: in-plane CuNNp distances maintain isotropic expansion consistent with the bulk, while the distances to the next layer (CuNNd) show little variation with temperature, accompanied by a slight \u0026ldquo;accordion\u0026rdquo; effect, resulting from competition between lattice thermal expansion and contraction of interlayer distances. The temperature dependence of the EFG for Cu atoms in each layer primarily originates from the \u0026ldquo;ionic\u0026rdquo; contribution, and its linear temperature behavior is directly related to surface reconstruction rather than being caused solely by surface generation. By analyzing atomic-scale electron density and partial density of states, it is confirmed that the linear temperature dependence of the surface EFG differs from the -αT^(3/2) law of the bulk EFG, and instead aligns with the linear behavior of the ionic contribution due to the linear variation of lattice parameters and anisotropic relaxation of the surface. This work provides a benchmark for pure surface effects in understanding the anomalous linear temperature dependence of the EFG for probe atoms doped on the Cu(100) surface, revealing the essential influence of surface boundary conditions on hyperfine interactions.\n17. Non-homogeneous structure of complex concentrated alloys: Effect of intrinsic strain Relevance Score: 3.3167 Authors: Vaclav Paidar, Pavel Lejcek, Andrea Skolakova Affiliations: Czech Academy of Sciences Link: http://arxiv.org/abs/2605.10182v1 Summary: This paper investigates the heterogeneous structures in three representative complex concentrated alloys (Cantor-type CrMnFeCoNi, refractory-type TiZrNbTaMo, and Cu-Ni-Ti-Zr-Hf system) through a combination of theoretical analysis and experimental observation. The study reveals that even though the atoms in these multi-component alloys occupy a common crystal lattice, their distribution is not uniform; instead, there exist local segregation regions of varying compositions. Based on atomic volume and elastic modulus, the authors calculated the deformation energy required for atoms of different sizes to achieve the average atomic volume, and analyzed the distribution of this deformation energy in different regions (such as interdendritic, intradendritic, and bright/dark regions). The results indicate that the formation of local segregation regions can effectively reduce the overall energy of the system through mutual compensation of tensile and compressive strain fields generated by atoms of different sizes. For example, in the transition metal system, the deformation energies of Mn and Ni compensate each other, promoting the formation of Mn-Ni-enriched regions; in the refractory system, the large deformation energies of Mo and Zr drive the separation into two bcc structures with different lattice parameters; in the Cu-Ni-Ti-Zr-Hf system, partial compensation of deformation energies between Ni and Zr/Hf leads to elemental segregation. These cases highlight the critical role of local chemical and structural heterogeneities in determining the thermodynamic stability of multi-component alloys, providing new insights into the phase stability and mechanical behavior of such alloys.\n18. Molecular Nitrogen Formation in Nitrogen-Implanted (100) $β-Ga_2O_3$ Revealed by Temperature-Dependent $N$ $K$-edge XANES Relevance Score: 3.3071 Authors: I. N. Demchenko, Y. Syryanyy, A. Shokri, Y. Melikhov, M. Chernyshova, M. Turek, A. Droździel, F. Munnik, R. Jakieła, R. Minikayev, J. Z. Domagala, A. Derkachova, M. Zając, J. Krajczewski, E. Grzanka, Z. Galazka Affiliations: Helmholtz-Zentrum Dresden-Rossendorf, Warsaw University of Technology, Leibniz-Institut für Kristallzüchtung, Jagiellonian University, University of Warsaw, National Center for Nuclear Research, Institute of Plasma Physics and Laser Microfusion, Polish Academy of Sciences, Maria Curie-Sklodowska University Link: http://arxiv.org/abs/2605.09578v1 Summary: This study systematically elucidates the micro-configurations of nitrogen ion-implanted (100) β-Ga₂O₃ by combining temperature-dependent nitrogen K-edge X-ray absorption near-edge structure (XANES) spectroscopy with first-principles calculations and multiple scattering simulations. Experimental results reveal that all implanted samples exhibit a pronounced π* resonance feature in the XANES spectra, characteristic of molecular nitrogen (N₂). As the annealing temperature increases from 320 to 1100 °C, this resonance peak becomes progressively sharper and more intense, indicating that annealing promotes the transformation of nitrogen atoms into N₂-like configurations rather than the formation of substitutional acceptors. Calculation results confirm that the defect-rich environment induced by implantation—particularly the localized β→γ structural distortion in the near-surface layer—strongly favors the stabilization of N–N bonding configurations. The bond length (1.094 Å) of these configurations is consistent with that of free N₂ molecules, while the nitrogen at oxygen substitutional sites (N_O) fails to reproduce the experimental spectral features. This study provides a microscopic explanation for the longstanding difficulty in achieving p-type conductivity in nitrogen-doped β-Ga₂O₃: implanted nitrogen preferentially self-organizes into molecular N₂-like structures rather than forming electrically active substitutional acceptors. This finding identifies impurity molecularization as a previously overlooked key doping compensation pathway under highly non-equilibrium implantation conditions.\n19. Giant Rashba Splitting and Enhanced Nonlinear Berry-Phase Responses in Sliding-Tunable vdW MXene Heterostructures Relevance Score: 3.3005 Authors: Ali Sufyan, J. Andreas Larsson, Andreas Kreisel, Erik van Loon Affiliations: Lund University, Luleå University of Technology, LINXS Institute of advanced Neutron and X-ray Science, Uppsala University Link: http://arxiv.org/abs/2605.09674v1 Summary: This paper systematically investigates chalcogen-terminated van der Waals MXene materials M2CX2 (M = Nb, Ta; X = S, Se) and their heterostructures with the ferromagnetic insulator CrBr3 using first-principles calculations. The study reveals that monolayer MXene exhibits significant Rashba splitting (up to 2.53 eV Å) and valley-contrast spin polarization due to the lack of inversion symmetry, leading to spin-valley locking at the K/K′ points. These properties drive strong second-order nonlinear Berry phase responses: the shift current peak of pristine bilayer Ta2CS2 reaches approximately 5 Å mA/V², and the Berry curvature dipole (BCD) is significantly enhanced near the band edges, outperforming most known two-dimensional materials. In the M2CS2/CrBr3 heterostructure, the ferromagnetic substrate breaks time-reversal symmetry through proximity exchange coupling, inducing a magnetization-reversible exchange field and generating a valley-selective conduction band renormalization of about 50 meV. Crucially, the interfacial geometry (including stacking inversion and lateral sliding) serves as a mechanical tuning knob, enabling continuous modulation of the competition between the exchange field and spin-orbit coupling, as well as the band gap, thereby driving a quantum anomalous Hall phase in the bilayer system. This work demonstrates that chalcogen-terminated MXene provides an ideal platform for cooperatively tuning Rashba physics, proximity exchange, and Berry phase responses via magnetic and mechanical means.\n20. Cavity-Induced Excitonic Insulation and Non-Fermi-Liquid Behavior in Dirac Materials Relevance Score: 3.2911 Authors: Yuxuan Guo, Ashida Yuto Link: http://arxiv.org/abs/2605.10652v1 Summary: This paper investigates two-dimensional Dirac fermions embedded in a deep subwavelength cavity formed by high-impedance metasurfaces. Unlike conventional metallic boundaries, such metasurfaces support quasi-electrostatic transverse magnetic modes, which mediate long-range interactions between electrons. By combining static electronic screening with Dyson-Schwinger equation analysis, the authors find that this engineered interaction can qualitatively alter the ground-state properties of Dirac materials. When the fermion flavor number N_f is below a critical value N_c = 16/π, the interaction drives the system through an infinite-order quantum phase transition into an excitonic insulator phase, spontaneously generating a mass gap. When N_f \u0026gt; N_c, the system remains gapless but enters a non-Fermi liquid critical regime, where the quasiparticle residue is singularly suppressed to zero and the Dirac cone exhibits a non-analytic dispersion relation. Moreover, under a vertical magnetic field, cavity fluctuations can dynamically enhance the degeneracy of the zero Landau level for all N_f values. These results indicate that high-impedance metasurface cavities are a promising platform for realizing correlated Dirac matter.\n","permalink":"https://nickelates.uk/en/posts/2026-05-13-arxiv-daily/","summary":"\u003cblockquote\u003e\n\u003cp\u003e\u003cstrong\u003eDaily Overview\u003c/strong\u003e:\nDear readers! Today marks an important theoretical advancement in the field of nickel-based superconductivity. Paper [1] systematically reveals the orbital-selective Fermi surface reconstruction driven by electronic correlations in the bilayer nickel oxide La₃Ni₂O₇, using cluster perturbation theory and density matrix renormalization group methods: under weak coupling, superconductivity is dominated by interlayer spin-singlet pairing from the d_{z²} orbital, while under strong coupling it transitions to dominance by the d_{x²-y²} orbital, yet always maintaining an s± pairing structure. This discovery elucidates the mechanism connecting the disappearance of the γ pocket with superconductivity, providing a key microscopic picture for understanding the origin of high-temperature superconductivity in this system. \u0026gt; Additionally, Paper [3] focuses on rare-earth nickelates RNiO₃, proposing a multi-orbital model that uniformly describes charge, spin, orbital, and lattice degrees of freedom, predicting a nonmagnetic charge-orbital ordered insulating phase induced by the Jahn-Teller effect. This provides a theoretical basis for explaining the anomalous experimental phenomenon where the metal-insulator transition temperature is higher than the magnetic ordering temperature in small-bandwidth systems. \u0026gt; This issue also includes other cutting-edge works in superconductivity and condensed matter physics, such as the transverse magnetic response of orbital-polarized Cooper pairs in elemental superconductors, the origin of apparent double Tc in anisotropic phase models, Ginzburg-Landau theory for confined superconducting thin films, and long-range magnetic coupling mediated by superconductivity, for your reference.\u003c/p\u003e","title":"arXiv Daily: Nickelate superconductors 2026-05-13"},{"content":" Daily Overview: Although today\u0026rsquo;s daily paper overview does not directly include works related to nickelate superconductors, it covers several highlights closely tied to unconventional superconductivity, topological superconductivity, and strongly correlated electron systems, offering multidimensional perspectives for understanding superconducting pairing mechanisms and quantum state manipulation. Key highlights include: 《(BaS)₁/₃TaS₂》 achieves bulk two-dimensional Ising superconductivity with both high transition temperature and large interlayer spacing, breaking traditional trade-offs through a chain-intercalation strategy; 《d-wave altermagnets》 reveals that d-wave altermagnets can stabilize finite-temperature pair density wave phases without an external magnetic field; 《cuprate superconductivity》 uses first-principles three-band modeling to confirm the indispensability of long-range hopping for the superconducting dome and pairing symmetry in cuprates; 《twisted bilayer cuprates》 predicts topological superconducting states with Chern numbers up to ±8 under electron doping in a weakly interacting Hubbard model; 《Majorana bound states》 provides an analytical framework for Majorana modes hosted by skyrmion-vortex pairs in chiral ferromagnet-superconductor heterostructures. Additionally, the discovery of the three-dimensional bipartite quantum spin liquid candidate material KBa₃Ca₄Cu₃V₇O₂₈, and the successful decoupling of RuO₂ surface electronic states from bulk states, provide important experimental foundations for studying novel quantum states in correlated electron systems.\n1. Breaking the Trade-off: Bulk 2D Ising Superconductivity with High Tc and Giant Interlayer Spacing via a Unique Chain Intercalation in (BaS)1/3TaS2 Relevance Score: 4.3355 Authors: Ziyi Zhu, Leiming Chen, Xiangqi Liu, Haonan Wang, Chen Xu, Ze Yan, Zhengyang Li, Wei Xia, Jiawei Luo, Na Yu, Xia Wang, Ke Qu, Zhenzhong Yang, Yanfeng Guo Affiliations: ShanghaiTech University, Zhengzhou University of Aeronautics, East China Normal University Link: http://arxiv.org/abs/2605.07336v1 Summary: Through a unique chain-intercalation strategy, a novel polymorph (BaS)₁/₃TaS₂ has been successfully synthesized, featuring Ba-S-S-Ba chain structures inserted between TaS₂ bilayers. This method breaks the bulk c-axis mirror symmetry, achieving interlayer decoupling with an interlayer distance of 12.75 Å, more than three times that of pristine 2H-TaS₂. This structure suppresses interlayer electronic coupling, allowing local inversion symmetry breaking within individual TaS₂ layers to dominate, thereby preventing the compensation of the Ising spin-orbit field in centrosymmetric bulk phases and realizing robust two-dimensional Ising superconductivity. While maintaining a large interlayer spacing, the compound exhibits an enhanced superconducting transition temperature T꜀, breaking the traditional trade-off between large spacing/high anisotropy and high T꜀. Comprehensive transport, magnetic, and thermodynamic measurements confirm its robust superconducting state. This work establishes a general intercalation framework for designing bulk two-dimensional Ising superconductors, offering a new pathway to reconcile competing material demands and expanding the scope of Ising superconductivity research.\n2. Anomalous Phase-Coherence Scaling in a Quantum-Critical Dirac Semimetal Relevance Score: 3.9937 Authors: Sana Nakamichi, Ryotaro Kobara, Yoshinari Unozawa, Yoshitaka Kawasugi, Sakura Hiramoto, Koki Funatsu, Toshio Naito, Masafumi Tamura, Reizo Kato, Yutaka Nishio, Naoya Tajima Link: http://arxiv.org/abs/2605.07085v1 Summary: This paper investigates the quantum coherence behavior of weak antilocalization (WAL) in the pressurized Dirac semimetal α-(BEDT-TTF)₂I₃. Through low-temperature magnetoconductance measurements, the phase coherence length Lφ and its temperature scaling were extracted under various pressures. In the high-pressure region (\u0026gt;1.2 GPa), the system exhibits conventional dephasing behavior of two-dimensional diffusive conductors: Lφ ∝ T^(-p), with exponent p ≈ 0.5–0.55, dominated by electron-electron scattering. As the pressure decreases to near the critical pressure Pc ≈ 1.2 GPa, the temperature exponent is significantly suppressed to p ≈ 0.3, while Lφ remains large (about 700–800 nm at 0.5 K). This anomalous scaling suggests an unconventional inelastic scattering mechanism dominated by Dirac electrons near the quantum critical point. Notably, the WAL signal persists even upon entering the charge-ordered insulating phase, indicating that this quantum phase transition is massless or nearly massless, without opening a energy gap. Alternative interpretations such as phase separation or first-order phase transition are ruled out: Lφ varies continuously near the critical point and remains at the submicron scale, excluding macroscopic phase separation. Spin-orbit coupling is applicable for explaining the WAL behavior in the strong SOC limit, with the estimated spin-orbit scattering energy scale being approximately 1–3 K. These results provide transport evidence of anomalous dephasing scaling in a quantum critical Dirac system, supporting the system\u0026rsquo;s entry into a quantum critical Dirac regime dominated by correlation effects, where the scattering dynamics of Dirac fermions are strongly renormalized.\n3. Noncollinear antiferromagnetic structure and physical properties of CrRhAs with distorted kagome lattice Relevance Score: 3.8659 Authors: Chenglin Shang, Daye Xu, Bingxian Shi, Xuejuan Gui, Zhongcen Sun, Juanjuan Liu, Jinchen Wang, Hongxia Zhang, Hongliang Wang, Lijie Hao, Peng Cheng Affiliations: Renmin University of China, China Institute of Atomic Energy Link: http://arxiv.org/abs/2605.07540v1 Summary: This paper systematically investigates the magnetic structure and physical properties of the ZrNiAl-type compound CrRhAs, which features a distorted Kagome lattice, through powder X-ray diffraction, neutron diffraction, magnetic susceptibility, electrical transport, and specific heat measurements. CrRhAs undergoes an antiferromagnetic transition at TN = 149 K. Powder neutron diffraction analysis reveals a non-collinear antiferromagnetic structure with a propagation vector of k = (1/3, 1/3, 1/2), characterized by ferromagnetic second-nearest-neighbor coupling within the Kagome plane, which differs from previous predictions based on density functional theory calculations. The electrical transport properties exhibit anomalous behavior: the longitudinal resistivity shows semiconducting behavior above TN and becomes metallic below TN; the Hall coefficient undergoes two sign reversals near 70 K and 300 K, likely associated with multiband effects and strong spin fluctuations. Specific heat measurements yield a large Kadowaki-Woods ratio of α = 33.9 μΩ·cm·mol²·K²/J², indicating the presence of strong electron correlations. The comprehensive results suggest that CrRhAs is a strongly correlated Kagome metal with multiband characteristics and a non-collinear magnetic structure.\n4. Finite temperature pair density wave superconductivity in $d$-wave altermagnets Relevance Score: 3.8407 Authors: Amrutha N Madhusuthanan, Madhuparna Karmakar Link: http://arxiv.org/abs/2605.07656v1 Summary: This paper employs a non-perturbative static path approximation Monte Carlo method to investigate finite-temperature superconducting pairing in two-dimensional d-wave altermagnets. The study demonstrates that altermagnets provide a mechanism for stabilizing finite-momentum superconductivity without the need for an external magnetic field. Specifically, the d-wave altermagnet supports a robust pair density wave (PDW) phase, which persists within a finite temperature window and remains stable even in the presence of strong thermal fluctuations. The underlying mechanism originates from momentum-dependent spin splitting, which effectively enhances pairing instabilities at finite center-of-mass momentum without the application of a Zeeman field. Through analysis, the researchers identify distinct thermal scales associated with phase coherence, gap closure, and pseudogap formation, and establish characteristic spectral and real-space signatures of the PDW state. These findings reveal that altermagnets offer a robust route to realizing thermally stable finite-momentum superconductivity and provide experimentally verifiable signatures for altermagnetic materials.\n5. Beyond the conventional Emery model: crucial role of long-range hopping for cuprate superconductivity Relevance Score: 3.8285 Authors: Eric Jacob, M. O. Malcolms, Viktor Christiansson, Leonard M. Verhoff, Paul Worm, Liang Si, Philipp Hansmann, Thomas Schäfer, Karsten Held Link: http://arxiv.org/abs/2605.07739v1 Summary: This study employs the dynamical vertex approximation (DΓA) method, constructing a complete three-band CuO₂ model based on first-principles calculations (DFT+Wannier+cRPA), to systematically investigate the superconducting pairing mechanism in cuprate superconductors. The conventional Emery model includes only three hopping parameters: nearest-neighbor oxygen-copper hopping (tₚd), nearest-neighbor oxygen-oxygen hopping (tₚₚ), and next-nearest-neighbor oxygen-oxygen hopping (tₚₚ′). However, this work reveals that such a simplified model significantly underestimates effective hopping integrals, causing the van Hove singularity in the band structure to be too close to the Fermi level, thus failing to correctly describe superconducting behavior. By incorporating all long-range hopping parameters derived from DFT into the model, DΓA calculations yield a superconducting dome (hole doping from approximately 7% to 22%) consistent with experimental observations in cuprates, with the d-wave superconducting order parameter exhibiting a standard form in momentum space. In contrast, the conventional Emery model produces superconductivity only within a very narrow doping range (approximately 9% to 14%), and its d-wave order parameter shows unphysical modulation at the antinode, arising from the suppression of antinodal spectral weight by the pseudogap. This study demonstrates that long-range hopping is indispensable for quantitatively accurate descriptions of the phase diagram and pairing symmetry in cuprate superconductors, providing a more comprehensive framework for theoretical studies of superconductivity in real materials based on oxygen orbitals.\n6. Emergent Dynamic Magnetic Ground State in a Mixed 3d/5d Heavy Fermion System CaCu3Ir4O12 Relevance Score: 3.7210 Authors: J. Ming, Abhisek Bandyopadhyay, G. B. G. Stenning, M. T. F. Telling, N. N. Wang, G. Wang, J. -G. Cheng, D. T. Adroja Affiliations: Lalit Narayan Mithila University, Rutherford Appleton Laboratory, Chinese Academy of Sciences, University of Johannesburg, University of Chinese Academy of Sciences Link: http://arxiv.org/abs/2605.07602v1 Summary: Through a comprehensive and in-depth study of the mixed 3d/5d electron system CaCu₃Ir₄O₁₂, this paper reveals the nature of its ground-state magnetism. This material possesses a cubic A-site ordered quadruple perovskite structure (space group Im-3), in which the 3d localized magnetic moments of Cu²⁺ ions couple with the extended 5d network of Ir. The research team employed a combination of experimental techniques, including DC and AC magnetic susceptibility, heat capacity measurements (down to 50 mK), and zero-field and longitudinal-field muon spin relaxation (μSR) techniques (down to 40 mK), to comprehensively characterize its magnetic ground state at both macroscopic and microscopic scales. The experimental results show that despite the presence of strong antiferromagnetic interactions (with a magnetic-field-dependent Weiss temperature θ_W of approximately -200 K), no evidence of long-range magnetic order or spin freezing was detected across the entire measured temperature range (down to 40 mK). More critically, μSR measurements directly confirm that, even at the lowest temperatures, the local magnetic moments exhibit significant quantum spin fluctuations, indicating that the magnetic ground state is intrinsically dynamic rather than static. These results establish CaCu₃Ir₄O₁₂ as a three-dimensional quantum disordered magnet, providing a well-characterized and excellent platform for exploring fluctuation-dominated exotic magnetic states in strongly correlated 3d/5d oxides. This work overcomes difficulties commonly encountered in identifying such quantum disordered states in three-dimensional systems—specifically, the need to rule out chemical disorder-induced glassy behavior or weak static order—thereby strongly supporting the existence of an intrinsic dynamic magnetic ground state.\n7. Microscopic Magnetism of A(TiO)Cu4(PO4)4 (A = Ba, Pb, Sr): 31P and 63,65Cu NMR Study Relevance Score: 3.6820 Authors: Riho Rästa, Ivo Heinmaa, Joosep Link, Yusuke Kousaka, Tsuyoshi Kimura, Yoshihiko Ihara, Kenta Kimura, Raivo Stern Link: http://arxiv.org/abs/2605.07946v1 Summary: This paper systematically investigates the microscopic magnetism of the chiral square-lattice antiferromagnet Pb(TiO)Cu₄(PO₄)₄ (PbTCPO) using nuclear magnetic resonance (NMR), and compares it with the isostructural compounds BaTCPO and SrTCPO. Above the Néel temperature T_N ≈ 6.7 K, the ³¹P Knight shift is consistent with the bulk magnetic susceptibility, yielding nearly isotropic transferred hyperfine coupling constants H_hf^(010) = 6.77(3) kOe/μ_B and H_hf^(001) = 6.19(3) kOe/μ_B. Upon entering the ordered state, the ³¹P NMR spectrum splits into three lines (in contrast to four lines for BaTCPO), and the line spacing exhibits power-law behavior with the emergence of the static internal field, characterized by an exponent β ≈ 0.23, consistent with quasi-two-dimensional critical behavior. Through crystal rotation experiments, all eight symmetry-related phosphorus sites and their anisotropy were resolved in the ordered phase. Zero-field ⁶³,⁶⁵Cu NMR measurements yield an internal field at the copper site B_int = 14.50(6) T and a quadrupole frequency ν_Q = 32.72(5) MHz. Combined with point-charge electric field gradient calculations, the hole occupancy at the copper site is determined to be n_d = 0.20(4), indicating ligand-hole-dominated charge transfer character. Comparison among the three compounds reveals that the transferred hyperfine coupling H_hf varies with the system, reflecting differences in local Cu-O-P covalency. Furthermore, the internal field at the ³¹P site in the ordered state of PbTCPO is 69.5 mT, significantly higher than those in BaTCPO (35.6 mT) and SrTCPO (34.6 mT). This enhancement cannot be attributed solely to the dipole term but results from the combined effect of the transferred hyperfine contribution and the cancellation effect arising from the interlayer stacking pattern.\n8. Anomalous magnetotransport in a non-collinear correlated kagome ferromagnet MgMn6Sn6 Relevance Score: 3.6627 Authors: Kakan Deb, Sourav Kanthal, Jyotirmoy Sau, Chandra Shekhar, Manoranjan Kumar, Matthias Gutmann, Jhuma Sannigrahi, Nitesh Kumar Link: http://arxiv.org/abs/2605.07904v1 Summary: We present a combined study of single-crystal neutron diffraction and magnetotransport properties of the room-temperature kagome ferromagnet MgMn₆Sn₆, complemented by first-principles calculations. Neutron diffraction reveals that the Mn magnetic moments are arranged non-collinearly within the basal plane of the kagome bilayers, forming a coplanar but non-collinear magnetic structure with all Mn moments confined to the easy plane. The Hall conductivity exhibits a significant intrinsic contribution of approximately 0.29 e²/h per kagome layer, which is nearly isotropic with respect to the field orientation. At low temperatures, a pronounced anisotropic extrinsic component emerges in the anomalous Hall conductivity, highlighting the directional sensitivity of scattering processes. The relatively large Sommerfeld coefficient in this f-electron-free system indicates enhanced electronic correlation effects. Thus, MgMn₆Sn₆ serves as an ideal candidate for investigating the influence of electronic correlations on magnetotransport in non-collinear kagome ferromagnets.\n9. Disentangling bulk and surface electronic structure using targeted cleave planes in RuO$_2$ Relevance Score: 3.6197 Authors: Maria H. Visscher, Sebastian Buchberger, Bruno Saika, Shu Mo, Lea Richter, Mats Leandersson, Craig Polley, Andrew P. Mackenzie, Phil D. C. King Link: http://arxiv.org/abs/2605.06798v1 Summary: This work utilizes focused ion beam (FIB) engineering cleavage techniques to fabricate specific (110) and (100) surfaces in RuO₂, enabling high-quality angle-resolved photoemission spectroscopy (ARPES) measurements. The study reveals that the ARPES spectra of RuO₂ are predominantly governed by distinctive surface electronic states. Through comparison with density functional theory (DFT) calculations, we resolve the evolution of these surface states with surface termination and distinguish them from highly three-dimensional bulk states and surface resonances. Furthermore, we find that the strong spin-orbit coupling effects of Ru 4d orbitals are significant in the surface region, and the breaking of spatial inversion symmetry leads to prominent Rashba-type spin splitting of surface bands. The study also demonstrates that the band crossings previously attributed to Dirac nodal lines are in fact artifacts arising from the projection of bulk states onto the surface Brillouin zone in ARPES measurements, and can be reconciled with experimental data without requiring substantial energy shifts of DFT bands. This work successfully resolves the long-standing confusion between bulk and surface states in the electronic structure measurements of RuO₂, providing a crucial foundation for understanding its unconventional electronic and magnetic properties as well as superconductivity.\n10. Electronic excitations in the Shastry-Sutherland compound SrCu$_2$(BO$_3$)$_2$ Relevance Score: 3.5581 Authors: Tariq Leinen, Ola K. Forslund, Eugenio Paris, Nicola Colonna, Marco Caputo, Johan Chang, Gabriel Nagamine, Takashi Tokushima, Conny Såthe, Pascal Puphal, Jeremie Teyssier, Thorsten Schmitt, Nikolay A. Bogdanov, Maria Daghofer, Adrian L. Cavalieri, Flavio Giorgianni Link: http://arxiv.org/abs/2605.07862v1 Summary: This study systematically characterizes high-energy electronic excitations in the Shastry-Sutherland model compound SrCu₂(BO₃)₂ by combining Cu L₃-edge resonant inelastic X-ray scattering (RIXS), broadband optical spectroscopy, and electronic structure calculations. The RIXS measurements reveal a clear set of localized Cu²⁺ d-d excitation peaks within the 1.8–2.4 eV energy range, whose energies and polarization dependencies are in excellent agreement with results from multireference quantum chemical (MRCI+) calculations. Optical spectroscopy identifies two charge transfer (CT) excitation regimes: an absorption onset at 1.2–1.6 eV and a broader high-energy structure centered around approximately 4.5 eV, features that are qualitatively reproduced by DFT+U calculations. The study confirms the energy-scale separation between d-d excitations and CT excitations, with no d-d features observed in the optical response, validating their dipole-forbidden nature and highlighting the complementarity of RIXS and optical spectroscopy. By comparing first-principles calculations (including DFT+U and MRCI+) with experimental data, this work establishes accurate energy scales for local crystal-field and charge-transfer excitations, providing key experimental constraints for quantifying Cu–O hybridization effects and optimizing superexchange magnetic models. These findings are significant for understanding the exotic magnetic phases of this prototypical frustrated quantum antiferromagnet.\n11. Revisiting Ferroelectricity Beyond Polar Space Groups Relevance Score: 3.5399 Authors: Yudi Yang, Changming Ke, Shi Liu Link: http://arxiv.org/abs/2605.07382v1 Summary: This paper revisits ferroelectric phenomena that transcend the traditional polar space group paradigm through the lens of Berry phase-based modern polarization theory. Methodologically, polarization is defined as a multivalued lattice quantity modulo polarization quanta, rather than a single vector, and a generalized Neumann principle is introduced to govern the symmetry of formal polarization. By distinguishing formal polarization from effective polarization, the paper analyzes the mechanisms underlying quantized changes in polarization during adiabatic cycles: adiabatic paths between symmetrically equivalent structures or long-range ionic migration can induce discrete jumps in formal polarization without violating symmetry principles. In conclusion, the paper argues that the origin of switchable polarization in fractional quantum ferroelectrics and ionic conductor ferroelectrics can be naturally attributed to a topological definition of oxidation state, which connects ionic transport to quantized charge transfer and polarization changes. The practical functionality of these materials does not lie in conventional bulk ferroelectric switching, but rather in utilizing discontinuities in formal polarization to create and control charged interfaces and domain walls, thereby enabling novel functional devices. The paper emphasizes that understanding these unconventional polarization states requires moving beyond static symmetry constraints to consider physical factors such as ionic transport kinetics, boundary conditions, and domain wall dynamics.\n12. Checkerboard Bose Hubbard Ladders using Transmon Arrays Relevance Score: 3.4806 Authors: Pranjal Praneel, Thomas G Kiely, Andre G Petukhov, Erich J Mueller Affiliations: University of California, Santa Barbara, Cornell University, Google Quantum AI Link: http://arxiv.org/abs/2605.07906v1 Summary: This paper investigates the implementation and physical properties of the checkerboard Bose-Hubbard model in a transmon array. The authors propose tuning the model by introducing a sublattice bias, thereby bringing the commensurate superfluid phase into an experimentally accessible regime and providing new detection methods. A quantum simulator is constructed using superconducting transmon arrays, where each transmon serves as an anharmonic quantum oscillator, with its energy levels corresponding to the particle number at a lattice site. Capacitive coupling enables particle hopping, and nonlinear terms provide on-site interactions. The study focuses on ladder geometries with varying leg numbers. The ground state is prepared from an insulating state through slow adiabatic evolution, and observables such as localization length, energy gap, and polarization are measured to characterize superfluid and insulating phases. Particular attention is given to finite-size effects and the robustness of insulating states in even-leg ladders. By mapping the system to a spin model (hard-core bosons or the XY model), analytical solutions are obtained within specific parameter windows. Numerical calculations present the phase diagram as a function of sublattice bias and coupling strength, and the timescale required for adiabatic state preparation is explored, along with its dependence on system size. This work provides a concrete roadmap for exploring novel quantum phases of strongly correlated bosonic systems using current transmon quantum processors.\n13. Nonadiabatic Theory of Phonon Magnetic Moments in Insulators and Metals Relevance Score: 3.4459 Authors: Haoran Chen, Wenqin Chen, Kaijie Yang, Ting Cao, Di Xiao Link: http://arxiv.org/abs/2605.06983v1 Summary: We develop a non-adiabatic theory of phonon magnetic moment applicable to both insulators and metals. By relating the phonon magnetic moment to the force-velocity response of ions in a magnetic field, we derive a gauge-invariant expression using the gauge-covariant Wigner expansion. This formalism naturally separates contributions from the Fermi sea and the Fermi surface, and fully captures the frequency dependence of phonons. In gapped systems, the theory reduces to the previous adiabatic expression in the low-frequency limit; beyond this limit, it reveals additional contributions arising from resonant interband processes and the Fermi surface. Applied to Pb$_{1-x}$Sn$_x$Te, we find that the Fermi surface contribution significantly enhances the phonon magnetic moment, bringing it to the same order of magnitude as experimental observations. Our results provide a unified framework for describing phonon magnetic moments beyond the adiabatic regime.\n14. Topological superconductivity in a Hubbard model for twisted bilayer cuprates Relevance Score: 3.4131 Authors: T. Vibert, D. Sénéchal Link: http://arxiv.org/abs/2605.06923v1 Summary: This study employs the Hubbard model to describe twisted bilayer cuprates. Within the weak interaction regime (U/t=3.85), the superconducting order parameter is calculated using the variational cluster approximation (VCA), and the Chern number is obtained via the topological Hamiltonian method. The topological superconducting properties of the system are systematically investigated. The results indicate that the topological properties are highly sensitive to the doping level: under electron doping, the Chern number reaches ±8, signifying nontrivial topology; whereas under hole doping, the Chern number is zero, corresponding to a topologically trivial phase. The existence of the nontrivial topological phase is further confirmed through edge-state analysis in a finite-width ribbon geometry—the edge states of the electron-doped system exhibit chiral characteristics, consistent with the bulk Chern number calculations. The study also finds that in the weak interaction regime, the time-reversal symmetry broken superconducting phase has the largest order parameter near half-filling, which decreases with reduced doping. This work demonstrates that, even in the presence of multiband complexity, topological superconductivity can be reliably identified via the Chern number and edge-state analysis in the weak interaction regime, providing a microscopic theoretical basis for realizing topological superconductivity in actual twisted bilayer cuprate systems.\n15. Spin-lattice coupling enables adaptive adsorption in magnetically-driven electrocatalysts Relevance Score: 3.3940 Authors: Arnold Gaje, Lulu Li, Felipe A. Garcés-Pineda, Camilo A. Mesa, Ghazaleh Abdolhosseini, Aditya K. Kushwaha, Dora Zalka, Elzbieta Trzop, Nicolas Godin, Raffaella Torchio, María Escudero-Escribano, Eric Collet, Sixto Giménez, Niels Keller, José Ramón Galán-Mascarós, Núria López, Ernest Pastor Affiliations: ICREA, Catalan Institute of Nanoscience and Nanotechnology, Universitat Jaume I, The University of Tokyo, Institute of Chemical Research of Catalonia, Universitat Rovira i Virgili, European Synchrotron Radiation Facility, Univ. Rennes Link: http://arxiv.org/abs/2605.07437v1 Summary: This study investigates how external magnetic fields relax the linear scaling relationship of intermediates in the oxygen evolution reaction (OER) through spin-lattice coupling. Using Ni-Fe oxyhydroxide as a model catalyst, combined with spectroscopic measurements and density functional theory (DFT) simulations, it was found that applying a magnetic field can alter surface chemisorption and introduce interfacial structural flexibility. DFT calculations reveal the existence of multiple quasi-degenerate intermediates under different spin states (high-spin/low-spin) and oxidation states, which possess distinct atomic and electronic structures, with their energy distributions breaking the one-to-one correspondence between conventional adsorption energies. UV-VIS spectroelectrochemical experiments observed magnetic-field-induced changes in the population of redox intermediates, while magneto-optical Faraday responses showed a strong correlation between electrode magnetization and electrochemical current, including hysteresis loops and coercivity characteristics, indicating that magnetic stimulation can directly affect reaction kinetics. Both experiments and theory demonstrate that the magnetic field, by exciting changes in spin-lattice coupling, enables the system to access previously inaccessible oxygen-containing intermediates, thereby independently modulating the energy requirements of each reaction step. This redefines the nature of the scaling limit—it is not an intrinsic constraint but a limitation imposed by the projection of electronic states. This study proves that external stimuli such as magnetic fields can serve as an effective strategy to break the linear scaling relationship, offering new insights for optimizing electrocatalytic reaction pathways within a multi-state energy landscape.\n16. Epitaxial growth of beta-bismuthene on Sb2Te3 Relevance Score: 3.3568 Authors: Giorgia Sementilli, Arslan Masood, Fabio Ronci, Stefano Colonna, Marilena Carbone, Marco Papagno, Ziya S. Aliev, Evgueni V. Chulkov, Sergey V. Eremeev, and Roberto Flammini Link: http://arxiv.org/abs/2605.07700v1 Summary: This article reports the first successful growth of β-bismuthene on a three-dimensional topological insulator Sb₂Te₃ substrate via molecular beam epitaxy, and systematically investigates its growth mechanism and atomic structure using scanning tunneling microscopy. The study reveals that at room temperature, when the bismuth coverage reaches approximately 0.5 bilayers, island coalescence and the formation of triangular islands begin, marking the onset of β-bismuthene nucleation. At a coverage of one bilayer, the islands exhibit a uniform triangular morphology and achieve complete lattice matching with the substrate (lattice constant ~0.43 nm). By varying the substrate temperature (room temperature, 200 K, 150 K), it is found that lower temperatures significantly affect the size, shape, and density of the islands: at 200 K, the island edges become blurred, while at 150 K, high-density small islands form; nevertheless, a hexagonal honeycomb structure is maintained at all temperatures. Atomically resolved images show a coherent epitaxial interface between the bismuthene layer and the Sb₂Te₃ substrate. Intrinsic defects in the substrate, such as antimony antisites and tellurium vacancies, are replicated in the bismuthene layer with similar defect features through local electronic density of states perturbations. Annealing experiments indicate that annealing at 500 K causes bismuth atoms to migrate to step edges, disrupting the island order. This work confirms that β-bismuthene/Sb₂Te₃ constitutes an ideal van der Waals heterostructure, providing a high-quality platform for studying spin-orbit coupling and proximity effects in two-dimensional/three-dimensional topological insulator interfaces.\n17. Quantum spin liquid on a 3D bipartite lattice of spin trimers stabilized by enhanced effective anisotropy Relevance Score: 3.3517 Authors: M. Gomilšek, L. Mangin-Thro, T. Arh, S. Petit, B. Grenier, V. Simonet, M. Pregelj, A. Zorko, B. Koteswararao, B. -G. Jeon, B. Sana, Y. Furukawa, Y. Inagaki, T. Asano, C. Repellin, B. Fåk, J. Ollivier, F. Fauth, C. V. Colin, E. Pachoud, V. Pomjakushin, J. S. Lord, H. Luetkens, K. -H. Kim, P. Khuntia Link: http://arxiv.org/abs/2605.06752v1 Summary: This paper reports a quantum spin liquid candidate material, KBa₃Ca₄Cu₃V₇O₂₈, based on a three-dimensional bipartite lattice of spin trimers. Upon cooling, strongly coupled Cu²⁺ trimers condense into effective pseudospin-1/2 degrees of freedom, forming a three-dimensional bipartite lattice network. Comprehensive experimental measurements, including specific heat, thermal conductivity, neutron scattering, μSR, and nuclear magnetic resonance, reveal that the system exhibits no spin freezing or symmetry-breaking phase transitions down to 20 mK. Instead, it displays a gapless dynamic ground state with algebraic spin-spin correlations. Monte Carlo and exact diagonalization calculations demonstrate that the stabilization of this quantum spin liquid state originates from a significant enhancement of effective anisotropy: microscopically only about 15% weak Cu-Cu exchange anisotropy is universally amplified to 60–100% effective anisotropy between pseudospins upon projection onto the Kramers doublet ground state of the trimers. This mechanism resembles the anisotropy stabilization in the Kitaev model but, for the first time, realizes a quantum spin liquid in a three-dimensional bipartite lattice via weak microscopic anisotropy. This work identifies networks based on spin trimers as highly promising platforms for exploring anisotropy-stabilized quantum entangled states, including those in three-dimensional bipartite lattice systems.\n18. Anisotropic Defect Diffusion in Layered CsPbBr$_\\mathrm{x}$I$_\\mathrm{3-x}$ Perovskites Relevance Score: 3.2628 Authors: Konrad Wilke, Mike Pols, Titus S. van Erp, Geert Brocks, Shuxia Tao Link: http://arxiv.org/abs/2605.08055v1 Summary: In this study, we employed large-scale molecular dynamics simulations using the reactive force field (ReaxFF) to systematically investigate the influence of layered ordered halide arrangements on defect diffusion behavior in CsPbBrₓI₃₋ₓ perovskites. By comparing layered ordered structures with randomly mixed structures, we found that layered halide ordering induces strong anisotropic defect diffusion: migration along the direction of the halide layers is highly facile, whereas cross-layer diffusion is significantly suppressed. For cesium (Cs) defects, this anisotropy originates from the directional lattice strain induced by the layered structure and the corresponding octahedral tilting patterns, which lock specific Pb-I-Pb bond angles in certain directions, hindering the hopping motion of Cs atoms across layers. For halide defects (Br, I vacancies or interstitials), the migration anisotropy is jointly influenced by strain and local halide bonding configurations. Furthermore, by applying biaxial strain to pure CsPbI₃ and CsPbBr₃ in simulations, we verified the critical role of strain in generating anisotropic diffusion. These results indicate that through the design of layered halide ordering, directional defect migration can be effectively controlled, thereby potentially enhancing the structural stability of the material, and providing a new atomic-scale design strategy for optimizing the optoelectronic performance of mixed-halide perovskites.\n19. Majorana bound states in chiral ferromagnet-superconductor heterostructures revisited Relevance Score: 3.2505 Authors: A. S. Slobodskoi, S. S. Apostoloff, I. S. Burmistrov Link: http://arxiv.org/abs/2605.06828v1 Summary: This paper presents a comprehensive theoretical analysis of low-energy quasiparticle bound states in chiral ferromagnet-superconductor heterostructures. The study focuses on the skyrmion-vortex pair system, composed of a magnetic skyrmion and a superconducting vortex, which has recently been realized experimentally and theoretically predicted to host localized Majorana zero modes. Using the Bogoliubov-de Gennes framework, we develop an analytical formalism for the Majorana wavefunctions as well as the wavefunctions and energy spectra of other low-energy bound states. Approximate analytical expressions are derived for the Majorana states and low-energy bound states at the superconducting vortex, both with and without an accompanying skyrmion, explicitly demonstrating the crucial role of spin-orbit coupling in stabilizing the Majorana mode—without it, the vortex-localized Majorana states would cease to exist. Our analytical results show good agreement with numerical simulations. Additionally, we evaluate the effects of realistic factors, such as the vector potential generated by the vortex and stray field perturbations from the magnetic texture, on the system. These analyses provide an important theoretical foundation for topological quantum computing based on skyrmion-vortex pairs and contribute to understanding the spatial structure of Majorana states and the low-energy excitation spectrum.\n20. Ground states of quantum XY dipoles on the Archimedean lattices Relevance Score: 3.1421 Authors: Marcus Bintz, Ahmed Khalifa, Vincent S. Liu, Johannes Hauschild, Michael P. Zaletel, Shubhayu Chatterjee, Norman Y. Yao Link: http://arxiv.org/abs/2605.07685v1 Summary: This thesis employs large-scale density matrix renormalization group (DMRG) calculations to systematically investigate the ground-state properties of the quantum XY dipolar model on nine of the eleven Archimedean lattices. This model describes extended antiferromagnetic interactions in two-dimensional arrays of polar molecules and Rydberg atoms, with its ground state being entirely determined by geometric arrangement. The study finds that the ground states of these lattices fall into two main categories: on five lattices—square, hexagonal, truncated square, snub square, and truncated trihexagonal—the system exhibits collinear Néel antiferromagnetic order with long-range correlations and a clear alternating sign structure; on the other four lattices—elongated triangular, truncated hexagonal, rhombillitic, and snub trihexagonal—the system is in a trivial paramagnetic state, characterized by a tensor product of local singlets formed by adjacent spins. For lattices with collinear order, the thesis calculates hydrodynamic parameters such as magnetization, magnetic susceptibility, and spin stiffness, comparing them with results from linear spin wave theory. On the triangular lattice, several competing phases are identified, including coplanar magnetic order, stripe density wave order, and a possible spin liquid phase, whose relative stability is sensitive to the long-range coupling in the dipolar model. Additionally, the thesis points out that on the kagome lattice, the system may be a Dirac spin liquid (see companion work for details). This study reveals the decisive influence of geometric arrangement on the ground-state phase diagram of quantum spin systems, providing theoretical guidance for quantum simulations in ultracold atomic and molecular experiments.\n","permalink":"https://nickelates.uk/en/posts/2026-05-12-arxiv-daily/","summary":"\u003cblockquote\u003e\n\u003cp\u003e\u003cstrong\u003eDaily Overview\u003c/strong\u003e:\nAlthough today\u0026rsquo;s daily paper overview does not directly include works related to nickelate superconductors, it covers several highlights closely tied to unconventional superconductivity, topological superconductivity, and strongly correlated electron systems, offering multidimensional perspectives for understanding superconducting pairing mechanisms and quantum state manipulation. Key highlights include: \u003cstrong\u003e《(BaS)₁/₃TaS₂》\u003c/strong\u003e achieves bulk two-dimensional Ising superconductivity with both high transition temperature and large interlayer spacing, breaking traditional trade-offs through a chain-intercalation strategy; \u003cstrong\u003e《d-wave altermagnets》\u003c/strong\u003e reveals that d-wave altermagnets can stabilize finite-temperature pair density wave phases without an external magnetic field; \u003cstrong\u003e《cuprate superconductivity》\u003c/strong\u003e uses first-principles three-band modeling to confirm the indispensability of long-range hopping for the superconducting dome and pairing symmetry in cuprates; \u003cstrong\u003e《twisted bilayer cuprates》\u003c/strong\u003e predicts topological superconducting states with Chern numbers up to ±8 under electron doping in a weakly interacting Hubbard model; \u003cstrong\u003e《Majorana bound states》\u003c/strong\u003e provides an analytical framework for Majorana modes hosted by skyrmion-vortex pairs in chiral ferromagnet-superconductor heterostructures. Additionally, the discovery of the \u003cstrong\u003ethree-dimensional bipartite quantum spin liquid\u003c/strong\u003e candidate material KBa₃Ca₄Cu₃V₇O₂₈, and the successful decoupling of \u003cstrong\u003eRuO₂ surface electronic states\u003c/strong\u003e from bulk states, provide important experimental foundations for studying novel quantum states in correlated electron systems.\u003c/p\u003e","title":"arXiv Daily: Nickelate superconductors 2026-05-12"},{"content":" Daily Overview:\nToday\u0026rsquo;s Quick Overview of the Ni-Based Superconductor Field \u0026gt; Among today\u0026rsquo;s submissions, no research papers directly targeting nickel-based superconductors were found. However, several works have made important progress in closely related directions such as superconducting mechanisms, strongly correlated electron systems, and topological superconductivity, offering potential insights for nickel-based superconductor research: \u0026gt; 1. Cuprate Superconductivity Theory: A work systematically studying the three-band Emery model via the dynamical vertex approximation (DA) is noteworthy. The study points out that traditional simplified models are insufficient for quantitatively describing the cuprate superconducting phase diagram; instead, the full set of long-range hopping parameters derived from first principles must be included to obtain a superconducting dome (doping range 7–22%) and d-wave order parameter consistent with experiments. Given the electronic structure similarities between nickel-based superconductors and cuprates, this methodology has direct reference value for theoretical modeling of nickel-based superconductors. \u0026gt; 2. Topological Superconductivity in Twisted Bilayer Hubbard Model: A study using the variational cluster approximation investigates topological superconductivity in twisted cuprate bilayers. It reveals that in the weak-interaction regime below the Mott transition, the electron-doped side can realize nontrivial topological superconducting states with Chern numbers up to ±8, while the hole-doped side remains topologically trivial. This microscopic mechanism provides a theoretical framework for exploring possible topological phases in nickel-based superconductors. \u0026gt; 3. Pair-Density Wave in Altermagnets: A non-perturbative Monte Carlo study reveals that d-wave altermagnets can stabilize finite-momentum superconductivity (pair-density wave) without requiring an external magnetic field. This originates from the momentum-dependent spin splitting, which effectively enhances pairing at finite center-of-mass momentum while suppressing the uniform superconducting channel. This mechanism offers a new perspective for understanding possible incommensurate superconducting orders in nickel-based superconductors. \u0026gt; 4. Theory of Majorana Bound States: An analytical theoretical work on chiral ferromagnet–superconductor heterostructures clarifies the crucial role of spin-orbit coupling for the existence of Majorana zero modes and provides the threshold condition for the spin-orbit coupling strength. These results have theoretical guiding significance for designing topological quantum computing platforms based on nickel-based superconductors. \u0026gt; Summary: Although no studies directly targeting nickel-based superconductors were submitted today, theoretical advances in directions such as multi-orbital models for cuprates, topological superconductivity in twisted bilayers, and pair-density waves in altermagnets provide important inspiration for refined modeling, topological state exploration, and understanding of unconventional superconducting mechanisms in nickel-based superconductor systems, meriting the attention of researchers in the field. 1. Breaking the Trade-off: Bulk 2D Ising Superconductivity with High Tc and Giant Interlayer Spacing via a Unique Chain Intercalation in (BaS)1/3TaS2 Relevance Score: 4.3582 Authors: Ziyi Zhu, Leiming Chen, Xiangqi Liu, Haonan Wang, Chen Xu, Ze Yan, Zhengyang Li, Wei Xia, Jiawei Luo, Na Yu, Xia Wang, Ke Qu, Zhenzhong Yang, Yanfeng Guo Affiliations: East China Normal University, ShanghaiTech University, Zhengzhou University of Aeronautics Link: http://arxiv.org/abs/2605.07336v1 Summary: This paper reports the synthesis of a new polymorph, (BaS)₁/₃TaS₂, via a unique chain-like intercalation strategy, which successfully overcomes the long-standing trade-off between high superconducting transition temperature (Tc) and increased interlayer spacing/enhanced two-dimensionality in conventional intercalation systems. In this structure, Ba-S-S-Ba chains are inserted between TaS₂ bilayers, forming locally decoupled two-dimensional superconducting layers with an interlayer spacing of 12.75 Å, more than three times that of pristine 2H-TaS₂. This structural configuration breaks the bulk c-axis mirror symmetry, significantly suppresses interlayer electronic coupling, and renders local inversion symmetry breaking within individual TaS₂ layers dominant, thereby avoiding the compensation of the Ising spin–orbit field in the centrosymmetric bulk and realizing robust bulk two-dimensional Ising superconductivity. Comprehensive transport, magnetic, and thermodynamic measurements confirm that (BaS)₁/₃TaS₂ exhibits an enhanced Tc, an in-plane upper critical field far exceeding the Pauli limit, and pronounced superconducting anisotropy, demonstrating the successful coexistence of high Tc with large interlayer spacing/high two-dimensionality. This work establishes a generic intercalation framework for designing bulk two-dimensional Ising superconductors, offering a new route to reconcile competing demands in materials and expanding the scope of Ising superconductivity research.\n2. Anomalous Phase-Coherence Scaling in a Quantum-Critical Dirac Semimetal Relevance Score: 4.0071 Authors: Sana Nakamichi, Ryotaro Kobara, Yoshinari Unozawa, Yoshitaka Kawasugi, Sakura Hiramoto, Koki Funatsu, Toshio Naito, Masafumi Tamura, Reizo Kato, Yutaka Nishio, Naoya Tajima Link: http://arxiv.org/abs/2605.07085v1 Summary: By investigating the weak antilocalization (WAL) effect during the quantum phase transition driven by the charge-ordered insulating state in the pressurized Dirac semimetal α-(BEDT-TTF)₂I₃, the phase coherence length Lφ and its temperature scaling were extracted from low-temperature magnetoconductance. In the high-pressure region, the system exhibits conventional two-dimensional dephasing behavior (Lφ ∝ T⁻ᵖ, p ≈ 1/2), consistent with electron-electron scattering in diffusive conductors. As the pressure approaches the critical pressure Pc ≈ 1.2 GPa, the temperature exponent decreases to p ≈ 0.3, while Lφ remains relatively large (approximately 700–800 nm at 0.5 K). This anomalous scaling suggests a nontrivial inelastic scattering mechanism for Dirac electrons near the quantum critical point. The persistence of WAL throughout the phase transition supports the identification of this transition as a gapless or nearly gapless quantum phase transition. The research methodology is based on fitting the low-field magnetoconductance with the quasi-two-dimensional Hikami-Larkin-Nagaoka model, self-consistently extracting Lφ and the prefactor, and analyzing their pressure and temperature dependencies. The conclusions reveal the presence of a quantum critical regime in strongly correlated Dirac systems, characterized by a large phase coherence length but a significant deviation of the temperature scaling from conventional behavior, providing experimental evidence for quantum critical transport in correlated Dirac semimetals.\n3. Noncollinear antiferromagnetic structure and physical properties of CrRhAs with distorted kagome lattice Relevance Score: 3.8590 Authors: Chenglin Shang, Daye Xu, Bingxian Shi, Xuejuan Gui, Zhongcen Sun, Juanjuan Liu, Jinchen Wang, Hongxia Zhang, Hongliang Wang, Lijie Hao, Peng Cheng Affiliations: Renmin University of China, China Institute of Atomic Energy Link: http://arxiv.org/abs/2605.07540v1 Summary: A systematic experimental investigation has been carried out on the magnetic structure and physical properties of the ZrNiAl-type compound CrRhAs with a distorted Kagome lattice. The results indicate that CrRhAs undergoes an antiferromagnetic phase transition at TN = 149 K. Powder neutron diffraction analysis reveals a non-collinear antiferromagnetic order with a propagation vector k = (1/3, 1/3, 1/2), and the characteristics of ferromagnetic next-nearest-neighbor coupling within the Kagome plane differ from previous predictions based on density functional theory calculations. The electrical transport properties exhibit anomalous behavior: the longitudinal resistivity shows semiconductor-like behavior above TN, but becomes metallic below TN; the Hall coefficient undergoes two sign reversals near 70 K and 300 K, which may be associated with multi-band effects and strong spin fluctuations. Combined with specific heat measurements, a large Kadowaki-Woods ratio α = 33.9 μΩ·cm·mol²·K²/J² is obtained, indicating that CrRhAs is a strongly correlated Kagome metal with multi-band and non-collinear magnetic structure characteristics. Furthermore, magnetic susceptibility measurements yield an effective magnetic moment of 3.79 μB/Cr, corresponding to the S = 3/2 spin state of Cr³⁺, and reveal a certain degree of spin frustration (θCW/TN ≈ 3.2). These findings provide important experimental evidence for understanding magnetism and electronic correlations in distorted Kagome lattices.\n4. Beyond the conventional Emery model: crucial role of long-range hopping for cuprate superconductivity Relevance Score: 3.8428 Authors: Eric Jacob, M. O. Malcolms, Viktor Christiansson, Leonard M. Verhoff, Paul Worm, Liang Si, Philipp Hansmann, Thomas Schäfer, Karsten Held Link: http://arxiv.org/abs/2605.07739v1 Summary: Using the dynamical vertex approximation (DA) method, this study performs precise calculations on the three-band Emery model for cuprate superconductors. It is found that the conventional simplified model, which includes only the Cu-O next-nearest-neighbor and O-O nearest and next-nearest-neighbor hopping parameters (three terms in total), is insufficient to quantitatively describe the superconducting phase diagram. Based on first-principles calculations (DFT+Wannier) and the constrained random phase approximation (cRPA) to obtain the complete hopping parameters, we find that the long-range hopping terms (other nearest-neighbor and next-nearest-neighbor hoppings beyond the conventional three terms) are crucial for obtaining a superconducting dome consistent with experiment (doping range approximately 7-22%) and the correct d-wave order parameter. If only the traditional three hopping parameters are used, the superconducting dome contracts significantly to a smaller doping range (9%-14%), and the d-wave order parameter exhibits anomalous modulation at the antinodal region, which arises from the van Hove singularity being too close to the Fermi level. The presence of long-range hopping terms makes the band structure closer to that of real materials. In particular, they bring the next-nearest-neighbor hopping parameter of the effective single-band Hubbard model into agreement with experimental values (the traditional model underestimates it by a factor of about 3.5). Our work demonstrates that to accurately describe cuprate superconductivity, it is necessary to include the complete orbital hopping parameters in the Emery model, which opens the way for more material-realistic studies.\n5. Finite temperature pair density wave superconductivity in $d$-wave altermagnets Relevance Score: 3.8391 Authors: Amrutha N Madhusuthanan, Madhuparna Karmakar Link: http://arxiv.org/abs/2605.07656v1 Summary: This study systematically investigates finite-momentum superconductivity in two-dimensional d-wave altermagnets using the non-perturbative static path approximation Monte Carlo method. The results demonstrate that altermagnets provide a mechanism for stabilizing the pair density wave (PDW) state without the need for an external magnetic field. This mechanism originates from the momentum-dependent spin splitting unique to altermagnets, which effectively enhances pairing instabilities at finite center-of-mass momentum while suppressing the uniform superconducting channel. Consequently, a robust PDW phase is maintained even under strong thermal fluctuations and exists within a finite temperature window. Through analysis of the thermal phase diagram, the study identifies distinct thermal scales associated with phase coherence, gap closure, and pseudogap formation, and determines the characteristic spectroscopic and real-space signatures of the PDW state. These findings reveal that altermagnets offer a feasible route to realizing thermally stable finite-momentum superconductivity, providing testable predictions for experimental exploration in relevant altermagnetic materials.\n6. Emergent Dynamic Magnetic Ground State in a Mixed 3d/5d Heavy Fermion System CaCu3Ir4O12 Relevance Score: 3.6954 Authors: J. Ming, Abhisek Bandyopadhyay, G. B. G. Stenning, M. T. F. Telling, N. N. Wang, G. Wang, J. -G. Cheng, D. T. Adroja Affiliations: University of Chinese Academy of Sciences, Rutherford Appleton Laboratory, Lalit Narayan Mithila University, University of Johannesburg, Chinese Academy of Sciences Link: http://arxiv.org/abs/2605.07602v1 Summary: This study systematically investigates the magnetic ground state of the three-dimensional hybrid 3d/5d heavy fermion system CaCu₃Ir₄O₁₂ by combining macroscopic probes (DC and AC magnetic susceptibility, specific heat down to 50 mK) with microscopic local probes (muon spin relaxation down to 40 mK). Despite the strong coupling between the 3d magnetic moments of Cu²⁺ and the extended Ir 5d network in the cubic Im-3 structure, accompanied by significant antiferromagnetic interactions (field-dependent Weiss temperature θ_W ~ −200 K), no evidence of long-range magnetic order or spin freezing is detected at any measured temperature. In-depth analysis of zero-field and longitudinal-field μSR spectra confirms that the local magnetic moments remain strongly quantum fluctuating down to 40 mK, exhibiting genuinely dynamic behavior. These results establish CaCu₃Ir₄O₁₂ as a promising three-dimensional quantum disordered magnet, providing an ideal platform for exploring fluctuation-dominated magnetic ground states in correlated 3d/5d oxides.\n7. Microscopic Magnetism of A(TiO)Cu4(PO4)4 (A = Ba, Pb, Sr): 31P and 63,65Cu NMR Study Relevance Score: 3.6892 Authors: Riho Rästa, Ivo Heinmaa, Joosep Link, Yusuke Kousaka, Tsuyoshi Kimura, Yoshihiko Ihara, Kenta Kimura, Raivo Stern Link: http://arxiv.org/abs/2605.07946v1 Summary: In this paper, we systematically investigate the antiferromagnet Pb(TiO)Cu₄(PO₄)₄ (PbTCPO) with a chiral tetragonal cup-like structure using 31P and 63,65Cu nuclear magnetic resonance (NMR), and compare it with the isostructural Ba/Sr analogs. In the paramagnetic state (above T_N ≈ 6.7 K), the 31P Knight shift varies with the bulk magnetic susceptibility, yielding nearly isotropic transferred hyperfine coupling constants: H_hf^[010] = 6.77(3) kOe/μ_B and H_hf^[001] = 6.19(3) kOe/μ_B. Upon entering the ordered state, the frequency-swept 31P spectra split into three lines (distinct from the four lines in BaTCPO), and the line splitting increases with the static 31P internal field according to a power law with exponent β ≈ 0.23, consistent with quasi-two-dimensional critical behavior. Using crystal-rotation NMR, we resolved all eight symmetry-related P sites and their anisotropy in the ordered state. Zero-field 63,65Cu NMR measurements yield an internal field B_int = 14.50(6) T and a quadrupole frequency ν_Q = 32.72(5) MHz at the Cu site. Combined with point-charge electric field gradient calculations including Sternheimer corrections, the hole occupancy at the Cu site is determined to be n_d = 0.20(4), indicating that charge transfer is dominated by ligand holes. Comparison across the series reveals that the transferred hyperfine coupling varies with the A-site element, reflecting differences in local Cu-O-P covalency. Moreover, the 31P internal field in the ordered state of PbTCPO is 69.5 mT, significantly higher than those of BaTCPO (35.6 mT) and SrTCPO (34.6 mT). This enhancement cannot be explained solely by the dipolar term; instead, it results from the combined effect of the transferred contribution and a stacking-dependent cancellation.\n8. Anomalous magnetotransport in a non-collinear correlated kagome ferromagnet MgMn6Sn6 Relevance Score: 3.6373 Authors: Kakan Deb, Sourav Kanthal, Jyotirmoy Sau, Chandra Shekhar, Manoranjan Kumar, Matthias Gutmann, Jhuma Sannigrahi, Nitesh Kumar Link: http://arxiv.org/abs/2605.07904v1 Summary: Through neutron diffraction, magnetotransport measurements, and first-principles calculations on MgMn6Sn6 single crystals, this paper reveals its non-collinear magnetic structure and associated magnetotransport properties. Neutron diffraction experiments show that Mn magnetic moments are arranged non-collinearly within the kagome bilayer basal plane, exhibiting weak in-plane anisotropy. Hall effect measurements reveal a significant intrinsic contribution to the Hall conductivity, approximately 0.29 e²/h per kagome layer, which is nearly isotropic with respect to the magnetic field direction. At low temperatures, the anomalous Hall conductivity exhibits a pronounced anisotropic extrinsic component, indicating directional sensitivity in the scattering process. Additionally, this material exhibits an exceptionally large Sommerfeld coefficient in the absence of f electrons, confirming strong electronic correlation effects. These results demonstrate that MgMn6Sn6 serves as an ideal platform for studying the interplay between electronic correlations and topological magnetotransport.\n9. Disentangling bulk and surface electronic structure using targeted cleave planes in RuO$_2$ Relevance Score: 3.6232 Authors: Maria H. Visscher, Sebastian Buchberger, Bruno Saika, Shu Mo, Lea Richter, Mats Leandersson, Craig Polley, Andrew P. Mackenzie, Phil D. C. King Link: http://arxiv.org/abs/2605.06798v1 Summary: This study employs focused ion beam (FIB) engineering cleavage to fabricate target (110) and (100) surfaces on RuO₂ single crystals, enabling high-quality angle-resolved photoelectron spectroscopy (ARPES) measurements. It is found that the ARPES spectra of RuO₂ are predominantly governed by contributions from various surface electronic states. By comparing with density functional theory (DFT) calculations, the authors reveal the evolution of these surface states with surface termination (oxygen-rich or ruthenium-rich) and successfully distinguish them from highly three-dimensional bulk bands and surface resonances. Additionally, significant spin-orbit coupling effects are observed for Ru 4d orbitals in the surface region: due to the breaking of spatial inversion symmetry at the surface, these surface bands exhibit pronounced Rashba-type spin splitting. Through measurements on different cleavage planes and theoretical simulations, the authors clarify that band crossings previously misidentified as Dirac nodal lines are actually artifacts arising from the projection of bulk bands onto the surface Brillouin zone, achieving agreement with experiment without requiring large energy shifts of DFT bands. Moreover, various surface resonance states (such as quasi-one-dimensional flat bands SS1 and SS2–SS4) are observed experimentally, whose behavior is qualitatively consistent with DFT calculations for different surface terminations, with spin-orbit coupling further splitting these surface bands. This work demonstrates that FIB-assisted cleavage is an effective method for studying the electronic structure of strongly three-dimensional crystalline materials, particularly for separating bulk and surface states.\n10. Revisiting Ferroelectricity Beyond Polar Space Groups Relevance Score: 3.5278 Authors: Yudi Yang, Changming Ke, Shi Liu Link: http://arxiv.org/abs/2605.07382v1 Summary: This paper re-examines the traditional definition of ferroelectricity, arguing that ferroelectricity need not be confined to polar space groups. Based on the modern theory of polarization using Berry phases, it points out that the formal polarization in periodic insulating crystals is a multivalued lattice quantity modulo a polarization quantum, rather than a single-valued vector. Consequently, non-polar crystals can also possess non-zero formal polarization, and adiabatic paths connecting symmetrically equivalent structures can yield quantized polarization changes. By distinguishing formal polarization from effective polarization (i.e., measurable charge flow), the paper unifies the unconventional polarization behaviors in fractional quantum ferroelectrics (FQFE) and ionic conductor ferroelectrics (ICFE) under a common framework: the topological definition of oxidation state naturally links long-range ionic migration with quantized charge transfer and polarization changes. The study further analyzes the physical realizability of these unconventional polarization states, emphasizing the critical roles of switching paths, boundary conditions, and domain wall dynamics, particularly in the α-In₂Se₃ system. The final conclusion is that the most promising functionalities of such materials lie not in conventional bulk ferroelectric switching, but in utilizing discontinuities in formal polarization to create and control charged interfaces and domain walls.\n11. Electronic excitations in the Shastry-Sutherland compound SrCu$_2$(BO$_3$)$_2$ Relevance Score: 3.5206 Authors: Tariq Leinen, Ola K. Forslund, Eugenio Paris, Nicola Colonna, Marco Caputo, Johan Chang, Gabriel Nagamine, Takashi Tokushima, Conny Såthe, Pascal Puphal, Jeremie Teyssier, Thorsten Schmitt, Nikolay A. Bogdanov, Maria Daghofer, Adrian L. Cavalieri, Flavio Giorgianni Link: http://arxiv.org/abs/2605.07862v1 Summary: This study systematically characterizes high-energy electronic excitations in the Shastry-Sutherland model compound SrCu₂(BO₃)₂ (SCBO) by combining Cu L₃-edge resonant inelastic X-ray scattering (RIXS), broadband optical spectroscopy, and electronic structure calculations (DFT+U and multireference quantum chemistry methods). The RIXS experiments clearly resolve the local Cu²⁺ d-d excitation spectrum in the energy range of 1.8–2.4 eV, and the energy and polarization dependences show excellent agreement with multireference configuration interaction (MRCI+) calculations, confirming the crystal-field origin of these excitations. Optical spectroscopy reveals the absorption onset of low-energy charge transfer excitations (1.2–1.6 eV) as well as a broad peak structure near 4.5 eV, features that are qualitatively reproduced by DFT+U calculations. The two types of experiments complementarily define the characteristic energy scales of local d-d transitions and charge transfer excitations in SCBO, providing quantitative benchmarks for first-principles computational methods and offering critical input for refining superexchange-based magnetic models (such as the exchange parameters in the Shastry-Sutherland model). This work highlights the synergistic role of RIXS and optical spectroscopy in probing electronic excitations of different symmetries and deepens the understanding of the coupling between electronic structure and magnetic mechanisms in such geometrically frustrated quantum antiferromagnets.\n12. Checkerboard Bose Hubbard Ladders using Transmon Arrays Relevance Score: 3.4721 Authors: Pranjal Praneel, Thomas G Kiely, Andre G Petukhov, Erich J Mueller Affiliations: Google Quantum AI, University of California, Santa Barbara, Cornell University Link: http://arxiv.org/abs/2605.07906v1 Summary: This paper proposes the implementation of a checkerboard Bose-Hubbard ladder model using transmon arrays, where sublattice detuning is introduced to enrich physical phenomena and enhance experimental operability. Methodologically, the authors treat the nonlinear quantum energy levels of transmons as particle occupation numbers and interactions in the Bose-Hubbard model, realize particle hopping via capacitive coupling, and adjust the energies of different lattice sites through sublattice detuning. The study focuses on ladder geometries ranging from one-dimensional to two-dimensional transitions (from single-leg to multi-leg configurations), analyzing the case of one particle per lattice site. By adiabatically evolving from an insulating state (a product state under deep detuning) while gradually increasing the coupling, superfluid states are prepared, and physical quantities such as localization length, energy gap, and polarization are measured. Results indicate that sublattice detuning brings the commensurate superfluid phase into an experimentally accessible parameter regime and provides new probing methods. The insulating states exhibit rich structures, where the polarization vector can serve as a topological invariant to distinguish different phases; notably, the insulating phase of two-leg ladders shows exceptional robustness. Finite-size effects are carefully considered, and the relationship between the adiabatic preparation time scale and system scaling is discussed. This work offers a feasible roadmap for simulating strongly correlated bosonic systems on superconducting quantum processors.\n13. Nonadiabatic Theory of Phonon Magnetic Moments in Insulators and Metals Relevance Score: 3.4264 Authors: Haoran Chen, Wenqin Chen, Kaijie Yang, Ting Cao, Di Xiao Link: http://arxiv.org/abs/2605.06983v1 Summary: This paper develops a non-adiabatic theory of phonon magnetic moments applicable to both insulators and metals. By linking the phonon magnetic moment to the force-velocity response of ions in a magnetic field and employing a gauge-covariant Wigner expansion, we derive a gauge-invariant expression. The theory naturally separates Fermi sea and Fermi surface contributions and fully captures the frequency dependence of phonons. In the low-frequency limit for gapped systems, the theory reduces to the conventional adiabatic approximation; in the high-frequency regime or metallic systems, it reveals additional contributions from resonant interband transitions and the Fermi surface. Applying the theory to the doped topological crystalline insulator Pb₁₋ₓSnₓTe, we find that Fermi surface contributions significantly enhance the phonon magnetic moment, reaching the same order of magnitude (approximately 10⁻⁵ μ_B/atom) as experimental observations. Specifically, in narrow-gap insulators, non-adiabatic effects lead to resonant enhancement and even sign reversal of the magnetic moment when the phonon frequency approaches the band gap; in the metallic state, the Fermi surface contribution rapidly dominates with increasing carrier concentration and exhibits an approximately 1/ω² dependence on frequency. These results explain the experimentally observed growth trend of the phonon magnetic moment with Sn doping concentration and indicate that non-adiabatic effects and Fermi surface processes are key to understanding phonon magnetic moments, providing a complete theoretical framework for a unified description of phonon magnetic moments in insulators and metals.\n14. Topological superconductivity in a Hubbard model for twisted bilayer cuprates Relevance Score: 3.3964 Authors: T. Vibert, D. Sénéchal Link: http://arxiv.org/abs/2605.06923v1 Summary: This study explores topological superconductivity in twisted cuprate bilayers within the weak interaction regime using the Hubbard model. The superconducting order parameters are solved via the variational cluster approximation (VCA), and the Chern numbers are calculated using Green\u0026rsquo;s function-based topological invariants. At an interaction strength of ( U/t = 3.85 ), non-trivial topology emerges in the electron-doped (above half-filling) region, with a Chern number of ±8, while the hole-doped (below half-filling) region exhibits a zero Chern number, indicating that the topological properties are highly dependent on the doping level. Furthermore, the edge spectral function is computed in a finite-width strip geometry, revealing eight chiral edge modes crossing the Fermi level on the electron-doped side, consistent with the bulk Chern number and confirming the existence of a topological superconducting state. This work demonstrates that, in the weak interaction regime below the Mott transition, the twisted bilayer Hubbard model can realize a superconducting state with non-trivial topology under electron doping, whereas strong correlation effects destroy the topology. These findings provide a microscopic theoretical basis for understanding possible topological phases in high-temperature superconductors.\n15. Spin-lattice coupling enables adaptive adsorption in magneticallydriven electrocatalysts Relevance Score: 3.3811 Authors: Arnold Gaje, Lulu Li, Felipe A. Garcés-Pineda, Camilo A. Mesa, Ghazaleh Abdolhosseini, Aditya K. Kushwaha, Dora Zalka, Elzbieta Trzop, Nicolas Godin, Raffaella Torchio, María Escudero-Escribano, Eric Collet, Sixto Giménez, Niels Keller, José Ramón Galán-Mascarós, Núria López, Ernest Pastor Affiliations: Universitat Jaume I, European Synchrotron Radiation Facility, CNRS, Universitat Rovira i Virgili, ICREA, Institute of Chemical Research of Catalonia (ICIQ-CERCA), Catalan Institute of Nanoscience and Nanotechnology (ICN2) Link: http://arxiv.org/abs/2605.07437v1 Summary: This study finds that in Ni-Fe oxyhydroxide electrocatalysts, applying an external magnetic field can alter surface chemisorption through spin-lattice coupling, thereby relaxing the linear scaling relationship among intermediates in the oxygen evolution reaction (OER). Density functional theory (DFT) simulations reveal the presence of multiple quasi-degenerate oxygen-containing intermediates on the catalyst surface, which exhibit different spin states (high-spin vs. low-spin) and oxidation state distributions (e.g., Ni-ox, Fe-ox, O-ox, etc.), with their relative stability significantly influenced by spin configuration. By combining reaction pathways of different spin states, the theoretical overpotential can be reduced from 0.44 eV (high-spin) or 0.26 eV (low-spin) for a single spin state to 0.29 eV, indicating that spin regulation can effectively decouple intermediate energetics. Experimentally, electrochemical measurements show that upon applying a 0.7 T magnetic field, the OER current density is enhanced at potentials \u0026gt;1.75 V_RHE, and the variation of current with magnetic field intensity is highly correlated with the magneto-optical Faraday response, exhibiting hysteresis loop characteristics similar to ferromagnetic materials, thereby indicating that the magnetization state of the electrode directly affects electrochemical reaction kinetics. UV-visible spectroelectrochemical measurements further confirm that the magnetic field alters the population distribution of intermediates. Integrating theoretical calculations and experiments, this work redefines the traditionally perceived linear scaling limitation as projection-dependent rather than intrinsic, and demonstrates that external magnetic field stimulation is a feasible strategy to modulate electrocatalytic reaction pathways in a multi-state energy landscape, reduce overpotential, while providing a framework for the application of other external stimuli.\n16. Epitaxial growth of beta-bismuthene on Sb2Te3 Relevance Score: 3.3593 Authors: Giorgia Sementilli, Arslan Masood, Fabio Ronci, Stefano Colonna, Marilena Carbone, Marco Papagno, Ziya S. Aliev, Evgueni V. Chulkov, Sergey V. Eremeev, and Roberto Flammini Link: http://arxiv.org/abs/2605.07700v1 Summary: This study successfully fabricated β-bismuthene heterointerfaces on the (0001) surface of the three-dimensional topological insulator Sb₂Te₃ using molecular beam epitaxy. The effects of bismuth coverage and substrate temperature on nucleation processes, island morphology, and atomic structure were systematically investigated via scanning tunneling microscopy (STM). Under room-temperature deposition conditions, islands began to coalesce and form triangular structures with well-defined zigzag edges at a bismuth coverage of approximately 0.5 bilayer (BL), marking the formation of β-bismuthene. At a coverage of 1 BL, the influence of substrate temperature (room temperature, 200 K, and 150 K) on island morphology was further examined: at room temperature, islands exhibited uniform triangular shapes; at 200 K, island edges became blurred and shapes irregular, attributed to reduced adatom mobility; at 150 K, a high density of small islands formed, with 1 BL islands remaining irregular while 2 BL islands appeared triangular due to templating by the ordered first-layer islands. Atomically resolved STM images confirmed that bismuthene islands grown at all temperatures displayed a hexagonal honeycomb structure (lattice constant ~0.43 nm) perfectly matched to the Sb₂Te₃ substrate, with an apparent island height of ~0.5 nm, consistent with freestanding β-bismuthene bilayers. Additionally, replication of electronic state perturbations originating from intrinsic substrate defects (e.g., Sb antisites and Te vacancies) was observed in the bismuthene islands, indicating a high-quality epitaxial relationship at the interface. This work achieves, for the first time, the β-bismuthene/Sb₂Te₃ van der Waals heterojunction, providing an ideal platform for studying two-dimensional/topological insulator interfaces and proximity effects.\n17. Quantum spin liquid on a 3D bipartite lattice of spin trimers stabilized by enhanced effective anisotropy Relevance Score: 3.3209 Authors: M. Gomilšek, L. Mangin-Thro, T. Arh, S. Petit, B. Grenier, V. Simonet, M. Pregelj, A. Zorko, B. Koteswararao, B. -G. Jeon, B. Sana, Y. Furukawa, Y. Inagaki, T. Asano, C. Repellin, B. Fåk, J. Ollivier, F. Fauth, C. V. Colin, E. Pachoud, V. Pomjakushin, J. S. Lord, H. Luetkens, K. -H. Kim, P. Khuntia Link: http://arxiv.org/abs/2605.06752v1 Summary: This study reports a candidate material for quantum spin liquid on a three-dimensional bipartite lattice, KBCVO (KBa₃Ca₄Cu₃V₇O₂₈). Strongly coupled Cu²⁺ trimers condense into effective spin-1/2 pseudospins upon cooling, forming a three-dimensional bipartite network. Through comprehensive experimental approaches including thermodynamic measurements, neutron scattering, μSR, and NMR, no spin freezing or symmetry-breaking phase transitions were detected down to 20 mK; instead, a gapless dynamical ground state was observed, with spin correlations exhibiting algebraic decay. Monte Carlo and exact diagonalization calculations indicate that this quantum spin liquid state is stabilized by a significant enhancement of effective anisotropy: the microscopic Cu-Cu exchange anisotropy (approximately 15%) is amplified to effective anisotropy between pseudospins (60–100%) at the trimer level, thereby realizing an anisotropy-stabilized quantum entangled state in a three-dimensional bipartite system with only weak microscopic anisotropy. This finding establishes a quantum spin liquid platform based on trimer networks and expands the pathways for realizing quantum spin liquids.\n18. Anisotropic Defect Diffusion in Layered CsPbBr$_\\mathrm{x}$I$_\\mathrm{3-x}$ Perovskites Relevance Score: 3.2760 Authors: Konrad Wilke, Mike Pols, Titus S. van Erp, Geert Brocks, Shuxia Tao Link: http://arxiv.org/abs/2605.08055v1 Summary: This study employed large-scale molecular dynamics simulations with a reactive force field (ReaxFF) to systematically investigate the diffusion behavior of defects in layered ordered CsPbBrₓI₃₋ₓ perovskite, and compared it with randomly mixed structures and pure CsPbI₃/CsPbBr₃ systems. The simulations tracked the migration pathways of cesium vacancies, cesium interstitials, as well as halogen vacancies and interstitials, and anisotropic diffusion coefficients were obtained by calculating the mean square displacement. The main finding is that the layered ordered arrangement of halide ions (e.g., od-CsPbBr₂I and od-CsPbBrI₂) introduces strong anisotropic strain, leading to significant direction-dependent defect diffusion—migration along the halogen layers (in-plane) is facile, while diffusion across layers (out-of-plane) is strongly suppressed. For cesium defects, this anisotropy originates from the directional lattice strain induced by the layered structure: the tilt patterns of adjacent lead-halide octahedra (PbI₄X₂ layers exhibit checkerboard tilting, while PbBr₄X₂ layers are nearly untilted) lock the Pb-I-Pb bond angles, hindering the \u0026ldquo;gate-opening\u0026rdquo; octahedral rearrangement required for cesium jumps across layers; applying biaxial compressive strain to pure CsPbI₃ reproduces the same tilt pattern and diffusion anisotropy, confirming strain as the dominant factor. For halogen defects, the diffusion anisotropy is jointly determined by strain and local halogen bonding tendencies: along the layer direction, differences in Pb-Br and Pb-I bonds affect migration energy barriers; across-layer migration is impeded by strain gradients and changes in the chemical environment. This work reveals the atomic-scale mechanisms by which layered halogen ordering or strain engineering controls ion migration, providing strategies for enhancing the phase stability of mixed-halide perovskites and tuning their optoelectronic properties.\n19. Majorana bound states in chiral ferromagnet-superconductor heterostructures revisited Relevance Score: 3.2098 Authors: A. S. Slobodskoi, S. S. Apostoloff, I. S. Burmistrov Link: http://arxiv.org/abs/2605.06828v1 Summary: This work presents a comprehensive theoretical analysis of Majorana bound states in chiral ferromagnet-superconductor heterostructures. Within the Bogoliubov–de Gennes framework, we develop an analytical theory applicable to superconducting vortices and skyrmion-vortex pairs, obtaining expressions for the wavefunctions and energy spectra of Majorana states as well as other low-energy bound states. The study explicitly reveals the crucial role of spin-orbit coupling for the existence of Majorana states: without spin-orbit coupling, no localized Majorana zero modes can form at the vortex core. Our derived conditions show that only when the spin-orbit coupling strength exceeds a certain threshold do the equations admit three exponentially decaying solutions, thereby supporting Majorana states. The analytical results are in excellent agreement with numerical simulations. Furthermore, we evaluate the effects of practical factors, including the vector potential generated by the superconducting vortex, the vector potential induced by the skyrmion magnetic texture, and the perturbation of the magnetic texture by stray fields. These results provide important theoretical guidance for realizing topological quantum computing based on skyrmion-vortex pairs.\n20. Ground states of quantum XY dipoles on the Archimedean lattices Relevance Score: 3.1050 Authors: Marcus Bintz, Ahmed Khalifa, Vincent S. Liu, Johannes Hauschild, Michael P. Zaletel, Shubhayu Chatterjee, Norman Y. Yao Link: http://arxiv.org/abs/2605.07685v1 Summary: This paper investigates the ground-state properties of the quantum XY dipolar model on nine of the eleven Archimedean lattices through large-scale density matrix renormalization group (DMRG) calculations. The model describes extended antiferromagnetic interactions in two-dimensional arrays of polar molecules and Rydberg atoms. The study reveals that the ground states on these lattices can be classified into two categories: four lattices (e.g., hexagonal, truncated square) exhibit trivial paramagnetic states composed of local singlets, while another four lattices (e.g., square, truncated trihexagonal) display collinear Néel antiferromagnetic order with a clear alternating sign structure in long-range correlations. For the ordered states, the authors compute hydrodynamic parameters such as magnetization, magnetic susceptibility, and spin stiffness, and compare them with results from linear spin-wave theory. The two approaches show qualitative agreement on most lattices; however, an instability arises in linear spin-wave theory on the snub square lattice, suggesting the possible existence of incommensurate order. The triangular lattice exhibits special behavior with multiple competing phases, including coplanar magnetic order, stripe density wave order, and a possible spin liquid phase, whose relative stability is sensitive to the truncation scheme of long-range couplings. Finally, the Kagome lattice, as a complement to the Archimedean classification, is argued in a companion work to realize a Dirac spin liquid. This study systematically reveals the decisive role of geometric arrangement in the ground state of the dipolar XY model.\n","permalink":"https://nickelates.uk/en/posts/2026-05-11-arxiv-daily/","summary":"\u003cblockquote\u003e\n\u003cp\u003e\u003cstrong\u003eDaily Overview\u003c/strong\u003e:\u003c/p\u003e\n\u003ch1 id=\"todays-quick-overview-of-the-ni-based-superconductor-field--among-todays-submissions-no-research-papers-directly-targeting-nickel-based-superconductors-were-found-however-several-works-have-made-important-progress-in-closely-related-directions-such-as-superconducting-mechanisms-strongly-correlated-electron-systems-and-topological-superconductivity-offering-potential-insights-for-nickel-based-superconductor-research--1-cuprate-superconductivity-theory-a-work-systematically-studying-the-three-band-emery-model-via-the-dynamical-vertex-approximation-da-is-noteworthy-the-study-points-out-that-traditional-simplified-models-are-insufficient-for-quantitatively-describing-the-cuprate-superconducting-phase-diagram-instead-the-full-set-of-long-range-hopping-parameters-derived-from-first-principles-must-be-included-to-obtain-a-superconducting-dome-doping-range-722-and-d-wave-order-parameter-consistent-with-experiments-given-the-electronic-structure-similarities-between-nickel-based-superconductors-and-cuprates-this-methodology-has-direct-reference-value-for-theoretical-modeling-of-nickel-based-superconductors--2-topological-superconductivity-in-twisted-bilayer-hubbard-model-a-study-using-the-variational-cluster-approximation-investigates-topological-superconductivity-in-twisted-cuprate-bilayers-it-reveals-that-in-the-weak-interaction-regime-below-the-mott-transition-the-electron-doped-side-can-realize-nontrivial-topological-superconducting-states-with-chern-numbers-up-to-8-while-the-hole-doped-side-remains-topologically-trivial-this-microscopic-mechanism-provides-a-theoretical-framework-for-exploring-possible-topological-phases-in-nickel-based-superconductors--3-pair-density-wave-in-altermagnets-a-non-perturbative-monte-carlo-study-reveals-that-d-wave-altermagnets-can-stabilize-finite-momentum-superconductivity-pair-density-wave-without-requiring-an-external-magnetic-field-this-originates-from-the-momentum-dependent-spin-splitting-which-effectively-enhances-pairing-at-finite-center-of-mass-momentum-while-suppressing-the-uniform-superconducting-channel-this-mechanism-offers-a-new-perspective-for-understanding-possible-incommensurate-superconducting-orders-in-nickel-based-superconductors--4-theory-of-majorana-bound-states-an-analytical-theoretical-work-on-chiral-ferromagnetsuperconductor-heterostructures-clarifies-the-crucial-role-of-spin-orbit-coupling-for-the-existence-of-majorana-zero-modes-and-provides-the-threshold-condition-for-the-spin-orbit-coupling-strength-these-results-have-theoretical-guiding-significance-for-designing-topological-quantum-computing-platforms-based-on-nickel-based-superconductors--summary-although-no-studies-directly-targeting-nickel-based-superconductors-were-submitted-today-theoretical-advances-in-directions-such-as-multi-orbital-models-for-cuprates-topological-superconductivity-in-twisted-bilayers-and-pair-density-waves-in-altermagnets-provide-important-inspiration-for-refined-modeling-topological-state-exploration-and-understanding-of-unconventional-superconducting-mechanisms-in-nickel-based-superconductor-systems-meriting-the-attention-of-researchers-in-the-field\"\u003eToday\u0026rsquo;s Quick Overview of the Ni-Based Superconductor Field \u0026gt; Among today\u0026rsquo;s submissions, \u003cstrong\u003eno research papers directly targeting nickel-based superconductors\u003c/strong\u003e were found. However, several works have made important progress in closely related directions such as superconducting mechanisms, strongly correlated electron systems, and topological superconductivity, offering potential insights for nickel-based superconductor research: \u0026gt; 1. \u003cstrong\u003eCuprate Superconductivity Theory\u003c/strong\u003e: A work systematically studying the three-band Emery model via the dynamical vertex approximation (DA) is noteworthy. The study points out that traditional simplified models are insufficient for quantitatively describing the cuprate superconducting phase diagram; instead, the full set of long-range hopping parameters derived from first principles must be included to obtain a superconducting dome (doping range 7–22%) and d-wave order parameter consistent with experiments. Given the electronic structure similarities between nickel-based superconductors and cuprates, this methodology has direct reference value for theoretical modeling of nickel-based superconductors. \u0026gt; 2. \u003cstrong\u003eTopological Superconductivity in Twisted Bilayer Hubbard Model\u003c/strong\u003e: A study using the variational cluster approximation investigates topological superconductivity in twisted cuprate bilayers. It reveals that in the weak-interaction regime below the Mott transition, the electron-doped side can realize nontrivial topological superconducting states with Chern numbers up to ±8, while the hole-doped side remains topologically trivial. This microscopic mechanism provides a theoretical framework for exploring possible topological phases in nickel-based superconductors. \u0026gt; 3. \u003cstrong\u003ePair-Density Wave in Altermagnets\u003c/strong\u003e: A non-perturbative Monte Carlo study reveals that d-wave altermagnets can stabilize finite-momentum superconductivity (pair-density wave) without requiring an external magnetic field. This originates from the momentum-dependent spin splitting, which effectively enhances pairing at finite center-of-mass momentum while suppressing the uniform superconducting channel. This mechanism offers a new perspective for understanding possible incommensurate superconducting orders in nickel-based superconductors. \u0026gt; 4. \u003cstrong\u003eTheory of Majorana Bound States\u003c/strong\u003e: An analytical theoretical work on chiral ferromagnet–superconductor heterostructures clarifies the crucial role of spin-orbit coupling for the existence of Majorana zero modes and provides the threshold condition for the spin-orbit coupling strength. These results have theoretical guiding significance for designing topological quantum computing platforms based on nickel-based superconductors. \u0026gt; \u003cstrong\u003eSummary\u003c/strong\u003e: Although no studies directly targeting nickel-based superconductors were submitted today, theoretical advances in directions such as multi-orbital models for cuprates, topological superconductivity in twisted bilayers, and pair-density waves in altermagnets provide important inspiration for refined modeling, topological state exploration, and understanding of unconventional superconducting mechanisms in nickel-based superconductor systems, meriting the attention of researchers in the field.\u003c/h1\u003e\u003c/blockquote\u003e\n\u003ch2 id=\"1-breaking-the-trade-off-bulk-2d-ising-superconductivity-with-high-tc-and-giant-interlayer-spacing-via-a-unique-chain-intercalation-in-bas13tas2\"\u003e1. Breaking the Trade-off: Bulk 2D Ising Superconductivity with High Tc and Giant Interlayer Spacing via a Unique Chain Intercalation in (BaS)1/3TaS2\u003c/h2\u003e\n\u003cul\u003e\n\u003cli\u003e\u003cstrong\u003eRelevance Score\u003c/strong\u003e: \u003ccode\u003e4.3582\u003c/code\u003e\u003c/li\u003e\n\u003cli\u003e\u003cstrong\u003eAuthors\u003c/strong\u003e: Ziyi Zhu, Leiming Chen, Xiangqi Liu, Haonan Wang, Chen Xu, Ze Yan, Zhengyang Li, Wei Xia, Jiawei Luo, Na Yu, Xia Wang, Ke Qu, Zhenzhong Yang, Yanfeng Guo\u003c/li\u003e\n\u003cli\u003e\u003cstrong\u003eAffiliations\u003c/strong\u003e: East China Normal University, ShanghaiTech University, Zhengzhou University of Aeronautics\u003c/li\u003e\n\u003cli\u003e\u003cstrong\u003eLink\u003c/strong\u003e: \u003ca href=\"http://arxiv.org/abs/2605.07336v1\"\u003ehttp://arxiv.org/abs/2605.07336v1\u003c/a\u003e\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003e\u003cstrong\u003eSummary\u003c/strong\u003e: This paper reports the synthesis of a new polymorph, (BaS)₁/₃TaS₂, via a unique chain-like intercalation strategy, which successfully overcomes the long-standing trade-off between high superconducting transition temperature (Tc) and increased interlayer spacing/enhanced two-dimensionality in conventional intercalation systems. In this structure, Ba-S-S-Ba chains are inserted between TaS₂ bilayers, forming locally decoupled two-dimensional superconducting layers with an interlayer spacing of 12.75 Å, more than three times that of pristine 2H-TaS₂. This structural configuration breaks the bulk c-axis mirror symmetry, significantly suppresses interlayer electronic coupling, and renders local inversion symmetry breaking within individual TaS₂ layers dominant, thereby avoiding the compensation of the Ising spin–orbit field in the centrosymmetric bulk and realizing robust bulk two-dimensional Ising superconductivity. Comprehensive transport, magnetic, and thermodynamic measurements confirm that (BaS)₁/₃TaS₂ exhibits an enhanced Tc, an in-plane upper critical field far exceeding the Pauli limit, and pronounced superconducting anisotropy, demonstrating the successful coexistence of high Tc with large interlayer spacing/high two-dimensionality. This work establishes a generic intercalation framework for designing bulk two-dimensional Ising superconductors, offering a new route to reconcile competing demands in materials and expanding the scope of Ising superconductivity research.\u003c/p\u003e","title":"arXiv Daily: Nickelate superconductors 2026-05-11"},{"content":" Daily Overview: No relevant papers have been published in the field of nickel-based superconductivity today.\n1. Pair-Breaking and Dimensionality in Spin-Orbit Coupled Superconductors Relevance Score: 4.5787 Authors: Reiley Dorrian, Mizuki Ohno, Elena Williams, Adrian Llanos, Joseph Falson Link: http://arxiv.org/abs/2605.06514v1 Summary: This paper employs the multi-mechanism Kharitonov-Feigel’man (KF) framework to analyze the thickness-dependent superconductivity in spin-orbit-coupled superconducting thin films of LaBi₂, and systematically compares it with the conventional Klemm-Luther-Beasley (KLB) model. A series of high-quality single-crystal films ranging from the “bulk” to the ultrathin limit (2.1 nm) were prepared by molecular beam epitaxy, and the temperature-dependent upper critical fields were measured under parallel magnetic fields. In contrast to the KLB model, which only considers paramagnetic pair-breaking, the KF framework simultaneously incorporates three mechanisms: orbital pair-breaking, paramagnetic effects, and magnetic scattering (spin-exchange scattering). An anomalous enhancement of the critical field was observed in the ultrathin limit (2.1 nm), attributed to the suppression of magnetic fluctuations by the magnetic field, which effectively reduces the spin-exchange scattering rate. Through fitting with the KF model, the contributions of each scattering channel were successfully isolated: the magnetic scattering time is on the order of 10⁻¹²–10⁻¹¹ seconds, while the KLB model, due to its neglect of orbital pair-breaking, severely overestimates the spin-orbit scattering time (by up to four orders of magnitude) at finite thickness and is meaningful only in the zero-thickness limit. The study also reveals differences among three distinct definitions of the zero-field critical temperature (experimental value, KLB extrapolated value, and KF value without magnetic impurities), and emphasizes that the determination of the Pauli limit should be extrapolated to the strictly two-dimensional limit. The results indicate that the KLB model, by ignoring magnetic disorder and orbital effects, introduces systematic biases in the interpretation of fundamental superconducting parameters (such as critical temperature and Pauli limit), whereas the KF framework provides a more accurate deconstruction of pair-breaking mechanisms in two-dimensional superconductors, offering new insights into the relationship between scattering times and superconductivity.\n2. Superconducting and correlated phases of an effective Hubbard model on the BCC lattice Relevance Score: 4.0572 Authors: Theja N. De Silva Link: http://arxiv.org/abs/2605.06422v1 Summary: This paper investigates the electronic phases of an effective Hubbard model on a body-centered cubic lattice, motivated by alkali-doped fullerene molecular solids. The model incorporates a renormalized on-site interaction and an effective inverse Hund coupling arising from electron-phonon interactions. To cover different interaction regimes, two theoretical approaches are employed. In the intermediate coupling regime, the on-site repulsion is approximated as a long-range interaction in momentum space, yielding an exactly solvable Komatsu–Kawamoto model supplemented with a BCS-type pairing term. Within this framework, the superconducting instability is analyzed, revealing a first-order normal-to-superconducting phase transition characterized by a discontinuous jump in the order parameter. In the strong coupling regime, pairing fluctuations are neglected and a spin-rotation-invariant slave-boson formalism is applied, resulting in a temperature–interaction phase diagram that displays first-order transitions among a Fermi liquid phase, an antiferromagnetic phase, and a Mott insulator phase, along with a narrow intermediate region where all three phases compete. The phase diagram captures the interplay of itinerancy, magnetic order, and Mott localization in a three-dimensional system, providing a unified perspective on superconductivity and correlation-driven phenomena in fullerene lattice systems.\n3. Superconductivity mediated by nematic fluctuations \u0026ndash; the dispersion of collective modes Relevance Score: 3.9201 Authors: Kazi Ranjibul Islam, Andrey Chubukov Link: http://arxiv.org/abs/2605.05433v1 Summary: This paper investigates the collective excitation spectrum of superconductors mediated by long-range nematic fluctuations. The authors derive the pair susceptibility χ(q,Ω) at finite momentum and frequency in the superconducting phase, and analyze the spectral function Imχ(q,Ω) and its pole structure in both the transverse (phase) and longitudinal (amplitude) channels. The study reveals that the analytical structure of the pair susceptibility in this system differs fundamentally from that of conventional BCS superconductors, leading to highly unconventional dispersion relations for the phase and amplitude collective modes. Specifically: in the transverse channel (neglecting Coulomb interactions), no sharp mode exists, but Imχ(q,Ω) exhibits two peaks at specific angles of the momentum direction relative to the Fermi surface; these peaks merge at a certain momentum while remaining damped. In the longitudinal channel, at zero momentum, Imχ(q,Ω) is nonzero at all frequencies and displays a bilateral logarithmic singularity at the maximum gap, while Reχ jumps and diverges at a frequency-dependent point; at finite momentum, the logarithmic singularity splits into two, with Reχ undergoing a finite jump at the corresponding frequencies. These features are markedly different from those in conventional gapped and nodal superconductors (e.g., s-wave and d-wave) and are expected to be observable via spectroscopic techniques such as Raman scattering or terahertz conductivity. Based on FeSe and its doped systems, this work assumes pairing mediated by nematic fluctuations and employs a single-band model with an effective interaction. By solving the nonlinear gap equation, a highly anisotropic s-wave gap (exponentially small in four cold regions of the Fermi surface) is obtained, and the collective modes are computed using the Gorkov diagrammatic method. This study deepens the understanding of collective excitations in unconventional superconductors.\n4. Josephson spectroscopy study of kagome superconductors toward the deep point-contact regime Relevance Score: 3.8807 Authors: Hailang Qin, Xiao-Yu Yan, Hanbin Deng, Mu-Wei Gao, Guowei Liu, Yuanyuan Zhao, Jia-Xin Yin Affiliations: Quantum Science Center of Guangdong-Hong Kong-Macao Greater Bay Area, Southern University of Science and Technology Link: http://arxiv.org/abs/2605.06150v1 Summary: This paper systematically investigates the Josephson spectroscopy behavior of kagome superconductors in the deep point-contact regime. By employing a dilution refrigerator scanning tunneling microscope and reducing the junction resistance between the superconducting tip and the samples (Cs(V₀.₈₆Ta₀.₁₄)₃Sb₅ and KV₃Sb₅) to as low as 0.15 h/2e² (approximately 2 kΩ), the experiment achieves a transition from the tunneling regime to the point-contact regime. Measurements reveal that the zero-bias conductance (ZBC) exhibits an approximate quadratic increase when the normal-state conductance is relatively small; however, upon entering the deep point-contact regime, the ZBC rapidly deviates from the quadratic dependence and eventually saturates. By analyzing the series resistance (approximately 5.3 kΩ) in the circuit, it is confirmed that this saturation originates from the dominance of the series resistance in the measurement loop, rather than the intrinsic Josephson current saturation. This finding provides a crucial caution for interpreting ZBC saturation or quantization phenomena (e.g., in studies of Majorana zero modes) under extremely low junction resistance conditions. Furthermore, the study identifies the optimal operating range of JSTM as an atomic-scale probe: by avoiding the deep point-contact regime, it can stably detect the pair density wave state in low superconducting transition temperature kagome superconductors (such as AV₃Sb₅), thereby offering a reliable experimental approach for the microscopic investigation of such exotic quantum states.\n5. Tuning charge-transport properties and magnetic order in metallic EuTiO$_{3-δ}$ Relevance Score: 3.7902 Authors: Xing He, Chiou Yang Tan, Issam Khayr, Zach Van Fossan, Richard J. Spieker, Dayu Zhai, Sarah Anderson, Dinesh Shukla, Suchismita Sarker, Javier Garcia-Barriocanal, Turan Birol, Martin Greven Affiliations: UGC-DAE Consortium for Scientific Research, Cornell University, University of Minnesota Link: http://arxiv.org/abs/2605.05612v1 Summary: By using CaH₂ as an oxygen getter, we prepared oxygen-vacancy-doped metallic EuTiO₃₋δ single crystals, achieving a higher carrier concentration than previously reported. We systematically investigated their charge transport and magnetic properties, revealing that the phase diagram of oxygen-vacancy doping differs from that of cation doping: in the metallic state, the magnetic order transitions from antiferromagnetic to ferromagnetic, with a Curie temperature of approximately 11 K at the highest carrier concentration of about 10²¹ cm⁻³. Density functional theory (DFT+U) calculations indicate that the nearest-neighbor magnetic exchange constant changes significantly with increasing electron doping. X-ray diffuse scattering experiments and first-principles calculations reveal that, similar to SrTiO₃, the diffuse scattering in EuTiO₃ is primarily dominated by thermal diffuse scattering, with no quasi-elastic scattering. Specific heat measurements confirm the magnetic transition temperatures obtained from magnetization measurements and support the lattice dynamics picture derived from the diffuse scattering data.\n6. Emergence of a correlated insulating state in bulk 1T-NbSe$_2$ via metal intercalation Relevance Score: 3.7639 Authors: M. Tomlinson, AKM A. Rahman, S. Devi, R. Tuchikawa, M. Ishigami, D. Le, Md Z. Mohayman, A. Kushima, Y. Nakajima Affiliations: University of Central Florida Link: http://arxiv.org/abs/2605.06545v1 Summary: Through electrochemical tin intercalation, the 1T phase, previously limited to monolayer form, has been successfully achieved in bulk NbSe₂. Transmission electron microscopy directly confirms that tin intercalation induces a structural transition from 2H to 1T. Transport measurements reveal that the intercalated samples exhibit insulating behavior, in stark contrast to the metallic 2H-NbSe₂; the resistivity shows an insulating state at low temperatures, with a small superconducting peak at around 7 K, which is attributed to residual 2H phase regions. Density functional theory calculations, however, predict a metallic band structure, indicating that the observed insulating state is not caused by disorder but rather originates from electron correlation effects, similar to the Mott insulator in 1T-TaS₂. Raman spectroscopy further reveals vibrational modes associated with tin intercalation and possible charge density wave order. These results establish electrochemical intercalation as an effective strategy to stabilize previously inaccessible bulk polytype phases, making bulk 1T-NbSe₂ a new platform for investigating correlated electronic states.\n7. Disentangling magnetic and optical contributions in ultrafast dynamics of antiperovskite non-collinear antiferromagnets Relevance Score: 3.7413 Authors: J. Kimak, Tomas Ostatnicky, M. Nerodilova, F. Johnson, O. Faiman, T. Trejtnar, D. Boldrin, F. Rendell-Bhatti, J. Zemen, B. Zou, A. P. Mihai, X. Sun, F. Yu, E. Schmoranzerova, L. Nadvornik, L. F. Cohen, P. Nemec Link: http://arxiv.org/abs/2605.06233v1 Summary: This paper investigates the ultrafast dynamics of antiperovskite noncollinear antiferromagnetic metal films Mn₃NiN and Mn₃GaN using pump-probe techniques. Both materials exhibit dynamics independent of pump polarization, yet strongly dependent on the angle between the sample normal and the probe light direction. Through polarization-resolved measurements combined with optical modeling based on Yeh\u0026rsquo;s formalism, the magnetic and nonmagnetic contributions to the signal are quantitatively separated. In Mn₃NiN (Γ4g phase), which exhibits a significant anomalous Hall effect (AHE), the magneto-optical signal displays a pronounced magnetic field dependence when the probe light is incident at a non-zero angle; in contrast, the signal in Mn₃GaN (Γ5g phase), which lacks AHE, is independent of the magnetic field. The results indicate that the magnetic field dependence in Mn₃NiN originates from field-controlled redistribution of magnetic domain populations via the piezomagnetic effect, detected through a magneto-optical mechanism analogous to the Kerr effect, while this effect is absent in Mn₃GaN. Temperature-dependent measurements reveal that the demagnetization dynamics in Mn₃NiN transition from a single-step to a two-step process with increasing temperature, contrasting with the nearly temperature-independent demagnetization behavior in the noncollinear Heusler compound Mn₃Sn, but resembling the crossover from type I to type II demagnetization dynamics in metallic ferromagnets. This work provides key insights into the origin of ultrafast magneto-optical signals and the mechanisms of magnetic order quenching in noncollinear antiferromagnets.\n8. Tunable Interlayer Charge-transfer States in MoSe$_2$/WS$_2$ Moiré Superlattices Relevance Score: 3.7272 Authors: Zheyu Lu, Jiahui Nie, Tianle Wang, Rwik Dutta, Ruishi Qi, Jingxu Xie, Can Uzundal, Jianghan Xiao, Ziyu Wang, Yibo Feng, Kenji Watanabe, Takashi Taniguchi, James R. Chelikowsky, Archana Raja, Steven G. Louie, Mit H. Naik, Michael P. Zaletel, Feng Wang Affiliations: University of California at Berkeley, Lawrence Berkeley National Laboratory, The University of Texas at Austin, National Institute for Materials Science Link: http://arxiv.org/abs/2605.05571v1 Summary: By combining large-scale first-principles calculations with optical reflectance spectroscopy, this paper systematically investigates the emergent interlayer charge-transfer states in electron-doped angle-aligned MoSe₂/WS₂ moiré superlattices. The study reveals that by tuning the heterojunction band alignment from type I to type II via a vertical electric field, a series of interlayer charge-transfer transitions from n/n₀ = 1 to 4 (where n₀ is the moiré density) can be observed. Moiré exciton states serve as sensitive optical probes to detect the localization distribution of doped electrons. Under the application of a vertical electric field, interlayer electron localization is precisely controlled, realizing a Fermi-Hubbard model with tunable charge-transfer bands on an effective honeycomb lattice. Monte Carlo simulations further predict the emergence of various correlated charge-ordered states at both integer and fractional fillings. This work reveals the nature of emergent optical excitations and correlated charge-transfer states in electron-doped MoSe₂/WS₂ moiré superlattices.\n9. Anomalous Thomson Effect Relevance Score: 3.5859 Authors: Ying-Fei Zhang, Zhi-Fan Zhang, Zhen-Gang Zhu, Gang Su Link: http://arxiv.org/abs/2605.06299v1 Summary: This paper proposes a new effect called the anomalous Thomson effect (ATE), conceptually analogous to the anomalous Hall effect and the anomalous Nernst effect (ANE). Based on Berry curvature-driven anomalous transport, the anomalous Thomson coefficient (ATC) is theoretically derived as a function of the anomalous Nernst coefficient (ANC) and its temperature derivative. Consequently, ATE shares the same physical origin as ANE but exhibits distinct behavior. By constructing a giant Dirac model for Fe₃Sn₂ and employing the Boltzmann transport equation, Berry curvature-related transport coefficients are calculated. It is found that ATC is generally larger than ANC, and the ATC/ANC ratio approaches 3 in the low-temperature limit. Since the relationship between ATE and ANE is model-independent, this study infers the ATC values for CoS₂, Co₃Sn₂S₂, and CeCrGe₃ using experimentally measured ANC data. The results show that in the liquid nitrogen temperature range, the ATC of CeCrGe₃ can reach 15 times its ANC, indicating that this material possesses excellent solid-state thermoelectric cooling potential in that temperature regime. Furthermore, by optimizing the applied current density, the cold-end heat flow can be maximized, further enhancing cooling performance. An important conclusion of this work is that ATE can be directly verified using existing ANE experimental data, without the need for additional measurement equipment or experimental conditions.\n10. Fermi energy Weyl nodes in $\\mathbf{AM}$Te$_4$ ($\\mathbf{A}$=Ta, Nb, $\\mathbf{M}$=Ir, Rh) Relevance Score: 3.5697 Authors: Shivam Parasar, Jeroen van den Brink, Rajyavardhan Ray Affiliations: Birla Institute of Technology Mesra, Leibniz Institute for Solid-State and Materials Research (IFW) Dresden, Technische Universität Dresden Link: http://arxiv.org/abs/2605.05879v1 Summary: This work systematically investigates the distribution of Weyl points near the Fermi level in the Weyl semimetal family AMTe₄ (A = Ta, Nb; M = Ir, Rh) and its influence on quantum oscillations and magnetoresistance phenomena. Using a generalized search method, the authors comprehensively scan the band crossings of all subbands near the Fermi level and find that the distribution of Weyl points in these compounds is markedly different from previous studies that focused only on crossings between the highest valence band and the lowest conduction band. The results show that most compounds possess stable Weyl points within a few meV of the Fermi level, and most systems simultaneously host multiple types of Weyl points. For instance, NbRhTe₄ concurrently features type-I, type-II, and type-III Weyl points. The study also compares the effects of exchange-correlation functionals (LDA vs. GGA), lattice structures (experimental vs. optimized), and Wannier model quality on the electronic structure and the positions and energies of Weyl points. Based on a more accurate Wannier model, the de Haas–van Alphen oscillations of TaIrTe₄ are recalculated, significantly improving both qualitative and quantitative agreement between theory and experiment. This resolves previously unassignable quantum oscillation frequencies and magnetoresistance behaviors, such as non-saturating magnetoresistance, the quantum limit, and anomalous phase intercepts. This work not only maps the complex topological electronic structure of this family and elucidates the origin of magnetoresistance differences among different compounds, but also provides a theoretical framework for the precise manipulation of Weyl points, thus bridging the gap between theory and experiment.\n11. Enhancement of $J$$_c$ by Proton Irradiation in HgBa$_2$Ca$_2$Cu$_3$O$_8$$_+$$_δ$ Single Crystals Relevance Score: 3.5092 Authors: Wenjie Li, Ran Guo, Xin Zhou, Qiang Hou, Mengqin Liu, Longfei Sun, Yuhang Zu, Wenshan Hong, Yuan Li, Sheng Li, Yue Sun, Zhixiang Shi, Tsuyoshi Tamegai Link: http://arxiv.org/abs/2605.05800v1 Summary: This study introduces pinning centers into HgBa₂Ca₂Cu₃O₈₊δ single crystals via 3 MeV proton irradiation to enhance their critical current density (J_c). After irradiation, J_c is significantly improved, reaching a maximum at a dose of 1×10¹⁶/cm²: the self-field J_c at 2 K increases from 5.5 MA/cm² in the pristine crystal to 26 MA/cm²; at 77 K, the self-field J_c of all irradiated crystals exceeds 0.1 MA/cm², reaching practical levels. After irradiation, J_c exhibits a power-law dependence on the magnetic field, with the power exponent α close to 1, indicating strong pinning characteristics. The normalized magnetic relaxation rate varies monotonically with the magnetic field, attributed to the low irreversibility field caused by the high anisotropy of Hg1223. By comparing the pinning force density before and after irradiation, a clear transition in the pinning mechanism is observed—from elastic-plastic and creep crossover behavior in the pristine sample to strong pinning dominance after irradiation. At higher doses (≥1×10¹⁷/cm²), J_c decreases, accompanied by a gradual reduction in the superconducting transition temperature T_c, mainly due to the damaging effect of nanoscale defect clusters introduced by irradiation on superconductivity. This study confirms that proton irradiation is an effective means to enhance J_c in Hg1223 single crystals and reveals the associated changes in the pinning mechanism.\n12. Colossal Magnetoresistance and Phonon Driven Exchange Dynamics in Eu$_5$Sn$_2$As$_6$ Relevance Score: 3.4652 Authors: Luke Pritchard Cairns, Kohtaro Yamakawa, Shengzhi Zhang, Youzhe Chen, Bernard Field, Rainer Reczek, Ryan P. Day, Joel E. Moore, Marcelo Jaime, Sinead M. Griffin, Robert J. Birgeneau, James G. Analytis Affiliations: Physikalisch-Technische Bundesanstalt, University of Tokyo Link: http://arxiv.org/abs/2605.06649v1 Summary: This study reveals the lattice origin of the giant magnetoresistance effect in Eu₅Sn₂As₆ by measuring its thermal conductivity and magnetostriction. Experimental results show that both thermal conductivity and magnetostriction are strongly dependent on the magnetic field and vary synchronously with magnetization, saturating when the Eu²⁺ spins are fully polarized. The phonon-dominated thermal conductivity is significantly enhanced under a magnetic field, which is attributed to the field lifting the nearly degenerate spin configurations at zero field and suppressing the magnetostrictive strain caused by exchange frustration, thereby reducing strong phonon scattering. By comparison with spin-glass insulators, it is proposed that this suppression of phonon scattering is not a byproduct of electron localization, but rather a key mechanism driving electron delocalization and the giant magnetoresistance. Classical spin models further confirm that lattice vibrations (phonons) can dynamically alter the magnetic ground state, indicating that exchange striction is the dominant form of spin-phonon coupling. This conclusion highlights the close interplay among the lattice, spin, and charge subsystems, offering new insights into the giant magnetoresistance in novel Eu²⁺-based antiferromagnets.\n13. MLM: Multi-Layer Moire \u0026ndash; A Python Package for Generating Commensurate Supercells of Twisted Multilayer Two-Dimensional Materials Relevance Score: 3.4086 Authors: Anikeya Aditya, Sampad Mohanty Link: http://arxiv.org/abs/2605.05393v1 Summary: MLM is an open-source Python package designed to generate periodic supercells for twisted two-dimensional materials with an arbitrary number of layers. The method employs a solve-and-round strategy: for each candidate twist angle, the underlying lattice vectors are enumerated, and linear equations are solved to obtain the fractional coordinates of atoms in the top layer. If the fractional coordinates are close to integers within a tolerance, the points are accepted as coincident sites. This algorithm reduces the traditional O(N^4) brute-force enumeration to an O(N^2) linear algebra problem per angle. For systems with three or more layers, a sequential expansion approach is adopted: the supercell vectors of the first two layers are first determined, which are then used as a reference for matching with the next layer. MLM supports both homogenous and heterogenous bilayers, trilayers, and arbitrary multilayer stacks, and is applicable to various Bravais lattice types, including hexagonal and tetragonal. Its effectiveness has been validated on bilayer graphene, bilayer and trilayer MoS₂, bilayer SrTiO₃, and PbTiO₃/SrTiO₃ oxide heterostructures, directly generating input files for VASP and LAMMPS simulations. The atomic coordinates are generated using a fractional-coordinate folding algorithm, which can handle supercells containing millions of atoms and remains robust across all twist angles, including those below 1 degree. This tool fills the gap where existing bilayer tools struggle to scale to multiple layers, providing an efficient and reliable supercell construction scheme for atomistic simulations of multilayer moiré systems.\n14. Emergent spin quantum Hall edge states at the boundary of two-dimensional electron gas proximitized by an $s$-wave superconductor Relevance Score: 3.3423 Authors: M. V. Parfenov, V. S. Khrapai, I. S. Burmistrov Link: http://arxiv.org/abs/2605.05847v1 Summary: This paper investigates the topological properties of a hybrid structure composed of a two-dimensional electron gas and an s-wave superconductor (2DEG-S) in a quantized magnetic field. By analyzing the Bogoliubov-de Gennes Hamiltonian, the authors find that the system belongs to class C of the Altland-Zirnbauer classification, supporting the spin quantum Hall effect. Under a clean interface, the spin conductance exhibits even integer quantization in units of (e/4\\pi), while the charge conductance is non-quantized and sensitive to disorder. In disordered superconductors, using the nonlinear sigma model, it is demonstrated that the integer quantization of the spin conductance is topologically protected and robust against impurity scattering. The authors propose an experimental scheme: utilizing spin-split edge channels, the even integer quantization of the spin conductance can be detected through electrical measurements, thereby verifying the existence of class C edge states. This work indicates that the chiral Andreev edge states in the 2DEG-S hybrid structure are essentially spin quantum Hall edge modes, with topological protection manifested in the spin transport channel rather than the charge transport channel, providing a feasible route for the experimental observation of the spin quantum Hall effect.\n15. Strain-Dependent Ionic Transport in Li3YCl6 Solid Electrolytes Relevance Score: 3.3410 Authors: Wei-Fan Huang, Jin Dai, Jiahui Pan, Mingjian Wen Affiliations: University of Electronic Science and Technology of China, University of Houston Link: http://arxiv.org/abs/2605.05603v1 Summary: Based on the atomic cluster expansion (ACE) machine learning potential, this paper conducts large-scale molecular dynamics simulations of the Li₃YCl₆ halide superionic conductor, systematically investigating the effects of lattice strain on its ion transport behavior. The ACE potential, trained via an active learning strategy, accurately reproduces structural, mechanical, and transport properties from first-principles calculations and experiments. The study finds that Li⁺ diffusion in Li₃YCl₆ exhibits dual-regime Arrhenius behavior: a one-dimensional hopping mechanism at low temperatures and a three-dimensional cooperative diffusion at high temperatures, with a transition occurring at a critical temperature T_c. Lattice strain significantly modulates ion diffusivity—tensile strain enhances diffusion while compressive strain suppresses it—yet T_c remains unchanged, indicating that strain alters transport efficiency without affecting the underlying diffusion mechanism. The regulatory mechanism of strain differs across temperature regimes: at low temperatures, it primarily influences diffusion by changing the activation energy, while at high temperatures, it mainly acts through the pre-exponential factor. These results demonstrate that lattice strain can serve as a design lever for the ionic conductivity of Li₃YCl₆ solid electrolytes, providing theoretical guidance for optimizing electrolyte performance under realistic stress conditions in solid-state batteries.\n16. Quantum oscillations and nonsaturating magnetoresistivity in nodal-line semimetals Relevance Score: 3.2851 Authors: Rui Min, Yi-Xiang Wang Link: http://arxiv.org/abs/2605.06044v1 Summary: This study presents a theoretical analysis of the magnetotransport properties of the nodal line semimetal EuGa₄, with a focus on quantum oscillations and unsaturated magnetoresistance. A torus model is employed to describe the nodal line semimetal state. Within the framework of Landau quantization, the oscillatory behavior of the chemical potential as a function of magnetic field is analyzed by solving the eigenvalues and eigenstates of the Hamiltonian containing the magnetic field, under the condition of fixed carrier density. The longitudinal and Hall magnetoconductivities are calculated using the Kubo-Bastin formula, and the magnetoresistance is subsequently obtained. The findings reveal: (i) In the low-energy regime, two distinct frequencies appear in the oscillations of the chemical potential and magnetoconductivity with respect to the inverse magnetic field, corresponding to the outer and inner orbits of the torus Fermi surface—a characteristic that serves as an important experimental signature of nodal line semimetals; in the high-energy regime, only a single oscillation frequency is observed. (ii) Unsaturated magnetoresistance occurs only in the low-energy regime; however, over a wide range of Dirac mass and carrier density, the magnetoresistance ratio is significantly smaller than experimentally reported values, suggesting that the giant magnetoresistance observed in experiments may originate from mechanisms beyond band topology. Additionally, the influence of impurity scattering on transport is examined. This work provides deep insights into the microscopic mechanisms underlying magnetotransport behavior in nodal line semimetals.\n17. Unraveling the Origin of Ferrimagnetic Signatures in (Fe,Mn,Ga)2O3 Bixbyites: The Role of Structurally-Undetectable Spinel Impurities Relevance Score: 3.2671 Authors: Evgeniya Moshkina, Yuriy Knyazev, Ekaterina Smorodina, Oleg Bayukov, Maxim Molokeev, Evgeniy Khramov, Andrey Kartashev, Ruslan Batulin, Mikhail Cherosov, Dmitriy Velikanov, Evgeniy Eremin, Mikhail Rautskii, Dieter Kokh, Mikhail Platunov, Leonard Bezmaternykh Affiliations: Siberian State University of Science and Technologies, Professor V.F. Voino-Yasenetsky Krasnoyarsk State Medical University, National Research Centre “Kurchatov Institute”, Kazan Federal University, Far Eastern State Transport University, Federal Research Center KSC SB RAS, Boreskov Institute of Catalysis of Siberian Branch of the Russian Academy of Sciences, Siberian Federal University, Federal Research Center \u0026ldquo;Krasnoyarsk Science Center of the Siberian Branch of the Russian Academy of Sciences\u0026rdquo; Link: http://arxiv.org/abs/2605.05885v1 Summary: This study systematically investigates the origin of room-temperature ferromagnetic signals in cubic Fe₂₋ₓMnₓO₃ (bixbyite), aiming to address the long-standing controversy over its magnetic properties. The research team synthesized three single-crystal samples of (Fe,Mn,Ga)₂O₃ solid solutions with different Fe/Mn/Ga ratios using the flux method, along with a Ga-free Fe₂₋ₓMnₓO₃ reference sample. The actual chemical composition and crystal structure of the samples were precisely characterized using energy-dispersive X-ray spectroscopy (EDX), powder X-ray diffraction (XRD), and X-ray absorption spectroscopy (XAS). The magnetic states of the samples were investigated using a magnetometer and Mössbauer spectroscopy, and low-temperature magnetic anomalies were analyzed in conjunction with specific heat measurements. The results indicate that the low-temperature magnetic anomalies are more consistent with spin-glass freezing behavior rather than conventional long-range antiferromagnetic ordering. Although the magnetic behavior varies with composition and synthesis cooling rate, this does not account for the markedly distinct magnetic characteristics reported in the literature. Further magnetization and electron spin resonance (ESR) measurements revealed that the room-temperature ferromagnetism observed in one sample is extrinsic, primarily attributed to trace amounts of spinel-type impurity phases (such as Fe₃O₄ or MnFe₂O₄), which are undetectable by conventional XRD. Therefore, this work proposes that the fundamental cause of the discrepancies in reported magnetic properties of bixbyite-type oxides lies in the chemical purity of the samples, which is largely dependent on the synthesis process.\n18. Twisted Kagome Bilayers: Higher-Order Magic Angles, Topological Flat Bands, and Sublattice Interference Relevance Score: 3.2280 Authors: David T. S. Perkins, Joseph J. Betouras Affiliations: Loughborough University Link: http://arxiv.org/abs/2605.06551v1 Summary: This paper generalizes the renowned Bistritzer-MacDonald (BM) method and develops a low-energy continuum model applicable to heterojunction interfaces. Using twisted bilayer Kagome metal (TBK) as an example, the moiré physics near 1/3 filling (the energy level of the monolayer Dirac cone) is investigated. By projecting the active bands and applying a truncation approximation for interlayer tunneling, a low-energy continuum Hamiltonian for TBK is constructed. It is found that at specific twist angles, higher-order magic angles emerge, accompanied by significant local flattening of the Dirac cone and the appearance of higher-order van Hove singularities. Furthermore, nontrivial topological properties, such as non-Abelian valley Chern numbers in the bands, can be induced solely by twisting. Meanwhile, it is noted that while sublattice interference effects are important in monolayer Kagome, their impact in TBK is not significant. These results reveal the potential of band engineering to manipulate strongly correlated and topological physics in twisted layered Kagome systems.\n19. Winding feature and thermal evolution of the Dirac magnons in CrI$_3$ Relevance Score: 3.1207 Authors: Weiliang Yao, Matthew B. Stone, Colin L. Sarkis, Yi Li, Ruixian Liu, Xingye Lu, Pengcheng Dai Link: http://arxiv.org/abs/2605.06291v1 Summary: This study systematically measured the momentum and temperature dependence of magnon excitation spectra in the honeycomb ferromagnet CrI₃ using neutron inelastic scattering with improved sample quality. The experiments directly observed the winding feature of magnon scattering intensity near the K point of the hexagonal Brillouin zone—a phase reversal of the intensity distribution around the K point as the energy varies across the Dirac gap. This behavior serves as a direct experimental fingerprint of the topological structure of Dirac magnon wavefunctions in momentum space, which was previously indistinguishable due to sample quality limitations. Additionally, by measuring the magnon dispersion at different temperatures, it was found that the magnon energy exhibits an approximately T² renormalization behavior with increasing temperature near the Curie temperature, with more pronounced renormalization in the low-energy branch. This is consistent with energy softening and lifetime reduction caused by magnon-magnon interactions. These results not only fill a critical gap in experimental information regarding the magnon spectrum of CrI₃ but also further confirm the topological nature of its spin excitations. The study demonstrates that high-quality single-crystal samples are a prerequisite for resolving the subtle momentum-space characteristics of topological magnons, and CrI₃, as a prototypical two-dimensional van der Waals magnet, provides an ideal platform for bridging topological band theory with neutron scattering observations.\n20. Electrically controlled Heat Assisted Magnetic Recording in Intercalated 2D Magnets Relevance Score: 3.1043 Authors: Josue Rodriguez, Ruishi Qi, Catherine Xu, Feng Wang, James G. Analytis, Hossein Taghinejad Link: http://arxiv.org/abs/2605.06645v1 Summary: This paper proposes an all-electrical heat-assisted magnetic recording scheme that utilizes Joule heating from current pulses as a substitute for conventional laser heating to achieve data writing in the intercalated two-dimensional magnet Ni₁/₄TaSe₂, with electrical readout enabled by the anomalous Hall effect. This approach overcomes the limitations of traditional heat-assisted magnetic recording, which relies on lasers and plasmonic transducers and is difficult to integrate into chips. Using low current density pulses (on the order of ~10⁶ A/cm²) to heat Ni₁/₄TaSe₂ devices, combined with magneto-optical Kerr imaging and transport measurements, we directly confirm that the current pulses transiently heat the material above the Curie temperature. Under these conditions, a writing field as low as ~2 mT (100 times smaller than the coercive field) is sufficient to efficiently reverse the magnetization direction. The material retains strong perpendicular magnetic anisotropy below the Curie temperature, ensuring thermal stability of the data; above the Curie temperature, the anisotropy temporarily vanishes, enabling low-field writing. The threshold current density exhibits a quadratic relationship with the apparent Curie temperature reduction caused by Joule heating and depends on the pulse width. This scheme achieves reversible, deterministic switching between two saturated magnetization states, requiring far lower current densities than spin-transfer torque-assisted switching approaches. The combination of all-electrical operation with two-dimensional layered intercalated magnets offers new insights for overcoming the magnetic recording trilemma and holds promise for advancing magnetic storage technologies with high density, low power consumption, and ease of integration.\n","permalink":"https://nickelates.uk/en/posts/2026-05-08-arxiv-daily/","summary":"\u003cblockquote\u003e\n\u003cp\u003e\u003cstrong\u003eDaily Overview\u003c/strong\u003e:\nNo relevant papers have been published in the field of nickel-based superconductivity today.\u003c/p\u003e\u003c/blockquote\u003e\n\u003ch2 id=\"1-pair-breaking-and-dimensionality-in-spin-orbit-coupled-superconductors\"\u003e1. Pair-Breaking and Dimensionality in Spin-Orbit Coupled Superconductors\u003c/h2\u003e\n\u003cul\u003e\n\u003cli\u003e\u003cstrong\u003eRelevance Score\u003c/strong\u003e: \u003ccode\u003e4.5787\u003c/code\u003e\u003c/li\u003e\n\u003cli\u003e\u003cstrong\u003eAuthors\u003c/strong\u003e: Reiley Dorrian, Mizuki Ohno, Elena Williams, Adrian Llanos, Joseph Falson\u003c/li\u003e\n\u003cli\u003e\u003cstrong\u003eLink\u003c/strong\u003e: \u003ca href=\"http://arxiv.org/abs/2605.06514v1\"\u003ehttp://arxiv.org/abs/2605.06514v1\u003c/a\u003e\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003e\u003cstrong\u003eSummary\u003c/strong\u003e: This paper employs the multi-mechanism Kharitonov-Feigel’man (KF) framework to analyze the thickness-dependent superconductivity in spin-orbit-coupled superconducting thin films of LaBi₂, and systematically compares it with the conventional Klemm-Luther-Beasley (KLB) model. A series of high-quality single-crystal films ranging from the “bulk” to the ultrathin limit (2.1 nm) were prepared by molecular beam epitaxy, and the temperature-dependent upper critical fields were measured under parallel magnetic fields. In contrast to the KLB model, which only considers paramagnetic pair-breaking, the KF framework simultaneously incorporates three mechanisms: orbital pair-breaking, paramagnetic effects, and magnetic scattering (spin-exchange scattering). An anomalous enhancement of the critical field was observed in the ultrathin limit (2.1 nm), attributed to the suppression of magnetic fluctuations by the magnetic field, which effectively reduces the spin-exchange scattering rate. Through fitting with the KF model, the contributions of each scattering channel were successfully isolated: the magnetic scattering time is on the order of 10⁻¹²–10⁻¹¹ seconds, while the KLB model, due to its neglect of orbital pair-breaking, severely overestimates the spin-orbit scattering time (by up to four orders of magnitude) at finite thickness and is meaningful only in the zero-thickness limit. The study also reveals differences among three distinct definitions of the zero-field critical temperature (experimental value, KLB extrapolated value, and KF value without magnetic impurities), and emphasizes that the determination of the Pauli limit should be extrapolated to the strictly two-dimensional limit. The results indicate that the KLB model, by ignoring magnetic disorder and orbital effects, introduces systematic biases in the interpretation of fundamental superconducting parameters (such as critical temperature and Pauli limit), whereas the KF framework provides a more accurate deconstruction of pair-breaking mechanisms in two-dimensional superconductors, offering new insights into the relationship between scattering times and superconductivity.\u003c/p\u003e","title":"arXiv Daily: Nickelate superconductors 2026-05-08"},{"content":" Daily Overview: Today\u0026rsquo;s research highlights in the field of nickelate superconductors focus on the regulation of oxygen content in the La₃Ni₂O₇₊δ system. A collaborative team from the Chinese Academy of Sciences, Hainan University, Sun Yat-sen University, and other institutions successfully isolated pure bilayer phases, hybrid 1212 phases, and triple-layer intergrowth phases with different structures by precisely controlling the oxygen content. They found significant differences in superconducting transition temperatures—the pure bilayer phase reaches approximately 83.5 K, while the triple-layer intergrowth phase only exhibits 4–6 K. The study also established a phase diagram showing the evolution of Tc and upper critical field Hc₂ with oxygen content, revealing the decisive influence of oxygen content on the intergrowth structure of Ruddlesden-Popper phases and superconducting properties. This work provides key experimental evidence for understanding the high-temperature superconducting mechanism and synthesis control of La₃Ni₂O₇₊δ.\n1. Regulating oxygen content and superconductivity in La$_3$Ni$_2$O$_{7+δ}$ Relevance Score: 5.8274 Authors: Peiyue Ma, Jingyuan Li, Xing Huang, Yixing Zhao, Yifeng Han, Mengwu Huo, Deyuan Hu, Chaoxin Huang, Hengyuan Zhang, Sihao Deng, Lunhua He, Juan Rodriguez-Carvajal, Abhisek Bandyopadhyay, Alessandro Puri, Devashibhai Adroja, Xiang Chen, Tao Xie, Zhen Chen, Hualei Sun, Meng Wang Affiliations: Spallation Neutron Source Science Center, Chinese Academy of Sciences, Universita di Bologna, STFC Rutherford Appleton Laboratory, Institut Laue-Langevin, University of Johannesburg, Hainan University, University of Chinese Academy of Sciences, Lalit Narayan Mithila University, Consiglio Nazionale delle Ricerche, Sun Yat-Sen University Link: http://arxiv.org/abs/2605.04562v1 Summary: This study systematically investigates the effects of oxygen content on the microstructure and superconductivity of La$_3$Ni$_2$O$_{7+\\delta}$ polycrystalline samples synthesized with precisely controlled oxygen stoichiometry. Using X-ray absorption fine structure spectroscopy, neutron powder diffraction, synchrotron radiation X-ray diffraction, and scanning transmission electron microscopy, we reveal how oxygen content regulates the tilting of NiO$_6$ octahedra and the intergrowth structures of Ruddlesden–Popper phases. By precisely controlling the oxygen content, we obtain a pure bilayer phase, a mixed phase of bilayer and hybrid single-layer–bilayer, and a bilayer phase containing trilayer intergrowths. High-pressure electrical transport measurements show that these distinct phases exhibit markedly different superconducting transition temperatures: approximately 83.5 K for the pure bilayer phase, approximately 51 K for the hybrid 1212 phase, and approximately 4–6 K for the trilayer intergrowth phase. Further studies indicate that oxygen content not only determines phase purity (i.e., the presence of intergrowth phases) but also directly influences the upper critical field of the bilayer superconductor, with the pure bilayer phase exhibiting a higher $H_{c2}$. By establishing a phase diagram of $T_c$ and $H_{c2}$ as functions of oxygen content for La$_3$Ni$_2$O$_{7+\\delta}$, this work advances the synthetic control of Ruddlesden–Popper nickelates and provides new insights into the mechanism of their high-temperature superconductivity.\n2. Superconductivity in moiré transition metal dichalcogenide bilayers: comparison of two distinct theoretical approaches Relevance Score: 4.1425 Authors: Waseem Akbar, Michał Zegrodnik Link: http://arxiv.org/abs/2605.04693v1 Summary: This paper investigates the superconducting state in twisted bilayer WSe₂ using two complementary theoretical approaches. The first method is based on the negative-U Hubbard model combined with the Hartree-Fock approximation, yielding an isotropic s-wave superconducting gap that represents a relatively conventional pairing picture, in which strong electron repulsion does not directly affect the pairing state. The second method is based on the t-J-U model employing the Gutzwiller approximation, which accounts for strong correlation effects via significant renormalization induced by Coulomb repulsion, allows unconventional gap symmetries, and ultimately gives rise to mixed singlet and triplet pairing channels with topologically nontrivial Chern numbers. By comparing the key characteristics of the superconducting states obtained from these two frameworks: the negative-U Hubbard model predicts that the superconducting state is stabilized along the Van Hove singularity lines in the phase diagram, and can even be achieved away from half-filling by tuning the displacement field. This contradicts experimental observations, where the superconducting state only appears near half-filling. In the t-J-U model, the superconducting state is stabilized near half-filling at moderate interaction strengths, but strong correlations suppress superconductivity at half-filling due to the renormalization of the gap parameters. Upon further inclusion of the nearest-neighbor Coulomb repulsion, the superconducting state survives only in the region where Van Hove singularities intersect with half-filling, where both effects (renormalization and high density of states) simultaneously favor pairing. The resulting phase diagram is qualitatively consistent with experimental findings. This study indicates that the negative-U Hubbard model fails to reproduce the experimental features, whereas the t-J-U model, by incorporating strong correlations and Coulomb repulsion, provides a better description of the nearly half-filled superconductivity in twisted WSe₂.\n3. Response tensor for the superconducting (Josephson) diode effect Relevance Score: 3.8236 Authors: Qiong Qin, Jie Wu, Congjun Wu Link: http://arxiv.org/abs/2605.04928v1 Summary: We propose a response tensor to characterize the nonreciprocal critical current response in the superconducting (Josephson) diode effect. This tensor describes the coupling between the dipolar component of the angular distribution of the critical current and the applied magnetic field, analogous to the Hall response in the normal state. In quasi-two-dimensional systems with Rashba spin-orbit coupling and point group symmetry C₃ᵥ, C₄ᵥ, or C₆ᵥ, this tensor takes a completely antisymmetric form. When nematicity is present, symmetric contributions emerge, serving as an indicator of nematic order in the superconducting state. Conversely, for systems with Dresselhaus spin-orbit coupling and D₂ᵈ symmetry, the tensor becomes diagonal and traceless, with nematicity introducing a trace component. Our analysis not only explains the superconducting diode effect under an external magnetic field or intrinsic effective field but also predicts the symmetry conditions for realizing the diode effect when the magnetic field is parallel to the current. Furthermore, this tensor provides a powerful tool for probing nematicity and potential nematic phase transitions deep within the superconducting phase, and may encode additional information about the underlying electronic structure and symmetry-breaking orders, warranting further experimental investigation. Through mean-field theory and Ginzburg-Landau analysis, we validate these symmetry predictions in both Rashba and Dresselhaus spin-orbit coupling models, and demonstrate how nematicity modifies the tensor structure, thereby affecting the diode efficiency.\n4. Plastic deformation of B19\u0026rsquo; martensite where \u0026ndash; where it matters in NiTi technology Relevance Score: 3.7424 Authors: Petr Šittner, Hanuš. Seiner, Petr Sedlák, Orsolya. Molnárová, Lukáš Kadeřávek, Ondřej Tyc, Elizaveta Iaparova, Luděk Heller Affiliations: Institute of Physics of the CAS, Institute of Thermomechanics of the CAS Link: http://arxiv.org/abs/2605.04669v1 Summary: This paper systematically elucidates a unique plastic deformation mechanism of B19\u0026rsquo; martensite in NiTi alloys—kwinking (kink-twin cooperative deformation)—and explores its critical role in NiTi technology. The kwinking mechanism, through the synergistic action of 100 dislocation slip-induced kinking and (100) deformation twinning, enables martensite to achieve up to 80% plastic strain under extremely high stresses (\u0026gt;1 GPa), with a cold-work reduction ratio exceeding 90% without crack formation. Based on theoretical analysis, transmission electron microscopy observations, and texture evolution experiments, the study demonstrates that kwinking can reasonably explain a variety of anomalous phenomena reported over the past 50 years, including: excellent plastic workability in the martensitic state; tensile deformation leading to near-amorphous refinement of austenite microstructure; the formation of high-density {114} deformation bands in austenite; necking-induced fracture of strengthened NiTi wires upon tensile yielding; local plastic deformation (~40% local strain) driven by Lüders band propagation; an anomalously long upper stress plateau (\u0026gt;8% strain) in superelastic tension; large plastic strains (\u0026gt;20%) induced by a single cooling/heating cycle under constant stress; and shape setting of annealed NiTi via heating under external constraints. The paper also discusses how kwinking deformation can be incorporated into constitutive modeling and highlights the significance of this mechanism for understanding functional fatigue, microstructure manipulation, and further development of high-performance NiTi technologies.\n5. Imaging GHz surface acoustic wave modes in electrostricted LaAlO$_3$/SrTiO$_3$ heterostructures Relevance Score: 3.5697 Authors: Ranjani Ramachandran, Sayanwita Biswas, Prithwijit Mandal, Kyoungjun Lee, Madeleine Msall, Chang-Beom Eom, Patrick Irvin, Jeremy Levy, Mingyun Yuan Affiliations: Bowdoin College, University of Pittsburgh, Paul-Drude-Institut fur Festkörperelektronik, Leibniz-Institut im Forschungsverbund Berlin e.V., Pittsburgh Quantum Institute, University of Wisconsin-Madison Link: http://arxiv.org/abs/2605.04402v1 Summary: This study achieves GHz surface acoustic wave (SAW) excitation and imaging at room temperature in LaAlO₃/SrTiO₃ (LAO/STO) heterostructures via the electrostriction effect. Due to the absence of intrinsic piezoelectricity in STO at room temperature, conventional methods struggle to generate SAWs. In this work, by applying an external DC bias to induce electrostriction, SAW modes with frequencies up to 2.2 GHz are successfully observed, along with an extremely low propagation loss of approximately 10⁻³ dB per wavelength. To directly visualize these acoustic wave modes, the team employed atomic acoustic force microscopy (AAFM), achieving sub-micrometer-resolution imaging of SAW waveforms and thereby providing deep insights into the electrostriction-driven SAW generation mechanism. Experiments reveal two SAW modes with a frequency difference of about 10 MHz: a slow mode (approximately 2.156 GHz) and a fast mode (approximately 2.165 GHz), with the fast mode exhibiting stronger resonant peaks in both transmission and reflection coefficients. By varying the DC bias on the input/output interdigital transducers (IDTs), the coupling strength of the SAWs can be effectively tuned. AAFM imaging further confirms that both modes are surface waves, and the fast mode is identified as a shear-horizontal (SH) type mode capable of coupling with in-plane degrees of freedom. This study demonstrates that STO, as a commercially available substrate, can stably excite and propagate SAWs, providing a foundational platform for future integration of SAWs with various materials—such as two-dimensional electron gases, graphene, and transition metal dichalcogenides—for applications in quantum electronic transport, acoustoelectric effects, and hybrid quantum devices.\n6. Microscopic evidence for imaginary charge density wave in a kagome metal Relevance Score: 3.5065 Authors: S. Suetsugu, F. Hori, M. Shibata, S. Kitagawa, K. Ishida, T. Asaba, S. Nakazawa, Q. Li, H. -H. Wen, T. Shibauchi, H. Kontani, Y. Matsuda Link: http://arxiv.org/abs/2605.05101v1 Summary: This paper presents microscopic evidence for a pure imaginary charge density wave (iCDW) in the Kagome non-magnetic metal CsV₃Sb₅, obtained through nuclear quadrupole resonance (NQR) and nuclear magnetic resonance (NMR) spectroscopy. In experiments, NQR measurements on the perpendicular ¹²¹Sb site revealed anomalous line broadening above the nematic transition temperature of approximately 120 K, which is significantly higher than the transition temperature of the real charge density wave (rCDW). Under an applied external magnetic field, the spectral line exhibits an antisymmetric lineshape: the deviation of the peak frequencies from the centroid for different nuclear spin transitions shows opposite trends. By separating the electric quadrupole effect from the magnetic effect, it is confirmed that the broadening arises solely from the magnetic effect, rather than the electric quadrupole effect induced by CDW fluctuations. Quantitative fitting indicates that this antisymmetric lineshape is consistent with a local internal magnetic field of about 1 mT generated by a triple-q chiral loop current model, where the Sb2 site experiences an asymmetric hyperfine field distribution in a 1:3 ratio. Zero-field extrapolation yields a finite internal magnetic field value (approximately 0.3 Oe), demonstrating spontaneous time-reversal symmetry breaking at zero field. This study provides the first observation of a pure iCDW phase in bulk materials, whose essence is the chiral loop current order, fundamentally distinct from conventional real CDW. This discovery establishes a new ordered state in quantum materials, offering significant insights into the exotic electronic states in Kagome metals and the pseudogap phase of high-temperature superconductors.\n7. Nonlocal transport phenomena in coupled quasiperiodic Kitaev chains Relevance Score: 3.3654 Authors: Koki Mizuno Affiliations: Nagoya University Link: http://arxiv.org/abs/2605.04710v1 Summary: We investigate the topological phases in a coupled one-dimensional p-wave superconducting Fibonacci quasicrystal described by the quasiperiodic Kitaev chain model. Using the Keldysh Green\u0026rsquo;s function and recursive Green\u0026rsquo;s function methods, we systematically elucidate the topological phases of the coupled system and demonstrate the dependence of the differential conductance on the wiring connection pattern. It is found that topological phases emerge in the coupled system, characterized by the presence of Majorana edge modes and the leakage behavior of Majorana wave functions. Importantly, we identify novel topological phase transitions induced by quasiperiodicity. Furthermore, in both periodic and quasiperiodic coupled systems, there exist topological phases that cannot be fully characterized solely by topological invariants; these phases exhibit distinctive edge Majorana fermion properties, particularly asymmetric wave function leakage (e.g., cross-chain delocalization at the right edge, while a single Majorana mode at the left edge is confined to one chain). Finally, we establish an equivalence between the quasiperiodic Kitaev chain and a quasiperiodic quantum wire under strong spin-orbit coupling and a perpendicular Zeeman field with s-wave superconducting proximity effect, indicating that these theoretical predictions are experimentally realizable. Numerical results show that, within the parameter range considered, quasiperiodicity does not significantly alter the zero-bias conductance peaks associated with localized Majorana modes; however, when the coherence length is sufficiently long, quasiperiodicity indeed induces new topological phase transitions.\n8. Giant orbital-magnon conversion driven perpendicular magnetization switching Relevance Score: 3.3609 Authors: Fanyu Meng, Ying Feng, Mingyang Sun, Baiyan Kang, Donglin Song, Tuo Zhang, Jia Zhang, Wenping Zhou, Jijun Zhao, Yi Wang Affiliations: Huazhong University of Science and Technology, South China Normal University, Dalian University of Technology, Inner Mongolia University Link: http://arxiv.org/abs/2605.04486v1 Summary: This paper reports the experimental realization of orbital-to-magnon (L-M) conversion in a bilayer structure consisting of metallic Ti and antiferromagnetic insulator NiO, which exhibits an efficiency over one order of magnitude higher than conventional orbital systems lacking the L-M process at room temperature. The study utilizes Ti to generate an orbital current, which is injected into the NiO layer to excite a strong magnon current via L-M conversion, subsequently driving the perpendicular magnetization switching of the CoFeB ferromagnetic layer through magnon torque. Through spin-torque ferromagnetic resonance (ST-FMR) and harmonic Hall voltage measurements, the effects of NiO thickness and temperature on the damping-like torque efficiency (θ_DL) are systematically characterized, confirming the existence of magnon torque. Quantitative analysis yields an L-M conversion coefficient in NiO of approximately 0.06 (considering interfacial transmittance), an orbital diffusion length of about 3.2 nm, and a magnon diffusion length of about 25.4 nm. Finally, nearly 100% perpendicular magnetization switching of CoFeB is achieved at room temperature using pulsed currents, with the switching polarity controllable by the direction of the external magnetic field. This work experimentally establishes the first direct connection between orbitronics and magnonics, providing a platform for novel nanodevices based on orbital-driven magnon phenomena.\n9. Search for magnetoacoustic quantum oscillations in the insulating phase of YbB$_{12}$ Relevance Score: 3.3583 Authors: Ryosuke Kurihara, Atsuhiko Miyata, Koji Araki, Shusaku Imajo, Ruo Hibino, Atsushi Miyake, Sergei Zherlitsyn, Joachim Wosnitza, Hiroshi Yaguchi, Fumitoshi Iga, Masashi Tokunaga, Yasuhiro H. Matsuda Link: http://arxiv.org/abs/2605.04350v1 Summary: This study employed a bulk-sensitive ultrasonic experimental technique to systematically search for magnetoacoustic quantum oscillations in the insulating phase of the Kondo insulator YbB₁₂, under pulsed magnetic fields up to 65 Tesla and temperatures down to 485 millikelvin. The YbB₁₂ single-crystal samples used in the experiments had previously been confirmed to exhibit magnetoresistance oscillations in the insulating state. We first verified the sample quality through measurements of magnetoresistance and the magnetocaloric effect, successfully reproducing oscillation signals with a frequency of approximately 700 Tesla in the insulating phase, as well as anomalies at approximately 20 and 30 Tesla. However, measurements of the ultrasonic elastic constants (longitudinal and transverse modes) revealed no clear magnetoacoustic quantum oscillations in the insulating phase. Clear oscillation signals, with a frequency of approximately 620(50) Tesla, were observed only in the field-induced metallic phase (above the insulator-metal transition field of approximately 45 Tesla), consistent with previous reports. In the insulating phase, the ultrasonic data showed only a weak dip at approximately 10 Tesla, a kink anomaly at approximately 30 Tesla, and a pronounced dip structure at approximately 39 Tesla in the longitudinal elastic constant. The physical origins of these anomalies remain unclear and may be related to Lifshitz transitions or unknown phase transitions. By ruling out experimental factors such as the thermal effects of pulsed magnetic fields, we suggest that the absence of magnetoacoustic quantum oscillations in the insulating phase may arise from a different coupling mechanism between quasiparticles and phonons. For example, if the oscillations originate from electrically neutral fermions, they may not directly couple to lattice strain and thus cannot be detected via ultrasound. This study provides new constraints on the anomalous behavior of quantum oscillations in the insulating phase of YbB₁₂, supporting the hypothesis of the existence of unconventional quasiparticles (such as neutral fermions) in this system.\n10. Dielectric, magnetic, and magnetodielectric behaviors of BaFe12O19 hexaferrite modulated by Mn and Ti substitutions Relevance Score: 3.3560 Authors: Xiao-Fan Zhang, Yang Yang, Ze-Qing Guo, Li Lv, Can Gao, Jian-Ping Zhou, Xiao-ming Chen Affiliations: Xi’an Mingde Institute of Technology, Shaanxi Normal University, Fuyang Normal University Link: http://arxiv.org/abs/2605.04620v1 Summary: In this study, Mn and Ti single-doped and co-doped BaFe12O19 hexagonal ferrites were prepared by the solid-state reaction method, and their dielectric, magnetic, and magnetodielectric behaviors were systematically investigated. Raman spectroscopy and formation energy calculations indicate that Mn ions preferentially occupy the 4f2 and 2b sites, while Ti ions mainly substitute Fe³⁺ ions at the 4f1 and 12k sites. Pure BaFe12O19 exhibits ferromagnetism, whereas Ti-doped samples show a non-collinear longitudinal conical spin order at low temperatures, and BaFe6Mn3Ti3O19 maintains this spin order up to room temperature. The substitution of Ti⁴⁺ plays a key role in stabilizing the non-collinear conical spin order by modulating superexchange interactions and reducing the uniaxial magnetocrystalline anisotropy along the c-axis. The magnetic response exhibits two distinct transition temperatures, attributed to the interruption of inequivalent superexchange interactions with different exchange integrals by Ti⁴⁺ ions. Pure BaFe12O19 shows quantum paraelectric behavior at low temperatures, which is disrupted by Mn-Ti doping due to the decoupling of electric dipoles in the trigonal bipyramidal sites. In the 10–50 K range, electron hopping and polaron effects dominate the dielectric response; at high temperatures, Maxwell-Wagner interfacial polarization and electron hopping together lead to dielectric dispersion. At 10 K, the negative magnetodielectric effects in pure BaFe12O19 and BaFe6Mn3Ti3O19 originate from spin-phonon coupling and magnetic-field-induced electric polarization from the non-collinear spin order, respectively. The Mn-Ti co-doped samples achieve a higher magnetodielectric response under low magnetic fields; at high temperatures, the magnetodielectric effect mainly arises from the modulation of electron hopping by the magnetic field and extrinsic interfacial polarization. This study reveals that the physical properties of M-type hexagonal ferrites can be tuned by substituting Fe³⁺ ions at different crystallographic sites.\n11. Thermodynamics of stacking faults and phase stability in cobalt alloys: A combined computational and experimental study Relevance Score: 3.3361 Authors: Zheng Zhong, Ziqi Cui, Yu Zhuo, Tianyu Yu, Jianfeng Cai, Kaibo Zou, Jiacheng Shen, Bowen Huang, Zhuoming Xie, Huiqiu Deng, Yang Yu, Hao Zhang, Wangyu Hu, Tengfei Yang, Jie Hou Link: http://arxiv.org/abs/2605.04420v1 Summary: By combining first-principles thermodynamic calculations with microstructural characterization, this study systematically investigates the effects of alloying elements on the stacking fault energy and phase stability of cobalt-based alloys. At 0 K, the influence of transition metal solutes on stacking fault energy is primarily governed by atomic mismatch volume; 4d and 5d elements exhibit a consistent linear trend, while certain 3d elements deviate due to significant magnetic contributions. By incorporating contributions from phonons, electronic excitations, longitudinal spin fluctuations, and magnetic free energy, the model accurately describes the fcc-hcp phase transition in pure cobalt and quantitatively reveals the regulatory effects of different solutes on phase stability: V, Ni, Fe, Mo, and W lower the transition temperature by stabilizing the fcc phase, whereas Cr and C exhibit the opposite effect, consistent with experimental phase diagrams. Microstructural characterization further confirms that W dissolved in the cobalt matrix effectively suppresses the formation of stacking faults by increasing the stacking fault energy at finite temperatures. This work elucidates the physical mechanisms by which alloying governs the stacking fault energy and phase stability in cobalt-based systems, providing theoretical guidance for the design of cobalt-based alloys and WC-Co cemented carbides.\n12. Melting upon cooling in a quantum magnet Relevance Score: 3.3221 Authors: K. Jaksetič, T. Arh, M. Pregelj, M. Gomilšek, M. Dragomir, P. Prelovšek, M. Ulaga, L. Šibav, M. Malovrh, K. Železnikar, Z. Jagličić, P. Manuel, F. Orlandi, D. Khalyavin, M. D. Le, N. Bujault, E. Lhotel, J. van Tol, U. Jena, B. Sana, P. Khuntia, A. Zorko Link: http://arxiv.org/abs/2605.04611v1 Summary: This study demonstrates the first realization of a Pomeranchuk-like inverse melting phenomenon, termed the \u0026ldquo;spin Pomeranchuk effect,\u0026rdquo; in the quantum magnet ErTa7O19. This material is a triangular lattice Ising-type antiferromagnet with strong anisotropy and frustrated interactions. Through neutron diffraction, specific heat, and magnetic susceptibility measurements, it was observed that as temperature decreases below approximately 0.5 K, the system first forms a solid phase with long-range three-sublattice magnetic order, akin to a spin supersolid, which possesses a large excess entropy. However, at even lower temperatures (below about 0.3 K), this long-range ordered state unexpectedly melts into a short-range correlated spin stripe state (liquid phase), characterized by magnetic correlations extending only a few unit cells. This transition from long-range order to short-range correlation resembles the classical Pomeranchuk effect but does not require additional degrees of freedom. Theoretical analysis, combining Monte Carlo and finite-temperature Lanczos calculations, indicates that this inverse melting originates from a strong competition between long-range dipolar interactions and quantum fluctuations. In the classical pure dipolar Ising model, the low-temperature ground state should be stripe-ordered, but quantum effects (such as transverse exchange interactions) suppress the stripe phase, thereby stabilizing the long-range ordered three-sublattice state at higher temperatures due to entropy gain. This \u0026ldquo;spin Pomeranchuk effect\u0026rdquo; provides a new avenue for understanding exotic magnetic phase transitions in frustrated magnets and is expected to be extendable to other quantum materials.\n13. Frustrated magnetic order in hybrid Kitaev spin-orbital models Relevance Score: 3.1462 Authors: Ivan Dutta, Aayush Vijayvargia, Anamitra Mukherjee, Onur Erten, Kush Saha Link: http://arxiv.org/abs/2605.05196v1 Summary: This paper investigates the coexistence of two independently exactly solvable Kitaev-type spin liquid Hamiltonians (defined on distinct lattice geometries) on a common coordination-4 lattice. The analysis focuses on mixed systems combining the Kitaev honeycomb model with the square lattice model, as well as the Yao-Lee model with the square lattice model. Through self-consistent mean-field analysis and perturbative calculations, it is found that in the strong Kitaev coupling regime, a weak square-lattice spin-orbit coupling lifts the spin degeneracy, inducing magnetic order (ferromagnetic, antiferromagnetic, or spiral order), while the orbital part retains the Kitaev flux structure and topological order—a phenomenon termed \u0026ldquo;magnetic fragmentation.\u0026rdquo; For the mixture of the Yao-Lee and square lattice models, the mean-field solution does not yield magnetic order; instead, the competition between three species of Majorana fermions and two species of Majorana fermions reconstructs the low-energy bands, resulting in Dirac point shifts and Lifshitz transitions. Notably, when the Yao-Lee and square lattice couplings are equal in magnitude and opposite in sign, the model becomes exactly solvable again and supports a single itinerant Majorana fermion. These results suggest that mixed spin-liquid platforms can host a variety of emergent phases beyond the traditional exactly solvable limits.\n14. Magnetic Brightening and Nanoscale Imaging of Spin-Polarized Helical Edge Modes Relevance Score: 3.1070 Authors: Samuel Haeuser, Richard H. J. Kim, Lin-Lin Wang, Thomas Koschny, Pedro M. Lozano, Genda Gu, Randall K. Chan, Joong-Mok Park, Martin Mootz, Liang Luo, Qiang Li, Jigang Wang Affiliations: U.S. Department of Energy, Iowa State University Link: http://arxiv.org/abs/2605.04883v1 Summary: This study employs low-temperature magneto-infrared scattering-type scanning near-field optical microscopy (cm-IR-sSNOM) to achieve, for the first time, nanoscale real-space imaging and magnetic field control of highly spin-polarized infrared helical edge states in the topological insulator ZrTe5 at 1.8 K and under magnetic fields up to 5 T. The results reveal a magnetic-field-induced enhancement of near-field conductivity at step edges, indicating the presence of spin-split edge modes in the quantum spin Hall system, with increased infrared polarizability and a slight narrowing of the near-field distribution. Furthermore, the edge electrodynamic response increases approximately linearly with the number of atomic layers, providing strong evidence that the magnetic-field-induced energy gap at approximately 100 meV does not compromise the topological robustness of the monolayer edge state. This contrasts sharply with the suppression of edge conduction by the magnetic-field-induced gap observed in DC and microwave transport. The study demonstrates that magnetically tunable, topologically protected high-frequency edge modes offer a new pathway for achieving ultralow-loss nanoscale interconnects and quantum logic architectures in next-generation microelectronics, spintronics, and quantum information science.\n15. Effective long-range attraction of moiré excitons under the influence of atomic reconstructions and anisotropic screening Relevance Score: 3.0524 Authors: Nils-Erik Schütte, Carl Emil Mørch Nielsen, Niclas Götting, Alexander Steinhoff, Gabriel Bester, Christopher Gies Affiliations: Carl von Ossietzky Universität Oldenburg, University of Hamburg Link: http://arxiv.org/abs/2605.04667v1 Summary: This paper presents a material-realistic modeling of moiré exciton interactions in MoS₂/WS₂ heterobilayers, with a particular focus on atomic reconstruction and anisotropic screening effects. By combining DFT calculations with force-field relaxation, a reconstructed moiré potential is obtained, and the band structure of exciton center-of-mass motion is solved using a continuum model. The results show that atomic reconstruction significantly modifies the shape of the moiré potential: for small twist angles (e.g., 1°), the potential wells become wider and deeper, leading to flatter exciton bands; for large twist angles (e.g., 3.9°), the reconstruction effect is weaker. The on-site interaction U is strongly affected by reconstruction—it increases at large twist angles and decreases at small twist angles. For long-range interactions (spanning the moiré period scale), anisotropic dielectric screening causes the exciton–exciton interaction to switch from repulsive to attractive, a transition that can be tuned by the dielectric environment. Finally, using the interaction potentials and hopping amplitudes as parameters, a Bose–Hubbard model on the moiré lattice is constructed, and the quantum phase behavior of excitons is predicted via mean-field approximation. This work reveals the decisive roles of atomic reconstruction and dielectric anisotropy in moiré exciton interactions, providing a theoretical foundation for understanding related many-body phenomena.\n16. Spin-wave bandgap engineering via mode hybridization in dipolar-coupled YIG film/CoFeB nanodisk magnonic crystals Relevance Score: 3.0499 Authors: Junyoung Hyun, Krzysztof Szulc, Mateusz Zelent, Nikolai Kuznetsov, Lukáš Flajšman, Maciej Krawczyk, Paweł Gruszecki, Sebastiaan van Dijken Link: http://arxiv.org/abs/2605.04774v1 Summary: This paper investigates spin-wave propagation in a hybrid two-dimensional magnonic crystal composed of a low-damping yttrium iron garnet (YIG) thin film coupled with a periodic array of CoFeB nanodisks. Using propagating spin-wave spectroscopy, super-Nyquist magneto-optical Kerr effect microscopy, and micromagnetic simulations, we observe the formation of prominent and tunable band gaps in this system, whose origin is not conventional Bragg scattering. These band gaps arise from the hybridization between the fundamental magnonic crystal mode and in-plane transverse standing-wave modes induced by the nanodisk array. The spectral positions and widths of the band gaps can be tuned by geometric parameters (such as nanodisk diameter and lattice period) as well as the magnetic state of the nanodisks (including vortex configurations), which determine the nature of the static and dynamic dipolar coupling. For larger lattice periods, additional band gaps emerge due to hybridization with quantization modes both transverse and longitudinal to the propagation direction, reflecting dispersion folding in two dimensions. The experimental results establish mode hybridization as a spin-wave band engineering mechanism that goes beyond the limitations of Bragg scattering, providing a pathway toward reconfigurable magnonic devices based on dipolar-coupled hybrid architectures.\n17. Magnetic influence on ion transport in concentrated solid solutions: An analytic investigation Relevance Score: 3.0498 Authors: Timothy Carlson, Sanjay Govindjee Link: http://arxiv.org/abs/2605.04370v1 Summary: This paper systematically investigates the influence of magnetic fields on ion transport in solid ionic conductors using analytical methods. Based on the Onsager-Stefan-Maxwell multicomponent concentrated solution theory and incorporating the full form of the Lorentz force, generalized multicomponent transport equations including magnetic field effects are derived. For isotropic materials, three specific models are established: single-ion conductors, single-ion conductors with secondary mobile species (e.g., systems with vacancies), and binary ionic conductors. In the single-ion conductor model, a standard conductivity expression incorporating the Hall effect is derived. For single-ion conductors with vacancies, the derived macroscopic conductivity is shown to be consistent in form with the standard single-carrier model, with the caveat that the effective carrier concentration is related to the vacancy concentration. For binary conductors, an analytical expression for the conductivity tensor, including partial Hall coefficients, is obtained. By analyzing combined parameter conditions, a physical criterion for significant magnetic field effects is revealed: when the partial resistivity of a certain species is extremely small, the magnetic field effect may become non-negligible. Finally, the binary conductor model is applied to the fluoride ion conductor Pb₀.₆₆Cd₀.₃₄F₂. Under the assumption of nearly degenerate multicomponent transport, the magnetoresistance calculated by the model agrees well with experimental data, explaining the strong magnetic field effects that cannot be predicted by classical Hall coefficient estimates. This study indicates that the influence of magnetic fields on transport in solid ionic conductors may originate from multicomponent interactions and carrier concentration constraints, rather than a simple Hall effect.\n18. Sculpting Spin-Wave Landscapes via Curvature of 2D Magnonic Crystals Relevance Score: 3.0260 Authors: Ondřej Wojewoda, Robert Kraft, Olha Bezsmertna, Oleksandr Pylypovskyi, Jose A. Fernandez Roldan, Caroline A. Ross, Rui Xu, Sergey A. Bunyaev, Ivan Soldatov, Rudolf Schäfer, Claas Abert, Gleb N. Kakazei, Michal Urbánek, Denys Makarov Affiliations: Helmholtz-Zentrum Dresden-Rossendorf, Kyiv Academic University, Leibniz Institute for Solid State and Materials Research, University of Vienna, Universidade do Porto, Massachusetts Institute of Technology, Brno University of Technology Link: http://arxiv.org/abs/2605.05156v1 Summary: This paper proposes a novel method for manipulating the band structure of spin waves using large-area curved nanotemplates. By depositing a 50 nm thick Permalloy film on a periodically arranged three-dimensional nanopillar array (with a period of 400 nm), a two-dimensional magnonic crystal is constructed. Micro-focused Brillouin light scattering measurements confirm that, under an external magnetic field exceeding 200 mT, the structure forms a complete in-plane bandgap and exhibits flat-band modes in the low-frequency region, corresponding to strong real-space localization of spin waves in the valley regions of the nanopillars. The bandgap can be dynamically opened and closed by varying the strength of the external magnetic field. Static magnetization characterization and micromagnetic simulations further reveal that the three-dimensional curvature induces shape anisotropy and modulates the effective internal field, resulting in multi-branch responses in the ferromagnetic resonance spectrum and fourfold symmetric in-plane anisotropy. The results demonstrate that continuous films based on three-dimensional templates provide a versatile platform for two-dimensional signal processing and magnonic computing, avoiding the drawback of conventional methods where the removal of material to fabricate two-dimensional magnonic crystals significantly shortens the spin wave propagation length.\n19. An extended ab initio theory of the V$_{\\text{B}}^-$ center in hBN: excited states, Jahn-Teller distortion, and pressure dependence Relevance Score: 3.0065 Authors: Zsolt Benedek, Ádám Ganyecz, Oscar Bulancea-Lindvall, Gergely Barcza, Viktor Ivády Affiliations: Eötvös Loránd University, Linköping University, HUN-REN Wigner Research Centre for Physics Link: http://arxiv.org/abs/2605.04283v1 Summary: This paper presents an ab initio theoretical study of the negatively charged boron vacancy (Vₐ⁻) center in hexagonal boron nitride (hBN) using wavefunction-based advanced electronic correlation methods (CASSCF-NEVPT2). The energetics, structural relaxation, and transition rates of the center are systematically modeled, with in-depth analysis of the excited-state fine structure, pseudo-Jahn-Teller effect, singlet-triplet quasi-degeneracy, photoluminescence parameters, intersystem crossing pathways, and the influence of stress on the fine structure and decay parameters. The results indicate that after optical excitation, the Vₐ⁻ center rapidly relaxes to the lower triplet states via internal conversion. The E\u0026rsquo; state undergoes a significant static Jahn-Teller distortion (stabilization energy of 308 meV), forming a ground-state configuration with C₂ᵥ symmetry, whereas the A₂\u0026rsquo; state exhibits weaker distortion. The calculated zero-phonon line energy is 1.56 eV, with a Huang-Rhys factor of 5.4 and a Debye-Waller factor of only 0.4%, indicating that the photoluminescence spectrum is dominated by a broad phonon sideband, rendering the zero-phonon line unresolved. Radiative transitions predominantly occur between the E\u0026rsquo; state and the ground state, with a calculated radiative lifetime on the order of microseconds. The study further reveals significant anharmonicity in the potential energy surface (a three-hat-shaped potential) induced by the pseudo-Jahn-Teller effect, and explores the transition between static and dynamic Jahn-Teller systems at different temperatures. These findings clarify the fundamental photophysical behavior of the Vₐ⁻ center and provide a theoretical basis for developing readout schemes for this center in hBN-based integrated two-dimensional quantum sensors.\n","permalink":"https://nickelates.uk/en/posts/2026-05-07-arxiv-daily/","summary":"\u003cblockquote\u003e\n\u003cp\u003e\u003cstrong\u003eDaily Overview\u003c/strong\u003e:\nToday\u0026rsquo;s research highlights in the field of nickelate superconductors focus on the regulation of oxygen content in the La₃Ni₂O₇₊δ system. A collaborative team from the Chinese Academy of Sciences, Hainan University, Sun Yat-sen University, and other institutions successfully isolated pure bilayer phases, hybrid 1212 phases, and triple-layer intergrowth phases with different structures by precisely controlling the oxygen content. They found significant differences in superconducting transition temperatures—the pure bilayer phase reaches approximately 83.5 K, while the triple-layer intergrowth phase only exhibits 4–6 K. The study also established a phase diagram showing the evolution of Tc and upper critical field Hc₂ with oxygen content, revealing the decisive influence of oxygen content on the intergrowth structure of Ruddlesden-Popper phases and superconducting properties. This work provides key experimental evidence for understanding the high-temperature superconducting mechanism and synthesis control of La₃Ni₂O₇₊δ.\u003c/p\u003e","title":"arXiv Daily: Nickelate superconductors 2026-05-07"},{"content":" Daily Overview: Today\u0026rsquo;s overview of the nickelate superconductor field focuses on magnetic studies of bilayer La₃Ni₂O₇ single crystals. Using neutron scattering techniques, this work, for the first time under ambient pressure, clarifies the spin excitation energy gap, in-plane anisotropic dispersion, and bilayer periodic modulation in this material, directly confirming the existence of interlayer antiferromagnetic coupling. A bilayer Heisenberg model based on stripe-type magnetic order successfully describes the experimental dispersion and reveals that its spin-wave bandwidth is only about 25% of that in cuprates, yet the total fluctuating magnetic moment at comparable energies is similar to that in cuprates, establishing a magnetic framework distinct from cuprates. These results provide key constraints on the magnetic order and spin dynamics for understanding the possible high-temperature superconductivity mechanism in bilayer nickelate systems.\n1. Nature of magnetism in bilayer nickelate La3Ni2O7 single crystals Relevance Score: 5.9525 Authors: Lixing Chen, Enkang Zhang, Yiqing Hao, Yinghao Zhu, Bingkun Cui, Douglas L. Abernathy, Travis J. Williams, Yoichi Ikeda, Hao Zhang, Feiyang Liu, Wenbin Wang, Qisi Wang, Jun Zhao Link: http://arxiv.org/abs/2605.03448v1 Summary: Here is the professional English translation of the provided Chinese summary: Using neutron scattering techniques, this study investigates the spin ordering and dynamic properties of bilayer nickelate La₃Ni₂O₇ single crystals under ambient pressure. Clear spin excitations were observed at Q = (0, 0.5, 2.5), characterized by a spin gap of approximately 5 meV and an in-plane anisotropic dispersion. Band softening at the zone boundary along the transverse direction indicates the presence of competing exchange interactions. The excitations exhibit a pronounced bilayer periodic modulation along the out-of-plane direction, providing direct evidence for interlayer antiferromagnetic coupling. A bilayer Heisenberg Hamiltonian model based on a stripe-type magnetic order, featuring strong interlayer exchange interactions and competing in-plane couplings, well describes the experimental dispersion. After normalizing the spectrum to absolute units, it is found that, although the spin-wave bandwidth is only about 25% of that in cuprates, the local dynamic magnetic susceptibility is significantly enhanced at comparable energies, and the total fluctuating magnetic moment is comparable to that in cuprates. These results highlight that intermediate-energy spin excitations arising from strong electronic correlations are a hallmark feature of this family of materials, establishing a magnetic framework distinct from cuprates and bearing direct implications for understanding the superconducting mechanism in this system.\n2. Pressure induced Electronic and Structural Transition in Ba$_2$NiTeO$_6$ Relevance Score: 4.6269 Authors: Bidisha Mukherjee, Supratik Mukherjee, Mrinmay Sahu, Bhagyashri Giri, A C Gracia Castro, G Vaitheeswaran, Konstantin Glazyrin, Goutam Dev Mukherjee Link: http://arxiv.org/abs/2605.03593v1 Summary: This study systematically investigates the evolution of the structural, vibrational, and electronic properties of double perovskite Ba₂NiTeO₆ under high pressure through a combination of experimental and theoretical approaches. Experimentally, synchrotron X-ray diffraction and micro-Raman spectroscopy were employed for characterization up to 45 GPa. Theoretically, density functional theory was used to simulate the changes in structural, electronic, and magnetic properties with pressure. The main findings are as follows: First, a structural phase transition occurs at approximately 21 GPa, from a trigonal R¯3m phase to a monoclinic C2/m phase, accompanied by a significant increase in bulk modulus (from 102 GPa to 167 GPa). Second, an anomaly is observed in the Raman spectra at around 1 GPa, where the slopes of some mode frequencies abruptly change or even soften. Combined with DFT calculations, this indicates a transition of the electronic structure from a direct band gap to an indirect band gap. Furthermore, at approximately 11 GPa, the full width at half maximum of Raman modes reaches a minimum, corresponding to a decrease in the distortion index of NiO₆ octahedra and a discontinuity in the c/a ratio, suggesting an increase in sample order. These results reveal the coupling mechanism among lattice, electronic, and magnetic interactions under pressure, providing key experimental and theoretical insights into the behavior of such complex oxides under extreme conditions.\n3. Point-contact enhanced superconductivity in trigonal PtBi2: quest for the origin of high-Tc Relevance Score: 4.2263 Authors: O. E. Kvitnitskaya, L. Harnagea, G. Shipunov, S. Aswartham, I. Kovalchuk, V. V. Fisun, D. V. Efremov, B. Büchner, Yu. G. Naidyuk Affiliations: IFW Dresden, NAS of Ukraine, Technische Universität Dresden, Kyiv Academic University, Indian Institute of Science Education and Research (IISER) Link: http://arxiv.org/abs/2511.00920v2 Summary: In this study, point contacts (PCs) were fabricated on the type-I Weyl semimetal trigonal phase PtBi₂, using normal metal (Ag, Cu, Pt) and ferromagnetic metal (Fe, Co, Ni) tips. Enhanced superconductivity was investigated by measuring differential resistance dV/dI(V) curves. Experiments revealed that the superconducting critical temperature Tc of most PCs is concentrated between 3 and 5 K, several times higher than the bulk superconducting Tc. Some PCs even exhibit a Tc as high as 8 K, with the critical magnetic field also enhanced to several Tesla. The increase in Tc may be associated with the pressure or strain generated during PC formation. Notably, PCs formed at the edges of thin sample flakes show higher Tc than those formed on flat surfaces. Furthermore, ferromagnetic tips also exhibit compatible enhanced superconductivity, suggesting that the mechanism underlying the enhancement may be of a complex nature. These results indicate that t-PtBi₂ is a promising candidate for achieving topological superconductivity at higher temperatures.\n4. Superconductivity in hole-doped germanium point contacts Relevance Score: 4.2255 Authors: N. V. Gamayunova, M. Kuzmiak, P. Szabo, P. Samuely, Yu. G. Naidyuk Affiliations: Slovak Academy of Sciences, National Academy of Sciences of Ukraine Link: http://arxiv.org/abs/2109.01364v1 Summary: Superconductivity was observed through measurements of the differential resistance (dV/dI(V)) spectra of heavily p-type doped germanium (Ge) in contact with platinum-iridium (PtIr) point contacts. The experiment employed a \u0026ldquo;tip-anvil\u0026rdquo; technique, where a sharp PtIr wire was pressed against a Ge crystal surface at low temperatures to form point contacts, and spectra were recorded over a temperature range of 1.5–10 K and a magnetic field range of 0–2 T. In some point contacts, a double-minimum structure resembling Andreev reflection was observed near zero bias. These features gradually diminished with increasing temperature or magnetic field, completely vanishing above approximately 6 K or 1 T, corresponding to a critical temperature Tc ≈ 5–6 K and a critical magnetic field Bc ≈ 1.3 T. The spectra were fitted using the single-gap Blonder-Tinkham-Klapwijk (BTK) model, yielding a superconducting gap Δ of approximately 2.4 meV. The temperature dependence of the gap closely followed the BCS theory prediction, but the ratio 2Δ/kBTc was as high as 10 ± 1, far exceeding that of conventional superconductors (BCS theoretical value ~3.5). The magnetic field significantly suppressed the Andreev reflection features, but the superconducting gap decreased slowly with increasing field, similar to the behavior observed in type-II superconductors such as nickel borocarbides and iron-based superconductors. Notably, no superconducting signal was observed in n-type Ge with the same doping concentration. The spectral intensity was low (only a few percent), indicating that the superconducting phase occupied a small volume within the point contact region. These results suggest the possible existence of an unconventional superconducting mechanism in heavily p-type doped Ge, with the high gap ratio and slow gap variation under magnetic field warranting further investigation.\n5. Quasiclassical theory of vortex states in locally non-centrosymmetric superconductors: application to CeRh$_{2}$As$_{2}$ Relevance Score: 4.1954 Authors: Akihiro Minamide, Youichi Yanase Link: http://arxiv.org/abs/2510.14452v2 Summary: This paper employs a quasiclassical theoretical approach to investigate vortex states in bilayer superconductors with local inversion symmetry breaking, and applies the results to the heavy-fermion superconductor CeRh₂As₂. In this material, two distinct superconducting phases exist under a c-axis magnetic field: a conventional even-parity spin-singlet superconducting state at low fields, and an odd-parity spin-singlet superconducting state at high fields, where the order parameter alternates sign between adjacent Ce layers (i.e., a pair density wave state). Based on a bilayer Rashba model, the authors derive the multiband quasiclassical Eilenberger equations and employ an approximate solution method to treat the vortex lattice state. Through self-consistent calculations, the phase diagram of the BCS state and the PDW state at low temperatures is obtained, and the local density of states (LDOS) in the vortex lattice state is computed. The results reveal that the pairing symmetry of different superconducting states is clearly reflected in the LDOS peak structure at the vortex core: the peak positions and shapes of the LDOS corresponding to the BCS state and the PDW state exhibit significant differences. Since LDOS can be directly observed via experiments such as scanning tunneling microscopy, this work provides a clear pathway for experimentally verifying the superconducting parity transition in CeRh₂As₂. Furthermore, the study also incorporates the orbital depairing effect, overcoming previous limitations that focused only on uniform states or isolated vortices, and offers a microscopic theoretical foundation for understanding the thermodynamic properties and electronic structure of the vortex lattice state in this material.\n6. Coupled phase transitions in crystalline solids with extreme chemical disorder Relevance Score: 4.1440 Authors: Subha Dey, Rukma Nevgi, Suresh Chandra Joshi, Sourav Chowdhury, Nandana Bhattacharya, Kashish Kapoor, Tinku Dan, Subhadip Chowdhury, Sabyasachi Karmakar, S. D. Kaushik, Shibabrata Nandi, Christoph Klewe, Manuel Valvidares, Moritz Hoesch, George E. Sterbinsky, Srimanta Middey Link: http://arxiv.org/abs/2605.03444v1 Summary: This study demonstrates that by carefully designing complex composition oxides (CCOs), coupled structural phase transitions can be realized in a lattice with extreme chemical disorder, challenging the conventional view that such transitions are rare in high-entropy systems. Using the spinel-type [Mn₀.₂Co₀.₂Ni₀.₂Cu₀.₂Zn₀.₂]Cr₂O₄ as a representative material, where the A-site contains five equimolar divalent transition metal ions, experiments reveal two successive symmetry-lowering structural phase transitions upon cooling: the first near 100 K, driven by orbital ordering of Jahn-Teller (J-T) active ions (Ni²⁺ and Cu²⁺), inducing a cubic-to-tetragonal transition; and the second near 40 K, driven by long-range magnetic ordering, further transforming to an orthorhombic phase. Systematic substitution of A-site cations confirms that these phase transitions occur only when both Ni and Cu (the two J-T active ions) are present. Using element-specific extended X-ray absorption fine structure (EXAFS) spectroscopy to probe local structure, it was found that the bond lengths around Ni and Cu exhibit opposing distortion trends with decreasing temperature (Ni–O and Ni–Cr bonds contract, while Cu–O and Cu–Cr bonds elongate), whereas the local environments of Mn, Co, and Zn remain largely unchanged. This \u0026ldquo;cooperation through competition\u0026rdquo; mechanism of local distortions enables the overall lattice to undergo a global structural transition while maintaining a high-symmetry framework. This finding expands the design principles for complex oxides and offers a new paradigm for tuning structural and functional properties through chemical disorder in high-entropy systems.\n7. Gossamer Superconductivity in Moiré WSe$_2$ Bilayer Relevance Score: 4.0877 Authors: Hui-Ke Jin, Guangyue Ji, Zhan Wang, Jie Wang, Fu-Chun Zhang Link: http://arxiv.org/abs/2605.03766v1 Summary: This paper proposes that the superconductivity observed in twisted bilayer WSe₂ under half-filling and zero displacement field possesses a \u0026ldquo;gauze\u0026rdquo; nature. By mapping the moiré continuum system onto an effective extended single-orbital Hubbard model on a triangular lattice and employing renormalized mean-field theory to study the strong-coupling phase diagram, the authors find that moderate Coulomb repulsion partially suppresses charge fluctuations while retaining a finite density of mobile double occupancies and holes. In this regime, the synergy between extended kinetic energy and antiferromagnetic superexchange stabilizes a chiral d+id superconducting phase. The theory naturally explains the evolution from a Mott insulator to a superconductor and then to a correlated metal as the twist angle varies. The model also indicates that this half-filled pairing state rapidly disappears upon doping, consistent with experimental observations. By analyzing the trajectory of effective model parameters with twist angle, the phase diagram qualitatively reproduces the superconducting transition behavior observed in experiments: at small twist angles, the extremely flat bands lead to a strongly correlated Mott insulator; as the twist angle increases, the system enters the gauze superconducting phase; with further increase in twist angle, correlations weaken and the system eventually becomes a metal. Furthermore, the gauze state already possesses intrinsic charge mobility at half-filling and is therefore highly sensitive to doping, explaining the extremely narrow superconducting dome observed in experiments. This work establishes, for the first time, a connection between superconductivity in twisted WSe₂ and the gauze superconductivity mechanism, offering new perspectives for understanding unconventional superconductivity in moiré materials.\n8. Anisotropic Josephson coupling of $d$ vectors in triplet superconductors arising from frustrated spin textures Relevance Score: 4.0119 Authors: Grayson R. Frazier, Junyi Zhang, Yi Li Link: http://arxiv.org/abs/2506.15661v3 Summary: This work demonstrates that coupling itinerant electrons to a non-collinear classical exchange field can induce anisotropic Josephson couplings between the d-vectors of triplet superconductors, analogous to the Dzyaloshinskii–Moriya and Γ-type interactions in magnetic systems. Using a perturbative approach, the authors analyze the s-d model on a geometrically frustrated lattice. The study finds that non-collinear local spin textures can generate spin-triplet pairing correlations and, due to the anisotropic Josephson coupling between d-vectors, favor a spatially varying superconducting order parameter, thereby imparting a \u0026ldquo;flexibility\u0026rdquo; to the pairing order that competes with the superfluid stiffness. In the case of non-unitary pairing, the spatial texture of the d-vector can give rise to anomalous vortices in the absence of an external magnetic field. Furthermore, the paper predicts a Josephson diode effect whose efficiency is proportional to the spin chirality of the underlying magnetic texture. These results establish a direct connection between frustrated magnetism and the spatial texture of triplet superconducting pairing, with important implications for materials such as Mn₃Ge and 4H_b-TaS₂, where superconductivity is realized via proximity effects or intrinsically.\n9. Nonuniform superconducting states from Majorana flat bands Relevance Score: 3.9379 Authors: Sushanth Varada, Aksel Kobiałka, Ankita Bhattacharya, Patric Holmvall, Annica M. Black-Schaffer Link: http://arxiv.org/abs/2605.03859v1 Summary: Zero-energy flat bands existing within the superconducting gap can induce competing ordered phases. We investigate such phases in topological superconductors based on a magnetic adatom platform that hosts a flat band of Majorana edge states. Through self-consistent calculations of the superconducting order parameter, we identify two inhomogeneous superconducting states: a pair density wave, characterized by edge-localized amplitude modulation, and a phase crystal, characterized by edge-localized phase modulation. Both phases lower the system’s free energy by opening a gap in the Majorana flat band, and their behavior is governed by a winding number primarily tuned by the chemical potential. At zero temperature, the uniform superconducting state with Majorana flat bands is always unstable, and the pair density wave dominates the phase diagram; when the amplitude modulation is insufficient to hybridize all Majorana states, the order parameter transforms into a phase crystal. A broad intermediate region exists where the strengths of amplitude and phase modulation are comparable. At finite temperatures, the pair density wave survives up to approximately 80% of the bulk superconducting transition temperature, whereas the phase crystal appears only at lower temperatures, and the intermediate region is strongly suppressed. Our findings establish the universality of inhomogeneous superconducting phases and their temperature-dependent behavior in topological superconductors.\n10. Spatially Inhomogeneous Triplet Pairing Order and Josephson Diode Effect Induced by Frustrated Spin Textures Relevance Score: 3.9111 Authors: Grayson R. Frazier, Yi Li Link: http://arxiv.org/abs/2510.25756v3 Summary: This paper investigates how frustrated spin structures induce anisotropic Josephson coupling in spin-triplet superconductors, thereby stabilizing spatially inhomogeneous spin-triplet pairing orders. Competing with the superfluid stiffness of the superconductor, such “flexibility” originates from couplings analogous to the Dzyaloshinskii-Moriya and Γ-type interactions in magnetism, yet arises not from spin-orbit coupling but from the coupling of itinerant electrons to frustrated local spin moments. Through a T-matrix expansion, it is demonstrated that such coupling leads to effective electron tunneling that depends on the spin configuration of the barrier. For a three-sublattice perturbed system, the analysis shows that the coupling between itinerant electrons and local exchange fields can generate effective tunneling that depends on the spin structure. Furthermore, when the frustrated spin structure possesses finite spin chirality or when antisymmetric Josephson coupling exists between noncollinear d-vectors, the system breaks inversion and time-reversal symmetries, thereby realizing the Josephson diode effect. This diode effect can originate either from spin chirality in the barrier or directly from antisymmetric Josephson coupling. This work provides a new route for engineering non-uniform superconducting textures through magnetic frustration rather than spin-orbit coupling and reveals the possibility of direct interplay between frustrated magnetism and unconventional superconductivity.\n11. Magnetic field-induced momentum-dependent symmetry breaking in a kagome superconductor Relevance Score: 3.8720 Authors: Jianwei Huang, Zheng Ren, Hengxin Tan, Jounghoon Hyun, Yichen Zhang, Thomas Hulse, Zhaoyu Liu, Jonathan M. DeStefano, Yaofeng Xie, Ziqin Yue, Junichiro Kono, Pengcheng Dai, Yu He, Aki Pulkkinen, Ján Minár, Jiun-Haw Chu, Ziqiang Wang, Binghai Yan, Rafael M. Fernandes, Ming Yi Link: http://arxiv.org/abs/2512.11341v2 Summary: This study demonstrates that an applied magnetic field induces momentum-dependent electronic structure symmetry breaking in the kagome superconductor CsV₃Sb₅. Using a self-developed tunable-field magneto-angle-resolved photoemission spectroscopy (magneto-ARPES) technique, the research team observed a momentum-selective response of the electronic structure to an external magnetic field. Specifically, within the charge density wave (CDW) phase, the van Hove singularity band of vanadium 3d orbitals near the K/K\u0026rsquo; points of the Brillouin zone exhibits a breaking of sixfold rotational symmetry (C₆) under the magnetic field: the originally mirror-symmetric spectral weight becomes anisotropic, and this anisotropy reverses with the reversal of the magnetic field direction, consistent with piezomagnetic effects and strong orbital selectivity. Meanwhile, the antimony 5p orbital electron pocket near the center of the Brillouin zone undergoes elliptical stretching under the magnetic field—an effect that persists above the CDW transition temperature, suggesting the presence of high-temperature fluctuations. The application of the magnetic field leads to selective broadening of the spectral weight of V-3d bands in different momentum branches, and the response shows symmetric inversion under opposite magnetic fields, clearly revealing the intertwining of time-reversal symmetry breaking and rotational symmetry breaking. The experiments also indicate that this time-reversal symmetry breaking originates from the van Hove singularity of vanadium at the onset of the CDW order. This work not only provides key constraints on the order parameter of the exotic CDW order in CsV₃Sb₅ but also demonstrates that the magnetic field can serve as an effective tuning tool to disentangle intertwined electronic orders in quantum materials in momentum space.\n12. Influence of ligand field and correlation on the electronic structure of NiO and CoO from DFT+DMFT calculations Relevance Score: 3.8676 Authors: Daniel Mutter, Frank Lechermann, Daniel F. Urban, Christian Elsässer Affiliations: University of Freiburg, Fraunhofer IWM, Ruhr-Universität Bochum Link: http://arxiv.org/abs/2605.03526v1 Summary: Using charge self-consistent density functional theory combined with dynamical mean-field theory (DFT+DMFT), we systematically investigated the electronic structures of paramagnetic NiO and CoO in both rock salt (RS) and zinc blende (ZB) structures. By analyzing the influence of octahedral and tetrahedral ligand fields on the spectral functions, and tuning the correlation strength of transition metal 3d electrons by varying the Hubbard parameter U (7–10 eV), we also employed the self-interaction correction (SIC) pseudopotential scheme to treat the correlation effects of oxygen 2p orbitals. The results show that the type of ligand field significantly affects the sublevel splitting of 3d orbitals, thereby altering the characteristics of the spectral function; increasing the U value enhances correlations, leading to an enlarged band gap and redistribution of spectral weight. After introducing a partial SIC (80%) for the oxygen 2p orbitals, the calculated spectral functions are in better agreement with experimental X-ray photoelectron and inverse photoemission spectra (XPS/BIS) in terms of both band gap size and peak positions. For the RS structure, both NiO and CoO exhibit charge-transfer insulator characteristics, whereas under the ZB structure, due to the weaker ligand field, the spectral functions show narrower bands and stronger localization features. By comparing different parameter settings, this study reveals the mechanism by which the interplay of ligand-field splitting, electron correlation, and p-d hybridization determines the electronic structure of transition metal oxides, providing a theoretical basis for understanding their applications in fields such as catalysis and optoelectronic devices.\n13. Universal Theory of Incoherent Metals Relevance Score: 3.8401 Authors: Aaron Kleger, Nikolay Gnezdilov, Rufus Boyack Link: http://arxiv.org/abs/2605.03013v1 Summary: This paper investigates the transport properties of incoherent metals in a non-perturbative manner using the two-dimensional Yukawa-SYK model, a system where fermions are spatially randomly coupled to quantum critical bosons. The model is exactly solvable in both strong and weak coupling regimes, yielding momentum-independent self-energies, which simplifies the calculation of electrical conductivity and shear viscosity. The main findings include: (1) In the weak-coupling low-temperature regime, the resistivity exhibits a linear temperature dependence, characteristic of strange metals; in the strong-coupling regime, the resistivity exceeds the Mott-Ioffe-Regel limit, manifesting as a bad metal. (2) A non-Boltzmann transport formula is derived, revealing a non-Drude relationship between resistivity and quasiparticle lifetime, and a modified scaling relation between transport lifetime and single-particle lifetime. (3) In the bad metal region, due to the dominance of bosonic entropy and the extremely high electron scattering rate, the ratio of shear viscosity to entropy density strongly violates the Kovtun-Son-Starinets bound, and this ratio decreases sharply with decreasing temperature. This work provides the first microscopic realization of a universal description of incoherent metals, offering a theoretical foundation for understanding the anomalous transport in the normal state of unconventional superconductors such as cuprates and heavy fermion systems.\n14. Sol-Gel-Derived NiO/ZnO Thin Films with Single and Heterostructure Layers for Electrochemical Energy Storage Relevance Score: 3.8311 Authors: Miss Nourin Nurain Amina, Md Noushad Hossain, Muhammad Shahriar Bashar, Munira Sultana, Md. Salahuddin Mina Link: http://arxiv.org/abs/2601.01479v2 Summary: This study employed a sol-gel method combined with non-vacuum spin-coating technology to prepare NiO/ZnO-based monolayer and heterostructure films on fluorine-doped tin oxide (FTO) substrates, and NaCl-doped ZnO was introduced to improve its relatively lower capacitive performance compared to NiO. The surface morphology, structural parameters, and optical properties of the films were characterized using scanning electron microscopy, X-ray diffraction, and UV-Vis spectroscopy. The results indicated that the direct bandgaps of ZnO and Na-ZnO ranged from 3.17 to 3.31 eV, while NiO exhibited a wider bandgap of 3.81 eV. The electrochemical performance was evaluated in a three-electrode system with 1 M KOH electrolyte using cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy. The results demonstrated that the specific capacitance of the monolayer NiO film was 1.391 F g⁻¹; in contrast, the NiO/ZnO heterostructure exhibited a synergistic effect, achieving a maximum specific capacitance of 1.627 F g⁻¹ at a current density of 2.0 mA cm⁻², significantly enhancing charge storage capability. Furthermore, sodium doping effectively improved the capacitive performance of ZnO. This work confirms the potential application of sol-gel-derived oxide heterostructures and doped films as low-cost, scalable electrode materials for supercapacitors in portable electronics and energy storage systems.\n15. First-Order Transitions in Weak Ising Spin-Orbit-Coupled Superconductors Relevance Score: 3.8007 Authors: Xusheng Wang, Gaomin Tang, Shuai-hua Ji Affiliations: Frontier Science Center for Quantum Information, Tsinghua University, China Academy of Engineering Physics Link: http://arxiv.org/abs/2605.03774v1 Summary: This paper investigates the phase transition behavior of weak Ising spin-orbit coupling (ISOC) superconductors under strong exchange fields using the free energy method, revealing the possibility of a first-order phase transition. The conventional approach based on the gap equation can only determine the supercooling field but fails to identify the thermodynamic critical field; free energy analysis, in contrast, accurately describes the thermodynamic critical field of first-order phase transitions. The study indicates that the phase diagram of weak ISOC superconductors is dominated by second-order phase transitions in the low- and high-temperature regions, with a first-order phase transition emerging in the intermediate temperature range. Additionally, two prominent in-gap coherence peaks are predicted in the quasiparticle spectrum, which characterize the features of the previously reported phantom gap states induced by weak ISOC. These results uncover distinct spectroscopic signatures in the weak ISOC regime and highlight the importance of free energy analysis in describing first-order phase transitions in Ising superconductors.\n16. Nb$_3$Sn Thin Films Using a Cu-Sn Route for Dark Matter Detection Relevance Score: 3.7993 Authors: Andre Juliao Affiliations: Florida State University Link: http://arxiv.org/abs/2605.03171v1 Summary: This paper investigates the preparation of Nb₃Sn thin films on copper substrates for axion dark matter detection, addressing the need for superconducting radio-frequency cavities. While conventional methods require high-temperature tin vapor diffusion at approximately 1100 °C, this study employs a high-tin Cu-Sn alloy to form Nb₃Sn through solid-state diffusion reaction with the niobium layer at 650–750 °C, a temperature compatible with copper substrates. By adjusting the composition of the Cu-Sn alloy, tin activity was optimized. Compositional analysis and thermal expansion calculations indicate that strain from the copper substrate suppresses the superconducting critical temperature below 18 K. To isolate the strain effect, comparative experiments were conducted on niobium and sapphire substrates. Two feasible routes were developed: Route 1, in which Cu-Sn is deposited on tantalum-coated copper followed by hot sputtering of niobium, yielding a Tc of 16 K; Route 2, in which niobium is deposited on tantalum-coated copper, followed by Cu-Sn evaporation and ex situ reaction, producing a more uniform Nb₃Sn layer and selected for cavity coating. Using Route 2, a hexagonal cavity was coated and tested at 50 mK in a 9 T magnetic field. At zero field, the quality factor Q reached 77,000, 40% higher than that of bare copper (55,000), but Q decreased sharply with increasing magnetic field. The study demonstrates that Nb₃Sn-coated copper cavities outperform bare copper at zero field, offering a practical approach to improving axion detectors and indicating directions for further optimization.\n17. Strong long-wavelength electron-phonon coupling in Ta$_2$Ni(Se,S)$_5$ Relevance Score: 3.7744 Authors: Zhibo Kang, Burak Gurlek, Weichen Tang, Xiang Chen, Jacob P. C. Ruff, Ahmet Alatas, Ayman Said, Robert J. Birgeneau, Steven G. Louie, Angel Rubio, Simone Latini, Yu He Link: http://arxiv.org/abs/2509.09620v1 Summary: This paper systematically investigates the low-energy phonon dynamic structure factors of the quasi-one-dimensional excitonic insulator candidate Ta₂NiSe₅ and its isostructural compound Ta₂NiS₅ using inelastic X-ray scattering (IXS) spectroscopy. In the semimetallic normal state of Ta₂NiSe₅, the 2 THz shear phonon at the long-wavelength limit exhibits strong anisotropic broadening and softening: the linewidth increases significantly along the L direction while remaining resolution-limited along the H direction. In contrast, this phonon broadening completely disappears in the symmetry-broken state of Ta₂NiSe₅ and in Ta₂NiS₅, which possesses a fully gapped normal state. By comparing the expected phonon lifetimes of excitonic insulators in the BCS and BEC limits, and combining density functional theory calculations with band structures fitted from angle-resolved photoemission spectroscopy, the analysis indicates that this phonon broadening primarily originates from interband electron-phonon coupling, rather than exciton-phonon coupling or excitonic phase-phonon interactions. The experiment quantitatively estimates the electron-phonon coupling vertex to be approximately 73 meV, with a dimensionless coupling constant g/ω₀ ∼ 10, marking the Ta₂Ni(Se,S)₅ family as a rare example of \u0026ldquo;ultra-strong coupling\u0026rdquo; materials. This work establishes high-resolution phonon spectroscopy as a universal criterion for distinguishing entangled phases with similar ground-state properties, such as density waves, structural instabilities, and excitonic insulators, and reveals quantum phenomena beyond the Born-Oppenheimer approximation, such as possible compressed phonon states under ultra-strong coupling conditions.\n18. Pressure-Tunable Generalized Wigner Crystal and Fractional Chern Insulator in twisted MoTe$_2$ Relevance Score: 3.6933 Authors: Bingbing Wang, Junxi Yu, Cheng-Cheng Liu Link: http://arxiv.org/abs/2504.11177v2 Summary: This paper demonstrates through theoretical calculations that pressure can effectively tune the flatness and quantum geometry of single-particle bands in twisted bilayer MoTe₂ (tMoTe₂). When the top valence band is fractionally filled, pressure serves as a flexible means to control the many-body topological phase transition between fractional Chern insulators (FCIs) and generalized Wigner crystals (GWCs). Employing a pressure-parameterized continuum model, the study defines a figure of merit for band flatness and analyzes geometric indicators such as Berry curvature and quantum metric. Using projected exact diagonalization, the many-body energy spectrum, many-body Chern number, particle entanglement spectrum, and static structure factor are computed at one-third filling, confirming that pressure can drive the system from an FCI phase (at zero or high pressure) to a GWC phase (at moderate pressure) and back to an FCI phase. The results reveal a clear correspondence between single-particle band geometry and the formation of FCIs and GWCs: band geometry close to that of the lowest Landau level favors FCIs, while deviations promote GWCs. This work provides a clean and efficient means of in situ tuning of strongly correlated topological states in moiré superlattices via pressure, and the predictions can be directly realized in near-term experiments.\n19. Magneto Transport and Spin Reorientation in Pt Co78Ho22 Heterostructures Near the Sublattice Compensation Temperature Relevance Score: 3.6740 Authors: Rajeev Nepal, Jose Flores, Aurain Seaton, Michael Newburger, John Derek Demaree, Ramesh C Budhani Affiliations: Air Force Research Laboratory, Morgan State University, DEVCOM Army Research Laboratory Link: http://arxiv.org/abs/2605.03982v1 Summary: Co78Ho22/Al thin films and Pt/Co78Ho22/Al heterostructures were prepared by multi-target magnetron sputtering to systematically investigate the transport behaviors of anomalous Hall resistivity, DC magnetization, and spin Hall magnetoresistance near the sublattice compensation temperature. X-ray diffraction, reflectivity, and atomic/magnetic force microscopy confirmed the structure and interfacial quality of the films. Experimental results revealed that both systems exhibit a sign reversal of anomalous Hall resistivity and unique wing-shaped hysteresis loops near the compensation temperature, accompanied by a minimum in saturation magnetization. After introducing a heavy Pt layer, the spin Hall magnetoresistance was significantly enhanced, the compensation temperature shifted, saturation magnetization increased, and the triple-loop (spin-flop) region expanded. These phenomena are attributed to interface-induced spin-flop transitions, spin-orbit torques, and the formation of 3d and 4f magnetic clusters due to microscopic phase separation. Owing to Ho possessing the largest orbital angular momentum among lanthanides, its unquenched orbital moment significantly influences magnetic anisotropy and transport. Spin current transport preferentially couples with the Co sublattice, allowing spin Hall magnetoresistance to persist near the compensation point while orbital magnetoresistance is suppressed. This study elucidates the mechanisms of sublattice magnetization reversal and interfacial spin scattering in ferromagnets with high sublattice angular momentum, offering new insights for compensated ferromagnetic spintronics.\n20. Umklapp correction to Landau damping and conditions for non-trivial modifications to quantum critical transport Relevance Score: 3.6547 Authors: Vibhu Mishra Link: http://arxiv.org/abs/2604.24274v2 Summary: This paper investigates particle-hole bubbles in a two-dimensional Ising-nematic metal when the critical Fermi surface approaches the Brillouin zone boundary, and computes the Landau damping correction in the boson self-energy. The main approach employs fermionic free propagators and performs analytical calculations under the patch approximation for both antipodal points on the Fermi surface and Umklapp scattering channels. The results show that the standard antipodal contribution yields Π_ATP ∝ Ω/q, while the Umklapp contribution from electrons near the zone boundary gives Π_U ∝ Ω^α at the minimal Umklapp momentum q ≈ Δ_q, with α = 2/3 (low temperature) or 1/2 (high temperature). This new frequency dependence differs from the standard critical scaling (z=3). For resistivity, at high temperatures (α=1/2), the lowest temperature T_U, originally expected to scale as ∝ Δ_q^3 for activating linear or quasi-linear resistivity, may be reduced to T_U ∝ Δ_q^4 due to the √Ω term. However, the paper points out that such a reduction can only be self-consistently realized in the \u0026ldquo;naive large-N limit\u0026rdquo; (large number of fermion flavors, single boson field) under specific hierarchical conditions; under more physical parameters (e.g., the Yukawa-SYK model), the correction effects are suppressed, and the critical scaling remains dominated by the antipodal contribution. In the three-dimensional case, the Umklapp contribution always yields Π_U ∝ Ω, thus not altering T_U, and has no substantial impact on heavy-fermion critical transport. In summary, Umklapp corrections introduce non-trivial frequency dependence, but in realistic systems, they are typically insufficient to alter the critical transport scaling; only in the special large-N limit might they cause a reduction in the activation temperature scale for resistivity.\n","permalink":"https://nickelates.uk/en/posts/2026-05-06-arxiv-daily/","summary":"\u003cblockquote\u003e\n\u003cp\u003e\u003cstrong\u003eDaily Overview\u003c/strong\u003e:\nToday\u0026rsquo;s overview of the nickelate superconductor field focuses on magnetic studies of bilayer La₃Ni₂O₇ single crystals. Using neutron scattering techniques, this work, for the first time under ambient pressure, clarifies the spin excitation energy gap, in-plane anisotropic dispersion, and bilayer periodic modulation in this material, directly confirming the existence of interlayer antiferromagnetic coupling. A bilayer Heisenberg model based on stripe-type magnetic order successfully describes the experimental dispersion and reveals that its spin-wave bandwidth is only about 25% of that in cuprates, yet the total fluctuating magnetic moment at comparable energies is similar to that in cuprates, establishing a magnetic framework distinct from cuprates. These results provide key constraints on the magnetic order and spin dynamics for understanding the possible high-temperature superconductivity mechanism in bilayer nickelate systems.\u003c/p\u003e","title":"arXiv Daily: Nickelate superconductors 2026-05-06"},{"content":" Daily Overview: Here is the English translation of the provided Chinese daily paper overview: \u0026gt; \u0026mdash; \u0026gt; Today\u0026rsquo;s Research Overview in the Nickelate Superconductor Field \u0026gt; Two research works today deepen our understanding of the superconducting mechanism in layered nickel oxides from the perspectives of structural and electronic phase transitions, as well as the relationship between electronic ordered phases and superconductivity. \u0026gt; First, a team from Université Paris-Saclay and other institutions systematically mapped the temperature-pressure phase diagram of the bilayer nickelate La₃Ni₂O₇ using high-pressure high-temperature Raman and infrared spectroscopy. They discovered that a pressure-induced lattice tilt-to-untilt structural phase transition is accompanied by a nearly two-order-of-magnitude increase in carrier concentration, and superconductivity is observed near the phase boundary. This work establishes a direct link between structural and electronic property changes, providing a key experimental foundation for understanding its high-pressure superconducting mechanism. \u0026gt; Meanwhile, another study led by Brookhaven National Laboratory and other institutions focuses on bilayer nickelate La₂PrNi₂O₇ thin films. Using resonant X-ray scattering and spectroscopy, they provide strong evidence that the spin density wave (SDW) is not a precursor state of superconductivity but rather a competing phase associated with oxygen vacancies. The work further proposes that in the superconducting phase, regions with intact oxygen stoichiometry have a ground state characterized by robust interlayer five-spin polaron states, which lock out-of-plane orbitals and render the in-plane orbital behavior close to the classical electronic configuration of cuprates and infinite-layer nickelates. \u0026gt; In summary, these studies not only elucidate the structural origin of pressure-driven superconductivity but also reveal the key regulatory role of oxygen stoichiometry in electronic states and the superconducting/competing phase balance, offering new perspectives for exploring the microscopic mechanism of nickelate superconductivity.\n1. Metallic crossover through the tilt-free transition in La$_3$Ni$_2$O$_7$ at high pressure and temperature Relevance Score: 6.0119 Authors: Bastien Michon, Yingpeng Yu, Beatrice D\u0026rsquo;Alò, Elena Stellino, Gergely Németh, Bosen Wang, Jianping Sun, Jinguang Cheng, Paolo Postorino, Ferenc Borondics, Francesco Capitani Affiliations: Université Paris-Saclay Link: http://arxiv.org/abs/2605.01651v1 Summary: This paper systematically investigates the pressure-induced structural phase transition and its effect on the electronic properties of bilayer nickel oxide La₃Ni₂O₇ using high-pressure and high-temperature Raman spectroscopy combined with synchrotron infrared reflectance spectroscopy. Experiments reveal that at room temperature, as the pressure increases from 0.8 GPa to 17 GPa, the material undergoes a continuous structural transition from a tilted Amam orthorhombic phase to an untilted Fmmm (or I4/mmm) phase, with the transition occurring in the range of approximately 6–15.25 GPa. Under high pressure, the phonon modes at 360 cm⁻¹ and 565 cm⁻¹ gradually broaden, soften, and ultimately disappear, while Fano lineshapes emerge, indicating enhanced electron-phonon coupling. High-temperature experiments show that the upper temperature limit of this structural transition at ambient pressure is 544 K. Infrared reflectance measurements indicate that as pressure increases, the plasma frequency jumps from 3450 cm⁻¹ (0.4 GPa) to 32,000 cm⁻¹ (16.9 GPa), corresponding to an increase in carrier density by nearly two orders of magnitude, marking a metal-to-metal crossover from a bad metal to a good metal. Based on these results, this paper constructs a temperature-pressure phase diagram, clearly defining the boundaries of the tilted phase, the coexistence region, and the untilted phase. Superconductivity (with T_c around 80 K) is found to occur near the structural transition boundary (around 6–7 GPa), closely related to the increase in carrier density and the enhancement of electron-phonon coupling. These findings establish a direct link between structural transition and electronic properties, providing key experimental evidence for understanding the superconducting mechanism in layered nickel oxides.\n2. Interlayer Five-Spin Polaron in Superconducting Bilayer Nickelates Relevance Score: 5.8975 Authors: Jiarui Li, Christopher T. Parzyck, Eder G. Lomeli, Yidi Liu, Taehun Kim, Heemin Lee, Zengqing Zhuo, Eun Kyo Ko, Yaoju Tarn, Cheng-Tai Kuo, Ronny Sutarto, Chunjing Jia, Vivek Thampy, Brian Moritz, Yijun Yu, Jun-Sik Lee, Valentina Bisogni, Thomas P. Devereaux, Harold Y. Hwang, Wei-Sheng Lee Affiliations: Brookhaven National Laboratory, Lawrence Berkeley National Laboratory, SLAC National Accelerator Laboratory, Canadian Light Source, University of Florida, Stanford University Link: http://arxiv.org/abs/2605.02891v1 Summary: This study systematically investigates the relationship between spin density wave (SDW) and superconductivity in bilayer nickelate superconductor La₂PrNi₂O₇ thin films using resonant X-ray scattering and spectroscopy. It is found that in superconducting samples, SDW signals appear only in locally sparse regions (such as sample edges or beneath electrodes), while the majority of regions (i.e., areas with complete oxygen stoichiometry) exhibit no SDW signal. Conversely, in oxygen-deficient non-superconducting samples, SDW is uniformly and strongly distributed throughout the entire film. This indicates spatial phase separation between SDW and superconductivity: regions with complete oxygen stoichiometry are free of SDW and exhibit superconductivity, whereas oxygen-deficient regions stabilize SDW and suppress superconductivity. Ni-L₃ and O-K edge spectra reveal that the superconducting phase possesses a metallic (small or negative charge transfer) ground state, primarily characterized by Ni d⁸ and significant oxygen ligand hole features, while the oxygen-deficient phase displays localized excitation peaks. O-K edge XAS and RIXS further demonstrate that oxygen deficiency modulates the spectral weight of in-plane Zhang-Rice singlet and apical ligand hole states, with particular sensitivity to the c-axis electronic structure. Combined with theoretical analysis, the study proposes that in the superconducting ground state, ligand holes are predominantly located at interlayer apical oxygen sites, forming robust interlayer five-spin polaron states (Ni(d⁸)-O(L)-Ni(d⁸)). This state locks the spin and charge configuration of the out-of-plane 3dₓ²₋ᵧ² orbitals, rendering the in-plane 3dₓ²₋ᵧ² orbitals nearly half-filled, analogous to the 3d⁹ characteristic of cuprates and infinite-layer nickelates. Therefore, oxygen stoichiometry is a critical parameter for tuning interlayer coupling and electronic structure in bilayer nickelates, and SDW is not a superconducting precursor but rather a competing phase induced by oxygen vacancies.\n3. Vortex Transport in Ni/Bi Bilayer Superconductor with Strong Spin-Orbit and Exchange Interaction Relevance Score: 5.0861 Authors: Laxmipriya Nanda, Sohini Guin, Yasen Hou, Rajib Sarkar, Naresh Shyaga, Souvik Banerjee, A. Sundaresan, N. S. Vidhyadhiraja, Jagadeesh S. Moodera, Dhavala Suri Link: http://arxiv.org/abs/2605.02677v1 Summary: This study systematically investigates interface superconductivity in Ni/Bi bilayer heterostructures through longitudinal and transverse magnetotransport measurements. The Ni/Bi system combines ferromagnetic Ni with Bi, a metal exhibiting strong spin-orbit coupling. Although the individual components only become superconducting below 10 mK, the bilayer structure displays a superconducting transition temperature of approximately 3-4 K. To elucidate the superconducting mechanism, we performed magnetotransport experiments near the critical temperature (Tc) and analyzed the data using a vortex force-balance model incorporating Magnus and viscous forces. The results reveal that under a perpendicular magnetic field, the motion of isolated vortices generates an antisymmetric transverse resistance peak resulting from the competition between Magnus and viscous forces. Control experiments using the ferromagnetic insulator EuS confirm that superconductivity pervades the entire bilayer film rather than being confined to the interface. Further analysis indicates that the superconducting state is quasi-two-dimensional and exhibits Berezinskii-Kosterlitz-Thouless (BKT)-type phase transition behavior. Fitting with the anisotropic Ginzburg-Landau model yields a coherence length anisotropy ratio of approximately 3.5. Ultimately, the experimental results are fully consistent with the vortex dynamics picture for conventional s-wave pairing order parameters, while any contribution from unconventional pairing (e.g., spin-triplet) is extremely weak. This study provides a unified framework for understanding superconducting transport in environments with strong spin-orbit coupling and magnetism.\n4. Two distinct superconducting regimes in Ti4Co2O under pressures Relevance Score: 4.7934 Authors: Lifen Shi, Keyuan Ma, Binbin Ruan, Zhen Wang, Pengtao Yang, Zhian Ren, Jianping Sun, Gang Li, Fabian O. von Rohr, Bosen Wang, Jinguang Cheng Affiliations: University of Chinese Academy of Sciences, Max Planck Institute for Chemical Physics of Solids, Chinese Academy of Sciences, University of Geneva Link: http://arxiv.org/abs/2605.01893v1 Summary: Through electrical transport measurements of the Ti4Co2O superconductor under pressure, the superconducting transition temperature Tc exhibits a non-monotonic variation: initially increasing monotonically with a coefficient of dTc/dP ≈ 0.034 K/GPa, then rapidly decreasing in the 10–20 GPa range, followed by a continuous increase with a coefficient of dTc/dP ≈ 0.023 K/GPa up to 4.31 K at 69.7 GPa. Meanwhile, the upper critical field Bc2(0) shows a dome-shaped pressure dependence, reaching a maximum at 5 GPa (approximately twice its ambient-pressure value), and exceeding the Pauli paramagnetic limit of the weak-coupling BCS theory across the entire pressure range. By comparing the properties of the normal state and the superconducting state, two distinct superconducting regions can be identified: the low-pressure region (\u0026lt;12 GPa) exhibits enhanced Bc2(0) and Fermi liquid-type electrical transport (exponent n ≈ 2); the high-pressure region (\u0026gt;20 GPa) shows a monotonic increase in Tc and enhanced phonon scattering (exponent n ≈ 4). Room-temperature synchrotron X-ray diffraction reveals no structural phase transition up to 55.8 GPa, with a bulk modulus of approximately 192 GPa, higher than that of other alloy superconductors. First-principles calculations indicate that the non-monotonic variation in Tc is closely related to the evolution of the density of states in Ti4Co2O under compression, differing from the isostructural Ti4Ir2O and Nb4Rh2C superconductors. The results demonstrate that even in Ti4Co2O with weak spin-orbit coupling, superconductivity is highly sensitive to external stimuli such as pressure.\n5. Impurity-Scattering Assisted Umklapp Scattering as the Origin of Low-Temperature Resistivity in the Normal-State of Cuprate Superconductors Relevance Score: 4.5323 Authors: Xingyu Ma, Minghuan Zeng, Huaiming Guo, Shiping Feng Link: http://arxiv.org/abs/2605.01316v1 Summary: Based on the microscopic electronic structure of cuprate superconductors, this paper systematically investigates the normal-state low-temperature resistivity behavior from the underdoped pseudogap phase to the overdoped strange metal phase. In this study, the authors employed the t-J model and the fermion-spin transformation method, and derived the contribution of impurity-assisted spin excitation Umklapp scattering to resistivity using the Boltzmann transport equation. The results show that the low-temperature resistivity behavior depends simultaneously on impurity scattering and Umklapp scattering: impurity scattering restricts the correction of the distribution function to the antinodal region, while impurity-assisted Umklapp scattering (mediated by spin excitations) is central to the temperature dependence of resistivity. In the overdoped strange metal phase, the resistivity exhibits a linear temperature dependence (T-linear) in the low-temperature region (above a certain temperature scale); whereas in the underdoped pseudogap phase, the opening of the spin pseudogap suppresses the density of spin excitation states near the antinodal region, weakening the Umklapp scattering intensity there, and consequently leading to a quadratic temperature dependence (T-quadratic) of resistivity. This temperature scale is similar to the crossover temperature of the antinodal spin pseudogap and varies with doping. This work provides a clear microscopic mechanism for understanding the anomalous transition of the normal-state resistivity in cuprates from T-linear to T-quadratic, emphasizing the critical role of the synergistic effect between impurity scattering and Umklapp scattering.\n6. Interfacial charge-induced adsorption mode for electron pairing in high-temperature superconductors Relevance Score: 4.2218 Authors: Jiu Hui Wu, Hua Tian, Kejiang Zhou Affiliations: Zhejiang University, Xi\u0026rsquo;an Jiaotong University Link: http://arxiv.org/abs/2605.02619v1 Summary: This paper proposes an electronic pairing mechanism for high-temperature superconductors—the interface charge-induced adsorption mode. Taking the YBa₂Cu₃O₇ superconductor as an example, it is found that electrons couple with the valence-flexible state of oxygen ions through the adsorption potential, forming a charge-modulated interfacial layer near the CuO₂ plane. Within this interfacial layer, electrons generate strong attractive forces by sharing an optimized interface structure and exchanging adsorption modes, thereby forming Cooper pairs. The paper derives in detail the effective interaction potential between electrons and the electron–adsorption mode coupling strength, with the adsorption coupling constant reaching 43.4. By analyzing the anisotropy of the interfacial adsorption force, the origin of d-wave pairing symmetry is explained, and the pseudogap behavior is elucidated. Using the one-dimensional Ginzburg–Landau equation in the absence of a magnetic field, an expression for the coherence length is obtained, with calculated values closely matching those reported in the literature. By establishing the gap equation, the superconducting gap is found to be approximately 18.37 meV, which is highly consistent with the 17 meV measured by scanning tunneling microscopy/spectroscopy. These quantitative predictions validate the effectiveness of this theoretical framework. This mechanism attributes electron pairing in high-temperature superconductors to selective condensation driven by the interfacial adsorption potential, providing a new perspective for understanding the anomalous properties of cuprate superconductors.\n7. Topological flat bands emerging at the inversion of stacking order in rhombohedral graphite Relevance Score: 3.9606 Authors: R. Weht, A. A. Aligia, M. Nunez-Regueiro Link: http://arxiv.org/abs/2605.01115v1 Summary: This study investigates the electronic band structures of different stacking configurations in rhombohedral graphite using first-principles calculations, with particular focus on potential flat bands near the Fermi level. When two opposite rhombohedral stacking sequences (ABCABC\u0026hellip; and CBACBA\u0026hellip;) meet at an interface, calculations reveal topological flat bands near the K and K\u0026rsquo; points in the Brillouin zone. By mapping the tight-binding model perpendicular to the graphene layers onto Su-Schrieffer-Heeger (SSH) chains, the physical origin of these flat bands is clearly understood: at the stacking inversion interface, the effective SSH model lies in a topological phase, giving rise to topologically protected zero-energy edge states near the interface. Unlike Bernal-rhombohedral interfaces, where flat-band states are localized in the Bernal region rather than at the interface, the charge density of flat-band states at the rhombohedral inversion interface is precisely concentrated on the stacking inversion interface layer and its adjacent layers. It is found that when the distance between two inversion interfaces decreases, the states from different interfaces hybridize, opening a small gap between the flat bands. Meanwhile, as the two-dimensional wave vector moves away from the K/K\u0026rsquo; point, the effective SSH model transitions from a topological phase to a trivial phase, causing the localized low-energy states to disappear. Additionally, the article predicts that increasing pressure enhances interlayer hopping, thereby expanding the momentum-space extent of the flat bands, which is expected to raise the superconducting transition temperature. This work suggests that naturally occurring stacking inversion interfaces in rhombohedral graphite may provide an ideal platform for high-temperature superconductivity, with interface flat bands offering advantages over surface flat bands, as external surfaces are susceptible to scattering damage from Bernal or AA stacking defects, while internal interfaces are typically sharper and more regular.\n8. Topological Ising superconductivity in two-dimensional p-wave magnet Relevance Score: 3.9386 Authors: Kyoung-Min Kim, Gibaik Sim, Moon Jip Park Link: http://arxiv.org/abs/2605.01686v1 Summary: This paper investigates topological superconductivity in two-dimensional p-wave magnets, employing an extended Hubbard model (including onsite attraction and nearest-neighbor attraction) and solving superconducting instabilities via the Bogoliubov-de Gennes (BdG) method. In this model, the odd-parity exchange field breaks the inversion symmetry of the spin-split electronic structure, causing singlet (s-wave) and triplet (p-wave) order parameters to mix within the same A1 symmetry channel. It is found that the dominant instability is a coupled s+p_x Ising state, whose singlet-triplet balance can be continuously tuned by the relative strength of the nearest-neighbor attraction. When the triplet gap amplitude exceeds that of the singlet, the system enters a nodal topological superconducting phase, characterized by Majorana edge states protected by the momentum-resolved winding number. These edge states exist over a finite momentum interval, whose boundaries correspond to the surface projections of bulk point nodes. Additionally, a Zeeman field perpendicular to the exchange field can induce a Z2 topological superconducting phase in the singlet-dominated gap region. This work reveals the potential of p-wave magnets as a platform for nonrelativistic topological superconductivity, where the exchange splitting strength is much larger than that of conventional spin-orbit coupling, enabling more robust topological protection.\n9. Revisiting the surface density of states of midgap Andreev edge states Relevance Score: 3.8264 Authors: Gota Sato, Yasushi Nagato, Seiji Higashitani Link: http://arxiv.org/abs/2605.02423v1 Summary: This paper re-examines the effect of surface roughness on midgap Andreev edge states (MAES) in p-wave and d-wave superconductors. Under perfectly specular reflection surfaces, MAES form flat bands at the Fermi level, leading to sharp midgap peaks in the surface density of states (SDOS). Previous theoretical studies have shown that MAES in p-wave and d-wave superconductors respond differently to surface roughness: in the d-wave case, diffusive scattering significantly broadens the midgap peak of SDOS and creates a V-shaped structure near the Fermi level, whereas the midgap peak in the p-wave case remains robust against diffusive scattering. Using the quasiclassical Green\u0026rsquo;s function framework and a random R-matrix model, this paper clarifies the physical origin of this contrasting behavior. A key finding of the analysis reveals that the flat band in the d-wave state consists of two distinct types of MAES modes; diffusive scattering between these modes leads to significant broadening of the midgap peak and the formation of a V-shaped structure. In contrast, the flat band in the p-wave state contains only a single MAES mode, so diffusive scattering merely causes a uniform redistribution of spectral weight, leaving the zero-energy peak sharp. These results reveal the microscopic mechanism underlying the response of MAES to surface roughness and provide new insights into the properties of superconducting surfaces.\n10. Spin-polarized Josephson current induced by inhomogeneous altermagnetic interlayers Relevance Score: 3.7731 Authors: Wenjun Zhao, Yuri Fukaya, Pablo Burset, Jorge Cayao, Yukio Tanaka, Bo Lu Link: http://arxiv.org/abs/2605.02140v1 Summary: We study a Josephson junction consisting of two alternating magnetic layers sandwiched between superconducting electrodes, where each alternating magnetic layer possesses an in-plane Néel vector with identical strength. Using the tight-binding model and the recursive Green\u0026rsquo;s function method, we calculate the Josephson charge and spin currents. The results show that when the Néel vectors of the two layers are antiparallel (π orientation) and the layers have equal thickness, the spatial oscillations of the superconducting pair amplitude driven by the center-of-mass momentum cancel each other, effectively suppressing the single-layer pair-breaking effect. This significantly enhances the critical current and eliminates the 0-π transition; in this case, the critical current decays monotonically with junction length without oscillatory behavior. In contrast, under a parallel configuration, the critical current exhibits rapid oscillatory decay. Furthermore, when the Néel vectors are arranged non-collinearly, the system generates a net spin-polarized Josephson current, which exists even at zero phase bias, and its sign and magnitude can be highly tuned via crystal orientation. This spin current is a direct manifestation of spin-triplet pairing correlations, arising from spin-dependent momentum shifts in the alternating magnetic exchange field. Our work provides a new platform for realizing field-free, highly tunable, dissipationless spintronic devices.\n11. Composition-Driven Tunable Optical and Electrical Properties in Van der Waals Ferroelectric NbOI2-xClx Alloys Relevance Score: 3.6258 Authors: Gaolei Zhao, Juhe Liu, Jinkai Huo, Tian Han, Yunhao Tong, Hu Wang, Konstantin Kozadaev, Andrei Zheltkovich, Changsen Sun, Alexei Tolstik, Andrey Novitsky, Lujun Pan, Dawei Li Affiliations: Dalian University of Technology, Belarusian State University, Belarusian National Technical University Link: http://arxiv.org/abs/2605.01285v1 Summary: Here is the English translation of the provided Chinese academic summary: High-quality, full-composition-range van der Waals ferroelectric alloys NbOI2-xClx were successfully synthesized via chemical vapor transport, achieving composition-driven tunability of optical and electrical properties. Through a combination of experimental characterization and first-principles calculations, it was found that the lattice constants, phonon modes, and band structures of the alloys can be continuously tuned between NbOI2 and NbOCl2. The intensity and polarization pattern of the second harmonic generation signal vary significantly with Cl content: the intensity monotonically decreases, and the polarization pattern evolves from a four-lobed to a two-lobed shape, providing optical evidence for the tunability of in-plane ferroelectricity. Field-effect transistors based on these alloys exhibit stable n-type semiconductor behavior, with threshold voltage and carrier mobility precisely adjustable via the I/Cl molar ratio. Furthermore, full-composition two-dimensional NbOI2-xClx photodetectors demonstrate excellent gate-tunable current on/off ratios and strong polarization-sensitive photoresponse. This study provides a novel van der Waals ferroelectric material platform with tunable optical and electrical properties, paving the way for its applications in modern nanophotonics and nanoelectronics.\n12. Geometric Percolation Threshold Defines Half-Metallic Window in Vacancy-Doped Titanium disulfides Relevance Score: 3.6094 Authors: Shrestha Dutta, Rudra Banerjee Affiliations: SRM Institute of Science and Technology Link: http://arxiv.org/abs/2605.01754v1 Summary: This study reveals the geometric percolation mechanism of the insulator-to-half-metal transition in vacancy-doped monolayer 1T-TiS₂ through first-principles calculations (density functional theory combined with Hubbard U correction) and percolation theory analysis. Methodologically, the GGA+U method is employed to compute the electronic structure, and a continuous percolation model is constructed based on self-consistent charge densities, with the Hoshen-Kopelman algorithm used to identify vacancy network clusters. The main conclusions are as follows: The breaking of crystal field symmetry (O_h → C_{4v}) stabilizes the Ti 3d_{z²} orbital, generating a local magnetic moment of approximately 0.94 μ_B, yet spin-polarized transport requires these moments to form a spanning cluster. At the critical vacancy concentration x_c ≈ 12.5%, the percolation transition transforms the majority-spin impurity band from a localized state (bandwidth \u0026lt; 0.1 eV) into a dispersive state (bandwidth of 1.5 eV), achieving 100% spin polarization with a minority-spin band gap of 1.0 eV. Finite-size scaling yields a Fisher exponent τ = 2.09 ± 0.03, consistent with the two-dimensional percolation universality class. Supercell size effects validate this mechanism: at the same concentration, the 2×2 supercell exhibits antiferromagnetic order, while the 4×4 supercell, due to the formation of a spanning cluster, displays ferromagnetic order. The Curie temperature is estimated to exceed 300 K via exchange coupling calculations, and geometric blocking instability in the network is observed for x \u0026gt; 20%. Ultimately, the half-metallic functionality window is identified as 11% \u0026lt; x \u0026lt; 15%, establishing geometric connectivity as a quantitative design principle for defect-engineered two-dimensional spintronics.\n13. Multi-probe detection of domain nucleation across the metal-insulator transition in VO$_2$ Relevance Score: 3.6073 Authors: Shubhankar Paul, Giordano Mattoni, Amitava Ghosh, Pooja Kesarwani, Dipak Sahu, Monika Ahlawat, Ashok P, Amit Verma, Vishal Govind Rao, Chanchal Sow Link: http://arxiv.org/abs/2605.01314v1 Summary: This paper systematically investigates the nucleation and distribution of domains in vanadium dioxide (VO₂) thin films during the metal-insulator transition (MIT) using a multi-probe approach. VO₂ thin films with different grain sizes (P-VO₂ ~40 nm, S-VO₂ ~20 nm) were prepared via pulsed laser deposition (PLD) and direct current magnetron sputtering. Combining macroscopic electrical transport measurements, first-order reversal curve (FORC) analysis, and infrared thermography, the evolution of domain distribution was elucidated at both macroscopic and microscopic scales. The FORC distribution reveals that the large-grain P-VO₂ sample exhibits a single peak, corresponding to a uniform domain distribution and a symmetric thermal hysteresis loop (hysteresis width ~9 K). In contrast, the small-grain S-VO₂ sample displays a bimodal distribution, indicating the presence of two distinct domain distributions (D1 and D2), which is attributed to the stabilization of supercooled metallic domains within the insulating matrix, leading to asymmetric thermal hysteresis (hysteresis width ~16 K). Coordinate-transformed FORC diagrams further confirm that P-VO₂ exhibits unidirectional irreversibility, corresponding to a single conduction path, while S-VO₂ exhibits bidirectional irreversibility, corresponding to multiple conduction paths. Infrared imaging visually demonstrates the nucleation and growth of metallic domains during the phase transition: in P-VO₂, metallic domains nucleate continuously from the bottom of the sample and coalesce; in S-VO₂, nucleation sites are sparse and dispersed, forming multidirectional conduction paths. This study establishes correlations among growth conditions, inter-domain interactions, and domain nucleation processes, indicating that reduced grain size introduces more surface states and grain boundary strain, promoting the formation of metastable supercooled metallic domains and thereby altering the MIT pathway. This multi-probe quantitative analysis provides important insights for understanding domain dynamics in electronic phase transitions of strongly correlated systems.\n14. Collinear ferromagnetism with reduced moment length in kagome magnet Nd3Ru4Al12 Relevance Score: 3.5040 Authors: Yuki Ishihara, Ryota Nakano, Rinsuke Yamada, Takuya Nomoto, Priya R. Baral, Moritz M. Hirschmann, Kamini Gautam, Kamil K. Kolincio, Akiko Kikkawa, Seno Aji, Hiraku Saitoh, Masaaki Matsuda, Yasujiro Taguchi, Taka-hisa Arima, Yoshinori Tokura, Taro Nakajima, Max Hirschberger Link: http://arxiv.org/abs/2605.01447v1 Summary: Through single-crystal neutron diffraction and polarized neutron experiments, this study determined the magnetic ground state of the kagome lattice magnet Nd₃Ru₄Al₁₂. The experiments revealed that this material is a collinear ferromagnet (hex-FM state), with all Nd sites exhibiting a uniform magnetic moment length (approximately 2.1 μB/Nd) and a magnetic ordering wavevector Q=0. This result overturns the previously proposed orthogonal ferromagnetic (ortho-FM) model, which assumed unequal magnetic moments at two inequivalent Nd sites. Analysis of the flipping ratio in polarized neutron scattering further confirmed the hex-FM state and ruled out the possibility of in-plane magnetic moment canting. Based on the experimental data, this work provides a microscopic basis for understanding the significant Hall effect and Nernst effect induced by thermal fluctuations near the Curie temperature TC ≈ 41 K in Nd₃Ru₄Al₁₂. Additionally, electronic structure calculations indicate that the ortho-FM state is unstable and tends to transform into the hex-FM state, with the measured orbital magnetic moment being suppressed. In summary, this study clarifies the magnetic differences between light rare-earth elements (such as Nd) and heavy rare-earth elements (such as Gd, Tb, etc.) in this class of compounds: the former exhibits simple collinear ferromagnetism, while the latter displays complex antiferromagnetic ordering, thereby explaining the deviation from the De Gennes scaling relation.\n15. Dirac Semimetal Phase in Rhombohedral $β-$Cu$_{2}$Se Relevance Score: 3.4597 Authors: Thomas Steele, Becker Sharif, David Lederman, Xiangang Wan, Sergey Y. Savrasov Link: http://arxiv.org/abs/2605.01142v1 Summary: Based on first-principles calculations within density functional theory, this work predicts that the rhombohedral phase β-Cu₂Se is an ideal Dirac semimetal. It is found that, in the bulk electronic structure of this phase, there exist two Dirac points near the Fermi level along the kz direction of the Brillouin zone, which are protected by C₃z symmetry and precisely pinned at the Fermi level. By comparing the band evolution of the cubic phase α-Cu₂Se and the rhombohedral phase β-Cu₂Se, it is revealed that the structural phase transition from cubic to rhombohedral (analogous to applying tensile strain along the (111) direction) opens a gap at the original quadratic contact points, while maintaining linear-crossing Dirac dispersion along specific directions. Surface state calculations are performed using a tight-binding method to construct a thin-layer model of the (100) surface, and Fermi arc surface states connecting the projections of the two Dirac points are identified in the surface Brillouin zone. These Fermi arcs exhibit a helical spin texture similar to that of topological insulators: electron spins are perpendicular to their velocity direction, and only near the Dirac point projections do they adopt a \u0026ldquo;all-in/all-out\u0026rdquo; arrangement. This unique spin texture, together with the shape of the Fermi arcs, suppresses both backscattering and side-scattering effects in surface transport (the orthogonal spin states of opposite momenta result in zero scattering matrix elements), suggesting that surface electrons can achieve ultrahigh carrier mobility and strongly anisotropic conductivity. This work proposes that the Dirac semimetal phase of β-Cu₂Se, along with its topologically protected Fermi arc surface states, provides a new material platform for designing high-mobility electronic devices, with transport properties potentially analogous to the strong quantum oscillations and large magnetoresistance effects observed in the reported Dirac semimetal Cd₃As₂ and Weyl semimetal NbAs.\n16. Quantum Limits of Electronic Transport in Nanostructured Macroscopic Conductors Relevance Score: 3.4271 Authors: Agnieszka E. Lekawa-Raus, John S. Bulmer, Teresa Kulka, Magdalena Marganska, Nick Papior, Dwight G. Rickel, Fedor F. Balakirev, Jacek A. Majewski, Krzysztof Koziol, Karolina Z. Milowska Affiliations: Warsaw University of Technology, Ikerbasque, Basque Foundation for Science, CIC nanoGUNE Link: http://arxiv.org/abs/2605.02295v1 Summary: This paper proposes a unified atomic framework (Landauer–Peierls–Molecular–Dynamics) that integrates quantum coherent transport, thermal disorder, and magnetic field effects, combined with wide-temperature-range ultrahigh-field magnetotransport measurements up to 60 T, to investigate electronic transport in carbon nanotube fibers. The study reveals that positive magnetoresistance is controlled by junction overlap length, while negative magnetoresistance primarily arises from lattice-mismatched heterojunctions rather than being solely caused by weak localization. Statistical analysis of a large-scale numerical dataset demonstrates that the experimentally observed positive quadratic magnetoresistance originates from junction transport. These results confirm that macroscopic transport in disordered low-dimensional networks is predominantly governed by junction-level quantum interference, rather than being determined solely by defects or doping.\n17. Evidence for altermagnetic order in Cr-doped FeSb2 Relevance Score: 3.3704 Authors: A K M Ashiquzzaman Shawon, Eoghan Downey, Shane Smolenski, Thomas J. Hicken, Amir Henderson, Mingyu Xu, Trisha Musall, Rafael Lopes Sabainsk, Yuan Zhu, Weiwei Xie, Elena Gati, Lu Li, Zurab Guguchia, Na Hyun Jo Link: http://arxiv.org/abs/2605.01088v1 Summary: In this paper, we synthesize Fe₁₋ₓCrₓSb₂ single crystals (with a focus on Fe₀.₈₅Cr₀.₁₅Sb₂) and, by combining electrical transport, magnetic susceptibility, and muon spin relaxation (μSR) measurements, reveal a potential altermagnetic ordered ground state in this system. Magnetic susceptibility measurements indicate the emergence of spin-compensated order below approximately 3.5 K, with magnetic moments aligned along the crystallographic b direction. The transport properties exhibit a crossover from large positive magnetoresistance to negative magnetoresistance at low temperatures, accompanied by the observation of an anomalous Hall effect below 3.5 K, demonstrating the breaking of time-reversal symmetry with zero net magnetization. Muon spin relaxation experiments further confirm the existence of bulk magnetic order, which originates from the material itself rather than impurity phases. These results support the transition of Cr-doped FeSb₂ into an altermagnetic ordered state at low temperatures, characterized by compensated magnetic moments and broken time-reversal symmetry, consistent with theoretical predictions of altermagnetic behavior.\n18. Field-induced metal-insulator transition, Chern insulators, and topological semimetals in a clean magnetic semiconductor GdGaI Relevance Score: 3.3695 Authors: Kazuki Guzman, Hiroaki Ishizuka Affiliations: Institute of Science Tokyo Link: http://arxiv.org/abs/2605.01804v1 Summary: This study focuses on the electronic structure and topological phase transitions in the clean magnetic semiconductor GdGaI under non-coplanar magnetic order (four-sublattice triple-(q) order). Based on first-principles results, the authors construct an effective (k \\cdot p) theoretical model that couples the Ga (4p) hole pocket at the (\\Gamma) point with three Gd (5d) electron pockets at the (M) points through four exchange channels, thereby describing the influence of magnetic order on the band structure. The study finds that in the antiferromagnetic umbrella state (with zero net magnetization), the phase diagram includes a trivial insulator (Chern number (C=0)) and Chern insulator phases with (C=\\pm4), separated by a metallic state region. By deriving the low-energy effective Hamiltonian near the (\\Gamma) point, the authors reveal that the topological phase boundaries correspond to two degenerate double Weyl semimetals, naturally explaining the origin of the Chern number jump (\\Delta C=4). Furthermore, in the absence of (p)-(d) exchange coupling, nodal-line-like states appear near the Fermi level, further separating the (C=\\pm4) phases. By tuning the tilt angle of magnetic moments via an external magnetic field, one can drive an insulator-metal transition in the Chern insulator phases, while the trivial insulator is largely unaffected; when uniform magnetization exchange coupling becomes significant, additional Chern insulator phases with (C=\\pm2) can be stabilized. These results confirm that GdGaI and its isostructural compounds serve as highly tunable platforms of clean magnetic semiconductors suitable for studying topological phases and field-induced metal-insulator transitions.\n19. Ab initio evidence for spin-polarized and soft-mode instabilities in D-type carbon schwarzite C136 Relevance Score: 3.3581 Authors: Eugene Yashin Link: http://arxiv.org/abs/2605.02082v1 Summary: This paper presents first-principles calculations on D-type carbon schwarzite C₁₃₆ (136-atom unit cell) using density functional theory (PBE functional, PAW pseudopotentials) and a plane-wave basis set. Non-spin-polarized calculations reveal a metallic electronic structure with significant flat-band features and high density of states near the Fermi level. Spin-polarized calculations converge to a magnetic order solution with a total magnetic moment of approximately 11.01 μB/cell and an absolute magnetic moment of about 12.15 μB/cell. The spin-polarized state is energetically lower than the non-spin-polarized state by roughly 0.03687 Ry (approximately 0.50 eV/cell). Phonon calculations using the finite displacement method with 78 symmetry-reduced displacement configurations, performed with Phonopy and Quantum ESPRESSO, reveal pronounced imaginary frequency modes in the ideal structure, with the softest mode occurring near q = [0.5, 0.5, 0.5] at a frequency of approximately -11.90 THz. These results indicate that ideal C₁₃₆ is not a simple harmonically stable metallic phase but rather a flat-band carbon network near the instability of spin and lattice symmetry breaking. Possible physical interpretations include Stoner-type flat-band magnetism and Peierls- or charge-density-wave-type structural reconstructions. This work does not claim that a superconducting state has been confirmed; instead, it identifies C₁₃₆ and related D-type schwarzites as candidate platforms for competing ground states, where magnetism, soft-mode reconstruction, and potentially doped or structurally stabilized superconducting phases compete.\n20. Metastable MnBi$_2$Te$_4$ enabled by magnetic-field-assisted synthesis Relevance Score: 3.3448 Authors: Abhinna Rajbanshi, G. M. Zills, Alexander M. Donald, Daniel Duong, David Graf, James J. Hamlin, Mark W. Meisel, I. Vekhter, Williams A. Shelton, Rongying Jin Affiliations: University of Florida, University of South Carolina, Louisiana State University, National High Magnetic Field Laboratory Link: http://arxiv.org/abs/2605.02119v1 Summary: This study successfully prepared metastable MnBi₂Te₄ single crystals via a magnetic field-assisted synthesis method (crystal growth in a 9 T magnetic field). X-ray diffraction confirmed that the crystal structure is identical to that of the zero-field-grown samples (space group R-3m), albeit with slightly altered lattice parameters. Measurements of magnetic susceptibility, magnetic torque, electrical resistivity, and specific heat reveal that the magnetic-field-grown MnBi₂Te₄ exhibits a ferromagnetic (FM) ground state with a Curie temperature of approximately 12.5 K, distinctly different from the A-type antiferromagnetic (AFM) ground state of the zero-field-grown samples. Low-temperature magnetization displays clear hysteresis loops and anisotropy (easy magnetization axis along the c-axis), with a coercive field of about 0.08 T. Curie–Weiss fitting of the high-temperature susceptibility yields a positive Curie temperature (~11.6 K) and an effective magnetic moment of about 2.2 μ_B, indicating that the Mn ions are in a low-spin state (S = 1/2), in contrast to the high-spin state (S = 5/2) of Mn in the zero-field-grown samples. First-principles calculations support the experimental results, revealing that magnetic field-assisted synthesis can effectively reconstruct the spin order and alter electronic properties, such as the de Haas–van Alphen oscillations observed in magnetic torque. This finding demonstrates that metastable FM phases can be stabilized via magnetic field-assisted synthesis, offering a new route to manipulate the quantum states of magnetic topological insulators.\n","permalink":"https://nickelates.uk/en/posts/2026-05-05-arxiv-daily/","summary":"\u003cblockquote\u003e\n\u003cp\u003e\u003cstrong\u003eDaily Overview\u003c/strong\u003e:\nHere is the English translation of the provided Chinese daily paper overview: \u0026gt; \u0026mdash; \u0026gt; \u003cstrong\u003eToday\u0026rsquo;s Research Overview in the Nickelate Superconductor Field\u003c/strong\u003e \u0026gt; Two research works today deepen our understanding of the superconducting mechanism in layered nickel oxides from the perspectives of structural and electronic phase transitions, as well as the relationship between electronic ordered phases and superconductivity. \u0026gt; First, a team from Université Paris-Saclay and other institutions systematically mapped the temperature-pressure phase diagram of the bilayer nickelate \u003cstrong\u003eLa₃Ni₂O₇\u003c/strong\u003e using high-pressure high-temperature Raman and infrared spectroscopy. They discovered that a pressure-induced lattice tilt-to-untilt structural phase transition is accompanied by a nearly two-order-of-magnitude increase in carrier concentration, and superconductivity is observed near the phase boundary. This work establishes a \u003cstrong\u003edirect link between structural and electronic property changes\u003c/strong\u003e, providing a key experimental foundation for understanding its high-pressure superconducting mechanism. \u0026gt; Meanwhile, another study led by Brookhaven National Laboratory and other institutions focuses on bilayer nickelate \u003cstrong\u003eLa₂PrNi₂O₇\u003c/strong\u003e thin films. Using resonant X-ray scattering and spectroscopy, they provide strong evidence that the spin density wave (\u003cstrong\u003eSDW\u003c/strong\u003e) is not a precursor state of superconductivity but rather a competing phase associated with \u003cstrong\u003eoxygen vacancies\u003c/strong\u003e. The work further proposes that in the superconducting phase, regions with intact oxygen stoichiometry have a ground state characterized by robust interlayer five-spin polaron states, which lock out-of-plane orbitals and render the in-plane orbital behavior close to the classical electronic configuration of cuprates and infinite-layer nickelates. \u0026gt; In summary, these studies not only elucidate the structural origin of pressure-driven superconductivity but also reveal the key regulatory role of oxygen stoichiometry in electronic states and the superconducting/competing phase balance, offering new perspectives for exploring the microscopic mechanism of nickelate superconductivity.\u003c/p\u003e","title":"arXiv Daily: Nickelate superconductors 2026-05-05"},{"content":" Daily Overview: Based on the list of papers you provided, no research papers directly focusing on nickel-based superconductivity as the core topic were found in today\u0026rsquo;s overview. Therefore, in accordance with your requirements, a related overall introduction cannot be generated this time.\n1. Dimensionality-Driven Electronic and Orbital Transitions Mediating Interfacial Magnetism in LaNiO3/CaMnO3 Observed In Situ Relevance Score: 4.9295 Authors: B-A. Courchene, A. Hampel, S. Beck, J. R. Paudel, J. D. Grassi, L. A. Lapinski, A. M. Derrico, M. Terilli, M. Kareev, C. Klewe, A. Gloskovskii, C. Schlueter, S. K. Chaluvadi, F. Mazzola, I. Vobornik, P. Orgiani, J. Chakhalian, A. J. Millis, A. X. Gray Affiliations: University of California, Berkeley, Lawrence Berkeley National Laboratory, DESY, Temple University, AREA Science Park, Rutgers University, CNR-IOM, Cornell University, Università degli Studi di Padova, Columbia University, Flatiron Institute Link: http://arxiv.org/abs/2604.28054v1 Summary: This study systematically investigates the modulation of interfacial magnetism by dimension-driven electronic and orbital transitions in LaNiO₃/CaMnO₃ superlattices through a combination of in-situ synthesis, polarization-dependent angle-resolved photoelectron spectroscopy, X-ray magnetic circular dichroism, and first-principles electronic structure calculations. It is found that reducing the LaNiO₃ thickness to the ultrathin limit triggers a metal-insulator transition, accompanied by the disappearance of electronic coherence and a crossing of orbital polarization (enhanced in-plane d_x²-y² orbital occupancy). These changes weaken charge transfer at the interface and suppress the interfacial magnetic moment of Mn in CaMnO₃, indicating that the interfacial ferromagnetic state is directly governed by the electronic confinement of LaNiO₃. Density functional theory combined with dynamical mean-field theory successfully reproduces the insulating state and orbital reconstruction. This work confirms a direct and tunable coupling among electronic, orbital, and magnetic degrees of freedom in oxide heterostructures, providing a new pathway for designing correlated electron behavior in nanoscale spintronic materials.\n2. Local probing of superconductivity at oxide interfaces with atomic force microscopy Relevance Score: 4.8366 Authors: Dilek Yildiz, Sungmin Kim, Dengyu Yang, Muqing Yu, Kyoungjun Lee, Ruiqi Sun, En-Min Shih, Steven R. Blankenship, Patrick Irvin, Franz J. Giessibl, Chang-Beom Eom, Jeremy Levy, Joseph A. Stroscio Affiliations: National Institute of Standards and Technology, University of Wisconsin–Madison, University of Regensburg, University of Pittsburgh, University of Maryland, The University of Tokyo Link: http://arxiv.org/abs/2604.28077v1 Summary: Here we report local probing of superconductivity in patterned nanoscale devices at the LaAlO₃/SrTiO₃ (LAO/STO) heterointerface, using ultralow-temperature noncontact atomic force microscopy (AFM), dissipation spectroscopy, and Kelvin probe force microscopy (KPFM) at millikelvin temperatures. Devices comprising two-dimensional electron gas, nanowires, and waveguide channels were fabricated by conductive AFM lithography or ultralow-voltage electron-beam lithography. Topography and contact potential difference (CPD) maps were obtained using frequency-modulation noncontact AFM. KPFM measurements reveal a CPD difference of about 1.5 V between the patterned and unpatterned regions. Combined with an electrostatic model, this yields a carrier density variation of approximately 1×10¹⁴ cm⁻², which lies in the intermediate density range corresponding to the superconducting dome. The key finding comes from spatially resolved energy dissipation measurements: within the patterned superconducting channels, the dissipation signal is significantly suppressed, and the dissipation spectra exhibit a characteristic nonlinear bias dependence, consistent with the suppression of ohmic losses by superconductivity. Spatial mapping shows that the superconducting features are confined to edge channels in certain devices, with a width of about 200 nm. This provides direct microscopic evidence for the width-independent critical current and anomalous pairing observed in previous transport measurements. This study establishes atomic force microscopy as a local probe of superconductivity in patterned oxide interfaces, and paves the way toward understanding the long-standing issues of quantum confinement and transport anomalies in related oxide nanostructures.\n3. Room-temperature shape-memory effect in Sr(Ni$_{1-x}$Cu$_x$)$_2$P$_2$ Relevance Score: 4.6059 Authors: Juan Schmidt, Alexander J. Horvarth, Seok-Woo Lee, Sergey L. Bud\u0026rsquo;ko, Paul C. Canfield Affiliations: CONICET, Iowa State University, University of Connecticut Link: http://arxiv.org/abs/2604.24019v2 Summary: This paper investigates the room-temperature shape memory effect in Sr(Ni₁₋ₓCuₓ)₂P₂ single crystals. The compound can exhibit three crystal structures between the Sr layers: an uncollapsed tetragonal phase (ucT) with no P–P bonding, an orthorhombic phase (tcO) with one-third P–P bonding, and a collapsed tetragonal phase (cT) with complete P–P bonding. Reversible transitions among these three states can be achieved through Cu substitution and temperature control. Temperature-dependent resistivity measurements and single-crystal X-ray diffraction experiments reveal that Cu substitution promotes P–P bonding and stabilizes the cT phase. The constructed T-ₓ phase diagram shows that all structural transition temperatures increase with Cu content. Notably, the transition from tcO to cT exhibits significant thermal hysteresis, and its temperature can be tuned close to room temperature by adjusting the Cu content. In particular, at ₓ = 0.037, the material displays a shape memory effect near room temperature. Micropillar compression tests demonstrate large recoverable strain and excellent fatigue performance, making it suitable for use as a room-temperature shape memory material.\n4. Enhancement of superconducting stiffness in hybrid superconducting-metallic bilayers Relevance Score: 4.5920 Authors: J. E. Ebot, Lorenzo Pizzino, Sam Mardazad, Johannes S. Hofmann, Thierry Giamarchi, Adrian Kantian Link: http://arxiv.org/abs/2604.28187v1 Summary: This paper investigates the enhancement mechanism of superconducting rigidity in a hybrid bilayer system composed of superconducting and metallic layers. Using a one-dimensional Anderson lattice or Kondo lattice model under conditions away from half-filling (i.e., doped), numerical simulations are performed via the density matrix renormalization group (DMRG) and auxiliary-field quantum Monte Carlo (AFQMC) methods. It is found that doping breaks the coexistence between superconducting and density-density correlations present at half-filling, leading to a clear dominance of superconducting correlations. The key conclusion is that in the doped regime, the superconducting quasi-long-range order is not suppressed by a small charge gap in the thermodynamic limit, unlike the half-filled case. The metallic layer, through the proximity effect, induces a spin gap in itself, turning its single-electron propagator from algebraic decay to exponential decay. Despite this, the metal still mediates extended pairing-pairing couplings, thereby effectively enhancing the superconducting rigidity. The study reveals a complex dependence of superconducting enhancement on metallic parameters. In particular, under weak coupling conditions, two distinct enhancement mechanisms emerge: a pairing-limited regime and a stiffness-limited regime. Through particle-hole transformation, the results can be mapped to heavy-fermion Kondo lattice materials in a magnetic field, predicting that the magnetic field drives the system from a regime dominated by antiferromagnetic correlations to one dominated by easy-plane magnetic correlations, providing a feasible route for indirect verification of the Kivelson bilayer proposal.\n5. Pressure-induced reentrant superconductivity in a misfit layered compound $\\mathrm{(SnS)_{1.15}(TaS_2)}$ Relevance Score: 4.4099 Authors: Chutong Zhang, Jiajia Feng, Xiao Tang, Xiangzhuo Xing, Na Zuo, Xiaolei Yi, Yan Meng, Xiaoran Zhang, Rajesh Kumar Ulaganathan, Raman Sankar, Xiaofeng Xu, Xin Chen, Xiaobing Liu Affiliations: Indian Institute of Technology Roorkee, Center for High Pressure Science and Technology Advanced Research, Academia Sinica, Xinyang Normal University, Zhejiang University of Technology, Qufu Normal University, Jining University Link: http://arxiv.org/abs/2602.22999v1 Summary: This study systematically measured the superconductivity, electrical transport, and structural properties of the misfit layered compound (SnS)₁.₁₅(TaS₂) up to approximately 150 GPa using diamond anvil cell technology. It was experimentally found that the low-pressure superconducting phase was gradually suppressed and disappeared near 14.7 GPa, accompanied by an increase in residual resistance. However, above about 80 GPa, a new superconducting phase re-emerged and persisted up to the highest pressure, exhibiting a zero-resistance state. High-pressure X-ray diffraction indicated that no structural phase transition occurred throughout the entire pressure range, apart from lattice compression. Further electrical transport analysis revealed that the reappearance of superconductivity occurred after the Hall coefficient underwent a sign reversal (from hole-type dominant to electron-type dominant) at around 60 GPa, and the normal-state resistance exhibited non-monotonic evolution, suggesting pressure-induced electronic reconstruction. This work demonstrates that pressure-driven electronic reconstruction in misfit layered compounds can induce the reappearance of superconductivity, providing an effective means to tune superconductivity and electronic states through pressure in natural van der Waals heterostructures.\n6. Fractionalized Fermi liquids and the cuprate phase diagram Relevance Score: 4.3187 Authors: Pietro M. Bonetti, Maine Christos, Alexander Nikolaenko, Aavishkar A. Patel, Subir Sachdev Link: http://arxiv.org/abs/2508.20164v7 Summary: This paper reviews the theoretical framework for cuprate superconductors, centering on the description of the low-doping intermediate-temperature pseudogap phase based on the fractionalized Fermi liquid (FL*). The FL* theory predicts that the hole pocket area is p/8 (p being the hole doping), which differs from the p/4 predicted by spin density wave theory. Magnetic transport measurements (e.g., Yamaji angles) observe hole pocket quasiparticles capable of coherent interlayer tunneling in a square lattice, consistent with the FL* description. Methodologically, the Ancilla Layer Model (ALM) is employed, introducing a pair of auxiliary qubits at each lattice site to construct a three-layer model, and SU(2) gauge theory is used to describe the background spin liquid and its critical Dirac spinon fluctuations. Monte Carlo simulations indicate that thermal SU(2) gauge effects transform hole pockets into Fermi arcs observed in angle-resolved photoemission spectroscopy. Upon cooling, the FL* undergoes a confinement transition via one pathway, forming a d-wave superconductor through the Kosterlitz-Thouless-type condensation of h/(2e) vortices, whose nodal Bogoliubov quasiparticles exhibit anisotropic velocities and around which charge-order halos exist. Another confinement pathway yields a charge-ordered metallic state with quantum oscillations. As doping increases beyond the FL* phase, the system transitions through a strange metal region into a conventional Fermi liquid (FL) at high doping. The authors explain the non-Fermi liquid behavior observed at low temperatures across optimal and overdoped regimes using the Griffiths effect near a quantum critical point in a disordered metal. This approach generalizes the Sachdev-Ye-Kitaev model to two dimensions, developing a critical quantum \u0026ldquo;charge\u0026rdquo; liquid theory of mobile electrons in a disordered background to describe the FL*-FL metal-metal transition (without requiring symmetry-breaking order parameters). The overall framework simultaneously accounts for the pseudogap features in photoemission spectroscopy and the hole pocket behavior in magnetic transport, as well as the intertwined phase diagram involving superconductivity, charge order, and the strange metal state.\n7. Critical temperatures and critical currents of wide and narrow quasi-one-dimensional superconducting aluminum structures in zero magnetic field Relevance Score: 4.2648 Authors: V. I. Kuznetsov, O. V. Trofimov Link: http://arxiv.org/abs/2604.27822v1 Summary: This paper experimentally measures the critical temperature and switching/reset currents of wide and narrow quasi-one-dimensional superconducting aluminum structures of the same thickness under zero magnetic field. It is found for the first time that narrower structures exhibit lower critical temperatures and critical current densities, which may arise from a stronger effect of depairing centers on the dirty longitudinal boundaries of the narrow structures. Additionally, it is first observed that the temperature-dependent switching critical currents of both structures can be approximated by two functions in most cases: below the bottom temperature of the resistive normal-to-superconducting transition, the switching critical current follows the Kupriyanov-Lukichev theory; near the top temperature of the transition, the switching current exhibits a linear dependence on temperature and is consistent with the critical Josephson current, indicating the formation of Josephson SNS junctions in the structures. The aluminum structures, with widths of approximately 1.5 μm (wide) and 0.7 μm (narrow) and a thickness of about 50 nm, were experimentally fabricated. Using different measurement circuits, the critical temperature of the wide part was measured to be about 1.487 K, while that of the narrow part was about 1.458 K, with a difference exceeding 30 mK. The critical temperature was found to depend on the measurement circuit, indicating that the wide and narrow parts have different critical temperatures. By measuring voltage-current curves, the switching and reset currents as functions of temperature were obtained. Fitting the switching current with the Kupriyanov-Lukichev theory yielded adjustable critical currents and critical temperatures close to the theoretical values. These results support the model in which the difference in critical temperatures between the wide and narrow half-rings in a circular asymmetric aluminum ring leads to a phase shift in the critical current, providing key evidence for explaining related nonlocal effects.\n8. Unusual critical currents in quasi-one-dimensional superconducting aluminum two-width structures in a magnetic field Relevance Score: 4.2055 Authors: V. I. Kuznetsov, O. V. Trofimov Link: http://arxiv.org/abs/2604.27881v1 Summary: This paper investigates the anomalous critical switching current behavior of quasi-one-dimensional superconducting aluminum thin film structures composed of strips with different widths (narrow and wide) in a magnetic field. The temperature dependence of the critical switching current at zero field and the variation of the critical switching current with a perpendicular magnetic field at a given temperature near the critical temperature were experimentally measured. The main findings include: the critical switching current exhibits nonlocality, meaning its magnitude depends on the electron transport properties of the connecting region between the narrow and wide strips; in different measurement circuits, the experimentally measured switching current significantly deviates from calculations based on the Ginzburg-Landau theory; a nonzero switching current persists at high magnetic fields (even exceeding the maximum critical field of a single quasi-one-dimensional superconducting wire), a phenomenon that cannot be explained by existing theories. The paper also fits the experimental data using the Ginzburg-Landau theory and the Kupriyanov-Lukichev theory, revealing deviations of the fitting parameters from theoretical values. The study suggests that these anomalous phenomena originate from the different critical temperatures of the narrow and wide strips, causing the structure to behave as a Josephson SNS junction within a specific temperature range, where the critical current varies linearly with temperature and coincides with the hysteresis current. These results challenge traditional theories and provide new insights into electron transport in complex superconducting structures.\n9. Magnetic Quantum Criticality inside the Superconducting State Revealed by Penetration Depth Scaling with Local $T_{\\mathrm c}$ Relevance Score: 4.1204 Authors: Yusuke Iguchi, Kaede Inoh, Ryosuke Koizumi, Makoto Yokoyama Link: http://arxiv.org/abs/2604.27507v1 Summary: This study employs scanning superconducting quantum interference device (SQUID) microscopy to simultaneously measure the local magnetic penetration depth and superconducting transition temperature ((T_{\\mathrm c})) in Zn-doped CeCoIn₅ single crystals. To avoid ambiguities arising from doping inhomogeneity, the researchers used the local (T_{\\mathrm c}) as the tuning parameter instead of the nominal Zn doping concentration, thereby extracting critical exponents with higher precision. The experiment reveals a pronounced peak-like enhancement of the zero-temperature magnetic penetration depth (\\lambda(0)) near the antiferromagnetic quantum critical point, indicating the existence of a magnetic quantum critical point within the superconducting state. Scaling analysis shows that the extracted critical exponents exceed the Gaussian values predicted by the clean spin-density wave (SDW) theory, suggesting that the system lies in a disordered-modified quantum critical regime (i.e., a conventional critical point where the Harris criterion applies). The enhancement of (\\lambda(0)) reflects a suppression of the superfluid stiffness, consistent with critical scaling behavior. Furthermore, the local magnetic susceptibility exponent increases significantly with Zn doping, indicating that disorder enhances magnetic correlations. By using a local probe, this work effectively eliminates the broadening caused by macroscopic averaging, revealing intrinsic quantum critical behavior hidden by spatial inhomogeneity in conventional heavy-fermion superconductors, and provides a new approach for studying quantum criticality in unconventional superconductors.\n10. Superconductivity-Enabled Conversion of Ferromagnetic Resonance into Standing Spin Waves Relevance Score: 4.1029 Authors: Ya. V. Turkin, N. G. Pugach, F. M. Maksimov, A. S. Pakhomov, A. I. Chernov, V. I. Belotelov, S. N. Polulyakh, V. S. Stolyarov Link: http://arxiv.org/abs/2604.27076v1 Summary: This study, through a combination of experiment and theory, demonstrates that conventional diffusive superconductors (e.g., niobium) can convert uniform ferromagnetic resonance modes in adjacent ferromagnetic insulators (e.g., Bi-substituted yttrium iron garnet) into perpendicular standing spin waves. In the Bi-GdIG/Nb bilayer structure, an additional resonance peak appears in the microwave transmission spectrum below the superconducting transition temperature of niobium, located near the uniform ferromagnetic resonance peak, and emerges only when the superconducting state is present. The researchers constructed a microscopic theoretical model that self-consistently couples the superconducting condensate described by the quasiclassical Keldysh–Usadel equations with the Landau–Lifshitz–Gilbert dynamics, revealing two key mechanisms for mode conversion: (i) interfacial spin-transfer torque mediated by spin-polarized triplet Cooper pairs, which provides effective dynamic spin pinning; (ii) depth-dependent effective fields (electromagnetic proximity effect) generated by Abrikosov vortices near the superconductor/ferromagnet interface, which break the symmetry of the magnetic film thickness and enhance the overlap between the uniform drive and the standing wave eigenmodes. The calculated magnetic susceptibility successfully reproduces the experimental lineshape, indicating that superconductivity can serve as an active tuning knob to control exchange standing wave modes in magnetic insulators. This work provides a new pathway for low-dissipation information processing in superconducting spintronics and magnonics.\n11. Uniaxial strain-driven ferroelastic domain control in LaAlO3 Relevance Score: 4.0984 Authors: Matthias Roeper, Robin Buschbeck, Jakob Wetzel, Tobias Ritschel, Anna-Lena Hofmann, Vladyslav Kovtunovych, Mike N. Pionteck, Javier Taboada-Gutiérrez, Alexey B. Kuzmenko, Martina Basini, Vivek Unikandanunni, Iuliia Kiseleva, Jochen Geck, Susanne C. Kehr, Maximilian Lederer, Simone Sanna, Lukas M. Eng, Samuel D. Seddon Link: http://arxiv.org/abs/2604.28183v1 Summary: This paper achieves continuous and reversible manipulation of ferroelastic domain structures in single-crystal LaAlO₃ through in situ uniaxial strain. By integrating atomic force microscopy, X-ray diffraction, Raman spectroscopy, and first-principles calculations, we fully characterize the microstructural evolution of twin domain populations during the transition from the rhombohedral R3̄c ground state to the predicted orthorhombic Fmmm phase. Applying strain below 0.5% induces significant surface flattening and large-scale domain reorganization, demonstrating that uniaxial strain is a technically accessible control parameter for ferroelastic domain engineering. Experiments show that strain drives continuous domain wall rotation and redistribution of domain areas, ultimately transforming a four-domain state into a two-domain state, with the process being fully reversible. These findings open new pathways for active real-time programming of domain architectures in LaAlO₃-based heterostructures, holding significant implications for strain-tunable superconducting interfaces, nanoscale phonon-polariton optics, and ultrafast lattice control.\n12. Lectures on insulating and conducting quantum spin liquids Relevance Score: 4.0860 Authors: Subir Sachdev Affiliations: The Abdus Salam International Centre for Theoretical Physics, Harvard University, Flatiron Institute Link: http://arxiv.org/abs/2512.23962v6 Summary: This lecture reviews how the fractional quantum Fermi liquid (FL*) state addresses two key observational puzzles in cuprate high-temperature superconductors: (i) angle-dependent magnetoresistance (ADMR) measurements of the pseudogap metallic phase reveal small hole pockets that can coherently tunnel between square lattice planes; (ii) the nodal Bogoliubov quasiparticle velocity in the d-wave superconductor exhibits strong anisotropy (v_F \u0026raquo; v_Δ). The lecture first introduces two parton theories of insulating quantum spin liquids: the bosonic spinon theory and the fermionic spinon theory. Doping the bosonic spinon theory yields a \u0026ldquo;holon metal\u0026rdquo; state, applicable to ultracold atom experiments on the Lieb lattice, but unable to explain the coherent tunneling behavior in the cuprate pseudogap metal. Doping the fermionic spinon theory produces a d-wave superconductor with nearly isotropic quasiparticle velocities, inconsistent with observations. The core lies in the construction of the FL* state: by doping a quantum spin liquid with gauge-neutral electron-like quasiparticles, it simultaneously resolves both contradictions. The lecture elaborates on constructing the FL* state in the single-band Hubbard model using quantum dimer models, and then introduces the more realistic Ancilla layer model (ALM) to obtain theories of the pseudogap and d-wave superconductor. The ALM also provides a variational wavefunction for the FL* state of the Hubbard model, whose local correlations agree with ultracold atom observations.\n13. Polar Topologies in a Ferroelastic Metal Membrane Relevance Score: 3.8460 Authors: Rahil Haria, Noah Schnitzer, T. Ben Britton, Yaqi Li, Tom J. P. Irons, Sophia Linssen Pitsaros, Ella Banyas, Geri Topore, Annabel Hoyes, Mariana Palos, Sinead M. Griffin, Katherine Inzani, Michele Shelly Conroy Link: http://arxiv.org/abs/2604.28120v1 Summary: This study achieved free-standing membranes by exfoliating epitaxially grown SrRuO₃ thin films from the substrate. Using a correlative microscopy approach ranging from medium-electron-channeling contrast imaging (ECCI) to atomic-resolution scanning transmission electron microscopy (STEM), combined with Fourier-space strain analysis and first-principles calculations, we systematically characterized the ferroelastic domain structures within the membrane and the resulting polar topologies. It was found that upon releasing the substrate constraint, the thin film undergoes hierarchical ferroelastic domain refinement from micrometer to nanometer scales, spontaneously generating two types of polar textures. The first type selectively appears at translationally inequivalent antiphase boundaries (APBs): at these boundaries, the multi-component oxygen octahedral tilt field undergoes a Néel-like interpolation, preserving the in-phase tilt component and amplifying the rotation-flexoelectric coupling, thereby inducing an in-plane polarization displacement exceeding 13 pm; in contrast, translationally equivalent APBs exhibit Ising-type behavior with simultaneous collapse of all tilt components, remaining nonpolar. The second type of polar texture originates from embedded 90° ferroelastic walls. Through elastic accommodation of strain mismatch between variants and rotational-elongation effects, polar nanoclusters with a size of about 4 nm form at the walls. These results demonstrate that in free-standing metal oxide membranes, nanoscale ferroelastic domain structures can spontaneously generate polar topologies, providing a new platform for realizing reconfigurable spin-orbit coupling and multiferroic functionalities in conductive systems.\n14. Evidence for interior-gap pair-density-wave state in Kondo-Heisenberg chains Relevance Score: 3.8371 Authors: Yuto Hirose, Shunsuke C. Furuya, Yasuhiro Tada Link: http://arxiv.org/abs/2604.27440v1 Summary: This paper systematically investigates the superconducting phases of the one-dimensional Kondo-Heisenberg model in spin S=1/2 and S=3/2 chains by combining infinite density matrix renormalization group (iDMRG) and finite DMRG calculations. The results show that within the spin-gap regime, the bond-pairing correlation function decays as a power law, with the smallest exponent among all considered operators, confirming it as the dominant quasi-long-range order and exhibiting finite-wave-vector oscillations, thus establishing this state as a pair density wave (PDW) phase. Meanwhile, the momentum distribution function n(k) exhibits a reconstructed structure: it appears only as a hump in the S=1/2 chain but develops into a clear dip in the S=3/2 chain. This systematic variation strongly supports an interpretation of internal-gap single-particle reconstruction. Unlike conventional internal-gap superconductivity, which relies on preexisting Fermi surface mismatch, this system starts from a single bare conduction electron Fermi surface and dynamically generates additional low-energy single-particle structures through Kondo coupling, intertwined with the dominant PDW correlations. Direct iDMRG calculations in the thermodynamic limit reveal that PDW correlations dominate the bulk state, while charge density wave (CDW) correlations, though subdominant, preserve translational symmetry (i.e., they are not truly long-range ordered). Finite DMRG calculations show that boundary effects significantly modulate real-space correlations, highlighting the necessity of thermodynamic limit calculations for identifying intrinsic bulk momentum structures and dominant correlation channels. The study also indicates that the Yamanaka-Oshikawa-Affleck (YOA) momentum constraint manifests as large-wave-vector structures in the charge channel, but does not correspond to a conventional large Fermi surface. In summary, this paper provides clear evidence for an internal-gap PDW state arising from strong correlations in Kondo-Heisenberg chains.\n15. Flux-trapping characterization for superconducting electronics using a cryogenic widefield N-$V$ diamond microscope Relevance Score: 3.7160 Authors: Rohan T. Kapur, Pauli Kehayias, Sergey K. Tolpygo, Adam A. Libson, George Haldeman, Collin N. Muniz, Alex Wynn, Nathaniel J. O\u0026rsquo;Connor, Neel A. Parmar, Ryan Johnson, Andrew C. Maccabe, John Cummings, Justin L. Mallek, Danielle A. Braje, Jennifer M. Schloss Link: http://arxiv.org/abs/2506.01906v3 Summary: We have developed a low-temperature wide-field NV diamond magnetic microscope capable of rapid (typically 4 minutes/field of view) micron-scale imaging of magnetic flux vortices in superconducting devices. The system operates from 4 K to room temperature with background magnetic fields ranging from nT to mT levels, effectively isolating samples from laser and microwave interference through reflective coatings and integrated microwave interconnect boards. Using this instrument, we measured 200 nm thick Nb films and patterned strips (widths 4–80 μm). In unpatterned films, vortex density increases linearly with external magnetic field, and recurring strong pinning sites are identified. For patterned strips, we extracted two expulsion fields: the first expulsion field (onset of vortex entry) and the second expulsion field (vortex density linearly increases to match that of the film). A crossover in expulsion behavior is observed at strip widths of 10–20 μm: for wide strips (≥40 μm), the expulsion field is approximately inversely proportional to width (B_exp ~ 1/w), while for narrow strips (≤20 μm), the expulsion field approaches a constant value (B_exp ~ 4 μT). This scaling relationship qualitatively agrees with theoretical models (Likharev model), and the lower expulsion field in narrow strips indicates significant effects of film defects on vortex nucleation and pinning. This technique enables high-throughput characterization of flux trapping, providing direct experimental evidence for optimizing flux mitigation strategies in superconducting electronics, such as designing trenches and controlling cooling magnetic fields.\n16. Spin responses of a disordered helical superconducting edge under Zeeman field Relevance Score: 3.7075 Authors: Zeinab Bakhshipour, Mir Vahid Hosseini Affiliations: University of Zanjan Link: http://arxiv.org/abs/2511.04263v3 Summary: This paper systematically analyzes the influence of disorder on the spin transport of helical edges in two-dimensional topological insulators under the combined effects of a Zeeman field and superconducting proximity, using bosonization and renormalization group methods. In the study, the authors construct a partially spin-mixed helical superconductor model, treating the Zeeman field and superconducting pairing potential as sine-Gordon-type perturbations, and consider two scenarios: a single impurity and random disorder (multiple impurities). Renormalization group flow analysis indicates that in the attractive interaction regime, the Zeeman field enhances the superconducting gap; in the repulsive regime, the Zeeman field reduces the effective Luttinger parameter, keeping disorder relevant at lower energy scales, thereby extending the effective range of impurity scattering. Disorder itself logarithmically suppresses charge and spin density wave correlations, but simultaneously introduces logarithmic enhancement corrections to superconducting pairing correlations, helping to stabilize superconducting pairing. These competing mechanisms are directly reflected in the scaling behavior of spin conductance: in the single-impurity case, spin conductance exhibits a power-law decay with decreasing temperature; in the multiple-impurity disordered case, collective backscattering further suppresses spin conductance, even leading to localization in certain parameter regimes. Superconducting correlations partially offset this suppression in the attractive interaction regime, resulting in a rich phase diagram. The paper presents experimentally observable spin transport characteristics, providing a theoretical basis for understanding the interplay between disorder and superconductivity in topological edge channels.\n17. Chern number reversal and emergent superconductivity in rhombohedral graphene induced by in-plane magnetic fields Relevance Score: 3.6869 Authors: Xiaozhou Zan, Hangzhe Li, Jiawei Guo, Gengdong Zhou, Kangyao Chen, Cihan Gao, Zijun Xu, Kenji Watanabe, Takashi Taniguchi, Anqi Wang, Jie Shen, Jinsong Zhang, Zhida Song, Yayu Wang Affiliations: Peking University, Tsinghua University, National Institute for Materials Science, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Hefei National Laboratory Link: http://arxiv.org/abs/2604.27788v1 Summary: This study investigates topological and superconducting states in an hBN-aligned eight-layer rhombohedral graphene moiré superlattice. By utilizing dual-gate tuning of the displacement field and carrier density, combined with in-plane magnetic field transport measurements, two key phenomena are observed: (i) In the electron-doped region away from the moiré potential, the system exhibits a robust quantum anomalous Hall (QAH) state, whose Chern number can be cooperatively tuned by both the displacement field and in-plane magnetic field, enabling sign reversal. The response of this QAH state to an in-plane magnetic field is isotropic, indicating that the interplay between orbital magnetism and spin-orbit coupling is crucial. (ii) In the hole-doped region near the moiré superlattice, three unconventional superconducting phases (SC1, SC2, SC3) are identified, each exhibiting distinct responses to an in-plane magnetic field: SC1 is weakly enhanced, SC2 is strongly suppressed, and SC3 is entirely induced by the in-plane field. This field-induced superconducting state provides strong evidence for spin-triplet pairing. The superconducting transition temperatures of the three phases are approximately 120 mK, 100 mK, and 88 mK, respectively, and all are rapidly suppressed by a perpendicular magnetic field. This work reveals the rich physics of coexisting topological and superconducting orders in rhombohedral graphene moiré systems and demonstrates that the in-plane magnetic field serves as a powerful in-situ tuning tool, paving the way for the design of novel quantum devices.\n18. Programmable superconducting diode from nematic domain control in FeSe Relevance Score: 3.6820 Authors: R. D. H. Hinlopen, C. Putzke, L. Holeschovsky, R. Nicholls, F. Ronning, E. D. Bauer, N. E. Hussey, P. J. W. Moll Affiliations: HFML-FELIX, Max Planck Institute for Structure and Dynamics of Matter, University of Bristol, Los Alamos National Laboratory Link: http://arxiv.org/abs/2604.26631v2 Summary: This study demonstrates a programmable superconducting diode effect based on FeSe nematic superconductors. FeSe is a centrosymmetric material; however, through the interaction between its intrinsic nematic domain walls and vortices, a superconducting diode efficiency of up to approximately 75% is achieved. Using a low-temperature focused ion beam to fabricate high-quality micro-scale devices, the current–voltage characteristics were measured under a magnetic field. It was found that when the magnetic field direction is slightly tilted relative to the twin boundaries, vortex pinning at the domain walls leads to asymmetry in the critical current with respect to polarity. The key lies in applying microsecond-scale high-current pulses (with a quenching rate exceeding 10^7 K/s) to rapidly heat and quench the nematic order, thereby altering the domain wall configuration and enabling deterministic programming of the diode polarity and efficiency. For example, slow annealing yields a nearly symmetric state, thermal quenching produces a reverse diode, and cold quenching results in a forward diode. This repeatable pulse protocol achieves microsecond-scale writing of superconducting diode functionality while maintaining constant sample temperature and magnetic field. Mechanistically, the anisotropy of the coherence length on either side of the nematic domain wall gives rise to a difference in vortex line energy, resulting in asymmetric pinning. This method overcomes the conventional reliance on structural asymmetry for superconducting diodes, offering a new paradigm based on the programming of electronic state patterns for superconducting circuit components, and can be extended to other anisotropic type-II superconductors.\n19. On the proposed concept of mechanical phasons in Ni-Mn-Ga modulated martensite Relevance Score: 3.6154 Authors: Petr Sedlák, Tomáš Grabec, Hanuš Seiner Affiliations: Czech Academy of Sciences Link: http://arxiv.org/abs/2604.27729v1 Summary: This paper proposes the concept of a \u0026ldquo;mechanical phason\u0026rdquo; to explain the anomalous elastic behavior of five-layered modulated (10M) martensite in Ni-Mn-Ga shape memory alloys. It is found that 10M martensite exhibits extremely low macroscopic shear stiffness on specific planes perpendicular to the modulation vector, and this compliance disappears when the modulation becomes incommensurate. The authors construct a simplified mechanical model that couples the modulation phason (i.e., the dynamic phase shift of the modulation function) with the macroscopic lattice strain. The model integrates the adaptive martensite theory (nanotwin architecture) and a charge density wave perspective based on electronic structure, assuming the modulation wave is described by a sinusoidal function. By linking the phase shift to the monoclinic distortion angle, the phason is enabled to relax external shear loads. The results show that under commensurate and weakly incommensurate modulations, the mechanical phason can effectively relax shear stress, resulting in anomalously low macroscopic shear compliance (on the order of 0.1 GPa). However, under strongly incommensurate modulation, the phason relaxation mechanism fails, and the lattice shear stiffness recovers to values consistent with first-principles predictions (approximately 15–18 GPa). The model also naturally explains properties such as the spontaneous monoclinic distortion of the 10M lattice and the easy formation and propagation of a/b twin variants. Through this model, the paper reconciles the contradiction between laser-ultrasonic experiments (observing extremely soft elasticity) and inelastic neutron scattering along with first-principles calculations (predicting normal stiffness), indicating that the macroscopic elastic softening originates from phason degrees of freedom rather than an intrinsic lattice soft mode. This study provides a new perspective for understanding mechanical instabilities and twin supermobility in modulated martensites.\n20. From Narrow-gap Semiconductor to Metallic Altermagnet: Optical Fingerprints of Co-Doped FeSb$_2$ Relevance Score: 3.5645 Authors: R. Mathew Roy, M. Povolotskiy, J. Kirschke, C. Prange, Y. Xia, V. Sundaramurthy, P. Puphal, M. Pinteric, M. van de Loo, A. Kreyssig, T. Zhang, A. E. Böhmer, M. Dressel, M. Wenzel Affiliations: Universität Stuttgart, Max Planck Institute for Solid State Research, Chinese Academy of Sciences, Ruhr University Bochum, University of Maribor Link: http://arxiv.org/abs/2604.28105v1 Summary: Through infrared spectroscopy, transport, and magnetic measurements of cobalt-doped FeSb₂, combined with density functional theory calculations, it is found that approximately 15% cobalt substitution can transform the narrow-band-gap semiconductor FeSb₂ into a room-temperature stable metallic d-wave altermagnet. The infrared optical conductivity reveals low-energy interband transitions around 0.1 eV after doping, with intensity increasing as cobalt concentration rises. First-principles calculations indicate that these transitions originate entirely from non-relativistic band splitting (approximately 0.2 meV) induced by the altermagnetic spin order, as well as band splitting (approximately 5 meV) caused by spin-orbit coupling near the Fermi level. Additionally, cobalt substitution introduces Fano line shapes and mode mixing of infrared-active phonons, reflecting enhanced electron-phonon coupling and local inversion symmetry breaking, while the altermagnetic spin symmetry remains intact. This work establishes carrier-tuned FeSb₂ as a platform for exploring metallic d-wave altermagnetism and its coupling with lattice degrees of freedom, providing clear optical fingerprints for realizing bulk metallic altermagnetism in correlated materials.\n","permalink":"https://nickelates.uk/en/posts/2026-05-01-arxiv-daily/","summary":"\u003cblockquote\u003e\n\u003cp\u003e\u003cstrong\u003eDaily Overview\u003c/strong\u003e:\nBased on the list of papers you provided, no research papers directly focusing on nickel-based superconductivity as the core topic were found in today\u0026rsquo;s overview. Therefore, in accordance with your requirements, a related overall introduction cannot be generated this time.\u003c/p\u003e\u003c/blockquote\u003e\n\u003ch2 id=\"1-dimensionality-driven-electronic-and-orbital-transitions-mediating-interfacial-magnetism-in-lanio3camno3-observed-in-situ\"\u003e1. Dimensionality-Driven Electronic and Orbital Transitions Mediating Interfacial Magnetism in LaNiO3/CaMnO3 Observed In Situ\u003c/h2\u003e\n\u003cul\u003e\n\u003cli\u003e\u003cstrong\u003eRelevance Score\u003c/strong\u003e: \u003ccode\u003e4.9295\u003c/code\u003e\u003c/li\u003e\n\u003cli\u003e\u003cstrong\u003eAuthors\u003c/strong\u003e: B-A. Courchene, A. Hampel, S. Beck, J. R. Paudel, J. D. Grassi, L. A. Lapinski, A. M. Derrico, M. Terilli, M. Kareev, C. Klewe, A. Gloskovskii, C. Schlueter, S. K. Chaluvadi, F. Mazzola, I. Vobornik, P. Orgiani, J. Chakhalian, A. J. Millis, A. X. Gray\u003c/li\u003e\n\u003cli\u003e\u003cstrong\u003eAffiliations\u003c/strong\u003e: University of California, Berkeley, Lawrence Berkeley National Laboratory, DESY, Temple University, AREA Science Park, Rutgers University, CNR-IOM, Cornell University, Università degli Studi di Padova, Columbia University, Flatiron Institute\u003c/li\u003e\n\u003cli\u003e\u003cstrong\u003eLink\u003c/strong\u003e: \u003ca href=\"http://arxiv.org/abs/2604.28054v1\"\u003ehttp://arxiv.org/abs/2604.28054v1\u003c/a\u003e\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003e\u003cstrong\u003eSummary\u003c/strong\u003e: This study systematically investigates the modulation of interfacial magnetism by dimension-driven electronic and orbital transitions in LaNiO₃/CaMnO₃ superlattices through a combination of in-situ synthesis, polarization-dependent angle-resolved photoelectron spectroscopy, X-ray magnetic circular dichroism, and first-principles electronic structure calculations. It is found that reducing the LaNiO₃ thickness to the ultrathin limit triggers a metal-insulator transition, accompanied by the disappearance of electronic coherence and a crossing of orbital polarization (enhanced in-plane d_x²-y² orbital occupancy). These changes weaken charge transfer at the interface and suppress the interfacial magnetic moment of Mn in CaMnO₃, indicating that the interfacial ferromagnetic state is directly governed by the electronic confinement of LaNiO₃. Density functional theory combined with dynamical mean-field theory successfully reproduces the insulating state and orbital reconstruction. This work confirms a direct and tunable coupling among electronic, orbital, and magnetic degrees of freedom in oxide heterostructures, providing a new pathway for designing correlated electron behavior in nanoscale spintronic materials.\u003c/p\u003e","title":"arXiv Daily: Nickelate superconductors 2026-05-01"},{"content":" Daily Overview: This post sorts papers by relevance to nickelate superconductors. Summaries are AI-generated and may contain errors.\n1. Dimensionality-Driven Electronic and Orbital Transitions Mediating Interfacial Magnetism in LaNiO3/CaMnO3 Observed In Situ Relevance Score: 4.9640 Authors: B-A. Courchene, A. Hampel, S. Beck, J. R. Paudel, J. D. Grassi, L. A. Lapinski, A. M. Derrico, M. Terilli, M. Kareev, C. Klewe, A. Gloskovskii, C. Schlueter, S. K. Chaluvadi, F. Mazzola, I. Vobornik, P. Orgiani, J. Chakhalian, A. J. Millis, A. X. Gray Link: http://arxiv.org/abs/2604.28054v1 Summary: Emergent magnetic states at oxide interfaces arise from the interplay of charge transfer, orbital reconstruction, and dimensional confinement, offering a route to engineered correlated-electron behavior in nanoscale spintronic materials. Here, we combine in situ synthesis, polarization-dependent angle-resolved photoelectron spectroscopy, X-ray magnetic circular dichroism, and first-principles electronic-structure calculations to investigate LaNiO3/CaMnO3 superlattices. We show that reducing the LaNiO3 thickness drives a metal-insulator transition accompanied by loss of electronic coherence and an orbital-polarization crossover in the ultrathin limit. These changes weaken charge transfer across the interface and suppress the interfacial Mn magnetic moment in CaMnO3, revealing that the emergent ferromagnetic state is directly governed by electronic confinement in LaNiO3. The insulating state and orbital reconstruction are reproduced by density functional theory combined with dynamical mean-field theory. Together, these results establish a direct and tunable coupling among electronic, orbital, and magnetic degrees of freedom in oxide heterostructures.\n2. Local probing of superconductivity at oxide interfaces with atomic force microscopy Relevance Score: 4.8074 Authors: Dilek Yildiz, Sungmin Kim, Dengyu Yang, Muqing Yu, Kyoungjun Lee, Ruiqi Sun, En-Min Shih, Steven R. Blankenship, Patrick Irvin, Franz J. Giessibl, Chang-Beom Eom, Jeremy Levy, Joseph A. Stroscio Link: http://arxiv.org/abs/2604.28077v1 Summary: Superconductivity in strontium titanate has remained enigmatic for more than 50 years. The LaAlO$_3$/SrTiO$_3$ (LAO/STO) heterointerface enables systematic dimensional confinement, from a two-dimensional electron gas to quasi-one-dimensional nanostructures, providing access to this quantum state. Transport measurements in patterned devices reveal puzzling phenomena, including width-independent critical currents and anomalous pairing suggestive of one-dimensional behavior, but direct local probes of the patterned interface and its superconducting response have been lacking. Here we use ultralow-temperature non-contact atomic force microscopy, dissipation spectroscopy, and Kelvin probe force microscopy to locally probe signatures of superconductivity in patterned LAO/STO devices. Spatially resolved energy-dissipation measurements reveal superconducting signatures, with features confined in some devices to edge channels approximately 200 nm wide. Dissipation spectra exhibit a characteristic nonlinear bias dependence that provides a local diagnostic of superconductivity, consistent with the intermediate carrier-density regime near the superconducting dome, and persisting up to the critical field. These results establish atomic force microscopy as a local probe of superconductivity in patterned LAO/STO structures and provide a route to addressing longstanding questions about quantum confinement and transport anomalies in correlated oxide nanostructures.\n3. Enhancement of superconducting stiffness in hybrid superconducting-metallic bilayers Relevance Score: 4.7141 Authors: J. E. Ebot, Lorenzo Pizzino, Sam Mardazad, Johannes S. Hofmann, Thierry Giamarchi, Adrian Kantian Link: http://arxiv.org/abs/2604.28187v1 Summary: Boosting superconductivity by metallic reservoirs is the essence of Kivelson\u0026rsquo;s bilayer proposal. One layer provides pairing to the electrons, while the weakly coupled metal provides additional phase coherence to those pairs by mediating extended-range pair-pair coupling. Demonstrating significant and unambiguous performance gains with strong-coupling methods for such set-ups had been difficult. In the present work, we study these systems doped away from half-filling, corresponding to a partially spin-polarized 1D Anderson- or Kondo-lattice. We show that this breaks the coexistence of dominant superconducting and density-density correlations decisively in favour or the former. Consequently, we provide evidence that in this doped regime, superconducting near-long-range order is not precluded by a small charge-gap in the thermodynamic limit, as we have recently shown to be the case at half-filling [JE Ebot $et$ $al.$, arXiv:2602.11153 [cond-mat.supr-con]]. We study the complex manner in which the enhancement of superconductivity in the pairing layer depends on the parameters of the metal, and especially that both pairing-limited and stiffness-limited regimes may appear in these systems. In addition to superconducting bilayers, our results are relevant, via a particle-hole transformation, for heavy-fermion Kondo-lattice materials in magnetic fields, as we provide previously lacking insight on the competition between antiferromagnetic and easy-plane magnetism, as well as a route for comprehensive indirect tests of Kivelson\u0026rsquo;s bilayer proposal well beyond previous capabilities.\n4. Critical temperatures and critical currents of wide and narrow quasi-one-dimensional superconducting aluminum structures in zero magnetic field Relevance Score: 4.2113 Authors: V. I. Kuznetsov, O. V. Trofimov Link: http://arxiv.org/abs/2604.27822v1 Summary: We measured the critical temperatures and critical switching and retrapping currents of wide and narrow thin-film quasi-one-dimensional superconducting aluminum structures of the same thickness in zero magnetic field. For the first time, we found that the narrower the structure, the lower the critical temperature and critical current density in the structure. Probably, the influence of depairing centers that are on dirty longitudinal boundaries of the structure, is the stronger than the narrower the structure. It is found for the first time that, in most cases, the temperature-dependent switching critical current in both structures is approximated by two functions. At temperatures below the temperature corresponding to the bottom of the resistive N-S transition of structures, the switching critical current is described by the Kupriyanov-Lukichev theory. At temperatures close to the top of the N-S transition, the switching current is linear with temperature and coincides with the critical Josephson current. At these temperatures, Josephson SNS junctions are formed in structures.\n5. Unusual critical currents in quasi-one-dimensional superconducting aluminum two-width structures in a magnetic field Relevance Score: 4.1539 Authors: V. I. Kuznetsov, O. V. Trofimov Link: http://arxiv.org/abs/2604.27881v1 Summary: We measured unusual critical currents as functions of temperature in the zero field and as functions of a magnetic field perpendicular to the substrate surface at a given temperature close to the critical temperature in thin-film long quasi-one-dimensional superconducting aluminum two-width structures consisting of narrow and wide wires with different critical temperatures. It is found that the experimental critical switching current as a function of the field at a given temperature, determined by the appearance of a dc voltage on a short section of the structure, is nonlocal (dependent on electron transport in the area containing the junction line between the narrow and wide wires). When current flows through the narrow and wide wires of the structure, the switching currents, experimental and calculated within the framework of the Ginzburg-Landau theory, differ radically from each other. A nonzero switching current exists in high fields greater than the maximum critical magnetic field in a quasi-one-dimensional superconducting wire. In the aluminum two-width structures studied here, the unusual measured switching current challenges description by known theories.\n6. Magnetic Quantum Criticality inside the Superconducting State Revealed by Penetration Depth Scaling with Local $T_{\\mathrm c}$ Relevance Score: 4.0969 Authors: Yusuke Iguchi, Kaede Inoh, Ryosuke Koizumi, Makoto Yokoyama Link: http://arxiv.org/abs/2604.27507v1 Summary: We demonstrate a magnetic quantum critical point embedded within the superconducting state of Zn-doped CeCoIn$_5$, revealed by a pronounced peak in the magnetic penetration depth at zero temperature $λ(0)$. Using scanning SQUID microscopy, we determine the local superconducting transition temperature $T_{\\mathrm c}$ and $λ(0)$. By parameterizing $λ(0)$ in terms of the local $T_{\\mathrm c}$ rather than nominal Zn substitution, we circumvent the ambiguity caused by doping inhomogeneity and enable a more precise extraction of the critical exponent. The extracted exponent exceeds the clean spin-density-wave value, indicating a disorder-modified quantum critical regime. The enhancement of $λ(0)$ reflects the suppression of the superfluid stiffness and is consistent with critical scaling. Our approach provides a route to uncover intrinsic quantum critical behavior hidden by inhomogeneity in unconventional superconductors.\n7. Uniaxial strain-driven ferroelastic domain control in LaAlO3 Relevance Score: 4.0938 Authors: Matthias Roeper, Robin Buschbeck, Jakob Wetzel, Tobias Ritschel, Anna-Lena Hofmann, Vladyslav Kovtunovych, Mike N. Pionteck, Javier Taboada-Gutiérrez, Alexey B. Kuzmenko, Martina Basini, Vivek Unikandanunni, Iuliia Kiseleva, Jochen Geck, Susanne C. Kehr, Maximilian Lederer, Simone Sanna, Lukas M. Eng, Samuel D. Seddon Link: http://arxiv.org/abs/2604.28183v1 Summary: Multiferroic domain walls in functional oxides exhibit properties distinct from the bulk and are increasingly exploited as active elements in nanoelectronic and photonic devices. Deterministic control of domain populations has typically remained limited to local control, or removal with temperature. Here we demonstrate continuous, reversible manipulation of the ferroelastic domain structure in single-crystal LaAlO$_3$ using in-situ uniaxial strain. Combining atomic force microscopy, X-ray diffraction, and Raman spectroscopy with first-principles calculations we map the complete microscopic evolution of the twin domain population through the strain-driven transition from the rhombohedral $R\\bar{3}c$ ground state toward the predicted orthorhombic $Fmmm$ phase. Applied strains below $0.5\\%$ produce pronounced surface flattening and large-scale domain reorganisation, establishing uniaxial strain as a technically accessible control parameter for ferroelastic domain engineering. These results open a route to active, real-time programming of domain architectures in LaAlO$_3$-based heterostructures, with implications for strain-tunable superconducting interfaces, nanoscale phonon-polariton optics, and ultrafast lattice control.\n8. Polar Topologies in a Ferroelastic Metal Membrane Relevance Score: 3.8892 Authors: Rahil Haria, Noah Schnitzer, T. Ben Britton, Yaqi Li, Tom J. P. Irons, Sophia Linssen Pitsaros, Ella Banyas, Geri Topore, Annabel Hoyes, Mariana Palos, Sinead M. Griffin, Katherine Inzani, Michele Shelly Conroy Link: http://arxiv.org/abs/2604.28120v1 Summary: Polar metals, materials in which electric polarisation and metallicity coexist, are exceptionally rare because itinerant electrons screen long-range dipoles and favour centrosymmetric structures. Engineering polar textures in a conducting magnet holds promise for reconfigurable spin orbit coupling and magnetoelectric functionality. Here we show that releasing epitaxial SrRuO3 films from their substrates drives a hierarchy of ferroelastic domain refinement from micrometre to nanometre length scales, and that this structural reorganisation spontaneously generates two distinct classes of emergent polar texture that are ubiquitous across the freestanding membrane. Using correlative microscopy from mesoscale electron channelling contrast imaging (ECCI) to atomic resolution scanning transmission electron microscopy (STEM), we demonstrate that electric polarisation emerges selectively at translation-inequivalent antiphase boundaries (APBs). At these boundaries multicomponent aac tilt field undergoes Neel-like interpolation that preserves the in-phase tilt component and amplifies roto flexoelectric coupling, while translation-equivalent boundaries remain nonpolar. The Neel like interpolation at hard APBs and Ising like collapse of all tilt components at easy APBs is corroborated with ab initio calculations. While embedded 90 ferroelastic walls provide an additional mechanistically distinct source of electric polarisation resulting in polar nanoclusters (4 nm). These distinct nanotextures at 90 walls from via elastic accommodation of strain mismatch between variants and rotostriction as the tilt field interpolates across the boundaries. These findings show that, in a membrane form, metal oxides provide a robust platform for hosting nanoscale ferroelastic domains that generate polar textures.\n9. Evidence for interior-gap pair-density-wave state in Kondo-Heisenberg chains Relevance Score: 3.8189 Authors: Yuto Hirose, Shunsuke C. Furuya, Yasuhiro Tada Link: http://arxiv.org/abs/2604.27440v1 Summary: Interior-gap superconductivity has long been discussed as an exotic paired state in the presence of Fermi-surface mismatch, but its realization in canonical strongly correlated models has remained elusive. Here we present evidence that the superconducting phase of one-dimensional Kondo-Heisenberg models realizes an interior-gap pair-density-wave (PDW) state generated by strong correlations. Combining infinite density-matrix-renormalization-group (iDMRG) and finite DMRG calculations for $S=1/2$ and $S=3/2$ chains, we show that the PDW correlation is the dominant bulk superconducting correlation in the spin-gapped regime and that the momentum distribution function $n(k)$ exhibits a reconstructed structure characteristic of interior-gap physics. In particular, while the feature in $n(k)$ for the $S=1/2$ chain is only hump-like, the corresponding structure in the $S=3/2$ chain develops into a clear dip, strongly supporting the interpretation in terms of an interior-gap-like dip structure. Unlike conventional interior-gap scenarios based on a mismatch between preexisting Fermi surfaces, the present system starts from a single bare conduction-electron Fermi surface, and the additional low-energy single-particle structure emerges dynamically together with the dominant PDW correlation through the Kondo coupling. Finite DMRG data further demonstrate that boundary effects can substantially modify real-space correlations in this gapless one-dimensional system, making a direct thermodynamic-limit calculation essential for identifying the intrinsic bulk momentum structure and the dominant correlation channel.\n10. Chern number reversal and emergent superconductivity in rhombohedral graphene induced by in-plane magnetic fields Relevance Score: 3.6879 Authors: Xiaozhou Zan, Hangzhe Li, Jiawei Guo, Gengdong Zhou, Kangyao Chen, Cihan Gao, Zijun Xu, Kenji Watanabe, Takashi Taniguchi, Anqi Wang, Jie Shen, Jinsong Zhang, Zhida Song, Yayu Wang Link: http://arxiv.org/abs/2604.27788v1 Summary: Rhombohedral graphene with topological flat bands offers an ideal platform for realizing correlated and topological quantum phases. Here we investigate hBN aligned eight-layer rhombohedral graphene moire superlattices, which host a robust quantum anomalous Hall (QAH) state alongside three unconventional superconducting phases. For electron-doped carriers away from the moire potential, we observe QAH Chern number reversal driven by the displacement fields and in plane magnetic fields. For hole-doped carriers near the moire superlattice, the three superconducting phases exhibit distinctively different in plane magnetic field responses: one is weakly enhanced, the second is strongly suppressed, and the third exclusively induced by in plane magnetic field. The isotropic in plane magnetic field response in the QAH regime points to interplay between orbital magnetism and spin-orbit coupling, and the field-emergent superconductivity provides compelling evidence for spin-triplet pairing. Our work demonstrates a highly versatile platform for coexisting topological and superconducting states, and highlights in plane magnetic field as a powerful in-situ control knob for engineering novel quantum devices.\n11. On the proposed concept of mechanical phasons in Ni-Mn-Ga modulated martensite Relevance Score: 3.6321 Authors: Petr Sedlák, Tomáš Grabec, Hanuš Seiner Link: http://arxiv.org/abs/2604.27729v1 Summary: We discuss modulation phasons as a possible source of unusual elastic behavior of five-layer modulated (10,M) martensite of the Ni-Mn-Ga shape memory alloy. This material exhibits anomalous macroscopic shear compliance along specific planes perpendicular to the modulation vector, and this compliance disappears when the modulations become incommensurate. Using a simple mechanical model, we show that modulation phasons in Ni-Mn-Ga can have macroscopic mechanical manifestations, and that the resulting \u0026lsquo;mechanical phasons\u0026rsquo; can relax external shear loadings for commensurate and weakly incommensurate modulations, but not for strongly incommensurate modulations. The model merges ideas from the adaptive martensite theory and electronic-structure considerations, and enables straightforward explanations of several properties of the 10,M lattice, such as spontaneous monoclinic distortion or easy formation and propagation of $a/b$ twins.\n12. From Narrow-gap Semiconductor to Metallic Altermagnet: Optical Fingerprints of Co-Doped FeSb2 Relevance Score: 3.5848 Authors: R. Mathew Roy, M. Povolotskiy, J. Kirschke, C. Prange, Y. Xia, V. Sundaramurthy, P. Puphal, M. Pinteric, M. van de Loo, A. Kreyssig, T. Zhang, A. E. Böhmer, M. Dressel, M. Wenzel Link: http://arxiv.org/abs/2604.28105v2 Summary: The realization of bulk metallic altermagnetism has remained elusive despite the growing number of candidate materials. Here, we present evidence that moderate cobalt substitution ($\\sim$15%) drives the correlated narrow-gap semiconductor FeSb$_2$ into a metallic altermagnetic state persisting up to room temperature. The infrared optical conductivity reveals low-energy interband transitions near 0.1 eV that emerge upon doping and grow with Co concentration. Density functional theory calculations show that these transitions originate exclusively from altermagnetic spin ordering, with spin split bands ($\\sim$0.2 eV) of non-relativistic origin, together with spin-orbit coupling induced band splitting of the order of $\\sim$5 meV near the Fermi level. Co substitution further leads to Fano lineshapes and mode mixing in the infrared-active phonons, reflecting enhanced electron-phonon coupling and local inversion symmetry breaking, while leaving the altermagnetic spin symmetry intact. Our results establish carrier-tuned FeSb$_2$ as a platform for exploring metallic $d$-wave altermagnetism and its coupling to lattice degrees of freedom.\n13. Unveiling the potential of NdPO4 magnetocaloric phases in cryogenic refrigeration Relevance Score: 3.5688 Authors: M. Balli, L. Attou, S-E. Bouzarmine, S. Oubad, K. El Maalam, P. Fournier, S. Mangin Link: http://arxiv.org/abs/2604.28128v1 Summary: The RPO4 orthophosphates (R = rare earth element) have recently attracted a wide interest due to the strong coupling between their electronic, orbital and structural ordering parameters resulting in a variety of functional properties. Herein, we demonstrate that NdPO4 phases synthesized via a facile precipitation growth process unveil promise in low-temperature magnetic cooling. The analysis of their structural properties reveals nanorod forms with diameters of 10 to 20 nm and lengths ranging from 200 to 500 nm while the heat treatment transforms their hexagonal rhabdophane-type structure to a monoclinic anhydrous monazite-type symmetry. Magnetization measurements and DFT calculations show strong antiferromagnetic couplings and the absence of any magnetic ordering in the 2-300 K range. On the other hand, the monoclinic phase of NdPO4 exhibits a large magnetocaloric effect of about 19 J/kg K under 5 T near 3 K, outperforming some reference materials containing more expensive rare-earth elements with high magnetic moments.\n14. Shift of the maxima of the critical currents of different polarity relative to the zero magnetic flux along the flux axis in a superconducting asymmetric aluminum ring Relevance Score: 3.5164 Authors: V. I. Kuznetsov, O. V. Trofimov Link: http://arxiv.org/abs/2604.27848v1 Summary: We measured the rectification of an ac voltage in a structure of superconducting circularly-asymmetric aluminum rings in series, permeated with a magnetic flux and biased with a low-frequency alternating current (without a dc component). This rectification is due to the shift of the maxima of the critical currents of different polarity relative to the zero flux in opposite directions along the flux axis in the asymmetric ring. For the first time, we propose a model for a temperature-dependent phase shift equal to difference between dimensionless kinetic inductances of wide and narrow semirings having the same length and thickness. The shift is not zero in the case of different critical currents densities in both semirings. This is possible only in a situation of different critical temperatures of both semirings. The model describes well the temperature-dependent shift of the maxima of the critical currents, answers the long-standing mysterious challenge of the shift and removes extremely strange contradiction between the results of different measurements, previously found in circularly-asymmetric aluminum structures.\n15. Demonstration of a fermion Quadrupling Condensate via Quantum Monte Carlo Simulation Relevance Score: 3.4814 Authors: Alexandru Golic, Egor Babaev, Johan Carlström Link: http://arxiv.org/abs/2605.00137v1 Summary: Fermionic condensation typically occurs via pairing. In recent decades, however, a fundamental question has emerged: whether alternative forms of order exist, such as condensates of fermion quadruplets. These states\u0026ndash;including charge-4e\u0026quot; superconductors and charge-0\u0026quot; counterflow condensates\u0026ndash;lie beyond the standard Bardeen-Cooper-Schrieffer framework, and require strong fluctuations and correlation effects that invalidate the BCS mean-field description. This makes the problem notoriously difficult to study numerically at a microscopic level, as it involves both strong interactions and the fermionic sign problem. Here, we present a microscopic fermionic model featuring correlated hopping that significantly mitigates the sign problem, enabling rigorous Monte-Carlo-based analysis. Using large-scale simulations, we demonstrate the existence of a fermion-quadrupling condensate with a transition temperature comparable to the hopping energy scale. These results provide direct numerical evidence for quartic fermionic order in a microscopic system and suggest that these exotic states are also experimentally accessible in ultracold atomic gases.\n16. Anharmonic phonon coupling enabled by local inversion symmetry breaking at domain walls in ferroelastics Relevance Score: 3.3847 Authors: Seyyed Jabbar Mousavi, Vivek Unikandanunni, Niccolo Sellati, Paolo Barone, Martina Basini, Steven L. Johnson, Andrey Shalit, Peter Hamm, Mattia Udina, Thomas Feurer Link: http://arxiv.org/abs/2604.28066v2 Summary: In ferroelastic materials, spontaneous symmetry breaking leads to the formation of twin domains. Although the bulk crystal typically remains centrosymmetric, inversion symmetry can be locally broken at the domain walls, potentially changing phonon selection rules and enabling local anharmonic phonon coupling. Here we report direct evidence of such anharmonic coupling in ferroelastic LaAlO$_3$ using two-dimensional Raman-terahertz spectroscopy. We attribute the cross-peaks observed in the two-dimensional spectra to both mechanical and electrical anharmonicity between the $A_{1g}$ Raman-active phonon and the $E_g$ phonon, which acquires finite infrared activity through local inversion symmetry breaking at ferroelastic domain walls. These findings provide new insight into the complex lattice dynamics of ferroelastic materials and highlight the potential of two-dimensional Raman-terahertz spectroscopy to uncover subtle symmetry breaking through the detection of intrinsically weak anharmonic signals.\n17. The second altermagnet candidate in organic conductors: $κ$-(BEDT-TTF)$_2$$m$-HOOCC$_6$H$_4$SO$_3$ Relevance Score: 3.2853 Authors: Kohei Tokura, Takato Masuta, Kazushi Aoyama, Hiroki Akutsu, Yasuhiro Nakazawa, Scott S. Turner Link: http://arxiv.org/abs/2604.27746v1 Summary: We have developed a novel BEDT-TTF-based organic conductor, $κ$-(BEDT-TTF)$_2 m$-HOOCC$_6$H$_4$SO$_3$ ($κ$-$m$-SBA), and propose it as a candidate for altermagnet. Tight-binding band calculations of $κ$-$m$-SBA provide a $t'/t$ of 1.01 at 100 K, indicating that the spin structure is closely aligned to an equilateral triangle ($t'/t= 1$). While most $κ$-type BEDT-TTF-based salts become spin liquids due to the spin frustration caused by the triangular lattice, $κ$-$m$-SBA surprisingly shows a weak ferromagnetic transition at $T_\\mathrm{N} = 14$ K due to a canted antiferromagnetic (AFM) spin structure. Until recently, $κ$-(BEDT-TTF)$_2$Cu[N(CN)$_2$]Cl ($κ$-Cl) was the only $κ$-type organic conductor known to exhibit this order, and it is also recognized as the first candidate for altermagnetism in organic conductors. This was theoretically predicted by Naka et al. in 2019, who demonstrated that $κ$-type organic conductors can be candidates for altermagnetism if they display such order. Consequently, $κ$-$m$-SBA can be considered the second candidate for altermagnetism in organic conductors. Furthermore, numerical calculations demonstrate a characteristic of altermagnets in $κ$-$m$-SBA, namely spin splitting of energy bands.\n18. Exotic Spin Excitation Continuum in a Weakly Coupled Quantum Chainsaw Antiferromagnet Relevance Score: 3.2631 Authors: Asiri Thennakoon, Prena Chaudhary, Sankha Subhra Bakshi, Tommy Park, Tristen Lowrey, Daniel Pajerowski, Christina Hoffmann, Junghong H. He, Hiroaki Ueda, Collin Broholm, Gia-Wei Chern, Seung-Hun Lee Link: http://arxiv.org/abs/2604.27310v1 Summary: Collective motions in strongly interacting magnets involve many spins and are often described in terms of integer-spin excitations. However, in certain cases, the collective motion can behave as if these integer excitations break apart into smaller, particle-like entities with unusual properties. Such fractionalized excitations in quantum magnets are commonly associated either with topological order in two dimensions or with criticality in one dimension. It remains unclear how these distinct mechanisms are connected across a dimensional crossover. Here we investigate the Ti-based quantum antiferromagnet, $Cs_{8}LiNa_{3}Ti_{12}F_{48}$, in which $Ti^{3+}$ ($3d^{1}$, $S=1/2$) ions interact antiferromagnetically within distorted kagome planes. Our inelastic neutron scattering study on a single crystal reveals a frustrated network of weakly coupled spin-$1/2$ chainsaws, realizing a regime of dimensional frustration in which interchain couplings fail to establish coherent two-dimensional order. The magnetic excitation spectrum exhibits a strong continuum spanning the full measured momentum and energy phase space. In addition, the dynamic spin correlation function displays rod-like scattering in momentum space, indicating a quasi-one-dimensional nature of the magnetic correlations. These results point to fractionalized excitations with intrinsically directional character, demonstrating that signatures of one-dimensional criticality can persist within a two-dimensional lattice. Our findings establish anisotropic fractionalization as a distinct organizing principle for quantum-disordered states.\n19. Strong coupling between quantized magnon modes in a YIG microstucture and microwaves in a superconducting resonator Relevance Score: 3.2062 Authors: Seth W. Kurfman, Philipp Geyer, Anoop Kamalasanan, Karl Heimrich, Kwangyul Hu, Tharnier O. Puel, Frank Heyroth, Michael Flatté, Georg Schmidt Link: http://arxiv.org/abs/2604.28145v2 Summary: Strong-coupling experiments based on magnons enable the exploration into on-chip demonstrations involving numerous long-lived excitations. Yttrium iron garnet (YIG) has been considered for decades as a gold standard material for magnonics due to its low-loss magnonic properties. While YIG has successfully demonstrated strong-coupling in macroscopic device geometries, the strong coupling of magnons in truly sub-10 micron YIG structures to date has not yet been realized. This obstacle is due to the difficulty producing large enough effective magnonic mode volume necessary primarily due to thickness limitations of YIG deposition and device fabrication techniques. Here, we demonstrate the use of a microplatelet of YIG, manufactured from a single crystal of YIG via focused ion beam (FIB) techniques, placed on a constricted inductive line of an optimized superconducting lumped element LC resonator to achieve strong coupling between numerous magnon modes and the LC resonator photons. These experimental findings are qualitatively backed by micromagnetic simulations and quantitatively supported by analytical calculations to identify the magnon modes corresponding to the experimentally observed anti-crossings in the microwave transmission signal. Further, we show that these anti-crossings remain even at incredibly low device input powers ($\\leq 10$ fW). The fabrication techniques and device geometry enable the deterministic use of numerous confined magnon modes in micron-scale YIG structures for various magnetic field strengths and orientations at substantially reduced device powers. The results here establish a foundational path forward to achieving efficient magnon-based strong-coupling experiments in micron-scale YIG magnetic elements for effective on-chip studies.\n20. Deep Strong light-matter Coupling in 3D Kane Fermions Relevance Score: 3.2030 Authors: Dmitriy Yavorskiy, David Hagenmuller, Noureddine Charrouj, Yurii Ivonyak, Alexander Kazakov, Yanko Todorov, Wojciech Knap, Marcin Bialek Link: http://arxiv.org/abs/2604.28042v1 Summary: Deep strong light-matter coupling represents an extreme non-perturbative regime of quantum electrodynamics, in which the interaction strength exceeds the bare frequencies of the uncoupled systems. The ground state features strong quantum correlations between photons and matter excitations, and new cavity-driven phase transitions are expected to occur. Whether a superradiant quantum phase transition, marked by spontaneous dipole ordering and photon condensation, is possible has remained a long-standing and controversial question. Such phenomena have been proposed to arise in exotic electronic systems hosting Dirac and Kane fermions, owing to the formal absence of an $A^2$ term in their low-energy Hamiltonian. Here we exploit the ultralow effective mass of Kane fermions to realise Landau polaritons in a bulk mercury cadmium telluride layer coupled to a Fabry-Perot resonator. Using thermally tunable carrier density, we continuously tune the coupling from the weak to the deep-strong regime, achieving a record normalised coupling ratio exceeding 1.6 above room temperature. The measured polariton spectra are in excellent agreement with a rigorous, gauge-invariant microscopic theory. Despite the nonlinear Landau level structure of relativistic Kane fermions, we show that a diamagnetic $A^2$ term naturally emerges and precludes a superradiant phase transition. These results resolve the long-standing controversy surrounding cavity quantum electrodynamics of relativistic-like matter systems, extend deep-strong-coupling physics to Kane fermions, and open new opportunities for polaritonic semiconductor devices operating in extreme light-matter coupling regimes.\n","permalink":"https://nickelates.uk/en/posts/2026-04-30-arxiv-daily/","summary":"\u003cblockquote\u003e\n\u003cp\u003e\u003cstrong\u003eDaily Overview\u003c/strong\u003e:\nThis post sorts papers by relevance to nickelate superconductors. Summaries are AI-generated and may contain errors.\u003c/p\u003e\u003c/blockquote\u003e\n\u003ch2 id=\"1-dimensionality-driven-electronic-and-orbital-transitions-mediating-interfacial-magnetism-in-lanio3camno3-observed-in-situ\"\u003e1. Dimensionality-Driven Electronic and Orbital Transitions Mediating Interfacial Magnetism in LaNiO3/CaMnO3 Observed In Situ\u003c/h2\u003e\n\u003cul\u003e\n\u003cli\u003e\u003cstrong\u003eRelevance Score\u003c/strong\u003e: \u003ccode\u003e4.9640\u003c/code\u003e\u003c/li\u003e\n\u003cli\u003e\u003cstrong\u003eAuthors\u003c/strong\u003e: B-A. Courchene, A. Hampel, S. Beck, J. R. Paudel, J. D. Grassi, L. A. Lapinski, A. M. Derrico, M. Terilli, M. Kareev, C. Klewe, A. Gloskovskii, C. Schlueter, S. K. Chaluvadi, F. Mazzola, I. Vobornik, P. Orgiani, J. Chakhalian, A. J. Millis, A. X. Gray\u003c/li\u003e\n\u003cli\u003e\u003cstrong\u003eLink\u003c/strong\u003e: \u003ca href=\"http://arxiv.org/abs/2604.28054v1\"\u003ehttp://arxiv.org/abs/2604.28054v1\u003c/a\u003e\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003e\u003cstrong\u003eSummary\u003c/strong\u003e: Emergent magnetic states at oxide interfaces arise from the interplay of charge transfer, orbital reconstruction, and dimensional confinement, offering a route to engineered correlated-electron behavior in nanoscale spintronic materials. Here, we combine in situ synthesis, polarization-dependent angle-resolved photoelectron spectroscopy, X-ray magnetic circular dichroism, and first-principles electronic-structure calculations to investigate LaNiO3/CaMnO3 superlattices. We show that reducing the LaNiO3 thickness drives a metal-insulator transition accompanied by loss of electronic coherence and an orbital-polarization crossover in the ultrathin limit. These changes weaken charge transfer across the interface and suppress the interfacial Mn magnetic moment in CaMnO3, revealing that the emergent ferromagnetic state is directly governed by electronic confinement in LaNiO3. The insulating state and orbital reconstruction are reproduced by density functional theory combined with dynamical mean-field theory. Together, these results establish a direct and tunable coupling among electronic, orbital, and magnetic degrees of freedom in oxide heterostructures.\u003c/p\u003e","title":"arXiv Daily: nickelate superconductors 2026-04-30"},{"content":" Daily Overview: Dear readers, welcome to today\u0026rsquo;s daily overview of the nickelate superconductor field. The highlight of today focuses on a deeper understanding of the electronic structure of hybrid Ruddlesden-Popper nickelates. In [1], a theoretical study using the DFT+DMOT method reveals that the monolayer-bilayer alternating structure of La₅Ni₃O₁₁ exhibits distinctly different electronic behaviors under ambient pressure. Specifically, the monolayer Ni ions display an orbital-selective Mott insulating state, while the bilayer Ni ions exhibit strongly correlated quasiparticle behavior, with magnetic correlations predominantly governed by the bilayer. This work unveils the critical role of confinement effects and orbital-dependent correlations in determining the physical properties of nickel-based superconductors. Additionally, several other studies in today\u0026rsquo;s overview are worth noting: - [2] A high-pressure study of the cluster Mott insulator GaNb₄Se₈ demonstrates the evolution from \u0026ldquo;wavefunction collapse\u0026rdquo; to superconductivity, providing an ideal platform for understanding pressure-induced Mott transitions in correlated systems. - [3] Proposes a scheme to achieve high-temperature superconductivity on the surface of Weyl semimetals by engineering Van Hove singularities. This interface-enhanced superconductivity mechanism parallels the approach of exploring superconductivity in nickelate thin-film interfaces and is highly inspiring. - [8] Realizes a programmable superconducting diode effect in the nematic superconductor FeSe, demonstrating a method to manipulate the superconducting state by controlling nematic domains. This offers new tuning dimensions and technical paradigms for the study of nickel-based superconductors that exhibit similar electronic correlations and nematic order. The above direct research on nickelates, along with physically related work, constitutes the core content of today\u0026rsquo;s overview.\n1. Electronic structure, quasiparticle renormalizations, and magnetic correlations in the alternating single-layer bilayer nickelate La$_5$Ni$_3$O$_{11}$ Relevance Score: 5.1706 Authors: I. V. Leonov Link: http://arxiv.org/abs/2604.26627v1 Summary: Using the DFT+DMFT method, this study systematically analyzes the electronic structure and magnetic correlation properties of the mixed Ruddlesden-Popper nickelate La₅Ni₃O₁₁ (1212-LNO) under ambient pressure. The results reveal qualitative differences between structurally distinct monolayer and bilayer Ni ions, indicating the importance of confinement effects and orbital-dependent correlations. The e_g electrons of bilayer Ni form strongly renormalized quasiparticle bands, with effective mass enhancement factors of approximately 3.5 and 4.2 for the Ni x²-y² and 3z²-r² orbitals, respectively. In contrast, the e_g states of monolayer Ni exhibit an orbital-selective Mott insulating state: the 3z²-r² state has a narrow gap, while the x²-y² state is metallic and strongly incoherent (non-Fermi liquid). Magnetic correlation analysis shows intertwined spin-charge density wave stripes within the bilayer NiO₆ layers, with the primary instability corresponding to the \u0026ldquo;up-down-0\u0026rdquo; spin pattern at wave vector Q=(1/3,1/3), competing with the bicollinear \u0026ldquo;up-up-down-down\u0026rdquo; stripe state at (1/4,1/4). The 3d electrons of monolayer Ni tend toward Néel-type magnetic order. Under pressure, 1212-LNO undergoes an orbital-selective Mott insulator-metal transition, where the monolayer Ni e_g states become metallic, displaying non-Fermi liquid (bad metal) behavior. Correlated effects significantly reconstruct the magnetic correlations, shifting the dominant magnetic correlation from DFT-predicted monolayer dominance to bilayer dominance, similar to bilayer nickelates.\n2. From Wavefunction Collapse to Superconductivity: Evolution of the Electronic State in Compressed GaNb4Se8 Relevance Score: 4.2016 Authors: Yuejian Wang, Zhongyan Wu, K C Bhupendra, Dongzhou Zhang, Lin Wang, Sanjay V. Khare, Lilian Prodan, Vladimir Tsurkan Affiliations: Yanshan University, University of Toledo, University of Augsburg, University of Chicago, Moldova State University, Oakland University Link: http://arxiv.org/abs/2604.26203v1 Summary: This study systematically reveals the electronic state evolution of the cluster-based Mott insulator GaNb₄Se₈ under pressure through high-pressure transport measurements, synchrotron X-ray diffraction, and first-principles calculations. At low pressures, the resistance follows the Efros-Shklovskii variable-range hopping mechanism with a localization length of approximately 6.1 Å, close to the Nb₄ cluster spacing (~6.7 Å), confirming a \u0026ldquo;wavefunction collapse\u0026rdquo; phenomenon where charge carriers are strictly confined within individual clusters at low temperatures. At about 5 GPa, the system begins transitioning to a metallic state, yet the cubic-to-monoclinic structural phase transition occurs at around 20 GPa, indicating a decoupling between electronic delocalization and changes in structural symmetry. Under high pressure, superconductivity emerges in the correlated metallic state with a coherence length of approximately 80–90 Å. Theoretical calculations demonstrate that pressure suppresses Jahn-Teller distortion and weakens Nb–Se bond strength, thereby broadening the Nb 4d band and leading to the collapse of the Mott insulator. These results establish GaNb₄Se₈ as an ideal platform for investigating transport evolution governed by correlation effects in cluster-based solids.\n3. Engineering superconductivity on the surface of Weyl semimetals Relevance Score: 4.0561 Authors: Riccardo Vocaturo, Mattia Trama Link: http://arxiv.org/abs/2604.26859v1 Summary: This study proposes a feasible scheme to achieve high-temperature superconductivity on the surface of Weyl semimetals through material interface engineering. Using PtBi₂ as a specific model, it is theoretically demonstrated that depositing an appropriate additional layer on the Weyl semimetal surface can induce a surface van Hove singularity, which originates from the dispersion distortion of topologically protected Fermi arcs due to long-range hopping (e.g., third-nearest-neighbor hopping). Employing a variational mean-field method based on free energy minimization to calculate the superconducting properties under s-wave pairing, it is found that when the chemical potential approaches the van Hove singularity energy, the surface superconducting critical temperature is enhanced by more than 30 times compared to the bulk, with a sharp asymmetry: below the singularity, the quasi-one-dimensional conical dispersion leads to good Fermi surface nesting, while above the singularity, nesting conditions disappear. This mechanism naturally explains the experimentally observed surface superconducting transition temperature (approximately 5 K) being much higher than the bulk (approximately 0.2 K) in PtBi₂, as well as the highly dispersed superconducting gap values among different samples. By integrating out the capping layer to obtain an effective interface Green’s function, it is proven that selective hybridization can equivalently realize surface long-range hopping, thereby providing an experimentally accessible tuning pathway for engineering two-dimensional high-temperature superconductivity and other topological quantum phases.\n4. Superconductivity-Enabled Conversion of Ferromagnetic Resonance into Standing Spin Waves Relevance Score: 3.8143 Authors: Ya. V. Turkin, N. G. Pugach, F. M. Maksimov, A. S. Pakhomov, A. I. Chernov, V. I. Belotelov, S. N. Polulyakh, V. S. Stolyarov Link: http://arxiv.org/abs/2604.27076v1 Summary: This study experimentally and theoretically demonstrates that a conventional diffusive superconductor (Nb) can convert the uniform ferromagnetic resonance (FMR) mode in an adjacent ferromagnetic insulator (Bi-GdIG) into perpendicular standing spin waves (PSSW). In Bi-GdIG/Nb bilayers, an additional resonance peak emerges in the microwave transmission spectrum only when the temperature is below the superconducting transition temperature of Nb, and it appears adjacent to the uniform FMR peak. Microscopic theory, combining the quasiclassical Keldysh–Usadel equation with Landau–Lifshitz–Gilbert dynamics, reveals that the conversion mechanism relies on two cooperative elements: interfacial spin-transfer torque mediated by spin-polarized triplet Cooper pairs and a depth-dependent effective field generated by Abrikosov vortices. This mechanism enables energy transfer from the uniform mode to the lowest-order exchange-standing mode without requiring eddy currents or inhomogeneous microwave fields, and it can be tuned via temperature, magnetic field, and supercurrent biasing. This provides a new avenue for engineering low-dissipation spin-wave modes in superconducting hybrid platforms.\n5. Non-local Tunneling Spectroscopy of Inelastic Quasiparticle Relaxation in Superconducting 1-D Wires Relevance Score: 3.7819 Authors: Kevin M. Ryan, Detlef Beckmann, Venkat Chandrasekhar Affiliations: National Institute of Standards and Technology Link: http://arxiv.org/abs/2604.26862v1 Summary: This study employs mesoscopic three-terminal Cu and Al normal metal–insulator–superconductor (NIS) devices to investigate nonlocal quasiparticle transport on the scale of the superconducting coherence length. Using a dual-bias scheme (with the detector biased both above and below the superconducting gap) and symmetry analysis to extract signals from the effect of quasiparticle energy imbalance on the self-consistent pair potential, we observe pair-breaking-induced nonlocal conductance features that are antisymmetric with respect to voltage bias polarity and exhibit a sharp onset near the single-electron tunneling energy of approximately 3Δ. By comparing experimental results with quasiclassical simulations incorporating inelastic effects, we obtain estimates of the energy-dependent inelastic scattering time. Additionally, we demonstrate dynamical effects arising from large supercurrents, which can be decomposed within the same formalism based on particle-hole symmetry and supercurrent direction. These findings provide a spectroscopic tool for a deeper understanding of nonequilibrium relaxation and transport mechanisms of quasiparticles in superconductors, and they point to future developments of this methodology.\n6. Resolving growth-induced off-stoichiometry in AgCrSe$_2$ single crystals Relevance Score: 3.6306 Authors: Felix Eder, Zeno Maesen, Yurii Skourski, Enrico Giannini, Oksana Zaharko, Fabian O. von Rohr Affiliations: Helmholtz-Zentrum Dresden-Rossendorf, University of Geneva, PSI Link: http://arxiv.org/abs/2604.26887v1 Summary: Layered delafossite-type antiferromagnet AgCrSe₂ is a superionic conductor at high temperatures, and at low temperatures, it has been reported to exhibit anomalous Hall effect and Kondo-like physics. These abnormal transport properties have been almost entirely based on single crystals grown by chemical vapor transport (CVT) using CrCl₃ as a transport agent, which systematically introduces off-stoichiometry, resulting in an actual composition of Ag₁₋ₓCr(Se₂₋ᵧClᵧ) (x ≈ y ≈ 0.08). Through elemental analysis, single-crystal X-ray diffraction, and magnetization measurements, this work confirms that chlorine incorporation and silver deficiency in CVT crystals significantly alter the magnetic properties, reducing the Néel temperature to 46 K, compared to 58 K for stoichiometric polycrystalline samples prepared by solid-state synthesis. To address this issue, researchers optimized the Ag/Se self-flux growth method combined with hot centrifugation separation, successfully obtaining large stoichiometric AgCrSe₂ single crystals. The magnetic transition temperature and saturation field of these self-flux crystals are fully consistent with those of stoichiometric polycrystalline samples, restoring the intrinsic magnetic behavior. This study demonstrates that self-flux growth is a reliable approach for preparing high-quality stoichiometric AgCrSe₂ single crystals, providing a stable and comparable material platform to re-examine whether the previously reported anomalous transport phenomena are intrinsic or caused by off-stoichiometry.\n7. Revealing magnetism in the distorted kagome $R$Ti$_3$Bi$_4$ ($R$ = Nd, Sm, Gd) via ARPES and XMCD Relevance Score: 3.5861 Authors: C. Lim, F. Ballester, A. Kar, M. Alkorta, D. Subires, J. Dai, M. Tallarida, E. Vescovo, T. K. Kim, C. Cacho, C. Yi, S. Roychowdhury, A. Kumar Sharma, Y. Choi, G. Fabbris, J. Strempfer, P. Gargiani, C. Shekhar, C. Felser, I. Errea, M. G. Vergniory, S. Blanco-Canosa Link: http://arxiv.org/abs/2604.26636v1 Summary: This study systematically investigates the electronic and magnetic structures of the distorted kagome materials R Ti₃Bi₄ (R = Nd, Sm, Gd) using angle-resolved photoemission spectroscopy (ARPES), density functional theory (DFT), and X-ray magnetic circular dichroism (XMCD). ARPES and DFT reveal that the bulk electronic bands are primarily dominated by the hybridization of Ti orbitals, while a weak electron-type pocket near the Γ point is identified as a surface state. Isotropic X-ray absorption spectra (XAS) at the rare-earth M₄,₅ edges confirm that R exists in the R³⁺ oxidation state. Applying XMCD sum rules supplemented by atomic multiplet theory calculations, the spin and orbital magnetic moments are obtained. XMCD at the Ti L₂,₃ edges indicates a small magnetic moment at the Ti site in GdTi₃Bi₄, which is attributed to the nearest-neighbor coupling between the Ti kagome layer and the Gd zigzag chains, and the total magnetic moment of Gd arises from contributions of both f and d electrons. This comprehensive investigation provides critical insights into the spin-flip transitions and anomalous Hall effect observed in R Ti₃Bi₄ kagome metals.\n8. Programmable superconducting diode from nematic domain control in FeSe Relevance Score: 3.5200 Authors: R. D. H. Hinlopen, C. Putzke, L. Holeschovsky, R. Nicholls, F. Ronning, E. D. Bauer, N. E. Hussey, P. J. W. Moll Affiliations: University of Bristol, Los Alamos National Laboratory, HFML-FELIX, Max Planck Institute for Structure and Dynamics of Matter Link: http://arxiv.org/abs/2604.26631v2 Summary: In the nematic superconductor FeSe, researchers have realized a programmable superconducting diode effect through the interaction between electronic domain walls and vortices. By employing low-temperature focused ion beam processing on high-quality single crystals, they ensured a high degree of device symmetry to eliminate geometric factors that could cause symmetry breaking. Experimental results showed that when the magnetic field direction is nearly aligned with the nematic twin boundaries, the current–voltage curves exhibit a significant polarity-dependent difference in critical current, achieving a diode efficiency as high as approximately 75%. This nonreciprocal transport originates from the asymmetric pinning of vortices at nematic domain walls, where the domain wall configuration directly encodes the polarity and magnitude of the diode effect. By applying large current pulses with durations as short as microseconds (quenching rates exceeding 10^7 K/s), the sample can be rapidly heated above the nematic phase transition temperature and subsequently cooled quickly, altering the domain distribution and enabling deterministic switching of the diode polarity and efficiency. This method allows repeated writing of different diode states under the same magnetic field and temperature, demonstrating a new paradigm for programming correlated-electron-state patterns in superconducting circuits, and offers a general design strategy for other superconductors with low-temperature electronic nematic order, such as iron-based superconductors.\n9. Metalization of topological insulators Relevance Score: 3.5000 Authors: Xian-Peng Zhang, Yan-Qing Feng, Ji-Feng Shao, Haiwen Liu, Yugui Yao Link: http://arxiv.org/abs/2604.26698v1 Summary: This paper proposes that in systems dominated by Berry curvature, the traditional criterion for distinguishing metals from insulators based on the presence or absence of carriers near the Fermi surface fails, as transport is governed by interband quantum coherence across the entire Fermi sea. Using the BHZ model of HgTe/CdTe quantum wells and a quantum master equation approach, the authors develop a microscopic transport theory for bulk topological insulators when the density of states at the Fermi level is zero. They find that impurity scattering causes the decay of interband coherence (i.e., quantum decoherence), which creates a new longitudinal transport channel in topologically trivial regions without edge contributions. The conductivity of this channel scales linearly with impurity density in the dilute impurity limit (contrary to Drude’s inverse relation) and remains finite when the Fermi level lies in the bulk band gap; moreover, its resistivity is inversely proportional to temperature, resembling strange metal behavior. This decoherence-induced transport mechanism fundamentally challenges the metal-insulator dichotomy based on band theory, suggesting that quantum decoherence can serve as a source of longitudinal response beyond the Drude paradigm.\n10. Large magnetoresistance and weak-antilocalization in the nodal-line semimetal VP2 Relevance Score: 3.4606 Authors: Chunxiang Wu, Shuijin Chen, Tingyu Zhou, Le Liu, Xin Peng, Jianjian Jia, Xinyu Yu, Hangdong Wang, Jinhu Yang, Jianhua Du, Minghu Fang Link: http://arxiv.org/abs/2604.26480v1 Summary: Researchers have successfully grown high-quality VP2 single crystals and, through systematic measurements of longitudinal and Hall resistivities combined with electronic band structure and Fermi surface calculations, confirmed that VP2 is a type-II nodal-line semimetal. Under high magnetic fields, the magnetoresistance exhibits linear behavior without saturation, reaching 170% at 40 K and 9 T; this behavior is dominated by the intrinsic electronic structure and Lorentz force, as verified by resistivity anisotropy measurements and numerical simulations. Additionally, approximately 2.24% V⁴⁺ magnetic impurities (spin-1/2) are present in the crystals, leading to a Kondo effect minimum in the resistivity at low temperatures, while the low-field conductance shows typical weak antilocalization behavior that can be fitted by the Hikami-Larkin-Nagaoka equation. This study indicates that VP2 provides an ideal platform for exploring the electronic transport properties of topological materials containing magnetic impurities.\n11. Negative nonlocal and local voltages (resistances) in a quasi-one-dimensional superconducting aluminum structure Relevance Score: 3.4495 Authors: V. I. Kuznetsov, O. V. Trofimov Link: http://arxiv.org/abs/2604.26814v1 Summary: This study explores nonlocal electron transport mechanisms by measuring negative nonlocal and local DC voltages in quasi-one-dimensional superconducting aluminum structures near the critical temperature under a magnetic field. The structures consist of wide and narrow wires, operating in the normal-superconducting transition temperature range (T_cn \u0026lt; T \u0026lt; T_cw). Experiments reveal that when current flows through the wide wire and the connected narrow wire, both negative nonlocal voltage and negative local voltage appear simultaneously under a specific measurement circuit configuration, with magnitudes increasing linearly with current to a peak and then sharply dropping, while no such phenomenon is observed in other circuit configurations. The generation of negative voltage is attributed to charge imbalance induced by quasiparticle currents across the normal-superconducting interface. The researchers plotted the temperature and magnetic field dependencies of the current, resistance, and voltage at the negative voltage peak, and performed fitting based on equilibrium and non-equilibrium superconducting fluctuation theories, incorporating Aslamazov-Larkin and Maki-Thompson corrections. The results show that the peak currents for negative nonlocal and local voltages coincide with the superconducting critical current, and the negative resistances are approximately -1.2 Ω and -0.5 Ω. The study reveals the key role of quasiparticle charge imbalance in nonlocal transport, providing experimental evidence for understanding non-equilibrium effects related to superconducting fluctuations.\n12. Hidden Crossover and Relaxor-Like Response from Emerging Polar Skyrmion Correlations in Ferroelectric Superlattices Relevance Score: 3.4427 Authors: Zhiyang Wang, Fei Yang, Long-Qing Chen Link: http://arxiv.org/abs/2604.26100v1 Summary: Through large-scale phase-field simulations, researchers have uncovered a hidden thermal crossover of polar skyrmions deeply embedded within the ferroelectric phase of ferroelectric superlattices: as temperature decreases, skyrmions evolve from a randomly distributed, layer-uncorrelated state to an ordered stacking with interlayer correlation. This crossover does not involve additional symmetry breaking or new order parameters, yet it generates a pronounced broad dielectric peak in the intermediate temperature range. This anomaly originates from the competition between two effects: the correlation-enhanced dielectric response driven by increasing interlayer skyrmion correlations and the polarization stiffness that suppresses dielectric fluctuations at low temperatures. More critically, under an alternating electric field, this dielectric peak shifts toward higher temperatures with increasing frequency, exhibiting typical relaxor ferroelectric behavior despite the absence of compositional disorder or polar nanoregions in the system. This indicates that collective correlations of topological defects can produce relaxor-like responses without the conventional order-disorder mechanism. This work establishes a new paradigm where topological defect correlations serve as an organizing principle for thermodynamic anomalies and provides a stray-free pathway to engineer dielectric responses by tuning interlayer polarization contrast.\n13. Finite-Temperature Ferromagnetic Correlations of the Kagome Lattice Hubbard Model Relevance Score: 3.4063 Authors: Francisco Correia, Kyle Corbett, Ehsan Khatami Link: http://arxiv.org/abs/2604.26827v1 Summary: Using two accurate finite-temperature methods, numerical linked-cluster expansion and determinant quantum Monte Carlo, this study systematically investigates the variation of ferromagnetic correlations with doping and interaction strength in the Kagome lattice Hubbard model. It is found that repulsive interactions significantly enhance ferromagnetic correlations at high electron densities; as the interaction strength increases, the region of strong ferromagnetic correlations extends from near the band insulator toward half-filling, smoothly connecting with the Nagaoka ferromagnetism near the Mott insulating regime. Through charge compressibility calculations, the critical interaction strength for the metal-insulator transition at half-filling is precisely estimated. These results deepen the understanding of magnetic tendencies away from half-filling and lay the foundation for subsequent studies in systems such as ultracold atoms in optical lattices.\n14. Influence of strain on the anomalous Hall and Nernst effects in Fe thin films Relevance Score: 3.2272 Authors: Ao Nakagawa, Ryo Toyama, Keisuke Masuda, Weinan Zhou, Hirofumi Suto, Kodchakorn Simalaotao, Yoshio Miura, Yuya Sakuraba, Tetsunori Koda Affiliations: National Institute of Technology, Oshima college, University of Tsukuba, Kyoto Institute of Technology, National Institute for Materials Science (NIMS) Link: http://arxiv.org/abs/2604.26257v1 Summary: By epitaxially growing Fe thin films on MgO and MgAl₂O₄ substrates, this study systematically modulated strain through substrate mismatch and deposition conditions, and combined scaling law analysis with first-principles calculations to investigate the effects of strain on the anomalous Hall effect (AHE) and anomalous Nernst effect (ANE). Scaling analysis revealed that the intrinsic anomalous Hall conductivity (AHC) varies with the tetragonal distortion ratio (c/a) and closely aligns with theoretical calculations based on Berry curvature corrections, confirming the strain-mediated modulation of the intrinsic AHE mechanism. However, the anomalous Nernst conductivity (ANC) deviates significantly from theoretical predictions and exhibits a markedly different c/a dependence. These results highlight a key distinction in the physical origins of AHC and ANC in Fe films: AHC is primarily governed by the intrinsic Berry curvature mechanism, whereas ANC is strongly influenced by extrinsic contributions such as scattering.\n15. Emergent surface resonance from charge density wave symmetry breaking in TiSe2 Relevance Score: 3.2204 Authors: Turgut Yilmaz, Yi Sheng Ng, Muhammad Awais Fiaz, Anil Rajapitamahuni, Asish K. Kundu, Shawna M. Hollen, Polina M. Sheverdyaeva, Paolo Moras, Ivana Vobornik, Jun Fujii, Shinichiro Ideta, Kenya Shimada, Boris Sinkovic, Elio Vescovo, Hui-Qiong Wang, Jin-Cheng Zheng Link: http://arxiv.org/abs/2604.26685v1 Summary: This study identifies a surface resonance state (SRS) induced by charge density wave (CDW) symmetry breaking in 1T-TiSe₂. Experimentally, micro-angle-resolved photoelectron spectroscopy (μ-ARPES), combined with photon-energy-dependent measurements and polarization analysis, resolves a sharp two-dimensional SRS in the CDW-reconstructed low-energy spectrum, whose dispersion exhibits negligible variation with kz, indicating quasi-two-dimensional character and surface localization. The spectral weight of the SRS significantly weakens and vanishes at approximately 160 K, whereas the bulk CDW transition temperature is typically 202 K. Density functional theory (DFT+U) slab calculations reveal that CDW folding brings the valence and conduction bands near degeneracy, selectively forming localized resonant states on the surface, with their formation modulated by correlation effects. This SRS is neither a simple topological surface state nor a CDW-folded replica band but rather a surface-localized state embedded within the bulk continuum. The findings demonstrate that the interplay between CDW symmetry breaking and electronic correlations can generate novel surface states, providing a general framework for designing low-dimensional quantum states in van der Waals layered materials through symmetry breaking and band engineering.\n16. Tracking visible pulsed laser annealing of Hf$_{0.5}$Zr$_{0.5}$O$_2$ heterostructures with in situ transmission electron microscopy Relevance Score: 3.1923 Authors: Aida Amini, Shruti Verma, Katharina Kohlmann, Sebastian Obernberger, Jean-Christof Lamanque, Andreas Rüdiger, Kenneth R. Beyerlein Affiliations: Institut national de la recherche scientifique (INRS) Link: http://arxiv.org/abs/2604.26718v2 Summary: This study employed visible nanosecond pulsed laser annealing on Si₃N₄/TiN/Hf₀.₅Zr₀.₅O₂ thin film heterostructures, with in situ transmission electron microscopy used to track the crystallization process in real time. Due to the wide bandgap of HZO, the work utilized the absorption of visible light in TiN to generate heat, thus avoiding photochemical interference. The critical laser energy density and ferroelectric phase fraction were systematically measured for different HZO thicknesses (7, 8, and 15 nm), revealing a clear threshold behavior: an 8 nm film subjected to a single pulse energy density of 177 mJ/cm² achieved 86% ferroelectric orthorhombic phase (oIV-HZO). Finite element simulations elucidated the heat transfer dynamics within the heterostructure, indicating that partial melting of the silicon nitride substrate limited the temperature to 1900°C, and the observed threshold behavior supported a kinetic crystallization pathway involving a tetragonal intermediate phase. Quantitative phase analysis confirmed that oIV-HZO was the dominant phase in all samples after laser annealing, with oIV phase fractions of 76% and 63% for the 7 nm and 15 nm films, respectively. These results demonstrate that visible light pulsed laser annealing can achieve efficient ferroelectric phase engineering of HZO thin films, offering a new route for back-end-of-line compatible scalable fabrication of ferroelectric devices.\n17. Achieving Large Uniaxial and Homogeneous Strain in Two-Dimensional Materials Relevance Score: 3.1246 Authors: Yangchen He, Jessica Kienbaum, Wuzhang Fang, Hongrui Ma, Ying Wang, Ping Yuan, Daniel A. Rhodes Affiliations: University of Wisconsin-Madison Link: http://arxiv.org/abs/2604.26164v1 Summary: This paper reports a high-yield sample preparation and device strain platform that overcomes the limitations of traditional two-dimensional material strain engineering, including small strain ranges (typically below 1.5%), poor cyclic repeatability, and low strain transfer efficiency at low temperatures. The platform forms controllable trenches on a silicon substrate via lithography and deep etching, enhances strain transfer by using a polycaprolactone (PCL)-functionalized surface, and employs a substrate cracking process to ensure uniform height on both sides of the trench. Experiments show that this platform achieves uniform uniaxial strains of up to approximately 4% in two-dimensional materials such as CrSBr, with a linear relationship between strain and driving voltage and negligible slip during cycling. Furthermore, controllable linear strain gradients (up to 0.06%/μm) can be designed over tens of micrometers, providing a new route for systematic studies of flexoelectric and flexomagnetic phenomena. This method is applicable to a variety of transition metal dichalcogenides (e.g., 2H-MoTe₂, 1T′-MoTe₂, and T_d-WTe₂), achieving a record strain of approximately 5.5% in T_d-WTe₂, accompanied by a continuous redshift of the Raman A₁³ mode and its clear separation from the A₁² mode at 2% strain. This platform overcomes previous strain technology bottlenecks, enabling reversible strain modulation limited only by the material\u0026rsquo;s intrinsic fracture strength, and operates stably at low temperatures.\n18. Third-order intrinsic anomalous Hall effect as a transport fingerprint of altermagnets Relevance Score: 3.1186 Authors: Longjun Xiang, Hao Jin, Jian Wang Affiliations: Shenzhen University, The University of Hong Kong, Quantum Science Center of Guangdong-Hongkong-Macao Greater Bay Area (Guangdong) Link: http://arxiv.org/abs/2604.26665v1 Summary: Based on spin group symmetry analysis, this study demonstrates that the third-order intrinsic anomalous Hall effect is universally allowed in ten spin Laue groups associated with altermagnets when spin-orbit coupling is considered. By combining symmetry constraints with second-order Berry curvature-induced anomalous velocity, a resonant third-order intrinsic anomalous Hall effect is discovered near altermagnetic band crossings in the Lieb lattice altermagnet and experimentally realized V₂Se₂O. The study further identifies the Berry curvature quadrupole moment (activated by finite spin-orbit coupling) encoded in the second-order Berry curvature as the microscopic quantum geometric origin of this resonance. These results establish the third-order intrinsic anomalous Hall effect as an intrinsic quantum geometric transport fingerprint of altermagnets and extend the hierarchy of intrinsic anomalous Hall effects in collinear quantum magnets.\n19. Tunable high-Chern-number Chern insulators in rhombohedral tetralayer graphene/hBN moiré superlattices Relevance Score: 3.1041 Authors: Chuanqi Zheng, Chushan Li, Ke Huang, Chenyu Zhang, Kenji Watanabe, Takashi Taniguchi, Hao Yang, Dandan Guan, Liang Liu, Shiyong Wang, Yaoyi Li, Hao Zheng, Canhua Liu, Jinfeng Jia, Xueyang Song, Zhiwen Shi, Guorui Chen, Xiao Li, Tingxin Li, Xiaoxue Liu Affiliations: Quantum Science Center of Guangdong-Hong Kong-Macao Greater Bay Area (Guangdong), Shanghai Research Center for Quantum Sciences, Hefei National Laboratory, Shanghai Jiao Tong University, Southern University of Science and Technology, City University of Hong Kong, Hong Kong University of Science and Technology, National Institute for Materials Science Link: http://arxiv.org/abs/2604.26643v1 Summary: This paper systematically investigates the transport properties of the hole-doped side in rhombohedral tetralayer graphene (RTG)/hexagonal boron nitride (hBN) moiré superlattices. By varying the twist angle and alignment orientation, multiple Chern insulators with high Chern numbers are observed. At integer moiré filling ν = -1, the previously reported C = -4 integer Chern insulator is obtained; meanwhile, newly discovered symmetry-broken Chern insulating states are found at fractional filling ν ≈ -2.5 or -2.6, with Chern numbers of +3, ±2, and ±1. These Chern insulating states appear in both hBN orientations but are highly sensitive to the moiré wavelength: the C = -4 state exists only when the moiré wavelength exceeds 13 nm, while the other states exhibit more complex wavelength dependence. Furthermore, all these states can be effectively tuned by the moiré wavelength, displacement field, and external magnetic field, and the states at fractional fillings are suppressed in a vertical magnetic field of about 0.3–0.5 T. The results reveal unique topological band structures in hole-doped RTG/hBN moiré superlattices, providing a highly tunable platform for exploring correlated topological phases in flat bands with high Chern numbers.\n20. The Meissner effect does not require radial charge flow Relevance Score: 3.1001 Authors: A. V. Nikulov Link: http://arxiv.org/abs/2605.10945v1 Summary: This paper points out that the emergence of persistent currents in the Meissner effect originates from the quantization of Cooper pair angular momentum, rather than from radial charge flow and the action of the Lorentz force. Traditional superconductivity theories (such as Ginzburg-Landau theory and BCS theory), based on the wave function proposed by Landau in 1941, treat angular momentum quantization as the core mechanism for explaining the Meissner effect and flux quantization, the latter having been experimentally verified (e.g., observations of flux quantization in thick-wall and thin-wall cylinders). In contrast, Jorge Hirsch\u0026rsquo;s hole superconductivity theory posits radial charge flow as a necessary prerequisite, but this paper emphasizes that the persistent current resulting from quantization is not merely a theoretical deduction but a robust experimental fact that cannot be explained by the Lorentz force. Furthermore, by analyzing why macroscopic quantum phenomena violate the correspondence principle—such as Cooper pairs, as bosons, occupying the ground state, and the duality of the wave function increasing the kinetic energy dispersion of macroscopic condensates—the paper further demonstrates how angular momentum quantization can be observed at macroscopic scales. Therefore, explaining the Meissner effect does not require invoking radial charge flow.\n","permalink":"https://nickelates.uk/en/posts/2026-04-29-arxiv-daily/","summary":"\u003cblockquote\u003e\n\u003cp\u003e\u003cstrong\u003eDaily Overview\u003c/strong\u003e:\nDear readers, welcome to today\u0026rsquo;s daily overview of the nickelate superconductor field. The highlight of today focuses on a deeper understanding of the electronic structure of hybrid Ruddlesden-Popper nickelates. In [1], a theoretical study using the DFT+DMOT method reveals that the monolayer-bilayer alternating structure of \u003cstrong\u003eLa₅Ni₃O₁₁\u003c/strong\u003e exhibits distinctly different electronic behaviors under ambient pressure. Specifically, the monolayer Ni ions display an orbital-selective Mott insulating state, while the bilayer Ni ions exhibit strongly correlated quasiparticle behavior, with magnetic correlations predominantly governed by the bilayer. This work unveils the critical role of confinement effects and orbital-dependent correlations in determining the physical properties of nickel-based superconductors. Additionally, several other studies in today\u0026rsquo;s overview are worth noting: - [2] A high-pressure study of the cluster Mott insulator \u003cstrong\u003eGaNb₄Se₈\u003c/strong\u003e demonstrates the evolution from \u0026ldquo;wavefunction collapse\u0026rdquo; to superconductivity, providing an ideal platform for understanding pressure-induced Mott transitions in correlated systems. - [3] Proposes a scheme to achieve high-temperature superconductivity on the surface of Weyl semimetals by engineering Van Hove singularities. This interface-enhanced superconductivity mechanism parallels the approach of exploring superconductivity in nickelate thin-film interfaces and is highly inspiring. - [8] Realizes a programmable superconducting diode effect in the nematic superconductor \u003cstrong\u003eFeSe\u003c/strong\u003e, demonstrating a method to manipulate the superconducting state by controlling nematic domains. This offers new tuning dimensions and technical paradigms for the study of nickel-based superconductors that exhibit similar electronic correlations and nematic order. The above direct research on nickelates, along with physically related work, constitutes the core content of today\u0026rsquo;s overview.\u003c/p\u003e","title":"arXiv Daily: nickelate superconductors 2026-04-29"},{"content":" Daily Overview: Today\u0026rsquo;s highlight work focuses on the controllable experimental realization of multi-orbital models in strongly correlated electron systems, which is highly relevant to the current pursuit of understanding complex electronic structures in the field of nickel-based superconductivity. In [1], the researchers propose a novel architecture based on ultracold fermions and optical superlattices, successfully realizing the three-band Emery model—a core theoretical framework for describing the low-energy physics of cuprate and nickel-based superconductors. By precisely tuning orbital-dependent interactions and charge transfer energies, and combining quantum walk experiments with quantum Monte Carlo simulations, this work observes, for the first time in an undoped system, a finite-temperature metal-insulator crossover and the consequent emergence of antiferromagnetic correlations, which bears a profound analogy to the electronic correlation behavior in nickel-based superconducting parent compounds. Furthermore, the Hamiltonian learning protocol developed in this study can invert experimental data to extract an effective single-band Hubbard model, providing a novel methodology for resolving effective low-energy models in future multi-orbital nickelate systems. Although the remaining papers do not directly target nickelates, their investigations into strong-coupling superconductivity theory, electron-phonon coupling dynamics, and interface defect engineering also offer valuable references for frontier issues such as the ambient-pressure pairing mechanism, excitonic effects, and interface engineering in nickel-based superconductivity. arXiv submission processing window: 2026-04-23 20:33 to 2026-04-24 18:58 UTC.\n1. Realizing multi-orbital Emery models with ultracold atoms Relevance Score: 4.0484 Authors: Conall McCabe, Jamie Boyd, Kaizhao Wang, Martin Lebrat, Cindy Regal, Adam Kaufman, Ana Maria Rey, Lukas Homeier Link: http://arxiv.org/abs/2604.22955v1 Summary: This study proposes an optical superlattice architecture that utilizes ultracold fermions to realize a three-band Emery model. By combining lattice beams with controllable interference, orbital degrees of freedom that reproduce key features of the cuprate band structure are constructed, allowing independent tuning of orbital-dependent interactions and charge transfer energy. Single-particle quantum walk experiments can benchmark the resulting tight-binding model. Combined with determinant quantum Monte Carlo simulations, a finite-temperature metal-insulator crossover is found in the undoped system, accompanied by the emergence of antiferromagnetic correlations observable in current experiments. Furthermore, a Hamiltonian learning protocol is developed to extract an effective single-band Hubbard model from the experimental realization of the Emery model. This work provides a feasible route to simulate multi-orbital Hubbard physics using quantum gas microscopes.\n2. Dynamical stability and multifunctional properties of Ni2+/Pr3+ co-doped CsPbCl3 perovskite: insights from first-principles lattice dynamics and carrier transport Relevance Score: 3.8430 Authors: Sikander Azam, Asif Zaman, Qaiser Rafiq, Amin Ur Rahman, Saleem Ayaz Khan Affiliations: RIPHAH International University, University of West Bohemia Link: http://arxiv.org/abs/2604.22874v1 Summary: The stability and optoelectronic properties of Ni²⁺/Pr³⁺ co-doped CsPbCl₃ perovskite were systematically investigated using first-principles FP-LAPW method (WIEN2k). The calculations indicate that Ni²⁺ and Pr³⁺ substitute Pb²⁺ at the B-site and Cs⁺ at the A-site, respectively, maintaining charge balance. Co-doping significantly increases the formation energies of halogen and metal vacancies, reducing deep defect levels in the band gap, while phonon dispersion confirms that the system remains dynamically stable before and after doping. The introduction of Ni²⁺/Pr³⁺ suppresses low-frequency vibrations and induces mode splitting in the 3–5 THz range, enhancing phonon scattering and reducing lattice thermal conductivity. Regarding mechanical properties, the elastic constants and bulk modulus increase without compromising ductility. Electronic structure reveals that Ni-3d and Pr-4f states appear at band edges, reducing effective carrier masses and passivating vacancy states. Optical absorption exhibits a red shift, with high-frequency and low-frequency dielectric constants of 2.4 and 7.4, respectively. Carrier transport analysis shows that lighter effective masses lead to higher mobilities. Overall, Ni²⁺/Pr³⁺ co-doping effectively reduces defect concentration and comprehensively improves the optoelectronic performance of CsPbCl₃.\n3. Theoretical prediction of strong-coupling superconductivity in a hypothetical NaAlH3 phase at ambient pressure Relevance Score: 3.6660 Authors: Izabela A. Wrona, Yinwei Li, Radoslaw Szczesniak, Artur P. Durajski Link: http://arxiv.org/abs/2604.22300v1 Summary: This study systematically investigates the lattice dynamics, electronic structure, and superconducting properties of the hypothetical cubic Pm-3m phase ternary hydride NaAlH₃ under ambient pressure using first-principles calculations combined with the Migdal-Eliashberg formalism. Phonon dispersion and ab initio molecular dynamics simulations demonstrate that this phase exhibits dynamical and thermal stability within the theoretical framework. The electronic structure reveals metallic behavior, with the density of states at the Fermi level primarily arising from the orbital contributions of Al and Na. By solving the Eliashberg equations, an extremely strong electron-phonon coupling (λ = 2.23) is found, yielding a superconducting critical temperature as high as 73.7 K under a Coulomb pseudopotential μ* = 0.1. The calculated superconducting energy gap ratio (2Δ(0)/k_BT_c ≈ 4.8) and specific heat jump (ΔC/γT_c ≈ 2.2) significantly exceed the predictions of the BCS weak-coupling theory, highlighting the strong-coupling nature of superconductivity in this hypothetical phase.\n4. Influence of Ni Doping on the Structural, Morphological, Optical, and Electrical Properties of Nanocrystalline Cd1-xMnxS Thin Films Relevance Score: 3.6564 Authors: Himanshu Sharma Pathok, Padma Pani Shahu, Himanshu Kalita, Prasanta Kumar Saikia Link: http://arxiv.org/abs/2604.22561v1 Summary: In this study, Cd₁₋ₓMnₓS (x=0.4) nanograined thin films doped with different concentrations of nickel (Ni) were prepared via chemical bath deposition, and the effects of Ni doping on the structural, morphological, optical, and electrical properties of the films were systematically analyzed. X-ray diffraction and transmission electron microscopy results revealed that the films exhibited a cubic zincblende structure, with improved crystallinity and reduced microstrain and dislocation density upon Ni doping. Field-emission scanning electron microscopy showed that the films were uniform, dense, and crack-free, with grain size increasing with Ni content and thickness stabilizing in the range of 181.2–189.1 nm. Optical measurements indicated high transmittance of 75%–90% in the visible and near-infrared regions, while the optical band gap decreased from 2.72 eV to 2.62 eV as Ni content increased from 1% to 4%. Current-voltage measurements demonstrated that Ni doping significantly enhanced the electrical conductivity of the films, which further increased under illumination, confirming their photoconductive characteristics. These results suggest that Ni doping can effectively tune the properties of Cd₁₋ₓMnₓS thin films, making them promising for application as window layers in thin-film solar cells and related optoelectronic devices.\n5. Resonance Frequency Shift Measurements of SRF Cavities at DESY Relevance Score: 3.5407 Authors: Rezvan Ghanbari, Thorsten Buettner, Wolfgang Hillert, Karol Kasprzak, Tom Krokotsch, Ricardo Monroy-Villa, Detlef Reschke, Lea Steder, Alexey Sulimov, Hans Weise, Marc Wenskat, Mateusz Wiencek, Jonas Wolff Link: http://arxiv.org/abs/2604.22596v1 Summary: This paper reports on a dedicated resonance frequency shift measurement setup developed and tested at DESY, used to investigate the variations in frequency and quality factor of superconducting radio-frequency niobium cavities during the superconducting-to-normal state transition. The initial system enabled precise determination of the superconducting penetration depth and the electron mean free path within the normal-state skin depth, and detected an anomalous frequency dip near the critical temperature for niobium cavities containing interstitial atoms (such as oxygen and nitrogen). The study found that the frequency drift observed in the initial measurement stage originated from mechanical stress due to thermal expansion of the support structure, which could be largely eliminated by loosening the cavity mounting screws, and an empirical frequency drift correction method was validated as reliable. Recent upgrades also include the addition of a thermal shield around the cavity, effectively reducing spatial temperature gradients and significantly improving measurement accuracy and reproducibility. The upgraded setup allows stable investigation of frequency shift and quality factor across the full temperature range above 7 K, providing a reliable means for in-depth understanding of the superconducting properties of niobium cavities modified by interstitial atoms.\n6. Uncovering long-lived relaxation channel and exciton-phonon coupling in \\textrm{Ta\\textsubscript{2}NiSe\\textsubscript{5}} via non-degenerate pump-probe spectroscopy Relevance Score: 3.3633 Authors: Poulami Ghosh, Anupama Chauhan, Sidhanta Sahu, Sk Kalimuddin, Mintu Mondal, N. Kamaraju Link: http://arxiv.org/abs/2604.22218v1 Summary: By extending the delay window to 500 ps via nondegenerate optical pump–probe spectroscopy (pump at 3.14 eV, probe at 1.57 eV), the temperature-dependent nonequilibrium dynamics of Ta₂NiSe₅ (TNSe) were investigated. In addition to the known subpicosecond relaxation channel (~0.7–0.9 ps, arising from carrier cooling and recombination accompanied by exciton reconstruction), a significantly slower recovery process (decay time ~280–600 ps) was observed, attributed to enhanced scattering between excitons and nonequilibrium phonons, which delays the restoration of equilibrium excitonic correlations. Superimposed on this biexponential background, two coherent phonon modes at 1.0 THz and 2.9 THz were observed, exhibiting distinctly different coupling behaviors: the 1.0 THz mode displays an order-parameter-like temperature dependence, indicating strong coupling with the excitonic condensate, while the 2.9 THz mode shows no significant coupling and originates from anharmonic lattice dynamics associated with the structural phase transition. These results elucidate the hierarchy of relaxation pathways in TNSe and highlight the importance of extending the time window in pump–probe measurements to fully capture long-lived exciton–phonon dynamics.\n7. Dynamic Moiré Potentials and Robust Wigner Crystallization in Large-Scale Twisted Transition Metal Dichalcogenides Relevance Score: 3.3493 Authors: Yifan Ke, Chuanjing Zeng, Xinming Qin, Wei-Lin Tu, Wei Hu, Jinglong Yang Link: http://arxiv.org/abs/2604.22343v1 Summary: This study develops a machine-learning-based workflow integrating DeePMD molecular dynamics with the DeepH electronic structure prediction framework, combined with first-principles calculations, to efficiently simulate the time-dependent structural and electronic responses of twisted bilayer transition metal dichalcogenides (exemplified by WS₂) containing over 3000 atoms at experimentally relevant twist angles. The results show that low-temperature lattice vibrations and relaxation deepen the moiré potential wells, further narrow the lowest conduction band, and promote the formation of strongly localized electronic states. Using DFT-derived moiré potentials that incorporate these dynamical effects, density matrix renormalization group calculations reveal robust Wigner crystallization behavior and a three-electron state with a kagomé pattern consistent with recent experiments. This workflow provides a practical approach for exploring large moiré supercells beyond static configurations, elucidating the interplay among lattice dynamics, electronic localization, and emergent correlated states.\n8. Tantalum Damascene Coplanar Waveguide Resonators Fabricated Using 300 mm Scale Processes Relevance Score: 3.2899 Authors: Ekta Bhatia, Yingge Du, Krishna P Koirala, Chung Kow, Mingzhao Liu, Juan Macy, Tharanga R. Nanayakkara, Francisco Ponce, Satyavolu S. Papa Rao, Drew J. Rebar, Peter V. Sushko, Brent A VanDevender, Chongmin Wang, Marvin G. Warner, Zhihao Xiao Link: http://arxiv.org/abs/2604.22086v1 Summary: This study explores the fabrication of tantalum coplanar waveguide resonators on 300 mm silicon wafers using a Damascene process, aiming to replace the native oxide layer on device sidewalls with a metal/substrate interface, thereby reducing losses caused by surface oxides in superconducting transmon devices. By intentionally embedding an oxide layer during fabrication to mimic sidewall oxidation, we compared the performance of devices under five different interface treatments, including buried oxide interfaces and pristine interfaces. Low-temperature characterization reveals that the resonant frequencies of Damascene devices are significantly lower than theoretical predictions, indicating a substantial contribution from kinetic inductance. Compared to devices with buried oxide layers, pristine interface devices show a moderate improvement in performance, suggesting a reduction in surface participation ratio. Although the experiments differ in total attenuation configurations, the results still indicate that this process has the potential to improve superconducting quantum device performance by eliminating native sidewall oxides, providing a foundation for further optimization in the future.\n9. Corner Majorana states in semi-Dirac materials Relevance Score: 3.2797 Authors: M. García Olmos, Y. Baba, R. A. Molina, M. Amado Link: http://arxiv.org/abs/2604.22553v2 Summary: This paper presents a theoretical framework for realizing Majorana bound states in two-dimensional semi-Dirac materials, which feature anisotropic dispersion such that edge states propagate only along specific boundaries under certain conditions, forming isolated one-dimensional channels. By introducing Rashba spin-orbit coupling, a Zeeman field, and proximity to an s-wave superconductor, an effective p-wave pairing is induced between the edge states. In finite geometries, each edge can independently undergo a topological phase transition to become a one-dimensional topological superconductor, yielding four localized zero-energy modes at the four corners of the ribbon. At low energies, the edge-state subspace can be described as coupled Kitaev chains, clearly revealing the origin, robustness, and tunability of the corner Majorana modes. This scheme does not rely on engineered nanostructures, vortices, or higher-order lattice topology, thereby providing a new platform for naturally realizing Majorana modes in two-dimensional systems.\n10. Enhanced Tantalum Superconducting Resonator Performance via All-Surface Organic Monolayer Passivation Relevance Score: 3.2472 Authors: Harsh Gupta, Moritz Singer, Benedikt Schoof, Anna Cattani-Scholz, Shreya Sharma, Luca Rommeis, Marc Tornow Affiliations: Indian Institute of Technology Roorkee, Fraunhofer Institute for Electronic Microsystems and Solid State Technologies (EMFT), Technical University of Munich Link: http://arxiv.org/abs/2604.22112v1 Summary: This study employs self-assembled organic monolayers to achieve full-interface passivation of freshly etched tantalum and silicon surfaces, thereby inhibiting the regrowth of native oxides. Characterization via contact angle measurements, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, and transmission electron microscopy confirms the formation of ordered, nanometer-thick films that effectively block oxidation. Microwave measurements of coplanar waveguide resonators in the 5–9 GHz band reveal internal quality factors as high as 1.8×10⁶ in the single-photon regime at 100 mK, representing an approximately 140% improvement compared to untreated devices containing native oxides. Power and temperature-dependent measurements indicate that the performance enhancement stems from a significant reduction in dielectric loss attributed to interfacial two-level systems. This molecular-level passivation method enables the engineering of low-loss interfaces, offering a scalable pathway for fabricating high-coherence superconducting quantum devices.\n11. Chirality Transfer to the Centrosymmetric Magnetic Sublattice in the Hybrid Perovskite (R)-/(S)-3-Fluoropyrrolidinium Copper(II) Chloride Relevance Score: 3.2435 Authors: Zheng Zhang, Mingyu Xu, Jose L. Gonzalez Jimenez, Stephen Zhang, Weiwei Xie, Xianghan Xu, Daniel B. Straus Affiliations: University of Minnesota, Princeton University, Tulane University, Michigan State University Link: http://arxiv.org/abs/2604.22952v1 Summary: This study reports a novel two-dimensional chiral magnetic metal halide material, (R)- and (S)-(C₄H₉FN)₂CuCl₄, in which chiral organic cations 3-fluoropyrrolidinium are introduced into the centrosymmetric inorganic Cu-Cl sublattice. Although the inorganic layer structure itself possesses inversion symmetry, the chiral cations successfully induce chiral magnetic ordering, whereas no chiral magnetic order is observed in the racemic mixture containing equal amounts of R and S cations. Magnetization measurements reveal an antiferromagnetic phase transition with Néel temperature TN = 2.23 K along the direction perpendicular to the Cu-Cl layers in both chiral and racemic samples, and specific heat measurements confirm this transition. More importantly, the chiral variants exhibit field-induced magnetochirality, observed through a quadratic magnetoelectric effect, while the racemate shows no such effect, indicating that chiral magnetic ordering exists exclusively in the chiral materials. This work demonstrates that by incorporating chiral cations into chiral organic–inorganic hybrid magnets, chirality can be transferred to the centrosymmetric magnetic sublattice, yielding materials that simultaneously possess structural chiral optical properties and chiral magnetic order, thereby providing a viable strategy for designing novel multifunctional chiral magnetoelectric and spintronic devices.\n12. Non-volatile superconducting tunnelling magnetoresistance memory enabled by exchange-field gap engineering Relevance Score: 3.2333 Authors: Sonam Bhakat, Pushpak Banerjee, Ahmedullah Aziz, Jackson Miller, Avradeep Pal Affiliations: University of Tennessee, Indian Institute of Technology Bombay, Victoria University of Wellington Link: http://arxiv.org/abs/2604.22214v1 Summary: This study realizes exchange-field-controlled superconducting gap engineering by integrating a de Gennes spin valve with a superconducting tunnel junction in a vertical current geometry, thereby developing a nonvolatile superconducting tunneling magnetoresistance memory device. The device leverages the relative orientation of the ferromagnetic insulating layers to modulate the exchange field in the superconducting layer, producing two distinct superconducting gap voltages in parallel and antiparallel magnetization states, and exhibits fully switchable quasiparticle tunneling magnetoresistance from the superconducting transition temperature down to 0.25 K. This memory element achieves nanowatt-level read power consumption at millivolt bias with zero standby power; its vertical junction structure and niobium-based material platform are compatible with superconducting logic circuits and scalable cryogenic memory arrays. Experiments confirm that the device enables bistable switching of the gap voltage via magnetic field at all temperatures, offering a low-power, nonvolatile intrinsic superconducting memory solution for cryogenic computing systems.\n13. Fraunhofer Patterns in Atomic Josephson Junctions Relevance Score: 3.1864 Authors: Kevin T. Geier, Giampiero Marchegiani, Vijay Pal Singh, Juan Polo, Luigi Amico Link: http://arxiv.org/abs/2604.22923v1 Summary: This study proposes the realization of Fraunhofer-like critical current modulation in an atomic Josephson junction subjected to a synthetic magnetic field. Through numerical simulations based on the Gross-Pitaevskii equation, a movable tunneling barrier is constructed in a quasi-two-dimensional Bose-Einstein condensate with an applied synthetic magnetic field, revealing that the critical current exhibits a characteristic Fraunhofer pattern as a function of magnetic flux. This effect originates from the synthetic magnetic field-induced phase gradient, which spatially modulates the current density within the junction, leading to constructive or destructive interference. The study further elucidates the crucial role of Josephson vortices in forming the spatially modulated current distribution: each modulation period corresponds to a vortex pinned to the junction, with phase kink features analogous to fluxons in superconducting junctions, yet distinguished by normal cores and larger sizes due to the neutral superfluid nature. These results demonstrate that atomic Josephson junctions can exhibit Fraunhofer patterns akin to those in superconducting short junctions even under static synthetic magnetic fields, while simultaneously incorporating nonlinear effects characteristic of long junctions. This work provides a new avenue for studying spatial coherence in Josephson junctions using matter-wave circuits and holds significant implications for the development of novel quantum technologies.\n14. Accurate Nanoscale Mapping of Electric Fields across Random Grain Boundaries in Polycrystalline Oxides Using Precession-Assisted 4D-STEM Relevance Score: 3.1384 Authors: Sangjun Kang, Hyeyoung Cho, Maximilian Töllner, Anna Rose Nelson, Ziming Ding, Xiaoke Mu, Di Wang, Wolfgang Rheinheimer, Kai Wang, Bai-Xiang Xu, Jakob Konstantin Laux, Mahmoud Serour, Karsten Albe, Andreas Klein, Christian Kübel Affiliations: University of Stuttgart, Lanzhou University, Karlsruhe Institute of Technology, Technical University of Darmstadt Link: http://arxiv.org/abs/2604.22398v1 Summary: This study proposes a four-dimensional scanning transmission electron microscopy method that integrates electron beam precession with advanced post-processing (iterative Sobel edge detection and singular value decomposition) to precisely measure nanoscale electric fields at random grain boundaries in polycrystalline oxides. By accurately correcting the center disk position in nanobeam electron diffraction patterns, this method effectively eliminates artifacts caused by orientation contrast and dynamical scattering in conventional center-of-mass analysis, significantly enhancing the accuracy and robustness of extracting local electric fields and charge distributions. In comparative experiments on random grain boundaries in BaTiO₃ and SrTiO₃, the new method demonstrates superior performance over the traditional center-of-mass approach. By combining atomic simulations to separate the electric fields of space charge layers, the average inner potential difference across grain boundaries, and the effects of elemental segregation, this study experimentally proves that the method can faithfully map electromagnetic fields and their charge distributions in complex polycrystalline samples, laying a foundation for quantitative analysis using differential phase contrast in scanning transmission electron microscopy.\n15. Classifying magnons in itinerant ferromagnets from linear response TDDFT: Fe, Ni and Co revisited Relevance Score: 3.0043 Authors: Thorbjørn Skovhus, Thomas Olsen Link: http://arxiv.org/abs/2604.22484v1 Summary: This study employs a new implementation of linear-response time-dependent density functional theory (LR-TDDFT) to perform first-principles calculations of the magnetic excitation spectra in typical itinerant ferromagnets (body-centered cubic iron, face-centered cubic nickel, face-centered cubic cobalt, and hexagonal close-packed cobalt). By introducing the self-enhancement function (the product of the non-interacting Kohn-Sham susceptibility and the exchange-correlation kernel), the authors classify the collective nature of characteristic peaks in the many-body spectral function, distinguishing coherent from decoherent collective excitations based on whether the real part of the self-enhancement function crosses unity at the magnon peak, and assessing the influence of Landau damping according to the magnitude of its imaginary part. The calculations reveal multiple coexisting coherent magnon branches in body-centered cubic iron, while in face-centered cubic nickel, the primary magnon branch decoheres near the Brillouin zone boundary, with incoherent valley magnons subsequently carrying significant spectral weight. This analytical approach also naturally yields a definition of the many-body Stoner spectrum and quantitatively describes the binding energy of Stoner pair excitations. This work clarifies the physical mechanisms underlying complex magnetic excitation features in itinerant ferromagnets and validates that the proposed method rigorously satisfies the Goldstone condition, thereby accurately describing the coupling between collective modes and the Stoner continuum.\n","permalink":"https://nickelates.uk/en/posts/2026-04-24-arxiv-daily/","summary":"\u003cblockquote\u003e\n\u003cp\u003e\u003cstrong\u003eDaily Overview\u003c/strong\u003e:\nToday\u0026rsquo;s highlight work focuses on the controllable experimental realization of multi-orbital models in strongly correlated electron systems, which is highly relevant to the current pursuit of understanding complex electronic structures in the field of nickel-based superconductivity. In [1], the researchers propose a novel architecture based on ultracold fermions and optical superlattices, successfully realizing the three-band Emery model—a core theoretical framework for describing the low-energy physics of cuprate and nickel-based superconductors. By precisely tuning orbital-dependent interactions and charge transfer energies, and combining quantum walk experiments with quantum Monte Carlo simulations, this work observes, for the first time in an undoped system, a finite-temperature metal-insulator crossover and the consequent emergence of antiferromagnetic correlations, which bears a profound analogy to the electronic correlation behavior in nickel-based superconducting parent compounds. Furthermore, the Hamiltonian learning protocol developed in this study can invert experimental data to extract an effective single-band Hubbard model, providing a novel methodology for resolving effective low-energy models in future multi-orbital nickelate systems. Although the remaining papers do not directly target nickelates, their investigations into strong-coupling superconductivity theory, electron-phonon coupling dynamics, and interface defect engineering also offer valuable references for frontier issues such as the ambient-pressure pairing mechanism, excitonic effects, and interface engineering in nickel-based superconductivity.\n\u003cstrong\u003earXiv submission processing window\u003c/strong\u003e: 2026-04-23 20:33 to 2026-04-24 18:58 UTC.\u003c/p\u003e","title":"arXiv Daily: nickelate superconductors 2026-04-24"},{"content":" Daily Overview: Today\u0026rsquo;s highlights focus on an in-depth understanding of the electronic structure of mixed Ruddlesden-Popper nickelates. In [1], X-ray absorption spectroscopy and resonant inelastic X-ray scattering studies on (La,Pr)₃Ni₂O₇₋δ thin films reveal that both strain and oxygen content modulation lead to the delocalization of the oxygen 2p₂ orbital and the nickel 3d₂² orbital, while long-range spin density wave order is significantly suppressed, and short-range magnons remain robust, indicating that orbital delocalization and short-range magnetic fluctuations are prerequisites for superconductivity. [2] provides a theoretical analysis of the 1313-phase La₃Ni₂O₇, pointing out that its superconductivity primarily originates from a three-layer subsystem with s^{±}-wave pairing symmetry, but the single-layer subsystem, acting as a weakly connected layer forming S-N-S Josephson junctions, suppresses the global transition temperature. This work thus deduces that the 2222-phase, rather than the 1313-phase, is the true host of high-temperature superconductivity in the RP-phase La₃Ni₂O₇ family. These two studies deepen the understanding of the superconducting mechanism in nickelates from experimental and theoretical perspectives, respectively. arXiv submission processing window: 2026-04-22 20:37 to 2026-04-23 18:00 UTC.\n1. $3d_{z^2}$ orbital delocalization and magnetic collapse in superconducting (La,Pr)$_3$Ni$_2$O$_{7-δ}$ films Relevance Score: 5.6451 Authors: Xiaoyang Chen, Wenliang Zhang, Fei Peng, Ting Cui, Guangdi Zhou, Zezhong Li, Jaewon Choi, Lizhi Xu, Yiu-Fung Chiu, Stefano Agrestini, Sahil Tippireddy, Haoliang Huang, Heng Wang, Xianfeng Wu, Peng Li, Jin-Feng Jia, Mirian Garcia-Fernandez, Yi Lu, Er-Jia Guo, Qi-Kun Xue, Zhuoyu Chen, Donglai Feng, Ke-Jin Zhou Link: http://arxiv.org/abs/2604.21899v2 Summary: This study utilized X-ray absorption spectroscopy and resonant inelastic X-ray scattering to independently control the strain and oxygen content of (La,Pr)₃Ni₂O₇₋δ thin films, tracking the microscopic evolution from a non-superconducting parent phase to a superconducting phase. The results demonstrate that both tuning methods induce delocalization of the oxygen 2p_z and nickel 3d_z² orbitals, as evidenced by spectral weight transfer from the \u0026ldquo;upper Hubbard\u0026rdquo; peak to the hole peak in the O K-edge absorption spectra, accompanied by broadening and weakening of the Ni L-edge absorption spectra and dd excitations. Concurrently, the intensity and correlation length of the long-range spin density wave (SDW) order are significantly suppressed, indicating direct competition with superconductivity; while short-range magnons are damped, their bandwidth remains unchanged. This suggests that the delocalization of oxygen 2p_z and nickel 3d_z² orbitals, along with the robustness of short-range magnons during the melting of the SDW order, are prerequisites for achieving superconductivity, thus providing constraints for theoretical models and pointing toward an orbital-selective pathway for designing nickel-based superconductors.\n2. Pairing mechanism and superconductivity in 1313 phase La$_3$Ni$_2$O$_7$ Relevance Score: 5.3451 Authors: Cui-Qun Chen, Ming Zhang, Fan Yang, Dao-Xin Yao Link: http://arxiv.org/abs/2604.21533v1 Summary: Using density functional theory combined with dynamical mean-field theory (DFT+DMFT) and the random phase approximation (RPA), we systematically investigated the electronic structure and superconducting mechanism of the 1313-phase La₃Ni₂O₇. DMFT calculations reveal that the monolayer subsystem exhibits a nearly insulating state, with the d_{z²} orbital displaying Mott physics, while the trilayer subsystem remains metallic and is primarily responsible for superconductivity, with its Ni-e_g orbitals being hole-doped relative to bulk La₄Ni₃O₁₀. Based on the low-energy effective Hamiltonian derived from DMFT, RPA analysis yields an s^{±}-wave pairing symmetry within the trilayer subsystem. Compared to bulk La₄Ni₃O₁₀, the significantly reduced superconducting transition temperature in the 1313 phase arises from two factors: first, hole doping weakens the pairing strength; second, the monolayer subsystem acts as a weak-link layer, forming S-N-S Josephson junctions between adjacent trilayer superconducting layers, which suppresses interlayer phase coherence and further lowers the global transition temperature. Overall, the high-temperature superconductivity in the Ruddlesden-Popper La₃Ni₂O₇ family should be attributed to the 2222 phase rather than the 1313 phase.\n3. Two-gap to Single-gap Transition and Two-dome-like Superconductivity in Alkali-Metal Intercalated Bilayer PdTe2 Relevance Score: 4.1783 Authors: Yu-Lin Han, Shu-Xiang Qiao, Kai-Yue Jiang, Jie Zhang, Bao-Tian Wang, Ping Zhang, C. S. Ting, Hong-Yan Lu Link: http://arxiv.org/abs/2604.21635v1 Summary: Based on first-principles calculations and the anisotropic Migdal-Eliashberg equation, this work systematically investigates the effect of alkali metal intercalation on the superconducting properties of bilayer PdTe₂. The results show that intercalation significantly enhances its weak superconductivity, raising the superconducting transition temperature from 1.4 K to 5.0–13.5 K and exhibiting a double-dome-like Tc evolution, with the rubidium-intercalated system achieving the highest Tc of 13.5 K, which can be further increased to 14.5 K under biaxial tensile strain, while the strain-dependent Tc also displays a double-dome feature, reflecting the synergistic modulation of band structure and electron-phonon coupling. The study further reveals a systematic correlation between the superconducting gap and interlayer interaction: lithium intercalation induces a typical double-gap state, whereas alkali metals with larger atomic radii (Na, K, Rb, Cs) transform the system into a single-gap characteristic, a transition arising from the intercalation-induced interlayer expansion that modulates interlayer coupling. Additionally, the pristine and Li/Na-intercalated bilayer systems possess nontrivial band topology, indicating that layered PdTe₂ serves as an ideal platform for exploring the coexistence of superconductivity and topology. These results deepen the understanding of the electron-phonon coupling mechanism from an anisotropic perspective and provide feasible pathways for enhancing Tc and realizing multifunctional quantum properties.\n4. Single-crystal growth and magnetic, magnetoelectric, and optical properties of ferroaxial-type SrMn$_2$Ni$_6$Te$_3$O$_{18}$ Relevance Score: 4.0466 Authors: Ryoya Nakamura, Shinichiro Asai, Yusuke Nambu, Takatsugu Masuda, Kenta Kimura Affiliations: The University of Tokyo, Osaka Metropolitan University, Kyoto University, High Energy Accelerator Research Organization, The University of Osaka Link: http://arxiv.org/abs/2604.21460v1 Summary: Single crystals of the ferrotoroidic oxide family member SrMn₂Ni₆Te₃O₁₈ were successfully grown, and their structural, magnetic, magnetoelectric, and optical properties were systematically investigated. Electric-field-induced spatial distribution imaging of optical rotation revealed that the single crystal preferentially forms a single ferrotoroidic (FA) domain. Magnetic susceptibility and neutron diffraction measurements indicated that the magnetic moments of Mn²⁺ and Ni²⁺ undergo antiferromagnetic ordering at T_N = 83 K, forming a c-axis collinear double-spin-flip antiferromagnetic structure. All independent magnetoelectric tensor components allowed by the magnetic point group 6/m′ were detected, with the χ₃₃ component exhibiting significant temperature-dependent anomalies including a peak and sign reversal. Preferential formation of a single FA domain and analogous χ₃₃ anomalies were also observed in the isostructural compound PbMn₂Ni₆Te₃O₁₈. These findings demonstrate that the ferrotoroidicity and magnetic characteristics within this structural framework are robust with respect to Sr-Pb substitution.\n5. Intertwined charge density wave, tunable anti-dome superconductivity, and topological states in kagome metal VSn Relevance Score: 4.0168 Authors: Shu-Xiang Qiao, Ya-Ping Li, Jie Zhang, Yi Wan, Na Jiao, Meng-Meng Zheng, Hong-Yan Lu, Ping Zhang Link: http://arxiv.org/abs/2604.21488v1 Summary: This study predicts a new 1:1 kagome metal VSn via first-principles calculations and reveals an intrinsic charge density wave (CDW) order driven by electron-phonon coupling. As hydrostatic pressure or hole doping concentration increases, the CDW is gradually suppressed, and superconductivity emerges, with the superconducting transition temperature exhibiting a rare anti-dome-shaped dependence: initially decreasing and then increasing, showing non-monotonic variation under pressures of 3–90 GPa or hole doping levels of 0.1–1.25. This anti-dome superconducting phase diagram originates from the evolution of phonon modes, which first harden and then soften, along with band reconstruction, where the electron-phonon coupling contribution shifts from being dominated by in-plane vibrations of V atoms to in-plane vibrations of Sn atoms. Beyond a critical tuning threshold, the CDW order reappears. Notably, VSn maintains nontrivial topological properties throughout the entire superconducting region, as evidenced by nonzero topological invariants and clear surface states. This work unveils the rich quantum behavior of intertwined CDW, superconductivity, and topological states in VSn, providing a platform for designing 1:1 kagome superconducting topological metals and exploring the interplay of multiple quantum phases in kagome systems.\n6. Superconductivity induced by altermagnetic spin fluctuations in high-pressure MnB$_4$ Relevance Score: 3.8824 Authors: Danylo Radevych, Mercè Roig, Daniel F. Agterberg, Igor I. Mazin Link: http://arxiv.org/abs/2604.21561v1 Summary: Recent experiments have observed superconductivity in non-magnetic MnB₄ at 158 GPa with a critical temperature as high as 14 K, yet electron-phonon coupling calculations based on density functional perturbation theory predict a Tc below 1 K, indicating that the conventional mechanism cannot explain this phenomenon. In this work, using density functional theory calculations, we find that MnB₄ is close to an altermagnetic instability, and propose that superconductivity is driven by altermagnetic spin fluctuations. To verify the pairing symmetry, a two-orbital tight-binding model is constructed by integrating out the boron states near the Fermi level, identifying the extended s-wave as the dominant pairing instability. If this mechanism is confirmed, it would be the first report of superconductivity driven by altermagnetic spin fluctuations.\n7. Effect of Mn Substitution on Superconductivity in PrFeAs(O,F): Role of Magnetic Impurities Relevance Score: 3.8148 Authors: Priya Singh, Konrad Kwatek, Tatiana Zajarniuk, Taras Palasyuk, Cezariusz Jastrzębski, A. Szewczyk, Michał Wierzbicki, Shiv J. Singh Link: http://arxiv.org/abs/2604.21684v1 Summary: This study systematically investigates the effect of Mn substitution for Fe on superconductivity in PrFe₁₋ₓMnₓAsO₀.₇F₀.₃ (0 ≤ x ≤ 0.1) through structural analysis, Raman spectroscopy, density functional theory calculations, electrical transport, and magnetic measurements. X-ray diffraction and Raman analysis confirm that Mn preferentially enters the FeAs layers, resulting in lattice expansion and suppression of Fe-related vibrational modes. Electrical transport measurements reveal that the superconducting transition temperature decreases progressively from 48 K at x = 0 and completely disappears at x = 0.1, accompanied by an increase in low-temperature resistivity and an insulating behavior. Magnetization and magnetotransport measurements indicate continuous degradation of superconducting coherence, critical current density, upper critical field, and vortex activation energy with increasing Mn content. The results demonstrate that Mn acts as an efficient magnetic impurity, strongly disrupting the electronic and magnetic environment of the FeAs layers. Compared with other rare-earth systems, Pr-based superconductors exhibit relatively stronger superconducting robustness, highlighting the crucial role of rare-earth-dependent electronic correlations in impurity effects.\n8. Controlled Manipulation of Intermediate State in a Type-I Superconductor Relevance Score: 3.7002 Authors: Xin-Sheng Gao, Qun Wang, Ya-Xun He, Xing-Jian Liu, Jun-Han Zhang, Kang-Hong Yin, Jia-Ying Zhang, Jun-Yi Ge Affiliations: Shanghai University Link: http://arxiv.org/abs/2604.21499v1 Summary: This study employs low-temperature magnetic force microscopy (MFM) to directly image and controllably manipulate the intermediate state of a type-I superconductor in high-purity tantalum single crystals. The evolution of magnetic flux morphology from tubular to stripe-like structures during flux penetration and expulsion is systematically tracked, revealing significant topological hysteresis induced by geometric barriers. Using the MFM probe, individual flux tubes are dragged and merged, and local reconstruction of entire stripe domains is achieved. Under AC excitation, a reversible stripe-grid-stripe transition is observed, where the dynamic reorganization is driven by current-induced flux penetration and pinning effects. The corresponding phase diagram shows that the threshold current decreases with increasing applied magnetic field and increases with increasing AC frequency. This work provides a feasible approach for actively manipulating flux structures in type-I superconductors, reveals rich dynamic behaviors, and lays the foundation for flux-based superconducting devices.\n9. Pressure-Tuned Competing Electronic States in Layered Tellurides Relevance Score: 3.6582 Authors: Mahmoud Abdel-Hafiez, Govindaraj Lingannan, D. A. Chareev, A. N. Vasiliev, Anas Abutaha, Kadir Can Dogan, Mehmet Yagmurcukardes, Mehmet Egilmez, Hasan Sahin, Sami El-Khatib Affiliations: Korzhinskii Institute of Experimental Mineralogy RAS, University of Doha for Science and Technology, Ural Federal University, University of Sharjah, Hamad Bin Khalifa University, American University of Sharjah, Izmir Institute of Technology Link: http://arxiv.org/abs/2604.21336v1 Summary: Under hydrostatic pressure, the magnetotransport behavior of the layered semiconductor 2H-MoTe₂ was investigated. At ambient pressure, the transport transitions from high-temperature metallic behavior to activated conduction, eventually entering a strong localization regime characterized by three-dimensional Mott variable-range hopping, accompanied by a magnetoresistance anomaly near 45 K and an unsaturated magnetoresistance of up to 60 T. Upon applying compression up to 15.6 GPa, the insulating state is rapidly suppressed, giving rise to a low-resistivity state dominated by quantum interference, which exhibits a crossover from weak antilocalization to weak localization at low temperatures. A phenomenological model describes the magnetoresistance in different regimes, and the extracted characteristic electronic length scales remain similar in the localization and quantum interference regions. First-principles calculations reveal that pressure continuously closes the band gap, resulting in a semimetallic electronic structure. These results collectively depict a pressure-tuned picture from hopping to quantum coherent transport.\n10. Field-driven phases in a three-dimensional twisted Kitaev model for CoNb$_2$O$_6$: Interplay of frustration and spin-orbit coupling Relevance Score: 3.5731 Authors: Tom Drechsler, Matthias Vojta Link: http://arxiv.org/abs/2604.21973v1 Summary: For CoNb₂O₆ material, we propose a three-dimensional twisted Kitaev model that simultaneously accounts for Kitaev physics and frustrated interchain coupling. Using a zero-temperature semiclassical method under an external magnetic field, we systematically map out the field-driven phase sequence for arbitrary field directions, including commensurate and incommensurate interchain ordered phases. Due to spin-orbit coupling, the phase diagram is highly sensitive to slight variations in the field angle. We further calculate static observables and magnetic excitation spectra for each phase, and correlate the results with existing experimental data, revealing how the interplay between frustration and spin-orbit coupling governs the complex phase behavior under magnetic fields.\n11. Room-temperature third-order nonlinear anomalous Hall effect in ferromagnetic metal Fe3GaTe2 Relevance Score: 3.5414 Authors: Zheng Dai, Shuai Zhang, Jiajun Li, Xiubing Li, Congcong Li, Fengyi Guo, Heng Zhang, Ziqi Wang, Minhao Zhang, Xuefeng Wang, Huaiqiang Wang, Fengqi Song Affiliations: Nanjing Normal University, Nanjing Institute of Atomic Scale Manufacturing, Nanjing University Link: http://arxiv.org/abs/2604.21285v1 Summary: We report the observation of a third-order nonlinear anomalous Hall effect in the ferromagnetic metal Fe3GaTe2 at room temperature. By mechanically exfoliating Fe3GaTe2 flakes and fabricating devices, harmonic responses under AC current excitation were measured using a standard lock-in amplifier, revealing that the third-order anomalous Hall voltage exhibits a cubic dependence on current and is frequency-independent, while the second-order signal is negligible. This third-order nonlinear anomalous Hall effect shows the same hysteretic behavior as the anomalous Hall effect in magnetic field sweeps, with consistent coercive fields, and persists up to the Curie temperature of approximately 350 Kelvin. Temperature-dependent measurements indicate that the third-order nonlinear anomalous Hall resistance decreases rapidly at low temperatures (2-60 K), then increases between 60 and 330 K, peaking near 330 K, before sharply dropping to zero at the Curie temperature. Scaling analysis attributes this effect to an intrinsic contribution from the Berry curvature quadrupole moment rather than extrinsic scattering effects. This work not only provides a method to study magnetic materials via nonlinear electrical transport but also lays the foundation for future development of room-temperature third-order nonlinear electronic devices.\n12. Emergence of a non-bulk hexagonal Fe$_2$S$_2$ single layer via phase transformation Relevance Score: 3.4778 Authors: Affan Safeer, Wejdan Beida, Felix Oberbauer, Nicolae Atodiresei, Gustav Bihlmayer, Max Wolfertz, Chiara Schlichte, Wouter Jolie, Stefan Blügel, Jeison Fischer, Thomas Michely Link: http://arxiv.org/abs/2604.21613v1 Summary: This study reports that a monolayer tetragonal mackinawite (t-Fe2S2) grown on a graphene/Ir(111) substrate undergoes a thermally induced phase transition to a previously unknown hexagonal Fe2S2 monolayer with a β-CuI structure, consisting of a buckled layer formed by two vertically stacked FeS honeycomb lattices. In situ scanning tunneling microscopy and low-energy electron diffraction reveal the transition from a tetragonal to a hexagonal lattice, accompanied by significant changes in morphology and electronic characteristics. This hexagonal Fe2S2 can be reproducibly formed during annealing and represents a new structural motif in the Fe–S material family. First-principles calculations identify the β-CuI structure as the most consistent with experiments and indicate that local Coulomb interactions and magnetic ordering are crucial for understanding the stability of this two-dimensional Fe–S compound. The preferential nucleation of monolayer mackinawite, despite its energetic disadvantage, is inferred to arise from its low edge energy, analogous to the three-dimensional case. These results establish Fe2S2 as a platform for exploring two-dimensional structural polymorphism and demonstrate that reducing dimensionality can stabilize crystal structures unattainable in bulk materials.\n13. Bismuth Films on EuO(111) as a Platform for Proximity-Induced Topological States Relevance Score: 3.4715 Authors: Subham Naskar, Sujit Manna Link: http://arxiv.org/abs/2604.21862v1 Summary: In this work, atomically ordered bilayer bismuth films were successfully epitaxially grown on ferromagnetic insulating EuO(111). High-resolution scanning tunneling microscopy observations reveal the formation of a (012)-oriented quasi-square lattice, corresponding to the stable α-phase bismuthene, with the films exhibiting exceptional flatness, indicative of two-dimensional intrinsic characteristics. Tunneling spectroscopy measurements show a robust energy gap of approximately 400 meV in the local density of states, consistent with a quantum spin Hall insulator that persists even at room temperature. Spatially resolved spectroscopy further detects enhanced edge-localized states at island boundaries. Meanwhile, the proximitized ultrathin bismuth films exhibit linear magnetoresistance and Hall sign reversal in low-temperature magnetotransport, indicating surface-dominated transport driven by quantum confinement. These results achieve the heterointegration of bismuthene with a magnetic insulator, providing an experimental basis for constructing magnetically tunable topological phase platforms, representing a critical step toward the observation of two-dimensional higher-order topological states.\n14. Healing of topological defects while crystallizing nanocrystals Relevance Score: 3.4647 Authors: M. I. Dolz, A. B. Kolton, Y. Fasano Link: http://arxiv.org/abs/2604.21105v1 Summary: This study employs Langevin dynamics simulations to systematically investigate the effects of vortex density, system elasticity, and sample size on crystallization kinetics and low-temperature structural properties under field-cooling conditions, using a nanocrystal composed of hundreds of vortices in a micrometer-sized superconductor as a model system. The simulation results reveal a topological defect healing effect at the edges of the nanocrystal at low temperatures, which is quantitatively consistent with experimental data from Bi2Sr2CaCu2O8+δ micrometer-sized samples. The study demonstrates that the radial distribution of topological defects at low temperatures exhibits a steady-state characteristic, frozen at a temperature below the melting line, with its shape jointly governed by the intrinsic properties of the vortex structure and confinement effects. These findings on the dynamics and spatial distribution of topological defects can be extended to describe the physical properties of generally confined soft condensed matter nanocrystals.\n15. Higher odd-order nonlinear Hall effect in magnetic topological insulator Mn(Bi1-xSbx)2Te4 Relevance Score: 3.4511 Authors: Xiubing Li, Zheng Dai, Shuai Zhang, Heng Zhang, Congcong Li, Boyuan Wei, Fengyi Guo, Chunfeng Li, Fucong Fei, Minhao Zhang, Xuefeng Wang, Huaiqiang Wang, Fengqi Song Affiliations: Suzhou Laboratory, Nanjing Normal University, Nanjing Institute of Atomic Scale Manufacturing, Nanjing University Link: http://arxiv.org/abs/2604.21293v1 Summary: In magnetic topological insulator Mn(Bi₁₋ₓSbₓ)₂Te₄ thin films, high odd-order (third, fifth, and seventh) nonlinear Hall effects were experimentally observed. By applying an AC drive current and measuring harmonic Hall voltages at each order, it was found that these high-order nonlinear Hall voltages exhibit a twofold angular dependence, exist only below the Néel temperature, and peak near the charge neutrality point. Their amplitudes decay exponentially with increasing order and are comparable in samples of different layer thicknesses (odd and even layers). Theoretical analysis suggests that this high odd-order nonlinear Hall response may originate from Berry curvature multipoles. This finding extends the study of nonlinear Hall effects to higher orders and provides an experimental basis for exploring higher-order nonlinear transport phenomena.\n16. $η$-pairing in a two-band model of spinless fermions Relevance Score: 3.3232 Authors: Igor N. Karnaukhov Link: http://arxiv.org/abs/2604.21318v1 Summary: This study proposes a two-band model for spinless fermions, in which itinerant fermions interact with localized fermions via two-particle hybridization. In one dimension, the model can be exactly solved using the Bethe ansatz. The results show that the two-particle hybridization can counteract the repulsive interaction between itinerant fermions, leading to an effective attraction under strong coupling and thereby realizing η pairing of spinless fermions. This pairing mechanism, driven by two-particle hybridization, can give rise to a p-wave superconducting state. The energy of the η-pairing state lies below the bottom of the conduction band, and the pairing condition depends only on the effective attractive interaction, independent of the fermion bandwidth. In the three-dimensional model, strong interactions also induce η pairing, determining the p-type superconducting order. Since η pairing occurs when the filling of itinerant fermions exceeds half-filling, this mechanism may explain high-temperature superconductivity in hole-doped cuprate superconductors and provide a new theoretical perspective on high-temperature superconductivity observed in hydrogen-rich materials under high pressure.\n17. Direct observation of surface bandgap shrinkage and negative electronic compressibility in SrTiO3 Relevance Score: 3.3231 Authors: Warakorn Jindata, Trung-Phuc Vo, Chutchawan Jaisuk, Sung-Kwan Mo, Thanh-Tien Nguyen, Ján Minár, Worawat Meevasana Affiliations: Can Tho University, EQ Tech Energy Company Limited, Suranaree University of Technology, University of West Bohemia in Pilsen, Lawrence Berkeley National Laboratory Link: http://arxiv.org/abs/2604.21783v1 Summary: This study systematically investigates the evolution of surface electronic structures in SrTiO₃ and KTaO₃ under ultraviolet-light-induced electron doping using angle-resolved photoemission spectroscopy (ARPES). In contrast to KTaO₃, SrTiO₃ exhibits a significant band gap shrinkage of approximately 390 meV as the surface electron density increases, accompanied by an anomalous shift of the valence band peak toward lower binding energy by up to 200 meV—a behavior that provides direct spectroscopic evidence for negative electronic compressibility (NEC). Density functional theory calculations qualitatively support the experimental results: surface formation alone reduces the apparent band gap of SrTiO₃, while electron accumulation further drives the system toward a metallic state; the oxygen vacancy model can also induce substantial band gap shrinkage, revealing possible mechanisms underlying the surface band gap reduction. These findings establish a direct spectroscopic link between band gap modulation and the NEC effect on the SrTiO₃ surface, highlighting the potential of SrTiO₃ for next-generation oxide electronic, optoelectronic, and high-performance capacitive energy storage devices.\n18. Generative Discovery of Magnetic Insulators under Competing Physical Constraints Relevance Score: 3.3137 Authors: Qiulin Zeng, Tahiya Chowdhury, Md Shafayat Hossain Link: http://arxiv.org/abs/2604.21073v1 Summary: This paper proposes MagMatLLM, a constraint-guided generative discovery framework based on large language models (LLMs), aimed at addressing the challenge of discovering rare materials such as magnetic insulators that must simultaneously satisfy multiple competing physical constraints—including stability, magnetism, and insulating behavior. The framework integrates LLM-driven crystal generation with evolutionary selection, surrogate screening, and first-principles verification, directly imposing functional constraints during the generation and selection stages to guide the search into sparse regions of material space defined by competing physical conditions, thereby differing from traditional \u0026ldquo;stability-first\u0026rdquo; paradigms that apply constraints only post hoc. The workflow includes LLM-based generation of candidate structures, two-tier screening (basic validity checks and performance evaluation using the CHGNet machine learning model), and multi-objective evolutionary selection. The study identifies 12 previously unreported candidate magnetic insulators, including Tm₄Co₂Cr₂O₁₂ and Cr₄Nb₂O₁₂, of which 10 are confirmed to be dynamically stable via phonon analysis and exhibit finite band gaps and nonzero magnetic moments in spin-polarized density functional theory calculations. This work establishes a transferable multi-objective materials discovery strategy in data-scarce chemical spaces, providing a general paradigm for designing quantum materials under competing constraints.\n19. Nearly Complete Charge\u0026ndash;Spin Conversion via Strain-Eliminated Fermi Pockets in $d$-Wave Altermagnets Relevance Score: 3.3027 Authors: Wancheng Zhang, Zhenhua Zhang, Rui Xiong, Zhihong Lu Affiliations: Hubei Polytechnic University, Wuhan University of Science and Technology, Wuhan University Link: http://arxiv.org/abs/2604.21779v2 Summary: For the d-wave altermagnet KV2Se2O, a theoretical charge-spin conversion efficiency (CSE) of 100% is achievable, but residual elliptical Fermi pockets in actual samples enhance charge conductivity while suppressing spin conductivity, leading to a significant reduction in CSE. This paper proposes systematically eliminating these parasitic pockets via in-plane equibiaxial tensile strain to restore the flat band geometry. First-principles calculations show that CSE increases monotonically with strain, reaching a record value of approximately 96% at 4% strain. An effective tight-binding model fitted to the band structure accurately captures the evolution of the Fermi surface, confirming that the suppression of these pockets—dominated by the weakening of next-nearest-neighbor hopping—is the primary mechanism behind strain-enhanced CSE. Furthermore, unconventional out-of-plane spin current components are found under an out-of-plane electric field, achieving nearly 55% CSE at optimal orientation, offering a new pathway for field-free vertical magnetization switching. This study establishes strain engineering as a practical route toward approaching the conversion limit of d-wave altermagnets, providing design principles for efficient spintronic devices.\n20. Nickel intercalation in epitaxial graphene on SiC(0001): a novel platform for engineering two-dimensional heterostructures Relevance Score: 3.2641 Authors: Ylea Vlamidis, Stiven Forti, Antonio Rossi, Arrigo Calzolari, Carmela Marinelli, Camilla Coletti, Stefan Heun, Stefano Veronesi Link: http://arxiv.org/abs/2604.21739v1 Summary: This study reports a method for achieving controllable nickel intercalation beneath epitaxial graphene on SiC(0001) via a scalable colloidal nanoparticle deposition route: chemically synthesized ~10 nm nickel nanoparticles are uniformly deposited on the graphene surface at room temperature, followed by annealing at 650 °C to drive nickel atom diffusion to the graphene/buffer layer interface, forming ordered single-atom-thick nickel islands whose morphology is tunable by annealing conditions. Scanning tunneling microscopy and angle-resolved photoemission spectroscopy, combined with density functional theory calculations, reveal the atomic and electronic structure of the intercalated nickel islands: the island edges align along the zigzag direction of graphene, correlating with the step orientation of the underlying SiC substrate, and the lattice integrity of graphene is preserved after intercalation. DFT simulations confirm the thermodynamic stability of two-dimensional nickel nanostructures of varying shapes and sizes, predicting a robust average magnetic moment of 0.9 μB per nickel atom. The resulting nickel-intercalated graphene/SiC heterostructures simultaneously retain the graphene band structure and interface ferromagnetism while being stable under ambient conditions. This work establishes a reproducible and scalable route for fabricating magnetic graphene heterostructures, opening new directions for integration into spintronic devices.\n","permalink":"https://nickelates.uk/en/posts/2026-04-23-arxiv-daily/","summary":"\u003cblockquote\u003e\n\u003cp\u003e\u003cstrong\u003eDaily Overview\u003c/strong\u003e:\nToday\u0026rsquo;s highlights focus on an in-depth understanding of the electronic structure of mixed Ruddlesden-Popper nickelates. In [1], X-ray absorption spectroscopy and resonant inelastic X-ray scattering studies on (La,Pr)₃Ni₂O₇₋δ thin films reveal that both strain and oxygen content modulation lead to the delocalization of the oxygen 2p₂ orbital and the nickel 3d₂² orbital, while long-range spin density wave order is significantly suppressed, and short-range magnons remain robust, indicating that orbital delocalization and short-range magnetic fluctuations are prerequisites for superconductivity. [2] provides a theoretical analysis of the 1313-phase La₃Ni₂O₇, pointing out that its superconductivity primarily originates from a three-layer subsystem with s^{±}-wave pairing symmetry, but the single-layer subsystem, acting as a weakly connected layer forming S-N-S Josephson junctions, suppresses the global transition temperature. This work thus deduces that the 2222-phase, rather than the 1313-phase, is the true host of high-temperature superconductivity in the RP-phase La₃Ni₂O₇ family. These two studies deepen the understanding of the superconducting mechanism in nickelates from experimental and theoretical perspectives, respectively.\n\u003cstrong\u003earXiv submission processing window\u003c/strong\u003e: 2026-04-22 20:37 to 2026-04-23 18:00 UTC.\u003c/p\u003e","title":"arXiv Daily: nickelate superconductors 2026-04-23"},{"content":" Daily Overview: The highlight of today’s work focuses on deepening the understanding of the electronic structure of mixed Ruddlesden-Popper nickelates. In [1], a review systematically elaborates on the strong-coupling Hund’s rule-assisted pairing mechanism in bilayer La₃Ni₂O₇, pointing out that the strong interlayer antiferromagnetic exchange mediated by the inner apical oxygen of the 3d_z² orbital cooperates with the itinerant nature of the 3d_x²-y² orbital, forming effective interlayer pairing via Hund’s coupling, which drives extended s-wave superconductivity. Meanwhile, localized ladder singlets give rise to a pseudogap phase, providing a unified theoretical framework for high-temperature superconductivity in this system. Additionally, although several other papers do not directly investigate nickelates, the physical mechanisms they explore are highly relevant to the core issues currently addressed in nickel-based superconductivity. For example, [3] discovers a parity-breaking charge density wave and pairing density wave in kagome metals, offering new perspectives for understanding quantum geometry and pairing symmetry in unconventional superconductors. In [12], perfect spin non-reciprocity is achieved in superconducting alternating magnetic heterostructures, with its momentum-selective filtering strategy inspiring spin transport manipulation in nickel-based heterojunctions. Meanwhile, [7] manipulates van Hove singularities in antimony telluride superlattices via layer-number control, providing a tunable pathway for driving correlated quantum states through dimensionality engineering in nickelates. These advancements collectively deepen the understanding of electron correlations, symmetry, and pairing mechanisms in strongly correlated superconducting systems. arXiv submission processing window: 2026-04-22 00:02 to 2026-04-22 19:31 UTC.\n1. Superconductivity in bilayer La$_3$Ni$_2$O$_7$: A review focusing on the strong-coupling Hund\u0026rsquo;s rule assisted pairing mechanism Relevance Score: 5.3873 Authors: Zhiming Pan, Chen Lu, Fan Yang, Congjun Wu Link: http://arxiv.org/abs/2604.20613v1 Summary: The high-temperature superconductivity in bilayer La₃Ni₂O₇ originates from its unique two-orbital bilayer electronic structure, where the 3d_z² orbital is nearly half-filled and localized, generating strong interlayer antiferromagnetic exchange via the inner apical oxygen 2p_z orbital, while the 3d_x²-y² orbital is approximately quarter-filled and highly itinerant. Under strong coupling, Hund’s rule coupling aligns the spins of the two orbitals on the same nickel site, effectively transferring the interlayer antiferromagnetic exchange to the itinerant 3d_x²-y² orbital, forming an effective coupling J⊥. This mechanism can be simplified into a strong-coupling bilayer t-J-J⊥ model for the 3d_x²-y² band, where J⊥ drives electrons to form interlayer Cooper pairs, realizing extended s-wave pairing superconductivity with high critical temperature. Meanwhile, the strongly localized 3d_z² electrons tend to form interlayer ladder singlets; due to the lack of phase coherence, these singlets do not directly participate in the superconducting condensation but instead give rise to a pseudogap phase. This review systematically elaborates on this strong-coupling Hund’s rule assisted pairing theory, providing a unified framework for understanding the mechanism of high-temperature superconductivity in this system.\n2. Stabilization of a non-superconducting, orthorhombic phase by over-hydrogenating LaFeSiH Relevance Score: 4.1129 Authors: M. F. Hansen, C. Lepoittevin, J. -B. Vaney, P. Boullay, V. Nassif, A. Sulpice, H. Mayaffre, M. -H. Julien, S. Tencé, P. Toulemonde Link: http://arxiv.org/abs/2604.20716v1 Summary: This study achieved overhydrogenation of LaFeSi through high-pressure thermal decomposition of different hydrogen sources (anthracene and ammonia borane). Using anthracene yielded the known tetragonal superconducting phase LaFeSiH (single hydrogen site), while using ammonia borane at a lower temperature synthesized a new orthorhombic overhydrogenated phase LaFeSiH1+x (x ≈ 0.6). Chemical analysis and neutron diffraction identified the existence and occupancy of a second hydrogen site. Unlike metallic LaFeSi and the superconducting tetragonal phase LaFeSiH, orthorhombic LaFeSiH1.6 exhibits semiconductor-like electrical transport behavior rather than superconductivity. Upon heating to approximately 100°C, this orthorhombic phase releases excess hydrogen, undergoes a structural transition back to the tetragonal phase, and recovers superconductivity (LaFeSiH1+δ, with δ much less than 0.6). These results reveal the chemical flexibility of the layered LaFeSiX (X = H, O, F) family and the accessibility of high hydrogen doping, providing a new route for studying superconductivity in iron-based silicides.\n3. Discovery of parity-violating chiral polar-nematic charge density wave and superconductivity in kagome metals Relevance Score: 4.0418 Authors: Xingwei Shi, Geng Li, Zhan Wang, Chuqi Zhang, Ke Zhu, Keyu Zeng, Zikun Tang, Li Huang, Zhen Zhao, Jianping Sun, Xiao Liu, Jin-Guang Cheng, Chengmin Shen, Shu Ping Lau, Kian Ping Loh, Haitao Yang, Xiao Lin, Ziqiang Wang, Hong-Jun Gao Affiliations: Chinese Academy of Sciences, Hefei National Laboratory, University of Chinese Academy of Sciences, Boston College, National University of Singapore, The Hong Kong Polytechnic University Link: http://arxiv.org/abs/2604.20546v1 Summary: Using scanning tunneling microscopy, atomic force microscopy, and optical second harmonic generation, this study directly reveals that the charge density wave state in the kagome metal KV₃Sb₅ spontaneously breaks inversion symmetry within the kagome plane, forming a parity-mixed charge density wave state that simultaneously exhibits ferroelectric dipole moment and nematic quadrupole moment order. The coexistence and coupling of dipole and quadrupole lead to non-collinear ferroelectric polarization and nematic alignment, breaking all mirror symmetries and generating robust electronic chirality in the 3Q charge density wave. Through the coupling of multipole moments with in-plane electric fields, electrical control and manipulation of this chiral polar nematic charge density wave state, including its chirality, can be achieved. Below the superconducting transition temperature, parity-breaking Cooper pair density modulations are observed at both the pristine lattice wave vector and the charge density wave lattice wave vector. These findings provide profound microscopic insights into magnetoelectric and non-reciprocal transport, loop currents, pair density waves, and unconventional superconductivity in kagome metals and related quantum materials.\n4. Disorder-driven coexistence of distinct dynamical states in frustrated Sr$_3$CuNb$_2$O$_9$: a microscopic $μ$SR and $^{93}$Nb NMR study Relevance Score: 3.6640 Authors: M. Biswas, K. Bhattacharya, K. M. Ranjith, S. M. Hossain, S. S. Islam, M. Naskar, R. Sarkar, B. Büchner, T. Shiroka, H. -J. Grafe, M. Majumder Link: http://arxiv.org/abs/2604.20337v1 Summary: Using muon spin relaxation and ⁹³Nb nuclear magnetic resonance (NMR) techniques, a microscopic investigation was conducted on the three-dimensional frustrated magnetic system Sr₃CuNb₂O₉. The zero-field μSR relaxation rate exhibits a power-law divergence with temperature, and the relaxation rate under longitudinal field also displays power-law behavior, consistent with the characteristics of a random singlet (RS) phase. The ⁹³Nb NMR spectra clearly resolve two components with distinct local magnetic environments; the relaxation rate distribution extracted via inverse Laplace transform of the nuclear magnetization recovery reveals two separated relaxation channels: the fast channel shows a T⁰·⁶ power-law temperature dependence, representing an RS-like state, while the slow channel exhibits a T¹·¹ power-law dependence, indicative of quantum spin liquid (QSL)-like behavior. By combining spectroscopic and relaxation data, this work establishes, for the first time, the microscopic coexistence of an RS state and a QSL state in a three-dimensional frustrated magnetic material, shedding light on the mechanism by which disorder and frustration cooperatively stabilize a quantum disordered ground state.\n5. Field-Induced Selective Spin Gap Closure and Quantum Criticality in BaNd$_2$ZnS$_5$ Relevance Score: 3.5433 Authors: Sangyun Lee, A. J. Woods, B. Billingsley, Shengzhi Zhang, R. Movshovich, S. M. Thomas, C. A. Mizzi, B. Maiorov, Shuyi Li, Chunjing Jia, Tai Kong, Eun Sang Choi, Vivien S. Zapf, Minseong Lee Link: http://arxiv.org/abs/2604.20173v1 Summary: In the layered rare-earth magnet BaNd₂ZnS₅, researchers have discovered magnetic-field-induced mode-selective quantum criticality through thermodynamic measurements (including magnetic susceptibility, AC susceptibility, specific heat, magnetocaloric effect, and ultrasonic experiments) combined with theoretical models. Below the Néel temperature, this material exhibits two low-energy spin excitation modes arising from Kramers doublets, corresponding to distinct gaps Δ_L and Δ_H. When a magnetic field is applied along the [110] direction, the lower gap Δ_L continuously softens and closes at a critical field H_c ≈ 2 T, while the higher gap Δ_H remains open, leading to an intermediate partially critical phase. Although the criticality is confined to only part of the excitation modes, thermodynamic measurements reveal a continuous quantum phase transition, with AC susceptibility exhibiting universal scaling behavior (χ_ac ∝ T^{-0.2}) and a finite residual Sommerfeld coefficient γ_0, indicating that only one symmetry sector becomes gapless near the quantum critical point. This phenomenon fundamentally differs from conventional quantum criticality based on global softening of low-energy excitations and is attributed to the selective collapse of Kramers doublet excitations induced by strong anisotropic interactions. These results establish BaNd₂ZnS₅ as a spin-orbit-coupled rare-earth magnet in which quantum criticality is not global but rather mode-selective, with anisotropic interactions allowing distinct excitation sectors to undergo critical behavior independently.\n6. Resonance-enhanced super-superexchange yields giant chiral magnon splitting in rutile altermagnets Relevance Score: 3.4460 Authors: Dai Q. Ho, D. Quang To, Byungkyun Kang, Matthew F. Doty, Garnett W. Bryant, Anderson Janotti Affiliations: University of Delaware Link: http://arxiv.org/abs/2604.20126v1 Summary: By combining hybrid functional first-principles calculations with linear spin-wave theory, the researchers reveal a chiral magnon splitting on the order of meV along specific momentum directions in rutile-phase CuF₂. This splitting originates from the enhancement of the symmetry-allowed seventh-nearest-neighbor exchange difference (J₇b-J₇a), driven by an anomalously strong long-range super-superexchange channel Cu—F⋯F—Cu. Further analysis shows that the energy-level alignment between the Cu 3d_z² and F 2p_z states induces an orbital resonance effect, significantly boosting virtual hopping along this pathway and thereby amplifying the anisotropic long-range exchange interaction, ultimately leading to this substantial chiral magnon splitting. The results establish CuF₂ as an ideal insulating platform for validating altermagnetism in rutile structures and provide both a microscopic mechanism and a feasible descriptor for designing insulating altermagnets with large chiral magnon splitting via orbital energy engineering.\n7. Evolution of the Saddle Point in Antimony Telluride Homologous Superlattices Relevance Score: 3.4188 Authors: Yi-Hsin Shen, Shane Smolenski, Ming Wen, Yimo Hou, Eoghan Downey, Jakob Hammond-Renfro, Katharine Moncrieffe, Chun Lin, Makoto Hashimoto, Donghui Lu, Kai Sun, Dominika Zgid, Emanuel Gull, Pierre Ferdinand P. Poudeu, Na Hyun Jo, Rachel S. Goldman Link: http://arxiv.org/abs/2604.21037v1 Summary: This study systematically investigates the electronic structure of antimony telluride homologue superlattices (Sb₂Te₃)₁(Sb₂)ₙ containing two to four layers of antimonene, using scanning tunneling spectroscopy and angle-resolved photoemission spectroscopy. Combined experimental and self-consistent computational analyses reveal the presence of a saddle point and its associated van Hove singularity near the M point, which shifts toward the Fermi level as the number of antimonene layers increases. Atomic orbital contribution analysis identifies the hybridization of Sb and Te p_z orbitals as the key mechanism driving the energy shift of the van Hove singularity. These findings confirm theoretical predictions and demonstrate a new approach for aligning the Fermi level with band extrema through layer-number engineering, laying the groundwork for generating correlated quantum matter in topological insulator/topological semimetal superlattices.\n8. Anisotropic multiband magnetotransport in LaAg$_2$Ge$_2$ thin films Relevance Score: 3.3418 Authors: Mizuki Ohno, Reiley Dorrian, Veronica Show, Joseph Falson Affiliations: California Institute of Technology Link: http://arxiv.org/abs/2604.20709v1 Summary: LaAg₂Ge₂ thin films were grown on MgO(001) substrates by molecular beam epitaxy, and their magnetotransport properties were systematically investigated. The Hall effect and magnetoresistance data can be well described by an effective two-carrier model incorporating one high-mobility electron band, yielding a positive magnetoresistance of 22.5% at 9 T. The angle-dependent magnetoresistance exhibits a dominant twofold symmetry, with repeatable valley/peak features at specific tilt angles that are nearly independent of magnetic field and temperature. These results deepen the understanding of anisotropic electronic transport in ThCr₂Si₂-type germanide thin films.\n9. Domain-Wall-Mediated Ultralow-Barrier Sliding and Pinning in Ferroelectric Moiré Superlattices Revealed by Machine Learning Relevance Score: 3.3159 Authors: Jia-Wen Li, Sheng Meng, Xinghua Shi, Jin Zhang, Wei-Hai Fang Link: http://arxiv.org/abs/2604.20277v1 Summary: Using machine learning molecular dynamics simulations, this study reveals thermally driven spontaneous interlayer sliding in ferroelectric MoS₂ moiré superlattices, with a relative velocity of approximately 1 m/s at 300 K. Unlike rigid layer translation, this sliding manifests as a global drift of the moiré pattern, which contradicts the rigid sliding barrier on the order of meV/atom. When full atomic relaxation is allowed with only interlayer displacement constrained, sliding proceeds along a nearly barrier-free path, with a barrier nearly two orders of magnitude lower than that of the rigid path, and directly reproduces the global drift of the moiré pattern. Further analysis shows that this ultralow-barrier sliding is dominated by a collective reconstruction mechanism mediated by domain walls, rather than synchronous translation of rigid layers. Additionally, sulfur vacancies induce a transition from sliding to pinning; a mere 0.1% sulfur vacancy concentration is sufficient to convert long-range sliding into localized oscillations. Notably, these phenomena are not limited to small twist angles but are universally present in twist-induced multidomain structures. This study reveals the domain-wall-mediated ultralow-barrier sliding pathway in moiré superlattices, deepening the understanding of the microscopic dynamics of sliding ferroelectrics.\n10. Symmetry-dictated switching of antiferromagnetic magnon transport in 2D multiferroics Relevance Score: 3.3054 Authors: Yibo Liu, Jiale Wang, Jiexiang Wang, Ying Dai, Baibiao Huang, Xinru Li, Yandong Ma Affiliations: Shandong University Link: http://arxiv.org/abs/2604.20064v1 Summary: This study proposes a universal mechanism for nonvolatile switching of antiferromagnetic magnon transport via ferroelectric polarization in two-dimensional multiferroic materials. The core idea is to couple the magnon geometric phase with sublattice asymmetry in ferroelectric-induced exchange interactions and Dzyaloshinskii-Moriya interactions, thereby breaking the exact compensation of inherently opposite-chirality magnons in collinear antiferromagnets, lifting spin degeneracy, and generating a highly tunable net Berry curvature. The key finding is that flipping the ferroelectric polarization deterministically swaps these magnetic asymmetries, leading to a complete reversal of the net magnon Berry curvature and the resulting anomalous thermal Hall conductivity. Using first-principles calculations and linear spin-wave theory, the authors rigorously validate this geometric-phase-driven mechanism in monolayer CuCr₂Se₄, establishing a robust paradigm for coupling multiferroicity with magnon geometric phases and laying the foundation for nonvolatile, electrically controlled antiferromagnetic magnonic devices.\n11. Symplectic connection third-order Hall effect in a room-temperature ferromagnet Relevance Score: 3.2444 Authors: Yu Cao, Xukun Feng, Yiming Guo, Huiying Liu, Qia Shen, Hongliang Chen, Wanxi Gong, Yu Yang, Dandan Guan, Yaoyi Li, Shiyong Wang, Hao Zheng, Canhua Liu, Xiaoxue Liu, Yumeng Yang, Xuepeng Qiu, Ruidan Zhong, Jinfeng Jia, Shengyuan A. Yang, Cong Xiao, Liang Liu Affiliations: Beihang University, Fudan University, Shanghai Jiao Tong University, ShanghaiTech University, The Hong Kong Polytechnic University, Tongji University Link: http://arxiv.org/abs/2604.20356v1 Summary: In the room-temperature van der Waals ferromagnet Fe₃GaTe₂, researchers have discovered a novel third-order nonlinear Hall effect (THE) originating from the second-order Berry connection polarizability, reflecting a higher-order band geometric property known as the symplectic connection. Experimental results show that this third-order transverse response exhibits odd symmetry with respect to the magnetization direction, vanishes above the Curie temperature, and is independent of the driving current direction. Through scaling-law analysis and first-principles calculations, the response is confirmed to be a symplectic connection-induced THE. This discovery achieves the first experimental detection of the symplectic connection, surpassing previous low-order quantum geometric studies limited to quantum metrics and Berry curvature, and opens a new avenue for exploring higher-order quantum geometric properties via nonlinear transport. It also reveals the potential for investigating nonlinear Hall effects in a broad class of magnets with inversion symmetry. Moreover, the ability to manipulate this effect at room temperature offers possibilities for device applications based on quantum geometric connection structures.\n12. Perfect spin nonreciprocity in gated superconducting altermagnetic heterostructures Relevance Score: 3.2361 Authors: Pei-Hao Fu, Jun-Feng Liu, Luca Chirolli, Jorge Cayao Link: http://arxiv.org/abs/2604.20312v1 Summary: This study constructs a superconducting alternating magnet heterostructure, wherein a finite normal region regulated by gate voltage is introduced between the superconducting alternating magnet and a metallic reservoir, enabling selective filtering of transverse momentum channels. This filtering mechanism aligns the transmission channels with the momentum-dependent spin-split states in the alternating magnet, thereby generating a perfectly nonreciprocal spin-polarized current. The findings reveal that this nonreciprocity manifests in both local and nonlocal spin currents, with its polarity highly tunable by gate voltage and a near-unity quality factor. Additionally, local and nonlocal charge currents exhibit similar nonreciprocal behavior, also achieving a perfect quality factor. Both spin and charge currents are sensitive to variations in the alternating magnetic field strength, a feature that can be utilized to identify the type of alternating magnet. This work provides a feasible route for electrically controlled nonreciprocal superconducting spintronic devices based on alternating magnets.\n13. Giant spontaneous Kerr effect reveals the defect origin of macroscopic time-reversal symmetry breaking in altermagnetic MnTe Relevance Score: 3.2053 Authors: Weitung Yang, Choongjae Won, Cory Cress, Marshall Zachary Franklin, Xiaochen Fang, Shelby Fields, Nicholas Combs, Shaofeng Han, Weihang Lu, Steven P. Bennett, Sang-Wook Cheong, Jing Xia Affiliations: University of California, Irvine, U.S. Naval Research Laboratory, Pohang University of Science and Technology, Rutgers University Link: http://arxiv.org/abs/2604.21021v2 Summary: This study reports the observation of a large spontaneous Kerr rotation of up to ±1500 microradians in α-MnTe single crystals using a fiber-based Sagnac interferometric microscope operating at the telecommunication wavelength of 1550 nm. The signal emerges precisely at the Néel temperature of 307 K and forms micrometer-scale opposite-chirality domains. The application of a weak external magnetic field effectively trains the domain chirality, and a temperature-driven chirality reversal is observed during heating. In stark contrast, no spontaneous Kerr signal is detected in stoichiometric insulating α-MnTe thin films across the entire temperature range. By comparing bulk single crystals with thin films and correlating resistivity with doping levels, the study clearly demonstrates that the macroscopic magneto-optical response does not originate from ideal alternating magnetic order, but is instead activated by naturally occurring hole self-doping (e.g., manganese vacancies and other defects) in the material. This finding reveals that defect-induced carriers, rather than the ideal alternating magnetic structure, are the true origin of macroscopic time-reversal symmetry breaking, and confirms that telecommunication-wavelength Kerr imaging can serve as a practical and sensitive readout method in alternating magnetic spintronics.\n14. Crystal structure prediction with nuclear quantum and finite-temperature effects via deep free energy learning Relevance Score: 3.1929 Authors: Xiaoyang Wang, Yinan Wang, Wenbo Zhao, Hanyu Liu, Hao Xie, Lei Wang, Han Wang Affiliations: Artificial Intelligence for Science Institute, Chinese Academy of Sciences, École Polytechnique Fédérale de Lausanne (EPFL), Peking University, Institute of Applied Physics and Computational Mathematics, Jilin University Link: http://arxiv.org/abs/2604.20230v1 Summary: The deep free-energy model is constructed through a two-level parallel learning workflow, directly treating the self-consistent harmonic approximation (SCHA) free-energy surface as a function with the same mathematical structure as the potential energy surface, which is learned using a deep neural network potential. The model can simultaneously output free energy, forces, and stresses in a single forward propagation. Applied to the La–Sc–H system at 200 GPa and 300 K, crystal structure prediction based on the deep free energy not only reproduces the stability of experimentally known LaH₁₀ and LaSc₂H₂₄ but also uncovers a previously unreported thermodynamically stable clathrate hydride, P4/mmm LaScH₈. For the LaH₁₀ system, the model achieves a cost reduction of 1.72×10⁶ times compared to density functional theory-level stochastic self-consistent harmonic approximation. The deep free-energy framework provides a scalable route for effectively incorporating finite-temperature and nuclear quantum effects in high-throughput crystal structure prediction.\n15. Fluctuation-driven multi-step charge density wave transition in monolayer TiSe$_2$ Relevance Score: 3.1539 Authors: Luka Benić, Dino Novko, Ivor Lončarić Link: http://arxiv.org/abs/2604.20355v1 Summary: This study employs large-scale molecular dynamics simulations of monolayer TiSe₂ using a machine-learned interatomic potential trained on first-principles data, revealing the microscopic mechanism of its charge density wave (CDW) phase transition. It is found that CDW melting does not follow a conventional second-order transition but proceeds via a two-step process: an extended fluctuation region over a broad temperature range from approximately 200 K to 250 K, accompanied by proliferation of topological defects and domain walls, along with a fully overdamped soft optical phonon mode. Furthermore, anisotropic long-wavelength thermal fluctuations spontaneously stabilize a non-symmetric 3Q chiral CDW order with C2 symmetry, which is broken at around 150 K. The simulated transition temperatures are consistent with experimental observations. The study also shows that thermal fluctuations and electron-phonon coupling alone are sufficient to accurately describe the CDW dynamics of TiSe₂, without invoking excitonic correlations. This work provides a unified microscopic framework for understanding fluctuation-driven complex phase transitions in two-dimensional quantum materials.\n16. Strain effects in [001] textured Co80Ir20 thin films with negative magnetocrystalline anisotropy Relevance Score: 3.1038 Authors: L. Aviles Felix, M. Vasquez Mansilla, J. E. Gomez, M. Balod, J. Padilla, J. Santiso, Subhakanta Das, S. N. Piramanayagam, A. Butera Link: http://arxiv.org/abs/2604.20645v1 Summary: The study systematically analyzed the effects of different underlayers (Ta, Pt) and capping layers on strain and magnetic anisotropy in 24 nm thick [001]-textured Co80Ir20 films using X-ray diffraction, magnetometry, and ferromagnetic resonance. The results show that the underlayer material significantly affects the c-axis lattice parameter (Ta induces larger negative strain), while the degree of texture and grain size remain largely constant (except for one multilayer). Magnetically, the anisotropy of films with Ta underlayers is close to shape anisotropy, while Pt underlayers introduce an additional in-plane anisotropy field of approximately 7–9 kOe. A simple model of stress-induced anisotropy agrees well with experimental values. The study indicates that due to the observed correlation between strain and anisotropy and the similar microstructural properties, stress effects cannot be ignored when analyzing magnetic data to evaluate magnetocrystalline anisotropy contributions.\n17. Layer-mediated tuning of spin and valley physics in stacked tetragonal altermagnetic bilayers Relevance Score: 3.0655 Authors: Jianke Tian, Xiaowen Zhou, Gui-Bin Liu Affiliations: Beijing Institute of Technology Link: http://arxiv.org/abs/2604.20162v1 Summary: Based on first-principles calculations and symmetry analysis, this work reveals that in a bilayer system composed of two tetragonal alternating magnetic monolayers, the layer stacking enforces symmetry constraints on spin and valley degrees of freedom, enabling their manipulation through interlayer sliding and external electric fields. It is found that [C2||P] and [C2||Mz] symmetries enforce spin degeneracy, while the coupling between spin and layer degrees of freedom provides a general framework for electric-field control of spin states; appropriate interlayer sliding can break the [C2||Md] symmetry, thereby inducing spontaneous valley splitting and driving the system toward a fully compensated ferromagnetic state. Moreover, the interlayer-sliding-induced tunable valley splitting can enhance tunneling magnetoresistance. This work emphasizes the intrinsic correlations among spin, valley, and layer degrees of freedom, offering symmetry-based design principles for layer-structured spintronic and valleytronic devices.\n18. Engineering Wake-Up-Free Ferroelectric Capacitors with Enhanced High-Temperature Reliability Relevance Score: 3.0211 Authors: Nashrah Afroze, Salma Soliman, Yu-Hsin Kuo, Sanghyun Kang, Mengkun Tian, Priyankka Ravikumar, Andrea Padovani, Asif Khan Link: http://arxiv.org/abs/2604.20698v1 Summary: This paper systematically investigates the high-temperature reliability of hafnium zirconium oxide (HZO) ferroelectric capacitors fabricated via thermal atomic layer deposition (Th-ALD) and plasma-enhanced atomic layer deposition (PE-ALD) using tungsten (W) and titanium nitride (TiN) as bottom electrodes. Experimental results show that on the W bottom electrode, PE-ALD HZO capacitors exhibit polarization switching characteristics without wake-up effects at temperatures up to 125°C, and demonstrate significantly superior endurance compared to Th-ALD devices in the 85–125°C range. By isolating the naturally formed tungsten oxide interfacial layer (WOx) during the PE-ALD process from the effect of the PE-ALD film itself, it is confirmed that WOx is the primary factor enhancing high-temperature endurance and suppressing the wake-up effect, while the PE-ALD film itself contributes only secondarily to wake-up reduction. In contrast, on the TiN bottom electrode, PE-ALD HZO capacitors do not improve wake-up behavior or endurance; instead, they exhibit polarization degradation due to the formation of a TiOxNy interfacial layer, as oxidized TiN cannot effectively enhance endurance or suppress wake-up like oxidized W. The findings indicate that PE-ALD HZO achieves superior high-temperature ferroelectric performance only with the W bottom electrode, whereas Th-ALD HZO remains a reliable high-temperature option on the TiN bottom electrode, providing guidance for thermal reliability design in three-dimensional monolithic integration of ferroelectric memories.\n19. Polaron transport and Verwey transition in magnetite Relevance Score: 3.0083 Authors: Nikita Fominykh, Vladimir Stegailov Link: http://arxiv.org/abs/2604.20642v1 Summary: This study directly simulates the coupling between polarons and lattice vibrations in magnetite by combining kinetic Monte Carlo (kMC) and first-principles molecular dynamics (MD) within an ab initio framework, aiming to elucidate the Verwey transition mechanism that has remained unresolved for nearly a century. Contrary to the Ihle-Lorentz small polaron model, the calculations reveal no significant change in the band structure near the transition temperature, but instead observe thermally activated hopping behavior of trimers. The DC conductivity derived from this model agrees well with experimental data on both the low- and high-temperature sides. The study proposes that the essence of the Verwey transition lies in a shift from non-adiabatic polaron hopping under a frozen trimeron ordered state at low temperatures to adiabatic hopping after the destruction of trimeron order at high temperatures, accompanied by a marked reduction in activation energy. These results underscore the critical role of electron–lattice coupling and the connection between the destruction of trimeron order and the adiabatization of the hopping process, offering a first-principles-based perspective on the Verwey transition.\n","permalink":"https://nickelates.uk/en/posts/2026-04-22-arxiv-daily/","summary":"\u003cblockquote\u003e\n\u003cp\u003e\u003cstrong\u003eDaily Overview\u003c/strong\u003e:\nThe highlight of today’s work focuses on deepening the understanding of the electronic structure of mixed Ruddlesden-Popper nickelates. In [1], a review systematically elaborates on the strong-coupling Hund’s rule-assisted pairing mechanism in bilayer La₃Ni₂O₇, pointing out that the strong interlayer antiferromagnetic exchange mediated by the inner apical oxygen of the 3d_z² orbital cooperates with the itinerant nature of the 3d_x²-y² orbital, forming effective interlayer pairing via Hund’s coupling, which drives extended s-wave superconductivity. Meanwhile, localized ladder singlets give rise to a pseudogap phase, providing a unified theoretical framework for high-temperature superconductivity in this system. Additionally, although several other papers do not directly investigate nickelates, the physical mechanisms they explore are highly relevant to the core issues currently addressed in nickel-based superconductivity. For example, [3] discovers a parity-breaking charge density wave and pairing density wave in kagome metals, offering new perspectives for understanding quantum geometry and pairing symmetry in unconventional superconductors. In [12], perfect spin non-reciprocity is achieved in superconducting alternating magnetic heterostructures, with its momentum-selective filtering strategy inspiring spin transport manipulation in nickel-based heterojunctions. Meanwhile, [7] manipulates van Hove singularities in antimony telluride superlattices via layer-number control, providing a tunable pathway for driving correlated quantum states through dimensionality engineering in nickelates. These advancements collectively deepen the understanding of electron correlations, symmetry, and pairing mechanisms in strongly correlated superconducting systems.\n\u003cstrong\u003earXiv submission processing window\u003c/strong\u003e: 2026-04-22 00:02 to 2026-04-22 19:31 UTC.\u003c/p\u003e","title":"arXiv Daily: nickelate superconductors 2026-04-22"},{"content":" Daily Overview: Greetings readers, welcome to today\u0026rsquo;s overview of papers in the nickel-based superconductivity field. Although no works directly targeting nickelates as the research subject are included today, multiple papers focus on physical mechanisms closely related to the core issues of nickel-based superconductivity. Among them, [1] decomposes the pseudogap in cuprates via nuclear magnetic resonance shift, proposing three condensation rules for spin-singlet pairing, thereby providing a unified framework for understanding the electronic phase diagram of layered oxide superconductors. [13], based on real-space Ginzburg-Landau analysis, explores the inversion symmetry breaking and chirality induced by four-layer charge density waves in the Kagome superconductor CsV₃Sb₅, with conclusions that are relevant to similar possible CDW order in nickelates. [20] introduces hidden hyperuniform disorder into the Hubbard model, revealing the high sensitivity of electronic states and magnetic phase transitions in correlated systems to ordered microstructures, offering new insights into the regulation of disorder effects in nickelates. arXiv submission processing window: 2026-04-20 20:00 to 2026-04-21 18:14 UTC.\n1. Pseudogap and Condensation in Cuprate Superconductors from NMR Shifts Relevance Score: 4.2485 Authors: Abigail Lee, Juergen Haase Link: http://arxiv.org/abs/2604.19215v1 Summary: Based on the symmetry of the copper nuclear hyperfine coupling (anisotropic A component and isotropic B component), this paper decomposes the nuclear magnetic resonance shift of copper oxide high-temperature superconductors into two independent electronic spin components. The study finds that, under different doping levels, the metallic B-spin emerges above the pseudogap temperature and coexists with the A-spin; as doping increases, the pseudogap temperature decreases, the density of states of the B-spin increases linearly, and above x ≈ 0.20 the rate of increase nearly triples, at which point the pseudogap disappears and both A and B behave as superconducting metals (disappearing rapidly at Tc). The pseudogap temperature reflects the coupling between A and B, which suppresses the shift but does not affect nuclear relaxation. Spin singlet pairing follows three condensation rules, where a specific matching of A and B determines the optimal Tc, but the highest Tc is not determined by the shift but is related to nuclear relaxation and charge sharing between planar copper and oxygen. This phenomenology provides a unified framework for understanding the electronic phase diagram of cuprate superconductors.\n2. Unveiling the Superconducting Ground State of Heusler alloy Pd2ZrIn via muon spin relaxation and rotation measurement Relevance Score: 4.0374 Authors: Kavita Yadav, Anoop M Divakaran, Jumpei G. Nakamura, Tsunehiro Takeuchi, K. Mukherjee Affiliations: Indian Institute of Technology Mandi, Toyota Technological Institute, University of Delhi, High Energy Accelerator Research Organization (KEK) Link: http://arxiv.org/abs/2604.19283v1 Summary: Through zero-field and transverse-field muon spin relaxation/rotation (μSR) measurements, combined with macroscopic physical property characterizations including resistivity, magnetic susceptibility, and specific heat, the superconducting ground state of the full Heusler alloy Pd₂ZrIn has been systematically investigated. This alloy crystallizes in a cubic L2₁ structure with significant B2-type anti-site disorder. Resistivity and magnetic susceptibility measurements confirm it as a bulk type-II superconductor with a superconducting transition temperature T_C ≈ 2.2 K. Zero-field μSR results reveal no detectable spontaneous internal magnetic field below T_C, indicating the preservation of time-reversal symmetry. Transverse-field μSR spectra confirm the formation of a vortex lattice, consistent with type-II superconductivity; the temperature dependence of the superfluid density is perfectly described by a fully gapped s-wave state without nodes, with a superconducting gap Δ(0) = 0.33 ± 0.01 meV. Moreover, the ratio of T_C to the Fermi temperature (T_C/T_F) falls within the conventional superconductivity region of the Uemura plot. Collectively, these results establish Pd₂ZrIn as a weak-coupling, dirty-limit type-II superconductor with a fully gapped, nodeless order parameter and unbroken time-reversal symmetry.\n3. Competing Constraints on Superconductivity in Thick FeSe films Relevance Score: 3.9298 Authors: Ya-Xun He, Xing-Jian Liu, Qun Wang, Ting Chen, Hassan Ali, Jia-Ying Zhang, Bao-Juan Kang, Zheng Zhang, Jun-Yi Ge Affiliations: Shanghai University, Shanghai Maritime University Link: http://arxiv.org/abs/2604.19443v1 Summary: This study addresses the challenge of optimizing multiple growth parameters in thick FeSe superconducting thin films, which are mutually constrained, by developing a high-throughput off-axis pulsed laser deposition strategy. Utilizing the inherent lateral inhomogeneity of the plasma plume, a combinatorial FeSe thin-film library with continuous gradients in lattice parameters, composition, and defects was constructed. Systematic characterization of 80 films with thicknesses exceeding 50 nanometers, combined with interpretable machine learning analysis, revealed that the maximum superconducting transition temperature does not always occur at the plume center but can shift to off-axis positions, uncovering a competition among c-axis lattice expansion, stoichiometry, and defect scattering. The results indicate that although the c-axis lattice parameter is strongly correlated with (T_c), stoichiometry and defect scattering impose critical constraints on the achievable high transition temperatures, defining a narrow optimization window rather than a simple monotonic relationship. Based on this framework, an onset transition temperature of 17.1 K was achieved in thick FeSe films, and a general methodology combining combinatorial synthesis with machine learning was established to uncover constrained optimization landscapes in complex functional materials.\n4. Optical conductivity of topological semimetal Nb$_{2n+1}$Si$_n$Te$_{4n+2}$ Relevance Score: 3.7386 Authors: Seongjin Ahn Link: http://arxiv.org/abs/2604.19166v1 Summary: Using the Dirac Su-Schrieffer-Heeger model and Kubo formula, this paper systematically investigates the linear optical conductivity of the quasi-one-dimensional nodal line topological semimetal family Nb₂ₙ₊₁SiₙTe₄ₙ₊₂. At zero temperature, the Drude weight exhibits pronounced anisotropy: along the nodal line direction, it takes a finite value at the charge neutrality point (inheriting properties of one-dimensional Dirac fermions), while the transverse Drude weight vanishes quadratically with the Fermi energy. In contrast, the interband optical conductivity shows linear frequency dependence in both longitudinal and transverse directions at low frequencies, with only the slope varying by direction—a behavior distinctly different from that of two-dimensional symmetry-enforced nodal line semimetals (no interband transitions) and three-dimensional nodal ring semimetals (constant axial, linear radial dependence), constituting a unique optical signature of this asymmetric nodal line system. Finite-temperature corrections to the intraband and interband optical conductivity are further analyzed, demonstrating that zero-temperature results remain valid within experimentally relevant temperature ranges. Moreover, the derivative of the Drude weight exhibits a kink at the Fermi energy corresponding to the topological transition of the Fermi surface (open to closed), while doping opens a clear optical gap in the interband conductivity via Pauli blocking. These results provide qualitative and quantitative guidance for experimental detection of this family of materials.\n5. From Entropy to Compression: Competing Thermodynamic Drivers of Structural Transitions in Transition Metals Relevance Score: 3.6885 Authors: S. Azadi, S. M. Vinko, A. Principi, T. D. Kuehne, M. S. Bahramy Link: http://arxiv.org/abs/2604.19222v2 Summary: Using finite-temperature density functional theory, this study constructs pressure-temperature phase diagrams for 15 transition metals with hcp, fcc, and bcc ground-state structures, systematically revealing the evolution of structural stability under electronic excitation. The results indicate that as electron temperature increases, structural diversity systematically decreases, with the fcc phase gradually dominating stability, the hcp phase persisting as a secondary phase, and the bcc phase being progressively suppressed. At high temperatures, the fcc phase is generally more stable, while the bcc phase is primarily stabilized through compression, leading to material-dependent competition across the periodic table. These findings provide a unified framework for understanding structural transitions in electronically excited metals and emphasize the necessity of simultaneously considering electronic excitation and pressure effects when describing phase stability away from equilibrium.\n6. Observation of field-odd and field-free superconducting diode effects in $\\mathrm{Mo}_2\\mathrm{C}$ nanoflakes Relevance Score: 3.6367 Authors: Wei Gao, Kaixuan Fan, Menghan Li, Jinhao Cheng, Peng Zhu, Qing Zhang, Shuaishuai Ding, Wenping Hu, Fan Yang, Dechao Geng, Hechen Ren Link: http://arxiv.org/abs/2604.19525v2 Summary: In nominally centrosymmetric molybdenum carbide (Mo₂C) nanoplates grown by chemical vapor deposition, micro-ribbons were fabricated for transport measurements, enabling the first simultaneous observation of both field-odd and field-independent superconducting diode effects (SDE). For the field-odd SDE, with an in-plane magnetic field perpendicular to the current, the diode efficiency exceeded 40% at 4 K, and its polarity reversed upon flipping the field direction; in contrast, the field-independent SDE persisted stably in another device after zero-field cooling, with its polarity unchanged by out-of-plane magnetic fields, indicating its intrinsic nature. After excluding extrinsic mechanisms such as edge asymmetry and vortex trapping, it is proposed that domain wall supercurrents or charge-density-wave-like order induce unexpected symmetry breaking in the material, simultaneously lifting spatial inversion and time-reversal symmetries. This work establishes robust Mo₂C as an ideal platform for nonreciprocal superconducting electronics operating at liquid helium temperatures and opens new avenues for exploring SDE in nominally centrosymmetric superconductors.\n7. Stripping Symmetry: Electrochemical Oxidation to a Superconducting Polar Metal in Au2Pb0.914P2 Relevance Score: 3.6322 Authors: Scott B. Lee, Stephanie R. Dulovic, Joseph W. Stiles, Xin Zhang, Fatmagül Katmer, Sudipta Chatterjee, Jaime Moya, Allana G. Iwanicki, Abby N. Neill, Chris Lygouras, Tieyan Chang, Tyrel M. McQueen, Yu-Sheng Chen, Leslie M. Schoop Affiliations: The University of Chicago, The Johns Hopkins University, Princeton University Link: http://arxiv.org/abs/2604.18843v1 Summary: Here, we successfully synthesized the polar metal Au₂Pb₀.₉₁₄P₂ by selectively removing Pb atoms from the centrosymmetric parent compound Au₂PbP₂ via an electrochemical topochemical deintercalation method. This approach leverages the synergistic effect of the second-order Jahn-Teller effect and stereochemically active lone pairs to drive structural symmetry breaking, locking the product into the noncentrosymmetric superspace group Ama2(01γ)ss0. The (3+1)-dimensional modulated structure was resolved using synchrotron single-crystal X-ray diffraction, and the polar nature was confirmed through nonlinear electronic transport experiments. Below 1.52 K, this material transforms into a type-II superconductor, with both heat capacity and AC magnetic susceptibility exhibiting power-law behavior, indicating that the superconducting gap structure is modulated by inversion symmetry breaking. This work establishes electrochemical oxidation as a rational synthetic pathway for preparing metastable noncentrosymmetric superconductors via chemically directed symmetry breaking.\n8. Re-examination of electronic structure of dilute Kondo transition-metal ions substituted into a Heavy Fermion compound Relevance Score: 3.5948 Authors: Kou Takubo, Shintaro Suzuki, Kohei Yamamoto, Kohei Yamagami, Masafumi Horio, Toshiaki Ina, Kiyohumi Nitta, Masaichiro Mizumaki, Eiji Ikenaga, Yosuke Matsumoto, Hiroki Wadati, Satoru Nakatsuji Link: http://arxiv.org/abs/2604.19078v1 Summary: We performed a site-selective study of the electronic structure at Mn sites in the heavy-fermion compound α-(Yb,Lu)(Al₁₋ₓMnₓ)B₄ using X-ray absorption spectroscopy (XAS) and hard X-ray photoelectron spectroscopy (HAXPES). Mn 2p XAS reveals clear multiplet structures, indicating that the unoccupied states are correlated high-spin Mn²⁺, despite magnetic measurements showing that the Mn sites are nonmagnetic—this contradiction confirms the existence of an effective ligand field between local Mn 3d and surrounding B 2p, serving as a spectroscopic manifestation of the Kondo effect. In contrast, Mn 2p HAXPES shows no multiplet or charge-transfer satellite peaks, suggesting that the occupied Mn²⁺ 3d electrons are itinerant and exhibit nonlocal screening, arising from Kondo-like correlations with the conduction band B 2p and the Yb 4f/5d bands below the Fermi level. This particle–hole asymmetry prompts a reexamination of correlation and screening effects in core-level spectroscopy.\n9. Room-temperature multistage metastability in a moiré superstructure Relevance Score: 3.5822 Authors: B. Q. Lv, Yifan Su, Alfred Zong, Karna Morey, Bryan T. Fichera, Qiaomei Liu, Dong Wu, Yongchang Ma, Dupeng Zhang, Faran Zhou, Makoto Hashimoto, Dong-Hui Lu, Donald A. Walko, Haidan Wen, Jiarui Li, Suchismita Sarker, Jacob P. C. Ruff, N. L. Wang, Nuh Gedik Link: http://arxiv.org/abs/2604.18998v1 Summary: In the bulk material EuTe₄, which naturally hosts a moiré superlattice formed by stacking incommensurate monolayer and bilayer charge density waves, researchers have achieved nonvolatile metastable states at room temperature via electrical driving. Systematic transport measurements reveal discrete resistance plateaus and strong electric field sensitivity, enabling the induction of numerous metastable states within a wide temperature window inside a giant thermal hysteresis loop, suitable for high-temperature multibit memory. Combining photoemission spectroscopy, X-ray diffraction, and in-situ transport measurements, it is found that these metastable states do not originate from the emergence of new ordered phases or changes in incommensurate periodicity, but rather manifest as suppression of the pristine charge density wave amplitude and reduction of correlation length, pointing to a unique switching of the out-of-plane charge density wave phase in the electric-field-induced moiré superstructure. This study not only provides key insights into metastable phenomena in moiré systems with stacked electronic order, but also establishes EuTe₄ as a promising platform for developing room-temperature multibit memory.\n10. Dynamical magnetism in the disordered cubic lattice material $γ$-${\\rm Ba}_{3}{\\rm CoNb}_{2}{\\rm O}_{9}$ Relevance Score: 3.5565 Authors: Fanjun Xu, Ralf Feyerherm, Cecilie Glittum, Thomas J. Hicken, Hubertus Luetkens, Jonas A. Krieger, Cintli Aguilar-Maldonado, Sven Luther, Lucy K. Saunders, Clemens Ritter, Peter Fouquet, Margarita Russina, Karel Prokes, A. T. M. Nazmul Islam, Bella Lake Link: http://arxiv.org/abs/2604.18794v1 Summary: γ‑Ba₃CoNb₂O₉ is a disordered simple cubic spin‑1/2 lattice material in which Co²⁺ ions randomly occupy one‑third of the lattice sites, bringing the system close to the site‑percolation threshold for magnetic order. Measurements including specific heat, magnetic susceptibility, neutron spin echo, and muon spin rotation reveal a broad thermodynamic crossover, short‑range magnetic correlations, and fast spin dynamics persisting down to at least 0.1 K, with no evidence of static order or conventional spin‑glass freezing. Monte Carlo simulations show a broad distribution of orphan spins, finite clusters, and an infinite network; the calculated proportion of orphan spins (≈8.8%) agrees well with the fraction of weakly correlated spins obtained from magnetization fitting (≈8.2%). Exact diagonalization of the diluted S=1/2 Heisenberg model successfully reproduces the broadened magnetic specific‑heat anomaly and confirms the coexistence of weakly and strongly correlated spin environments. These findings indicate that in a three‑dimensional dilute magnet, spin‑1/2 quantum fluctuations, together with dilution effects and the proximity to the percolation threshold, drive a short‑range correlated dynamic magnetic state distinct from both classical spin glasses and geometrically frustrated quantum spin liquids.\n11. Atomic-scale origin of charge density wave-driven metal-semiconductor transition in an incommensurately modulated metal-organic framework Relevance Score: 3.5453 Authors: Ling Zhang, Zeyue Zhang, Liu He, Bin Jiang, Yingchao Wang, Jiaxiang Zhang, Huimin Qi, Chao Zhang, Jinkun Guo, Hao Chen, Yunlong Fan, Yanran Shen, Hongli Jia, Guobao Li, Yu-Qing Zheng, Julius J. Oppenheim, Tianyang Chen, Jian Wang, Lei Sun, Junliang Sun, Jin-Hu Dou Affiliations: Princeton University, The Chinese University of Hong Kong (Shenzhen), Westlake Institute for Advanced Study, Westlake University, Peking University Link: http://arxiv.org/abs/2604.19640v1 Summary: Using high-quality Pr₃HHTP₂ single crystals as a model system, this work precisely resolved for the first time the incommensurately modulated structure of a conductive metal-organic framework at 100 K via variable-temperature single-crystal X-ray diffraction, with a modulation vector q = 0.39143(12)c*, and discovered a reversible metal-semiconductor transition at approximately 350 K that perfectly synchronizes with the disappearance of structural modulation, providing compelling evidence for the electronic origin of lattice distortion. Guest water molecules stabilize the modulated phase by cooperatively regulating the relative rotation of ligands and interlayer spacing, thereby optimizing inter-ligand interactions. This study establishes specific experimental criteria for one-dimensional charge density waves in metal-organic frameworks and offers an ideal platform for exploring electron-lattice coupling modulation.\n12. Superconducting properties of the three-dimensional Hofstadter-Hubbard model below the critical flux for Weyl points Relevance Score: 3.5172 Authors: Pierpaolo Fontana, Luca Lepori, Andrea Trombettoni Link: http://arxiv.org/abs/2604.19332v1 Summary: This paper investigates the superconducting properties of the three-dimensional Hofstadter-Hubbard model at critical magnetic flux. By solving the self-consistent gap and chemical potential equations within the mean-field approximation, the authors map out the phase diagram on the flux plane parameterized by coprime pairs. The central finding is the existence of a critical flux Φ_c that divides the system into two distinct regimes: when Φ \u0026gt; Φ_c, the system undergoes a quantum phase transition from a semimetal to a superconductor at a finite interaction strength U_c; whereas when Φ \u0026lt; Φ_c, an arbitrarily weak attractive interaction induces superconductivity, with the gap exhibiting a BCS-type exponential scaling as a function of interaction strength, due to a non-zero density of states at the Fermi level. Near the phase transition point, the authors examine the scaling behavior and determine the critical exponents. The results reveal a profound intrinsic connection between flux-tuned band topology—particularly the emergence of Weyl points—and pairing interactions, elucidating the interplay between magnetic band topology and superconductivity in three-dimensional Hofstadter systems.\n13. Four-layer charge density waves and chirality in CsV$_3$Sb$_5$ Relevance Score: 3.5151 Authors: Fernando de Juan, Mark H. Fischer Link: http://arxiv.org/abs/2604.19328v1 Summary: This study investigates whether a four-layer charge density wave (CDW) in the kagome superconductor CsV₃Sb₅ can induce inversion symmetry breaking through real-space Ginzburg-Landau free energy analysis. Under the rigid-layer limit where each layer is forced into a fixed triple-symmetric tri-hexagonal configuration, the phase diagram is predominantly occupied by AB and ABCD stacking states that preserve inversion symmetry. When the rigid-layer constraint is reasonably relaxed in a manner consistent with first-principles calculation parameters, several new phases emerge, including the AABC state and a distorted ABCD state, which break inversion symmetry and all mirror symmetries, thereby exhibiting chirality. However, these chiral phases occupy only a small portion of the phase space, suggesting that the inversion symmetry breaking observed in CsV₃Sb₅ (such as second-harmonic transport) may originate from other mechanisms rather than solely from the four-layer CDW stacking order.\n14. Griffiths-like phase, spin-phonon coupling, and exchange-bias in the disordered double perovskite GdSrCoMnO$_{6}$ Relevance Score: 3.5140 Authors: Gyanti Prakash Moharana, Diptikanta Swain, Hanuma Kumar Dara, Debendra Prasad Panda, S. N Sarangi Link: http://arxiv.org/abs/2604.19894v1 Summary: This study systematically analyzes the physical properties of the disordered double perovskite GdSrCoMnO₆ through structural, magnetic, and Raman spectroscopy measurements. DC magnetic susceptibility reveals a ferromagnetic transition at approximately 153 K, with inverse susceptibility decreasing above the Curie temperature, consistent with a Griffiths-like phase up to around 172 K. Raman spectra exhibit deviations of phonon frequencies from anharmonic behavior near the magnetic ordering temperature, confirming the presence of spin-phonon coupling. AC susceptibility indicates slow magnetic dynamics below a freezing temperature of about 30 K, and the Mydosh parameter along with Vogel-Fulcher analysis unveils interacting cluster glass behavior. An exchange bias effect is observed at low temperatures, with an exchange bias field of 379 Oe at 5 K, persisting up to 50 K. These phenomena are attributed to magnetic inhomogeneity arising from competition between ferromagnetic and antiferromagnetic interactions due to the random distribution of mixed-valence Co and Mn ions. The study underscores the significant role of structural disorder in modulating magnetic correlations, spin dynamics, and spin-lattice responses.\n15. Controlling Quantum Materials by Growth: Thermodynamics, Kinetics, and Defect Engineering in Transition Metal Dichalcogenides Relevance Score: 3.4856 Authors: Anzar Ali, Md Ezaz Hasan Khan, Mahmoud Abdel-Hafiez Link: http://arxiv.org/abs/2604.19110v1 Summary: The electronic states of transition metal dichalcogenides (TMDs) are strongly coupled to lattice structure, dimensionality, and electronic degrees of freedom, such that crystal growth is not merely a preparative step but rather establishes the thermodynamic boundary conditions that define chemical potentials, defect concentrations, polytype stability, and the accessibility of metastable phases. This article develops a unified thermodynamic and kinetic framework that connects growth conditions to phase stability, defect energetics, and microstructure: chemical potential constraints define stability windows, supersaturation and mass transport control nucleation and morphology, and nonequilibrium pathways enable kinetic trapping and polytype selection. By placing bulk and thin-film methods—including chemical vapor transport, flux growth, physical vapor transport, solvent-assisted crystallization, chemical vapor deposition, and molecular beam epitaxy—within a common thermodynamic-kinetic landscape, it elucidates how distinct growth modes yield characteristic disorder distributions and structural phases. The article explicitly correlates synthesis variables with charge density wave order, superconductivity, band topology, and correlation effects, establishing crystal growth as a central parameter governing the effective electronic Hamiltonian realized in experiments, thereby providing a physical basis for improving reproducibility and deterministic control over emergent quantum phases in layered quantum materials.\n16. Electrically steered conduction topologies and period-doubling phase dynamics in VO2 Relevance Score: 3.4747 Authors: Siyuan Huang, Shuaishuai Sun, Yin Shi, Wentao Wang, Chunhui Zhu, Huanfang Tian, Huaixin Yang, Jun Li, Jianqi Li Affiliations: Chinese Academy of Sciences, Chongqing University, Songshan Lake Materials Laboratory, University of Chinese Academy of Sciences, Hebei Normal University Link: http://arxiv.org/abs/2604.19329v1 Summary: Using a newly developed electrically pulsed ultrafast transmission electron microscope, this work directly visualizes the multiscale electro-thermo-mechanical dynamics of the insulator-metal transition in suspended VO₂ devices. The results reveal that electric-field-induced Poole-Frenkel emission, localized by patterned oxygen vacancies, plays a decisive role in redistributing the built-in electric field to trigger deterministic Mott transitions; the extreme nonlinearity of this effect enables the formation of dynamically reconfigurable connection topologies that bypass conventional thermal limits. Furthermore, the coupling between thermal and elastic energies governs discrete domain evolution, manifesting as stepwise and period-doubling configuration resets characteristic of non-equilibrium phase dynamics in confined geometries. By integrating experimental imaging with phase-field simulations, the authors establish a comprehensive framework for electrically driven insulator-metal transitions and predict sub-100 picosecond switching kinetics. These findings provide a foundation for rationally designing ultrafast, low-energy functional devices through nanoscale defect and strain engineering in correlated systems.\n17. Spatially-resolved voltage-reversal due to Bernoulli potentials in dissipative Bi$_2$Sr$_2$CaCu$_2$O$_{8+x}$ Relevance Score: 3.4402 Authors: Sharadh Jois, Gregory M. Stephen, Samuel W. LaGasse, Genda Gu, Aubrey T. Hanbicki, Adam L. Friedman Affiliations: Laboratory for Physical Sciences, Brookhaven National Laboratory Link: http://arxiv.org/abs/2604.19467v1 Summary: In Bi₂Sr₂CaCu₂O₈₊ₓ Hall bar devices, magnetotransport and critical current measurements were performed. When a DC current exceeding the critical current was applied in the presence of an external magnetic field, the longitudinal differential voltage along one edge of the device was observed to be comparable in magnitude but opposite in sign to that along the opposite edge. This phenomenon was unaffected by reversal of the external magnetic field direction and occurred only in devices with invasive voltage contacts. Through a series of control experiments ruling out other possible factors, this behavior was attributed to particle-hole symmetry breaking in moving vortices, along with the formation of hot spots at the edges due to invasive contacts, which promoted rapid vortex nucleation and flux flow, resulting in opposite vortex velocities at the edges and generating opposing Bernoulli potentials. Hall effect analysis revealed that the carrier type in the dissipative state changed with the magnetic field direction, further supporting the symmetry-breaking interpretation. These findings are of fundamental significance for understanding the composition and flow of dissipative currents in layered superconductors.\n18. Proximity Magnetism in Mn(Bi,Sb)2Te4-(Bi,Sb)2Te3/MnTe Natural Heterostructures Relevance Score: 3.4244 Authors: Owen A. Vail, Shu-Wei Wang, Yasen Hou, Dinura Hettiarachchi, Jean-Felix Milette, Tim B. Eldred, Wenpei Gao, Wendy Sarney, Haile Ambaye, Jong Keum, Valeria Lauter, George J. de Coster, Matthew J. Gilbert, Don Heiman, Jagadeesh S. Moodera, Hang Chi Link: http://arxiv.org/abs/2604.18935v1 Summary: Using scanning transmission electron microscopy and depth-sensitive polarized neutron reflectometry, this study reveals that during the growth of the MnTe/(Bi,Sb)₂Te₃ interface, interdiffusion of Mn spontaneously forms a natural heterostructure with alternating Mn(Bi,Sb)₂Te₄ septuple layers and (Bi,Sb)₂Te₃ quintuple layers. Magneto-transport experiments and quantum magnetic simulations indicate that although the Néel temperature of Mn(Bi,Sb)₂Te₄ itself is only about 20 K, it can mediate an exchange field above this temperature, inducing the anomalous Hall effect at the (Bi,Sb)₂Te₃/MnTe interface and raising the interfacial Néel temperature to over 200 K. This novel magnetic interface also achieves robust, deterministic spin-orbit torque switching without the need for an external magnetic field, with a critical current density as low as 300 kA/cm². This antiferromagnetically coupled natural heterostructure exhibits unique magnetic and topological proximity effects, offering not only rich interfacial physics but also a practical platform for low-power spintronic devices.\n19. Electronic structure and oxidation states in high-pressure synthesized isostructural CeCN$_5$ and TbCN$_5$ Relevance Score: 3.4205 Authors: Amanda Ehn, Florian Trybel, Talha Bin Masood, Leonid V. Pourovskii, Igor A. Abrikosov Affiliations: Linköping University, Université PSL, Institut Polytechnique de Paris Link: http://arxiv.org/abs/2604.19629v2 Summary: Using density functional theory (DFT) combined with the static DFT+U framework and the DFT+dynamical mean-field theory (DMFT) with the quasi-atomic (Hubbard-I) approximation for cross-validation, this study systematically analyzes the electronic properties of the isostructural high-pressure synthesized compounds CeCN₅ and TbCN₅. Calculations reveal that despite their identical crystal structures, Ce and Tb exhibit distinctly different oxidation states: Ce is tetravalent (+4), leading to insulating behavior in CeCN₅, while Tb is trivalent (+3), rendering TbCN₅ metallic. The extra electron contributed by Ce is transferred to and redistributed within the polymeric C–N network, causing specific bond lengths in CeCN₅ to differ from those in TbCN₅. This study confirms that the polymeric C–N network can accommodate different oxidation states of rare-earth ions within an identical structural framework. These results demonstrate that lanthanide carbonitride (LnCN) compounds synthesized under high pressure provide a unique platform for investigating the interplay between 4f electron behavior and structural complexity.\n20. Stealthy hyperuniform disorder: A new route to controlling electric states and magnetic phase transition in correlated systems Relevance Score: 3.3980 Authors: Akihisa Koga, Takanori Sugimoto Link: http://arxiv.org/abs/2604.19041v1 Summary: This study introduces hidden hyperuniform bond distributions into the Hubbard model on a honeycomb lattice. Using exact diagonalization of the non-interacting Hamiltonian, we find that the density of states consistently exhibits linear behavior at low energies, while the hidden nature significantly alters the wavefunction extensivity at high energies and adjusts the density of states structure near the band edges. Magnetic analysis via the real-space Hartree approximation reveals a quantum phase transition from a semimetallic state to an antiferromagnetic ordered phase, with the critical interaction strength being highly sensitive to hyperuniformity. Comparison with quasiperiodic honeycomb tilings further underscores the crucial role of structural correlations. These findings demonstrate that hidden hyperuniform disorder provides a novel pathway for tuning electronic states and magnetic phase transitions in correlated systems.\n","permalink":"https://nickelates.uk/en/posts/2026-04-21-arxiv-daily/","summary":"\u003cblockquote\u003e\n\u003cp\u003e\u003cstrong\u003eDaily Overview\u003c/strong\u003e:\nGreetings readers, welcome to today\u0026rsquo;s overview of papers in the nickel-based superconductivity field. Although no works directly targeting nickelates as the research subject are included today, multiple papers focus on physical mechanisms closely related to the core issues of nickel-based superconductivity. Among them, [1] decomposes the pseudogap in cuprates via nuclear magnetic resonance shift, proposing three condensation rules for spin-singlet pairing, thereby providing a unified framework for understanding the electronic phase diagram of layered oxide superconductors. [13], based on real-space Ginzburg-Landau analysis, explores the inversion symmetry breaking and chirality induced by four-layer charge density waves in the Kagome superconductor CsV₃Sb₅, with conclusions that are relevant to similar possible CDW order in nickelates. [20] introduces hidden hyperuniform disorder into the Hubbard model, revealing the high sensitivity of electronic states and magnetic phase transitions in correlated systems to ordered microstructures, offering new insights into the regulation of disorder effects in nickelates.\n\u003cstrong\u003earXiv submission processing window\u003c/strong\u003e: 2026-04-20 20:00 to 2026-04-21 18:14 UTC.\u003c/p\u003e","title":"arXiv Daily: nickelate superconductors 2026-04-21"},{"content":" Daily Overview: Today\u0026rsquo;s highlights focus on deepening the understanding of the electronic structure of mixed Ruddlesden-Popper nickelates. In [1], a review systematically summarizes experimental and theoretical progress on RP-phase nickel oxide superconductors, emphasizing that ultra-thin La₃Ni₂O₇ films grown on compressively strained substrates achieve ambient-pressure superconductivity, enabling experimental techniques such as angle-resolved photoemission spectroscopy. Theoretically, the Ni e_g and a_{1g} orbitals and the interlayer dimer picture are highlighted as key factors. In [3], density matrix renormalization group simulations of a three-leg t-J ladder with strong inter-chain coupling reveal that pair correlation functions exhibit power-law decay near 1/3 hole doping, forming asymmetric pairing compared to electron doping, providing numerical evidence for understanding the electronic properties of trilayer nickelate superconductors. These works collectively advance the understanding of the microscopic mechanism of nickel-based superconductivity. arXiv submission processing window: 2026-04-19 20:01 to 2026-04-20 19:34 UTC.\n1. Superconductivity in Ruddlesden-Popper nickelates: a review of recent progress, focusing on thin films Relevance Score: 5.8669 Authors: Yang Zhang, Ling-Fang Lin, Thomas A. Maier, Elbio Dagotto Link: http://arxiv.org/abs/2604.18385v2 Summary: In recent years, significant breakthroughs have been achieved in the study of Ruddlesden-Popper (RP) nickel oxide superconductors. This article systematically reviews the experimental and theoretical progress in this field, with a particular focus on thin-film systems. Key findings include the emergence of superconductivity in bilayer La₃Ni₂O₇ (T_c ~ 80 K) and trilayer La₄Ni₃O₁₀ under high pressure, and, critically, the realization of ambient-pressure superconductivity in ultra-thin films of La₃Ni₂O₇ grown on substrates providing compressive strain—a breakthrough that overcomes the high-pressure limitation and enables the use of experimental techniques previously inaccessible in the superconducting state, such as angle-resolved photoemission spectroscopy (ARPES). On the theoretical side, the system requires simultaneous consideration of both the Ni e_g and a_{1g} orbitals, as well as the strong interlayer coupling within bilayers that gives rise to a \u0026ldquo;dimer\u0026rdquo; picture, and exhibits strange metal behavior and strong correlation features reminiscent of cuprates. By comparing the similarities and differences among various RP nickel oxides, this article offers a new perspective on understanding the mechanism of high-temperature superconductivity in correlated electron systems and outlines future research directions.\n2. Magnetism and symmetry of superconducting gap in LaFeAsO from dynamical mean-field theory Relevance Score: 4.1208 Authors: S. L. Skornyakov, V. I. Anisimov, A. A. Katanin Link: http://arxiv.org/abs/2604.18582v1 Summary: By combining density functional theory with dynamical mean-field theory (DFT+DMFT), this study systematically investigates the effects of electronic correlations on the magnetic and superconducting properties of the iron-based parent compound LaFeAsO. The calculations reveal that the static nonlocal magnetic susceptibility peaks at the in-plane wave vector (π,π), and this peak is significantly enhanced after incorporating vertex corrections via the ladder approximation, leading to magnetic instability. Solving the eigenfunctions of the Bethe-Salpeter equation using second-order perturbation theory and the ladder method with dynamical interaction vertices, the resulting order parameters exhibit close competition: second-order perturbation favors d-wave pairing, while the ladder method supports s±-wave symmetry. The study indicates that the dominance of s± instability in the ladder DFT+DMFT approach arises because the itinerant degrees of freedom reduce the degree of magnetic frustration after the formation of local magnetic moments. The final conclusion demonstrates that dynamical correlation effects do not alter the primary superconducting instability (s±-wave) in LaFeAsO.\n3. Pairing properties of correlated three-leg ladders with strong interchain couplings near 1/3 filling Relevance Score: 4.0995 Authors: Yushi Yamada, Tatsuya Kaneko, Masataka Kakoi, Ryota Ueda, Kazuhiko Kuroki Link: http://arxiv.org/abs/2604.17812v1 Summary: This paper employs the density matrix renormalization group method to study the ground-state properties of a three-leg t-J ladder with strong interchain coupling near 1/3 filling. When holes are doped into the spin-gapped state at 1/3 filling, the pairing correlation function exhibits power-law decay while the spin correlation function decays exponentially; in contrast, electron doping does not significantly enhance pairing correlations. Further comparison with the three-leg Hubbard model shows that the pairing correlation properties of the hole-doped state are similar to those of the t-J model, but require a sufficiently large spin gap. The study indicates that hole doping near 1/3 filling favors superconducting pairing, and this asymmetric pairing property differs from the phase diagram predicted by weak-coupling theory, providing numerical evidence for understanding the electronic properties of tri-layer nickelate superconductors.\n4. Bose metal near pair-density-wave order in a spin-orbit-coupled Kondo lattice Relevance Score: 4.0142 Authors: Piers Coleman, Aaditya Panigrahi, Alexei Tsvelik Link: http://arxiv.org/abs/2604.18451v2 Summary: In three-dimensional superconductors, a non-Abelian order parameter with SU(2) symmetry can support an extended resistive state—a Bose metal—whose transport is carried by bosonic bound states formed between electrons and Majorana fermions, separating the uniform superconducting phase from the pair-density-wave (PDW) phase. This conclusion is based on a solvable Kondo lattice model, where Kondo screening of the Yao-Lee spin liquid yields an SU(2) order parameter with both superconducting and spin-density-wave components, rather than the conventional U(1) symmetry. Two effects cooperate to make fluctuations exceptionally strong in three dimensions: near the Lifshitz point where the optimal pairing momentum changes from zero to a finite value, the quadratic superfluid stiffness vanishes, and the order parameter manifold expands to SU(2). Building on the previous finding that doping-driven finite-momentum electron-Majorana condensation leads to amplitude-modulated PDW order, this work employs a nonlinear sigma model to analyze the fluctuation-dominated regime above that phase. It finds that the order parameter propagator develops a soft-mode ring in the disordered phase, and the resistivity approximately follows a R ~ T³ scaling law in three dimensions. Such strong fluctuation mechanisms in non-Abelian PDW systems may shed light on anomalous phenomena in heavy-fermion materials such as UTe₂.\n5. Photoinduced orbital polarization and Jahn-Teller effect in RNiO$_3$ Relevance Score: 3.9045 Authors: Sangeeta Rajpurohit, Sheikh Rubaiat Ul Haque, Aaron M. Lindenberg, Peter E. Blöchl, Tadashi Ogitsu Link: http://arxiv.org/abs/2604.18524v2 Summary: By combining an interacting multi-band tight-binding model with real-time electron-ion-spin dynamics simulations, this work investigates the non-equilibrium behavior of rare-earth nickelates RNiO₃ under polarized light excitation. It is found that d-d transitions excited by linearly polarized light effectively reduce the local magnetic moment at Ni sites and suppress Hund coupling, while orbital-selective transitions achieved by tuning the light polarization direction lead to an imbalance in eg orbital occupancy. This non-equilibrium state, characterized by orbital polarization and reduced effective Hund coupling, further triggers Jahn-Teller distortion, driving structural relaxation along coherently excited JT modes. The results demonstrate that polarization-controlled photoexcitation can activate otherwise inert orbital degrees of freedom in equilibrium and induce a hidden non-thermal phase with long-range orbital order, offering a new route for coherent control of charge, spin, and lattice degrees of freedom on ultrafast timescales.\n6. Proximitized Topological Insulator Charge Island Fabricated via In Situ Multi-Angle Stencil Lithography Relevance Score: 3.7722 Authors: Benedikt Frohn, Tobias Schmitt, Vanessa Serrano, Anne Schmidt, Michael Schleenvoigt, Albert Hertel, Benjamin Bennemann, Abdur Rehman Jalil, Detlev Grützmacher, Peter Schüffelgen Link: http://arxiv.org/abs/2604.18736v1 Summary: This paper presents a fully in situ multi-angle mask lithography technique for fabricating proximity-superconducting topological insulator charge islands. The method combines selective area growth of (Bi,Sb)₂Te₃ nanoribbons with angle-controlled deposition of a platinum diffusion barrier, superconducting aluminum, and an ultrathin aluminum oxide tunnel barrier, all performed in vacuum to avoid post-growth processing and surface oxidation. Low-temperature transport measurements reveal robust Coulomb blockade and significant suppression of low-energy conductance, which disappears under an applied magnetic field, confirming the presence of a proximity-induced superconducting gap in the island. However, no transition from 2e to 1e charging periodicity is observed, indicating that charge parity is not preserved, which is attributed to quasiparticle states within the soft gap and quasiparticles introduced by normal-metal leads. This work provides a clean, scalable nanofabrication platform for topological insulator-superconductor hybrid systems, laying the foundation for studying topological superconductivity and Majorana physics.\n7. Metal Atom (Dis)Order and Superconductivity in YCaH$_{n}$ ($n=8-20$) High-Pressure Superhydrides Relevance Score: 3.7384 Authors: Masashi W. Kimura, Seong Won Jang, Nisha Geng, Eva Zurek Link: http://arxiv.org/abs/2604.17712v1 Summary: This study systematically explores the structural and superconducting properties of the YCaHₙ (n=8–20) system under high pressures of 100–300 GPa using density functional theory calculations and evolutionary algorithms, with a focus on the effects of metal atom disorder and doping on the superconducting transition temperature (Tc). For YCaH₈, multiple phases with different metal atom arrangements are found to be nearly isenthalpic, indicating that configurational entropy plays a significant role in phase stability. Equimolar Y and Ca tune the Fermi level to near the peak of the density of states, yielding Tc values of 149 K and 170 K for the P4/mmm and Cmmm phases at 180 GPa, respectively, based on isotropic Eliashberg theory. YCaH₁₂ also exhibits a tendency toward disorder, but its ordered variants show a wide Tc range (105–253 K) at 200 GPa, suggesting that doping can either mildly enhance or substantially suppress Tc. For YCaH₁₈ and YCaH₂₀, solely a single dynamically stable phase is predicted, attributed to the differences in their stable parent binary structures. This work highlights the regulatory roles of metal atom disorder and equimolar composition in modulating the electronic structure and superconducting performance of high-pressure superhydrides.\n8. Competition and coexistence of superconductivity and nematic order in a two-dimensional electron gas with quadrupolar interactions Relevance Score: 3.6771 Authors: Nei Lopes, Guilherme da Silva do Vale, Daniel G. Barci Link: http://arxiv.org/abs/2604.18777v1 Summary: This paper employs a mean-field approach to investigate the competition and coexistence of superconductivity and nematic order in a two-dimensional electron gas with pairing and quadrupole forward scattering interactions. The model simultaneously considers s-wave and d-wave superconducting channels, and the free energy density and phase diagram are obtained by solving five sets of coupled self-consistent equations. At zero temperature, nematic order strongly competes with d-wave superconductivity, leading to a direct first-order phase transition, while pairing with s-wave allows for a coexistence phase characterized by a uniform superconducting gap on an anisotropic Fermi surface. At finite temperature, the quadrupole interaction promotes the emergence of additional superconducting components, resulting in a coexistence region of s-wave, d-wave, and nematic order. The study reveals the crucial roles of symmetry and interaction strength in determining the phase structure, providing a minimal theoretical framework for describing intertwined nematic and superconducting phases in correlated electron systems.\n9. Anisotropic Superconducting Diode Effect in Planar Josephson Junctions Relevance Score: 3.6681 Authors: Abhishek Chilampankunnel Prasannan, Baris Pekerten, Nowar Alashkar, Alex Matos-Abiague Link: http://arxiv.org/abs/2604.17594v1 Summary: This work systematically investigates the dependence of the superconducting diode effect (SDE) on magnetic field direction and crystalline orientation in planar Josephson junctions with coexisting Rashba and Dresselhaus spin-orbit coupling, using symmetry analysis, phenomenological modeling, analytic approximations in the narrow-junction low-field regime, and tight-binding Bogoliubov–de Gennes simulations. It is found that the SDE completely vanishes under specific geometric conditions between the magnetic field and crystal axes, providing experimentally verifiable signatures for probing the interplay between spin-orbit coupling and the Zeeman effect. Analytic analysis reveals that the SDE efficiency depends on the relative orientation of the effective spin-orbit field and the applied magnetic field, with the anisotropy originating from Fermi surface distortion and anisotropic Cooper pair momentum induced by spin-orbit coupling. The simulations reproduce recent experimental observations of electrostatic gate-induced SDE polarity reversal even with only Rashba spin-orbit coupling, and predict additional polarity reversals under specific magnetic field directions, junction geometries, and spin-orbit coupling ratios. These findings elucidate the microscopic mechanism of anisotropic nonreciprocal superconducting transport in planar Josephson junctions and provide clear guidance for experimentally identifying the physical mechanism of the SDE in semiconductor-based Josephson junctions.\n10. Enhanced Anomalous Nernst Effect in the Ferromagnetic Kondo Lattice CeCo2As2 Relevance Score: 3.6518 Authors: Shuyue Guan, Weian Guo, Pengyu Zheng, Xinxuan Lin, Yuqing Huang, Jiawei Li, Xiao-Bin Qiang, Longfei Li, Weiwei Xie, Hai-Zhou Lu, Zhiping Yin, Shuang Jia Link: http://arxiv.org/abs/2604.17987v1 Summary: In the ferromagnetic Kondo lattice CeCo₂As₂, a significantly enhanced anomalous Nernst effect is observed, with an anomalous Nernst coefficient reaching 7.4 μV/K at 40 K and an anomalous Nernst angle of 144% at 3 K, far exceeding those of the Seebeck coefficient and common topological magnets. Combining transport measurements with DFT+DMFT calculations reveals that this enhancement originates from strong Berry curvature in flat bands dominated by f-electron orbitals, where multiple hybridization band gaps and Weyl nodes generated by Kondo hybridization lie within a few millielectronvolts of the Fermi level. Compared with LaCo₂As₂, which contains no f electrons, the Kondo effect in CeCo₂As₂ effectively pins the Fermi level within the topological flat bands, concentrating the Berry curvature in a narrow energy window and thereby greatly enhancing the anomalous Nernst conductivity and Hall conductivity (reaching 710 Ω⁻¹cm⁻¹ at 2 K). This correlation-driven topological state breaks the conventional Mott relation, highlighting the unique advantages of ferromagnetic Kondo lattices in thermoelectric conversion and providing a new pathway for enhancing the thermoelectric performance of topological states via electron correlation.\n11. Type-II-like ultrafast demagnetization behavior in NiCo2O4 thin films Relevance Score: 3.5841 Authors: Ryunosuke Takahashi, Kaede Yamada, Harjinder Singh, Kanata Watanabe, Junta Igarashi, Julius Hohlfeld, Jon Gorchon, Gregory Malinowski, Daisuke Kan, Yuichi Shimakawa, Takayuki Ishibashi, Stephane Mangin, Hiroki Wadati Link: http://arxiv.org/abs/2604.17916v1 Summary: Using time-resolved magneto-optical Faraday effect with two independent pump-probe systems operating at 1030/515 nm and 800/400 nm, the photo-induced magnetization dynamics of epitaxial NiCo₂O₄ thin films were investigated. The experiments revealed an ultrafast demagnetization signal occurring immediately after photoexcitation (within the time resolution), followed by a reproducible slower demagnetization component with a characteristic time of approximately 5–6 ps, and a subsequent recovery process on the order of 100 ps. This picosecond demagnetization component consistently appeared in both experimental configurations and at different excitation wavelengths, confirming it as an intrinsic feature of the ultrafast magnetic response of NiCo₂O₄ thin films. Given that the earliest signal decay may include transient optical contributions, the overall response is described as type II-like behavior rather than being strictly classified as textbook type II based on the sub-resolution signal. These results establish a robust two-step ultrafast demagnetization mechanism in NiCo₂O₄, highlighting the potential of rare-earth-free oxide ferrimagnets for exploring multi-sublattice spin dynamics on ultrafast timescales.\n12. $0-π$ transitions in non-Hermitian magnetic Josephson junctions Relevance Score: 3.3798 Authors: Roberto Capecelatro, Marco Marciani, Claudio Guarcello, Gabriele Campagnano, Procolo Lucignano, Roberta Citro Link: http://arxiv.org/abs/2604.17978v1 Summary: This paper investigates the transport properties of non-Hermitian magnetic Josephson junctions, which consist of superconductor-quantum dot-superconductor devices coupled to a ferromagnetic reservoir and subjected to an external magnetic field. The focus is on the 0-π transition of the equilibrium phase difference between the superconductors, which shifts from 0 to π as the magnetic field increases. The environmental coupling introduces spin-dependent dissipation, broadening the Andreev levels in the junction region. By combining Green\u0026rsquo;s function calculations with an effective non-Hermitian description restricted to subgap Andreev quasibound states, the authors find that dissipation drives the 0-π transition to higher magnetic field values. Notably, at a fixed magnetic field strength, the relative angle between the applied field and the magnetization direction of the reservoir can also induce this transition, an effect entirely attributable to the complex eigenvalue behavior of the non-Hermitian Hamiltonian. These results indicate that non-Hermiticity can serve as a new control degree of freedom for engineering the current-phase relation of superconducting junctions.\n13. Polarization Engineering of the Orbital Hall Conductivity in Two-dimensional Ferroelectric Higher-Order Topological Insulator Tl$_2$S and SnS Relevance Score: 3.2688 Authors: YingJie Hu, Heng Gao, Yabei Wu, Wei Ren Link: http://arxiv.org/abs/2604.18093v1 Summary: This work systematically investigates two types of two-dimensional ferroelectric higher-order topological insulators (HOTIs) with out-of-plane polarization (represented by Tl₂S) and in-plane polarization (represented by SnS) using density functional theory, revealing the microscopic mechanism of polarization-controlled orbital Hall conductivity (OHC). It is found that the out-of-plane polarization in Tl₂S is decoupled from the higher-order topological phase, and the rotation-symmetry-protected higher-order topological corner states remain robust during polarization reversal, resulting in a persistent OHC plateau within the band gap and thus enduring orbital transport characteristics. In contrast, the introduction of in-plane polarization in SnS breaks the crystal rotational symmetry and drives a higher-order topological phase transition: the non-polarized phase is a trivial insulator, while the polarized phase exhibits higher-order topological corner states protected by C₄ rotational symmetry. This phase transition is accompanied by a reversible switching of the OHC plateau from zero to a finite value, indicating that in-plane polarization can serve as an intrinsic means to achieve orbital transport switching. Further analysis of the orbital Berry curvature reveals that the OHC originates from the non-zero expectation values of the orbital angular momenta of S and Tl at the top of the valence band. This work elucidates the coupling among ferroelectricity, higher-order topology, and orbital transport, providing new insights for the development of electrically controlled orbital electronic devices.\n14. Moire Control of Alterelectric Quadrupolar Order Relevance Score: 3.2472 Authors: Alejandro Lopez-Bezanilla Link: http://arxiv.org/abs/2604.18428v1 Summary: This paper proposes the continuous tuning of alternating electric quadrupole order using moiré superlattices. Based on Bloch periodic two-orbital theory, the slowly varying interlayer stacking coordination is coarse-grained into an effective moiré field that acts on self-consistent two-component alternating electric quadrupoles. It is found that this ordered state forms above a filling-dependent instability threshold and evolves from a weak selection regime into a robust axial-dominated ground state, with diagonal branches being only weak competitors. By varying the coordination phase, the orientation can be guided along a continuous path in the internal quadrupole space, demonstrating that the moiré superlattice not only stabilizes alternating electric order but also enables directional control of its internal orientation. This orientational selection is directly encoded in the redistribution of low-energy spectral weight in the moiré Brillouin zone. These results establish moiré superlattices as a universal platform for realizing controllable alternating electric order and programmable anisotropic electronic functionalities.\n15. Multipolar Piezoelectricity and Anisotropic Surface Transport in Alterelectrics Relevance Score: 3.2447 Authors: Amber Visser, Viktor Könye, Oleg Janson, Jeroen van den Brink, Corentin Coulais, Jasper van Wezel Link: http://arxiv.org/abs/2604.18324v1 Summary: This study introduces the concept of \u0026ldquo;alterelectrics\u0026rdquo; as a non-magnetic analog of altermagnets. By constructing symmetry structures that substitute magnetization with electric polarization, alterelectrics achieve quadrupole piezoelectric effects and hyperbolic dispersion without breaking time-reversal symmetry. Based on a minimal Lieb lattice model, the authors demonstrate that alterelectrics exhibit equal and opposite piezoelectric responses along orthogonal directions under applied strain, with a net zero polarization vector, analogous to the magnetization behavior of altermagnets. Further investigations show that finite-sized alterelectric slabs can support surface states localized on different surfaces, with dispersion relations exhibiting fourfold rotational differences, causing wave packets to propagate along distinct directions on opposite surfaces, thereby enabling surface-dependent anisotropic electronic transport—termed \u0026ldquo;surface electronics\u0026rdquo;—which is analogous to spin-separated transport in altermagnets but based on charge rather than spin. To validate the concept, a first-principles material model (Sr₄CuTe₀.₅W₀.₅TiZrO₁₂) based on a perovskite structure was designed, and density functional theory calculations confirmed zero net polarization, while strain applied along the diagonal direction induced polarization responses along the coordinate axes, verifying quadrupole piezoelectricity. It is concluded that alterelectrics extend the symmetry-driven properties of altermagnets to the electric polarization system, and the anisotropic transport of surface states offers a new pathway for spintronic-free applications, with such designs being generalizable to other systems that break specific symmetries.\n16. Chiral Magnetism and Quantum Anomalous Hall Effect in a Low-energy Kondo Model on the Triangular Lattice Relevance Score: 3.2323 Authors: Kai Vylet, Xingkai Huang, Leon Balents Link: http://arxiv.org/abs/2604.17641v1 Summary: We study a low-energy Kondo model on a triangular lattice, where itinerant electrons occupy a valence band pocket at the Γ point and three conduction band pockets at the M points in the Brillouin zone; this Fermi surface nesting structure favors triple-Q magnetic order. Treating the local moments as classical spins on a four-sublattice magnetic unit cell, we employ a differential evolution algorithm to search for the ground states, finding that in addition to ferromagnetic and coplanar phases, a wide range of non-coplanar orders emerge, including tetrahedral and related canted tetrahedral states. The chiral phase remains stable over a broad range of Kondo couplings and persists under an external magnetic field. For certain chiral magnetic orders, an energy gap opens in the electronic bands, giving rise to a quantum anomalous Hall state with a Hall conductivity of σ_xy = 4e^2/h. These results indicate that chiral magnetism and the quantum anomalous Hall effect on the triangular lattice do not rely on specific tight-binding band structures but can arise generically from low-energy nested pockets at the Γ and M points.\n17. Direct observation of quadruple spin-texture locking in a 2D d-wave altermagnet Relevance Score: 3.1646 Authors: Dan Mu, Bei Jiang, Qingchen Duan, Zulin Xu, Xingkai Cheng, Yusen Xiao, Xinru Han, Xinyu Liang, Zhaokun Luo, Ryan L. Kong, Qiheng Wang, Junwei Liu, Jianxin Zhong, Ruidan Zhong, Qiangqiang Gu, Baiqing Lv, Hong Ding Affiliations: Southern University of Science and Technology, The Hong Kong University of Science and Technology, Hefei National Laboratory, Shanghai University, Shanghai Jiao Tong University, Shanghai Research Center for Quantum Sciences Link: http://arxiv.org/abs/2604.18337v1 Summary: By employing spin-polarized scanning tunneling microscopy with an in-situ switchable spin-polarized Cr tip, we directly observe four types of spin texture locking in the two-dimensional d-wave altermagnet RbV2Se2O. At the real-space atomic scale, different V sublattices exhibit opposite c-axis spin polarization, providing the first microscopic evidence of spin-lattice locking; impurity-induced orthogonal standing waves correspond one-to-one with spin polarization directions, confirming spin-scattering locking. In momentum space, quasiparticle interference patterns display complementary d-wave anisotropy, indicating spin-momentum locking. Additionally, an unexpected long-period stripe modulation locks the spin polarization of defect states on adjacent stripes to opposite directions, i.e., spin-stripe locking, attributed to the emergence of a spin-density-wave Moiré pattern. These results establish for the first time a unified fourfold spin texture locking picture in a two-dimensional d-wave altermagnet, offering a new platform for exploring many-body interactions among spin, lattice, momentum, Moiré potential, and valley degrees of freedom.\n18. Magnetotransport and Phase competition in three-dimensional Hubbard-Holstein model at half-filling Relevance Score: 3.1519 Authors: Sandip Halder, Moshe Schechter Link: http://arxiv.org/abs/2604.18219v1 Summary: Using semiclassical Monte Carlo simulations based on exact diagonalization and treating phonons in the adiabatic limit, this paper systematically investigates the magnetotransport properties of the three-dimensional half-filled single-band Hubbard-Holstein model. At low temperatures, the phase diagram as a function of electronic correlation U and electron-phonon coupling V reveals two insulating phases—antiferromagnetic insulator (AF-I) and charge-ordered insulator (CO-I)—separated by a first-order phase transition line, with no metallic phase emerging at their intersection, indicating the robustness of these phases in three dimensions. When U is close to the bandwidth, the phase diagram in the V versus temperature T plane contains multiple phases: AF-I, CO-I, Mott-Hubbard insulator, bipolaron insulator, and two types of bipolaron metallic states (BP-M and BP-M*), with several first-order transitions occurring near V ≈ 3.75. Above the ordering temperature, the density of states (DOS) exhibits universal behavior dominated by electronic contributions, while analysis of the magnetic susceptibility and DOS reveals pseudogap features. The study of magnetic and transport properties along the phase boundaries uncovers strong proximity effects between competing phases, offering potential pathways for tuning correlated materials and realizing emergent electronic states.\n19. Asymmetric Scattering-Induced Neel Spin-Orbit Torque in Antiferromagnets Relevance Score: 3.1432 Authors: Sayan Sarkar, Amit Agarwal Link: http://arxiv.org/abs/2604.18097v1 Summary: This study proposes a novel mechanism for generating Néel spin–orbit torque in antiferromagnets, originating from the coupling between asymmetric impurity scattering and the anomalous spin polarizability of Bloch electrons. Conventional theory holds that staggered spin polarization in collinear antiferromagnets arises solely from symmetric scattering processes, with the response required to be odd under combined space-time inversion symmetry. Using the Boltzmann framework, the authors demonstrate that antisymmetric high-order scattering processes interacting with band geometry, such as Berry curvature, convert the originally even anomalous spin polarizability into an odd response, thereby yielding an extrinsic anomalous skew-scattering contribution. Tight-binding model calculations based on tetragonal CuMnAs show that this contribution can be comparable to or even exceed the conventional Drude symmetric scattering channel and is tunable with impurity density and barrier strength. Further analysis reveals that this mechanism effectively enhances the Néel vector switching dynamics, offering a band-geometry-driven efficient pathway for electrical control of antiferromagnets.\n20. Magnetic-fluctuation-driven suppression of spin-orbit hybridization in the surface ferromagnet GdAg$_2$/Ag(111) Relevance Score: 3.1312 Authors: Ryo Noguchi, Jongkeun Jung, Younsik Kim, Sungsoo Hahn, Changyoung Kim Link: http://arxiv.org/abs/2604.18009v1 Summary: Through temperature- and polarization-dependent angle-resolved photoemission spectroscopy, this work investigates the influence of spin fluctuations on spin–orbit coupling (SOC) hybridization in the surface ferromagnet GdAg₂/Ag(111). It is experimentally observed that even above the Curie temperature, band splitting induced by local Gd magnetic moments can maintain band crossings similar to Weyl nodal lines; however, SOC-induced band hybridization occurs only at low temperatures with long-range ferromagnetic order, manifesting as a spectral weight redistribution toward higher binding energies. The suppression of hybridization at high temperatures involves a reduction in effective SOC coupling strength due to spin fluctuations and differences in scattering rates among bands, which can be described by an effective non-Hermitian Hamiltonian. These results indicate that magnetic fluctuations are a key means of tuning SOC hybridization and Berry curvature, and reveal that magnetic materials serve as an ideal platform for exploring non-Hermitian band physics.\n","permalink":"https://nickelates.uk/en/posts/2026-04-20-arxiv-daily/","summary":"\u003cblockquote\u003e\n\u003cp\u003e\u003cstrong\u003eDaily Overview\u003c/strong\u003e:\nToday\u0026rsquo;s highlights focus on deepening the understanding of the electronic structure of mixed Ruddlesden-Popper nickelates. In [1], a review systematically summarizes experimental and theoretical progress on RP-phase nickel oxide superconductors, emphasizing that ultra-thin La₃Ni₂O₇ films grown on compressively strained substrates achieve ambient-pressure superconductivity, enabling experimental techniques such as angle-resolved photoemission spectroscopy. Theoretically, the Ni e_g and a_{1g} orbitals and the interlayer dimer picture are highlighted as key factors. In [3], density matrix renormalization group simulations of a three-leg t-J ladder with strong inter-chain coupling reveal that pair correlation functions exhibit power-law decay near 1/3 hole doping, forming asymmetric pairing compared to electron doping, providing numerical evidence for understanding the electronic properties of trilayer nickelate superconductors. These works collectively advance the understanding of the microscopic mechanism of nickel-based superconductivity.\n\u003cstrong\u003earXiv submission processing window\u003c/strong\u003e: 2026-04-19 20:01 to 2026-04-20 19:34 UTC.\u003c/p\u003e","title":"arXiv Daily: nickelate superconductors 2026-04-20"},{"content":" Daily Overview: Today\u0026rsquo;s highlights focus on the pairing mechanism of the bilayer nickelate La₃Ni₂O₇ high-temperature superconductor, revealing that a unified framework based on the \u0026ldquo;gene principle\u0026rdquo; and the \u0026ldquo;cooperative Fermi surface rule\u0026rdquo; can be naturally extended to this bilayer multi-orbital system. Two dominant antiferromagnetic superexchange channels cooperatively generate a stable s± superconducting state, offering new perspectives for understanding the unique electronic environment of nickel-based superconductivity. Additionally, although not directly targeting nickelates, today\u0026rsquo;s list includes studies on the G-type antiferromagnetic order and hidden altermagnetism in Rb₁₋ₓV₂Te₂O, as well as the microscopic detection of hidden magnetic entropy in the orbital glass state of Ba₂NaOsO₆. The physical mechanisms explored in these studies—such as spin-orbit coupling, hidden order, and d-wave spin splitting—are closely related to the core issues currently addressed in the field of nickel-based superconductivity, including pairing symmetry, spin fluctuations, and orbital effects, warranting cross-disciplinary attention. arXiv submission processing window: 2026-04-19 00:56 to 2026-04-19 18:01 UTC.\n1. Pairing Mechanism in Bilayer Nickelate La$_3$Ni$_2$O$_7$ Superconductors Relevance Score: 5.7408 Authors: Xianxin Wu, Tao Xiang, Jiangping Hu Link: http://arxiv.org/abs/2604.17181v1 Summary: Research on the pairing mechanism of the bilayer nickelate La₃Ni₂O₇ high-temperature superconductor demonstrates that the unified framework based on the “genesis principle” and the “synergistic Fermi surface rule” can be naturally extended to this bilayer multi-orbital system. Through strong-correlation analysis, two dominant antiferromagnetic superexchange channels are identified: the intralayer same-orbital (d_z²) nearest-neighbor exchange J⊥ mediated by the inner apical oxygen, and the interlayer different-orbital (d_z² and d_x²-y²) nearest-neighbor exchange J_xz mediated by the in-plane oxygen. Due to the bilayer bonding-antibonding splitting and the B₁g symmetry of the d_x²-y² orbital, the two channels cooperate to produce a stable s± superconducting state, characterized by internal sign reversal between the mirror-even and mirror-odd Fermi surface pockets in momentum space. Both pairing channels maximize the superconducting gap on the β pocket with a form factor of (cosk_x − cosk_y)². This result incorporates La₃Ni₂O₇ into the unified framework of unconventional superconductivity while revealing its unique electronic environment for high-temperature superconducting pairing.\n2. Influence of Ni substitution on the phase transitions and magnetocaloric effect of NdCo2 at cryogenic temperatures Relevance Score: 3.9354 Authors: Vilde G. S. Lunde, Øystein S. Fjellvåg, Allan M. Döring, Marc Straßheim, Vladimir Pomjakushin, Konstantin P. Skokov, Oliver Gutfleisch, Tino Gottschall, Joachim Wosnitza, Anja O. Sjåstad, Bjørn C. Hauback, Christoph Frommen Affiliations: Institute for Energy Technology, Paul Scherrer Institute, Technische Universität Dresden, Technical University of Darmstadt, Helmholtz-Zentrum Dresden-Rossendorf, University of Oslo Link: http://arxiv.org/abs/2604.17336v1 Summary: This study investigates the phase transitions and magnetocaloric effects of the cubic Laves compounds NdCo₂₋ₓNiₓ (x = 0 to 1) using neutron diffraction and magnetization measurements. The results show that NdCo₂ undergoes sequential structural phase transitions from cubic to tetragonal (100 K) and from tetragonal to orthorhombic (42 K) upon cooling, corresponding to ferromagnetic ordering along the c-axis and reorientation of magnetic moments toward the ab-plane, respectively. With increasing Ni substitution, both transition temperatures decrease, and the orthorhombic phase is completely suppressed when x ≥ 0.5. Meanwhile, Ni substitution reduces the magnetic moment. The indirectly and directly determined magnetocaloric effects are in good agreement: under a 20 T magnetic field, the adiabatic temperature change of NdCo₂ is 6.3 K, while that of NdCoNi (x = 1) decreases to 4.9 K due to the reduced magnetic moment. The study demonstrates that partial substitution of Co with Ni effectively modulates the crystal structure, magnetic ordering, and magnetocaloric properties, but reduces the magnitude of the magnetocaloric effect.\n3. G-type antiferromagnetic structure in Rb1-xV2Te2O Relevance Score: 3.7802 Authors: Wu Xie, Changchao Liu, Fayuan Zhang, Zhenhong Tan, Wenhai Ji, Nan Zhao, Lingxiang Bao, Dong Zhang, Feiran Shen, Lunhua He, Hao Wang, Rong Du, Guanghan Cao, Chaoyu Chen, Ping Miao Link: http://arxiv.org/abs/2604.17365v2 Summary: This study systematically investigates the magnetic structure of the layered metal compound Rb₀.₈₈V₂Te₂O using neutron powder diffraction techniques. Experiments were conducted on the TREND and GPPD diffractometers at CSNS, and by combining Rietveld refinement, magnetic space group analysis, and irreducible representation methods, it is determined that this material exhibits G-type antiferromagnetic ordering below 337 K, with a magnetic propagation vector of (0,0,0.5), magnetic moments aligned along the c-axis, and a moment magnitude of approximately 1.43 μB at 5 K. This result differs from the C-type antiferromagnetic ground state predicted by density functional theory, which was originally considered an ideal configuration supporting d-wave spin-symmetry alternating magnetism. However, previous spin-resolved photoemission spectroscopy and scanning tunneling microscopy/spectroscopy experiments have observed d-wave spin polarization, indicating that this material is a candidate for room-temperature alternating magnetism. The determination of the magnetic structure in this work implies that the actual G-type antiferromagnetic order cannot directly produce global d-wave spin splitting, but the observed spin polarization features may be explained by local alternating magnetic order within a single layer (i.e., \u0026ldquo;hidden alternating magnetism\u0026rdquo;). This finding provides critical microscopic magnetic structural information for understanding the alternating magnetism mechanism in Rb₁₋ₓV₂Te₂O and promotes further research into the origin of alternating magnetism in similar systems.\n4. Collective Resonance of Superconducting/Normal Domain Walls in the Intermediate State of type-I superconductor Relevance Score: 3.7769 Authors: Mengju Yuan, Yugang Zhang, Ying Zhu, Jingchun Gao, Aifeng Wang, Mingquan He, Jun-Yi Ge, Yisheng Chai Affiliations: Chongqing University, Shanghai University Link: http://arxiv.org/abs/2604.17333v1 Summary: This paper employs the AC magnetostriction coefficient as a sensitive bulk probe to investigate the dynamic behavior of superconducting/normal (S/N) domain walls in the intermediate state of the type-I superconductor lead. While conventional magnetic susceptibility measurements are dominated by surface barriers and overdamped flux motion, exhibiting Debye-type relaxation, the magnetostriction response reveals distinctly different quasi-resonance characteristics: the imaginary part exhibits a frequency-dependent sign reversal, while the real part shows non-monotonic evolution. This phenomenon originates from the collective oscillation of S/N interfaces driven by eddy currents induced by the AC magnetic field within normal domains, which can be quantitatively explained by a modified damped harmonic oscillator model incorporating an intrinsic -π/2 phase shift in the driving force. This discovery unveils a fundamental dynamic channel in the superconducting modulated phase and establishes the AC magnetostriction coefficient as an effective tool for probing hidden interfacial dynamics.\n5. Static and Dynamic Electronic Properties and the Possible Magnetic Structure of the $4f^3$-$Γ_6$ System NdCo2Zn$_{18}$Ga$_2$ Investigated Using $^{59}$Co Nuclear Quadrupole Resonance Relevance Score: 3.6067 Authors: Tetsuro Kubo, Atsushi Sasaki, Keita Murooka, Hisashi Kotegawa, Rikako Yamamoto, Takahiro Onimaru, Hideki Tou Link: http://arxiv.org/abs/2604.17416v1 Summary: This study employs (^{59})Co nuclear quadrupole resonance (NQR) to microscopically investigate the static and dynamic electronic properties and magnetic structure of the NdCo₂Zn₁₈Ga₂ compound, which undergoes an antiferromagnetic phase transition at (T_N = 1.5) K. Although no discernible changes are observed in the NQR spectrum across the transition temperature, the nuclear spin-lattice relaxation rate (1/T_1) exhibits a clear anomaly peak at (T_N). Analysis of the Nd magnetic moments indicates that their internal fields cancel at the Co sites, resulting in no splitting or broadening of the NQR spectrum. If the nearest-neighbor Nd moments are antiferromagnetically arranged, this configuration suggests that Ga substitution relieves magnetic frustration in the parent system, thereby raising the antiferromagnetic transition temperature from 0.53 K in the undoped case to 1.5 K. Additionally, the temperature dependence of (1/T_1) follows a power law at low temperatures, indicating the opening of a partial gap in the antiferromagnetic ordered state. Combining the NQR spectral and relaxation data, two possible arrangements of Nd moments are proposed, one of which can be explained solely by nearest-neighbor antiferromagnetic interactions. This scenario is consistent with macroscopic observations that after Ga substitution, the magnetic entropy increases, the transition becomes second-order, and aligns with mean-field calculations. This study provides crucial microscopic evidence for understanding how Ga substitution stabilizes antiferromagnetic order and suppresses the possible two-channel Kondo effect in this system.\n6. Localized Exciton Emission with Spontaneous Circular Polarization in NiPS3/WSe2 Heterostructures Relevance Score: 3.3480 Authors: Adi Harchol, Shahar Zuri, Rajesh Kumar Yadav, Nirman Chakraborty, Idan Cohen, Tomasz Woźniak, Thomas Brumme, Thomas Heine, Doron Naveh, Efrat Lifshitz Affiliations: Yonsei University, Technion, University of Warsaw, Technische Universität Dresden, Technical University of Darmstadt, Bar-Ilan University, Helmholtz-Zentrum Dresden-Rossendorf Link: http://arxiv.org/abs/2604.17409v1 Summary: By employing low-temperature micro-photoluminescence and magneto-photoluminescence spectroscopy, the optical response of few-layer NiPS₃/WSe₂ heterostructures was investigated, revealing multiple sharp excitonic peaks absent in the individual constituent materials, which are attributed to excitons confined within the WSe₂ layers by the interface-induced potential barrier. These excitons exhibit spontaneous circular polarization under zero external magnetic field, indicating a magnetic proximity effect arising from uncompensated spins at the NiPS₃ interface. Magneto-optical measurements further demonstrate nonlinear Zeeman splitting, supporting the existence of an interfacial exchange field. Density functional theory calculations confirm that the photoluminescence originates intralayer and reveal interfacial orbital hybridization and alterations in spin texture. The results demonstrate that integrating two-dimensional semiconductors with layered antiferromagnets enables the manipulation of valley polarization and spin degrees of freedom, offering new avenues for chiral light sources and magnetically tunable optoelectronic devices.\n7. Crystallographic Challenges in Microscopy of Multidomain Spinel Materials Relevance Score: 3.3447 Authors: Ninon Scherz, Shashwat Anand, Colin Ophus, Tucker Holstun, Mary Scott, Tara P. Mishra, Gerbrand Ceder Link: http://arxiv.org/abs/2604.17561v1 Summary: This paper systematically evaluates the capabilities of STEM-HAADF imaging and Fourier filtering techniques in characterizing multi-domain spinel structures and their antiphase boundaries in δ-DRX materials. Based on electron microscopy simulations and group theory analysis, the projections of eight crystallographic spinel variants along the [110] zone axis are classified, revealing that interfaces formed by different variant pairs exhibit four distinct fringe discontinuity patterns in Fourier-filtered images, with one type of paired boundary being completely undetectable by atomic-scale STEM-HAADF. Furthermore, simulation results indicate that regions appearing disordered or layered in experiments may actually originate from low-energy {100} antiphase interfaces inclined relative to the [110] observation direction. The study demonstrates that in symmetry-lowering phase transitions occurring on a coherent lattice, complex domain structures resulting from local rearrangements require careful interpretation of two-dimensional projection micrographs; otherwise, inclined domain boundaries can be easily misidentified as disordered or layered regions. These findings highlight the inherent crystallographic challenges in microstructural characterization of multi-domain systems, holding critical implications for understanding the relationship between electrochemical performance and structure in δ-DRX materials.\n8. Orbital glass conceals missing magnetic entropy in a relativistic Mott insulator Relevance Score: 3.3225 Authors: Ilija K. Nikolov, Rong Cong, Adrien Rosuel, Stephen Carr, Ian R. Fisher, Dmitri E. Feldman, Adrian Del Maestro, Chandrasekhar Ramanathan, Vesna F. Mitrović Link: http://arxiv.org/abs/2604.17540v1 Summary: This study utilizes phase-sensitive nuclear magnetic resonance to independently probe the responses of spin and orbital degrees of freedom, revealing an orbital glass state in the relativistic Mott insulator Ba₂NaOsO₆: the orbital order parameter exhibits a globally zero average but with a significant distribution, while short-range orbital order persists up to 380 K. As the temperature decreases toward the magnetic phase transition, the orbital order parameter acquires a nonzero average, forming an orbital nematic state that breaks the rotational symmetry of the lattice and directly induces long-range magnetic order. The configurational entropy of this orbital glass state accounts for the magnetic entropy previously missing in thermodynamic measurements, resolving a long-standing puzzle concerning this material. This study elucidates the mechanism by which orbital order, under strong spin-orbit coupling, drives magnetic phase transitions through the generation of directional order rather than long-range orbital order, providing a new approach to understanding hidden order in quantum materials with coupled multiple degrees of freedom.\n9. Designer metal-free altermagnetism in honeycomb two-dimensional frameworks Relevance Score: 3.1286 Authors: Hongde Yu, Thomas Brumme, Thomas Heine Affiliations: Helmholtz Zentrum Dresden-Rossendorf, Yonsei University, Technische Universität Dresden Link: http://arxiv.org/abs/2604.17386v1 Summary: By reducing the point group symmetry of the triangulene-derived radical monomer from D₃h to C₂v while preserving the bipartite lattice and selectively breaking inversion symmetry, researchers achieved designable metal-free altermagnetism in a honeycomb two-dimensional organic framework. Spin-polarized density functional theory calculations revealed strong antiferromagnetic coupling (~ −130 meV), a 17 meV d-wave spin splitting at the M point, and a 1.26 eV Mott–Hubbard gap, all fully consistent with Lieb\u0026rsquo;s theorem. A minimal tight-binding model demonstrated that anisotropic nearest-neighbor hopping, arising from direction-dependent π-orbital overlaps, is the microscopic origin of both the spin splitting and altermagnetism. Biaxial compressive strain further enhanced the spin splitting to 27 meV. These results establish a general approach to realizing room-temperature organic altermagnets and open a pathway to carbon-based altermagnetism by engineering inversion symmetry breaking.\n10. Modern Solid Electrolytes for All-Solid-State Batteries: Materials Chemistry, Structure, and Transport Relevance Score: 3.0545 Authors: Denys Butenko, Mustafa Khan, Liusuo Wu, Jinlong Zhu Affiliations: Southern University of Science and Technology Link: http://arxiv.org/abs/2604.17380v1 Summary: This review systematically analyzes the structure–property relationships of three major classes of inorganic solid electrolytes—oxides, sulfides, and halides—from the perspective of crystalline symmetry to amorphous local polyhedral arrangements. The findings reveal that fast-ion conduction does not depend solely on composition or crystallographic diffusion pathways, but rather results from the coupled interplay of multiple factors, including framework topology, site energy distribution, defect chemistry, bottleneck response, and local anionic flexibility. Oxides achieve transport within chemically robust yet geometrically constrained frameworks; sulfides broaden low-energy migration pathways through soft and highly polarizable lattices; while halides leverage densely packed anionic sublattices, nearly degenerate lithium environments, and mixed-anion coordination to ensure efficient transport while enhancing oxidative stability and cathode compatibility. Based on these comparisons, the review proposes that long-range ionic transport does not proceed along a single ideal pathway but represents the macroscopic manifestation of statistically connected, low-barrier local migration events. Finally, experimental and computational methods required for establishing multiscale structure–property relationships are discussed, along with an overview of strategies for designing future transport-active frameworks that simultaneously optimize conductivity, stability, and processability.\n","permalink":"https://nickelates.uk/en/posts/2026-04-19-arxiv-daily/","summary":"\u003cblockquote\u003e\n\u003cp\u003e\u003cstrong\u003eDaily Overview\u003c/strong\u003e:\nToday\u0026rsquo;s highlights focus on the pairing mechanism of the bilayer nickelate La₃Ni₂O₇ high-temperature superconductor, revealing that a unified framework based on the \u0026ldquo;gene principle\u0026rdquo; and the \u0026ldquo;cooperative Fermi surface rule\u0026rdquo; can be naturally extended to this bilayer multi-orbital system. Two dominant antiferromagnetic superexchange channels cooperatively generate a stable s± superconducting state, offering new perspectives for understanding the unique electronic environment of nickel-based superconductivity. Additionally, although not directly targeting nickelates, today\u0026rsquo;s list includes studies on the G-type antiferromagnetic order and hidden altermagnetism in Rb₁₋ₓV₂Te₂O, as well as the microscopic detection of hidden magnetic entropy in the orbital glass state of Ba₂NaOsO₆. The physical mechanisms explored in these studies—such as spin-orbit coupling, hidden order, and d-wave spin splitting—are closely related to the core issues currently addressed in the field of nickel-based superconductivity, including pairing symmetry, spin fluctuations, and orbital effects, warranting cross-disciplinary attention.\n\u003cstrong\u003earXiv submission processing window\u003c/strong\u003e: 2026-04-19 00:56 to 2026-04-19 18:01 UTC.\u003c/p\u003e","title":"arXiv Daily: nickelate superconductors 2026-04-19"},{"content":" Daily Overview: Dear readers, welcome to today\u0026rsquo;s briefing on research in the nickel-based superconductivity field. Although today\u0026rsquo;s list lacks studies directly targeting nickelates, several works have made significant progress in areas such as low-dimensional electronic states, topological phase transitions, charge density waves, and altermagnetism. These topics share potential methodological and physical connections with issues currently central to nickel-based superconductivity, such as dimensionality-driven electronic reconstruction, strong correlation effects, and symmetry breaking. Highlights include: the observation of layer-dependent topological phase transitions in WTe₂ thin films, demonstrating how dimensionality regulates band topology through interlayer coupling; the first discovery of a fourfold-periodic charge density wave in isolated NbS₃ single chains, revealing deviations from Luttinger liquid behavior in truly one-dimensional systems; a symmetry-guided transport fingerprint identification route established via the screening of altermagnetic materials; the significant influence of in-plane anisotropy on the magneto-optical properties of FePS₃, illustrating strong structure-optics coupling; and the confirmation of the Berry phase origin of topological transport in polycrystalline FeSi thin films, along with an estimation of the Weyl point separation. These works advance the understanding of low-dimensional and topological quantum states from multiple perspectives, offering valuable insights for exploring the mechanisms of nickel-based superconductivity. arXiv submission processing window: 2026-04-18 04:23 to 2026-04-18 18:36 UTC.\n1. Evolution of topological phases in atomically thin WTe2 films Relevance Score: 3.3617 Authors: Changcang Qiao, Chen-Chia Hsu, Tao Zhang, Zhiming Sun, Dong Qian, Yang-hao Chan, Peng Chen Affiliations: Academia Sinica, Shanghai Jiao Tong University Link: http://arxiv.org/abs/2604.16860v1 Summary: Using angle-resolved photoemission spectroscopy (ARPES) and first-principles calculations, we systematically investigate the electronic structure evolution and topological phase transitions in atomically thin WTe₂ films ranging from monolayer to bulk. Experimental observations reveal that monolayer WTe₂ exhibits an indirect band gap of approximately 55 meV, characteristic of a quantum spin Hall insulator. As the layer number increases, the band gap narrows to about 30 meV in bilayers, while in trilayers the gap closes and the system becomes metallic. First-principles calculations demonstrate that the topological Z₂ invariant oscillates between 1 and 0 with increasing layer number, arising from band-crossing changes induced by interlayer coupling. When the conduction and valence bands come into contact near the Fermi level, the system evolves into a Weyl semimetal, whose topological properties are described by the Chern number. This study directly illustrates the nonmonotonic dependence of topological states on dimensionality and elucidates how layer-driven electronic band reconstruction triggers topological phase transitions in solids.\n2. Charge-Density Waves of Single and Double NbS$_{3}$ Chains Relevance Score: 3.3465 Authors: S. Tanda, S. Kashimoto, H. Yamamoto, K. Inagaki, H. Nobukane, Y. Fukuda Link: http://arxiv.org/abs/2604.16837v1 Summary: This study, for the first time, isolated single-chain and double-chain NbS₃ samples using a carbon nanotube sheath method, and precisely measured atomic spacings via scanning transmission electron microscopy (STEM), enabling direct detection of charge density waves (CDWs) in a truly one-dimensional system. In single-chain samples, an unexpected fourfold-periodic CDW (1/4 b*) was observed, instead of the known threefold-periodic CDW (1/3 b*) in bulk materials, with an average Nb–Nb distance contracted by approximately 6% relative to the structural model, accompanied by discommensurations. Double-chain samples simultaneously exhibited a dimeric structure (1/2 b*) and threefold-periodic CDW in each chain, resembling the quasi-one-dimensional behavior of bulk materials. These results demonstrate that the truly one-dimensional electronic system of NbS₃ is not a Luttinger liquid but a CDW state driven by the Peierls transition; the reduced dimensionality alters the universality class to which the system belongs, providing critical experimental evidence for understanding the true ground state of isolated one-dimensional chains in low-dimensional physics, surpassing previous studies limited to quasi-one-dimensional bulk materials.\n3. Medium-Throughput Evaluation of Transport and Optical Responses in Altermagnets Relevance Score: 3.2119 Authors: Fu Li, Bo Zhao, Vikrant Chaudhary, Shengqiao Wang, Chen Shen, Hao Wang, Hongbin Zhang Affiliations: Jilin University, Technical University of Darmstadt Link: http://arxiv.org/abs/2604.17071v1 Summary: This study develops a medium-throughput first-principles workflow that collects approximately 150 known altermagnetic compounds from the MAGNDATA database to systematically evaluate their transport and optical properties. By combining density functional theory, Wannier interpolation, and symmetry analysis, we investigate linear and nonlinear responses such as the anomalous Hall effect, magneto-optical Kerr effect, and bulk photovoltaic effect. The results show that these responses are strongly constrained by magnetic symmetry and further shaped by spin-orbit coupling, band structure, and inversion symmetry breaking. Representative examples include a finite anomalous Hall response in metallic VNb₃S₆, a giant Kerr rotation in insulating CaIrO₃, and a pronounced shift current in non-centrosymmetric CuFeS₂. These findings establish a symmetry-guided route for identifying experimentally detectable fingerprints and functional transport properties in altermagnetic materials.\n4. Crystal Anisotropy Implications on the Magneto-Optical Properties of van der Waals FePS3 Relevance Score: 3.1571 Authors: Ellenor Geraffy, Kusha Sharma, Shahar Zuri, Faris Horani, Adam K. Budniak, Muhamed Dawod, Yaron Amouyal, Thomas Brumme, Andrea Maricel León, Thomas Heine, Rajesh Kumar, Doron Naveh, Efrat Lifshitz Affiliations: Yonsei University, Technion-Israel Institute of Technology, Universidad de Chile, University of Washington, Bar-Ilan University, Technical University of Dresden, HZDR Link: http://arxiv.org/abs/2604.16912v1 Summary: This paper investigates the influence of in-plane structural anisotropy on the magneto-optical properties of the van der Waals antiferromagnetic material FePS₃. X-ray diffraction confirms that FeS₆ octahedral distortion leads to inequivalent Fe-Fe distances and a higher a/b lattice parameter ratio. Micro-photoluminescence measurements observe four emission bands in both bulk and monolayer FePS₃: an intratomic d-d transition at ~1.24 eV (band A) and three p-d charge transfer transitions at ~1.79 eV, ~2.3 eV, and ~2.56 eV (bands B, C, D, respectively). These emission bands exhibit distinct linear and circular polarization behaviors, and such polarization characteristics are maintained down to the monolayer limit. Density functional theory calculations reveal the electronic structure from bulk to monolayer, identify the origins of the emissions, and explain the differences in polarization responses among the peaks. These results establish a direct structure-optical correlation in FePS₃, highlighting the strong coupling among lattice anisotropy, electronic transitions, and symmetry-selective optical selection rules.\n5. Experimental Signatures of Topological Transport in Polycrystalline FeSi Thin Films Relevance Score: 3.0939 Authors: R. Mantovan, A. Bozhko, V. Zhurkin, A. Bogach, A. Khanas, S. Zarubin, A. Zenkevich, V. Glushkov Affiliations: CNR-IMM, Russian Academy of Sciences, Moscow Institute of Physics and Technology (National research university) Link: http://arxiv.org/abs/2604.17103v1 Summary: A 65 nm thick polycrystalline ε-FeSi film was prepared on a Si(100) substrate via solid-state reaction, and its electronic transport properties were systematically investigated. Below 200 K, the anomalous Hall conductivity σ_{xy}^{AHE} was found to be approximately 14 μS/sq and independent of the longitudinal conductivity, confirming that the anomalous Hall effect originates from a nontrivial Berry phase. This scaling behavior exhibits robustness against the nanoscale (≈40 nm) polycrystalline structure and remains stable across the temperature range where the transport mode transitions from bulk to surface states. Additionally, chiral anomalies were observed in both the anisotropic longitudinal magnetoresistance and the planar Hall effect, further corroborating the nontrivial topological states of ε-FeSi. By correlating the scaled anomalous Hall conductivity with the “quantized” Hall response of Weyl semimetals, the distance between two Weyl points was estimated as (k_{+}^{W}-k_{-}^{W})/(2π) ≈ 0.36. These findings confirm the topological origin of electronic transport in polycrystalline ε-FeSi thin films and reveal their potential as a novel, high-temperature, noble-metal-free Weyl semimetal.\n6. Theoretical and Numerical Efforts in Understanding Modern Experiments on Quantum Magnetism Relevance Score: 3.0175 Authors: Zi Yang Meng, Cristian D. Batista, Shiliang Li Affiliations: Chinese Academy of Sciences, University of Tennessee, Oak Ridge National Laboratory, The University of Hong Kong, Songshan Lake Materials Laboratory, University of Chinese Academy of Sciences Link: http://arxiv.org/abs/2604.16820v1 Summary: This paper advocates for a research paradigm that deeply integrates theory, numerical simulation, and experiment in quantum magnetism studies to address current challenges in the field. The authors note that while quantum magnetism has made significant progress in areas such as exotic quantum phase transitions and spin liquids, researchers in numerical, analytical, and materials experiments often view themselves as the driving force while treating other fields as auxiliary tools. Using the triangular-lattice quantum Ising material TmMgGaO₄ (TMGO) as an example, the article demonstrates how an integrated approach advances understanding. Through large-scale quantum Monte Carlo and thermal tensor renormalization group calculations, combined with quantitative comparison to specific heat and inelastic neutron scattering experiments, the researchers precisely determined the model parameters of TMGO (Δ/J₁ = 0.54), thereby establishing that this material lies in a region with observable clock-ordered and BKT phases, with computational results in high agreement with experimental spectroscopic measurements. This case illustrates that when theory, numerics, and experiment work closely together, it is possible to overcome difficulties in high-dimensional spin liquid candidate materials, such as large uncertainties in model extraction, numerical methods limited by the sign problem, and entanglement growth. The paper concludes by emphasizing that such interdisciplinary integrated thinking is not only crucial for quantum magnetism but also key to advancing the overall development of quantum many-body physics.\n","permalink":"https://nickelates.uk/en/posts/2026-04-18-arxiv-daily/","summary":"\u003cblockquote\u003e\n\u003cp\u003e\u003cstrong\u003eDaily Overview\u003c/strong\u003e:\nDear readers, welcome to today\u0026rsquo;s briefing on research in the nickel-based superconductivity field. Although today\u0026rsquo;s list lacks studies directly targeting nickelates, several works have made significant progress in areas such as low-dimensional electronic states, topological phase transitions, charge density waves, and altermagnetism. These topics share potential methodological and physical connections with issues currently central to nickel-based superconductivity, such as dimensionality-driven electronic reconstruction, strong correlation effects, and symmetry breaking. Highlights include: the observation of layer-dependent topological phase transitions in WTe₂ thin films, demonstrating how dimensionality regulates band topology through interlayer coupling; the first discovery of a fourfold-periodic charge density wave in isolated NbS₃ single chains, revealing deviations from Luttinger liquid behavior in truly one-dimensional systems; a symmetry-guided transport fingerprint identification route established via the screening of altermagnetic materials; the significant influence of in-plane anisotropy on the magneto-optical properties of FePS₃, illustrating strong structure-optics coupling; and the confirmation of the Berry phase origin of topological transport in polycrystalline FeSi thin films, along with an estimation of the Weyl point separation. These works advance the understanding of low-dimensional and topological quantum states from multiple perspectives, offering valuable insights for exploring the mechanisms of nickel-based superconductivity.\n\u003cstrong\u003earXiv submission processing window\u003c/strong\u003e: 2026-04-18 04:23 to 2026-04-18 18:36 UTC.\u003c/p\u003e","title":"arXiv Daily: nickelate superconductors 2026-04-18"},{"content":" Daily Overview: Today\u0026rsquo;s highlights focus on deepening the understanding of the electronic structure of mixed Ruddlesden–Popper nickelates. In [1], the researchers developed an ultrafast magneto-pressure spectroscopy platform capable of operating simultaneously under conditions of up to 40 GPa, a 7 T magnetic field, and temperatures as low as 5 K. This platform was applied to systematically probe the quasiparticle dynamics in the trilayer nickelate Pr₄Ni₃O₁₀. The experiments revealed a pronounced critical slowing down of quasiparticle relaxation near the charge density wave (CDW) transition, which disappeared upon applying pressure. At higher pressures, however, the low-temperature relaxation time increased, exhibiting features characteristic of incipient superconducting correlations. Notably, a magnetic field of up to 7 T had almost no effect on the relaxation behavior, and no vortex-induced pre-bottleneck dynamics were observed. This indicates that any possible superconducting state under the current pressure conditions is not bulk-like, but rather filamentary or strongly inhomogeneous. This work not only provides a new experimental approach to unraveling the competition between superconductivity and intertwined orders in nickelates, but also opens up an important avenue for understanding the microscopic origin of pressure-induced superconductivity. arXiv submission processing window: 2026-04-17 01:12 to 2026-04-17 19:06 UTC.\n1. Ultrafast Magneto-Pressure Spectroscopy and Control of Correlated Phases in a Trilayer Nickelate Relevance Score: 5.0119 Authors: Zhi Xiang Chong, Joong-Mok Park, Shuyuan Huyan, Avinash Khatri, Martin Mootz, Xinglong Chen, Daniel P. Phelan, Liang Luo, Ilias E. Perakis, J. F. Mitchell, Sergey L. Bud\u0026rsquo;ko, Paul C. Canfield, Jigang Wang Affiliations: Ames National Laboratory, Argonne National Laboratory, University of Alabama at Birmingham, Iowa State University Link: http://arxiv.org/abs/2604.16611v1 Summary: This study developed an ultrafast magneto-pressure optical spectroscopy platform capable of operating simultaneously at pressures up to 40 GPa, magnetic fields up to 7 T, and temperatures as low as 5 K, and applied it to investigate the evolution of quasiparticle dynamics under magnetic pressure in the trilayer nickelate Pr₄Ni₃O₁₀. The experiments revealed a pronounced critical slowing down of quasiparticle relaxation near the charge density wave (CDW) transition, which disappears upon the application of pressure. At higher pressures, the low-temperature relaxation time instead becomes longer, consistent with initial superconducting correlation signatures. However, a magnetic field as high as 7 T hardly alters the relaxation behavior, and no vortex-induced pre-bottleneck dynamics—robustly observed in bulk superconducting control samples—was detected, suggesting that any superconducting state under the present pressure conditions is not bulk-like but rather filamentary or strongly inhomogeneous. This magneto-pressure ultrafast capability opens a new pathway for addressing unresolved issues of pressure-induced superconductivity and intertwined orders in correlated quantum materials.\n2. Laser induced surface nitriding of niobium: phase evolution and superconducting behaviour Relevance Score: 4.0677 Authors: J. Frechilla, A. Frechilla, G. F. de la Fuente, A. Larrea, L. A. Angurel, E. Martínez Affiliations: CSIC-Universidad de Zaragoza Link: http://arxiv.org/abs/2604.15981v1 Summary: This study utilized a 1064 nm nanosecond pulsed laser to perform surface nitriding of niobium under controlled nitrogen gas pressures (up to 2.50 bar), and by independently adjusting nitrogen pressure, areal cumulative fluence, and laser irradiance, a laser processing map was established for forming either a mixed phase of β-Nb₂N (hexagonal) and γ-Nb₄N₃±ₓ (tetragonal) or a solely β phase. X-ray diffraction, scanning electron microscopy, and electron backscatter diffraction analyses revealed that when the cumulative fluence exceeded 50 kJ/cm² at 2.50 bar, the near-surface layer formed a nitrogen-rich γ phase via melting, with a β layer beneath it, and deeper still, a band of β grains embedded in the niobium matrix, whose grain size gradually decreased with increasing depth, suggesting formation mechanisms involving thermal gradients and diffusion. When the γ phase dominated, the superconducting critical temperature significantly increased to about 15 K, accompanied by magnetic irreversibility. Under low cumulative fluence (approximately 7.5 kJ/cm² at 1.50–2.50 bar), a uniform nitrided layer composed of submicron β-Nb₂N grains enhanced the surface microhardness by about fourfold. These findings provide fundamental insights into the preparation of Nb-N layers possessing both mechanical strength and superconducting properties via laser-induced nitriding technology.\n3. Antiferromagnetic Dimers in the Parent Phase of a Correlated Kagome Superconductor Relevance Score: 3.9585 Authors: Yifan Wang, Chenchao Xu, Yi Liu, Jinke Bao, Jiayu Guo, Xiaoran Yang, Yuiga Nakamura, Hiroshi Fukui, Taishun Manjo, Daisuke Ishikawa, Alfred Q. R. Baron, Saizheng Cao, Rui Li, Zilong Li, Yanan Zhang, Ruihan Chen, Ming Shi, Huiqiu Yuan, Guanghan Cao, Chao Cao, Yu Song Link: http://arxiv.org/abs/2604.15935v1 Summary: This study experimentally resolves the crystal structure of the charge density wave (CDW) state in the correlated kagome superconductor CsCr₃Sb₅, revealing that it consists of alternating chromium dimers and chromium chains. First-principles calculations indicate that dominant antiferromagnetic exchange interactions exist within the dimers, while the couplings within the chains and between dimers and chains are much weaker. Compared with AV₃Sb₅ (A = K, Rb, Cs), the CDW phase transition in CsCr₃Sb₅ exhibits more pronounced first-order characteristics, and no significant soft phonons or diffuse scattering are observed above the transition temperature. Based on these results, the authors propose that fluctuating antiferromagnetic dimers may play a key role in electronic pairing in the pressure-induced superconducting state.\n4. Fluctuating Pair Density Wave in Finite-temperature Phase Diagram of the $t$-$t^\\prime$ Hubbard Model Relevance Score: 3.7347 Authors: Qiaoyi Li, Yang Qi, Wei Li Link: http://arxiv.org/abs/2604.16293v1 Summary: This study employs the advanced thermal tensor renormalization group (tanTRG) method to systematically map the temperature-doping phase diagram of the t-t′ Hubbard model under both electron and hole doping. On the electron-doped side, a d-wave superconducting (dSC) regime is observed, supporting mechanisms of high-temperature superconductivity; on the hole-doped side, however, no robust dSC is found, replaced instead by a finite-temperature region dominated by strong pair density wave (PDW) fluctuations that may transition into charge density wave (CDW) order upon further cooling. The PDW state manifests as inter-arc pairing with a net momentum near (0,π), distinctly different from the zero-momentum pairing of conventional dSC, and occupies the lower portion of the pseudogap region on the hole-doped side. This finite-temperature phase diagram is consistent with previous ground-state studies, revealing doping-dependent differences in the nodal-antinodal Fermi surface structure: enhanced antinodal spectral weight under electron doping and the formation of Fermi arcs under hole doping. These findings elucidate the origins of pairing instabilities and anomalous electronic states in the Hubbard model, indicating that a single-band model alone is insufficient to fully describe the superconducting behavior on the hole-doped side.\n5. Charge Density Wave Driven Topological Phase Transition in Vortices Relevance Score: 3.2727 Authors: Zhenhua Zhu, Ziqiang Wang, Dong E. Liu Link: http://arxiv.org/abs/2604.15976v1 Summary: We develop a theoretical framework revealing that the phase of a stripe charge density wave (CDW) can modulate the transition of magnetic vortices between topological and conventional states. Based on recent experiments, we propose two candidate mechanisms: in the direct modulation mechanism, the CDW acts as a periodic potential that renormalizes band parameters, potentially inducing topological phase transitions, but it struggles to reproduce the experimentally observed node/antinode symmetry trend without fine-tuning. In contrast, in the inversion symmetry breaking (ISB) mechanism, CDW nodes pinned at vortex centers break local inversion symmetry, allowing mixing between spin-singlet and triplet pairing, leading to a robust topological transition when triplet pairing dominates. Through calculations combining three-dimensional surface states with two-dimensional vortex spectra, we demonstrate that the two-dimensional ISB mechanism is the minimal and most self-consistent explanation. These results indicate that the CDW phase can serve as a local means to control and detect vortex topology, offering a new pathway toward realizing effective p-wave pairing and Majorana zero modes in two-dimensional systems.\n6. Two New Molecular Nitrogen Phases near Megabar Pressures Relevance Score: 3.2525 Authors: Alexander F. Goncharov, Elena Bykova, Iskander Batyrev, Maxim Bykov, Huawei Chen, William Palfey, Mahmood Mohammad, Stella Chariton, Vitali Prakapenka, Jesse S. Smith Affiliations: Carnegie Institution for Science, University of Chicago, Goethe University Frankfurt, Argonne National Laboratory, Howard University, U.S. Army DEVCOM Army Research Laboratory Link: http://arxiv.org/abs/2604.16641v1 Summary: Under pressures approaching a megabar (1 Mbar), molecular nitrogen exhibits a rich structural diversity. In this study, by employing a diamond anvil cell combined with laser heating technology, we heated ζ-N₂ at 78–98 GPa and 1800–2500 K, and successfully synthesized two new molecular nitrogen phases. The first, tζ-N₂, is a polytype of the monoclinic C2/c ζ-N₂ with a tripled c-axis containing 96 atoms per unit cell, potentially corresponding to the previously reported κ-N₂ phase. The second, ξ-N₂, is a previously unknown hexagonal phase (P6cc) with 112 atoms per unit cell, representing the most complex molecular nitrogen structure known to date. The structures of both new phases were determined by single-crystal X-ray diffraction and verified by Raman spectroscopy and first-principles calculations. ξ-N₂ exhibits a columnar channel structure with significant orientational disorder of some molecules. These findings expand the phase diagram of molecular nitrogen at high pressures and reveal the existence of highly complex metastable molecular phases near the polymerization transition region.\n7. Nonequilibrium Cooper quartet generation in superconducting devices Relevance Score: 3.2459 Authors: Luca Chirolli, Alessandro Braggio, Michele Governale Link: http://arxiv.org/abs/2604.16647v1 Summary: This paper proposes coupling conventional superconducting leads and normal metal leads in a double quantum dot system, driven by a non-equilibrium voltage bias, to induce resonance between the vacuum state and the four-electron state under high bias, thereby forming an effective Cooper quadruplet coupling. This approach does not rely on the attractive interaction that is difficult to achieve in equilibrium, but instead utilizes non-equilibrium redistribution to excite the quadruplet subspace originally located in the high-energy regime. The study shows that the peak width of the Andreev current at the resonance point is proportional to the quadruplet coupling strength, and this strength can be tuned by the phase of additional superconducting leads, providing an indirect but clear signature of the quadruplet. Further analysis of current noise and the Fano factor reveals that in the quadruplet resonance region, the autocorrelation and cross-correlation are equal, indicating fast coherent double Cooper-pair oscillations between the double quantum dot and the superconducting leads, rather than ordinary single-pair exchange. This platform can be realized with existing experimental techniques, offering a feasible route for exploring quadruplet correlations and multi-fermion correlated states.\n8. Persistence of large and gate-tunable anisotropic magnetoresistance in an atomically thin antiferromagnet Relevance Score: 3.2111 Authors: Cheol-Yeon Cheon, Kenji Watanabe, Takashi Taniguchi, Alberto F. Morpurgo, Dmitry Lebedev Affiliations: University of Geneva, National Institute for Materials Science Link: http://arxiv.org/abs/2604.15793v1 Summary: In a two-dimensional van der Waals antiferromagnetic semiconductor NiPS3 with a thickness of only 1.3 nm (two layers), researchers achieved controllable rotation of the Néel vector via spin-flip processes and successfully realized electrical readout of the Néel vector using two device structures: transistors and tunnel junctions. They identified two distinct contributions to anisotropic magnetoresistance (AMR): at high carrier densities, non-crystalline AMR dominates (resistivity depends on the angle between the Néel vector and the current direction), while at low carrier densities, crystalline AMR dominates (determined by the angle between the Néel vector and the crystal axes). The amplitude and sign of these two contributions can be continuously tuned by gate voltage, enabling modulation of magnetoresistance from positive to negative. This work establishes a reliable method for probing antiferromagnetic order using AMR in the ultrathin limit, demonstrates that semiconducting van der Waals antiferromagnets serve as a rich platform for studying AMR at atomic thickness, and lays the foundation for developing multifunctional, electrically tunable antiferromagnetic spintronic devices.\n9. Inductance Meets Memory in the Quantum Magnet Mn3Si2Te6 Relevance Score: 3.1605 Authors: Tristan R. Cao, Gabriel Schebel, Arabella Quane, Hengdi Zhao, Yu Zhang, Feng Ye, Longji Cui, Gang Cao Affiliations: Oak Ridge National Laboratory, University of Colorado at Boulder Link: http://arxiv.org/abs/2604.15635v1 Summary: In the nonequilibrium reconstruction of chiral orbital currents, ferromagnetic Mn₃Si₂Te₆ single crystals simultaneously exhibit intrinsic inductance and nonvolatile memristive behavior. Under a magnetic field along the c-axis and at frequencies below approximately 6 Hz, coherent orbital current domains generate clockwise inductive current–voltage loops; whereas at zero or weak magnetic fields and higher frequencies, current-driven first-order reconstruction leads to incomplete inversion of the orbital texture and trapping in metastable states, resulting in a finite residual voltage at zero current that constitutes a nonvolatile memristive effect. These phenomena originate from the slow first-order reconstruction of collective orbital textures across discrete energy barriers, with a time scale on the order of tens of milliseconds. This study establishes chiral orbital currents as quantum state variables that simultaneously encode both reactance and memory functions, opening a pathway for intrinsically reconfigurable, energy-efficient electronics.\n10. Flat-band energy filtering in interacting systems: conditions for improving thermoelectric performances Relevance Score: 3.1551 Authors: F. Cosco, R. Tuovinen, F. Plastina, N. Lo Gullo Link: http://arxiv.org/abs/2604.15684v1 Summary: Employing the nonequilibrium Green\u0026rsquo;s function framework and treating interactions at the Hartree-Fock and GW levels, this paper investigates the electronic transport and thermoelectric properties in two one-dimensional flat-band models: the zigzag chain and the diamond chain. The full thermoelectric coefficients and the figure of merit zT are computed as functions of gate voltage and temperature. The results show that a completely isolated flat band is actually detrimental to thermoelectric performance, because the conductivity vanishes when the chemical potential enters the flat band, rendering the large Seebeck coefficient and the pronounced violation of the Wiedemann-Franz law unphysical. Optimal thermoelectric performance occurs just below the flat-band edge, where the transport function varies most rapidly with energy, consistent with the Mahan-Sofo picture, and requires that the flat band acquire a finite broadening through hybridization with dispersive states. Electron-electron interactions renormalize the flat-band structure, leading to interaction-driven band narrowing and, in the diamond chain, opening a correlation-induced gap between the flat band and the dispersive band near half-filling. Mean-field treatments systematically overestimate zT, highlighting the importance of beyond-mean-field correlation effects for quantitatively reliable predictions of thermoelectric properties in flat-band materials.\n11. Fully compensated and uncompensated ferrimagnetic ferrovalley semiconductors Relevance Score: 3.0824 Authors: Weifeng Xie, Libo Wang, Yunliang Yue, Xiong Xu, Huayan Xia, Hui Wang Affiliations: Hunan University of Technology and Business, Yangzhou University, Central South University Link: http://arxiv.org/abs/2604.15640v1 Summary: This work elucidates the microscopic mechanism underlying the transition from an altermagnet (AM) to a fully compensated ferrimagnet (FC-FIM) driven by uniaxial strain, revealing that the accompanying nonrelativistic valley polarization is positively correlated with the net magnetic moment between magnetic atoms in opposite spin sublattices. Based on this, a noncompensated ferromagnetic monolayer VCrSeTeO is proposed to achieve large intrinsic valley polarization. Under uniaxial strain, spin–orbit coupling (SOC) further enhances the valley polarization to over 400 meV, and this enhancement is explained using SOC perturbation theory. Moreover, a unique anomalous valley Hall effect is uncovered in this ferromagnet, characterized by a reversal of the valley Hall voltage within the same valley. This work provides a strategy for realizing giant valley polarization and offers theoretical guidance for the application of ferromagnetic ferrovalley semiconductors derived from altermagnets in valleytronics.\n12. Atomistic Mechanisms of Stress-Dependent Molten Salt Corrosion in NiCr Alloys Relevance Score: 3.0575 Authors: Hamdy Arkoub, Jia-Hong Ke, Miaomiao Jin Link: http://arxiv.org/abs/2604.16261v1 Summary: The coupled effect of stress on intergranular corrosion in Ni0.75Cr0.25 alloy exposed to FLiNaK molten salt at 800°C under uniaxial tensile (+4%) and compressive (−4%) strain was investigated using reactive molecular dynamics simulations. The results reveal that tensile strain reduces local atomic packing density via elastic expansion, increases excess free volume at grain boundaries, and consequently enhances atomic mobility and molten salt infiltration, significantly accelerating fluorine adsorption and selective dissolution of chromium at grain boundaries, leading to deeper intergranular corrosion. In contrast, compressive strain inhibits intergranular corrosion by promoting the formation of a ridge-like surface layer along grain boundaries, which impedes salt penetration into the underlying alloy. The diffusion coefficient in the grain boundary region is highest under tension, followed by compression, both exceeding that in the unstrained state; however, under compression, mass transport is primarily directed toward the formation of surface ridges rather than inward penetration along grain boundaries. These atomistic mechanisms elucidate how the stress state modulates the grain boundary corrosion behavior of NiCr alloys in molten salt environments.\n13. Inelastic neutron scattering study on the AFM uniform spin-1/2 chain compound CuSb2O6 Relevance Score: 3.0526 Authors: Masashi Hasea, Minoru Soda, Takatsugu Masuda, Shinichi Itoh, Tetsuya Yokoo Link: http://arxiv.org/abs/2604.15608v1 Summary: Inelastic neutron scattering experiments were performed on the antiferromagnetic uniform spin-1/2 chain compound CuSb2O6 powder sample. At 2.5 K, below the Néel temperature (8.7 K), magnetic excitations appeared in the energy range of 1.8 to 13 meV. The energy gap value of 1.8 meV is close to the 1.51 meV obtained from specific heat measurements. At 12.5 K (above TN), the excitations exhibited a gapless feature, indicating that the 1.8 meV gap originates from the anisotropy of spin-wave excitations. The gap excitation was strongest at the scattering vector Q = 0.48 Å⁻¹, corresponding to a Cu-Cu distance of approximately 0.66 nm, which is consistent with the Cu-Cu distance of 0.65562 nm associated with the theoretically strongest interaction Jab. All magnetic excitations can be explained by the uniform XXZ antiferromagnetic chain model, where Jab = 6.437 meV and ΔJab = 0.063 meV, with the 1.8 meV gap arising from a tiny Ising anisotropy (ΔJab/Jab = 0.0098). This result confirms the existence of the energy gap and its anisotropic origin, ruling out other mechanisms such as the spin-Peierls transition.\n14. Disambiguating electrical detection of magnetization dynamics in magnetic insulators Relevance Score: 3.0002 Authors: Hanchen Wang, William Legrand, Shangyuan Wang, Davit Petrosyan, Hiroki Matsumoto, Richard Schlitz, Ka Shen, Pietro Gambardella Link: http://arxiv.org/abs/2604.15999v1 Summary: This study systematically investigates the competitive contributions of spin pumping and spin-torque ferromagnetic resonance (ST-FMR) to electrical detection signals in heavy metal/magnetic insulator heterostructures. Using Pt electrodes with TmIG and BiYIG insulating layers, nonlocal and local device measurements were performed, with control of antenna-detector distance, microwave frequency, and magnetic field direction to separate the two mechanisms: spin pumping voltage arises from exponentially decaying propagating spin waves, while ST-FMR voltage originates from weakly distance-dependent inductive coupling. Experiments show that the voltage undergoes a sign reversal when magnetization rotates from out-of-plane to in-plane, but this reversal does not directly reflect magnon chirality; rather, it results from the competition between the two effects. In low-damping films, propagating spin waves dominate the long-distance response, whereas in high-damping systems, ST-FMR contributions become prominent. Additionally, inhomogeneous spin wave modes suppress spin pumping, causing signals to be dominated by ST-FMR. This research provides a unified framework for interpreting electrical signals from magnetization dynamics in magnetic insulators, resolves sign ambiguity, and offers guidance for designing low-loss magnonic devices.\n","permalink":"https://nickelates.uk/en/posts/2026-04-17-arxiv-daily/","summary":"\u003cblockquote\u003e\n\u003cp\u003e\u003cstrong\u003eDaily Overview\u003c/strong\u003e:\nToday\u0026rsquo;s highlights focus on deepening the understanding of the electronic structure of mixed Ruddlesden–Popper nickelates. In [1], the researchers developed an ultrafast magneto-pressure spectroscopy platform capable of operating simultaneously under conditions of up to 40 GPa, a 7 T magnetic field, and temperatures as low as 5 K. This platform was applied to systematically probe the quasiparticle dynamics in the trilayer nickelate Pr₄Ni₃O₁₀. The experiments revealed a pronounced critical slowing down of quasiparticle relaxation near the charge density wave (CDW) transition, which disappeared upon applying pressure. At higher pressures, however, the low-temperature relaxation time increased, exhibiting features characteristic of incipient superconducting correlations. Notably, a magnetic field of up to 7 T had almost no effect on the relaxation behavior, and no vortex-induced pre-bottleneck dynamics were observed. This indicates that any possible superconducting state under the current pressure conditions is not bulk-like, but rather filamentary or strongly inhomogeneous. This work not only provides a new experimental approach to unraveling the competition between superconductivity and intertwined orders in nickelates, but also opens up an important avenue for understanding the microscopic origin of pressure-induced superconductivity.\n\u003cstrong\u003earXiv submission processing window\u003c/strong\u003e: 2026-04-17 01:12 to 2026-04-17 19:06 UTC.\u003c/p\u003e","title":"arXiv Daily: nickelate superconductors 2026-04-17"},{"content":" Daily Overview: Today\u0026rsquo;s highlights focus on deepening the understanding of the superconducting mechanism in bilayer Ruddlesden-Popper nickelates. [1] By stabilizing (La,Pr)₃Ni₂O₇ superconducting thin films and combining X-ray absorption with resonant inelastic X-ray scattering, it was directly observed that superconductivity emerges only when the out-of-plane d_{z²}-p_z-d_{z²} interlayer hybridization becomes coherent, accompanied by the suppression of static spin order and strongly damped spin excitations. This reveals a microscopic picture in which interlayer orbital hybridization and correlation strength jointly shape the superconducting window. Meanwhile, [12] although not directly targeting nickelates, its discovery in the two-dimensional Fermi-Hubbard model of a universal magnetic energy scale J* that decreases linearly with doping, and uniformly determines the spin stiffness, bimagnon frequency, and the onset temperature of the pseudogap, provides a key theoretical framework for understanding the connection between doped antiferromagnetism and the pseudogap in nickel-based superconductors. arXiv submission processing window: 2026-04-15 20:10 to 2026-04-16 19:47 UTC.\n1. Interlayer hybridization enables superconductivity in bilayer nickelates Relevance Score: 5.8561 Authors: Shilong Zhang, Meng Zhang, Qilin Luo, Zihao Tao, Hsiao-Yu Huang, Kunhao Li, Ganesha Channagowdra, Jie Li, Junchi Fu, Di-Jing Huang, Yanwu Xie, Yi Lu, Yingying Peng Link: http://arxiv.org/abs/2604.14701v2 Summary: By stabilizing bilayer nickelate (La,Pr)₃Ni₂O₇ superconducting thin films with a protective capping layer and employing X-ray absorption and resonant inelastic X-ray scattering spectroscopy, this study directly probes the evolution of electronic structures across insulating, superconducting, and metallic states. Experimental and theoretical analyses reveal that the in-plane d_{x²-y²} states constitute an itinerant electron backbone, whereas superconductivity emerges only when the out-of-plane d_{z²}-p_z-d_{z²} interlayer hybridization becomes coherent, accompanied by suppression of static spin order and the appearance of strongly damped spin excitations. Oxygen stoichiometry and epitaxial strain jointly regulate this interlayer channel, confining the superconducting phase to a narrow window of interlayer coherence and correlation strength. These findings elucidate the microscopic prerequisites for superconductivity in bilayer nickelates and provide a multi-orbital framework to describe its emergent mechanism.\n2. Fermi-liquid versus non-Fermi-liquid/\u0026lsquo;strange-metal\u0026rsquo; fits to the electrical resistivity in the quantum critical magnetic regime of an unconventional superconductor Relevance Score: 3.9993 Authors: W. Knafo, T. Thebault, K. Somesh, G. Lapertot, G. Knebel, D. Braithwaite, D. Aoki Link: http://arxiv.org/abs/2604.14952v1 Summary: In the heavy fermion paramagnet UTe₂, unconventional superconductivity emerges near a magnetic field-induced metamagnetic quantum phase transition. This study measured the resistivity of two UTe₂ samples of different quality under a magnetic field tilted approximately 35–40° from the b-axis toward the c-axis, and fitted the data using the Fermi liquid function ρ = ρ₀ + AT² and the non-Fermi liquid/singular metal function ρ = ρ₀ + AₙTⁿ, respectively. The results show that near the superconducting phase induced by fields exceeding 40 T, the non-Fermi liquid fitting extracts an unphysical negative residual resistivity ρ₀ \u0026lt; 0, revealing a possible recovery of \u0026ldquo;hidden\u0026rdquo; Fermi liquid T² behavior at low temperatures. This finding underscores the importance of studying high-quality samples with low residual resistivity to confirm or rule out the underlying quantum critical behavior masked by superconductivity.\n3. Two pathways to break the insulating state in a correlated transition metal oxide Relevance Score: 3.8630 Authors: Joel Kuttruff, Ritwika Mandal, Marina Servol, Céline Mariette, Hiroko Tokoro, Shin-ichi Ohkoshi, Rodolphe Sopracase, Hervé Cailleau, Laurent Cario, Etienne Janod, Maciej Lorenc, Vinh Ta Phuoc Affiliations: European Synchrotron Radiation Facility, Nantes Université, Université de Rennes, Université de Tours, University of Tokyo, University of Tsukuba Link: http://arxiv.org/abs/2604.14415v1 Summary: Using broadband optical spectroscopy and density functional theory calculations, two pathways for breaking the insulating state in the correlated transition metal oxide Ti₃O₅ are investigated. The room-temperature insulating β phase is found to consist of one-dimensional zigzag chains formed by two types of titanium dimers (Ti1-Ti1 and Ti3-Ti3), giving rise to orbital-selective valence bonds. During the thermally induced phase transition at approximately 460 K, the Ti3-Ti3 dimers dissociate, triggering an insulator-metal transition accompanied by significant orbital electronic redistribution and the emergence of a narrow Drude peak. Furthermore, photoinduced spectra reveal that applying pressure at room temperature drives a distinctly different insulator-metal transition pathway, which does not involve structural symmetry breaking but instead arises from competition between intra-dimer and inter-dimer transitions, ultimately resulting in metallicity along the c-axis. These combined results demonstrate that Ti₃O₅ is a typical correlated transition metal oxide whose electronic state evolution requires simultaneous consideration of both electron correlation and orbital interactions.\n4. High-temperature charge-4e superconductivity in SU(4) interacting fermions Relevance Score: 3.6746 Authors: Shao-Hang Shi, Zhengzhi Wu, Jiangping Hu, Zi-Xiang Li Affiliations: University of Chinese Academy of Sciences, Chinese Academy of Sciences, University of Oxford Link: http://arxiv.org/abs/2604.15056v1 Summary: This study proposes a sign-problem-free SU(4) interacting fermion model and, using unbiased quantum Monte Carlo simulations, reveals the emergence of a charge-4e superconducting state in a two-dimensional system. The zero-temperature phase diagram shows that in the strong coupling regime, the ground state is charge-4e superconductivity rather than conventional charge-2e superconductivity; at finite temperatures, charge-2e pairing is strictly short-ranged, while charge-4e superconductivity forms via a Berezinskii-Kosterlitz-Thouless transition, with the superfluid stiffness exhibiting a universal jump consistent with 4e charge condensation, and the transition temperature Tc increases approximately linearly with interaction strength, achieving high-temperature four-electron superconductivity. Spectral analysis reveals a significant pseudogap above Tc caused by strong phase fluctuations. This work establishes the first numerically exact microscopic model of charge-4e superconductivity, providing key theoretical guidance for realizing this novel quantum state in moiré materials and ultracold atomic systems.\n5. Discovery of an odd-parity f-wave charge order in a kagome metal Relevance Score: 3.6339 Authors: Jiangchang Zheng, Caiyun Chen, Ruiqin Fu, Luca Buiarelli, Zihan Lin, Fazhi Yang, Tianhao Guo, Ganesh Pokharel, Andrea Capa Salinas, Sen Zhou, Turan Birol, Stephen D. Wilson, Junzhang Ma, Daniel J. Schultz, Xianxin Wu, Berthold Jäck Link: http://arxiv.org/abs/2604.14538v1 Summary: Using high-resolution scanning tunneling microscopy and angle-resolved photoemission spectroscopy, this study discovered an odd-parity f-wave charge bond order in the kagome metal CsV₃Sb₅. This order breaks spatial inversion symmetry while preserving translational symmetry, and is stabilized by spontaneously opening a spectral gap at previously overlooked Dirac points, providing a textbook realization of Dirac fermion dynamical mass generation and parity breaking in the Gross-Neveu model. This f-wave order emerges as an intermediate phase, reaching maximum intensity at around 14 K, yet abruptly disappears below 10 K, suggesting a subsequent transition into a “hidden” electronic state invisible to local STM probes. This discovery establishes odd-parity charge order as a new phase of matter and reveals its embedding within the hierarchical complex of correlated electronic orders in the kagome lattice.\n6. Long-range spin-polarized Josephson effect in ballistic S/F/S junctions with precessing magnetization Relevance Score: 3.5897 Authors: E. S. Andriyakhina, M. Mansouri, M. Breitkreiz, P. W. Brouwer Link: http://arxiv.org/abs/2604.14390v1 Summary: This paper presents a theory of long-range spin-polarized superconducting correlations induced by a uniformly precessing magnetization in ballistic N/F/S and S/F/S junctions. By employing a rotating reference frame and a scattering approach to handle the time-dependent Hamiltonian, the energy spectrum and non-equilibrium distribution of Andreev bound states are derived, and contributions from the continuum spectrum are incorporated to precisely compute the Josephson current. In the short-junction limit, both discrete and continuum spectra determine the current, and under large precession angles, the non-equilibrium distribution leads to a strongly non-sinusoidal current-phase relation. For fully polarized half-metallic junctions, precession switches the junction from an “off” state with no subgap current to an “on” state with finite Andreev conductance and Josephson current. For small precession angles, the current is proportional to the square of the tilt angle and can be resonantly enhanced when the precession frequency matches the ferromagnetic resonance. In the partially polarized case, opposite-spin correlations exhibit short-range oscillations, while equal-spin correlations possess a long-range component, manifesting as a long-range superconducting proximity effect in multi-dimensional structures.\n7. Type II Lifshitz invariant and optically active Higgs mode in time-reversal symmetry broken superconductors Relevance Score: 3.5648 Authors: Raigo Nagashima, Chihiro Mamiya, Naoto Tsuji Affiliations: University of Tokyo, Karlsruhe Institute of Technology, RIKEN Link: http://arxiv.org/abs/2604.15054v1 Summary: This paper proposes a novel \u0026ldquo;second-type Lifshitz invariant\u0026rdquo; for describing time-reversal symmetry breaking superconductors. Unlike the conventional \u0026ldquo;first-type Lifshitz invariant,\u0026rdquo; which is even under particle-hole transformation, the second-type Lifshitz invariant changes sign under particle-hole transformation and appears only in time-reversal symmetry breaking superconductors. Through Ginzburg-Landau theory analysis, the authors find that this invariant enables the Higgs mode to couple linearly with the electromagnetic field, making it visible in optical conductivity spectra. The study provides a group-theoretical classification of the irreducible co-representations of order parameters that permit the second-type Lifshitz invariant based on magnetic point groups, and validates the theoretical results through numerical calculations on various multiband superconductor models with broken time-reversal symmetry. The numerically computed optical conductivity spectra are consistent with the group-theoretical analysis. This work establishes a class of time-reversal symmetry breaking superconductors featuring a generic optically active Higgs mode.\n8. Phonon mediated spin-spin interactions Relevance Score: 3.5486 Authors: J. Fransson Link: http://arxiv.org/abs/2604.14731v1 Summary: This paper investigates phonon-mediated spin-spin interactions between local magnetic moments in insulators and proposes a derivation method based on the Kubo formalism with effective spin-phonon coupling. The study reveals that such interactions can be decomposed into symmetric and antisymmetric anisotropic components: the symmetric component exists for all phonon types, while the antisymmetric component (analogous to the Dzyaloshinskii-Moriya interaction) emerges only in structures with broken inversion symmetry, which can account for the weak ferromagnetism observed in chiral metal oxides such as CuO and CoO. Regarding temperature dependence, the interaction is nearly temperature-independent at low temperatures but increases linearly with temperature at high temperatures; spatially, it exhibits an oscillatory power-law decay with inter-nuclear distance, with distinct oscillation patterns for the symmetric and antisymmetric components. The paper concludes that phonon-mediated spin-spin interaction constitutes a universal and quantifiable long-range magnetic coupling mechanism in insulators, and its symmetry conditions along with temperature and spatial behaviors are of significant importance for understanding ordering phenomena in magnetic insulators.\n9. Josephson phase shift and diode effect due to the inverse spin Hall effect Relevance Score: 3.5451 Authors: Gen Tatara, Yositake Takane, Aurelien Manchon Link: http://arxiv.org/abs/2604.14521v1 Summary: We theoretically investigate the direct and inverse spin Hall effects in superconductor-normal metal-superconductor junctions with inversion-symmetric spin-orbit coupling. The supercurrent can induce a spin Hall effect, generating static spin accumulations of opposite polarization on both edges of the junction, similar to the behavior in normal conductors. For the inverse effect, we consider a spatially inhomogeneous static magnetic field and find that it produces an anomalous phase shift via the inverse spin Hall effect. When higher harmonics are taken into account, this phase shift leads to a Josephson diode effect—namely, a critical current that differs depending on the direction of the current. Unlike mechanisms relying on Rashba spin-orbit coupling, this scheme does not require breaking structural inversion symmetry; the spin current itself breaks both inversion and time-reversal symmetries, which is sufficient to induce the diode effect. This research provides a new avenue for phase control in Josephson devices using magnetic textures or spin injection.\n10. Reversable phase transitions in ferroic two-dimensional Nb2O2I4 through optically excited coherent phonons Relevance Score: 3.5287 Authors: Chuanlin Liu, Dan Liu, Jie Guan, Chao Lian Link: http://arxiv.org/abs/2604.14894v1 Summary: This study employs real-time time-dependent density functional theory (rt-TDDFT) to investigate photoinduced phase transitions in the two-dimensional ferroelectric material Nb₂O₂I₄. By customizing laser pulses to activate specific coherent phonon modes, particularly anharmonic atomic distortions of the A1-1 and A1-2 modes at the Γ point, intralayer polarization reversal can be achieved. Fine-tuning the laser parameters further excites other phonon modes at the Y and Γ points, inducing non-equilibrium atomic dynamics that lead to three previously unreported antiferroelectric phases and one ferrielectric phase. Importantly, these photoinduced phases can be reversibly restored to the initial ferroelectric state through appropriate techniques, such as applying a specific laser pulse for the ferrielectric phase or thermal activation for the antiferroelectric phases. This controllable reversibility among multiferroic phases positions two-dimensional Nb₂O₂I₄ as a promising candidate for next-generation electronic memory applications.\n11. Wide-field magnetic imaging of shielding-current-driven vortex rearrangement under local heating using diamond quantum sensors Relevance Score: 3.5191 Authors: Ryoei Ota, Shunsuke Nishimura, Koki Honda, Takeyuki Tsuji, Taro Yamashita, Takayuki Iwasaki, Mutsuko Hatano, Kento Sasaki, Kensuke Kobayashi Link: http://arxiv.org/abs/2604.14578v1 Summary: This study utilized fully aligned diamond nitrogen-vacancy (NV) centers for wide-field magnetic imaging to quantitatively measure the stray magnetic field distribution of vortices in NbN thin films. By employing localized laser heating and progressively varying the external magnetic field, continuous imaging was performed over 100 minutes, capturing the spatial and temporal rearrangement of vortex configurations in real time. Observations revealed that vortices in the center of the heated region underwent directional motion, while the configuration in the outer region remained unchanged, consistent with the weakening of pinning forces due to local heating and the Lorentz force direction induced by the screening current generated by the magnetic field variation. Further temperature-dependent experiments showed that pinning weakened with increasing temperature, and vortex hopping under thermal perturbations was isotropic. By calculating the screening current distribution, the estimated magnitude of the Lorentz force matched the observed direction of vortex motion, providing a quantitative basis for explaining the vortex rearrangement mechanism. This study elucidates the physical mechanism of collective vortex motion driven by the synergistic effect of local heating and magnetic field variation, offering a proof-of-concept for applications such as vortex exclusion in sensitive regions of superconducting devices and vortex positioning in vortex-based devices.\n12. Universal magnetic energy scale in the doped Fermi-Hubbard model Relevance Score: 3.4862 Authors: Radu Andrei, Ivan Morera, Jonathan B. Curtis, Immanuel Bloch, Eugene Demler Affiliations: Munich Center for Quantum Science and Technology, Ludwig-Maximilians-Universität, Max-Planck-Institut für Quantenoptik, ETH Zürich Link: http://arxiv.org/abs/2604.15234v1 Summary: This study describes the coupling between antiferromagnetic magnons and doped holes in the two-dimensional square-lattice Fermi-Hubbard model through a self-consistent diagrammatic formalism, revealing a universal magnetic energy scale (J^) that decreases linearly with doping. Originating from the competition between antiferromagnetic superexchange and frustration induced by hole motion, this energy scale uniformly determines both the static spin correlations and dynamic responses of the system: the spin stiffness and the frequency of the two-magnon peak scale with an identical doping dependence, as confirmed by lattice-modulation spectroscopy experiments and spin correlation length measurements. Furthermore, (J^) sets the onset temperature of the pseudogap phenomenon, satisfying (k_B T^* = c J^*); meanwhile, another lower energy scale governs the stability of Néel order at low temperatures, closely linked to quasiparticle properties and ultimately driving the system into an incommensurate spin-density-wave phase at finite doping. This analysis indicates that the stability of the commensurate antiferromagnetic phase can be experimentally tuned by introducing disorder or low-frequency noise to enhance quasiparticle broadening.\n13. Abrikosov vortices in altermagnetic superconductors Relevance Score: 3.4778 Authors: A. A. Mazanik, F. S. Bergeret Link: http://arxiv.org/abs/2604.15204v1 Summary: This paper employs the Ginzburg-Landau theory to investigate the penetration behavior of an external magnetic field in superconductors with a collinear d-wave alternating magnetic order. The key finding is that the magnetic field no longer generates circular Abrikosov vortices but instead forms elliptical vortices, with their long axis oriented along the crystal axis exhibiting the largest spin splitting. When the component of the magnetic field parallel to the alternating magnetic Néel vector is reversed, the vortices reorient to another crystal axis with maximal spin splitting. This effect arises from the effective mass anisotropy induced by the alternating magnetic order, which is controlled by the coupling between the external magnetic field and the Néel vector. Furthermore, in superconducting thin films containing pinning defects, the magnetization curves display nonreciprocity upon reversal of the magnetic field along the Néel vector direction, due to the differing interaction energies of vortices and antivortices. These results deepen the understanding of the coexistence mechanism of alternating magnetism and superconductivity, applicable to intrinsic materials or superconductor/alternating magnet hybrid structures, and open new experimental avenues for exploring superfluid vortices in such systems.\n14. Lattice dynamics and complete polarization analysis of Raman-active modes in LaInO$_3$ Relevance Score: 3.4334 Authors: Jonas Rose, Hai Nguyen, Moritz Meißner, Zbigniew Galazka, Roland Gillen, Georg Hoffmann, Oliver Brandt, Manfred Ramsteiner, Markus R. Wagner, Hans Tornatzky Affiliations: Swansea University, Leibniz-Institut für Kristallzüchtung, Leibniz-Institut im Forschungsverbund Berlin e. V. Link: http://arxiv.org/abs/2604.15156v1 Summary: This study combines polarization angle-resolved Raman spectroscopy with density functional theory to conduct a comprehensive analysis of the Raman-active phonon modes in orthorhombic LaInO₃. Through backscattering experiments on multiple crystal plane orientations and complete symmetry analysis, the 19 observed Raman-active zone-center phonons are assigned to irreducible representations of the D₂h point group. A multidimensional hyperspectral fitting procedure successfully extracts the relative Raman tensor elements from heavily overlapping angular dependencies of scattering intensities. First-principles calculations provide phonon dispersions along high-symmetry directions, density of states, and atomic displacement patterns, with computed frequencies in good agreement with experimental results. This work provides a complete experimental and theoretical foundation for understanding the lattice dynamics of LaInO₃, which is beneficial for optimizing its application as a transparent conductive oxide substrate.\n15. Nonmagnetic-magnetic Transitions in Rutile RuO2 Relevance Score: 3.3965 Authors: Yue-Fei Hou, Jiajun Lu, Xinfeng Chen, Gui-Bin Liu, Ping Zhang Link: http://arxiv.org/abs/2604.14764v1 Summary: Through density functional theory calculations, this study reveals the electronic correlation- and strain-dependent magnetic behavior in bulk rutile RuO₂. Within a reasonable range of Hubbard parameters, RuO₂ exhibits multiple altermagnetic (AM) phases with distinct spin magnetic moment magnitudes. When strain that significantly alters the unit cell volume is applied, the ground state of RuO₂ can transition between a nonmagnetic state without spin splitting and a magnetic state with band spin splitting. This nonmagnetic-to-magnetic transition is directly related to changes in the unit cell volume, while 4d electron correlations and the density of electronic states in the nonmagnetic state jointly influence the stability of the magnetic state, with the mechanism explainable by the generalized Stoner model. These findings not only demonstrate the rich physical phenomena in 4d electron correlation systems but also provide new insights into understanding the coexistence of nonmagnetic and altermagnetic states in experiments, while preserving the potential of RuO₂ for spintronic applications.\n16. Towards Non-van der Waals 2D Topological Insulators Relevance Score: 3.3959 Authors: Mani Lokamani, Gustav Bihlmayer, Gregor Michalicek, Daniel Wortmann, Stefan Blügel, Rico Friedrich Affiliations: Forschungszentrum Jülich, Helmholtz-Zentrum Dresden-Rossendorf, RWTH Aachen University, Technische Universität Dresden Link: http://arxiv.org/abs/2604.14976v1 Summary: This study systematically investigates the influence of spin-orbit coupling (SOC) on the electronic structures of non-van der Waals two-dimensional materials AgBiO₃, NaBiO₃, SbTlO₃, and their derivative system SbPbO₃ using first-principles calculations. The results reveal that the SOC effect is weak in AgBiO₃ and NaBiO₃, primarily due to the conduction band bottom being composed of Bi s orbitals (with zero angular momentum). In contrast, SbTlO₃ exhibits a conduction band splitting of up to 229 meV near the K point, accompanied by band inversion. By substituting Tl with Pb to obtain SbPbO₃, this band inversion feature is tuned to near the Fermi level, resulting in a topological gap of approximately 200 meV. Calculations of topological invariants and analysis of edge states in zigzag and armchair nanoribbons confirm its topologically nontrivial nature. This work lays the foundation for systematic studies of non-van der Waals two-dimensional topological insulators.\n17. Electronic Signature of Melting Onset in Polycrystalline Copper at Extreme Conditions Relevance Score: 3.3519 Authors: Edna R. Toro, Tobias Held, Armin Bergermann, Megan Ikeya, Maximilian Maigler, Eric R. Sung, Dirk O. Gericke, Mianzhen Mo, Baerbel Rethfeld, Siegfried H. Glenzer, Benjamin K. Ofori-Okai Link: http://arxiv.org/abs/2604.15491v2 Summary: Using single-shot terahertz time-domain spectroscopy, we measured the transient conductivity of polycrystalline copper thin films on a picosecond timescale after femtosecond laser excitation. Combining this with two-temperature molecular dynamics simulations, we identified a distinct electronic signature at the onset of melting. The experiments show that before melting occurs, grain boundary scattering significantly limits electron transport, whereas the melting process suppresses this scattering channel. When melting initiates at interfaces such as grain boundaries, the conductivity exhibits a transient increase, directly marking the phase transition onset. This phenomenon indicates that the relaxation stages of ions and electrons in non-equilibrium laser-driven materials are tightly coupled, allowing optical measurements to resolve different stages of melting, with conductivity changes serving as an electronic and optical signature of melting initiation.\n18. New frontiers in quantum science and technology using van der Waals Josephson junctions Relevance Score: 3.3443 Authors: Joydip Sarkar, Ayshi Mukherjee, Amit Basu, Ritajit Kundu, Arijit Kundu, Mandar M. Deshmukh Link: http://arxiv.org/abs/2604.15276v1 Summary: Josephson junctions based on van der Waals materials (vdW JJs) have developed rapidly in recent years, opening new frontiers in quantum science and technology. These junctions leverage the rich library of two-dimensional materials—such as graphene, transition metal dichalcogenides, and high-temperature superconductors—to achieve atomically sharp interfaces through layer-by-layer stacking, overcoming the material incompatibility issues inherent in conventional epitaxial growth. Compared with traditional oxide-barrier junctions, vdW JJs offer multiple unique tuning capabilities: electrostatic gating enables continuous modulation of the supercurrent and current-phase relation, significantly reducing crosstalk from flux tuning; interlayer twist angles allow engineering of electronic wave functions and superconducting order parameters—for instance, realizing magic-angle superconductivity in twisted bilayer graphene or generating chiral topological superconducting order at twisted high-temperature superconductor interfaces; and time-periodic driving can construct Floquet Hamiltonians, enabling non-equilibrium quantum states. These characteristics endow vdW JJs with superior performance in superconducting qubits, quantum-noise-limited amplifiers, single-photon thermal radiation sensors, and hybrid quantum sensors, while remaining compatible with existing circuit quantum electrodynamics architectures. However, scalable fabrication remains the primary challenge for practical applications. This review systematically summarizes current device and physics advancements and suggests that integrating twistronics with topology could redefine superconducting quantum technology, provided that the scalability bottleneck is overcome.\n19. Disentangling the ferroelectric phases of epitaxial hafnia Relevance Score: 3.3420 Authors: Johanna van Gent Gonzalez, Ewout van der Veer, Yulei Li, Daniel A. Chaney, Beatriz Noheda Link: http://arxiv.org/abs/2604.15081v1 Summary: This study employed synchrotron grazing-incidence diffraction combined with a large-area detector to perform comprehensive three-dimensional reciprocal space mapping of epitaxial hafnium oxide thin films, aiming to clarify the controversy surrounding their ferroelectric phases. The diffraction patterns, temperature dependencies, and electrical responses of rhombohedral-phase (R-phase) films grown on SrTiO₃ substrates and orthorhombic-phase (OIII-phase) films grown on YSZ substrates were directly compared. The results show that the R-phase films perfectly match the simulated rhombohedral structure in reciprocal space, exhibit no phase transition up to 800°C, and display an initial remanent polarization of 40 μC/cm² without a wake-up effect. In contrast, the OIII-phase films exhibit characteristic triangular peak splitting, transform into a cubic phase above 700°C via a reversible tetragonal intermediate phase, and achieve a remanent polarization of 20 μC/cm² after waking up. These findings provide conclusive evidence that the two phases are distinct ferroelectric phases and reveal differences in functional properties dictated by their crystal symmetries.\n20. Anomalous Platinum and Oxygen Transport during Electroforming of NbOx Memristors Relevance Score: 3.2723 Authors: Shimul Kanti Nath, Sanjoy Kumar Nandi, Xiao Sun, Sujan Kumar Das, Bin Gong, Nicholas J. Ekins-Daukes, Deepak Mishra, Mahesh P. Suryawanshi, William D. A. Rickard, Songyan Yin, Michael P. Nielsen, Robert G. Elliman Affiliations: The Australian National University, Curtin University, Jahangirnagar University, University of New South Wales Link: http://arxiv.org/abs/2604.14680v1 Summary: This study reveals anomalous ion transport phenomena during the electroforming process of Pt/NbOx/Nb2O5/Pt memristors through experiments and modeling. Conventional views hold that electroforming only generates oxygen vacancy filaments, while noble metal electrodes such as platinum remain chemically inert. However, time-of-flight secondary ion mass spectrometry (ToF-SIMS) three-dimensional imaging shows that highly correlated oxygen-rich and platinum-rich filaments form after electroforming: oxygen extends from the Nb2O5 layer through NbOx to the Pt top electrode, while platinum simultaneously penetrates the oxide stack along the same path in the opposite direction, forming micrometer-scale filaments. Finite element and lumped-element electrothermal models indicate that device operation in the negative differential resistance (NDR) mode generates localized Joule heating and high-frequency thermal cycles, which significantly enhance oxygen migration and enable thermally assisted platinum diffusion along vacancy-rich pathways. This finding challenges the conventional assumption of platinum electrode inertness, reveals a previously unrecognized metal ion migration mechanism in NbOx memristors, and underscores the critical influence of post-electroforming electrodynamic behavior on filament chemical composition, stability, and device reliability.\n","permalink":"https://nickelates.uk/en/posts/2026-04-16-arxiv-daily/","summary":"\u003cblockquote\u003e\n\u003cp\u003e\u003cstrong\u003eDaily Overview\u003c/strong\u003e:\nToday\u0026rsquo;s highlights focus on deepening the understanding of the superconducting mechanism in bilayer Ruddlesden-Popper nickelates. [1] By stabilizing (La,Pr)₃Ni₂O₇ superconducting thin films and combining X-ray absorption with resonant inelastic X-ray scattering, it was directly observed that superconductivity emerges only when the out-of-plane d_{z²}-p_z-d_{z²} interlayer hybridization becomes coherent, accompanied by the suppression of static spin order and strongly damped spin excitations. This reveals a microscopic picture in which interlayer orbital hybridization and correlation strength jointly shape the superconducting window. Meanwhile, [12] although not directly targeting nickelates, its discovery in the two-dimensional Fermi-Hubbard model of a universal magnetic energy scale J* that decreases linearly with doping, and uniformly determines the spin stiffness, bimagnon frequency, and the onset temperature of the pseudogap, provides a key theoretical framework for understanding the connection between doped antiferromagnetism and the pseudogap in nickel-based superconductors.\n\u003cstrong\u003earXiv submission processing window\u003c/strong\u003e: 2026-04-15 20:10 to 2026-04-16 19:47 UTC.\u003c/p\u003e","title":"arXiv Daily: nickelate superconductors 2026-04-16"},{"content":" Daily Overview: Today\u0026rsquo;s highlights focus on an in-depth understanding of the electronic structure of mixed Ruddlesden-Popper nickelates. One study systematically reveals the evolution of the pressure required for the superconducting phase with bandwidth and filling in the bilayer nickelate La₃Ni₂O₇ family by partially substituting La with Nd to alter NiO₆ octahedral tilting, thereby reducing bandwidth, and simultaneously introducing Sr for hole doping to regulate band filling. The study also identifies multiple characteristic resistance anomalies in the non-superconducting state, which may correspond to charge density wave and spin density wave orders competing with superconductivity, indicating that independently controlling bandwidth and filling is crucial for understanding the unconventional superconducting mechanism and its competing orders in this system. arXiv submission processing window: 2026-04-15 02:58 to 2026-04-15 19:49 UTC.\n1. Controlling the Band Filling and the Band Width in Nickelate Superconductors Relevance Score: 5.7509 Authors: M. Kriener, C. Terakura, A. Kikkawa, Z. Liu, H. Murayama, M. Nakajima, Y. Fujishiro, S. Sasano, R. Ishikawa, N. Shibata, Y. Tokura, Y. Taguchi Link: http://arxiv.org/abs/2604.13875v1 Summary: This study employs high-pressure synthesis and hydrostatic high-pressure transport techniques to systematically modulate the bandwidth and band filling in the bilayer nickelate La₃Ni₂O₇ family, aiming to investigate their effects on superconductivity and non-superconducting state properties. By partially substituting La with smaller Nd (which increases NiO₆ octahedral tilting and reduces bandwidth), the pressure required for the superconducting phase is significantly elevated; conversely, co-introducing Sr for hole doping reverses this trend, lowering the onset pressure of superconductivity. In the non-superconducting state, up to three characteristic resistance anomalies are observed, evolving with pressure, likely corresponding to charge density wave and spin density wave orders that compete with superconductivity. A comprehensive comparison of phase diagrams across samples with different compositions indicates that independent control of bandwidth and filling is key to unraveling the mechanism of unconventional superconductivity and its competing orders in this system.\n2. Anomalous Low-temperature Magnetotransport in Kagome Metal CsCr$_3$Sb$_5$ under Pressure Relevance Score: 3.9544 Authors: Zikai Zhou, Wenyan Wang, Deng Hu, Zheyu Wang, Ying Kit Tsui, Tsz Fung Poon, Zhiwei Wang, Swee K. Goh Link: http://arxiv.org/abs/2604.13553v1 Summary: Through systematic magnetotransport experiments under hydrostatic pressure on CsCr₃Sb₅ single crystals, researchers investigated the anomalous hump previously observed in resistivity at approximately 30 K (T₃). The results reveal that below T₃, there is an anomalous increase in the Hall coefficient, multiband characteristics, and a pressure-enhanced anomalous Hall effect, behaviors reminiscent of those in the charge density wave state of the sister compound CsV₃Sb₅. Further mobility spectrum analysis indicates that the high-mobility carrier contribution increases under high pressure, directly correlating with the enhancement of the anomalous Hall effect. These findings suggest that T₃ may signal the emergence of a new type of electronic order, calling for further studies to elucidate its microscopic mechanism.\n3. $μ$SR study of time-reversal symmetry constraints and bulk superfluid response in Li$_{0.95}$FeAs Relevance Score: 3.7882 Authors: Rustem Khasanov, Hubertus Luetkens, Nikolai D. Zhigadlo Link: http://arxiv.org/abs/2604.14376v1 Summary: This paper reports zero-field (ZF) and transverse-field (TF) muon spin rotation/relaxation measurements on the high-pressure self-flux-grown superconductor Li0.95FeAs with Tc ≈ 16.0 K. ZF-μSR data show no significant change in electronic relaxation rate upon cooling through Tc, providing no evidence for time-reversal symmetry breaking in the superconducting state. TF-μSR measurements reveal a well-developed vortex response with strong flux pinning and negligible nonsuperconducting contributions, confirming bulk superconductivity. From the second moment of the internal field distribution, the low-temperature in-plane magnetic penetration depth is determined to be λ_ab = 245(15) nm. The temperature dependence of the normalized superfluid density can be fitted by an effective two-gap model with gap values Δ1 = 2.0(2) meV and Δ2 = 0.7(2) meV. Quantitative comparison with band weights from angle-resolved photoemission spectroscopy (ARPES) indicates that the μSR response is dominated by Fermi surface sheets hosting moderate and small superconducting gaps, whereas the band with the largest gap contributes only about 3% of the total superfluid density and thus is not resolved in our analysis. Together, these results establish Li0.95FeAs as a bulk multigap superconductor without significant time-reversal symmetry breaking and demonstrate how μSR can reconcile gap-scale discrepancies between bulk-sensitive and surface-sensitive probes in this multiband system.\n4. Crystal structure effects on vortex dynamics in superconducting MgB$_2$ thin films Relevance Score: 3.6155 Authors: Clemens Schmid, Anton Pokusinskyi, Markus Gruber, Corentin Pfaff, Theo Courtois, Alexander Kasatkin, Karine Dumesnil, Stephane Mangin, Thomas Hauet, Oleksandr Dobrovolskiy Link: http://arxiv.org/abs/2604.14022v1 Summary: This study investigates the influence of two microstructural defects—columnar growth in textured films and buffer layer roughness in single-crystal films—on vortex dynamics in MgB₂ thin films. Current–voltage curves measured at approximately 0.25 times the critical temperature exhibit multiple-step features in both types of films. Combined with time-dependent Ginzburg–Landau simulations, experimental and simulation results consistently indicate that the resistive transition is dominated by the formation and growth of normal domains rather than flux flow instability. Single-crystal films exhibit stronger pinning due to transverse modulation of the superconducting order parameter induced by the MgO buffer layer, along with lower thermal boundary resistance, leading to a higher supercurrent-carrying capability, pinning activation energy approximately twice that of textured films, and more pronounced I–V curve steps. The study reveals that the microstructure of the film and the film–buffer layer interface jointly determine the resistive transition behavior, providing critical insights for the design of superconducting devices requiring controllable dissipation under high transport currents.\n5. Giant Room-Temperature Third-Order Electrical Transport in a Thin-Film Altermagnet Candidate Relevance Score: 3.5736 Authors: Hongyu Chen, Peixin Qin, Ziang Meng, Guojian Zhao, Kai Chen, Chuanying Xi, Xiaoning Wang, Li Liu, Zhiyuan Duan, Sixu Jiang, Jingyu Li, Xiaoyang Tan, Jinghua Liu, Jianfeng Wang, Huiying Liu, Chengbao Jiang, Zhiqi Liu Affiliations: Chinese Academy of Sciences, University of Science and Technology of China, Beihang University Link: http://arxiv.org/abs/2604.13893v1 Summary: This study observes a giant room-temperature third-order electrical transport response, including both longitudinal and transverse (Hall) effects, in (101)-oriented RuO₂ thin films—an altermagnetic candidate material—whose mechanism is intimately related to the Berry curvature and quantum metric of quantum geometric quantities. Altermagnets simultaneously break time-reversal–semi-lattice translation and parity–time symmetries, resulting in vanishing net magnetization while T-odd and T-even quantum geometric quantities coexist. Through combined symmetry analysis, scaling analysis, and first-principles calculations, the experiments reveal that these nonlinear transports originate from quantum metric quadrupole moments, Berry curvature quadrupole moments, electric-field-induced second-order Berry curvature, and extrinsic disorder scattering mechanisms. The third-order Hall effect exhibits a strong correlation with the altermagnetic order; its sign reverses after field cooling, thereby serving as an effective tool for probing the Néel vector. This work not only confirms altermagnetism in 8-nm-thick RuO₂ films but also demonstrates altermagnets as a versatile platform for studying quantum geometry and constructing quantum electronic and spintronic devices.\n6. Strain-Mediated Lattice Reconstruction Enhances Ferromagnetism in Cr2Ge2Te6/WTe2 van der Waals Heterobilayers Relevance Score: 3.5644 Authors: Franz Herling, Mireia Torres-Sala, Dorye L. Esteras, Charlotte Evason, Motomi Aoki, Marcos Rosado, Kapil Gupta, Bernat Mundet, Kai Xu, J. Sebastián Reparaz, Kenji Watanabe, Takashi Taniguchi, Dimitre Dimitrov, Vera Marinova, Ivan A. Verzhbitskiy, Goki Eda, José H. Garcia, Stephan Roche, Juan. F. Sierra, Sergio O. Valenzuela Affiliations: Agency for Science Technology and Research (A*STAR), Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Universitat Autònoma de Barcelona, Institució Catalana de Recerca i Estudis Avançats (ICREA), National University of Singapore, Catalan Institute of Nanoscience and Nanotechnology (ICN2), Bulgarian Academy of Sciences, National Institute for Materials Science Link: http://arxiv.org/abs/2604.13640v1 Summary: In Cr₂Ge₂Te₆/WTe₂ van der Waals heterostructures, magnetic transport measurements, interfacial microscopic characterization, and first-principles calculations reveal that the proximity effect of WTe₂ significantly enhances the ferromagnetism of Cr₂Ge₂Te₆. The anomalous Hall effect across multiple devices shows that the Curie temperature is elevated to over 150 K, more than double that of pristine CGT, while maintaining perpendicular magnetic anisotropy and enhanced coercive field. High-resolution interface imaging confirms atomically sharp interfaces with no elemental interdiffusion, and control experiments rule out artifacts from processing or stray fields. Theoretical calculations indicate that interfacial charge transfer drives CGT into a conductive state, while WTe₂ induces lattice distortion in CGT, strengthening exchange interactions and magnetocrystalline anisotropy. This work reveals that strain-mediated lattice reconstruction is an effective strategy for tuning high-temperature magnetic order in two-dimensional heterostructures and clarifies that changes within the magnetic layer dominate the proximity effect.\n7. Revisiting 9Be Nuclear Magnetic Resonance in UBe13: Itinerant-Localized Duality and Possible Fermi Surface Reconstruction at High Magnetic Field Relevance Score: 3.5403 Authors: Rintaro Matsuki, Shoko Minami, Hisashi Kotegawa, Hisatomo Harima, Yoshinori Haga, Etsuji Yamamoto, Yoshichika Onuki, Hideki Tou Link: http://arxiv.org/abs/2604.13576v1 Summary: This study presents 9Be nuclear magnetic resonance (NMR) measurements on single crystals of the heavy-fermion superconductor UBe13, covering a magnetic field range of 0.5 to 8 T at various angles. By considering the non-centrosymmetric space group, a nuclear spin Hamiltonian incorporating the classical dipolar field, Knight shift, and anisotropic electric quadrupole interaction was established, successfully reproducing the complex NMR line shapes at high fields and correcting deviations from low-field parameters extrapolated to high fields. Analysis reveals that the comparison between the Knight shift and classical dipolar shift provides microscopic evidence for itinerant-localized duality in UBe13. Additionally, an anomaly in the Knight shift near 6 T suggests a partial reconstruction of multiple Fermi surfaces under high magnetic fields. This work deepens the understanding of the microscopic properties of both the normal and superconducting states of this material.\n8. Low temperature Spin freezing and Diffuse Magnetic Correlations in Tb$_{2}$Zr$_{2-x}$Ti$_{x}$O$_{7}$ (x = 0, 0.5) Relevance Score: 3.5058 Authors: Sujata Singh, Leon Carstens, M. Duc Le, R. Klingeler, C. S. Yadav Affiliations: STFC Rutherford Appleton Laboratory, Indian Institute of Technology Mandi, Heidelberg University Link: http://arxiv.org/abs/2604.13864v1 Summary: In this study, polycrystalline samples of Tb₂Zr₂O₇ and Tb₂Zr₁.₅Ti₀.₅O₇ were synthesized by solid-state reaction. X-ray diffraction confirmed that the parent compound adopts a defect fluorite structure, which transforms to a pyrochlore phase upon Ti doping. Magnetic susceptibility measurements reveal no long-range magnetic order below 0.4 K for both samples, but field-dependent spin freezing behaviors emerge below approximately 1.25 K and 1.05 K, respectively. AC susceptibility data indicate slow spin relaxation processes at low temperatures (below about 20 K). Inelastic neutron scattering detects broad diffuse scattering signals, suggesting the dominance of short-range magnetic correlations at low temperatures, which are attributed to local structural distortions and persistent spin fluctuations. Curie-Weiss fitting yields negative Weiss temperatures, indicating predominantly antiferromagnetic interactions among Tb³⁺ ions. Collectively, the experimental evidence shows that Tb₂Zr₂O₇ and its Ti-doped counterpart exhibit correlated magnetic states strongly influenced by chemical disorder, with spin dynamics and short-range correlations governed by the competition between local structural disorder and magnetic interactions.\n9. Tunable bifurcation of magnetic anisotropy and bi-oriented antiferromagnetic order in kagome metal GdTi3Bi4 Relevance Score: 3.4387 Authors: Jianfeng Guo, Shiyu Zhu, Runnong Zhou, Ruwen Wang, Yunhao Wang, Jianping Sun, Zhen Zhao, Xiaoli Dong, Jinguang Cheng, Haitao Yang, Jiang Xiao, Hong-Jun Gao Affiliations: University of Chinese Academy of Sciences, Chinese Academy of Sciences, Fudan University Link: http://arxiv.org/abs/2604.14012v1 Summary: This study employs ultra-low-temperature magnetic force microscopy with a vector magnetic field to directly observe magnetic domain evolution in the quasi-one-dimensional kagome antiferromagnet GdTi₃Bi₄, revealing significant in-plane anisotropy along the a-axis. At approximately 2 K, a tunable bifurcation transition of the anisotropy is discovered, where the a-axis anisotropy splits into two special orientations deviating by ±7° from the high-symmetry direction, forming a hidden bi-orientational in-plane antiferromagnetic order. By modulating the vector magnetic field, the characteristics of the bifurcated anisotropy are clearly delineated, identifying three distinct in-plane domain phases in the transverse magnetic field phase diagram. These results not only deepen the understanding of the tunable bifurcation of anisotropy in GdTi₃Bi₄ but also provide a new avenue for the development of antiferromagnetic spintronics.\n10. Strong Correlation Drives Zero-Field Josephson Diode Effect Relevance Score: 3.4082 Authors: Yiheng Sun, Zhenyu Zhang, James Jun He Link: http://arxiv.org/abs/2604.14045v1 Summary: This study, by constructing a Josephson junction model incorporating the Hubbard U term and odd electron numbers, reveals a new mechanism for the zero-field Josephson diode effect (JDE) driven by strong electronic correlations. It finds that strong correlations spontaneously break time-reversal symmetry and mirror symmetry, forming φ junctions with energy minima at ±φ, thereby enabling nonreciprocal superconducting critical currents in the absence of magnetic order. Spin-orbit coupling only breaks SU(2) symmetry but does not determine the diode polarity, which differs from the conventional magnetic chiral mechanism. Further results show that applying a small Zeeman field can efficiently modulate the JDE via the strong correlation magnetic response, with the efficiency peaking at the level-crossing transition point. This discovery establishes strong electronic correlations as an independent mechanism for nonreciprocal superconducting transport and expands the understanding of the origin of the supercurrent diode effect.\n11. Topologically non-trivial gap function and topology-induced time-reversal symmetry breaking in a superconductor with singular dynamical interaction Relevance Score: 3.3900 Authors: Yue Yu, Andrey V. Chubukov Link: http://arxiv.org/abs/2604.14295v1 Summary: In superconductors with singular dynamical interactions, by adding a repulsive Hubbard interaction with a finite energy cutoff to the critical boson pairing model, the authors find that the originally subdominant topologically nontrivial gap function becomes the ground-state solution when the parameters (cutoff energy and boson mass) lie within a specific range. The gap equation is solved on the Matsubara axis, and the real-frequency complex gap function is obtained via Padé approximation, allowing analysis of the transition between topologically trivial (vortex-free) and nontrivial (vortex-containing) solutions. The study shows that these two topologically distinct gap functions cannot evolve continuously and must pass through an intermediate phase where time-reversal symmetry is spontaneously broken (TRSB), and the gap function becomes complex. This TRSB phase originates from the topological difference rather than from symmetry-breaking-induced topology. The numerical phase diagram reveals a finite region of the TRSB phase within a specific parameter window, whose extent increases as the cutoff decreases. This finding provides a universal strategy for realizing topologically nontrivial superconducting states and topology-driven TRSB by tuning the cutoff and boson mass, parameters that are experimentally accessible via gate voltage, doping, or pressure.\n12. Extreme Terahertz Nonlinear Phononics by Coherence-Imprinted Control of Hybrid Order Relevance Score: 3.3717 Authors: Liang Luo, Avinash Khatri, Martin Mootz, Tao Jiang, Liu Yang, Zijing Chen, Chuankun Huang, Zhi Xiang Chong, Joongmok Park, Ilias E. Perakis, Zhiwei Wang, Yugui Yao, Dao Xiang, Yong-Xin Yao, Jigang Wang Affiliations: Iowa State University, U.S. Department of Energy Link: http://arxiv.org/abs/2604.13429v1 Summary: In Ta₂NiSe₅, the research team reported an extreme terahertz nonlinear phononics mechanism, where the core lies in leveraging highly sensitive non-equilibrium electronic correlation baths under coherent driving to substantially amplify lattice nonlinearities. Using terahertz two-dimensional spectroscopy as a coherent tomography tool, they resolved approximately 30 distinct multi-order quantum pathways, including high-order harmonic phonon generation, multi-quantum coherence, and multi-wave anharmonic cross-mode mixing, whose density and complexity exceed the limits of conventional lattice responses. These high-order nonlinear signals completely vanish above about 100 K, indicating the existence of an electronic correlation scale defined by coherently imprinted mixed electron-phonon order, which governs the sustainability of high-order quantum correlations and nonlinear pathways. This study establishes a new route for coherent control via correlation-enhanced, phonon-anchored periodic Hamiltonian engineering and for verifying periodic driving states through multi-correlation coherent tomography.\n13. The ground ytterbium doublet in h-YbMnO3 and the related low-temperature peculiarities of the compound Relevance Score: 3.3601 Authors: S. A. Klimin, N. D. Molchanova, N. N. Kuzmin, E. S. Sektarov, Lihua Yin, M. N. Popova Affiliations: Russian Academy of Sciences, Chinese Academy of Sciences Link: http://arxiv.org/abs/2604.13651v1 Summary: A detailed temperature-dependent study of the optical f‑f transitions of Yb³⁺ ions in hexagonal YbMnO₃ (h‑YbMnO₃) was performed using Fourier transform spectroscopy, determining the splitting Δ₀(T) of the ground-state Kramers doublet of Yb³⁺ ions at the 4b site as a function of temperature. The results indicate that below the Néel temperature T_N = 87 K, this function reflects the dynamic behavior of the manganese magnetic moments, demonstrating that the ytterbium subsystem is magnetized by the magnetic field generated by the ordered manganese subsystem. The excitation of the upper level of the ground-state split doublet plays an important role in the low-temperature dynamics of the crystal. Using the Δ₀(T) function, the temperature dependence of the Yb(4b) magnetic moment was calculated, which agrees well with neutron scattering data; meanwhile, the contribution of Yb(4b) to the heat capacity clearly explains the origin of the Schottky anomaly in the Cp(T) curve. Based on this, a phase transition scenario for h‑YbMnO₃ is proposed, in which the energy gain of the ytterbium system plays a key role.\n14. Divergent spin conductivity on the verge of ferromagnetic quantum criticality Relevance Score: 3.3337 Authors: Sondre Duna Lundemo, Asle Sudbø Affiliations: Norwegian University of Science and Technology Link: http://arxiv.org/abs/2604.14286v1 Summary: This paper demonstrates that the spin conductivity of metals near a ferromagnetic quantum critical point exhibits divergent fluctuation corrections, an effect arising from critical spin fluctuations that constitutes the spin counterpart of the Aslamazov-Larkin paraconductivity theory in superconductivity. The study derives the spin current within the linear response framework based on an effective action under the Gaussian fluctuation approximation in an easy-plane magnetic anisotropy system, and verifies the self-consistency of this spin transport theory by satisfying the Ward identity and the vanishing of spin stiffness in the normal state. The critical enhancement of spin conductivity is interpreted as a manifestation of incipient spin superfluidity in the quantum critical regime, a picture further supported by an intuitive representation based on the current-loop representation of easy-plane ferromagnets.\n15. Topological anisotropic non-Fermi liquid from a Berry-dipole semimetal Relevance Score: 3.3139 Authors: Konstantinos Ladovrechis Link: http://arxiv.org/abs/2604.14146v2 Summary: Using large-N_f analysis and renormalization group epsilon expansion, this study investigates the behavior of three-dimensional Berry-dipole semimetals at the topological quantum critical point between a Hopf insulator and a trivial insulator under long-range Coulomb interactions. The results show that Coulomb interactions, acting as a relevant perturbation, drive a spatially anisotropic non-Fermi liquid phase characterized by vanishing quasiparticle weight and the breakdown of Fermi liquid behavior. The fermion anisotropy parameter in this phase flows toward a strong anisotropy fixed point under renormalization group flow, leading to anisotropic scaling between momentum and energy and yielding a nonzero fermion anomalous dimension. Physical observables such as density of states, specific heat, compressibility, diamagnetic susceptibility, and optical conductivity exhibit power-law scaling relations deviating from Fermi liquid theory. Furthermore, Berry curvature flux is significantly enhanced under interactions, and although it loses quantization, it can serve as an observable signature via enhancement of the nonlinear Hall conductivity. This work proposes a novel phase of matter driven synergistically by topology and interactions.\n16. Quantum Charge-4e Superconductivity and Deconfined Pseudocriticality in the Attractive SU(4) Hubbard Model Relevance Score: 3.2780 Authors: Zhou-Quan Wan, Huan Jiang, Xuan Zou, Shiwei Zhang, Shao-Kai Jian Link: http://arxiv.org/abs/2604.14289v1 Summary: This study systematically investigates the zero-temperature phase diagram of the attractive SU(4) Hubbard model using large-scale quantum Monte Carlo simulations, overcoming the technical challenge of infinite variance in charge-4e correlation calculations. The results reveal the coexistence of charge-2e and charge-4e superconducting phases. As the interaction strength increases, charge-2e correlations are suppressed and eventually vanish, while charge-4e correlations converge with system size and remain robust, signaling the emergence of an electron quadrupling condensate phase. Interestingly, the single-electron excitation remains gapped across the charge-2e to charge-4e phase transition, and the scaling behavior of charge-2e correlations deviates from the conventional Landau-Ginzburg-Wilson description. This phenomenon can be naturally understood within a fractionalization framework, where the physical charge-2e order parameter is constructed from composite fields coupled to an emergent non-Abelian gauge structure. On this basis, the authors formulate an Sp(4) gauge-Higgs theory, which achieves deconfined quantum pseudo-criticality via fixed-point collision, and the one-loop critical exponents quantitatively agree with the quantum Monte Carlo numerical results. This work not only establishes charge-4e superconductivity as a genuine zero-temperature quantum phase and provides a simple model amenable to numerically exact treatment for future studies, but also reveals a new route to superconducting criticality beyond the conventional paradigm.\n17. Spin-mediated hysteretic switching of unidirectional charge density waves by rotating magnetic fields Relevance Score: 3.2094 Authors: Zichao Chen, Shiyu Zhu, Kailin Xu, Ruwen Wang, Ningning Wang, Jianfeng Guo, Yunhao Wang, Xianghe Han, Zhongyi Cao, Jianping Sun, Hui Chen, Haitao Yang, Jinguang Cheng, Ziqiang Wang, Hong-Jun Gao Affiliations: University of Chinese Academy of Sciences, Chinese Academy of Sciences, Boston College Link: http://arxiv.org/abs/2604.14002v1 Summary: In the magnetic kagome metal GdTi3Bi4, the research team achieved deterministic hysteretic switching of unidirectional charge density wave (CDW) orientation by rotating an in-plane magnetic field. Using atomically resolved scanning tunneling microscopy/spectroscopy, two types of 3a₀ × 1a₀ CDW domains (Q1 and Q2) with a 60° orientation difference were observed, separated by atomically sharp domain walls. Rotating the magnetic field drove reversible transitions between these two configurations, exhibiting a robust C₂-symmetric phase diagram and significant hysteresis. This hysteretic switching is mediated by field-dependent reorientation of antiferromagnetic spins, which modulates the electronic charge order through spin-lattice coupling, forming a tunable energy landscape with stable and metastable states. This finding not only demonstrates the switching of CDW configurations using an in-plane magnetic field but also reveals the coupling mechanism between CDW and magnetic fields, providing new insights and a platform for developing spin-mediated multistate spin-charge coupled memory and programmable quantum devices.\n18. Hole and spin dynamics in an anti-ferromagnet close to half filling Relevance Score: 3.1662 Authors: Magnus Callsen, Jens H. Nyhegn, Kristian Knakkergaard Nielsen, Georg M. Bruun Link: http://arxiv.org/abs/2604.14039v1 Summary: 针对反铁磁体靠近半填充时的空穴与自旋动力学问题，该研究发展了一种守恒图解方法，结合自洽Born近似与随机相位近似，描述强排斥作用及小空穴掺杂条件下的费米-哈伯德模型。研究发现，掺杂会在布里渊区形成四个由磁极化子构成的椭圆空穴口袋，且随着空穴浓度增加，这些极化子逐渐被阻尼；同时，反铁磁的磁振子谱因空穴引入的磁阻挫而软化和展宽，导致反铁磁关联减弱，与近期量子模拟实验一致。进一步计算晶格调制的响应后，研究成功复现了实验中同相与反相调制的定性差异，该差异此前被解读为赝能隙物理的信号。结果表明，自旋与电荷自由度的复杂竞争以及赝能隙相的出现，可从低掺杂区域出发通过系统理论得到有效分析。\n19. Continuous correlated states and dual-flatness in a moiré heterostructure Relevance Score: 3.1539 Authors: Mohammed M. Al Ezzi, Na Xin, Yanmeng Shi, Shuigang Xu, Julien Barrier, Alexey Berdyugin, Shubhadeep Bhattacharjee, Angelika Knothe, Kenji Watanabe, Takashi Taniguchi, Vladimir Falko, Giovanni Vignale, Andre K. Geim, Shaffique Adam, Kostya S. Novoselov, Minsoo Kim Affiliations: Henry Royce Institute for Advanced Materials, University of Manchester, Harvard University, Washington University in St. Louis, National University of Singapore, Sogang University, National Institute for Materials Science Link: http://arxiv.org/abs/2604.13958v1 Summary: This study reveals a dual flatness mechanism in twisted monolayer-bilayer graphene, where a moiré potential-induced global flat band and a bilayer subsystem-generated local flat band coexist within the same conduction band. Through transport measurements and Stoner model analysis, it is found that global flatness opens a global energy gap at integer fillings, yielding discrete correlated insulating states; at non-integer fillings, while local flatness does not open a global gap, it enhances the density of states and triggers spontaneous valley polarization, producing continuous correlated metallic states manifested by the anomalous Hall effect and Berry curvature of opposite signs. Tilted magnetic field experiments further distinguish the orbital characteristics of the two states: the wavefunction of integer states distributes across all layers with magnetic moments aligning with the external field, whereas that of non-integer states localizes in the top layer with magnetic moments locked perpendicular to the plane. This work establishes dual flatness as a design principle for correlated quantum matter, extending moiré physics from the integer-filling-only paradigm to correlated metals at non-integer fillings, and suggests topological transport as an effective probe for gapless correlated states.\n20. Emergent topological phase from a one-dimensional network of defects Relevance Score: 3.1423 Authors: Rahul Singh, Ritajit Kundu, Arijit Kundu, Adhip Agarwala Link: http://arxiv.org/abs/2604.13532v1 Summary: This study demonstrates that by periodically placing two types of defects (impurities) with different strengths on a one-dimensional metallic wire, scattering states can generate emergent topological phases, which are termed Su-Schrieffer-Heeger (SSH) networks. Methodologically, the authors construct a scattering matrix network model that captures the emergent chiral symmetry induced by the defect superlattice and the nontrivial winding number of the quasi-energy bands, thereby elevating the system from a topologically trivial symmetry class to the topologically nontrivial BDI class. Key findings include: by tuning the ratio of defect strengths, the system can be switched between a topological phase (winding number 1) and a trivial phase (winding number 0), accompanied by the closure of the bulk band gap; under open boundary conditions, the topological phase supports zero-energy modes localized at the edges, whose localization length diverges at the phase transition point; further introduction of periodic driving enables robust Thouless charge pumping, with one unit of charge pumped per cycle, a phenomenon characterized by either the winding number of the reflection phase or the Chern number. Moreover, the Bloch mini-band energy spectrum from a microscopic lattice model directly corresponds to the quasi-energy spectrum of the network model, verifying the self-consistency of the theory, and the topological phase remains stable under finite disorder. The conclusion indicates that, in contrast to directly designing atomic Hamiltonians, tunable emergent topological quantum phases can be realized on a metallic platform via defect engineering, and proposes feasible experimental platforms such as quantum dot arrays in integer quantum Hall systems.\n","permalink":"https://nickelates.uk/en/posts/2026-04-15-arxiv-daily/","summary":"\u003cblockquote\u003e\n\u003cp\u003e\u003cstrong\u003eDaily Overview\u003c/strong\u003e:\nToday\u0026rsquo;s highlights focus on an in-depth understanding of the electronic structure of mixed Ruddlesden-Popper nickelates. One study systematically reveals the evolution of the pressure required for the superconducting phase with bandwidth and filling in the bilayer nickelate La₃Ni₂O₇ family by partially substituting La with Nd to alter NiO₆ octahedral tilting, thereby reducing bandwidth, and simultaneously introducing Sr for hole doping to regulate band filling. The study also identifies multiple characteristic resistance anomalies in the non-superconducting state, which may correspond to charge density wave and spin density wave orders competing with superconductivity, indicating that independently controlling bandwidth and filling is crucial for understanding the unconventional superconducting mechanism and its competing orders in this system.\n\u003cstrong\u003earXiv submission processing window\u003c/strong\u003e: 2026-04-15 02:58 to 2026-04-15 19:49 UTC.\u003c/p\u003e","title":"arXiv Daily: nickelate superconductors 2026-04-15"},{"content":" Daily Overview: Today\u0026rsquo;s highlights focus on several physical mechanisms indirectly related to the field of nickel-based superconductivity. Although no papers directly address nickelates, multiple studies explore topics highly relevant to the current core issues in nickel-based superconductivity: [9] investigates the kinetic arrest of the Mott phase transition in V₂O₃, offering new insights into the Mott insulator background and strain modulation in nickelates; [10] systematically calculates the superconducting transition temperature near the two-dimensional van Hove singularity using quantum Monte Carlo methods, revealing the crossover between weak-coupling BCS theory and strong-coupling preformed pairs, which is of reference value for similar Fermi surface topology effects potentially present in nickelates; [2] demonstrates the coupling transitions of structural, mechanical, and electronic properties through thickness-tuning of rippled strain gradients in perovskite oxide thin films, with strain engineering approaches that can inspire stress design in nickelate thin films. Additionally, [1] on magnetic modulation in Ni-doped two-dimensional ferromagnets, [3] on spin transport in altermagnet-superconductor junctions, and [4] on exotic residual phases in chiral superconductors all exhibit potential intersections with the research directions of nickel-based superconductivity at the levels of superconducting pairing, spin-related effects, or topological states. arXiv submission processing window: 2026-04-14 03:53 to 2026-04-14 18:00 UTC.\n1. Tuning Structure and Magnetism in Large-Scale 2D Ferromagnet Fe$_3$GeTe$_2$ through Ni Doping Relevance Score: 3.8972 Authors: Kacho Imtiyaz Ali Khan, Tauqir Shinwari, Soheil Ershadrad, Majid Ahmadi, Weiben Li, Hua Lv, Frans Munnik, Adriana I. Figueroa, Manuel Valvidares, Sandra Ruiz-Gómez, Lucia Aballe, Jens Herfort, Michael Hanke, Bart Kooi, Biplab Sanyal, João Marcelo J. Lopes Link: http://arxiv.org/abs/2604.12571v2 Summary: This study utilized molecular beam epitaxy to grow large-area, high-quality Ni-doped Fe₃GeTe₂ (FGT) two-dimensional ferromagnetic thin films on graphene substrates, achieving precise control over thickness and doping concentration. X-ray diffraction and scanning transmission electron microscopy characterization confirmed that Ni doping induced a contraction of both in-plane and out-of-plane lattice constants, with Ni atoms substituting Fe sites and intercalating into the van der Waals gaps. Measurements using a superconducting quantum interference device, Hall effect, and X-ray magnetic circular dichroism revealed that Ni doping significantly suppressed perpendicular magnetic anisotropy and sharply reduced the Curie temperature from approximately 220 K to 50 K. Density functional theory calculations further elucidated the intrinsic mechanism by which Ni doping alters magnetic exchange interaction parameters and atomic-projected magnetocrystalline anisotropy energy. This work demonstrates the feasibility of tuning the structure and magnetism of two-dimensional ferromagnets on a macroscopic scale through doping engineering, providing essential experimental evidence and physical understanding for the development of spintronic devices based on van der Waals magnetic heterostructures.\n2. Topographic patterning in perovskite oxide membranes for local control of strain, nanomechanics and electronic structure Relevance Score: 3.8525 Authors: Marti Ramis, Markos Paradinas, Jose M. Caicedo, Claudio Cazorla, Roger Guzman, Mariona Coll Affiliations: Institució Catalana de Recerca i Estudis Avançats (ICREA), Catalan Institute of Nanoscience and Nanotechnology (ICN2), Universitat Politècnica de Catalunya, Institut de Ciència de Materials de Barcelona (ICMAB-CSIC) Link: http://arxiv.org/abs/2604.12728v1 Summary: This study employs a water-soluble sacrificial layer method to fabricate (00l)-oriented La₀.₇Sr₀.₃MnO₃ single-crystal perovskite oxide thin films with thicknesses ranging from 4 to 100 nm on flexible silicone/polyethylene terephthalate substrates, which spontaneously form thickness-dependent sinusoidal ripple patterns. Using atomic force microscopy, force-distance spectroscopy, scanning transmission electron microscopy, and electron energy loss spectroscopy, the modulation of local strain, nanomechanics, and electronic structure by the ripples is systematically characterized. The results show that the ripple morphology directly modulates film stiffness, generating over 5% giant local strain and a strain gradient of approximately 2.5×10⁷ m⁻¹ in ultrathin films. These extreme deformations suppress antiferrodistortive octahedral rotations and stabilize polar distortions, indicative of curvature-driven symmetry transition. Variations in surface potential reinforce the ripple-induced polar patterns, which change significantly with thickness. The manganese oxidation state decreases from about 3.2+ to approximately 2.85+, providing a direct chemical signature of thickness-controlled electronic transitions. This study reveals that ripple strain gradients introduced by tuning film thickness can simultaneously drive coupled transitions in structural, nanomechanical, and electronic properties, offering a new pathway for designing functional states in next-generation flexible electronic devices.\n3. Robust realization of spin-polarized specular Andreev reflection in V$_2$O-based altermagnets Relevance Score: 3.7912 Authors: Yutaro Nagae, Andreas P. Schnyder, Satoshi Ikegaya Affiliations: Nagoya University, Hokkaido University, Max-Planck-Institut f¨ur Festk¨orperforschung Link: http://arxiv.org/abs/2604.12695v1 Summary: By constructing a microscopic six-orbital model that explicitly incorporates the sublattice degrees of freedom of vanadium and oxygen sites in the V₂O plane, this paper theoretically investigates charge transport in junctions between a conventional s-wave superconductor and a V₂O-based altermagnet. The altermagnet exhibits unique spin-split quasi-one-dimensional Fermi surfaces. After calculating scattering coefficients under various random interface conditions, the study demonstrates that specular Andreev reflection can robustly emerge with distinct spin polarization signatures. Furthermore, a multi-terminal measurement setup is designed to detect such specular Andreev reflection via nonlocal conductance measurements: by adjusting the bias configuration, regimes where specular Andreev reflection contributes or not can be distinguished, thereby providing a control signal. These results establish V₂O-based altermagnets as a promising platform for realizing spin-resolved Cooper pair splitting—a key process for generating energy-entangled electron pairs.\n4. Charge-4e/6e superconductivity and chiral metal from 3D chiral superconductor Relevance Score: 3.7894 Authors: Chu-Tian Gao, Chen Lu, Yu-Bo Liu, Zhiming Pan, Fan Yang Link: http://arxiv.org/abs/2604.12328v1 Summary: This study systematically investigates thermal fluctuation-induced residual phases in chiral superconducting systems governed by three-dimensional cubic point group symmetry (Oh) through Ginzburg-Landau analysis and Monte Carlo simulations. Focusing on the phase fluctuations of chiral order parameters in the Eg and T2g/T1u irreducible representations, we find that the phase diagram topology differs from that of two-dimensional systems: the multicritical intersection point manifests as a tetracritical point rather than a triple point. The results demonstrate that, within specific parameter regimes, the primary chiral order in both representations can melt into a chiral metallic phase; moreover, for the Eg representation, phase fluctuations can generate a charge-4e superconducting phase under certain conditions, while the T2g/T1u representations lead to a higher-order charge-6e superconducting state. This work reveals the mechanisms underlying exotic states driven by three-dimensional crystal symmetry and provides a theoretical pathway for exploring novel residual phases.\n5. Supercurrent-induced phonon angular momentum Relevance Score: 3.6944 Authors: Takehito Yokoyama Link: http://arxiv.org/abs/2604.12701v1 Summary: This paper proposes a mechanism for supercurrent-induced phonon angular momentum, focusing on mixed-parity superconductors and s-wave superconductors with spin-orbit coupling. Using perturbative calculations, the authors derive an analytic expression for the supercurrent-induced phonon angular momentum and provide a physical interpretation of the effect. It is found that near the superconducting transition temperature, the phonon angular momentum is proportional to the supercurrent density, and the response can be expressed as a function of the supercurrent density via the London equation. For mixed-parity superconductors, the phonon angular momentum is linearly proportional to the supercurrent density; for s-wave superconductors with Weyl-type spin-orbit coupling, the phonon angular momentum appears at third-order perturbation. This effect originates from the combination of supercurrent-induced spin polarization (Edelstein effect) and electron-chiral phonon coupling, which is equivalent to the supercurrent generating an effective magnetic field that drives phonon angular momentum through the orbital Zeeman effect. Experimentally, it can be detected by comparing circularly polarized Raman scattering with and without supercurrent, and it is suggested that this prediction be verified in Nb/Te/Nb Josephson junctions.\n6. Kinetic instability and superconductivity in Li$_2$AuH$_6$ and Li$_2$AgH$_6$ at ambient pressure Relevance Score: 3.6218 Authors: Yucheng Ding, Haoran Chen, Junren Shi Link: http://arxiv.org/abs/2604.12367v2 Summary: This study employed path integral molecular dynamics simulations to investigate the dynamical stability of Li₂AuH₆ and Li₂AgH₆ under ambient pressure, revealing that both compounds are unstable. Li₂AgH₆ undergoes lattice collapse, whereas the fluorite-type Li-Au sublattice in Li₂AuH₆ remains stable, but some hydrogen atoms dimerize into molecules and diffuse within the host lattice. For the system with diffusing atoms, a non-perturbative stochastic path integral method was further used to calculate the superconductivity of Li₂AuH₆ in this state, predicting a superconducting transition temperature of only 22 K, far below the earlier estimates of 80–140 K. This significant reduction arises from the hydrogen sublattice collapse and hydrogen dimerization, which lead to a substantial decrease in the electronic density of states near the Fermi level. The findings indicate that neither Li₂AuH₆ nor Li₂AgH₆ is dynamically stable under ambient pressure, and Li₂AuH₆ is not a high-critical-temperature superconductor.\n7. Momentum-dependent charge-density-wave gap formation in ZrTe_{2.98}Se_{0.02} Relevance Score: 3.5876 Authors: Iori Ishiguro, Hayate Kunitsu, Natsuki Mitsuishi, Shunsuke Tsuda, Koichiro Yaji, Yoichi Yamakawa, Hiroshi Kontani, Takahiro Shimojima Affiliations: Nagoya University, Tohoku University, National Institute for Materials Science Link: http://arxiv.org/abs/2604.12326v1 Summary: Using laser photoelectron emission microscopy, this study precisely resolves the Fermi surface structure of ZrTe₂.₉₈Se₀.₀₂ before and after the charge density wave (CDW) transition: an elliptical α Fermi surface is observed at the center of the Brillouin zone, while two quasi-one-dimensional Fermi surfaces, β and γ, exist along the boundary. By comparing the intensity distributions below and above the CDW transition temperature (~30 K), it is found that the CDW gap formation is confined to a momentum region along the B̅-D̅ line with k_y ranging from approximately 0.25 to 0.8 Å⁻¹, which exactly coincides with the position of the β Fermi surface. The significant momentum dependence of this gap cannot be explained solely by Fermi surface nesting; combined with first-principles calculations and band analysis, it indicates that the orbital composition of the quasi-one-dimensional Fermi surface gradually changes along the k_y direction and matches the strength of electron-phonon coupling. Therefore, the formation of the CDW in the ZrTe₃ system depends simultaneously on Fermi surface nesting and band-dependent electron-phonon coupling, providing key experimental evidence for understanding the competition mechanism between CDW and superconductivity in low-dimensional systems.\n8. Cs$_4$Cr$_7$Te$_{10}$: Interwoven Reconstructed Archimedean and Kagome Lattices with a Possible Phase Transition near 130 K Relevance Score: 3.4523 Authors: Zhen Zhao, Ruwen Wang, Hua Zhang, Tong Liu, Haisen Liu, Guojing Hu, Ke Zhu, Senhao Lv, Gang Cao, Chenyu Bai, Hui Guo, Xiaoli Dong, Wu Zhou, Haitao Yang, Hong-Jun Gao Affiliations: University of Chinese Academy of Sciences, Chinese Academy of Sciences Link: http://arxiv.org/abs/2604.12680v2 Summary: Researchers report a new chromium-based compound Cs₄Cr₇Te₁₀, whose unique crystal structure consists of interwoven chromium and tellurium sublattices derived from a reconstruction of the Archimedean 3.4.6.4 tiling and the kagome lattice, respectively. Transport measurements reveal semiconducting behavior. Magnetization measurements show a weak anomaly at approximately 130 K that is insensitive to magnetic field, along with weak magnetic anisotropy. Heat capacity measurements further confirm this bulk thermodynamic phase transition, but the accompanying entropy change is only 0.41 J mol⁻¹ K⁻¹, ruling out a structural transition and pointing to a possible electronic or magnetic transition. These results not only unveil the unique lattice geometry and physical properties of Cs₄Cr₇Te₁₀ but also offer new insights for designing complex crystal structures and exploring related emergent phenomena.\n9. Kinetic Arrest of a First Order Phase Transition Relevance Score: 3.3315 Authors: Sindhunil Barman Roy Link: http://arxiv.org/abs/2604.12531v1 Summary: This paper proposes a phenomenological theory describing the kinetic arrest of first-order phase transitions, exemplified by the Mott metal-insulator transition in V₂O₃. By defining an order parameter associated with monoclinic distortion and mapping its time-dependent Ginzburg-Landau dynamics onto an Imry-Wortis landscape subject to disorder, the authors derive a universal condition for kinetic arrest. The study finds that in (001)-oriented V₂O₃ thin films, epitaxial substrate-induced elastic clamping significantly elevates the elastic activation barrier, trapping the high-symmetry corundum phase down to 4.2 K. This structural suppression of the insulating state accounts for the hysteretic V-I switching behavior observed experimentally—a hallmark of memristive characteristics. The work identifies this non-equilibrium state as a \u0026ldquo;Mott glass\u0026rdquo; and suggests that strain engineering can modulate this process, providing a predictive framework for the design of neuromorphic synapses.\n10. Superconductivity near two-dimensional Van Hove singularities: a determinant quantum Monte Carlo study Relevance Score: 3.3156 Authors: Gustav Romare, Daniel Shaffer, Alex Levchenko, Edwin Huang, Ilya Esterlis Link: http://arxiv.org/abs/2604.13161v1 Summary: Using determinant quantum Monte Carlo simulations, we systematically compute the superconducting transition temperature Tc of the two-dimensional attractive Hubbard model near ordinary (logarithmic) and higher-order (power-law) van Hove singularities. The results show that for weak interactions (|U| ≤ W/3, where W is the bandwidth), Tc is enhanced near the van Hove point, but the enhancement is much weaker than expected from weak-coupling BCS theory, and upgrading the singularity from logarithmic to power-law yields only a minimal additional increase in Tc. When the interaction strength increases to |U| ≥ W/3, the location of the maximum Tc shifts significantly away from the van Hove point, appearing instead at electron densities unrelated to the non-interacting density of states features, consistent with the physical picture of strong-coupling preformed pairs and Bose-Einstein condensation. Ultimately, the maximum Tc of the model is achieved at intermediate interaction strengths (|U| ~ W/3) in density regions far from the van Hove point.\n11. Directional selection of field-induced phases by weak anisotropy in triangular-lattice K$_2$Mn(SeO$_3$)$_2$ Relevance Score: 3.2688 Authors: Bin Wang, Yantao Cao, Andi Liu, Guoliang Wu, Jin Zhou, Xiaobai Ma, Wenyun Yang, Takashi Ohhara, Akiko Nakao, Koji Munakata, Bing Shen, Zhendong Fu, Zhaoming Tian, Qian Tao, Zhu-an Xu, Wei Li, Jinkui Zhao, Hanjie Guo Link: http://arxiv.org/abs/2604.12489v1 Summary: This study systematically investigates the nearly isotropic triangular lattice manganese compound K₂Mn(SeO₃)₂ through magnetic susceptibility, specific heat measurements, as well as powder and single-crystal neutron diffraction. Under zero field, the compound does not adopt the expected Y-type magnetic structure but instead exhibits an up-down-zero (UD0) structure, in which one-third of the magnetic moments remain disordered even at the lowest temperature (0.05 K). Upon applying an external magnetic field along the c-axis, the UD0 structure becomes highly unstable and transforms into a Y-type structure, followed by the appearance of an up-up-down (UUD) phase corresponding to a 1/3 magnetization plateau; whereas when the magnetic field is applied within the triangular plane, the system enters a canted Y state at a higher critical field. These results indicate that, despite the very weak anisotropy, its direction dependence is significant and plays a decisive role in tuning the field-induced phase selection in this frustrated magnet.\n12. Heavy fermion $\\textit{d-f}$ hybrid and the SmB$_6$ low temperature phase Relevance Score: 3.2630 Authors: Anzhelika V. Buskina, Vladimir A. Zyuzin Link: http://arxiv.org/abs/2604.12959v2 Summary: This paper proposes a heavy fermion d-f hybridization model in which two types of fermions have dispersions with different masses, with one being significantly heavier than the other. At the intersection of the dispersions, hybridization does not open a true insulating gap but instead leaves a heavy fermion d-f hybrid at the Fermi level. The model qualitatively accounts for key experimental phenomena in the low-temperature phase of SmB₆: a linear temperature dependence of the specific heat, saturation of the resistivity at low temperatures, and the frequency-dependent behavior of the optical conductivity. The calculated optical conductivity exhibits a broadened peak at twice the hybridization value, accompanied by a low-frequency tail. The study indicates that SmB₆ is not a true insulator but rather a system with heavy fermion hybrids in the bulk, exhibiting both metallic and insulating characteristics: the metallic contribution leads to linear specific heat, resistivity saturation, and a low-frequency tail in the optical conductivity; the insulating contribution manifests as a rise in resistivity at intermediate temperatures and a peak in the optical conductivity. This work provides a unified theoretical framework for understanding the long-unexplained nature of bulk charge carriers in SmB₆.\n13. Nonmonotonic Scaling of the Anomalous Hall Effect in a Bicollinear Antiferromagnet Relevance Score: 3.2354 Authors: Ruifeng Wang, Chi Fang, Ilya Kostanovski, Ke Xiao, Felix Küster, Jenny Davern, Naoto Nagaosa, Stuart S. P. Parkin Affiliations: Max Planck Institute of Microstructure Physics, RIKEN Link: http://arxiv.org/abs/2604.12636v1 Summary: In epitaxial thin films of the bicollinear antiferromagnet FeTe, the anomalous Hall effect exhibits nonmonotonic scaling behavior. High-quality single-crystalline FeTe thin films were grown on SrTiO₃(001) substrates by molecular beam epitaxy, and a significant anomalous Hall conductivity was observed below the Néel temperature (~60 K). Notably, within a narrow temperature window around 49 K, the anomalous Hall resistance under high magnetic fields becomes nonlinear, deviating from the conventional monotonic scaling relationship between the anomalous Hall effect and longitudinal conductivity. Linear fits reveal a sharp negative peak in the intercept, accompanied by a field-induced canted magnetic moment. This anomalous Hall response originates from the Berry curvature imparted by the topological band structure of FeTe, unveiling a complex coupling mechanism among topology, magnetism, and electronic transport.\n14. Nanoscale electrothermal-switch superconducting diode for electrically programmable superconducting circuits Relevance Score: 3.2319 Authors: Tianyu Li, Jiong Li, Chong Li, Peiyuan Huang, Nuo-Zhou Yang, Wuyue Xu, Wen-Cheng Yue, Yang-Yang Lyu, Yihuang Xiong, Xuecou Tu, Tao Tao, Xiaoqing Jia, Qing-Hu Chen, Huabing Wang, Peiheng Wu, Yong-Lei Wang Affiliations: Zhejiang University, Purple Mountain Laboratories, Nanjing University of Science and Technology, Nanjing University Link: http://arxiv.org/abs/2604.12313v1 Summary: This study demonstrates a nanoscale superconducting diode based on the electrothermal switching effect, where gating-induced local nanohotspots dynamically break the spatial inversion symmetry of superconducting nanowires, enabling nonreciprocal transport. This mechanism yields two coexisting nonreciprocal transport modes within the same device: a nonreciprocal superconducting-to-normal transition and vortex dynamics akin to a ratchet effect, both originating from the same electrothermal switching process. The diode achieves rectification efficiencies of 42% and 60% in the two modes, respectively, and its polarity can be switched on, off, or reversed in situ via a small gate current. Leveraging this capability, electrically reconfigurable programmable superconducting circuits for full-wave and half-wave rectification are realized. The device employs a lithography-compatible design, offering both high performance and gate-tunable functionality, thus providing a scalable platform for programmable superconducting electronics and hybrid quantum systems.\n15. Order-disorder transition and Na-ion redistribution in NASICON-type Na$_3$FeCr(PO$_4$)$_3$ Relevance Score: 3.2215 Authors: Madhav Sharma, Archna Sagdeo, Rajendra S. Dhaka Link: http://arxiv.org/abs/2604.12828v1 Summary: This study employed temperature-dependent synchrotron X-ray diffraction and differential scanning calorimetry to analyze the structural phase transition of the NASICON-type Na₃FeCr(PO₄)₃. The experiments revealed that upon heating, the material undergoes a phase transition from a monoclinic phase (C2/c, with long-range Na vacancy ordering) to a rhombohedral phase (R\\bar{3}c, with statistical Na ion disorder), while the [FeCr(PO₄)₃] polyanionic framework remains essentially unchanged, indicating that the phase transition is driven by the redistribution of the Na sublattice. Along with discontinuous increases in the c-axis and unit cell volume, the occupancy of Na(1) sites gradually decreases, and Na ions transfer to the Na(2) sublattice. The temperature dependence of the superstructure diffraction intensity deviates from mean-field critical behavior and conforms to an S-shaped phase fraction model. Thermal analysis shows that the enthalpy change of the first transition near 350 K (4.17 kJ mol⁻¹) is significantly larger than that of the second transition near 445 K (-1.56 kJ mol⁻¹), suggesting that the major configurational rearrangement occurs in the low-temperature range. Combining the diffraction and calorimetric results, it is revealed that Na ordering proceeds through an order-disorder transition involving intermediate Na configurations and a limited coexistence region. The quantitative correlation among Na vacancy ordering, lattice strain, and symmetry reduction confirms that configurational interactions within the Na conduction channels play a central role in the phase stability of NASICON-type materials.\n16. Symmetry breaking structural relaxation and optical transitions of native defects and carbon impurities in LiGa$_5$O$_8$ Relevance Score: 3.1731 Authors: Klichchupong Dabsamut, Adisak Boonchun, Walter R. L. Lambrecht Affiliations: Kasetsart University, Chulabhorn Royal Academy, Case Western Reserve University Link: http://arxiv.org/abs/2604.12609v1 Summary: This study employs the HSE hybrid functional method to systematically investigate the optical transition properties of intrinsic defects and carbon impurities in LiGa₅O₈. Unlike previous work focusing on thermodynamic transition levels, this paper emphasizes constructing defect configuration diagrams to describe vertical transitions (i.e., absorption and emission processes) between different charge states. By allowing more complex symmetry-breaking relaxations, the structural relaxations of various intrinsic defects are re-examined. It is found that Li vacancies form polaron states after symmetry breaking, with holes localized on a single oxygen atom, and the 0/−1 transition level deepens from 0.74 eV to 1.58 eV, correcting contradictory results in previous literature. The symmetry-broken polaron state is 0.84 eV lower in energy than the symmetric non-polaron state, and the former introduces an isolated defect level within the band gap. For Ga vacancies, allowing lower-symmetry relaxations yields multiple transition levels consistent with prior studies. Additionally, carbon impurities, which may originate from organic precursors, are examined and found not to be shallow acceptors. Although Li vacancies are the naturally shallowest acceptors, none of the above defects can explain the experimentally observed unintentional p-type conductivity, suggesting that p-type conduction may arise from local non-equilibrium states in the sample. This work provides optical fingerprint references for experimentally identifying defects through photoluminescence or cathodoluminescence.\n17. Orbital-selective correlations and angular momentum coupling in heavy actinides Am, Cm, Bk, and Cf under pressure: A many-body perspective Relevance Score: 3.1731 Authors: Haiyan Lu Link: http://arxiv.org/abs/2604.12249v1 Summary: This work systematically investigates the electronic structures of americium (Am), curium (Cm), berkelium (Bk), and californium (Cf) in the ambient-pressure double hexagonal close-packed (dhcp) phase and the high-pressure face-centered cubic (fcc) phase using density functional theory combined with the embedded dynamical mean-field theory. The results show that Am exhibits moderate correlation strength and predominantly jj-coupled localized 5f states; in Cm and Bk, strong electronic correlations drive the system into the localized region, forming Hubbard bands, large effective masses, and non-Fermi liquid behavior, with their magnetic ground states dominated by intermediate coupling exchange interactions biased toward LS coupling; Cf re-enters the jj-coupling regime and displays the strongest orbital-selective correlations in this series. The atomic eigenstate probabilities indicate moderate configuration mixing in Am, while Cm, Bk, and Cf maintain nearly fixed trivalent configurations, signifying the localization of 5f states. Compared with the dhcp phase, the fcc structure generally enhances correlation effects, manifested as a wider Hubbard gap in Am and increased valence fluctuations. Analyses of kinetic energy, potential energy, spin susceptibility, and charge susceptibility further confirm the progressive localization of 5f electrons from Am to Cf and the emergence of orbital-selective correlations. This work establishes a unified picture of 5f electron evolution across the Am–Cf series, elucidates the interplay among spin-orbit coupling, electronic correlations, and crystal structure in heavy actinides, and provides an understanding of high-pressure behavior.\n18. Josephson coupling through a magnetic racetrack Relevance Score: 3.1567 Authors: A. A. Mazanik, F. S. Bergeret Link: http://arxiv.org/abs/2604.12742v1 Summary: This study numerically solves the Usadel equation to analyze the influence of Bloch domain walls in a diffusive magnetic racetrack on Josephson junctions connecting two superconducting electrodes. The interaction between supercurrent and the domain wall leads to highly nontrivial spatial distributions: when the domain wall is located at the junction center, the supercurrent accumulates along the wall, while near the boundaries it is expelled, accompanied by the formation of current loops. The critical current Ic is significantly modulated by the domain wall position along the racetrack, and under small exchange fields, a domain-wall-displacement-driven 0-π transition can be achieved, the mechanism of which arises from singlet-triplet conversion induced by the domain wall. These results provide a clear principle for the design of superconducting racetrack memory readout, confirming that domain walls can serve as effective control elements.\n19. Angle dependent hysteretic magnetotransport in MnBi2Te4 nanoflakes Relevance Score: 3.1419 Authors: Tithiparna Das, Soumik Mukhopadhyay Link: http://arxiv.org/abs/2604.12702v1 Summary: By employing angle-dependent magnetoresistance measurements, this paper systematically investigates the hysteretic magnetotransport behavior in layered antiferromagnetic MnBi2Te4 nanolayers. Experiments were conducted on single-crystal nanolayers of varying thicknesses (from several to tens of nanometers), measuring the hysteresis of longitudinal and Hall resistances during magnetic field sweeps. The results reveal a pronounced non-monotonic thickness dependence of the hysteresis area, which peaks at a thickness of approximately 17–18 nm, with hysteresis diminishing in both thinner and thicker samples; angle-dependent measurements indicate that hysteresis is strongest when the magnetic field deviates from the easy axis by about 20°, and multiple critical fields exhibit distinct angular evolution trends. These features rule out both surface-dominated magnetism and simple bulk sublattice magnetic transitions as origins. Combined with the deviation of magnetoresistance from coherent rotation behavior in the intermediate field range and the differences between forward and backward angle sweeps, the authors propose that magnetic irreversibility primarily arises from domain wall pinning and depinning processes in spatially inhomogeneous magnetic configurations. The conclusion states that dimensionality reduction is a key factor driving magnetic irreversibility in MnBi2Te4.\n20. Sensitive dependence of Poor Man\u0026rsquo;s Majorana modes on the length of the superconductor Relevance Score: 3.1294 Authors: Zhi-Lei Zhang, Xin Yue, Guo-Jian Qiao, C. P. Sun Link: http://arxiv.org/abs/2604.12950v2 Summary: This study models a superconductor as a finite-length one-dimensional chain treated on an equal footing with two quantum dots, systematically deriving the existence conditions for Poor Man\u0026rsquo;s Majorana modes under arbitrary superconducting lengths, tunneling strengths, and magnetic fields. The core finding is that the number of PMMs is extremely sensitive to the superconducting length: it oscillates between zero and two as the length varies, with an oscillation period equal to the Fermi wavelength (about 1 Å); when the superconducting length is much larger than the coherence length, the effective coupling vanishes and the system supports four PMMs. It is further demonstrated that, under finite superconducting length, strictly localized PMMs at the two ends of the system do not exist, and only sufficiently strong magnetic fields enable approximately localized PMMs. Based on this, a generalized \u0026ldquo;sweet spot\u0026rdquo; realizable in practical systems is provided. These results resolve the discrepancy between ideal models and previous theories regarding the number of PMMs and indicate that the superconducting length directly determines whether Majorana-related signals can be observed.\n","permalink":"https://nickelates.uk/en/posts/2026-04-14-arxiv-daily/","summary":"\u003cblockquote\u003e\n\u003cp\u003e\u003cstrong\u003eDaily Overview\u003c/strong\u003e:\nToday\u0026rsquo;s highlights focus on several physical mechanisms indirectly related to the field of nickel-based superconductivity. Although no papers directly address nickelates, multiple studies explore topics highly relevant to the current core issues in nickel-based superconductivity: [9] investigates the kinetic arrest of the Mott phase transition in V₂O₃, offering new insights into the Mott insulator background and strain modulation in nickelates; [10] systematically calculates the superconducting transition temperature near the two-dimensional van Hove singularity using quantum Monte Carlo methods, revealing the crossover between weak-coupling BCS theory and strong-coupling preformed pairs, which is of reference value for similar Fermi surface topology effects potentially present in nickelates; [2] demonstrates the coupling transitions of structural, mechanical, and electronic properties through thickness-tuning of rippled strain gradients in perovskite oxide thin films, with strain engineering approaches that can inspire stress design in nickelate thin films. Additionally, [1] on magnetic modulation in Ni-doped two-dimensional ferromagnets, [3] on spin transport in altermagnet-superconductor junctions, and [4] on exotic residual phases in chiral superconductors all exhibit potential intersections with the research directions of nickel-based superconductivity at the levels of superconducting pairing, spin-related effects, or topological states.\n\u003cstrong\u003earXiv submission processing window\u003c/strong\u003e: 2026-04-14 03:53 to 2026-04-14 18:00 UTC.\u003c/p\u003e","title":"arXiv Daily: nickelate superconductors 2026-04-14"},{"content":" Daily Overview: Today’s highlights focus on an in-depth understanding of the electronic structure of hybrid Ruddlesden–Popper nickelates. One study [1] systematically analyzed the Raman response of superconducting multi-orbital systems using electronic Raman scattering, with nickelates as an application target. It revealed unique fingerprint features in Raman spectra for different pairing symmetries (d-wave, s±-wave, s-wave) and model structures (single-layer/bilayer, single-orbital/two-orbital), and pointed out that full multi-orbital calculations are crucial for capturing inter-orbital hybridization effects, providing key theoretical tools for clarifying the minimal model and gap symmetry of nickelate superconductivity. Additionally, [10] investigated the microscopic mechanism of photo-resonance enhanced pair correlations in K₃C₆₀, identifying symmetry-constrained two-photon paths to provide independent support for a purely electronic mechanism underlying photo-induced superconducting pair formation. This mechanism may have generality in moderately coupled Hubbard systems and offers insights for exploring photo-controlled pairing in nickelate superconductors. [13] focused on anomalous conductive behavior at step edges of topological metal surfaces, revealing non-integer quantized conductance determined by the bulk Weyl node spacing and step orientation. This bulk–edge correspondence provides a new perspective for understanding the relationship between disorder and transport in topological materials, and offers useful references for the interplay between edge states and bulk superconductivity in unconventional superconductors. arXiv submission processing window: 2026-04-13 04:45 to 2026-04-13 19:38 UTC.\n1. Raman response in superconducting multiorbital systems with application to nickelates Relevance Score: 4.7509 Authors: Matías Bejas, Jun Zhan, Xianxin Wu, Andreas P. Schnyder, Andrés Greco Affiliations: University of Chinese Academy of Sciences, Chinese Academy of Sciences, Universidad Nacional de Rosario, Max Planck Institute for Solid State Research Link: http://arxiv.org/abs/2604.11997v1 Summary: This study systematically analyzes the Raman response of superconducting multi-orbital systems using electronic Raman scattering methods, with nickelates as the application target. For three models—a single-layer and a bilayer two-orbital model involving d_{x^2-y^2} and d_{z^2} orbitals, and a bilayer single-orbital model with only d_{x^2-y^2} orbitals—multiple pairing symmetries including d-wave, s±-wave, and s-wave are considered, and the response characteristics under various Raman symmetries (A1g, B1g, B2g) are calculated. In the two-orbital models, a full multi-orbital approach is employed, incorporating both intra-orbital and inter-orbital scattering, and compared with the additive approximation that simply sums the Raman responses of individual bands. The results reveal distinct fingerprint features in the Raman spectra for different pairing symmetries and model structures, with the full multi-orbital calculations uncovering inter-orbital mixing effects that the additive approximation may overlook. These findings help clarify the minimal model for nickelate superconductivity, determine the magnitude and symmetry of their superconducting gaps, and provide a general theoretical framework for Raman experimental analysis of other multi-orbital superconductors, such as iron-based superconductors.\n2. Strongly correlated model of acousticlike plasmons persisting across the phase diagram of cuprate superconductors Relevance Score: 4.1374 Authors: Luciano Zinni, Hiroyuki Yamase, Matthias Hepting, Matías Bejas, Andrés Greco Link: http://arxiv.org/abs/2604.11702v1 Summary: Using the layered t-J-V model that incorporates both strong correlation and long-range Coulomb interaction, it is found that a single set of microscopic parameters can consistently describe the acoustic plasmon dispersions observed in all existing resonant inelastic X-ray scattering (RIXS) data for the cuprate superconductor La₂₋ₓSrₓCuO₄, spanning from the underdoped to the heavily overdoped regime. The cross-doping transferability of this parameter set surpasses that of earlier theories, indicating that strong correlation persists even in the heavily overdoped region, while the acoustic plasmon, as a collective mode, exhibits only limited sensitivity in distinguishing electronic phenomena specific to different regions of the phase diagram, such as the pseudogap, charge and spin ordering, superconductivity, and strange metal behavior. The conclusion suggests that low-energy acoustic plasmons are robust collective charge excitations in strongly correlated electronic systems, with their dispersion primarily governed by the layered structure and Coulomb interactions rather than by specific electronic orders.\n3. Type-II superconductivity in the Dirac semimetal PdTe2 Relevance Score: 4.1311 Authors: Ritu Gupta, Catherine Witteveen, Debarchan Das, Fabian O. von Rohr, Rustem Khasanov Link: http://arxiv.org/abs/2604.11047v1 Summary: This study systematically investigates the microscopic superconducting properties of mosaic crystals of the Dirac semimetal PdTe₂ using zero-field and transverse-field muon spin relaxation/rotation (μSR), AC susceptibility, and resistivity measurements. Susceptibility measurements reveal two superconducting transition temperatures (1.8 K and 1.6 K), consistent with previous reports, but contrary to earlier conclusions classifying it as a type-I superconductor, we find these crystals are actually type-II superconductors. In the superconducting state, the clear diamagnetic shift and Gaussian broadening observed in Fourier spectra provide unambiguous evidence for the presence of a flux line lattice, a behavior likely induced by disorder in the mosaic crystals. Analysis of the superconducting order parameter based on the temperature-dependent magnetic penetration depth λ(T) reveals a fully gapped superconducting state, well described by an s-wave symmetric gap. These results indicate that PdTe₂ serves as an ideal model system for studying the interplay among nontrivial topology, surface superconductivity, and type-II bulk superconductivity in van der Waals materials, and its superconducting type can be readily tuned from type-I to type-II via disorder.\n4. Reduced pair breaking from extended disorder in unconventional superconductors: implications to 4Hb-TaS$_2$ Relevance Score: 3.7718 Authors: Yuval Tsur, Mark H. Fischer, Jonathan Ruhman Link: http://arxiv.org/abs/2604.11738v1 Summary: This study employs a multiband model combined with Ising spin-orbit coupling to simulate extended impurity potentials arising from chalcogen vacancies or adatoms in H-phase transition metal dichalcogenides, and compares them with conventional point-defect potentials. By calculating momentum relaxation rates and pair-breaking rates on an equal footing, it is found that extended impurity potentials can parametrically reduce the pair-breaking rate to approximately one-third of the momentum scattering rate (Γτ_D ~ 1/3). This effect originates from a partial match between the momentum structure of the impurity potential and the internal structure of the superconducting gap, thereby suppressing the pair-breaking process. Consequently, the robustness of the unconventional superconducting state against disorder is significantly enhanced beyond the predictions of the standard Abrikosov–Gor\u0026rsquo;kov (AG) theory. These results provide a natural explanation for the coexistence of high resistivity and unconventional superconductivity in materials such as 4Hb-TaS₂, bridging the apparent contradiction between transport measurements and superconducting pairing theory.\n5. Density Functional Theory Study of Lanthanide Monoxides under High Pressure: Pressure-Induced B1-B2 Transition Relevance Score: 3.7179 Authors: Sergio Ferrari, Daniel Errandonea Affiliations: CNEA, Consejo Nacional de Ciencia y Tecnología, Universidad de Valencia Link: http://arxiv.org/abs/2604.11194v1 Summary: Using density functional theory, the crystal structure stability of 15 lanthanide monoxides (La to Lu) under hydrostatic pressure was systematically investigated. The generalized gradient approximation (GGA) and local density approximation (LDA) were employed for calculations of the ambient-pressure B1 (NaCl-type) structure, and comparison with available experimental data revealed that the GGA method provides more accurate descriptions of lattice parameters. Based on these findings, high-pressure studies were conducted using the GGA method for three cubic structures: B1, B2 (CsCl-type), and B3 (ZnS-type). The results indicate that at ambient pressure, the B1 structure exhibits the lowest enthalpy for all compounds, representing the thermodynamically most stable phase; with increasing pressure, all compounds undergo a structural phase transition from B1 to B2. The transition pressures for each compound were determined (mostly 71–135 GPa, with the lowest at 29 GPa for YbO and the highest at 209 GPa for LuO), along with the pressure–volume relationships. Isothermal equations of state were fitted, yielding zero-pressure bulk moduli ranging from 125 to 152 GPa. This study predicts the universal B1–B2 phase transition in lanthanide monoxides under high pressure, providing theoretical guidance for future experiments.\n6. Quasi-linear `non-metallic\u0026rsquo; resistivity in the distorted-kagome metal CrPdAs Relevance Score: 3.5408 Authors: Benny Lau, Wenlong Wu, Bo Yuan, Julian Nickel, Stephen Julian Link: http://arxiv.org/abs/2604.11630v1 Summary: This study successfully grew single crystals of the distorted kagome lattice compound CrPdAs and characterized their structure and physical properties. All crystals exhibited spin-glass behavior with a freezing temperature of approximately 60 K; annealing treatment yielded single-phase crystals free of ferromagnetic impurity phases, although Cr and Pd sites still displayed about 29% antisite disorder. Low-temperature heat capacity measurements revealed a relatively large linear coefficient γ = 23 ± 3 mJ/mol·K², a typical characteristic of kagome metals. Band structure calculations indicated multiple Dirac-type band crossings near the Fermi level, which were lifted by spin-orbit coupling. Most critically, the in-plane resistivity exhibited non-metallic behavior over the entire measured temperature range from 300 K to 2 K: the resistivity monotonically increased with decreasing temperature and showed a quasi-linear dependence below about 130 K, without any sign of saturation down to 2 K. This quasi-linear non-metallic resistivity showed no clear correlation with the spin-glass transition, providing new insights into the anomalous transport in kagome metals.\n7. Topological Kondo Insulator from Spin Loop Currents Relevance Score: 3.4264 Authors: Andreas Gleis, Kevin Lucht, Po-Jui Chen, Daniele Guerci, Andrew J Millis, J. H. Pixley Link: http://arxiv.org/abs/2604.11739v1 Summary: Research indicates that the AB-stacked MoTe₂/WSe₂ bilayer system can realize a topological Kondo insulator at hole filling ν=2. When considering only local correlations, symmetry in the moiré band structure forces band inversion and band overlap to couple, forming a compensated topological semimetal. The study finds that nonlocal interactions fundamentally alter the physical properties: quantum geometry-induced spin loop currents act back on the effective band structure, eliminating residual accidental degeneracies and opening a full spectral gap, thereby producing a fully gapped topological Kondo insulator. This conclusion is based on a combination of real-time dynamical mean-field theory (addressing Kondo physics) and the Hartree-Fock approximation (addressing nonlocal interactions). The topological Kondo insulator emerges in the intermediate displacement field regime, where strong correlations manifest as enhanced spin susceptibility, suppressed charge susceptibility, and a stronger temperature dependence of resistivity. The computational results are in excellent agreement with recent experiments on displacement-field-tuned topological-trivial phase transitions in MoTe₂/WSe₂ bilayers.\n8. Evolution of effective magnetic exchange interaction under spin dilution in SrIr$_{1-x}$Sn$_x$O$_3$ Relevance Score: 3.3238 Authors: Xiang Li, Yifan Jiang, Yuan Wan, Xuerong Liu Link: http://arxiv.org/abs/2604.11075v1 Summary: Resonant inelastic X-ray scattering measurements combined with the linear spin-wave theory model were employed to systematically investigate the magnetic excitation behavior in the SrIr₁₋ₓSnₓO₃ series with spin dilution ratios of x = 0, 0.03, 0.06, 0.1, and 0.2. It was found that as the fraction of nonmagnetic Sn substituting for Ir increases, the effective magnetic exchange interaction continuously decreases, with its evolution following a simple spin dilution scaling law, where the effective exchange interaction is proportional to (1-x). This result not only confirms that the metallic parent compound SrIrO₃ possesses strong electronic correlation characteristics but also reveals the entanglement between charge and spin dynamics in this system. At a doping level of x = 0.2, the effective exchange interaction deviates from the linear scaling, likely due to clustering effects of Sn dopants.\n9. Ladder-like Structural Architecture of Layered Magnetic $A_{2.4}$Cr$_8$Te$_{14}$ ($A$ = Rb, Cs) Compounds by Self-flux Synthesis Relevance Score: 3.2958 Authors: Kai D. Röseler, Felix Eder, Fabian O. von Rohr Affiliations: University of Geneva Link: http://arxiv.org/abs/2604.11153v1 Summary: By fine-tuning the alkali metal-tellurium flux composition via a self-flux method, novel layered magnetic compounds A₂.₄Cr₈Te₁₄ (A = Rb, Cs) were successfully synthesized. Their crystal structures feature a unique ladder-like hybrid framework that integrates the two-dimensional layered characteristics of the delafossite-type phase ACrTe₂ with the tunnel structural units of the hollandite-type phase AₓCr₅Te₈. Direction-dependent magnetization measurements on oriented single crystals reveal distinct magnetic ground states: Rb₂.₄Cr₈Te₁₄ exhibits antiferromagnetic ordering at T_N = 114.5 K, while Cs₂.₄Cr₈Te₁₄ displays ferrimagnetic ordering at T_C = 125.0 K. This work highlights the simplicity and effectiveness of the flux growth strategy in discovering low-dimensional magnetic materials, offering an avenue for designing novel structures with tunable dimensionality and magnetic order.\n10. Microscopic mechanism for resonant light-enhanced pair correlations in K$_3$C$_{60}$ Relevance Score: 3.2005 Authors: Juan I. Aranzadi, Joseph Tindall, Paul Fadler, Michael A. Sentef Link: http://arxiv.org/abs/2604.10987v1 Summary: Based on a K₃C₆₀ driven electron model constructed from first-principles parameters, exact diagonalization identifies symmetry-constrained two-photon pathways: the first photon excites the system from an even-parity ground state to an odd-parity intermediate state, and the second photon further drives it to an even-parity excited state with enhanced pair correlations. Using the DMRG+Krylov method to study larger clusters, it is found that the resonance energy shifts downward with system size due to the kinetic energy gained by delocalized double-occupancy excitations. A simplified single-orbital model reproduces the same scaling trend and pushes the resonance peak to approximately 30 THz in a 14-site face-centered cubic cluster. These results indicate that the experimentally observed 10 THz resonance originates from resonantly enhanced pair correlations driven by purely electronic mechanisms rather than simple metallic improvement, independently supporting the interpretation of superconductor-like coherent pair formation. This mechanism suggests that similar resonant pathways may exist in intermediate-coupling Hubbard materials, where local repulsion U and electronic bandwidth W are comparable.\n11. Berry curvature and field-induced intrinsic anomalous Hall effect in an antiferromagnet FeTe Relevance Score: 3.1413 Authors: Satoshi Okamoto, Adriana Moreo, Naoto Nagaosa, Stuart S. P. Parkin Link: http://arxiv.org/abs/2604.11583v4 Summary: Based on the spin-fermion model combined with density functional theory and the Wannier tight-binding method, this paper theoretically investigates the intrinsic anomalous Hall effect in the tetragonal van der Waals antiferromagnet FeTe. The study reveals that under an external magnetic field, FeTe exhibits a significant anomalous Hall conductivity driven by Berry curvature; this conductivity is highly sensitive to both temperature and magnetic field strength, and can undergo a sign reversal near the antiferromagnetic transition. Calculations show that the Berry curvature distribution evolves with magnetic ordering, causing the Hall response to change from positive conductivity at high temperatures to negative conductivity at low temperatures, with the sign reversal temperature shifting markedly as the Fermi level changes. This work establishes FeTe as a prototype platform where magnetism and topology cooperate to produce a strong intrinsic Hall response, offering a new route to explore quantum transport in low-dimensional correlated systems and explaining the anomalous and non-normal Hall effects observed in recent experiments.\n12. Ru Alloying in Ni/Al Reactive Multilayers: Experimental Observations and Molecular Dynamics Simulations Relevance Score: 3.0765 Authors: Nensi Toncich, Ankit Yadav, Jan Fikar, Ralph Spolenak Link: http://arxiv.org/abs/2604.11370v1 Summary: This study employs a combined experimental and molecular dynamics simulation approach to investigate the effects of incorporating ruthenium (Ru) as a co-alloying element into Ni/Al reactive multilayers. Experimentally, Al/Ni-Ru multilayers with varying Ru content were fabricated via magnetron co-sputtering, revealing that Ru addition significantly enhances the propagation velocity of the reaction front while simultaneously inducing a composition-dependent phase transition from face-centered cubic (fcc) to hexagonal close-packed (hcp) in the as-deposited Ni-Ru layers. Molecular dynamics simulations using modified embedded atom method (EAM) potentials, with a small amount of Ru (1 at.%) substituting Ni in the model, reproduce the trend of increased reaction rate and elucidate atomic-scale mechanisms: Ru incorporation alters diffusion behavior and reaction pathways. Simulations further indicate that exceeding a certain Ru content threshold leads to solid solution destabilization. Both experimental and simulation results consistently confirm that Ru alloying effectively modulates the heat release rate and peak temperature of the reactive multilayers while influencing the microstructure of the final products. This work provides new insights into designing advanced reactive multilayers with tailored thermal and mechanical properties through alloying strategies.\n13. Step-Edge Anomaly in Topological Metals Relevance Score: 3.0475 Authors: Oskar Schweizer, Virginia Gali, Adam Y. Chaou, Gal Lemut, Piet W. Brouwer, Maxim Breitkreiz Link: http://arxiv.org/abs/2604.11654v1 Summary: This study investigates the anomalous electrical conduction behavior at step edges on the surface of three-dimensional topological metals, demonstrating that the conductance is uniquely determined by the bulk Weyl node separation and step orientation, exhibiting a non-integer value (K e^2/h). Based on the topological theory of gapless systems, numerical simulations and analytical calculations using a tight-binding lattice model reveal that the step-edge conductance is independent of local details or step height, arising from the cooperative contributions of localized chiral modes and nonlocal bulk modes, and remains unaffected by surface barriers or finite-size effects. Numerical results confirm the robustness of the conductance and show enhanced density of states at the step edge with asymmetric energy dependence, consistent with experimental observations. This work establishes a bulk-step-edge correspondence, providing a universal explanation for anomalous transport phenomena in topological metals and suggesting that step-edge currents may play a critical role in the low-resistivity mechanism of nanowires.\n14. High-Pressure Structural Evolution of Na2ZrSi2O7 and Na2ZrSi2O7.H2O: Topology-Driven Compression Behaviors, Phase Stability, and Electronic Transitions Relevance Score: 3.0333 Authors: Peijie Zhang, Pablo Botella, Neha Bura, Xiao Dong, Catalin Popescu, Yellampalli Raghavendra, Rakesh Shukla, Srungarpu Nagabhusan Achary, Daniel Errandonea Affiliations: Universitat de Valencia, Nankai University, Center for High Pressure Science and Technology Advanced Research (HPSTAR), Bhabha Atomic Research Center (BARC), CELLS-ALBA Synchrotron Light Facility Link: http://arxiv.org/abs/2604.11186v1 Summary: Through high-pressure synchrotron X-ray diffraction and electronic structure calculations, the structural evolution of anhydrous Na₂ZrSi₂O₇ and its hydrate Na₂ZrSi₂O₇·H₂O was comparatively studied up to 30 GPa. Although both share the same primary building units ([ZrO₆] octahedra and [SiO₄] tetrahedra), they differ in secondary building units (M₂T₄ vs. M₂T₆). The anhydrous compound undergoes a phase transition at approximately 15 GPa, while the hydrate remains stable up to 30 GPa. The anhydrous counterpart exhibits a higher bulk modulus (77.1 GPa) and less compression anisotropy, with compression primarily accommodated through distortion of [ZrO₆] octahedra; in contrast, the hydrate compresses via tilting of [Si₂O₇] groups, resulting in a lower bulk modulus (66.3 GPa). Electronic structure calculations reveal that the band gaps of both materials widen with increasing pressure, but the anhydrous compound undergoes a transition from a direct to an indirect band gap, whereas the hydrate retains a direct band gap throughout. These findings elucidate how topological changes in secondary building units induced by hydration dominate the pressure response, phase stability, and electronic properties of the zirconosilicate framework.\n","permalink":"https://nickelates.uk/en/posts/2026-04-13-arxiv-daily/","summary":"\u003cblockquote\u003e\n\u003cp\u003e\u003cstrong\u003eDaily Overview\u003c/strong\u003e:\nToday’s highlights focus on an in-depth understanding of the electronic structure of hybrid Ruddlesden–Popper nickelates. One study [1] systematically analyzed the Raman response of superconducting multi-orbital systems using electronic Raman scattering, with nickelates as an application target. It revealed unique fingerprint features in Raman spectra for different pairing symmetries (d-wave, s±-wave, s-wave) and model structures (single-layer/bilayer, single-orbital/two-orbital), and pointed out that full multi-orbital calculations are crucial for capturing inter-orbital hybridization effects, providing key theoretical tools for clarifying the minimal model and gap symmetry of nickelate superconductivity. Additionally, [10] investigated the microscopic mechanism of photo-resonance enhanced pair correlations in K₃C₆₀, identifying symmetry-constrained two-photon paths to provide independent support for a purely electronic mechanism underlying photo-induced superconducting pair formation. This mechanism may have generality in moderately coupled Hubbard systems and offers insights for exploring photo-controlled pairing in nickelate superconductors. [13] focused on anomalous conductive behavior at step edges of topological metal surfaces, revealing non-integer quantized conductance determined by the bulk Weyl node spacing and step orientation. This bulk–edge correspondence provides a new perspective for understanding the relationship between disorder and transport in topological materials, and offers useful references for the interplay between edge states and bulk superconductivity in unconventional superconductors.\n\u003cstrong\u003earXiv submission processing window\u003c/strong\u003e: 2026-04-13 04:45 to 2026-04-13 19:38 UTC.\u003c/p\u003e","title":"arXiv Daily: nickelate superconductors 2026-04-13"},{"content":" Daily Overview: Today\u0026rsquo;s highlighted work focuses on the study of physical mechanisms closely related to the field of nickel-based superconductivity. Although no papers directly addressing nickelates were present, several studies provided important insights into core topics such as quantum criticality, d-wave pairing, and magnetic order. [1] Using optical low-temperature experiments, the electrodynamics of disordered NbN, granular Al, and the heavy-fermion compound CeCoIn5 were systematically investigated, revealing Higgs modes, Goldstone modes, and hidden Fermi liquid behavior in quantum critical superconductors. These phenomena are directly related to possible quantum critical points and unconventional pairing mechanisms in nickel-based superconductivity. [2] Spin-resolved photoemission spectroscopy clarified the magnetic controversy in RuO₂, indicating surface ferrimagnetism rather than altermagnetism, providing a comparative case for understanding the influence of oxygen coordination environments on magnetism in nickel-based superconductors. [3] A universal design principle for vacancy-driven two-dimensional d-wave altermagnets was proposed, characterizing the symmetry of d-wave spin splitting, which is consistent with the symmetry of d-wave pairing in nickel-based superconductors. This design approach may inspire the exploration of similar electronic structure reconstructions in nickel-based superconducting systems. [4] The competition between disorder and interactions in quantum Hall systems was systematically studied, revealing the transition from fractional quantum Hall liquids to Wigner crystals. The concept of the many-body phase diagram can provide an analogy for the competition between charge order and superconductivity in nickel-based superconductors. These works deepen the understanding of quantum phenomena related to nickel-based superconductivity from various perspectives. arXiv submission processing window: 2026-04-12 12:58 to 2026-04-12 18:34 UTC.\n1. Electrodynamics of Quantum-Critical Conductors and Superconductors Relevance Score: 4.1859 Authors: Uwe S. Pracht Link: http://arxiv.org/abs/2604.10621v1 Summary: This paper investigates the electrodynamic properties of three materials—disordered NbN, granular aluminum films, and the heavy-fermion compound CeCoIn5—through optical low-temperature experiments, aiming to establish a unified picture of quantum critical superconductivity. Using coherent terahertz radiation transmission measurements, the dynamic conductivity as a function of photon energy is obtained, tracing the evolution of electronic states and collective excitations. In disordered NbN, near the superconductor-insulator quantum critical point, the spectral gap is suppressed and sub-gap absorption emerges, attributed to the Higgs mode predicted in relativistic boson field theories. For granular aluminum, the origin of the superconducting dome is revealed: as grains decouple, the pairing amplitude first enhances and then saturates, while the superfluid stiffness drops sharply, causing the critical temperature to first rise and then fall; additionally, pseudogap and sub-gap absorption are observed, with the latter explained as the optically active Goldstone mode in a disorder model. In CeCoIn5, analysis of effective mass enhancement and relaxation rate via the generalized Drude model reveals hidden Fermi liquid characteristics: despite anomalous resistivity, the quasiparticle relaxation rate still follows Fermi liquid behavior, and the system exhibits scaling consistent with quantum criticality. These studies deepen the understanding of quantum critical superconductors and offer new perspectives for enhancing superconductivity through nanoengineering and investigating exotic phenomena in unconventional superconductors.\n2. Surface ferrimagnetic order in RuO2 film Relevance Score: 3.2117 Authors: Jiahua Lu, Huangzhaoxiang Chen, Zhe Zhang, Xinyue Wang, Donghang Xie, Bo Liu, Liang He, Yao Li, Jun Du, Zhi Wang, Junwei Luo, Rong Zhang, Yongbing Xu, Xuezhong Ruan Affiliations: Chinese Academy of Sciences, University of York, Nanjing University Link: http://arxiv.org/abs/2604.10659v1 Summary: RuO₂ has long been proposed as a prototypical altermagnet, but its magnetic properties have been the subject of intense debate. In this study, using spin- and angle-resolved photoemission spectroscopy, we directly detect that RuO₂ films are nonmagnetic in the bulk but spontaneously form a surface ferrimagnetic order. The observed narrow surface states exhibit identical spin polarization directions at opposite momenta and at the Brillouin zone center, which is completely inconsistent with the spin texture of any altermagnetic order. First-principles calculations confirm the nonmagnetic ground state in the bulk and reveal that the observed magnetism is confined exclusively to the fully oxygen-terminated surface: at this surface, charge transfer from Ru to O triggers an antiparallel alignment of magnetic moments (+0.48 μB and –0.04 μB) between adjacent Ru sublattices, resulting in ferrimagnetic ordering. Our results provide a unified framework that reconciles previous conflicting reports on the magnetism of RuO₂, unambiguously attributing the observed magnetic signals to surface ferrimagnetism rather than altermagnetism, thereby resolving this long-standing controversy.\n3. Vacancy-driven inverse Lieb geometry: A general route to $d$-wave altermagnetism in two dimensions Relevance Score: 3.1698 Authors: Geethanjali S, Katsunori Wakabayashi, Sasmita Mohakud Link: http://arxiv.org/abs/2604.10768v2 Summary: This study proposes a universal approach to realize two-dimensional d-wave altermagnetism through vacancy-induced structural reconstruction. Taking V₂X₂ (X=S, Se) monolayers as examples, selective removal of chalcogen atom clusters triggers reconstruction, forming an inverse Lieb-type magnetic network: two inequivalent vanadium sites are related by C₄ rotational symmetry, carrying opposite exchange fields, which simultaneously breaks time-reversal and PT symmetries under zero net magnetization. Structural stability is confirmed by negative formation energies, phonon spectra with no imaginary frequencies, and molecular dynamics simulations at 300 K. Based on a minimal tight-binding model, after integrating out nonmagnetic corner sites as high-order terms, the effective Hamiltonian naturally yields a d-wave spin-splitting form factor of (cos kx - cos ky), quantitatively reproducing first-principles band features: spin splitting is maximal at the X and Y points, symmetry-enforced degeneracy at the M point, and a fourfold symmetric Fermi surface pattern. This mechanism is not restricted to specific chemical systems; similar behavior can be expected in any two-dimensional lattice with rotationally symmetry-related magnetic sublattices and anisotropic hopping through intermediate nonmagnetic sites. This work establishes vacancy-driven inverse Lieb magnetic network reconstruction as a universal design principle for two-dimensional d-wave altermagnets.\n4. Interplay of disorder and interaction in quantum Hall systems: from fractional quantum Hall liquids to Wigner crystals and amorphous solids Relevance Score: 3.0057 Authors: Ke Huang, Sankar Das Sarma, Xiao Li Link: http://arxiv.org/abs/2604.10642v2 Summary: This study systematically investigates the competition between disorder and interactions in two-dimensional electron systems under strong magnetic fields using classical energy minimization and exact diagonalization methods, with a focus on the transition between Wigner crystals and fractional quantum Hall liquids. The results show that as the concentration of charged impurities increases, the classical Wigner crystal evolves from a coherent crystal into short-range ordered localized domains and ultimately into an amorphous state; under a periodic potential, the structure factor of non-interacting quantum electron crystals simultaneously exhibits Bragg peaks and quantum-origin ring-like features, significantly differing from the classical case. For fractional quantum Hall liquids, short-range random disorder and quenched charged impurities drive the ground state from an incompressible liquid sequentially to a locally ordered solid state and finally to an amorphous state. Overall, random charged impurities induce a longer range of lattice order than short-range disorder. Qualitative comparison with recent scanning tunneling microscopy experiments confirms that as disorder strengthens, the system undergoes a continuous transition from a uniform incompressible fractional quantum Hall liquid to a locally ordered solid, and then to a strongly disordered amorphous solid. These findings reveal the rich interplay between disorder and interactions in quantum Hall systems and provide a theoretical basis for understanding related experimental phenomena.\n","permalink":"https://nickelates.uk/en/posts/2026-04-12-arxiv-daily/","summary":"\u003cblockquote\u003e\n\u003cp\u003e\u003cstrong\u003eDaily Overview\u003c/strong\u003e:\nToday\u0026rsquo;s highlighted work focuses on the study of physical mechanisms closely related to the field of nickel-based superconductivity. Although no papers directly addressing nickelates were present, several studies provided important insights into core topics such as quantum criticality, d-wave pairing, and magnetic order. [1] Using optical low-temperature experiments, the electrodynamics of disordered NbN, granular Al, and the heavy-fermion compound CeCoIn5 were systematically investigated, revealing Higgs modes, Goldstone modes, and hidden Fermi liquid behavior in quantum critical superconductors. These phenomena are directly related to possible quantum critical points and unconventional pairing mechanisms in nickel-based superconductivity. [2] Spin-resolved photoemission spectroscopy clarified the magnetic controversy in RuO₂, indicating surface ferrimagnetism rather than altermagnetism, providing a comparative case for understanding the influence of oxygen coordination environments on magnetism in nickel-based superconductors. [3] A universal design principle for vacancy-driven two-dimensional d-wave altermagnets was proposed, characterizing the symmetry of d-wave spin splitting, which is consistent with the symmetry of d-wave pairing in nickel-based superconductors. This design approach may inspire the exploration of similar electronic structure reconstructions in nickel-based superconducting systems. [4] The competition between disorder and interactions in quantum Hall systems was systematically studied, revealing the transition from fractional quantum Hall liquids to Wigner crystals. The concept of the many-body phase diagram can provide an analogy for the competition between charge order and superconductivity in nickel-based superconductors. These works deepen the understanding of quantum phenomena related to nickel-based superconductivity from various perspectives.\n\u003cstrong\u003earXiv submission processing window\u003c/strong\u003e: 2026-04-12 12:58 to 2026-04-12 18:34 UTC.\u003c/p\u003e","title":"arXiv Daily: nickelate superconductors 2026-04-12"},{"content":" Daily Overview: Today\u0026rsquo;s highlights focus on the decoupling behavior of the pseudogap and superconductivity in copper oxide superconductors under high pressure, as well as predictions of the electronic structure of strongly coupled multiband two-dimensional superconductors. Although this issue does not directly include original research on nickelates, the pressure-driven separation of the pseudogap onset temperature and gap amplitude in cuprate superconductors, the phenomenological model of the universal metallic state, and the discovery of multiband strong-coupling superconductivity in hexagonal BP₃ monolayers are all highly relevant to core issues currently of interest in nickelate superconductivity, such as pairing mechanisms, gap structures, and electron-phonon coupling. These findings provide valuable physical insights and theoretical approaches for understanding the superconducting state in nickelates. arXiv submission processing window: 2026-04-10 20:38 to 2026-04-11 18:22 UTC.\n1. Ultrafast decoupling of the pseudogap from superconductivity in a pressurized cuprate Relevance Score: 4.1931 Authors: Yanghao Meng, Wenjin Mao, Liucheng Chen, Elbert E. M. Chia, Yifeng Yang, Jianlin Luo, Lin Zhao, Xingjiang Zhou, Xiaohui Yu, Xinbo Wang Affiliations: University of Chinese Academy of Sciences, Chinese Academy of Sciences, Nanyang Technological University, Songshan Lake Materials Laboratory Link: http://arxiv.org/abs/2604.10207v1 Summary: Using ultrafast optical spectroscopy, the research team mapped the high-pressure phase diagram of underdoped Bi₂Sr₂CaCu₂O₈₊δ up to 37 GPa under hydrostatic pressure. By decomposing quasiparticle dynamics in the time domain, they extracted the pseudogap onset temperature T*, the superconducting critical temperature Tc, and their corresponding energy gaps ΔPG and ΔSC. The results reveal a significant divergence of the pseudogap under pressure: T* monotonically increases to over 300 K, while ΔPG is continuously suppressed; conversely, Tc and ΔSC exhibit a correlated dome-shaped evolution, with the coupling ratio 2ΔSC/kBTc dropping sharply at around 8 GPa, marking a dimensional crossover from two-dimensional fluctuations to three-dimensional phase coherence. When the pressure increases to 37 GPa, the superconducting condensate is completely quenched and the system enters an insulating state. These findings demonstrate that the pseudogap and superconductivity are governed by distinct microscopic degrees of freedom, with their thermodynamic onset temperature and gap magnitude decoupling under pressure, thereby providing stringent experimental constraints for understanding the pairing mechanism of high-temperature superconductivity.\n2. Hidden Universal Metal in Cuprate Superconductors Relevance Score: 4.1802 Authors: Abigail Lee, Juergen Haase Link: http://arxiv.org/abs/2604.10133v1 Summary: Based on nuclear relaxation data for planar copper and oxygen in the literature, this study develops a simple phenomenological model. Its core finding is the existence of a universal metallic state in all cuprate superconductors, characterized by the relationship 1/(⁶³T₁⊥)T_c ≈ 25/Ks between the copper nuclear relaxation rate and the critical temperature, meaning T_c is directly linked to the copper relaxation rate. Above T_c, as temperature increases, this universal metallic state crosses into a strange metal region, with the relaxation rate gradually deviating from the linear metallic behavior. Planar oxygen relaxation exhibits metallic behavior in the overdoped region, but in underdoped materials, it is influenced by a doping-dependent and temperature-independent pseudogap, deviating only at low energies. The anisotropy of copper relaxation varies with doping (decreasing from approximately 3.6 at low doping to about 1 at high doping), and this anisotropy directly determines the maximum critical temperature of each system, thus closely connecting to the universal metallic state, suggesting that the relaxation must be described by two components. This phenomenological model provides a new foundation for understanding the cuprate phase diagram.\n3. Strong Electron-Phonon Coupling and Multiband Superconductivity in Hexagonal BP3 Monolayer Relevance Score: 4.0303 Authors: Jakkapat Seeyangnok, Udomsilp Pinsook Link: http://arxiv.org/abs/2604.10026v1 Summary: Using first-principles calculations combined with anisotropic Migdal-Eliashberg theory, we systematically investigate the structural, electronic, and superconducting properties of hexagonal BP3 monolayer. The optimized structure exhibits a stable and slightly buckled configuration, with phonon spectra revealing high-frequency vibration modes associated with B–P bonds. Band structure calculations indicate a multiband metallic state, where electronic states near the Fermi level primarily originate from the pz orbitals of boron and phosphorus atoms, forming two distinct Fermi surfaces. The electron–phonon coupling is strong, with a total coupling constant λ = 1.59, mainly contributed by low-frequency and mid-frequency phonon modes. Solving the anisotropic Migdal-Eliashberg equations yields a superconducting transition temperature Tc = 9.7 K. The superconducting state exhibits a nodeless but anisotropic gap structure, with two gap values of approximately 2.25 and 1.74 meV corresponding to different Fermi surfaces. These results identify BP3 monolayer as a strongly coupled, multiband two-dimensional superconductor and highlight the important role of orbital hybridization in electron–phonon-mediated superconductivity in low-dimensional systems.\n4. Exchange Frustration and Topological Magnetism in Electrostatically Doped SrRuO3 Relevance Score: 3.6839 Authors: Naafis Ahnaf Shahed, Himanshu Mavani, Zhonglin He, Kai Huang, Mohamed Elekhtiar, Evgeny Y. Tsymbal Affiliations: University of Nebraska Link: http://arxiv.org/abs/2604.10019v1 Summary: This study, employing first-principles calculations combined with atomistic Monte Carlo simulations, reveals that ferroelectric polarization can electrostatically modulate exchange frustration in the itinerant ferromagnet SrRuO₃. The results show that electrostatic hole doping renormalizes competing exchange interactions, driving SrRuO₃ from its bulk ferromagnetic ground state into a frustrated regime, while electron doping largely preserves ferromagnetism. At the BaTiO₃/SrRuO₃ interface, polarization-induced charge depletion modulates layer-dependent exchange coupling, enhancing competition among nearest-neighbor, next-nearest-neighbor, and third-nearest-neighbor exchanges, thereby stabilizing a sequence of magnetic phases depending on thickness and external magnetic field, including stripe and helical states, topological meron and bimeron textures, and various skyrmionic states. Through a minimal spin model, exchange frustration is identified as the primary control parameter governing these evolutions, while magnetic anisotropy, Dzyaloshinskii-Moriya interaction, and external magnetic field select the final topological structures. This work establishes electrostatic doping as an effective route to engineer frustration and topological magnetism in itinerant oxide metals.\n5. How Does Intercalation Reshape Layered Structures? A First-Principles Study of Sodium Insertion in Layered Potassium Birnessite Relevance Score: 3.4615 Authors: Adriana Lee Punaro, Daniel Maldonado-Lopez, Jorge L. Cholula-Díaz, Marcelo Videa, Jose L. Mendoza-Cortes Affiliations: Michigan State University, Tecnológico de Monterrey Link: http://arxiv.org/abs/2604.09891v1 Summary: Using first-principles calculations based on hybrid density functional theory, this work systematically investigates the intercalation process of sodium ions in layered potassium birnessite (K₁.₃₃Mn₃O₆). Structural stability is analyzed via formation energies, while the diffusion energy barriers of sodium and potassium ions in the interlayer are calculated using transition state theory, and Raman spectra simulations correlate vibrational modes with structural changes. X-ray diffraction and geometric analysis reveal the evolution of lattice parameters and planar density upon intercalation, with binding energy analysis indicating weaker lattice bonding at sodium saturation. In terms of electronic properties, spin-polarized density of states shows that intercalation significantly alters the oxidation state of manganese, lattice distortion, and symmetry, leading to tunable band gaps and magnetic behavior, with certain structures exhibiting bipolar magnetic semiconductor characteristics, offering potential applications in spintronics. This work provides a comprehensive description of the evolution of structural, vibrational, diffusive, and electronic properties during the co-intercalation process, offering theoretical guidance for the application of birnessite in next-generation energy, electronic, and spintronic devices.\n6. Comment on arXiv:2510.13767; Structural origin of resonant diffraction in RuO_2 (DOI: 10.1103/yr5q-1v1s) Relevance Score: 3.2459 Authors: Stephen W. Lovesey Link: http://arxiv.org/abs/2604.10105v1 Summary: Occhialini et al.\u0026rsquo;s resonant X-ray Bragg diffraction study of RuO₂ (arXiv:2510.13767) contains serious errors: the scattering amplitude formulas (Eqs. 14 \u0026amp; 16) used in both the main text and supplementary materials are incorrect, derived from a previously erroneous reference (Phys. Rev. Lett. 122, 017202) while ignoring the correct published result (Phys. Rev. B 105, 014403). The correct magnetic symmetry is P4₂\u0026rsquo;/mnm\u0026rsquo;, under which nonmagnetic (Templeton \u0026amp; Templeton, T\u0026amp;T) diffraction and magnetic diffraction are phase-shifted by 90° with orthogonal intensities, yielding no interference. The intensity data presented by Occhialini et al. violate this symmetry, rendering their conclusions and footnote SM[54] misleading. In reality, the observed intensity at the reflection vector (0,0,1) arises purely from T\u0026amp;T diffraction with no axial magnetic dipole contribution, and the symmetry corresponds to a chiral magnetic structure where Bragg spot intensities change upon reversal of incident X-ray helicity.\n7. Continuous PT-Symmetry Breaking as a Design Variable for Giant Altermagnetic Spin Splitting Relevance Score: 3.2265 Authors: Kichan Chun, Gunn Kim Link: http://arxiv.org/abs/2604.10173v1 Summary: By elevating the traditional binary symmetry judgment to a continuous scalar—the motif symmetry breaking index (MSBI)—this study directly quantifies PT symmetry breaking between antiparallel magnetic motifs from crystallographic coordinates, eliminating reliance on spin-polarized density functional theory (DFT). Using an XGBoost surrogate model trained on 3,851 DFT-labeled binary structures and SHAP analysis, three dominant descriptors are identified: MSBI (symmetry-breaking axis), motif packing fraction MPF (superexchange axis), and p/d electron ratio (covalency axis), each corresponding to experimentally tunable parameters. A comparison between VO and CrSb within the same P6₃/mmc host lattice demonstrates that compositional change alone can enhance the spin splitting energy (SSE) sevenfold. Bayesian optimization, independently validated by DFT, reproduces α-NiS (SSE = 0.823 eV) as a cross-validation and identifies three previously unknown high-SSE candidates—square-planar FeS (1.297 eV), octahedral CoS (1.103 eV), and FeAs (1.089 eV)—all achieving SSE values at or exceeding that of CrSb. This work generalizes the square-planar Fe-S coordination motif as a transferable structural unit for generating giant altermagnetic spin splitting, thus advancing altermagnet design from symmetry classification to continuous quantitative optimization.\n8. NaCl-Assisted Growth of Ferroelectric SnSe Nanosheets with Spin Glass-like Behavior Relevance Score: 3.1648 Authors: Huiwen Xu, Hanxiang Wu, Chang Li, Fei Pang Affiliations: Renmin University of China Link: http://arxiv.org/abs/2604.10067v2 Summary: High-quality single-crystal SnSe nanosheets were successfully synthesized via NaCl-assisted chemical vapor deposition, where the addition of NaCl significantly enhanced the surface coverage of the nanosheets with minimal impact on their lateral dimensions. X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy characterized their crystal structure and composition. Piezoresponse force microscopy directly observed ferroelectric domains, exhibiting clear butterfly-shaped amplitude loops and nearly 180° phase switching at room temperature, confirming intrinsic ferroelectricity and reversible polarization switching. Magnetic measurements revealed a hysteresis loop in SnSe nanosheets at 2 K, indicating weak ferromagnetism, while spin-glass behavior was observed below 115 K, attributed to the presence of SnSe2 impurities. This work establishes a route for the controllable synthesis of SnSe nanosheets, laying the foundation for further investigation of their ferroelectric properties.\n9. Emergent Topological Universality and Marginal Replica Symmetry Breaking in Gauge-Correlated Spin Glasses Relevance Score: 3.0309 Authors: Alok Yadav Link: http://arxiv.org/abs/2604.10309v1 Summary: This paper presents a theoretical framework to explain the anomalous finite-temperature critical transition observed in recent tensor network sampling of two-dimensional Nishimori spin glasses, revealing that the circumvention of Monte Carlo dynamical traps via discrete Z₂ gauge constraints fundamentally alters the universality class of the system. By mapping the disorder distribution in the algorithm onto a two-dimensional Ising conformal field theory, the authors demonstrate that the spatial variance induced at the gauge field critical point generates a fractional momentum operator, driving the dynamic upper critical dimension to zero. This edge topological structure suppresses replica coupling vertices, leading to an infinite-order Berezinskii-Kosterlitz-Thouless-type phase transition and non-integrable replicon divergence, predicting an instability toward a phase with one-step replica symmetry breaking. Using the spectral angle transfer matrix renormalization group method, the topological scaling form ( G((T-T_c)\\ln(L/L_0)) ) is quantitatively verified on macroscopic scales (lattice size ( L = 1024 )), and after isolating lattice artifacts from the continuum field theory, the fundamental lattice metric ( L_0 \\approx 0.94 ) is recovered, thereby conclusively confirming the existence of a topologically driven novel spin glass phase distinct from the standard Edwards-Anderson model.\n10. Probing lattice fluctuations using solid-state high-harmonic spectroscopy Relevance Score: 3.0291 Authors: Lance Hatch, Navdeep Rana, Shoushou He, Jessica Yu, Boyang Zhao, Yu Zhang, Haidan Wen, Xavier Roy, Lun Yue, Mette Gaarde, Hanzhe Liu Affiliations: Binghamton University, Columbia University, Argonne National Laboratory, Louisiana State University, Purdue University Link: http://arxiv.org/abs/2604.10304v1 Summary: Through experimental measurements of high-order harmonic generation (HHG) in the superatomic semiconductor Re₆Se₈Cl₂ as a function of temperature, combined with first-principles calculations and simulations based on the semiconductor Bloch equations, the significant influence of thermal lattice fluctuations on solid-state HHG is systematically revealed. The results show that as the temperature decreases, the high-order harmonic yield increases slowly above 50 K, but sharply below 50 K, a behavior that closely coincides with the temperature range in which thermal occupation of low-frequency optical phonon modes is suppressed. The theoretical model indicates that thermal lattice fluctuations suppress harmonic emission through two mechanisms: on one hand, the acceleration path of electron-hole pairs within a single distorted lattice configuration is perturbed, reducing the intensity of the harmonic response; on the other hand, phase dispersion introduced among different lattice configurations disrupts the constructive interference of coherent harmonics. This effect can be equivalently described as a temperature-dependent effective electronic dephasing time, with a more pronounced impact on higher-order harmonics. The findings not only verify the high sensitivity of solid-state HHG to lattice thermal fluctuations but also provide a new route to explore dephasing mechanisms in strong-field electron dynamics by exploiting the tunable electron-phonon interactions of superatomic crystals, offering direct reference value for strong-field phenomena such as lightwave electronics and Floquet engineering.\n11. Probing topology in thin films with quantum Sondheimer oscillations Relevance Score: 3.0081 Authors: Léo Mangeolle, Johannes Knolle Link: http://arxiv.org/abs/2604.10141v1 Summary: The paper proposes a universal theory of quantum Sondheimer oscillations (SO) for detecting the band topology of thin films in the quantum limit under strong magnetic fields. Unlike conventional Shubnikov-de Haas (SdH) oscillations, where topological information is only encoded in the oscillation phase, the oscillation frequency of quantum SO is directly modified by band topology, enabling direct and robust access to the complete Landau level spectrum. Using a minimal model with a tunable Berry phase, the study demonstrates this mechanism: in the Fourier spectrum of quantum SO, the Landau level energy directly corresponds to the oscillation frequency, allowing topological features such as the zero mode to be unambiguously distinguished by the positions of frequency peaks. Furthermore, the paper analyzes the effects of damping mechanisms such as temperature, quasiparticle lifetime, and surface roughness on oscillation amplitudes, and points out that quantum SO should also be observable in thermodynamic signals. This work provides a new approach for directly probing the topological properties of electronic structures using magnetoresistance oscillations in thin films.\n","permalink":"https://nickelates.uk/en/posts/2026-04-11-arxiv-daily/","summary":"\u003cblockquote\u003e\n\u003cp\u003e\u003cstrong\u003eDaily Overview\u003c/strong\u003e:\nToday\u0026rsquo;s highlights focus on the decoupling behavior of the pseudogap and superconductivity in copper oxide superconductors under high pressure, as well as predictions of the electronic structure of strongly coupled multiband two-dimensional superconductors. Although this issue does not directly include original research on nickelates, the pressure-driven separation of the pseudogap onset temperature and gap amplitude in cuprate superconductors, the phenomenological model of the universal metallic state, and the discovery of multiband strong-coupling superconductivity in hexagonal BP₃ monolayers are all highly relevant to core issues currently of interest in nickelate superconductivity, such as pairing mechanisms, gap structures, and electron-phonon coupling. These findings provide valuable physical insights and theoretical approaches for understanding the superconducting state in nickelates.\n\u003cstrong\u003earXiv submission processing window\u003c/strong\u003e: 2026-04-10 20:38 to 2026-04-11 18:22 UTC.\u003c/p\u003e","title":"arXiv Daily: nickelate superconductors 2026-04-11"},{"content":" Daily Overview: Today\u0026rsquo;s highlights focus on deepening the understanding of the electronic structure of mixed Ruddlesden-Popper nickelates. [1] Using scanning transmission electron microscopy combined with electron energy-loss spectroscopy, it was revealed that the formation of the superconducting phase in La₃Ni₂O₇₋δ thin films is closely related to oxygen stoichiometric homogeneity, epitaxial strain, and specific stacking polytypes, establishing a theoretical framework in which oxygen content, lattice strain, and structural ordering collectively regulate the metastable superconducting phase. Meanwhile, [2] a continuous linear increase in the superconducting transition temperature under high pressure was achieved in freestanding infinite-layer Nd₀.₈₅Sr₀.₁₅NiO₂ thin films, rising from 17 K at ambient pressure to approximately 74 K without saturation. This pressure evolution behavior is distinctly different from the overdoping suppression observed in cuprates and bilayer nickelates, indicating that the pairing strength in infinite-layer nickelates can be significantly enhanced by lattice compression. Furthermore, [3] pressure-induced superconducting transitions observed in the d-wave altermagnetic candidate material CsV₂Se₂O, following an evolution path from a weakly insulating parent phase through electronic reconstruction to strange metal transport and superconducting behavior, are highly similar to the common characteristics of unconventional superconductors such as cuprates and nickel oxides, providing a cross-reference for understanding possibly universal electronic state transitions in nickel-based superconductivity. arXiv submission processing window: 2026-04-09 20:00 to 2026-04-10 18:31 UTC.\n1. Decoding Superconductivity in La$_3$Ni$_2$O$_{7-δ}$ Thin Films via Ozone-Driven Structure and Oxidation Tuning Relevance Score: 5.8745 Authors: Mathieu Flavenot, Hoshang Sahib, Jérôme Robert, Marc Lenertz, Gilles Versini, Laurent Schlur, Alexandre Gloter, Nathalie Viart, Daniele Preziosi Affiliations: Université de Strasbourg, Université Paris-Saclay Link: http://arxiv.org/abs/2604.09807v1 Summary: This study presents a detailed structural analysis of epitaxial La₃Ni₂O₇₋δ thin films using scanning transmission electron microscopy combined with electron energy loss spectroscopy. The films were prepared on SrLaAlO₄ substrates via pulsed laser deposition and exhibited significantly distinct superconducting properties after different ozone annealing treatments. It was found that the stabilization of the superconducting phase is closely related to oxygen stoichiometry uniformity, epitaxial strain, and specific stacking structural motifs such as bilayers and polytypes. By correlating the rich morphology of stacking polytypes with transport behavior, a theoretical framework for understanding metastable superconducting phases in bilayer nickelate thin films was established. The results reveal the critical roles of oxygen content, lattice strain, and structural ordering in achieving ambient-pressure superconductivity, providing a clear pathway for designing new nickel-based superconducting materials.\n2. High-temperature superconductivity in Nd$_{0.85}$Sr$_{0.15}$NiO$_2$ membranes under pressure Relevance Score: 5.1582 Authors: Yonghun Lee, Mengnan Wang, Xin Wei, Yijun Yu, Wendy L. Mao, Yu Lin, Harold Y. Hwang Affiliations: SLAC National Accelerator Laboratory, Stanford University, Fudan University Link: http://arxiv.org/abs/2604.09525v1 Summary: Researchers have developed a technique to integrate free-standing infinite-layer Nd₀.₈₅Sr₀.₁₅NiO₂ thin films into diamond anvil cells, thereby overcoming the difficulties of measuring such films under high-pressure conditions. By applying pressures up to approximately 90 GPa to the films, they observed that the superconducting transition temperature (T_c) increased monotonically and linearly from about 17 K at ambient pressure to roughly 74.2 K, with an enhancement rate of approximately 0.65 K/GPa and no signs of saturation. This linear, non-saturating pressure dependence of T_c markedly differs from the pressure-induced overdoping that leads to T_c suppression in most copper oxide superconductors and bilayer nickelates, suggesting that the pairing strength in infinite-layer nickelates can be elevated to unexpectedly high levels. Furthermore, measurements of the upper critical field and coherence length confirm the pressure-induced enhancement of the superconducting state. This study provides a new pathway for continuously enhancing superconductivity through lattice compression, and the developed free-film high-pressure technique holds promise for broad application to other two-dimensional materials.\n3. Pressure-Induced Superconducting-like Transition in the $\\it d$-wave Altermagnet Candidate CsV$_2$Se$_2$O Relevance Score: 4.3511 Authors: Yuanzhe Li, Yilin Han, Liu Yang, Wanli He, Pengda Ye, Wencheng Huang, Jiabin Qiao, Yuemei Li, Xiaodong Sun, Tingli He, Jiayi Han, Yuxiang Chen, Ruifeng Tian, Hao Sun, Yuwei Liu, Feng Wu, Baoshan Song, Zhengtai Liu, Mao Ye, Yaobo Huang, Kenichi Ozawa, Ji Dai, Massimo Tallarida, Shengtao Cui, Jie Chen, Meiling Jin, Wayne Zheng, Chaoyu Chen, Zhiwei Wang, Zhi-Ming Yu, Xiang Li, Yugui Yao Affiliations: Songshan Lake Materials Laboratory, Southern University of Science and Technology, ALBA Synchrotron, Chinese Academy of Sciences, University of Science and Technology of China, Beijing Institute of Technology, High Energy Accelerator Research Organization (KEK) Link: http://arxiv.org/abs/2604.09457v1 Summary: CsV2Se2O (CVSO), a quasi-two-dimensional d-wave altermagnet candidate, exhibits a weak insulating parent phase at ambient pressure accompanied by a density-wave-like anomaly near 100 K, with bulk properties consistent with a G-type compensated antiferromagnetic background. Combined experimental and theoretical investigations of its lattice, electronic structure, and transport properties reveal that under applied pressure, the density-wave features are suppressed, magnetoresistance transitions from predominantly negative to positive, and a reproducible superconducting-like drop in resistance emerges below approximately 3 K, which can be suppressed by a magnetic field. Room-temperature X-ray diffraction shows that the average crystal symmetry remains unchanged during compression, but lattice parameters and volume display pronounced compressibility anomalies over specific pressure ranges, indicating an isostructural phase transition. The resulting pressure-tuned phase diagram reveals a progression from a weak insulating parent phase through electronic reconstruction to strange metal transport and superconducting-like behavior, a pathway strikingly similar to the common phenomenology of unconventional superconductors such as cuprates and nickelates.\n4. Nonmonotonic Evolution of the Superconducting Transition Temperature and Robust Multigap Extended s-wave + s-wave Pairing in Zn-Substituted FeSe Single Crystals Relevance Score: 4.1047 Authors: Han-Shu Xu, Changhao Ding, Guanyin Gao, Xin Zhang, Xinyu Yin, Xucai Kan, Jiaping Hu, Wen Xie, Wensen Wei, Yuxiao Hou, Keyu An, Haoxiang Li, Kaibin Tang, Yu-Yan Han Link: http://arxiv.org/abs/2604.09172v1 Summary: This study systematically investigates the effect of non-magnetic Zn substitution on the superconductivity of FeSe by synthesizing high-quality Fe₁₋ₓZnₓSe single crystals (x = 0–0.023). Magnetization, electrical transport, and low-temperature specific heat measurements indicate that all doped samples maintain bulk superconductivity, but the superconducting transition temperature T_c exhibits a pronounced non-monotonic evolution with increasing Zn content: initially suppressed, then partially recovered, followed by further suppression, suggesting that the underlying mechanism cannot be explained solely by impurity-induced pair breaking. Low-temperature specific heat data uniquely support a two-gap model consisting of an isotropic s-wave gap and an anisotropic extended s-wave gap, while a single-gap model or other pairing symmetries fail to fit the data. The relative weights of the two gap components remain nearly unchanged with doping, indicating that Zn substitution introduces only weak interband scattering, thereby preserving the stability of the multiband superconducting state. These results reveal the robustness of multiband superconductivity in FeSe and provide strong constraints on possible pairing mechanisms, highlighting the crucial roles of the multiband electronic structure and anisotropic gap formation.\n5. The hidden ferroelectric chiral ground state of silver niobate Relevance Score: 3.9150 Authors: Safari Amisi, Fernando Gómez-Ortiz, Eric Bousquet, Philippe Ghosez Link: http://arxiv.org/abs/2604.09193v1 Summary: Silver niobate (AgNbO₃) is typically classified as an antiferroelectric, yet its low-temperature structure has long been controversial. Through first-principles calculations, this study reveals a previously overlooked rhombohedral ferroelectric phase with R3 symmetry, which energetically competes strongly with various earlier proposed structures and ultimately emerges as the thermodynamic ground state. This phase is distinctive not only for its ferroelectricity but also for its structural chirality, arising from an improper coupling between polarization and in-phase oxygen octahedral rotation along the [111] direction, resulting in a ferrochiral state where local chiral motifs do not fully cancel. Consequently, this phase exhibits natural optical activity comparable to that of quartz. Despite its energetic favorability, kinetic constraints may hinder its experimental observation, potentially explaining the persistent controversy surrounding the low-temperature structure of silver niobate. The paper systematically analyzes the lattice dynamics, mode coupling, and energy landscape of this phase, confirming it as the globally lowest-energy configuration and offering new insights into the complex low-temperature phase diagram of this material.\n6. Evolution of crystal field and intraionic interactions in the ilmenite $A$IrO$_3$ ($A$ = Mg, Zn, Cd) and hyperhoneycomb $β$-ZnIrO$_3$ Relevance Score: 3.8149 Authors: Yuya Haraguchi, Hiroko Aruga Katori, Kenji Ishii, Hakuto Suzuki Link: http://arxiv.org/abs/2604.08934v1 Summary: 通过Ir L₃边共振非弹性X射线散射（RIXS）对钛铁矿型A IrO₃（A = Mg, Zn, Cd）和超蜂窝型β-ZnIrO₃的局域电子结构进行了多峰分析，系统揭示了晶体场和离子内相互作用参数随A位离子半径的系统演化。随着A位离子半径增大，三角畸变增强，自旋-轨道耦合减弱，导致与理想J=1/2态的显著偏离，从而为CdIrO₃中增强的反铁磁相互作用提供了微观解释。值得注意的是，钛铁矿型ZnIrO₃与超蜂窝型β-ZnIrO₃的局域多峰参数几乎相同，证明两者迥异的磁基态主要源于不同的晶格拓扑结构而非单离子性质。这些结果确立了局域晶体场畸变在调控Kitaev候选材料磁哈密顿量中的核心作用。\n7. Superconductivity and competing orders in honeycomb $t$-$J$ model: interplay of lattice geometry and next-nearest-neighbor hopping Relevance Score: 3.7174 Authors: Zhi Xu, Hong-Chen Jiang, Yi-Fan Jiang Link: http://arxiv.org/abs/2604.08937v1 Summary: We systematically investigate the effects of next-nearest-neighbor hopping t\u0026rsquo; and superexchange J\u0026rsquo; = (t\u0026rsquo;/t)^2 J on superconductivity and competing orders in the extended t-J model on the honeycomb lattice using large-scale density matrix renormalization group (DMRG) simulations and slave-boson mean-field theory (SBMFT). On the YC4-0 cylinder, DMRG reveals that the doped ground state exhibits coexistence of quasi-long-range d-wave superconductivity and armchair stripe (a-stripe) orders over a wide range of t\u0026rsquo;, with the superconducting Luttinger exponent varying nonmonotonically and being optimal near t\u0026rsquo; ≈ 0.4. In contrast, on the XC cylinder, a long-range zigzag stripe phase without superconductivity emerges for t\u0026rsquo; \u0026gt; 0.5, highlighting the crucial role of boundary geometry in stabilizing competing phases. SBMFT further indicates that in the two-dimensional limit, the a-stripe is most stable over most of the phase diagram and undergoes a transition to uniform nematic d-wave superconductivity with increasing t\u0026rsquo; at 1/8 doping. The combined results from these two complementary methods suggest that a robust t\u0026rsquo;-induced superconducting phase can be stabilized in the doped extended t-J model on the honeycomb lattice.\n8. Superconducting orbital diode effect in SN bilayers Relevance Score: 3.6676 Authors: Yuriy A. Dmitrievtsev, Yakov V. Fominov Link: http://arxiv.org/abs/2604.09504v1 Summary: This study analyzes the superconducting diode effect (SDE) in diffusive superconductor-normal metal (SN) bilayers subjected to an in-plane magnetic field, with a focus on the influence of non-ideal interfaces (finite resistance) on the effect. The SDE originates from the Meissner current orbital mechanism induced by spatially inhomogeneous supercurrent density, manifesting as asymmetry in critical current and kinetic inductance for opposite current directions. The authors employ an analytical approach, focusing on the limit of weak in-plane inhomogeneity, and derive effective equations for weakly non-ideal and highly resistive interfaces. It is found that when the total bilayer thickness is much smaller than the coherence length, the SDE magnitude exhibits a nonmonotonic dependence on interface resistance: for small resistance, increasing resistance introduces additional inhomogeneity and enhances the SDE; however, when the resistance becomes too large, the proximity effect is suppressed and the SDE approaches zero. Notably, moderate interface resistance can further amplify the SDE compared to the ideal transparent interface. This work theoretically reveals the tunability of the orbital SDE by interface resistance, providing a new pathway for optimizing the performance of superconducting diodes.\n9. On the origin of superlattice stacking faults nucleation via climb of Frank partial in CoNi-based superalloys Relevance Score: 3.6422 Authors: Zhida Liang, Yinan Cui, Li Wang, Xin Liu, Bin Liu, Yong Liu, Fengxian Liu Affiliations: Tsinghua University, Central South university, University of Twente, Helmholtz-Zentrum hereon GmbH Link: http://arxiv.org/abs/2604.09329v1 Summary: This study demonstrates that in the γ′ phase of CoNi-based superalloys, superlattice intrinsic stacking faults (SISF) and extrinsic stacking faults (SESF) can form through the non-conservative climb of a/3〈111〉 Frank partial dislocations, a mechanism that is universally applicable and kinetically feasible under compression at 850 °C. High-resolution transmission electron microscopy directly observed that Frank partials located at the γ/γ′ interface can climb into the γ′ phase: positive climb generates SISF, while negative climb generates SESF, with negative climb-assisted SESF nucleation being experimentally confirmed for the first time. These Frank partials originate from the reaction between leading 30° Shockley partials and 60° mixed dislocations on conjugate {111} planes, forming an energetically stable configuration that promotes climb. Energy and kinetic analyses indicate that the reduction in stacking fault energy due to solute segregation is the primary driving force for Frank climb, enabling sustained climb and fault expansion. Quantitative comparisons further reveal that at high temperatures, solute-drag-controlled Shockley slip can achieve mobility comparable to vacancy-diffusion-controlled Frank climb. This work establishes climb-assisted fault formation as a unified deformation mechanism in the γ′ phase, demonstrating that both SISF and SESF can propagate via Frank partial climb.\n10. Realistic Pearl vortices in thin film superconductors Relevance Score: 3.4363 Authors: Aurélien Balzli, Louk Rademaker, Giulia Venditti Affiliations: University of Geneva, Leiden University Link: http://arxiv.org/abs/2604.09440v1 Summary: This paper revisits the classic problem of the magnetic field profile of vortices in thin-film superconductors by performing precise numerical simulations based on the Ginzburg-Landau theory. The study finds that for sufficiently thin films (thickness d ≲ 0.2λ), even at the intermediate Ginzburg-Landau parameter κ = 1/√2, the magnetic screening does not follow the exponential decay of bulk superconductors nor the power-law decay (1/r to 1/r³) predicted by Pearl for a point vortex core. Instead, it exhibits a universal curve that scales only with the film thickness. Although the magnetic field variation with distance differs from the classical Pearl picture—exhibiting exponential decay near the core and a thickness-dependent power law at large distances—the extracted generalized penetration depth in the two-dimensional limit is consistent with the Pearl length Λ = 2λ²/d, indicating that this length still determines the overall scale of the magnetic field distribution. The paper also quantitatively characterizes the crossover from bulk to thin-film behavior and provides different screening length scales suitable for experimental data analysis.\n11. Activation of Inner-Shell 4p-Orbital Electrons of Rubidium Driven by Asymmetric Coordination at High Pressure Relevance Score: 3.2695 Authors: Shuran Ma, Xue Cong, Yanchang Wang, Yuanzheng Chen, Zhen Liu Affiliations: Jilin University, Southwest Jiaotong University, Beijing Normal University Link: http://arxiv.org/abs/2604.08901v1 Summary: By combining first-principles crystal structure search (CALYPSO) with density functional theory (VASP) and ab initio molecular dynamics simulations, this study predicts a metastable ternary layered phase, RbBF₅, under high pressure. At pressures between 200 and 300 GPa, the Rb atoms in this phase are coordinated by 12 F atoms in a truncated cubic arrangement. This geometrically symmetric yet chemically asymmetric coordination environment breaks the degeneracy of the Rb 4p orbitals, causing crystal field splitting in which the in-plane 4pₓ,y levels shift upward significantly relative to the out-of-plane 4pz, thereby overlapping with the F 2p levels and participating in bonding, stabilizing the Rb–F layered structure. This approach overcomes the limitation of mere pressure compression, which insufficiently raises the inner-shell levels of light alkali metals such as Rb, and achieves chemical activation of inner p electrons through coordination symmetry breaking. This mechanism can be extended to lighter alkali metals such as K and Cs, providing a general design principle for realizing unconventional oxidation states and bonding modes under high pressure.\n12. Optical spin defect pairs in cubic boron nitride Relevance Score: 3.2392 Authors: Josiah E. Hsi, Islay O. Robertson, Abhijit Biswas, Jishnu Murukeshan, Valery Khabashesku, Alexander J. Healey, Erin S. Grant, David A. Broadway, Mehran Kianina, Igor Aharonovich, Pulickel M. Ajayan, Jean-Philippe Tetienne Link: http://arxiv.org/abs/2604.08737v1 Summary: In this study, optically detected magnetic resonance (ODMR) signals were observed in cubic boron nitride (cBN), with characteristics consistent with optically spin defect pairs in hexagonal boron nitride (hBN). ODMR measurements were performed at room temperature on cBN samples of varying sizes, including large crystals and micro-powders, revealing a single resonance peak that linearly shifts with the magnetic field, consistent with a spin-1/2 system, and reproducible under multiple excitation wavelengths. Through Rabi oscillation, spin relaxation, and photodynamics measurements, the charge transfer mechanism was verified: optical excitation induces electron transfer between adjacent defects, forming weakly coupled spin pairs that enable spin initialization and readout. The results indicate that ODMR in cBN originates from charge transfer between defect pairs, independent of crystal structure, supporting the material universality of this mechanism. Additionally, ODMR signals were detected from individual sub-micron cBN particles, demonstrating their potential for quantum sensing applications such as scanning magnetometry. Although current contrast and coherence times require further optimization, cBN, with its high hardness and thermal stability, offers a new platform for quantum sensing under extreme conditions.\n13. Reciprocity of Charge-Orbital-Spin Transport in Normal-Metal/Ferromagnet Heterostructures Relevance Score: 3.2340 Authors: Abhishek Erram, Akanksha Chouhan, Ashwin A. Tulapurkar Link: http://arxiv.org/abs/2604.08989v1 Summary: This study directly probed orbital torque-driven magnetization dynamics and orbital pumping within the same device by conducting two-port scattering parameter measurements on three types of heterojunction devices: Ru/Ni, Ru/Pt/CoFeB, and Co/Cu/SiO₂. The experimental results revealed that the transmission coefficients for the forward process (orbital Hall effect generating orbital torque) and the reverse process (orbital pumping accompanied by the inverse orbital Hall effect) satisfy the symmetry required by the Onsager reciprocity relation, demonstrating that reciprocal conversion among charge, orbital angular momentum, and spin angular momentum is achievable. These findings establish orbital pumping as the reciprocal counterpart of orbital torque, thereby providing a unified physical framework for orbital transport phenomena.\n14. Tantalum-Encapsulated Niobium Superconducting Resonators: High Internal Quality Factor and Improved Temporal Stability via Surface Passivation Relevance Score: 3.2337 Authors: Anas Alkhazaleh, Juan Villegas, Florent Ravaux, Alexey Zharinov Link: http://arxiv.org/abs/2604.09050v1 Summary: By depositing a thin tantalum layer in situ on the surface of niobium thin films, this study suppresses the formation of lossy Nb₂O₅ and replaces the complex surface oxides of niobium with a more uniform and stable Ta₂O₅ interface, thereby reducing the microwave loss induced by two-level systems (TLS). Nb/Ta bilayer resonators and pure niobium reference resonators were fabricated on high-resistivity silicon substrates using identical DC sputtering and wet etching processes, and characterized at millikelvin temperatures. The freshly prepared tantalum-capped devices exhibit intrinsic quality factors (Qᵢ) as high as 2.4×10⁶ in the near-single-photon regime, and their power dependence indicates a significant reduction in TLS loss at the metal–air interface; in contrast, the pure niobium devices show a lower TLS-related quality factor (Q_TLS), confirming the beneficial effect of the tantalum capping layer. After six months of aging tests, the Q_TLS of the Nb/Ta resonators experienced a moderate decrease but remained superior to that of freshly prepared pure niobium devices. These results demonstrate that a thin tantalum cap effectively improves interface quality and enhances temporal stability while remaining compatible with existing niobium-based fabrication processes, offering a viable surface passivation strategy for reducing microwave loss in quantum circuits.\n15. The effect of pressure in the crystal and magnetic structure of FeWO4 Relevance Score: 3.2122 Authors: Oscar Fabelo, Javier Gonzalez-Platas, Stanislav Savvin, Pablo Botella, Daniel Errandonea Affiliations: Universitat de Valencia, Universidad de La Laguna, Institut Laue-Langevin Link: http://arxiv.org/abs/2604.09190v1 Summary: This study employed high-pressure neutron diffraction techniques to investigate in situ the structural and magnetic changes of wolframite-type FeWO₄ under pressures up to 8.7(4) GPa and temperatures down to 30.0(5) K. Rietveld refinement of the diffraction data revealed that, although the maximum applied pressure compressed the volume by approximately 5%, the Shubnikov space group remained unchanged below the magnetic ordering temperature. However, both the orientation of the magnetic moments and the Néel temperature exhibited slight pressure-induced adjustments, consistent with existing understanding of wolframite magnetism. Additionally, the pressure-volume equation of state for FeWO₄ at 300 K was determined and compared with previous X-ray diffraction studies and density functional theory calculations. The findings confirm that the crystal structure of FeWO₄ remains highly stable within this pressure range, yet pressure can finely tune its magnetic ordering parameters.\n16. Ferromagnetic interlayer exchange coupling in a few layers of CrSBr on a gold thin film Relevance Score: 3.1926 Authors: Rixt Bosma, Darius A. Pacurar, Daniel Sade, Jingbo Wang, Nicholas Dale, Cameron W. Johnson, Sergii Grytsiuk, Alexander Rudenko, Alexander Stibor, Malte Roesner, Marcos H. D. Guimaraes, Roberto Lo Conte Affiliations: University of Groningen Link: http://arxiv.org/abs/2604.09794v1 Summary: This study directly imaged the magnetic texture of thin CrSBr flakes on a gold film using spin-polarized low-energy electron microscopy, revealing that CrSBr flakes with thicknesses below 11 nanometers exhibit a ferromagnetic ground state, rather than the A-type antiferromagnetic order typical of bulk material. Reflection electron energy spectroscopy showed distinct differences in the unoccupied density of states between thin CrSBr and bulk samples, indicating electronic band structure modification induced by the gold substrate. Combined with first-principles density functional theory calculations, the researchers attributed the stabilization of ferromagnetic order to electron transfer from the gold film to the CrSBr layers, which switches the interlayer exchange coupling from antiferromagnetic to ferromagnetic. This work demonstrates the potential for tuning the magnetic properties of two-dimensional van der Waals magnets through substrate engineering, offering a new approach for achieving controllable magnetic states in spintronic devices.\n17. Higher-order topological insulators in two-dimensional antiferromagnetic and altermagnetic chromium-based group-IV chalcogenides Relevance Score: 3.1157 Authors: Ruo-Yu Ning, Yong-Kun Wang, Shifeng Qian, Si Li, Wen-Li Yang Link: http://arxiv.org/abs/2604.08907v1 Summary: Based on first-principles calculations and theoretical analysis, this study identifies a class of monolayer chromium-based group-IV chalcogenides (CrCX₃, X = S, Se, Te, and CrSiS₃) as novel two-dimensional magnetic higher-order topological insulators. Among them, CrCX₃ and CrSiS₃ exhibit a conventional antiferromagnetic ground state while preserving PT symmetry, whereas Janus compounds Cr₂C₂S₃Se₃ and Cr₂Si₂S₃Se₃ display an altermagnetic ground state. The results demonstrate that all these monolayer materials realize a two-dimensional higher-order topological insulator phase, with nontrivial topology protected by the lattice C₃ rotational symmetry, manifested as zero-dimensional corner states carrying quantized fractional charge. Upon considering spin-orbit coupling, the system retains the higher-order topological phase with robust corner-localized states, confirming the stability of its higher-order topological properties. This discovery reveals the intrinsic connection between higher-order topology and magnetic order in two-dimensional antiferromagnetic and altermagnetic systems, providing an ideal platform for exploring higher-order topological phases and their potential applications in topological and spintronic devices.\n18. Pressure-stabilized dual-BCC polymorphism in a rhenium-based high-entropy alloy Relevance Score: 3.1059 Authors: Raimundas Sereika, Andrew D. Pope, Hunter Kantelis, Caleb M. Knight, Kallol Chakrabarty, Yogesh K. Vohra Affiliations: University of Alabama at Birmingham Link: http://arxiv.org/abs/2604.08770v1 Summary: In a near-equimolar ReNbTiZrHf high-entropy alloy, a unique metastable dual body-centered cubic (BCC) microstructure has been synthesized via high-pressure driving. Under ambient pressure, the alloy initially consists of a two-phase mixture of hexagonal C14 and BCC phases; upon compression above approximately 40 GPa, the hexagonal phase undergoes a selective diffusionless transformation to form a second crystallographically distinct BCC polymorph (BCC2), while the original BCC phase (BCC1) remains stable. Upon decompression, the BCC2 phase is kinetically trapped, resulting in a dual-BCC state unattainable through conventional heat treatment. The pressure-stabilized BCC2 phase, enriched in rhenium, inherits the high stiffness (bulk modulus ~290 GPa) of the hexagonal parent phase, creating a pronounced elastic and mechanical contrast with the softer original BCC1 matrix (~180 GPa). This study demonstrates that pressure can effectively modulate the flat free-energy landscape of chemically complex alloys, providing a robust pathway for polymorph engineering and metastable phase design in refractory high-entropy alloys.\n19. Oxygen-Mediated Phase Evolution in Sputtered Cu-W-O: Insights into Surface Chemistry Variability Relevance Score: 3.1053 Authors: José Montero-Amenedo Link: http://arxiv.org/abs/2604.09401v1 Summary: Copper tungsten oxide ternary thin films were deposited by DC magnetron co-sputtering under controlled oxygen partial pressures, followed by thermal annealing. Low oxygen conditions promoted the formation of a single CuWO4 phase, whereas higher oxygen partial pressures led to mixed phases of CuWO4 and Cu3WO6. X-ray diffraction and spectrophotometric analyses revealed phase coexistence and variations in preferred orientation as a function of deposition conditions. Through rigorously validated X-ray photoelectron spectroscopy, systematic shifts in the Cu 2p₃/₂ binding energy were observed, while the W 4f core levels remained stable across all oxygen partial pressures. Wagner plot analysis confirmed that these shifts were predominantly governed by initial-state effects, reflecting changes in the ground-state electronic structure of copper and Cu–O–W hybridization, rather than final-state screening effects. This study demonstrates that sputtered Cu–W–O films nominally identified as CuWO₄ can exhibit significantly different structural and electronic states under varied synthesis conditions, underscoring the need for rigorous characterization to ensure reproducibility in ternary oxide research.\n20. Effects of Compression on the Local Iodine Environment in Dipotassium Zinc Tetraiodate(V) Dihydrate K2Zn(IO3)4.2H2O Relevance Score: 3.0917 Authors: Daniel Errandonea, Robin Turnbull, Hussien H. H. Osman, Zoulikha Hebboul, Pablo Botella, Neha Bura, Peijie Zhang, Jose Luis Rodrigo Ramon, Josu Sanchez-Martin, Catalin Popescu, Francisco J. Manjon Affiliations: Universitat de Valencia, Universitat Politècnica de València, CELLS-ALBA Synchrotron Light Facility, Université Amar Telidji de Laghouat Link: http://arxiv.org/abs/2604.09140v1 Summary: This study, by combining synchrotron X-ray diffraction, density functional theory, and electron topology analysis, reveals the effect of compression on the local iodine environment in K₂Zn(IO₃)₄·2H₂O. Under pressure, iodine atoms gradually transition from original covalent I–O bonds and secondary halogen I···O interactions to O–I–O electron-deficient multicenter bonds, leading to the transformation of IO₃ trigonal pyramids into IO₆ units and the formation of an infinite two-dimensional iodate network, breaking the molecular isolation of iodate groups. This hypercoordination also promotes the formation of multicenter O–H–O hydrogen bonds. K₂Zn(IO₃)₄·2H₂O is one of the most compressible iodates studied to date, with a bulk modulus of only 22(3) GPa. Optical absorption and band structure calculations indicate that pressure-induced structural changes significantly alter the electronic structure, narrowing the band gap from 4.2(1) eV at ambient pressure to 3.4(1) eV at 20 GPa. This work elucidates the evolution of structure, bonding, and electronic properties of complex iodates under compression.\n","permalink":"https://nickelates.uk/en/posts/2026-04-10-arxiv-daily/","summary":"\u003cblockquote\u003e\n\u003cp\u003e\u003cstrong\u003eDaily Overview\u003c/strong\u003e:\nToday\u0026rsquo;s highlights focus on deepening the understanding of the electronic structure of mixed Ruddlesden-Popper nickelates. [1] Using scanning transmission electron microscopy combined with electron energy-loss spectroscopy, it was revealed that the formation of the superconducting phase in La₃Ni₂O₇₋δ thin films is closely related to oxygen stoichiometric homogeneity, epitaxial strain, and specific stacking polytypes, establishing a theoretical framework in which oxygen content, lattice strain, and structural ordering collectively regulate the metastable superconducting phase. Meanwhile, [2] a continuous linear increase in the superconducting transition temperature under high pressure was achieved in freestanding infinite-layer Nd₀.₈₅Sr₀.₁₅NiO₂ thin films, rising from 17 K at ambient pressure to approximately 74 K without saturation. This pressure evolution behavior is distinctly different from the overdoping suppression observed in cuprates and bilayer nickelates, indicating that the pairing strength in infinite-layer nickelates can be significantly enhanced by lattice compression. Furthermore, [3] pressure-induced superconducting transitions observed in the d-wave altermagnetic candidate material CsV₂Se₂O, following an evolution path from a weakly insulating parent phase through electronic reconstruction to strange metal transport and superconducting behavior, are highly similar to the common characteristics of unconventional superconductors such as cuprates and nickel oxides, providing a cross-reference for understanding possibly universal electronic state transitions in nickel-based superconductivity.\n\u003cstrong\u003earXiv submission processing window\u003c/strong\u003e: 2026-04-09 20:00 to 2026-04-10 18:31 UTC.\u003c/p\u003e","title":"arXiv Daily: nickelate superconductors 2026-04-10"},{"content":" Daily Overview: Today\u0026rsquo;s highlights focus on the electronic structure, superconducting mechanism, and material properties of bilayer Ruddlesden-Popper nickelate superconductors. In [1], the three-dimensional band structure of (La,Pr,Sm)₃Ni₂O₇ thin films was resolved using low-temperature ARPES, revealing orbital-dependent dimensionality and a superconducting gap driven by the dz² orbital (2Δ/kBTc~8), emphasizing the critical role of the third dimension. [2] attributed the two-step superconducting transition in La₂PrNi₂O₇₋δ thin films to granular superconductivity through transport and structural characterization, pointing to oxygen inhomogeneity as the primary factor limiting zero-resistance temperature. [3] used D-TRILEX many-body theory to find that competition between multiorbital and nonlocal correlations in the normal state of bilayer nickelates can form spin-polaron bound states, providing a new explanation for the controversy over ARPES spectral features. [4] employed variational Monte Carlo methods to obtain an orbital-selective d-wave superconducting state in a two-band t-J model, indicating that the quasi-localized dₓ²⁻y² orbital competes with superconductivity, and suppressing its participation may enhance Tc. These works deepen the understanding of nickelate superconductivity from both experimental and theoretical perspectives. arXiv submission processing window: 2026-04-08 23:37 to 2026-04-09 19:57 UTC.\n1. Three-Dimensional Electronic Structures in Superconducting Ruddlesden-Popper Bilayer Nickelate Films Relevance Score: 5.5252 Authors: Yueying Li, Lizhi Xu, Wei Lv, Zihao Nie, Zechao Wang, Yu Miao, Jianchang Shen, Guangdi Zhou, Wenhua Song, Heng Wang, Haoliang Huang, Junfeng He, Jin-Feng Jia, Peng Li, Qi-Kun Xue, Zhuoyu Chen Affiliations: Southern University of Science and Technology, Tsinghua University, University of Science and Technology of China, Shanghai Jiao Tong University, Quantum Science Center of Guangdong-Hong Kong-Macao Greater Bay Area Link: http://arxiv.org/abs/2604.08430v2 Summary: By employing a low-temperature ultrahigh-vacuum dark-box transfer technique to preserve sample surface quality, this study systematically resolves the three-dimensional electronic band structure of superconducting (La,Pr,Sm)₃Ni₂O₇/SrLaAlO₄ thin films using angle-resolved photoemission spectroscopy (ARPES) with multiple photon energies. The experiments reveal orbital-dependent dimensionality: the dx²-y²-dominated band exhibits quasi-two-dimensional character, while the dz²-dominated γ band displays clear kz dispersion. Finite gaps are observed along high-symmetry directions for all detected bands, with temperature-dependent analysis of the γ band indicating a superconducting gap of approximately 18 meV and a ratio 2Δ/kBTc ~ 8, far exceeding the weak-coupling BCS limit. Moreover, suppression of spectral weight near the Fermi level persists above the superconducting transition temperature, and ubiquitous waterfall-like spectral features are observed, indicating a significant influence of electron correlations. These findings underscore the critical role of the third dimension and the dz² orbital in the nickelate superconducting mechanism, imposing important constraints on theoretical models.\n2. Granular Superconductivity in La$_{2}$PrNi$_{2}$O$_{7-δ}$ Thin Films Relevance Score: 5.3446 Authors: Ziao Han, Lifen Xiang, X. J. Zhou, Zhihai Zhu Link: http://arxiv.org/abs/2604.07807v1 Summary: Research indicates that the two-step superconducting transition observed in La₂PrNi₂O₇₋δ thin films originates from their granular superconducting nature, where two superconducting phases with distinct critical temperatures coexist and couple through a Josephson junction network. For films grown via pulsed laser deposition and subsequently ozone-annealed, transport measurements reveal a pronounced secondary low-temperature transition even when the residual resistance is minimal near 30 K, resulting in a zero-resistance temperature of only about 10 K. The hysteresis in magnetoresistance and the sensitive response to weak magnetic fields align with the effective field model of granular superconductors, ruling out the possibility of a spin-glass phase. Structural characterization identifies oxygen inhomogeneity and local structural disorder, such as monolayer phase intercalation, as the primary causes of the observed phase separation. These findings elucidate the microscopic mechanisms underlying the complex superconducting behavior in bilayer nickelate films and underscore that improving oxygen uniformity is crucial for achieving bulk superconductivity with higher zero-resistance temperatures, thereby providing a foundation for subsequent spectroscopic studies.\n3. Co-operating multiorbital and nonlocal correlations in bilayer nickelate Relevance Score: 5.0341 Authors: Evgeny A. Stepanov, Steffen Bötzel, Ilya M. Eremin, Frank Lechermann Link: http://arxiv.org/abs/2604.08221v1 Summary: Based on the effective three-orbital model, this study systematically analyzes the interplay between multiorbital and nonlocal self-energy effects in the normal state of the high-pressure superconducting bilayer nickelate La₃Ni₂O₇ using the D-TRILEX many-body framework beyond dynamical mean-field theory. The results reveal that the low-energy physics is highly dependent on the interorbital interaction strength: when the interaction is weak, the renowned γ quasiparticle flat band lies below the Fermi level; as the interaction strengthens, this flat band crosses the Fermi level, causing electrons to scatter with ferromagnetic paramagnon excitations, thereby forming spin-polaron bound states. These bound states manifest as incoherent spectral weight shadow bands below the Fermi level. The findings unveil the existence of additional competing electronic states in bilayer nickelates, providing a theoretical basis for resolving recent controversies in angle-resolved photoemission spectroscopy experiments regarding spectral structures near the Fermi surface.\n4. Orbital-Selective $d$-wave Superconductivity in the Two-Band $t$-$J$ Model: Possible Applications to La$_3$Ni$_2$O$_7$ Relevance Score: 4.6979 Authors: Zhan Wang, Kun Jiang, Fu-Chun Zhang, Hui-Ke Jin Link: http://arxiv.org/abs/2604.08319v1 Summary: This study employs the variational Monte Carlo method to investigate superconductivity in a two-band t-J model consisting of an itinerant orbital (orbital 0) and a quasi-localized orbital (orbital 1). The key finding is the emergence of a robust orbital-selective d-wave superconducting state, which originates entirely from the itinerant orbital 0. Analysis of the superexchange energy hierarchy reveals that the quasi-localized orbital 1 competes with superconductivity by favoring the formation of local inter-orbital bound states, which act as energy defects that disrupt phase coherence. Consequently, the superconducting order parameter decreases monotonically with increasing occupation of orbital 1. Inspired by superconductivity in the nickelate La₃Ni₂O₇, these results highlight the crucial role of multiorbital physics beyond the single-band t-J framework and identify a concrete pathway for enhancing the superconducting transition temperature: suppressing the involvement of the localized d_{z²} orbital.\n5. Annealing-induced grain coarsening and voltage kinks in superconducting NbRe films Relevance Score: 3.9452 Authors: Zahra Makhdoumi Kakhaki, Anton O. Pokusinskyi, Francesco Avitabile, Abhishek Kumar, Francesco Colangelo, Carla Cirillo, Carmine Attanasio, Oleksandr V. Dobrovolskiy Link: http://arxiv.org/abs/2604.08735v1 Summary: This paper investigates the effects of annealing on grain coarsening, superconductivity, and vortex dynamics in 20-nm-thick non-centrosymmetric superconductor NbRe thin films. After annealing, the average grain size increased from approximately 2 nm to 8 nm. Combined current–voltage (I–V) measurements over a wide range of temperatures and magnetic fields reveal that, unlike the single voltage jump associated with flux flow instability in as-deposited films, the annealed films exhibit multiple voltage kinks in their I–V curves. Supported by time-dependent Ginzburg-Landau numerical simulations, these kinks are attributed to the nucleation and growth of normal domains along grain boundaries. The annealed films form a superconducting network where vortices move along grain boundary channels, while local heating effects and voltage kinks offer potential applications in discrete resistive switching and sensing. The results highlight the critical role of microstructural engineering in modulating vortex dynamics, dissipation, and flux flow instability.\n6. Type-I and Type-II Saddle Points and a Topological Flat Band in a Bi-Pyrochlore Superconductor CsBi2 Relevance Score: 3.8861 Authors: Yusei Morita, Yongkai Li, Yu-Hao Wei, Kosuke Nakayama, Zhiwei Wang, Hua-Yu Li, Takemi Kato, Seigo Souma, Kiyohisa Tanaka, Kenichi Ozawa, Jia-Xin Yin, Takashi Takahashi, Min-Quan Kuang, Yugui Yao, Takafumi Sato Affiliations: Southern University of Science and Technology, Tohoku University, Southwest University, Beijing Institute of Technology, The Graduate University for Advanced Studies (SOKENDAI), Institute for Molecular Science, Quantum Science Center of Guangdong-Hong Kong-Macao Greater Bay Area, High Energy Accelerator Research Organization (KEK) Link: http://arxiv.org/abs/2604.07805v2 Summary: For the Laves phase superconductor CsBi₂ with strong spin-orbit coupling, angle-resolved photoelectron spectroscopy and first-principles calculations reveal that the significantly enhanced electronic density of states originates from the coexistence of two exotic electronic structures: one is a topological flat band with p-orbital character and minimal dispersion locally formed along the U-K high-symmetry line, which contributes a density of states peak near the Fermi level; the other consists of a first-type saddle point at the time-reversal invariant momentum point L and second-type saddle points at non-time-reversal invariant momentum points such as W, U, and K, connected by a flat band, where these saddle points are energetically degenerate and cooperatively produce logarithmically divergent van Hove singularities, further increasing the density of states. Although strong spin-orbit coupling globally broadens the ideal flat band, multi-orbital hybridization instead locally yields a sharper density of states peak. This finding reveals a new mechanism for achieving density of states enhancement in three-dimensional systems with strong spin-orbit coupling, laying the foundation for exploring exotic quantum phases driven by the interplay of high density of states, nontrivial topology, and strong spin-orbit coupling.\n7. Bulk-dissociated topological bands without spin-orbit coupling in hetero-dimensional superconducting metamaterials Relevance Score: 3.7814 Authors: Joseph J. Cuozzo, Sayed Ali Akbar Ghorashi, Dale Huber, Wei Pan, François Léonard Affiliations: University of Pennsylvania, The University of Texas at El Paso, Sandia National Laboratories Link: http://arxiv.org/abs/2604.08675v2 Summary: In this work, the research team theoretically investigated a system where spin-polarized magnetic atoms are decorated on a square superconducting network, in which local Yu-Shiba-Rusinov bound states at the magnetic atom sites collectively form a weak topological superconducting phase in the absence of spin-orbit coupling. By tuning the Fermi energy of the network, the system can transition from a weak topological superconducting phase to a bulk-separated topological superconducting phase, where the edge state band separates from the bulk, giving rise to unexpected features such as nodal lines and coexisting bulk-separated edge states and corner states. This discovery reveals that heterodimensional superconducting metamaterials can serve as an effective template for controlling the coupling and separation of electronic degrees of freedom across different dimensions.\n8. Hubbard vs. Emery model: spectra, transport and relevance for cuprates Relevance Score: 3.6953 Authors: Jakša Vučičević, Rok Žitko Link: http://arxiv.org/abs/2604.08085v1 Summary: This paper systematically compares the performance of the single-orbital Hubbard model and the three-orbital Emery model in describing the spectroscopic and transport properties of cuprate superconductors. The authors obtained model parameters for La2CuO4-based compounds by downfolding from DFT band structures, solved the models using DMFT combined with the NRG method, and computed local spectral functions, DC resistivity, effective mass, etc., while scanning the doping-temperature phase diagram. The results show that the two models are qualitatively similar but quantitatively distinct: the gap in the Hubbard model varies sharply with doping, whereas that in the Emery model remains nearly constant; when the gaps are matched (U≈8t), the resistivity from the Emery model is significantly higher. Comparison with seven experiments on LSCO, LBCO, and LCCO reveals that the Emery model (with conventional U values) agrees well with LSCO and LBCO, while the Hubbard model requires a large coupling constant (U≈12t) to reproduce the experimental resistivity and effective mass. Furthermore, the local spectral weight near the Fermi level is sensitive to U and can be used to constrain the effective coupling from photoemission experiments; the critical doping for the Lifshitz transition also depends on U, and both models can roughly reproduce the experimental values. It is also found that the transport effective mass and the thermodynamic effective mass in theory are not equivalent near the Lifshitz transition, which may affect the extraction of the Planckian dissipation scattering rate. The conclusions indicate that both standard lattice models can quantitatively describe the spectroscopic and transport properties of La2CuO4-based cuprates with appropriate parameter choices, but the U value required by the Hubbard model is significantly larger than expected—a finding that still requires further theoretical understanding and suggests that future momentum-integrated photoemission experiments could precisely determine the effective coupling constant.\n9. Theory-Guided Discovery of Pressure-Induced Transitions in Fast-Ion Conductor BaSnF4 Relevance Score: 3.6603 Authors: Robin Turnbull, Zhang YingLong, Claudio Cazorla, Akun Liang, Rahman Saqib, Miriam Pena-Alvarez, Catalin Popescu, Laura Pampillo, Daniel Errandonea Affiliations: Universitat Politècnica de Catalunya, Universidad de Valencia, CELLS-ALBA Synchrotron Light Facility, CONICET – Universidad de Buenos Aires, University of Edinburgh, Eastern Institute of Technology, University of Chinese Academy of Sciences, Universidad de Buenos Aires Link: http://arxiv.org/abs/2604.08376v1 Summary: This study systematically investigates the structural evolution of the fast-ion conductor BaSnF4 up to 40 GPa by combining density functional theory (DFT) calculations with high-pressure experiments. DFT predicts two pressure-induced phase transitions: the ambient tetragonal P4/nmm phase transforms to a monoclinic P21/m-I structure at 10 GPa, followed by a further transition to a denser monoclinic P21/m-II phase at 32 GPa. The first transition is experimentally confirmed through ambient-temperature angle-dispersive X-ray diffraction, Raman spectroscopy, and electrical resistivity measurements, while the second transition is supported by abrupt changes in Raman modes and resistivity behavior under high pressure, consistent with further crystal structure rearrangement. These results not only establish the high-pressure phase diagram of BaSnF4 but also reveal potential pathways for pressure-modulating ionic transport in fluorostannate-based solid electrolytes.\n10. Machine Learning the order-disorder Jahn-Teller transition in LaMnO$_3$ Relevance Score: 3.6272 Authors: Lorenzo Celiberti, Alexander Ehrentraut, Luca Leoni, Cesare Franchini Link: http://arxiv.org/abs/2604.08058v1 Summary: Using machine learning force fields trained on ab initio data, this study conducted molecular dynamics simulations of the Jahn-Teller structural phase transition in LaMnO₃ at approximately 750 K. Analysis of the distorted site-site correlation functions revealed that the phase transition is driven by the ordering of the Q₂ Jahn-Teller distortion of MnO₆ octahedra, which serves as the order parameter and establishes the order-disorder nature of the transition. The simulations indicated that dynamic local distortions persist above the transition temperature. The results successfully reproduced the experimental temperature dependence of structural parameters and phonon properties, and uncovered anharmonic effects at finite temperatures. This study demonstrates that combining machine learning molecular dynamics with velocity autocorrelation function analysis provides a robust framework for elucidating the microscopic mechanisms of structural phase transitions in correlated materials, particularly enabling clear differentiation of order-disorder phase transitions from other mechanisms such as displacive transitions through the temperature dependence of vibrational properties.\n11. Comparative high-pressure study on rare-earth entropy fluorite-type oxides Relevance Score: 3.6226 Authors: Pablo Botellaa, David Vie, Leda Kolarek, Neha Bura, Peijie Zhang, Anna Herlihy, Dominik Daisenberger, Catalin Popescu, Daniel Errandonea Affiliations: Universitat de Valencia, CELLS-ALBA Synchrotron Light Facility, Diamond Light Source Ltd., University of Zagreb Link: http://arxiv.org/abs/2604.08371v1 Summary: This comparative high-pressure study of two fluorite-type rare earth oxides with increasing configurational entropy, (CePr)O₂-δ and (CePrLa)O₂-δ, employed synchrotron powder X-ray diffraction (up to 30 GPa) and Raman spectroscopy (up to 20 GPa) to analyze their structural and vibrational properties. Both compounds retained the cubic fluorite structure across the entire pressure range, yet anomalies emerged between 9–16 GPa, characterized by a compressibility plateau and changes in vibrational modes, which were attributed to local lattice distortion and gradual bond angle bending rather than a sharp phase transition. In (CePrLa)O₂-δ, the onset of amorphization was observed above 22 GPa, indicating reduced structural stability. After the anomalous regime, the bulk modulus of both systems decreased slightly, suggesting lattice softening. Raman spectroscopy revealed that the intensity of the F₂g mode was suppressed with increasing cation disorder, while the intensity of the RE-O mode increased under compression, implying partial reordering. These results elucidate the complex interplay among configurational entropy, cation size, and pressure in governing the structural stability and vibrational properties of rare earth high-entropy oxides, offering new insights into their ductility and local disorder mechanisms under extreme conditions.\n12. Switching magnetic spin-states using small magnetic fields in compositionally complex Sm(M7)O$_3$ Relevance Score: 3.6104 Authors: R. K. Dokala, M. Geers, P. Nordblad, R. Clulow, R. Mathieu Affiliations: Uppsala University Link: http://arxiv.org/abs/2604.08163v1 Summary: The high-entropy perovskite Sm(M7)O3, with seven equimolar transition metal cations at the B site, was synthesized via solid-state reaction, resulting in extreme chemical disorder. Magnetic measurements reveal long-range antiferromagnetic ordering at approximately 105 K, accompanied by an intrinsic but small and robust excess magnetic moment, manifested as irreversibility between zero-field-cooled and field-cooled magnetization curves, a shift in isothermal hysteresis loops, and discrete remanent magnetization states in DC demagnetization measurements. Notably, a minute cooling field of ±20 Oe suffices to reverse the direction of this excess moment, and the selected magnetic state remains stable under external fields as high as 50 kOe. Anomalies in the remanent magnetization at low temperatures indicate a secondary contribution from the Sm³⁺ sublattice, yet the excess moment primarily originates from uncompensated spins within the B-site antiferromagnetic sublattice. This work demonstrates that high-entropy perovskites provide a unique platform for manipulating uncompensated antiferromagnetic spin states via extremely small magnetic fields.\n13. A metallic CrS$_2$ phase bridging the gap between two- and three-dimensional dichalcogenides Relevance Score: 3.5759 Authors: Hicham Moutaabbid, Dario Taverna, Denis Pelloquin, Lorenzo Paulatto, Alexandre Gloter, Sophie Guéron, Alik Kasumov, Andrea Gauzzi Link: http://arxiv.org/abs/2604.08695v1 Summary: Single-crystal CrS₂ nanorods were synthesized via a high-pressure method, and their structure was resolved using precession electron diffraction tomography, confirming a ladder-like architecture composed of two-dimensional (2D) 1T-type CrS₂ layer fragments typical of dichalcogenides, connected by edge-sharing CrS₆ octahedral chains characteristic of a three-dimensional (3D) marcasite-type structure. First-principles density functional theory calculations indicated the structural stability and revealed strong overlap between the Cr 3d and S 3p states, implying robust covalent Cr–S bonds and metallic behavior. Resistivity measurements on individual nanorods confirmed this metallic nature, with resistivity values of approximately 2–20 mΩ·cm at 4 K. The ladder-like structure creates open channels along the chain direction, potentially facilitating ionic conduction.\n14. Topological multicomponent-pairing superconductivity in twisted bilayer cuprates Relevance Score: 3.5345 Authors: Yu-Hang Li, Congjun Wu, Wang Yang Link: http://arxiv.org/abs/2604.08235v1 Summary: This study focuses on the multicomponent superconducting state in twisted bilayer cuprates, characterized by an order parameter of the form (s + d_1 e^{i\\varphi_1} + d_2 e^{i\\varphi_2}), where (s) is the symmetric combination of the layer-resolved (s)-wave components. By combining Ginzburg-Landau analysis with self-consistent mean-field calculations based on a microscopic model, it is found that the three-component pairing state is topologically nontrivial when (\\varphi_1 - \\varphi_2 \\neq 0, \\pi) and can stabilize over a broad parameter range. The results indicate that even with a significant (s)-wave pairing component, twisted bilayer cuprates can maintain chiral and topological properties, thereby establishing them as a more robust platform for realizing chiral topological superconductivity than previously recognized.\n15. 2D Ferroelectric Ruddlesden-Popper Perovskites: an Emerging Fully Electronically Controllable Shift Current and Persistent Spin Helix Relevance Score: 3.5317 Authors: Yue Zhao, Fu Li, Vikrant Chaudhary, Hongbin Zhang, Gaoyang Gou, Niuzhuang Yang, Yue Hao, Wenyi Liu Affiliations: North University of China, Humboldt-Universität zu Berlin, Technology University of Darmstadt, Xidian University, Xi’an Jiaotong University Link: http://arxiv.org/abs/2604.08360v1 Summary: This study systematically investigates the relationship between structural distortions and functional responses in three Ruddlesden–Popper ferroelectric perovskites with C₂ᵥ symmetry—(4,4-DFPD)₂PbI₄, (DFCHA)₂PbI₄, and PEPI—using first-principles calculations combined with irreducible representation decomposition and wave-vector point group symmetry analysis. The results show that the shift currents generated by the lead-iodine framework are comparable to those of classical ferroelectric oxides, with PEPI reaching a maximum value of 69.16 μA/V², and that the magnitude of the shift current is positively correlated with the octahedral distortion index, though a competition exists between covalent bond strength and structural asymmetry, where an increase in average bond length counteracts the enhancement effect from distortion. In spintronics, C₂ᵥ symmetry protects persistent spin textures, which transform into C₂-protected quasi-persistent spin textures in the monoclinic phase of (4,4-DFHHA)₂PbI₄, thereby forming persistent spin helices capable of supporting long-distance spin transport. The synergistic interplay of ferroelectricity, shift currents, and persistent spin textures enables nonvolatile electrical control of photocurrent direction and spin configuration. This work provides evaluation criteria and practical guidance for designing high-performance integrated spin-photovoltaic devices.\n16. Exploring the conventional and anomalous Josephson effects at arbitrary disorder strength in systems with spin-dependent fields Relevance Score: 3.5305 Authors: Maryam Darvishi, F. Sebastián Bergeret, Stefan Ilić Link: http://arxiv.org/abs/2604.08231v1 Summary: We propose a theory of Josephson current in superconductor–normal metal–superconductor junctions with arbitrary disorder strength and spin-dependent fields such as spin-orbit coupling, Zeeman fields, and altermagnets. Based on the linearized quasiclassical Eilenberger equation, we derive a compact expression for the Josephson current and apply it to various experimentally relevant scenarios. It is found that under Rashba and Dresselhaus spin-orbit coupling, the evolution of the critical current with magnetic field can be used to probe the spin-orbit coupling in the junction; the anomalous Josephson effect (φ0 effect) in Rashba systems remains robust over a wide range of disorder, and in sufficiently long junctions, moderate disorder can even enhance this effect. Furthermore, in altermagnet junctions, disorder rapidly suppresses the 0-π transition. These results are useful for describing experimental setups in high-mobility samples, which always contain some disorder and where neither purely ballistic nor diffusive approximations apply.\n17. Strain continuously rotates the Néel vector in altermagnetic MnTe Relevance Score: 3.2498 Authors: Alex Liebman-Peláez, Jon Kruppe, Resham Babu Regmi, Nirmal J. Ghimire, Yue Sun, Igor I. Mazin, Hilary M. L. Noad, James Analytis, Veronika Sunko, Joseph Orenstein Link: http://arxiv.org/abs/2604.07653v1 Summary: This study utilizes magneto-optical measurement to apply in-situ strain to single-crystal MnTe, revealing that strain primarily influences the Néel vector orientation through continuous rotation rather than the previously assumed domain-twinning mechanism. The orientation of the Néel vector determines the magnetic point group symmetry, so continuous rotation can effectively tune the symmetry and related physical properties, such as switching off the anomalous Hall effect. The results also show that the inherent built-in strain in free-standing crystals is sufficient to pin the Néel vector into a continuous texture at the millimeter scale, and when the strain is large, the Néel vector exhibits hysteretic behavior, suggesting that the magnetic subsystem can undergo a process analogous to plastic deformation. These findings highlight the dominant role of strain in manipulating the Néel vector, provide guidance for using the Néel vector orientation as a tunable degree of freedom in spintronics, and explain the origin of property variations among samples.\n18. Spectral solution of axisymmetric magnetization problems for thin superconducting shells Relevance Score: 3.0780 Authors: Leonid Prigozhin, Vladimir Sokolovsky Affiliations: Ben-Gurion University of the Negev Link: http://arxiv.org/abs/2604.07947v1 Summary: This work proposes an efficient spectral method for the magnetization problem of axisymmetric non-planar superconducting thin films, based on a thin-shell integral current density formulation, employing Chebyshev polynomials for spatial discretization and the method of lines for time integration. The method is applicable to both open and closed axisymmetric shells, and its high accuracy enables the obtained solutions to serve as benchmarks for general (non-axisymmetric) thin-shell magnetization problems. The study demonstrates that the method can automatically detect the transition of the superconducting shell from an ideal Meissner state to a mixed state as the external field varies, and this capability is validated through the example of magnetic shielding by a superconducting spherical shell. Compared to traditional finite element methods, the spectral method exhibits exponential convergence for smooth problems and directly yields high-precision surface current density and electric field, avoiding errors introduced by numerical differentiation, thus providing a reliable tool for modeling superconducting thin films with complex geometries.\n19. Odd-parity Magnetism from the Generalized Bloch Theorem Relevance Score: 3.0126 Authors: Mikkel Christian Larsen, Thomas Olsen Link: http://arxiv.org/abs/2604.08233v1 Summary: This paper proposes using the generalized Bloch theorem to handle odd-parity magnetism in helical magnets, allowing the system to be described within the primitive unit cell while all relevant properties are obtained through downfolding in reciprocal space. First-principles calculations on MnI₂, NiI₂, and MnTe₂ as examples verify that the magnitude of spin splitting strongly depends on the orbital composition of the bands, with states exhibiting large odd-parity (p-type) characteristics showing the largest spin splitting. This method can be extended to the calculation of response functions for helical magnets, requiring only the primitive unit cell, thereby greatly facilitating theoretical progress in this field.\n","permalink":"https://nickelates.uk/en/posts/2026-04-09-arxiv-daily/","summary":"\u003cblockquote\u003e\n\u003cp\u003e\u003cstrong\u003eDaily Overview\u003c/strong\u003e:\nToday\u0026rsquo;s highlights focus on the electronic structure, superconducting mechanism, and material properties of bilayer Ruddlesden-Popper nickelate superconductors. In [1], the three-dimensional band structure of (La,Pr,Sm)₃Ni₂O₇ thin films was resolved using low-temperature ARPES, revealing orbital-dependent dimensionality and a superconducting gap driven by the dz² orbital (2Δ/kBTc~8), emphasizing the critical role of the third dimension. [2] attributed the two-step superconducting transition in La₂PrNi₂O₇₋δ thin films to granular superconductivity through transport and structural characterization, pointing to oxygen inhomogeneity as the primary factor limiting zero-resistance temperature. [3] used D-TRILEX many-body theory to find that competition between multiorbital and nonlocal correlations in the normal state of bilayer nickelates can form spin-polaron bound states, providing a new explanation for the controversy over ARPES spectral features. [4] employed variational Monte Carlo methods to obtain an orbital-selective d-wave superconducting state in a two-band t-J model, indicating that the quasi-localized dₓ²⁻y² orbital competes with superconductivity, and suppressing its participation may enhance Tc. These works deepen the understanding of nickelate superconductivity from both experimental and theoretical perspectives.\n\u003cstrong\u003earXiv submission processing window\u003c/strong\u003e: 2026-04-08 23:37 to 2026-04-09 19:57 UTC.\u003c/p\u003e","title":"arXiv Daily: nickelate superconductors 2026-04-09"},{"content":" Daily Overview: Today\u0026rsquo;s highlight work focuses on an in-depth understanding of the electronic structure of mixed Ruddlesden-Popper nickelates. In [1], a study based on cluster dynamical quantum Monte Carlo method reveals how a vertical electric field significantly modulates the superconducting pairing symmetry of the bilayer nickelate La₃Ni₂O₇: the electric field induces a transition from s±-wave to d-wave pairing symmetry by suppressing the s±-wave pairing derived from the d_{z²} orbitals, driving interlayer d_{z²} orbital mismatch, and promoting electron transfer to the d_{x²-y²} orbitals. The d-wave pairing strength exhibits a distinctive dome-shaped behavior as a function of the electric field. This large-scale many-body calculation provides a key microscopic picture for understanding the superconducting mechanism of RP nickelates and points to a new direction for manipulating nickel-based superconducting pairing states via electric fields. arXiv submission processing window: 2026-04-07 20:49 to 2026-04-08 18:48 UTC.\n1. Perpendicular electric field induced $s^\\pm$-wave to $d$-wave superconducting transition in thin film La$_3$Ni$_2$O$_7$ Relevance Score: 5.4135 Authors: Yongping Wei, Xun Liu, Fan Yang, Mi Jiang Link: http://arxiv.org/abs/2604.07185v1 Summary: Inspired by the vertically electric-field-tunable superconducting properties of Ruddlesden–Popper bilayer nickelate La₃Ni₂O₇, this study employs the dynamic cluster quantum Monte Carlo method to solve the imbalanced two-orbital bilayer Hubbard model. By analyzing the electric-field-induced pairing symmetry and its evolution under undoped, hole-doped, and electron-doped conditions, we find that the s±-wave pairing originating from the d_{z²} orbital is suppressed, while the interlayer mismatch of the d_{z²} orbital and the transfer of electrons to the d_{x²-y²} orbital drive a pairing symmetry transition from s±-wave to d-wave. Interestingly, the d-wave pairing arising from the d_{x²-y²} orbital exhibits a dome-shaped behavior as a function of electric field strength. The large-scale many-body calculations are consistent with the predictions of weak-coupling methods, providing new insights into the superconducting mechanism of RP nickelates.\n2. Influence of the Ortho-II superstructure in the YBa$_2$Cu$_3$O$_{7-δ}$ Orthorhombic phase after annealing Relevance Score: 4.1697 Authors: Roberto F. Luccas, Lorenzo Gallo, Cesar E. Sobrero, Jorge A. Malarría Affiliations: Universidad Nacional de Rosario, CONICET-UNR Link: http://arxiv.org/abs/2604.07060v1 Summary: This study conducted isothermal oxidation experiments on YBa₂Cu₃O₇-δ (YBCO) powder starting from a fully oxygen-deficient state (δ=1) and processed in an oxygen atmosphere within the temperature range of 300–800°C until saturation, utilizing thermogravimetric analysis and differential thermal analysis to monitor the tetragonal-to-orthorhombic (T-O) phase transition. Oxidized samples were obtained under two conditions: direct T-O transition into the Ortho-I superstructure, or passing through the Ortho-II superstructure region. X-ray diffraction analysis revealed differences in the orthorhombic diffraction patterns between the two conditions: at low oxidation temperatures (\u0026lt;400°C), the T-O transition traversed the phase diagram region where the Ortho-II superstructure exists, resulting in the retention of a tetragonal characteristic peak (around 47°) in the final orthorhombic phase, whereas high-temperature oxidation led to a complete transformation into orthorhombic double peaks. The study proposes that low-temperature oxidation through the Ortho-II superstructure leaves a persistent oxygen ordering fingerprint in the material, which can be detected by conventional X-ray diffraction even at high oxygen content (δ≈0) within the stable Ortho-I region. This mechanism explains the differences in diffraction patterns at varying oxidation temperatures and suggests that the final ordered configuration of oxygen atoms in YBCO can be regulated by controlling the oxidation path, offering a new approach for designing superconducting materials with tunable anisotropy and electronic properties.\n3. Directional Andreev-Reflection Signatures of Inter-Orbital Pairing in Sr$_2$RuO$_4$ Relevance Score: 4.1041 Authors: G. Csire, Y. Fukaya, M. Cuoco, Y. Tanaka, R. K. Kremer, A. S. Gibbs, G. A. Ummarino, D. Daghero, R. S. Gonnelli Link: http://arxiv.org/abs/2604.06706v1 Summary: This study investigates the quasi-two-dimensional unconventional superconductor Sr₂RuO₄ using directional point-contact Andreev reflection spectroscopy (PCARS), revealing a directional anisotropy contrary to conventional expectations: pronounced in-gap Andreev bound states (ABS) appear on surfaces perpendicular to the interlayer direction (c-axis), while the spectral features at in-plane edges are suppressed. First-principles Dirac-Bogoliubov-de Gennes calculations combined with a three-orbital tight-binding model analysis, along with Ag overlayer interface reconstruction simulations, indicate that this anomalous anisotropy originates from the interorbital nature of the superconducting pairing—irrespective of whether the interorbital pairing channels are even-parity or odd-parity, they naturally yield robust ABS on the c-axis surface while suppressing in-plane edge modes and potentially leading to horizontal line nodes. The theoretical results are in excellent agreement with experimental observations, highlighting the crucial role of interorbital correlations in shaping the spectral response and providing important constraints on the symmetry determination of the superconducting order parameter in Sr₂RuO₄.\n4. Nonlinear phononics in LaFeAsO: Optical control of the crystal structure toward possible enhancement of superconductivity Relevance Score: 4.0293 Authors: Shu Kamiyama, Tatsuya Kaneko, Kazuhiko Kuroki, Masayuki Ochi Affiliations: The University of Osaka Link: http://arxiv.org/abs/2604.06745v1 Summary: This study utilizes a nonlinear phononics approach to attempt to modulate the crystal structure of the iron-based superconductor LaFeAsO via photoinduced phonon excitation, aiming to enhance its superconducting transition temperature. Based on first-principles calculations, the researchers constructed an anharmonic lattice potential and simulated phonon dynamics under the excitation of different infrared-active phonon modes. The results reveal that when a specific infrared-active phonon mode is selectively excited, the key structural parameter—the anion height ( h )—approaches the ideal value (i.e., that in SmFeAsO). This effect originates from an ionic Raman scattering process driven by anharmonic coupling between infrared and Raman phonons. These findings suggest that selective excitation of infrared phonons via nonlinear phononics holds promise for optically controlling the crystal structure in iron-based superconductors, potentially enhancing their superconductivity.\n5. Microscopic evidence of spin-driven multiferroicity and topological spin textures in monolayer NiI2 Relevance Score: 3.9339 Authors: Haitao Wang, Tianxing Jiang, Weiyi Pan, Xu Wang, Hongyu Wang, Junchao Tian, Lianchuang Li, Dongming Zhao, Qingle Zhang, Chenxi Wang, Ying Yang, Hongjun Xiang, Changsong Xu, Donglai Feng, Tong Zhang Affiliations: Fudan University, Tsinghua University, Collaborative Innovation Center for Advanced Microstructures, Shanghai Research Center for Quantum Sciences, Hefei National Laboratory Link: http://arxiv.org/abs/2604.06959v1 Summary: Using vector spin-polarized scanning tunneling microscopy, this study reveals microscopic evidence of spin-driven multiferroicity at the atomic scale in monolayer NiI₂. A canted spin spiral state with a defined spin rotation plane was experimentally observed, accompanied by a 2Q charge modulation. Topological spin textures composed of meron/antimeron pairs were identified at spin spiral domain walls, which are associated with local charge extrema and band shifts, indicating that bound charges are induced by changes in ferroelectric polarization at the domain walls. The experimental results are successfully described by a realistic spin model incorporating Kitaev interactions and the generalized spin-current model for type-II multiferroicity. This work provides direct microscopic evidence for spin-driven multiferroicity in an extreme two-dimensional system and establishes a platform for achieving low-dissipation electric-field control of topological spin textures.\n6. Quantum Tunnelling and Room-Temperature Superconductivity of Hydride from Size Effects Relevance Score: 3.8669 Authors: Xiaozhi Hu Affiliations: University of Western Australia Link: http://arxiv.org/abs/2604.16460v1 Summary: This paper proposes that the superconductivity of micron-scale hydride samples between metal tips under extreme pressure be regarded as a macroscopic quantum tunneling phenomenon, where the energy barrier height of the hydride is modulated by pressure, and emphasizes the need to minimize the barrier width between metal tips to suppress the exponential decay of electron tunneling. Additionally, the sample thickness effect is significant: thinner hydrides (approximately 1 micron) are conducive to achieving higher superconducting temperatures. The core mechanism involves the deformation of hydrogen atoms under extreme compression, inducing electron redistribution and forming “low electron density” superconducting channels within the lattice, thereby facilitating the collisionless flow of Cooper pairs. Based on this model, an approximately linear relationship between the superconducting transition temperature Tc and pressure P is derived, and it is found that the sample thickness effect can further enhance Tc by about 15%, sufficient to elevate the currently experimentally confirmed 250–260 K range to room temperature. The conclusion indicates that simultaneously reducing the barrier width and sample thickness is the key size optimization strategy for achieving room-temperature superconductivity.\n7. d-Wave pair density wave superconductivity in a two-orbital model Relevance Score: 3.7453 Authors: Samuel Vadnais, Arun Paramekanti Link: http://arxiv.org/abs/2604.07511v2 Summary: Using a two-orbital model representing (p_x, p_y) or (d_{xz}, d_{yz}) orbitals on a square lattice, this study explores superconductivity in multiorbital systems. Through random phase approximation analysis of minimal interorbital t-J or t-V interactions in the weak-coupling regime, an incommensurate d_{xy} pairing density wave (d-PDW) superconducting instability driven by interband pairing is identified, along with its competition with the uniform nodal d_{xy} pairing state and magnetic and charge density wave (CDW) instabilities. In the strong-coupling regime, an effective hard-core Cooper pair Hamiltonian is derived, and using a bosonic Gutzwiller variational method, a period-2 PDW is revealed across a wide filling range, with a checkerboard CDW at quarter filling. These results indicate that orbital content and multiband Fermi surfaces play a crucial role in stabilizing interband PDW states, and the findings are relevant to correlated multiorbital materials with quasi-one-dimensional bands, the Hubbard model on a square-octagon lattice, and p-orbital atomic Fermi systems.\n8. Observation of the Ferromagnetic Kondo Effect Relevance Score: 3.6453 Authors: Elia Turco, Nils Krane, Hongyan Chen, Simon Gerber, Wulf Wulfhekel, Roman Fasel, Pascal Ruffieux, David Jacob Affiliations: Empa – Swiss Federal Laboratories for Materials Science and Technology, Delft University of Technology, Universidad de Alicante Link: http://arxiv.org/abs/2604.07174v1 Summary: This study simultaneously observed the ferromagnetic Kondo effect and the overscreened Kondo effect in a single-molecule spin system—a spin-1 and spin-1/2 triangulene dimer adsorbed on a gold surface. Using low-temperature scanning tunneling spectroscopy, a zero-bias dip feature was observed in the 2T unit, and a zero-bias Kondo peak was observed in the 3T unit, both typical signatures of non-Fermi liquid behavior. Many-body theoretical calculations perfectly match the experimental spectra and reveal that the microscopic mechanism is a three-channel Kondo model arising from the Clebsch–Gordan structure of the molecular ground-state wavefunction, where the 2T channel is ferromagnetically coupled and the 3T channel is antiferromagnetically coupled. Scaling analysis indicates that ferromagnetic and overscreened Kondo effects coexist in the same system. These results not only provide the first experimental verification of the long-unobserved ferromagnetic Kondo effect but also demonstrate that non-Fermi liquid physics can be precisely tuned through nanographene molecular design, offering a new strategy for atomic-scale quantum engineering.\n9. Alterelectricity: Electrical Analogue of Altermagnetism Relevance Score: 3.6078 Authors: Shibo Fang, Jianhua Wang, Zhenzhou Guo, Jialin Gong, Haiyu Meng, Wenhong Wang, Zhenxiang Cheng, Xiaotian Wang, Yee Sin Ang Link: http://arxiv.org/abs/2604.07112v1 Summary: This paper proposes the concept of “alterelectricity,” the electrical analogue of altermagnetism, describing a pair of states that can be switched between via a physical operation and feature alternating anisotropic band structures. This alterelectric state originates from switchable sublattice-selective structural changes connecting two configurations linked by non-inversion symmetry. Using an anisotropic Lieb lattice model, a symmetry framework for identifying alterelectricity is established, and first-principles calculations reveal two material realizations: interlayer sliding in bilayers, exemplified by tetragonal Ag₂N and hexagonal FeHfI₆, and a ferroelectrically switchable Ti-adsorbed SnP₂S₆ monolayer. Based on the switchable anisotropy of the alterelectric Fermi surface, an alterelectric tunnel junction (AETJ) is proposed, achieving a tunneling electroresistance effect of up to 120% through differences in Fermi surface matching between parallel and antiparallel configurations. This work establishes the foundational concept of alterelectricity and expands the material library of ferroic electronics.\n10. $\\mathbb Z_{2q}$ parafermionic hinge states in a three-dimensional array of coupled nanowires Relevance Score: 3.5818 Authors: Sarthak Girdhar, Viktoriia Pinchenkova, Even Thingstad, Jelena Klinovaja Link: http://arxiv.org/abs/2604.07313v1 Summary: This paper constructs a three-dimensional helical second-order topological superconductor model consisting of weakly coupled Rashba nanowire arrays. Through perturbation theory, bosonization techniques, and numerical diagonalization analysis, it is found that within a specific parameter region, both the bulk states and surface energy spectra of the system exhibit energy gaps, yet a pair of gapless helical (Z_{2q}) parafermionic modes (with (q) odd) still exist along the closed path of one-dimensional hinges. The precise trajectories of these hinge modes are determined by the hierarchy of inter-wire couplings and the termination of the sample boundaries. In the non-interacting limit (q=1), the system supports gapless Majorana hinge modes. Unlike known higher-order topological superconductors that rely on specific spatial symmetries, the parafermionic states in this model are protected solely by particle-hole symmetry and reside on the hinges of a uniform three-dimensional system, rather than at heterojunction interfaces or the ends of one-dimensional nanowires. This study reveals how strong electron-electron interactions evolve Majorana modes into more exotic parafermionic modes, providing an analytically tractable microscopic model for understanding correlated higher-order topological superconducting phases.\n11. Superradiance enhances and suppresses fermionic pairing based on universal critical scaling in two order parameters systems Relevance Score: 3.5389 Authors: Yilun Xu Affiliations: Beijing Academy of Quantum Information Sciences, Peking University Link: http://arxiv.org/abs/2604.07407v2 Summary: Based on Landau\u0026rsquo;s continuous phase transition theory, this paper proposes a universal physical quantity to determine how the phase transition of one order parameter affects the rate of change of another in a two-order-parameter system. By deriving the critical scaling rate under free energy minimization, it is found that the sign of the cross-coupling term determines whether the second order parameter is enhanced or suppressed after the phase transition. Taking the two-mode Rabi model and the one-dimensional attractive interacting Fermi-Dicke model as examples, numerical verification confirms the theoretical predictions: in the two-mode Rabi model, the superradiant phase transition can either enhance or suppress the pairing strength between two spins, depending on the strength of the Kerr effect; in the one-dimensional Fermi-Dicke model, the continuous superradiant phase transition always suppresses the superconducting gap. This work provides a new paradigm for indirectly enhancing or suppressing target physical effects (such as fermion pairing) by manipulating the phase transition of another order parameter, and offers a simple critical analysis tool for studying complex systems with multiple order parameters and quantum simulations.\n12. Magnetic-field switching of exciton-magnon coupling in LiNiPO$_4$ Relevance Score: 3.5295 Authors: Bei Sun, Zhuo Yang, Julian Shibuya, Koichi Kindo, Kenta Kimura, Atsuhiko Miyata Link: http://arxiv.org/abs/2604.06785v1 Summary: This study systematically measured the exciton-magnon coupling as a function of temperature and magnetic field in the magnetoelectric antiferromagnet LiNiPO₄ using pulsed magnetic fields up to 50 Tesla. The experimental results revealed sharp on/off switching behavior of the magnon sideband intensity at the magnetic phase boundaries induced by the field: in the plateau phases (I and V), the sideband intensity was strongly suppressed, exhibiting thermally activated characteristics due to a finite magnon gap; while in the canted spin states (IV and VII), the sideband intensity was significantly enhanced as the strong canting of spins increased the optical transition matrix element. This selective switching effect originates from the competition between thermal magnon population and spin-dependent transition matrix elements. The findings demonstrate that manipulating spin degrees of freedom via magnetic fields can effectively turn on or off the exciton-magnon optical transitions in antiferromagnets, offering a new avenue for controlling light-matter interactions.\n13. Proximate quantum spin liquid state in the frustrated HoInCu$_4$ metal Relevance Score: 3.5184 Authors: I. Ishant, T. Shiroka, O. Stockert, V. Fritsch, M. Majumder Link: http://arxiv.org/abs/2604.06867v1 Summary: A comparative muon spin relaxation and rotation (μSR) study of two fcc lattice metal compounds, HoCdCu4 and HoInCu4, reveals the critical role of magnetic frustration in stabilizing their magnetic ground states. The μSR results show that in HoCdCu4, all Ho magnetic moments participate in static long-range magnetic order below the Néel temperature (~8 K), whereas HoInCu4 exhibits strong magnetic frustration: only about 30% of the Ho moments form static magnetic order below approximately 0.76 K, while the remaining 70% display dynamic correlations and maintain persistent spin dynamics down to 0.3 K, behaving similarly to a quantum spin liquid (QSL). Furthermore, the temperature dependence of the relaxation rate in the paramagnetic state of HoInCu4 reveals quantum critical fluctuations near the Néel temperature, indicating its proximity to a quantum critical point. Combining these observations, the ground state of HoInCu4 is identified as a \u0026ldquo;proximate quantum spin liquid\u0026rdquo; (PQSL) state, which is reported for the first time in a frustrated metallic system. Inelastic neutron scattering results further support this conclusion, resembling those of insulating PQSL candidates, thereby confirming the unique ground state of HoInCu4 with coexisting dynamic and static magnetism.\n14. In-situ Observation of Magnetostriction Crossover in a Strongly Dipolar Two-Dimensional Bose Gas Relevance Score: 3.3878 Authors: Yifei He, Xin-Yuan Gao, Haoting Zhen, Mithilesh K. Parit, Yangqian Yan, Gyu-Boong Jo Link: http://arxiv.org/abs/2604.07194v1 Summary: By in-situ imaging of a quasi-two-dimensional ¹⁶⁶Er gas, this study observes the crossover of magnetostriction from a strongly anisotropic superfluid phase to a nearly isotropic normal phase in a strongly dipolar Bose gas. A quasi-two-dimensional Hartree-Fock-mean-field theoretical framework is developed, which serves as a reliable interaction-aware thermometry tool, allowing simultaneous determination of temperature and chemical potential for all dipole orientations from a single fit. The research demonstrates that the low-density wing region effectively obeys the local density approximation equation of state, validating the feasibility of extracting thermodynamic quantities via the local density approximation in strongly dipolar systems. Furthermore, a smooth crossover from an isotropic thermal wing to an anisotropic coherent core is revealed in a single in-situ image, providing a new avenue for future precise studies of two-dimensional strongly dipolar superfluidity and thermodynamics.\n15. Laterally Differentiated Polymorphs: a route to multifunctional nanostructures Relevance Score: 3.3446 Authors: Pete E. Lauer, Kensuke Hayashi, Yuichiro Kunai, Ondřej Wojewoda, Jan Klíma, Ekaterina Pribytova, Michal Urbánek, Aubrey Penn, Takayuki Kikuchi, Renzhi Ma, Takayoshi Sasaki, Takaaki Taniguchi, Caroline A. Ross Affiliations: National Institute for Materials Science (NIMS), Nagoya University, Fujikura Limited, Brno University of Technology, Massachusetts Institute of Technology Link: http://arxiv.org/abs/2604.07495v1 Summary: This study proposes a method termed \u0026ldquo;lateral differentiation polymorphism\u0026rdquo; (LDP), which involves pre-patterning perovskite seed layers (e.g., strontium titanate or lanthanum strontium manganite) on garnet substrates, followed by the deposition of a thin film with the same stoichiometry (e.g., Y₃Fe₅O₁₂), successfully yielding composite nanostructures with identical composition but distinct structures—garnet and perovskite. The two polymorphic phases are epitaxially grown on the garnet substrate and the perovskite seed layer, respectively, forming a lateral pattern with vertical interfaces and dimensions exceeding 50 nanometers. Experiments demonstrate that this method is applicable across the entire compositional range from garnet to perovskite (Y:Fe ratio from 1:1 to 3:5), with both phases achieving a growth thickness of up to 2 micrometers. More importantly, in LDP structures containing bismuth compositions (e.g., Bi₂.₂₅Y₀.₇₅Fe₅O₁₂ and Bi₃Fe₅O₁₂), applying an electric field to the perovskite phase significantly modulates the magnon dispersion and magneto-optical hysteresis loop of the garnet phase, realizing magnetoelectric coupling. This strategy overcomes the traditional bottleneck of integrating garnet into magnetoelectric nanocomposites, offering a new pathway for voltage-controlled spintronic, magnonic, and photonic devices.\n16. Topochemically-engineered coexistence of charge and spin orders in intercalated endotaxial heterostructures Relevance Score: 3.2969 Authors: Samra Husremović, Wanlin Zhang, Medha Dandu, Berit H. Goodge, Isaac M. Craig, Ellis Kennedy, Matthew P. Erodici, Karen C. Bustillo, Chengyu Song, Jim Ciston, Sinéad Griffin, Archana Raja, D. Kwabena Bediako Link: http://arxiv.org/abs/2604.06453v1 Summary: This study synthesizes a metastable two-dimensional crystal, T/H-FeₓTaS₂, via a topochemical method, which is an intergrown polytype heterostructure composed of 1T-TaS₂ and H-TaS₂ with Fe atoms intercalated at the van der Waals interfaces. Under mild annealing at 250°C, treatment of 1T-TaS₂ flakes with Fe precursors induces partial conversion of layers into H-TaS₂ while Fe intercalates between layers, forming a mixed-polytype framework that cannot be obtained by conventional high-temperature solid-state synthesis. In this heterostructure, Fe intercalation provides local spins for ferromagnetism, while the 1T-TaS₂ layers retain a commensurate charge density wave (C-CDW) up to room temperature, with both coexisting successfully. The Fe content simultaneously tunes spin and charge orders, and the C-CDW phase remains stable after intercalation, attributed to the enhancement effect of the polytype heterostructure on the CDW. This work demonstrates that metastable intercalated intergrowth heterostructures are an effective approach to stabilize and control competing quantum phases in two-dimensional materials.\n17. Atomic-Scale Detection of Néel Vector Switching in the Single-Layer A-type Antiferromagnet Cr2S3-2D Relevance Score: 3.2933 Authors: Affan Safeer, Calisa Dias, Mahdi Ghorbani-Asl, Abdallah Karaka, Pradyumna Bawankule, Weibin Li, Pierluigi Gargiani, Wouter Jolie, Arkady V. Krasheninnikov, Amilcar Bedoya-Pinto, Thomas Michely, Jeison Fischer Link: http://arxiv.org/abs/2604.07245v1 Summary: By combining spin-polarized scanning tunneling microscopy and X-ray magnetic circular dichroism measurements, this study confirms that monolayer Cr₂S₃-2D grown on graphene/Ir(110) substrates is the first single-layer A-type antiferromagnet. Spin-polarized scanning tunneling microscopy reveals hysteresis loops with large switching fields that depend significantly on island size; X-ray magnetic circular dichroism detects a small signal at the Cr L₂,₃ edges with a linear magnetic field dependence, indicating a nearly compensated antiferromagnetic ground state with a Néel temperature of approximately 160 K. Quantitative analysis of the switching field versus island size dependence, combined with first-principles calculations, reveals that substrate support induces a slight imbalance in the magnetic moments of the two chromium planes in Cr₂S₃-2D, generating a net magnetization that enables 180° rotation of the Néel vector. Furthermore, the material retains its magnetic properties after several days of exposure to air. This achievement represents a critical step toward functional two-dimensional spintronics.\n18. K$_2$Co$_2$(TeO$_{3}$)$_{3}$ $\\cdot$ 2.5 H$_2$O : A mineral-inspired pseudo-honeycomb cobalt dimer antiferromagnet Relevance Score: 3.2695 Authors: Austin M. Ferrenti, Maxime A. Siegler, Yiqing Hao, Chris Lygouras, Tong Chen, Tiffany A. Soetojo, Megan R. Rutherford, Kenji M. Kojima, Huibo Cao, Natalia Drichko, Alannah M. Hallas, Tyrel M. McQueen Link: http://arxiv.org/abs/2604.07376v1 Summary: This paper reports the synthesis and magnetic characterization of a novel zemannite-like antiferromagnet, K₂Co₂(TeO₃)₃·2.5H₂O (KCoTOH). The material was grown via a hydrothermal method, and its structure exhibits combined features of triangular dimers and honeycomb-like motifs, forming an origami honeycomb arrangement of cobalt ions constructed from [Co₂O₉] dimers. Bulk magnetic susceptibility and specific heat measurements indicate the onset of long-range antiferromagnetic order at TN = 7.6(1) K. Neutron diffraction and muon spin relaxation (μSR) experiments reveal that the majority of ordered magnetic moments lie within the pseudohoneycomb planes. Three distinct characteristic oscillation frequencies were resolved in the zero-field μSR spectra, indicating extremely low structural disorder in the as-grown crystals. In contrast to typical systems where inter-dimer interactions are negligible or ferromagnetic, KCoTOH stabilizes its planar ordered configuration primarily through net antiferromagnetic interactions mediated by bridging tellurite groups. This work highlights the potential of hydrothermal synthesis in stabilizing magnetic materials with novel and potentially higher geometric frustration.\n19. Magnetic order and excitations in the magnetically intercalated van der Waals material Cr$_{\\frac{1}{4}}$NbSe$_2$ Relevance Score: 3.2557 Authors: Ryota Yamaoka, Hiraku Saito, Yuki Settai, Xiang Huang, Daisuke Nishio-Hamane, Shingo Takahashi, Daichi Ueta, Tatsuro Oda, Hodaka Kikuchi, Tao Hong, Masaki Nakano, Shinichiro Seki, Taro Nakajima Link: http://arxiv.org/abs/2604.07117v1 Summary: Through non-polarized and polarized neutron scattering experiments, this study reveals that the magnetic ground state of the intercalated van der Waals material Cr₁/₄NbSe₂ is a 120° antiferromagnetic order with a magnetic propagation wave vector of q = (1/3, 1/3, 0). Using inelastic neutron scattering measurements on co-aligned single crystals, the dispersion relation of magnetic excitations was determined at low temperatures. Combined with linear spin wave theory calculations, it was found that the out-of-plane ferromagnetic interaction is significantly stronger than the in-plane nearest-neighbor antiferromagnetic interaction. Although the crystal structure consists of two-dimensional van der Waals layers, the magnetic order exhibits three-dimensional characteristics, which can be attributed to long-range magnetic interactions mediated by conduction electrons. These results provide quantitative evidence for understanding the three-dimensional nature of magnetic order in intercalated transition metal dichalcogenides.\n20. Volume Collapse Without a Structural Transition in Shock-Compressed FeO Relevance Score: 3.2547 Authors: C. Crépisson, T. Stevens, M. Fitzgerald, C. Camarda, P. G. Heighway, D. Peake, D. McGonegle, A. Descamps, A. Amouretti, D. A. Chin, K. K. Alaa El-Din, S. Azadi, E. Brambrink, K. Buakor, L. Pennacchioni, M. Sieber, A. Coutinho Dutra, J. Hernandez Gordillo, K. Yamamoto, J. -A. Hernandez, R. Torchio, T. Tschentscher, Y. Wang, H. Taylor, J. Pintor, O. S. Humphries, M. Andrzejewski, C. Baehtz, E. Barraud, A. B. Belonoshko, D. S. Bespalov, E. Boulard, R. Briggs, D. Cabaret, O. Castelnau, A. Chakraborti, J. Chantel, D. M. Cheshire, G. Collins, T. E. Cowan, Y. J. Deng, S. Di Dio Cafiso, L. Dresselhaus-Marais, X. Fang, A. Forte, S. Galitskiy, E. Galtier, T. Gawne, H. Ginestet, F. Hanby, A. Hari, N. J. Hartley, H. Höppner, N. Jaisle, J. Kim, Z. Konôpková, A. Krygier, J. Kuhlke, C. M. Lonsdale, S-N. Luo, J. Lütgert, M. Masruri, E. E. McBride, J. D. McHardy, M. I. McMahon, R. S. McWilliams, S. Merkel, T. Michelat, J-P. Naedler, B. Nagler, M. Nakatsutsumi, A-M. Norton, I. K. Ocampo, I. I. Oleynik, C. Otzen, N. Ozaki, C. A. J. Palmer, S. E. Parsons, A. Pelka, A. Phelipeau, C. Prescher, N. Pulver, C. Prestwood, C. Qu, D. Ranjan, R. Redmer, C. Sahle, A. A. Sanjuan Mora, S. Schumacher, J-P. Schwinkendorf, N. Sévelin-Radiguet, G. Shoulga, R. F. Smith, S. Singh, C. N. Somarathna, M. Stevenson, C. V. Storm, C. Strohm, T-A. Suer, M. X. Tang, A. Tipeev, M. Toncian, T. Toncian, U. Trdan, J. D. Tunacao, J. D. Umpleby-Thorp, L. Wang, M. Wilke, U. Zastrau, G. Gregori, D. Polsin, C. Sternemann, J. S. Wark, T. M. Hutchinson, C. McGuire, S. Pandolfi, A. Sollier, A. Higginbotham, T. R. Preston, D. Kraus, J. H. Eggert, K. Appel, M. Harmand, S. M. Vinko Link: http://arxiv.org/abs/2604.06768v1 Summary: This study employed X-ray diffraction and emission spectroscopy to characterize the behavior of FeO under laser-driven shock compression across a pressure range of 31-199 GPa. Experimental results revealed that FeO retains the B1 (rocksalt) structure along the shock adiabat up to the melting boundary at 191 GPa. Although the phase state and volume changes generally align with static compression data, an anomalous volume collapse of 7-10% was observed at approximately 60 GPa, a phenomenon absent in static experiments. Direct detection of the low-spin state via X-ray emission spectroscopy at 180 GPa confirmed that this volume collapse originates from an isostructural spin-state transition in FeO, from a high-spin insulating state to a low-spin metallic state. This finding demonstrates that electronic phase transitions in FeO under dynamic compression can induce significant volume reduction without necessitating a structural phase transition, offering crucial insights into the physical properties of iron-bearing minerals in the lower mantle and at the core-mantle boundary.\n","permalink":"https://nickelates.uk/en/posts/2026-04-08-arxiv-daily/","summary":"\u003cblockquote\u003e\n\u003cp\u003e\u003cstrong\u003eDaily Overview\u003c/strong\u003e:\nToday\u0026rsquo;s highlight work focuses on an in-depth understanding of the electronic structure of mixed Ruddlesden-Popper nickelates. In [1], a study based on cluster dynamical quantum Monte Carlo method reveals how a vertical electric field significantly modulates the superconducting pairing symmetry of the bilayer nickelate La₃Ni₂O₇: the electric field induces a transition from s±-wave to d-wave pairing symmetry by suppressing the s±-wave pairing derived from the d_{z²} orbitals, driving interlayer d_{z²} orbital mismatch, and promoting electron transfer to the d_{x²-y²} orbitals. The d-wave pairing strength exhibits a distinctive dome-shaped behavior as a function of the electric field. This large-scale many-body calculation provides a key microscopic picture for understanding the superconducting mechanism of RP nickelates and points to a new direction for manipulating nickel-based superconducting pairing states via electric fields.\n\u003cstrong\u003earXiv submission processing window\u003c/strong\u003e: 2026-04-07 20:49 to 2026-04-08 18:48 UTC.\u003c/p\u003e","title":"arXiv Daily: nickelate superconductors 2026-04-08"},{"content":" Daily Overview: The highlight of today\u0026rsquo;s work focuses on an in-depth understanding of the electronic structure of mixed Ruddlesden-Popper nickelates. In [1], a study based on DFT+singular mode functional renormalization group method reveals the critical role of interlayer Ni-Ni distance in governing the ground-state phase diagram of La3Ni2O7/LaAlO3 thin films: a shorter interlayer distance tends to form C-type spin density wave (with ferromagnetic interlayer coupling), a longer interlayer distance leads to G-type spin density wave (with antiferromagnetic interlayer coupling), while the intermediate region stabilizes an s±-wave superconducting state dominated by Ni 3d₃z²⁻ʳ² orbital pairing. This theoretical picture successfully explains the experimental observation of superconductivity in thin films under ambient pressure and predicts that applying pressure will suppress the superconducting transition temperature, ultimately entering a C-type spin density wave. If experimentally verified, this prediction would strongly reveal the itinerant electron nature of electronic correlations in this system, as the C-type spin density wave naturally emerges in the itinerant picture but is difficult to realize in the localized magnetic moment picture. arXiv submission processing window: 2026-04-06 21:27 to 2026-04-07 17:55 UTC.\n1. Tunable superconductivity and spin density wave in La3Ni2O7/LaAlO3 thin films Relevance Score: 5.7793 Authors: Yu-Han Cao, Kai-Yue Jiang, Hong-Yan Lu, Da Wang, Qiang-Hua Wang Link: http://arxiv.org/abs/2604.05590v1 Summary: Using first-principles calculations and the singular-mode functional renormalization group method, we systematically investigate the effect of interlayer nickel-nickel distance on the ground state in La₃Ni₂O₇/LaAlO₃ thin films. The results show that a smaller interlayer distance leads to a C-type spin density wave (interlayer ferromagnetic coupling), while a larger interlayer distance yields a G-type spin density wave (interlayer antiferromagnetic coupling). Between these two phases, an s±-wave superconducting state emerges, dominated by pairing in the Ni 3d₃z²⁻ᵣ² orbital. This finding explains the origin of superconductivity observed in the thin films under ambient pressure and predicts that applying pressure will suppress the superconducting transition temperature until the system enters the C-type spin density wave. If confirmed experimentally, this prediction will provide deep insight into the nature of electronic correlations in this system, as the C-type spin density wave naturally emerges within the itinerant electron picture, whereas it is difficult to realize within the local magnetic moment picture (where interlayer spins remain antiferromagnetically coupled).\n2. Visualizing the interplay of dual electronic nematicities in kagome superconductors Relevance Score: 4.2490 Authors: Yunmei Zhang, Jun Zhan, Ping Wu, Yun-Peng Huang, Qixiao Yuan, Hongyu Li, Zhuying Wang, Wanru Ma, Shuikang Yu, Kunming Zhang, Wanlin Cheng, Deshu Chen, Minrui Chen, Tao Wu, Ziji Xiang, Xianxin Wu, Zhenyu Wang, Xianhui Chen Affiliations: Chinese Academy of Sciences, University of Science and Technology of China Link: http://arxiv.org/abs/2604.05506v1 Summary: Using scanning tunneling microscopy to investigate the electronic structure of CsV₃Sb₅ at various temperatures and with titanium doping reveals two distinct nematic order parameters: one associated with the triple-Q charge density wave (CDW), and the other manifested as C₂ symmetric distortion of the vanadium d_{x²-y²} Fermi surface pockets without breaking translational symmetry. The latter persists even at high doping levels and elevated temperatures where CDW is completely suppressed. In moderately doped samples, its nematic orientation differs from that induced by CDW, whereas in pristine samples, the two eventually align at a lower characteristic temperature once the quasiparticles of vanadium orbitals become coherent. Combined with Ginzburg-Landau analysis, these observations suggest that the two nematic orders originate from different kagome lattice orbitals and exhibit rich interactions. This work offers new insights into the complex intertwined electronic orders in this material family and establishes a rare platform for the coexistence and coupling of multiple nematic orders.\n3. Understanding insulating ferromagnetism in LaCoO3 films under tensile strain Relevance Score: 4.0543 Authors: Ali Barooni, Murod Mirzhalilov, Mohit Randeria, Patrick M. Woodward, Maryam Ghazisaeidi Affiliations: The Ohio State University Link: http://arxiv.org/abs/2604.05193v1 Summary: Using density functional theory calculations, this study systematically investigates the magnetic ground state of stoichiometric LaCoO₃ thin films under tensile strain applied by a SrTiO₃ substrate. A ferromagnetic insulating ground state is identified, featuring a unique arrangement of Co³⁺ ions in ordered high-spin and low-spin states, forming a 2×2 columnar structure separated by low-spin planes, which yields a high-spin-low-spin-low-spin repeating sequence along the [100] and [010] directions. Electronic structure analysis confirms an energy gap of approximately 0.98 eV. Evaluation of superexchange interactions reveals ferromagnetic coupling between high-spin Co³⁺ ions via 90° pathways and antiferromagnetic coupling via 180° pathways, both mediated by empty σ* orbitals of low-spin Co³⁺ ions. The strength and abundance of the 90° ferromagnetic interactions are sufficient to overcome the antiferromagnetic competition, thereby stabilizing the ferromagnetic insulating state. This model elucidates the microscopic mechanism by which tensile strain alone can drive ferromagnetic insulating behavior in LaCoO₃ thin films.\n4. Numerically Exact Study of Flat-Band Superconductivity Relevance Score: 3.8801 Authors: I. S. Tupitsyn, B. Currie, B. V. Svistunov, E. Kozik, N. V. Prokof\u0026rsquo;ev Link: http://arxiv.org/abs/2604.05997v1 Summary: Using a controlled diagrammatic Monte Carlo method combined with combinatorial summation algorithms, we precisely computed the pairing response of the half-filled flat-band attractive Hubbard model on the Lieb lattice. The results reveal that over a wide range of temperatures and interaction strengths, the pairing response exhibits a linear divergence with decreasing temperature, characteristic of Gaussian critical behavior, and undergoes a sharp crossover to long-range superfluid correlations at a characteristic temperature (T_), providing a strict upper bound for the two-dimensional BKT transition temperature. Systematic investigations of three band structures—the gapless standard Lieb lattice, the symmetry-broken gapped lattice, and the symmetry-preserving gapped lattice—show that (T_) scales linearly with the attraction strength (|U|) in the weak-interaction regime, saturating to a maximum value in the strong-coupling limit. Among these, the standard gapless Lieb lattice yields the highest linear coefficient and the largest (T_) (approximately 0.07 times the hopping energy). Introducing a band gap reduces the maximum (T_), while intra-band dispersion induced by symmetry breaking further suppresses flat-band superconductivity. The study suggests that, under suitable conditions such as moderate electron-phonon coupling, flat-band systems hold potential for realizing high-temperature superconductivity.\n5. Optically induced thermal demagnetization and switching of antiferromagnetic domains in NiO and CoO thin films Relevance Score: 3.6437 Authors: Maciej Dąbrowski, Tong Wu, Connor R. J. Sait, Jia Xu, Paul S. Keatley, Yizheng Wu, Robert J. Hicken, Olena Gomonay Affiliations: University of Exeter, Johannes Gutenberg-University Mainz, Fudan University, Shaanxi University of Technology Link: http://arxiv.org/abs/2604.05806v1 Summary: This study demonstrates all-optical manipulation of antiferromagnetic domains in NiO/Pt and CoO/Pt thin films via magneto-optic birefringence imaging. Experiments reveal that a single laser pulse induces thermal demagnetization of the antiferromagnet, causing random domain redistribution, while scanning the laser beam enables controlled domain wall motion, achieving partial switching of the antiferromagnetic order. The underlying mechanism is explained by an analytical model: the temperature gradient generated by the moving beam exerts a thermal pressure akin to a ponderomotive force on the domain walls, driving their motion. Crucially, by simply reversing the direction of the thermal gradient, 90° domains can be reversibly switched without relying on electric currents. This work provides a new approach for ultrafast optical control of fully compensated antiferromagnets, with potential applications in nonvolatile memory technologies and antiferromagnetic spintronics.\n6. Key Role of Charge Disproportionation in Monoclinic Semiconducting Fe$_2$PO$_5$, a Room-Temperature d-Wave Altermagnet Candidate Relevance Score: 3.6067 Authors: Zhen Zhang, Mohd Anas, Andrey Kutepov, Parashu Kharel, Vladimir Antropov Link: http://arxiv.org/abs/2604.06114v1 Summary: This study, combining experiments and theoretical calculations, confirms the monoclinic semiconductor structure and d-wave altermagnetism of β-Fe₂PO₅ at room temperature. In the tetragonal metallic state, density functional theory with Hubbard U correction (DFT+U) reveals an electronic instability that induces charge disproportionation, subsequently driving monoclinic distortion and forming a narrow band gap. Only when both symmetry-breaking energy-lowering channels—charge disproportionation and structural distortion—are considered simultaneously in the calculations can the experimentally observed semiconducting behavior (band gap of approximately 0.26 eV) be successfully described; constraining the system to tetragonal symmetry yields only a metallic state. By systematically adjusting the U value and the degree of structural distortion, a nearly unique quadratic relationship is found between the Bader charge difference and the band gap, and when the charge difference reaches about 0.19 |e|, the band gap matches the experiment. Fe₂PO₅ is therefore defined as a correlation- and hybridization-assisted, distortion-coupled charge-disproportionated semiconductor, representing a rare room-temperature semiconducting d-wave altermagnet and providing an ideal platform for studying the coexistence of altermagnetism and charge density waves in quasi-one-dimensional systems.\n7. Quantum spin liquid ground state with the evidence of roton-like excitations at elevated temperatures in the triangular-lattice delafossite YbCuSe$_2$ Relevance Score: 3.5063 Authors: K. Bhattacharya, Y. Tokiwa, M. Majumder Link: http://arxiv.org/abs/2604.05784v1 Summary: We present a comprehensive experimental study of magnetization, specific heat, and muon spin relaxation (μSR) on high-quality single crystals of the triangular-lattice delafossite YbCuSe₂. Magnetization measurements reveal easy-plane anisotropy, while thermodynamic and μSR evidence indicates the absence of magnetic order or spin freezing down to 0.03 K (≤ J_avg/250), establishing a dynamic fluctuating quantum spin liquid (QSL) ground state. Specific heat data uncover multiple characteristic energy scales: T_H ≈ 4.5 K, T_L ≈ 1.8 K, and T^* ≈ 0.7 K. Below T^*, μSR detects kinetic phase separation: approximately 73% of spins form a QSL state, while the remaining spins become isolated due to disorder. Notably, the unconventional temperature dependence of the μSR relaxation rate between T_H and T_L reveals roton-like gapped excitations, a feature never before observed in any QSL system, and these excitations precede the stabilization of the low-temperature QSL state below 0.3 K. These findings establish YbCuSe₂ as a unique QSL platform, providing important insights for further experimental and theoretical exploration.\n8. Three-dimensional zigzag correlations in the van der Waals Kitaev magnet RuBr$_3$ Relevance Score: 3.3595 Authors: H. Gretarsson, R. Iwazaki, F. Sato, H. Gotou, S. Francoual, J. Nasu, Y. Imai, K. Ohgushi, J. Chaloupka, B. Keimer, H. Suzuki Link: http://arxiv.org/abs/2604.05346v1 Summary: Using Ru L₃-edge resonant X-ray scattering, this study systematically reveals the zigzag magnetic order and fluctuation characteristics in the van der Waals Kitaev magnet RuBr₃. Experiments show that long-range zigzag magnetic order vanishes at the Néel temperature (T_N = 34 K), but above T_N, zigzag correlations persist with significant spectral weight redistribution along the interlayer direction. Resonant inelastic X-ray scattering (RIXS) measurements indicate that interlayer magnetic interactions in RuBr₃ are markedly stronger than in the isostructural compound RuCl₃, attributed to the spatial extension of Br 4p orbitals, which enhances interlayer electron hopping and stabilizes three-dimensional zigzag correlations. Density functional theory calculations further confirm that the in-plane magnetic Hamiltonian is nearly identical to that of RuCl₃, yet the interlayer interactions result in a higher Néel temperature and greater stability of the three-dimensional magnetic order in RuBr₃. This finding challenges the conventional perception of van der Waals materials as inherently two-dimensional systems, underscoring the critical role of heavy ligand ions in interlayer coupling and offering new insights for tuning Kitaev quantum spin liquid phases.\n9. The effect of Nb and O on the martensitic transformation in the Ti-Nb-O alloys Relevance Score: 3.3556 Authors: Kristián Šalata, Dalibor Preisler, Josef Stráský, Jiří Kozlík, Lukáš Horák, Václav Holý Affiliations: Charles University Link: http://arxiv.org/abs/2604.05725v1 Summary: In this study, a series of Ti-(8-28)Nb-(0-3)O alloys were prepared and subjected to solution treatment in the β phase region. The microstructure and crystallography were characterized using X-ray diffraction, electron microscopy, and reciprocal space mapping. By employing two-dimensional XRD orientation simulation, all 12 crystallographically equivalent α″ martensite variants originating from individual β grains were successfully distinguished, and the atomic shuffle parameter y describing the β→α″ transformation was quantitatively evaluated. The results indicate that Nb primarily governs the evolution of α″ martensite: increasing Nb content stabilizes the β phase, shifting the α″ structure toward higher symmetry (manifested as systematic changes in lattice parameters and an increase in the y value), thereby suppressing the transformation to the hexagonal α′ phase. The role of oxygen alters the transformation pathway: at low Nb content, oxygen inhibits ω phase formation and promotes the β→α″ transformation; at high Nb content, oxygen suppresses long-range martensitic transformation, leading to retained β phase or the formation of competing ω phase. These effects are attributed to local lattice distortions induced by interstitial oxygen atoms.\n10. Stability and superstructural ordering of alkali-triel-pnictide clathrates A$_8$T$_{27}$Pn$_{19}$ Relevance Score: 3.3528 Authors: Frank Cerasoli, Xiaochen Jin, Genevieve Amobi, Kirill Kovnir, Davide Donadio Link: http://arxiv.org/abs/2604.05264v1 Summary: This study systematically investigates the stability of unconventional clathrates in the A₈T₂₇Pn₁₉ family of alkali-metal–trivalent-element–pnictogen compounds using high-throughput density functional theory calculations, establishing trends in formation energy, structure, and electronic properties. Electronic structure calculations and first-principles molecular dynamics simulations reveal that the ionization potential of guest alkali-metal atoms significantly influences the stability of electron-precise clathrates and their rattler vibrational behavior. Attempted target reactions from elemental precursors yielded two new ternary compounds but not the target clathrate phases. Further analysis indicates that the stability of clathrates containing heavy elements such as bismuth strongly depends on spin–orbit coupling, a factor often neglected in high-throughput formation energy calculations. The study also describes the correlation between chemical-induced superstructure ordering and Wyckoff sites in the prototype type-I clathrate unit cell. Ultimately, 20 new stable clathrates yet to be synthesized are predicted, revealing dominant stability factors and framework size conditions, providing theoretical guidance for the design and synthesis of novel functional materials.\n11. Tractable model for a fractionalized Fermi liquid (FL$^*$) on a square lattice Relevance Score: 3.3478 Authors: Piers Coleman, Elio J. König, Aaditya Panigrahi, Alexei Tsvelik Link: http://arxiv.org/abs/2604.06157v1 Summary: We propose an analytically solvable model of a fractionalized Fermi liquid (FL*) on a square lattice, constructed by Kondo coupling conduction electrons to a Yao-Lee-type Z2 spin liquid with a Majorana Fermi surface. Due to the static nature of the Z2 gauge field, the model can be solved analytically to logarithmic accuracy. Mean-field treatment reveals two phases: one where fractionalized fermions of the spin liquid hybridize with conduction electrons to form a common Fermi surface—a small Fermi surface violating the Luttinger count—and another where the two components remain decoupled. The small Fermi surface phase exhibits a momentum-dependent coherence factor, naturally reproducing the Yang-Rice-Zhang form of the Green\u0026rsquo;s function and Fermi arc features. Thermal fluctuations induce a strong diamagnetic response, while quantum fluctuations at the quantum critical point cause a logarithmic divergence of the Sommerfeld coefficient. This model provides a controlled theoretical framework for understanding the pseudogap and Fermi surface reconstruction in cuprate superconductors.\n12. Robust quantized thermal conductance of Majorana floating edge bands in d-wave superconductors Relevance Score: 3.3388 Authors: Yanmiao Han, Yu-Hao Wan, Zhaoqin Cao, Rundong Zhao, Qing-Feng Sun Link: http://arxiv.org/abs/2604.05588v1 Summary: This study proposes and characterizes a new class of Majorana boundary states—floating Majorana edge bands (FMEBs)—which emerge in two-dimensional superconductors that break time-reversal symmetry yet exhibit helical transport. Unlike conventional chiral or helical edge modes, FMEBs form counterpropagating Majorana modes that are separated in momentum and isolated from the bulk continuum. Their minimal generation mechanism is identified through anisotropic Wilson masses in a two-band Bogoliubov–de Gennes (BdG) model, and a microscopic realization is achieved in a quantum anomalous Hall (QAH) insulator proximitized by a d-wave superconductor. Using nonequilibrium Green’s function (NEGF) simulations, clear transport signatures are revealed: quantized total thermal conductance in two-terminal devices and robust half-quantized thermal conductance plateaus in four-terminal geometries, thereby unambiguously distinguishing FMEBs from the chiral QAH phase. These thermal responses remain stable under finite temperature, moderate long-range disorder, and finite chemical potential. These findings suggest that FMEBs offer an experimentally feasible route to realizing helical Majorana transport in systems lacking time-reversal symmetry, with direct implications for topological quantum computation.\n13. Many-body description of two-dimensional van der Waals ferroelectric $α-$In$_2$Se$_3$ Relevance Score: 3.2659 Authors: Denzel Ayala, Dimitar Pashov, Tong Zhou, Kirill Belashchenko, Mark van Schilfgaarde, Igor Žutić Affiliations: National Laboratory of the Rockies Link: http://arxiv.org/abs/2604.05220v1 Summary: This paper, using bilayer and sandwich structures of α-In₂Se₃ as examples, reveals that conventional density functional theory (DFT) may be unreliable for describing the electronic structures of two-dimensional van der Waals ferroelectrics. Although such materials are generally considered weakly correlated, their electronic properties depend strongly on the polarization configuration of the multilayer system, making calculations far more challenging than anticipated. By extending the Green\u0026rsquo;s function implementation in the open-source Questaal package, the researchers developed a high-fidelity many-body theory based on the quasiparticle self-consistent GW approximation. The results show that even advanced hybrid functional methods fail to correctly predict a nonzero band gap for bilayer In₂Se₃, and that properties such as charge density, polarization, and band offset deviate significantly from the many-body picture. This work underscores the necessity of many-body calculations for accurately understanding key properties of two-dimensional ferroelectrics and opens new opportunities for further research using the Questaal framework.\n14. Zr Concentration-Dependent Sub-Lattice Phase-Field Model of Hf1-xZrxO2: Analysis of Phase Composition and Polarization Switching Relevance Score: 3.2547 Authors: Tae Ryong Kim, Sumeet K. Gupta Link: http://arxiv.org/abs/2604.05184v1 Summary: This study develops a sublattice phase-field model incorporating zirconium concentration dependency to analyze the phase composition and polarization switching in Hf₁₋ₓZrₓO₂ thin films. The model extends the time-dependent Ginzburg-Landau equation to the sublattice level, introduces concentration-dependent interaction parameters and gradient coefficients, and, after experimental calibration, successfully describes the charge-voltage characteristics for Zr concentrations x ranging from 0.5 to 1.0. By elucidating the thermodynamic preferences and kinetic transition barriers of the orthorhombic and tetragonal phases through the sublattice energy landscape, the phase-field framework simultaneously enables spatiotemporal resolution of polarization and electric field distributions, naturally reproducing multi-domain polarization and mixed-phase states. The model replicates the experimentally observed transition from ferroelectric to antiferroelectric behavior with increasing x: the orthorhombic phase dominates at low concentrations, while the tetragonal phase stabilizes at high concentrations. A key finding is that at intermediate concentrations (x = 0.7–0.8), the energies of the two phases are comparable, and stray electric fields near domain walls induce locally inhomogeneous field distributions, resulting in mixed-phase compositions and spatially interleaved polarization reversal, manifested as a more gradual charge-voltage curve. By linking the energy landscape with spatial field effects, this model provides deep insights into the ferroelectric-antiferroelectric crossover in Hf₁₋ₓZrₓO₂.\n15. Band-basis decomposition of superfluid weight in magic-angle twisted bilayer graphene: Quantifying geometric and conventional contributions Relevance Score: 3.1155 Authors: Jian Zhou Link: http://arxiv.org/abs/2604.05994v1 Summary: Based on the Bistritzer-MacDonald continuum model, this study employs a current operator decomposition in the band basis to systematically separate the superfluid weight of magic-angle twisted bilayer graphene into a conventional contribution (from band velocity) and a geometric contribution (from interband coherence). The results show that within the flat-band subspace, the quantum geometric contribution accounts for 22%–26% of the total superfluid weight, depending on the pairing symmetry, with cross terms negligible to machine precision. When remote bands are included, the geometric fraction rises to approximately 55%–58%, while the conventional contribution converges within 2% error, demonstrating that remote bands contribute entirely through interband coherence. The geometric fraction peaks at 27%–33% near filling factor ν = ±2 (where superconductivity is strongest) and remains insensitive to the gap size over the experimentally relevant range. This decomposition provides a quantitative baseline for quantum-geometry-enhanced superfluidity in magic-angle twisted bilayer graphene and indicates that models considering only flat bands systematically underestimate the geometric contribution.\n16. Chemical Short-Range Order Regulates Hydrogen Energetics and Hydrogen-Dislocation Interactions in CoNiV Relevance Score: 3.0937 Authors: Beihan Chen, Dalia Sayed Ahmed, Yang Yang, Miaomiao Jin Affiliations: Pennsylvania State University Link: http://arxiv.org/abs/2604.05352v1 Summary: The research team developed a machine learning interatomic potential for the Co-Ni-V-H system and systematically investigated the effects of chemical short-range order (CSRO) on hydrogen thermodynamics and hydrogen-dislocation interactions in CoNiV alloys using combined Monte Carlo and molecular dynamics simulations. The simulations revealed a strong V-centered CSRO in the alloy, which suppresses direct V-V bonding and significantly reshapes the hydrogen solid solution energy landscape: compared to the chemically random alloy, the ordered state exhibits a higher average hydrogen solid solution energy and a reduced number of strong binding sites, indicating a decrease in bulk hydrogen uptake. At extended Shockley partial dislocations, hydrogen preferentially segregates to the tensile core region, forming shallow-level, reversible traps whose binding is much weaker than that of chemical trapping states. These results demonstrate that local chemical order strongly regulates hydrogen-dislocation coupling, providing key mechanistic insights for understanding and controlling the hydrogen-induced deformation behavior of CoNiV alloys from an atomic-scale perspective.\n17. Valence Bond Glass and Glassy Spin Liquid in Disordered Frustrated Magnets Relevance Score: 3.0225 Authors: Soumyaranjan Dash, Vansh Narang, Sanjeev Kumar Link: http://arxiv.org/abs/2604.05501v1 Summary: This study employs a semiclassical Monte Carlo method to analyze the thermodynamic behavior of the square-lattice spin-1/2 J1-J2 Heisenberg model with quenched disorder in the highly frustrated region. Through the analysis of frozen parameters, spin-spin correlation distributions, and specific heat, it is found that the ground state is a valence bond glass phase, characterized by frozen spin correlations and the absence of local magnetic moments, which melts into a glassy spin liquid at finite temperatures and eventually transitions to a paramagnetic phase. The results indicate that the low-temperature specific heat anomaly originates from collective singlet excitations (such as the rotation of singlet pairs) rather than spinon excitations, and is therefore insensitive to external magnetic fields. This feature can serve as a robust experimental signature of the valence bond glass phase, providing a new interpretation of thermodynamic data for candidate quantum spin liquid materials in disordered frustrated magnets, and suggesting that the glassy spin liquid represents a correlated quantum disordered phase of matter distinct from conventional quantum spin liquids.\n18. Bias controlled Interlayer Exchange Coupling Relevance Score: 3.0071 Authors: Nathan A. Walker, Alex D. Durie, Andrey Umerski Link: http://arxiv.org/abs/2604.05705v1 Summary: This study demonstrates, through computer simulations and non-equilibrium Green\u0026rsquo;s function methods, that the sign of non-equilibrium interlayer exchange coupling (ooeIEC) can be altered under an applied electrical bias. The system comprises an insulating segment connected to an exchange-coupled ferromagnetic trilayer (FM/NM/FM) placed between semi-infinite leads. When the trilayer contains a quantum well state within the ferromagnetic hybridization gap, a relatively small electrical bias is sufficient to switch the lowest energy state of the trilayer between parallel and antiparallel configurations. Three types of insulating segments are considered: a single tunneling barrier, a resonant tunneling barrier, and an amorphous insulating barrier; in each case, the bias dependence of ooeIEC is found to be strongly influenced by the system\u0026rsquo;s conductance. The findings indicate that the key to achieving the lowest switching current density lies in the use of strongly confined quantum well states.\n","permalink":"https://nickelates.uk/en/posts/2026-04-07-arxiv-daily/","summary":"\u003cblockquote\u003e\n\u003cp\u003e\u003cstrong\u003eDaily Overview\u003c/strong\u003e:\nThe highlight of today\u0026rsquo;s work focuses on an in-depth understanding of the electronic structure of mixed Ruddlesden-Popper nickelates. In [1], a study based on DFT+singular mode functional renormalization group method reveals the critical role of interlayer Ni-Ni distance in governing the ground-state phase diagram of La3Ni2O7/LaAlO3 thin films: a shorter interlayer distance tends to form C-type spin density wave (with ferromagnetic interlayer coupling), a longer interlayer distance leads to G-type spin density wave (with antiferromagnetic interlayer coupling), while the intermediate region stabilizes an s±-wave superconducting state dominated by Ni 3d₃z²⁻ʳ² orbital pairing. This theoretical picture successfully explains the experimental observation of superconductivity in thin films under ambient pressure and predicts that applying pressure will suppress the superconducting transition temperature, ultimately entering a C-type spin density wave. If experimentally verified, this prediction would strongly reveal the itinerant electron nature of electronic correlations in this system, as the C-type spin density wave naturally emerges in the itinerant picture but is difficult to realize in the localized magnetic moment picture.\n\u003cstrong\u003earXiv submission processing window\u003c/strong\u003e: 2026-04-06 21:27 to 2026-04-07 17:55 UTC.\u003c/p\u003e","title":"arXiv Daily: nickelate superconductors 2026-04-07"},{"content":" Daily Overview: Today\u0026rsquo;s highlights focus on deepening the understanding of the electronic structure and superconducting pairing mechanism in mixed Ruddlesden-Popper nickelates. [1] Using RIXS technique, the collective spin excitations in trilayer nickelate La₄Ni₃O₁₀ were systematically analyzed. It was found that the magnetic excitation bandwidth is comparable to that of bilayer systems but with lower spectral weight. Combined with linear spin-wave modeling, the study reveals stronger three-dimensional magnetism and the critical impact of reduced electronic correlations on magnetic evolution, providing new perspectives on the magnetism-superconductivity correlation within the family. [2] Meanwhile, multimodal terahertz spectroscopy was employed to study (La,Pr)₃Ni₂O₇ thin films. From both linear and nonlinear responses, the superconducting pairing symmetry (s±-wave) and normal-state pseudogap features were extracted simultaneously. It was also pointed out that the superconducting state coexists and competes with another ordered state, providing important experimental constraints for understanding the unconventional mechanism of nickel-based superconductivity. arXiv submission processing window: 2026-04-06 01:39 to 2026-04-06 18:00 UTC.\n1. Collective spin excitations in trilayer nickelate La$_4$Ni$_3$O$_{10}$ Relevance Score: 5.2877 Authors: Ying Chan, Yuehong Li, Yujie Yan, Xunyang Hong, Tianren Wang, Marli dos Reis Cantarino, Yinghao Zhu, Enkang Zhang, Lixing Chen, Jun Okamoto, Hsiao-Yu Huang, Di-Jing Huang, N. B. Brookes, Johan Chang, Yao Shen, Jun Zhao, Qisi Wang Link: http://arxiv.org/abs/2604.04643v1 Summary: Resonant inelastic X-ray scattering (RIXS) at the Ni L edge on single crystals of the trilayer nickelate La4Ni3O10 reveals collective spin excitations with a bandwidth of approximately 60 meV, comparable to that of the bilayer nickelate La3Ni2O7, but with significantly reduced spectral weight, indicating weaker electronic correlations in the trilayer system. Localized spin excitations at around 100 and 200 meV are also observed, originating from local dipole and quadrupole excitations. The dispersive magnetic excitations exhibit three-dimensional characteristics, and fitting with linear spin-wave theory yields comparable in-plane and out-of-plane exchange coupling parameters, with the interlayer coupling being the strongest. The results indicate that La4Ni3O10 possesses stronger three-dimensional magnetism, with its spin dynamics consistent with spin-density-wave order, while the reduced electronic correlations and three-dimensional multi-orbital character are key factors leading to differences in its magnetic excitation spectrum compared to the bilayer nickelate, providing important insights into the evolution of magnetism and its connection to superconductivity in the Ruddlesden-Popper nickelate family.\n2. Multimodal Terahertz Spectroscopy of the Pairing Symmetry and Normal-State Pseudogap in (La,Pr)$_3$Ni$_2$O$_7$ Films Relevance Score: 5.1288 Authors: Shuxiang Xu, Guangdi Zhou, Hao Wang, Tianyi Wu, Wei Wang, Liyu Shi, Dong Wu, Haoliang Huang, Xinbo Wang, Jinfeng Jia, Qi-Kun Xue, Zhuoyu Chen, Tao Dong, Nanlin Wang Affiliations: Southern University of Science and Technology, Tsinghua University, Beijing Academy of Quantum Information Sciences, Peking University, Chinese Academy of Sciences, Shanghai Jiao Tong University, Quantum Science Center of Guangdong-Hong Kong-Macao Greater Bay Area, Center for High Pressure Science and Technology Advanced Research Link: http://arxiv.org/abs/2604.04421v1 Summary: By combining linear terahertz time-domain spectroscopy with third-harmonic generation, this study systematically probes the superconducting pairing symmetry and normal-state pseudogap in compressively strained (La,Pr)₃Ni₂O₇ thin films. Linear terahertz spectroscopy reveals a significant suppression of low-frequency spectral weight below the superconducting transition temperature, accompanied by a weak coherence peak and a large residual conductivity persisting down to near-zero temperature, consistent with a disordered s±-wave pairing scenario. The nonlinear third-harmonic signal sharply enhances upon entering the superconducting state, but its response persists above the superconducting transition temperature, exhibiting a kink at approximately 100 K, which is attributed to the normal-state pseudogap based on similar temperature scales observed in angle-resolved photoemission spectroscopy on analogous films. This study establishes (La,Pr)₃Ni₂O₇ as a bulk superconductor with s±-wave-like pairing, where superconductivity coexists and likely competes with another ordered state, providing a new platform for exploring unconventional superconducting mechanisms beyond cuprates and iron-based superconductors.\n3. Discovery of Quasi One Dimensional Superconductivity in PtPb3Bi Relevance Score: 4.2708 Authors: Shashank Srivastava, Yash Vardhan, Anshu Kataria, Pradyumna Bawankule, Poulami Manna, Prabin Kumar Naik, Rahul Verma, Rhea Stewart, James S. Lord, Adrian D. Hillier, Mathias S. Scheurer, D. T. Adroja, Bahadur Singh, Ravi Prakash Singh Link: http://arxiv.org/abs/2604.04653v1 Summary: PtPb3Bi is a newly discovered quasi-one-dimensional Bi-based superconductor crystallizing in the non-centrosymmetric space group P42/mnm. Resistivity, magnetic susceptibility, and specific heat measurements confirm type-II superconductivity below 3.01(1) K. Transverse-field muon spin rotation (TF-μSR) and specific heat data reveal fully gapped isotropic s-wave pairing with moderate electron-phonon coupling (BCS parameter ~2.27), while zero-field μSR indicates preserved time-reversal symmetry in the superconducting state. Transport measurements show low carrier mobility, consistent with diffusive normal-state transport. Electronic structure calculations reveal strong dispersion along the quasi-one-dimensional c-axis and relatively flat bands in the in-plane direction, leading to significant Fermi surface nesting in the kx-ky plane, which corresponds to the charge density wave (CDW) transition observed experimentally at 280(1) K. Analysis of Wannier charge center flow and surface state dispersion confirms nontrivial band topology. Combining experimental results with pairing symmetry analysis, the most likely superconducting state is spin-singlet s-wave, with the CDW order further reconstructing the bands while retaining a full gap. These findings establish PtPb3Bi as a novel quasi-one-dimensional superconductor with a nontrivial electronic structure, making it a potential candidate for topological superconductivity.\n4. Two-Channel Allen-Dynes Framework for Superconducting Critical Temperatures: Blind Predictions Across Five Orders of Magnitude and a Quantum-Metric No-Go Result Relevance Score: 4.0647 Authors: Jian Zhou Link: http://arxiv.org/abs/2604.04719v1 Summary: This paper proposes a two-channel Allen-Dynes framework that unifies phonon-mediated and spin fluctuation-mediated pairing channels for predicting superconducting critical temperature (Tc). Channel 1 employs the standard Allen-Dynes formula with material-specific electron-phonon coupling constants as input, while Channel 2 extracts spin fluctuation coupling parameters from inelastic neutron scattering data. Blind tests on 19 materials covering conventional superconductors, MgB₂, iron-based superconductors, heavy fermions, cuprates, and hydrides show that predicted Tc values span five orders of magnitude from 0.4 K to 250 K, with a coefficient of determination R² of 0.96, requiring no free parameters. This work also proves an impossibility result for a quantum metric: the Peotta-Törmä geometric superfluid weight, though crucial for flat-band systems, cannot serve as a universal predictor for Tc because it relates to band structure topology rather than pairing strength. The framework further reveals that the spin fluctuation channel is the dominant factor enhancing Tc in unconventional superconductors, and accordingly provides quantitative design rules for materials with Tc exceeding 100 K.\n5. From Ferrimagnetic Insulator to superconducting Luther-Emery Liquid: A DMRG Study of the Two-Leg Lieb Lattice Relevance Score: 4.0594 Authors: Alexander Nikolaenko, Subir Sachdev Link: http://arxiv.org/abs/2604.05027v1 Summary: Using the density matrix renormalization group method, we systematically investigate the ground-state phase diagram of the two-leg Lieb ladder Hubbard model. At half filling, the system is in a ferromagnetic Mott insulator state consistent with Lieb\u0026rsquo;s theorem. Away from half filling, a state with nonzero total spin and zero charge gap persists up to a filling fraction n_c ≈ 2/3; at lower incommensurate fillings, the system exhibits a Luttinger liquid with one charge mode and one spin mode. Notably, a narrow window near the onset of ferromagnetic order at n_c ≈ 2/3 hosts a superconducting Luther-Emery phase with dominant sxy-wave pairing. By extracting correlation lengths via infinite DMRG, we confirm that within this window the pairing correlation length exceeds the charge correlation length, and both spin and charge modes are gapped, establishing the predominance of superconducting fluctuations. This work reveals a transition from a ferromagnetic insulator to a superconducting Luther-Emery liquid in the strongly correlated Lieb lattice and provides new insight into exotic pairing mechanisms near quantum critical points.\n6. Topological surface states revealed by the Zeeman effect in superconducting UTe2 Relevance Score: 4.0237 Authors: Zhen Zhu, Hans Christiansen, Yudi Huang, Kaiming Liu, Zheyu Wu, Shanta R. Saha, Johnpierre Paglione, Alexander G. Eaton, Andrej Cabala, Michal Vališka, Rafael M. Fernandes, Andreas Kreisel, Brian M. Andersen, Vidya Madhavan Affiliations: University of Illinois at Urbana-Champaign, University of Maryland, Canadian Institute for Advanced Research, Uppsala University, University of Copenhagen, University of Cambridge, Charles University Link: http://arxiv.org/abs/2604.04883v1 Summary: This study utilizes vector magnetic field scanning tunneling microscopy to directly observe topological surface states (TSS) in the spin-triplet superconductor UTe₂. Atomic-scale spectroscopy reveals substantial intragap density of states at Te sites, nearly filling the superconducting gap, while adjacent atomic sites remain gapped. Upon applying a magnetic field, the intragap states at Te sites are selectively suppressed, resulting in a spatially uniform and significantly deepened superconducting gap. This site-selective gap evolution quantitatively agrees with theoretical predictions, indicating that the TSS primarily possess Te orbital character. Spectral function calculations incorporating Zeeman coupling reproduce the magnetic field response. These results provide spectroscopic fingerprints of long-sought topological surface states in superconductors and establish UTe₂ as a robust platform for exploring intrinsic topological superconductivity.\n7. Signature of Unconventional Superconductivity in the High Temperature Normal State Resistivity Relevance Score: 3.9261 Authors: Yuchen Wu, Yiwen Liu, Wanyue Lin, Zohar Nussinov, Sheng Ran Link: http://arxiv.org/abs/2604.16433v1 Summary: This study employed machine learning methods to analyze the resistivity data of iron-based superconductors in the normal state (high-temperature range of 150–300 K) and revealed a strong correlation between normal-state resistivity and superconductivity. The research team performed cubic polynomial fitting on the resistivity curves of 175 single-crystal or thin-film samples, extracted the coefficients as features, and trained linear regression and random forest models. The results demonstrate that even far above the superconducting transition temperature (Tc), normal-state resistivity can effectively distinguish superconducting from non-superconducting samples (classification accuracy exceeding 80%), and even exhibits some predictive capability for Tc values (the random forest model achieved an R² of 0.43). Notably, the temperature window of predictive information is much broader than previous studies focusing on the vicinity of Tc, and the features related to superconductivity are distributed across multiple scattering channels (first-order, second-order, and third-order terms), rather than originating solely from a single scattering mechanism (e.g., the linear term characteristic of strange metal transport). This finding challenges the traditional view that the superconducting pairing mechanism is only associated with normal-state behavior near Tc, revealing the existence of superconducting \u0026ldquo;fingerprints\u0026rdquo; in the high-temperature normal state, thereby opening new avenues for understanding unconventional superconducting mechanisms and utilizing machine learning to predict superconducting materials.\n8. Strongly Correlated Superconductivity in Twisted Bilayer Graphene: A Gutzwiller Study Relevance Score: 3.7566 Authors: Matthew Shu Liang, Yi-Jie Wang, Geng-Dong Zhou, Zhi-Da Song, Xi Dai Affiliations: Peking University, Hefei National Laboratory, Hong Kong University of Science and Technology Link: http://arxiv.org/abs/2604.04631v2 Summary: This study employs the variational Gutzwiller wavefunction method to investigate strongly correlated superconductivity in magic-angle twisted bilayer graphene, where the projection operator allows the breaking of charge U(1) symmetry to describe the superconducting order. By applying the Gutzwiller approximation to an eight-band model incorporating correlated f-orbitals and uncorrelated c-orbitals, and considering Coulomb repulsion U, phonon-mediated anti-Hund coupling, and intra-orbital Hund coupling, a phase diagram is constructed at filling ν=2.5. The results reveal that a dome-shaped Fermi liquid phase separates the weak-coupling BCS superconductivity at small U from the strong-coupling superconducting region at large U. The nematic superconducting state is stabilized across a broad phase diagram including realistic parameters, exhibiting a nodal gap and V-shaped density of states at large U through interaction-driven reconstruction of the superconducting gap. In the strongly correlated superconducting regime, the off-diagonal components of the projection operator strongly suppress f-orbital charge fluctuations while maintaining finite pairing order and large quasiparticle weights, distinct from conventional Mott insulators. Additionally, a small Fermi liquid state with an effective Fermi surface volume of ν+2 is identified, serving as the parent state for the conventional Fermi liquid phase at intermediate U (≲40 meV) and the strongly correlated superconducting phase at large U (≳40 meV). These findings elucidate the interplay between strong correlations and unconventional pairing in MATBG and establish a general Gutzwiller framework applicable to other strongly correlated superconductors.\n9. Engineering 2D high-temperature ferromagnets with large in-plane anisotropy via alkali-metal decoration in a tetragonal CoSe monolayer Relevance Score: 3.5705 Authors: Yiran Peng, Yanfeng Ge, Yong Liu, Wenhui Wan Affiliations: Yanshan University Link: http://arxiv.org/abs/2604.04739v1 Summary: Through first-principles calculations, the authors propose that adsorbing alkali metal atoms (Li, Na, K, Rb, Cs) onto both sides of a tetragonal CoSe monolayer yields a series of stable two-dimensional ferromagnetic metallic materials, ACoSe, among which LiCoSe exhibits half-metallic characteristics. Compared with the pristine CoSe monolayer, the alkali metal-decorated systems achieve a Curie temperature exceeding 300 K, a magnetocrystalline anisotropy energy greater than 800 μeV/Co, and an in-plane easy magnetization axis. Mechanistic analysis reveals that the coupling of alkali metal atoms increases the local magnetic moment of Co ions, enhances ferromagnetic RKKY and superexchange interactions, and simultaneously weakens the direct antiferromagnetic exchange between Co ions. Furthermore, tensile strain can further enhance the magnetocrystalline anisotropy energy through band shifting and increase the nearest-neighbor exchange interaction J₁, thereby raising the Curie temperature. Among the studied systems, NaCoSe exhibits the highest magnetocrystalline anisotropy energy and excellent strain-tunable Curie temperature, making it the most promising candidate material. This work establishes alkali metal modification as an effective strategy for realizing two-dimensional ferromagnets with high Curie temperature and large magnetocrystalline anisotropy energy in tetragonal lattices.\n10. Real-space determination of orbital states driving successive phase transitions in FeV2O4 Relevance Score: 3.4800 Authors: Chihaya Koyama, Yusuke Nomura, Shunsuke Kitou, Taishun Manjo, Yuiga Nakamura, Takeshi Hara, Naoyuki Katayama, Yoichi Nii, Ryotaro Arita, Hiroshi Sawa, Taka-hisa Arima Affiliations: Tohoku University, Keio University, Nagoya Industrial Science Research Institute, Okayama University, The University of Tokyo, Japan Synchrotron Radiation Research Institute (JASRI), RIKEN Link: http://arxiv.org/abs/2604.04398v3 Summary: By integrating synchrotron-based X-ray diffraction valence electron density (VED) analysis with spin-polarized density functional theory calculations, this study uniquely determines the orbital states of Fe and V ions in the spinel oxide FeV₂O₄. Experimentally, it is found that temperature-dependent orbital occupancy rearrangements directly drive a continuous structural phase transition from cubic to tetragonal to orthorhombic, accompanied by the emergence of collinear and non-coplanar ferrimagnetic orders, thereby establishing a direct correspondence between orbital anisotropy and spin structure. This approach overcomes the theoretical multi-solution problem arising from the competition among electronic correlation, electron-lattice coupling, and spin-orbit interactions in strongly correlated systems, demonstrating that experimentally determined VED can provide decisive real-space constraints for competing theoretical solutions, offering a general framework for elucidating the microscopic mechanisms of complex phase transitions.\n11. Proton Quantum Effects in H$_3$S Electronic Structure: A Multicomponent DFT study via Nuclear-Electronic Orbital Method Relevance Score: 3.4731 Authors: Jianhang Xu, Aaron M. Schankler, Yosuke Kanai Link: http://arxiv.org/abs/2604.04860v1 Summary: This study employs the nuclear-electronic orbital density functional theory (NEO-DFT) method, treating hydrogen nuclei and electrons equivalently as quantum mechanical particles, to systematically investigate the influence of proton quantum effects on the electronic structure of high-pressure H₃S. Calculations reveal that nuclear quantum effects (NQEs) introduce subtle modifications to the band structure and density of states near the Fermi level, including features associated with van Hove singularities, yet these changes elevate the superconducting critical temperature (T_c) by only a few percent. In contrast, NEO-DFT calculations demonstrate that NQEs significantly alter hydrogen-dominated phonon dispersions, arising from the hardening of S-H bonds due to quantum effects. These results indicate that the experimentally observed reduction in T_c upon deuteration (D₃S) primarily stems from changes in phonon properties, while the direct impact of nuclear quantum effects on the electronic structure is minimal. This work provides a first-principles perspective on the role of proton quantum behavior in hydrogen-based superconductors.\n12. Topological Phase Transitions and Their Thermodynamic Fate in Arbitrary-$S$ Pyrochlore Spin Ice Relevance Score: 3.2839 Authors: Sena Watanabe, Yukitoshi Motome, Haruki Watanabe Link: http://arxiv.org/abs/2604.04346v1 Summary: This paper develops a self-consistent theoretical framework to classify the topological phases and critical phenomena of classical pyrochlore magnets with arbitrary spin S, investigating the roles of competing exchange and single-ion anisotropy. In the small w region, an exact duality reveals that integer spins exhibit continuous three-dimensional XY deconfined phase transitions, while half-integer spins always reside in a U(1) Coulomb liquid phase. In the large w region, local spin amplitudes are maximized, and macroscopic flux quantizes in multiples of 2S; topological loop gas mapping demonstrates that the physical ice rule is compatible with emergent Z_{2S} flux conservation only for S ≤ 3/2. For S = 3/2, the system maps onto a three-state Potts model, where the symmetry-allowed cubic invariant drives a first-order transition; for S ≥ 2, monopole contamination disrupts the discrete clock mapping, but exact decomposition of the partition function shows that hierarchical string fusion cascades exponentially suppress discrete perturbations, rendering them dangerously irrelevant at the three-dimensional XY fixed point and thereby protecting three-dimensional XY criticality. Finally, thermal monopoles act as effective symmetry-breaking fields that cut off defect strings, broadening continuous transitions into crossovers, whereas the first-order transition for S = 3/2 persists at finite temperature and terminates at a critical endpoint. Classical Monte Carlo simulations for spins up to S = 7/2 validate these analytical predictions.\n13. Atomic Structure of Grain Boundaries, Dislocations and Associated Strain in Templated Co-evaporated Photoactive Halide Perovskites Relevance Score: 3.2632 Authors: Huyen T Pham, Siyu Yan, Zhou Xu, Weilun Li, Sergey Gorelick, Michael B Johnston, Joanne Etheridge Affiliations: Monash University, University of Oxford Link: http://arxiv.org/abs/2604.04446v1 Summary: This study systematically resolves the atomic-scale defect structures of templated co-evaporated FA₀.₉Cs₀.₁PbI₃₋ₓClₓ perovskite thin films using customized low-dose electron microscopy. The films exhibit a preferential orientation along the ⟨001⟩ direction, with grains randomly rotated around this axis, consistent with the Volmer-Weber growth mechanism. Atomic-scale imaging identifies the atomic arrangements of high-angle and low-angle grain boundaries, reveals edge dislocations and their asymmetric strain fields (compressive strain on one side of the core and tensile strain on the other), and observes dislocations associated with stacking faults. These atomic-level insights clarify which grain boundaries and intragrain defects may act as non-radiative recombination centers or alter the local bandgap, providing direct evidence for understanding the key defects that limit the performance of perovskite solar cells.\n14. Multiferroicity in the Presence of Exchange Bias: The Case of Spinel CoMn2O4 Relevance Score: 3.2110 Authors: P. Kumar, P. Das, B. K. Kuanr, S. Patnaik Affiliations: Jawaharlal Nehru University Link: http://arxiv.org/abs/2604.04880v1 Summary: Researchers synthesized spinel CoMn₂O₄ polycrystalline samples using the conventional solid-state method, and confirmed the pure tetragonal phase (space group I4₁/amd) through X-ray diffraction and Raman spectroscopy. DC magnetization measurements revealed two magnetic phase transitions at T₁ ≈ 186 K and T₂ ≈ 86 K, with the low-temperature transition corresponding to Yafet–Kittel ferrimagnetic ordering. Near T₂, a frequency-independent anomaly in the temperature dependence of the dielectric constant was observed, suggesting coupling between lattice dynamics and spin ordering. Additionally, a significant exchange bias effect was detected below T₂. The variation of the dielectric constant under an applied magnetic field followed a quadratic dependence on magnetization, consistent with predictions from Ginzburg–Landau theory. However, detailed pyroelectric current measurements indicated the absence of intrinsic ferroelectric ordering in the samples. This study reveals that CoMn₂O₄ exhibits magnetodielectric coupling and strong magnetodielectric tunability without an external field, but due to the lack of intrinsic ferroelectricity, its multiferroic behavior is characterized by magnetodielectric coupling rather than coexistence of ferroelectricity and ferromagnetism.\n15. Broken Symmetry-driven Weyl Semimetal Phase in Zn-Substituted EuMn$_2$Sb$_2$ Relevance Score: 3.1484 Authors: Deep Sagar, Arti Kashyap Link: http://arxiv.org/abs/2604.04574v2 Summary: Through first-principles calculations, this work investigates the effect of Zn substitution on the magnetic and electronic structures of the layered compound EuMn₂Sb₂. The results indicate that the parent compound EuMn₂Sb₂ is a C-type antiferromagnetic semiconductor with a band gap of approximately 0.628 eV, whereas Zn substitution significantly alters the magnetic exchange interactions, leading to a ferromagnetic order and half-metallic character (metallic in the majority spin channel and semiconducting in the minority spin channel). Under spin-orbit coupling, both time-reversal and spatial inversion symmetries are broken, resulting in the formation of Weyl nodes near the Fermi level, which act as Berry curvature monopoles and generate topologically protected Fermi arc surface states. This work establishes EuMnZnSb₂ as a tunable platform that intrinsically couples magnetism and topology, and demonstrates that chemical substitution is an effective strategy for constructing magnetic Weyl semimetals in correlated electron systems, with potential implications for spintronics and topological transport phenomena.\n16. Effects of Spin Fluctuation and Disorder on Topological States of Quasi 2D Ferromagnet Fe1/5CrTe2 Relevance Score: 3.0880 Authors: M. Lamba, P. Saha, K. Yadav, N. Kamboj, S. Patnaik Affiliations: National Physical Laboratory, Jawaharlal Nehru University Link: http://arxiv.org/abs/2604.04864v1 Summary: Through magnetization and magnetotransport studies on the quasi-two-dimensional van der Waals ferromagnet Fe₁/₅CrTe₂, the Curie temperature is found to be as high as 182 K, and the saturation magnetization exhibits a quadratic temperature dependence, indicating the presence of long-wavelength spin fluctuations. Resistivity analysis reveals a dominant T^(3/2) contribution, reflecting strong coupling between conduction electrons and local spins. The magnetoresistance below the Curie temperature shows a linear, unsaturated, negative field dependence, consistent with the suppression of spin-disorder scattering. Anomalous Hall effect analysis indicates that the skew scattering mechanism associated with Fe-related disorder dominates, but through systematic separation of intrinsic and extrinsic components, the intrinsic anomalous Hall conductance is found to follow a linear scaling relation with saturation magnetization over a wide temperature range. This behavior aligns with the long-wavelength spin fluctuation framework, where thermal spin disorder reduces the net magnetization without significantly altering the electronic band structure. These results reveal Fe₁/₅CrTe₂ as a new van der Waals ferromagnet where spin fluctuations and disorder coexist, with a well-defined topological contribution from the Berry curvature.\n17. Light-modulated exchange bias in multiferroic heterostructures Relevance Score: 3.0576 Authors: Huan Tan, Zheng Ma, Cynthia Bou Karroum, Matthieu Liparo, Jean-Philippe Jay, David Spenato, David T. Dekadjevi, Luis Martinez Armesto, Alberto Quintana, Jordi Sort Affiliations: Institució Catalana de Recerca i Estudis Avançats (ICREA), Univ. Brest, Catalan Institute of Nanoscience and Nanotechnology (ICN2), Universitat Autònoma de Barcelona Link: http://arxiv.org/abs/2604.04555v1 Summary: This study constructs a multiferroic heterostructure using (011)-oriented Pb(Mg1/3Nb2/3)O3-Pb(Zr,Ti)O3 (PMN-PZT) single crystal substrates combined with Fe80Ga20 (FeGa) ferromagnetic layers and Ir20Mn80 (IrMn) antiferromagnetic layers, achieving non-contact modulation of the exchange bias field via strain-mediated magnetoelectric coupling by exploiting the photostrictive effect induced by visible light (405 nm laser) irradiation on the backside of PMN-PZT. Experimental results show that upon exposure to blue light with a power density as low as 0.1 W cm⁻² at room temperature, the exchange bias field decreases from 252.9 Oe to 231.5 Oe; this modulation process is reversible, non-thermal, and accompanied by no significant change in coercivity. By varying the light intensity, multilevel exchange bias fields and magnetization states can be further achieved. This discovery overcomes the limitations of traditional electric control methods and provides a new physical mechanism for developing low-power, wireless, multi-state opto-magnetic storage technologies.\n","permalink":"https://nickelates.uk/en/posts/2026-04-06-arxiv-daily/","summary":"\u003cblockquote\u003e\n\u003cp\u003e\u003cstrong\u003eDaily Overview\u003c/strong\u003e:\nToday\u0026rsquo;s highlights focus on deepening the understanding of the electronic structure and superconducting pairing mechanism in mixed Ruddlesden-Popper nickelates. [1] Using RIXS technique, the collective spin excitations in trilayer nickelate La₄Ni₃O₁₀ were systematically analyzed. It was found that the magnetic excitation bandwidth is comparable to that of bilayer systems but with lower spectral weight. Combined with linear spin-wave modeling, the study reveals stronger three-dimensional magnetism and the critical impact of reduced electronic correlations on magnetic evolution, providing new perspectives on the magnetism-superconductivity correlation within the family. [2] Meanwhile, multimodal terahertz spectroscopy was employed to study (La,Pr)₃Ni₂O₇ thin films. From both linear and nonlinear responses, the superconducting pairing symmetry (s±-wave) and normal-state pseudogap features were extracted simultaneously. It was also pointed out that the superconducting state coexists and competes with another ordered state, providing important experimental constraints for understanding the unconventional mechanism of nickel-based superconductivity.\n\u003cstrong\u003earXiv submission processing window\u003c/strong\u003e: 2026-04-06 01:39 to 2026-04-06 18:00 UTC.\u003c/p\u003e","title":"arXiv Daily: nickelate superconductors 2026-04-06"},{"content":" Daily Overview: Dear readers, welcome to today\u0026rsquo;s curated overview of papers in the nickel-based superconductivity field. Although no studies directly focusing on nickelates were published today, multiple papers address physical mechanisms highly relevant to the core issues in nickel-based superconductivity, warranting attention. [1] By decoupling the contributions of electrons and phonons to the superconducting transition temperature in hydrides, it is revealed that the electronic component dominates superconductivity and is governed by parameters such as bond length and electron localization function. This analytical approach can be directly transferred to the trade-off between electronic correlations and electron-phonon coupling in nickelates. [2] Using quantum Monte Carlo methods to study the optical SSH model on a triangular lattice, an s-wave superconducting phase is found at three-quarter filling. This result provides important insights for understanding the electron-phonon coupling-induced superconducting pairing mechanism in nickelates, particularly regarding kinetic frustration effects on non-bipartite lattices. [4] d-wave altermagnetism is realized in orthorhombically twisted bilayer CrPS₄, and the mechanisms of spin splitting and symmetry breaking offer a new perspective for exploring the possible coexistence of altermagnetic order and superconductivity in nickel-based superconductors. [5] A structure–property framework for decoherence in superconducting qubits is proposed, and its method of decoupling microstructure topology from geometric coupling provides methodological inspiration for controlling quantum coherence in nickelate thin films and heterostructures. These works enrich our understanding of the coupling among superconductivity, spin, and lattice in strongly correlated electronic systems from various angles, and are expected to provide new theoretical tools and experimental directions for nickel-based superconductivity research. arXiv submission processing window: 2026-04-05 04:07 to 2026-04-05 15:33 UTC.\n1. Disentangling electronic and phononic contributions to high-temperature superconductivity in X2MH6 hydrides Relevance Score: 3.9134 Authors: Feng Zheng, Shiya Chen, Zhen Zhang, Renhai Wang, Feng Zhang, Zi-zhong Zhu, Cai-Zhuang Wang, Vladimir Antropov, Yang Sun, Kai-Ming Ho Affiliations: Jimei University, Guangdong University of Technology, Iowa State University, Xiamen University, U.S. Department of Energy Link: http://arxiv.org/abs/2604.04151v1 Summary: To reveal how isoelectronic substitution influences the high-temperature superconductivity of the X₂MH₆ hydride family, this study decouples the contributions to the superconducting transition temperature (Tc) into phononic and electronic components and analyzes them separately. The results indicate that the electronic contribution dominates Tc within this family and is governed by three key parameters: the X–H bond length, the electron localization function (ELF) network value of hydrogen, and the projected density of states of hydrogen at the Fermi level. A figure of merit composed of these three parameters exhibits a strong correlation with Tc. Pressure exerts a competitive effect on superconductivity: shortening the X–H bond enhances the electronic contribution, while simultaneously increasing phonon frequencies weakens the phononic contribution, so the net dependence of Tc on pressure depends on the balance between the two. By systematically decoupling and quantifying the electronic and phononic mechanisms, this study provides a comprehensive understanding of superconductivity in X₂MH₆ hydrides and offers practical guidance for designing new high-Tc hydride superconductors.\n2. The optical Su-Schrieffer-Heeger model on a triangular lattice Relevance Score: 3.7069 Authors: Max Casebolt, Sohan Malkaruge Costa, Benjamin Cohen-Stead, Richard Scalettar, Steven Johnston Link: http://arxiv.org/abs/2604.04123v1 Summary: This study systematically investigates the optical Su-Schrieffer-Heeger (SSH) model on a triangular lattice using determinant quantum Monte Carlo methods. By tuning the carrier concentration, electron-phonon coupling strength, and phonon energy Ω, the authors identify two key doping regimes: at quarter filling (⟨n⟩=0.5), where the non-interacting Fermi surface is circular, the system undergoes a phase transition from a metal to a bond-order wave (BOW) insulator that breaks the local C6 rotational symmetry; at three-quarter filling (⟨n⟩=1.5), where the non-interacting Fermi surface is hexagonal, a different BOW phase emerges at small Ω, while an s-wave superconducting phase appears at sufficiently large Ω. The superconducting pairing tendency is related to the possible reversal of the effective hopping sign under large lattice displacements. Unlike the square-lattice SSH model, no enhanced magnetic correlations are observed in this study. These results reveal the interplay between kinetic frustration induced by the triangular lattice geometry and electron-phonon coupling, and delineate a rich low-temperature phase diagram, providing new insights into electron-phonon systems on non-bipartite lattices.\n3. Temperature Dependent Magnetic and Structural Properties of Al Substituted Nanostructured Ferrites with Large Coercive Fields Relevance Score: 3.2536 Authors: P. Maltoni, R. K. Dokala, P. Pramanik, R. Araujo, T. Edvinsson, S. A. Ivanov, B. Almqvist, G. Varvaro, A. Capobianchi, N. Yaacoub, C. Hervoches, A. Martinelli, R. C. Pullar, D. Peddis, R. Mathieu Affiliations: Le Mans Université, Uppsala University, Università Ca’ Foscari Venezia, Czech Academy of Sciences, CNR, University of Genoa, Lomonosov Moscow State University Link: http://arxiv.org/abs/2604.04152v1 Summary: This study systematically investigates the temperature-dependent structural, magnetic, vibrational, and dielectric properties of Al-substituted M-type hexagonal ferrites SrFe₁₂₋ₓAlₓO₁₉ (x = 1–2.4). Neutron powder diffraction and Mössbauer spectroscopy reveal that Al³⁺ preferentially substitutes Fe³⁺ at the spin-up octahedral 2a and 12k sites, disrupting the exchange coupling with the spin-down tetrahedral 4f sites, which leads to a gradual reduction in site magnetic moments and a systematic decrease in Curie temperature, a trend further confirmed by temperature-dependent magnetic susceptibility measurements. Raman spectroscopy shows distinct phonon anomalies near the Curie temperature, particularly for modes associated with Fe–O vibrations in bipyramidal sites, reflecting the weakening of 4e–12k and 4e–4f exchange paths. However, the coercivity increases significantly, with μ₀Hc reaching approximately 1.2 T for SrFe₉.₆Al₂.₄O₁₉, one of the highest values among similar materials. Magnetic susceptibility measurements indicate that although Al substitution weakens the superexchange network, it helps stabilize single-domain behavior. Overall, Al substitution achieves a substantial enhancement in coercivity through preferential site occupation and modulation of exchange interactions, while also providing a tunable pathway for high-temperature applications and the design of nanocomposite magnets.\n4. Emergent $d$-wave altermagnetism in orthogonally twisted bilayer CrPS$_4$ Relevance Score: 3.2324 Authors: Alberto M. Ruiz, Diego López-Alcalá, Rafael González-Hernández, José J. Baldoví Affiliations: Universidad del Norte, Universitat de València Link: http://arxiv.org/abs/2604.04072v1 Summary: Through first-principles calculations and symmetry analysis, this work demonstrates that orthogonally twisted (90° rotation) bilayer CrPS₄ can realize d-wave altermagnetism driven purely by structural rotation. The twisted stacking breaks partial joint symmetries of translation and time reversal, resulting in a fourfold rotational relationship between spin sublattices and thereby inducing altermagnetism. Calculations reveal a nonrelativistic spin splitting of up to 68 meV near the Fermi level, with the altermagnetic state further stabilized by interlayer compression and tuning of the Coulomb interaction U value. The resulting band structure exhibits significant spin-dependent anisotropy, enabling approximately 50% spin-to-charge conversion efficiency near the Fermi level and sizable giant magnetoresistance effects. This work establishes twisted CrPS₄ as a realistic platform for studying altermagnetism and highlights the potential of twistronics as a versatile route for advanced spintronics.\n5. Microstructural Topology as a Prescriptor for Quantum Coherence: Towards A Unified Framework for Decoherence in Superconducting Qubits Relevance Score: 3.2174 Authors: Vinayak P. Dravid, Akshay A. Murthy, Peter Lim, Gabriel T. dos Santos, Ramandeep Mandia, James M. Rondinelli, Mark C. Hersam, Roberto dos Reis Link: http://arxiv.org/abs/2604.03951v2 Summary: In superconducting qubits, improvements in decoherence are often difficult to attribute due to simultaneous changes in surface chemistry, microstructural topology, and device geometry. This paper proposes a channel-separable decoherence framework, where each loss channel is described as a reduced premonitor, with microstructural state variables independent of device geometry measurements, and geometric coupling functionals computable via field solutions without relying on surface chemistry. This product form is derived from a spatially resolved kernel representation and establishes a perturbative separability criterion that defines the effective region where variables can vary independently. The framework specifies five categories of premonitors corresponding to dominant loss pathways in transmon-type devices and achieves falsifiability through a pre-committed 2×2 experimental protocol: variables must satisfy independent row and column ratio tests within propagated uncertainties. Additionally, a minimal dataset specification standardizes inference reporting across laboratories. Part I establishes the conceptual and mathematical architecture, with coordinated experimental validation reserved for Part II. This work aims to formalize structure–property relationships in materials science and quantum engineering, providing a testable parsimonious description for coherence prediction in superconducting qubits.\n","permalink":"https://nickelates.uk/en/posts/2026-04-05-arxiv-daily/","summary":"\u003cblockquote\u003e\n\u003cp\u003e\u003cstrong\u003eDaily Overview\u003c/strong\u003e:\nDear readers, welcome to today\u0026rsquo;s curated overview of papers in the nickel-based superconductivity field. Although no studies directly focusing on nickelates were published today, multiple papers address physical mechanisms highly relevant to the core issues in nickel-based superconductivity, warranting attention. [1] By decoupling the contributions of electrons and phonons to the superconducting transition temperature in hydrides, it is revealed that the electronic component dominates superconductivity and is governed by parameters such as bond length and electron localization function. This analytical approach can be directly transferred to the trade-off between electronic correlations and electron-phonon coupling in nickelates. [2] Using quantum Monte Carlo methods to study the optical SSH model on a triangular lattice, an s-wave superconducting phase is found at three-quarter filling. This result provides important insights for understanding the electron-phonon coupling-induced superconducting pairing mechanism in nickelates, particularly regarding kinetic frustration effects on non-bipartite lattices. [4] d-wave altermagnetism is realized in orthorhombically twisted bilayer CrPS₄, and the mechanisms of spin splitting and symmetry breaking offer a new perspective for exploring the possible coexistence of altermagnetic order and superconductivity in nickel-based superconductors. [5] A structure–property framework for decoherence in superconducting qubits is proposed, and its method of decoupling microstructure topology from geometric coupling provides methodological inspiration for controlling quantum coherence in nickelate thin films and heterostructures. These works enrich our understanding of the coupling among superconductivity, spin, and lattice in strongly correlated electronic systems from various angles, and are expected to provide new theoretical tools and experimental directions for nickel-based superconductivity research.\n\u003cstrong\u003earXiv submission processing window\u003c/strong\u003e: 2026-04-05 04:07 to 2026-04-05 15:33 UTC.\u003c/p\u003e","title":"arXiv Daily: nickelate superconductors 2026-04-05"},{"content":" Daily Overview: Dear readers, welcome to today\u0026rsquo;s overview of papers in the nickel-based superconductivity field. While today\u0026rsquo;s list does not directly include studies on nickelate superconductors, [1] the work on interface and strain-tuned Weyl semimetal phases in SrNbO₃/LaFeO₃ heterostructures, and [4] the discovery of true pairing density waves in kagome lattices, both involve physical mechanisms (such as octahedral distortions and non-zero momentum pairing) that are highly relevant to core issues in the current nickel-based superconductivity research, and thus deserve attention. arXiv submission processing window: 2026-04-03 23:26 to 2026-04-04 18:14 UTC.\n1. Interface and Strain Control of Emergent Weyl Semimetallic Phase in SrNbO$_{3}$/LaFeO$_{3}$ Heterostructures Relevance Score: 4.4344 Authors: Sairam Ithineni, Pratik Sahu, Soumyakanta Panda, Aditya Mehta, Debashree Nayak, Amit Chauhan, Shwetha G Bhat, Niharika Mohapatra, K. Senapati, B. R. K. Nanda, D. Samal Link: http://arxiv.org/abs/2604.03596v1 Summary: This study successfully realizes a Weyl semimetal phase in SrNbO₃/LaFeO₃ heterojunctions through epitaxial strain and interface engineering. Transport measurements reveal a large, unsaturated magnetoresistance, nonlinear Hall response, and chiral anomaly features under parallel electric and magnetic fields, along with an anomalous Hall effect attributed to the proximity effect of the LFO layer. First-principles calculations indicate that the NbO₆ octahedra in the SNO layer exhibit an a⁰a⁰c⁻ rotation pattern, which, combined with interfacial lattice distortion, drives the formation of a twofold degenerate Weyl semimetal state protected by helical axis symmetry. Berry curvature calculations further confirm the presence of Berry curvature peaks with opposite signs in the upper and lower bands, consistent with the characteristics of Weyl nodes. This work highlights the critical role of strain and interfacial octahedral distortions in stabilizing the Weyl phase in transition metal oxide perovskite bilayers, offering an effective pathway to realize topological semimetal states in correlated oxides.\n2. Design A Family of 2D Nb-Based Multilayer Kagome Semimetals with High Fermi Velocity and Low Thermal Conductivity Relevance Score: 3.7443 Authors: En-Qi Bao, Xing-Yu Wang, Su-Yang Shen, Jun-Hui Yuan, Wen-Yu Fang, Jiafu Wang Affiliations: Hubei University of Science and Technology, Wuhan University of Technology Link: http://arxiv.org/abs/2604.03534v1 Summary: Based on the \u0026ldquo;1+3\u0026rdquo; multilayer kagome material design strategy, this study successfully designed nine stable two-dimensional niobium-based multilayer kagome monolayer materials (including Nb₆Cl₂S₃Br₆, etc.). These materials are all Dirac semimetals, with their Dirac cone structure primarily contributed by the dz² orbitals of the Nb-based kagome lattice. Hybrid functional calculations indicate that their Fermi velocities reach as high as 2.36–3.04×10⁵ m/s; meanwhile, the materials generally exhibit low phonon group velocities and short phonon lifetimes, resulting in lattice thermal conductivities of only 1.704–8.149 Wm⁻¹K⁻¹ at room temperature. This research not only strongly confirms the feasibility of the \u0026ldquo;1+3\u0026rdquo; multilayer kagome lattice design strategy for developing kagome materials but also establishes a benchmark for the study of niobium-based multilayer kagome materials.\n3. Analytical evaluation of surface barrier and resistance in iron-based superconducting multilayers for Superconducting Radio-Frequency applications Relevance Score: 3.7189 Authors: Carlos Redondo Herrero, Akira Miyazaki Link: http://arxiv.org/abs/2604.03702v1 Summary: This paper evaluates the application of iron-based superconductor (IBS) multilayer structures in superconducting radio-frequency cavities. The field distribution, vortex penetration field (maximum tolerable magnetic field), and surface resistance of the multilayer films were calculated using the London equations and Maxwell’s equations, and the layer parameters were optimized. For the FeSe/I/Nb structure, the optimal parameters (FeSe thickness 2 nm, insulating layer 5 nm) yield a maximum magnetic field of approximately 25.5 mT, a surface resistance of about 8.02 μΩ, and a power loss of approximately 0.0134 W/m²; for the FeSe/I/Nb₃Sn structure, with the same thickness of 2 nm/5 nm, the maximum magnetic field is about 33.7 mT, the surface resistance about 5.85 μΩ, and the power loss about 0.00818 W/m². Compared with conventional superconductor (e.g., NbN, Nb₃Sn) multilayer structures, the advantages of iron-based superconductors lie in their larger superconducting gap and smaller penetration depth, though their bulk surface resistance is higher. The introduced attenuation factor indicates that the surface resistance of the substrate material often dominates the overall loss, thus necessitating simultaneous optimization of high field and low loss. The conclusion notes that Nb₃Sn/I/Nb on a Nb substrate exhibits the best overall performance, but its mechanical brittleness limits application; FeSe/I/Nb shows comparable performance with better processability and is expected to operate at higher temperatures. The optimization strategy coupling the vortex penetration field and surface resistance proposed in this work provides a new direction for future multilayer structure design.\n4. Genuine pair density wave order on the kagome lattice Relevance Score: 3.6308 Authors: Han-Yang Liu, Da Wang, Ziqiang Wang, Qiang-Hua Wang Link: http://arxiv.org/abs/2604.03531v1 Summary: This study employs the advanced functional renormalization group method to discover, for the first time, a genuine primary pairing density wave (PDW) phase in a two-orbital Hubbard model on the kagome lattice. This PDW state exhibits Cooper pairing with nonzero center-of-mass momentum without an external magnetic field and contains neither a uniform superconducting component nor secondary structures arising from preexisting spin/charge density wave modulations, thereby overcoming two major challenges for PDW as a ground state. The key mechanism lies in the strong sublattice and orbital polarization of Bloch states on multiple Fermi pockets: they force zero-momentum Cooper pairing to be confined to the same sublattice, thereby suppressed by local Coulomb repulsion, whereas pairing between different sublattices is dominated by distinct Fermi pockets and carries nonzero total momentum, resulting in three degenerate PDW states at the M points of the Brillouin zone boundary. These degenerate states exhibit a novel intertwined order, from which topologically nontrivial chiral PDW states can be constructed via linear combinations. The PDW phase prevails over competing orders across a broad range of physical parameters, making it suitable for realization in actual materials. The paper suggests that this model can be experimentally verified in multi-orbital kagome materials such as CsCr3Sb5 and in cold-atom systems.\n5. A Top-Loading Point-Contact Spectroscopy Probe with In-Situ Sample Exchange for Dilution Refrigerators Relevance Score: 3.4857 Authors: Ghulam Mohmad, Atanu Mishra, Goutam Sheet Link: http://arxiv.org/abs/2604.03821v1 Summary: This paper reports the design and implementation of a top-loading point-contact spectroscopy probe integrated into a dilution refrigerator, enabling measurements at temperatures as low as 30 mK. The probe employs a needle-anvil geometry equipped with a low-temperature piezoelectric-driven nanopositioner for in situ formation of mesoscopic point contacts. Thermal anchoring strategies ensuring effective cooling of the probe to ultralow temperatures and reliable measurements, as well as solutions addressing the stable operation of the piezoelectric positioner at millikelvin temperatures, are discussed in detail. The probe performance was validated through point-contact spectroscopy measurements on Ta-doped TiSe₂ (Ta_xTi_{1-x}Se₂, x = 0.2, superconducting transition temperature T_c ≈ 2.3 K). The acquired spectra exhibit clear superconducting features that gradually weaken with increasing temperature and magnetic field. This platform provides a robust and versatile tool for spectroscopic studies of superconductors and other quantum materials under millikelvin temperatures and strong magnetic fields.\n6. Cascade of Spin Liquids in a Bilayer Triangular-lattice Antiferromagnet Rb_2Co_2(SeO_3)_3 Relevance Score: 3.3854 Authors: Xiaoyu Xu, Yunlong Wang, Xuejuan Gui, Jun Luo, Guijing Duan, Ke Shi, Zhaosheng Wang, Shuo Li, Huifen Ren, Chuanying Xi, Langsheng Ling, Zhanlong Wu, Ying Chen, Xiaohui Bo, Xinyu Shi, Kefan Du, Rui Bian, Jie Yang, Yi Cui, Rui Zhou, Jinchen Wang, Rong Yu, Weiqiang Yu Link: http://arxiv.org/abs/2604.03737v2 Summary: In the bilayer triangular lattice antiferromagnet Rb₂Co₂(SeO₃)₃, a cascade of field-driven spin liquid states has been discovered through high-field magnetization, specific heat, and nuclear magnetic resonance measurements, combined with theoretical modeling and Monte Carlo simulations. Four distinct magnetization plateaus are observed at 1/3, 1/2, 2/3, and 5/6 of the saturation magnetization. NMR spectral analysis reveals that the 1/3 plateau exhibits up-up-down antiferromagnetic order, the 1/2 plateau is partially ordered, while the 2/3 and 5/6 plateaus lack long-range magnetic order, signifying the formation of classical spin liquids. These spin liquid states are characterized by doubly degenerate up-down spin configurations (Ising dimers) and significant residual entropy arising from macroscopic ground-state degeneracy induced by field-controlled dilution of Ising dimers. Further theory and simulations reveal that the spin liquid at the 2/3 plateau is stabilized by lattice symmetry breaking, while the 5/6 plateau, due to interlayer dimer hopping that provides additional entropy, becomes a candidate for a quantum spin liquid. This work demonstrates that such bilayer Ising triangular lattice antiferromagnets offer a new platform for exploring diverse spin liquid states at both classical and quantum scales.\n7. Unconventional excitations and orbital-driven low-energy dispersions in chiral topological semimetals PdAsS, PdSbSe, and PdBiTe: a first-principles study Relevance Score: 3.2293 Authors: Roopam Pandey, Sudhir K Pandey Link: http://arxiv.org/abs/2604.03760v1 Summary: This study systematically investigates the electronic structures of chiral topological semimetals PdAsS, PdSbSe, and PdBiTe using first-principles density functional theory. Without spin-orbit coupling, spin-1 excitations (at the Γ point) and double Weyl points (at the R point) are identified; with spin-orbit coupling included, Rarita-Schwinger-Weyl fermions (at the Γ point) and double spin-1 excitations (at the R point) are observed. These higher-order nodes lie within an energy range of -0.5 to -0.85 eV. Additionally, eight new type-II Weyl points (without spin-orbit coupling) are found along the Γ-R line, and twelve new type-II Weyl points (with spin-orbit coupling) are discovered at generic momentum positions, results not previously reported. Low-energy dispersion analysis reveals that orbital hybridization significantly modifies the ideal dispersions: for spin-1 excitations, the middle band of PdBiTe is parabolic, while those of PdAsS and PdSbSe are relatively flat in the low-energy range; for double spin-1 excitations, the middle band of PdSbSe exhibits linear dispersion, whereas those of PdAsS and PdBiTe are parabolic. Finally, calculations show nontrivial surface states and Fermi arcs associated with the higher-order excitations. These findings provide important insights for understanding and designing topological materials.\n8. Shape of temperature dependence of spontaneous magnetization of various ferromagnets Relevance Score: 3.2065 Authors: A. Perevertov Affiliations: Institute of Physics of the Czech Academy of Sciences Link: http://arxiv.org/abs/2604.03704v1 Summary: This paper analyzes the shape of spontaneous magnetization temperature dependence curves for approximately forty ferromagnetic materials, using hyperelliptic equation (Lame curve) fitting to determine the shape rectangularity parameter η, which reflects the coupling strength between atomic vibrations and electron magnetic moments. Results indicate that η values range from 1.4 to 3.0, with iron exhibiting the largest rectangularity and antiferromagnetic materials along with Ni55Cu45 alloy showing the smallest. For metal alloys, η generally increases with the Curie temperature Tc, except for cobalt: despite having a Tc twice that of nickel, its magnetization curve in reduced coordinates is identical to that of nickel. Adding either ferromagnetic or non-ferromagnetic metals to iron or nickel leads to a decrease in η; the thermal expansion coefficient does not affect the curve, and zero-expansion Invar alloys still conform to the Lame curve. The study concludes that the hyperelliptic equation can effectively describe experimental data for most materials, and η can serve as a supplementary parameter for characterizing the temperature dependence of magnetization.\n9. First-principles theory of spin magnetic multipole moments in antiferromagnets Relevance Score: 3.0986 Authors: Hua Chen, Guang-Yu Guo, Di Xiao Link: http://arxiv.org/abs/2604.03578v1 Summary: This paper proposes a first-principles theory of spin magnetic multipole moments (SM³) that unifies the description of arbitrary-order multipole moments in antiferromagnets by introducing nonlocal spin density into macroscopic Maxwell\u0026rsquo;s equations. The method defines multipole moments as expansion coefficients of response functions in the long-wavelength limit, thereby eliminating the origin and unit-cell dependence inherent in traditional definitions and establishing a direct link to experimentally observable quantities such as boundary- or texture-induced spin densities. Based on first-principles calculated nonlocal spin densities, the authors propose a symmetry-constrained long-wavelength fitting scheme to extract SM³ of arbitrary order, and apply it to representative antiferromagnets including α-Fe₂O₃, Mn₃Sn, and Mn₃NiN. The calculations reveal that multipole moments exhibit significant system and symmetry dependence, while also elucidating the role of spin-orbit coupling; notably, in the weak coupling limit, clear predictions can be made based on symmetry principles. This work elevates magnetic multipole moments from a qualitative symmetry description to a quantitative predictive framework applicable to complex magnetic materials, laying the foundation for systematic investigation of multipolar order parameters in unconventional magnets.\n10. Scaling Breakdown as a Signature of Spinon-Gauge Interaction in the Quantum Spin Liquid YbZn$_2$GaO$_5$ Relevance Score: 3.0833 Authors: Shannon Gould, John Singleton, Rabindranath Bag, Sara Haravifard, Sheng Ran Link: http://arxiv.org/abs/2604.13087v1 Summary: High-field magnetization measurements and scaling analysis of the quantum spin liquid candidate material YbZn₂GaO₅ reveal that in the temperature range of 5 K to 70 K, the magnetization exhibits scale invariance characteristic of a zero-field quantum critical point; however, when the temperature drops below 3 K, this scaling behavior breaks down and cannot be restored by adjusting critical exponents. This breakdown temperature coincides precisely with the onset temperature of enhanced spin correlations observed in μSR measurements and the low-energy excitation energy scale detected by inelastic neutron scattering. Further analysis indicates that the form of the deviation from the scaling curve is consistent with the behavior expected from collective spinon excitations coupled via an emergent gauge field. The results suggest that the magnetization scaling behavior originates from quantum critical fluctuations rather than from the spin liquid phase itself, and the breakdown of scaling marks the emergence of low-energy intrinsic excitations upon entering the spin liquid phase. This work not only clarifies the relationship between scaling behavior and the spin liquid phase but also establishes high-field magnetization scaling as a sensitive thermodynamic probe for detecting emergent energy scales and fractionalized excitations in quantum spin liquids.\n","permalink":"https://nickelates.uk/en/posts/2026-04-04-arxiv-daily/","summary":"\u003cblockquote\u003e\n\u003cp\u003e\u003cstrong\u003eDaily Overview\u003c/strong\u003e:\nDear readers, welcome to today\u0026rsquo;s overview of papers in the nickel-based superconductivity field. While today\u0026rsquo;s list does not directly include studies on nickelate superconductors, [1] the work on interface and strain-tuned Weyl semimetal phases in SrNbO₃/LaFeO₃ heterostructures, and [4] the discovery of true pairing density waves in kagome lattices, both involve physical mechanisms (such as octahedral distortions and non-zero momentum pairing) that are highly relevant to core issues in the current nickel-based superconductivity research, and thus deserve attention.\n\u003cstrong\u003earXiv submission processing window\u003c/strong\u003e: 2026-04-03 23:26 to 2026-04-04 18:14 UTC.\u003c/p\u003e","title":"arXiv Daily: nickelate superconductors 2026-04-04"},{"content":" Daily Overview: Today\u0026rsquo;s highlights focus on an in-depth understanding of the electronic structure of mixed Ruddlesden-Popper nickelates. A key study employed time-resolved optical spectroscopy to reveal two high-energy electronic excitations in La₃Ni₂O₇ and their corresponding distinct density wave gaps, while elucidating the complex coupling behavior between phonons and electronic excitations, providing direct spectroscopic evidence for understanding many-body effects and the gap structure in this system. Additionally, several highly relevant studies from other systems offer insights into key physical issues underlying nickelate superconductivity. For example, the microscopic correlation between Mott insulator physics and Kondo hybridization observed in d-electron kagome lattices, and the anomalous phonon thermal Hall effect discovered in altermagnets, provide important references for exploring similar physical phenomena that may exist in nickelates from the perspectives of strongly correlated electronic states and novel magnetic excitations, respectively. arXiv submission processing window: 2026-04-03 01:38 to 2026-04-03 19:11 UTC.\n1. High-energy electronic excitations in La3Ni2O7 by time-resolved optical spectroscopy Relevance Score: 5.6279 Authors: Junzhi Zhu, Mengwu Huo, Yubin Wang, Yuxin Zhai, Lili Hu, Haiyun Huang, Xiu Zhang, Baixu Xiang, Mengdi Zhang, Yusong Gan, Zhiyuan An, Meng Wang, Qihua Xiong, Haiyun Liu Affiliations: Tsinghua University, Collaborative Innovation Center of Quantum Matter, Beijing Academy of Quantum Information Sciences, Sun Yat-Sen University, Chinese Academy of Sciences, Frontier Science Center for Quantum Information, University of Chinese Academy of Sciences Link: http://arxiv.org/abs/2604.02843v1 Summary: This study employs time-resolved optical spectroscopy to investigate the ultrafast dynamics of high-energy electronic excitations in bilayer nickelate La₃Ni₂O₇ from 10 K to room temperature at ambient pressure. Two high-energy electronic excitations originating from distinct interband transitions are identified at approximately 1.8 eV and 2.4 eV, revealing different density wave (DW) gaps of about 54 meV and 67 meV, respectively. The relaxation dynamics of these two excited states are well described by the Rothwarf-Taylor model. Additionally, four coherent Raman-active phonon modes are observed, exhibiting varying coupling strengths to the different electronic excitations. The phonon softening upon heating from about 100 K to room temperature can be explained by a semi-quantitative model incorporating thermal expansion and anharmonic phonon-phonon coupling, while the deviation of measured phonon frequencies from the model fit at low temperatures suggests an additional contribution from electron-phonon coupling. This work directly demonstrates the complex gap structure and phonon dynamics in this material, providing key insights into its density wave mechanism and many-body effects.\n2. Mott-Derived Local Moments and Kondo Hybridization in a d-electron Kagome lattice Relevance Score: 4.0772 Authors: Xing Zhang, Xintong Li, Boqin Song, Yuyang Xie, Qinghong Wang, Taimin Miao, Shusen Ye, Junhao Liu, Bo Liang, Neng Cai, Hao Chen, Wenpei Zhu, Mingkai Xu, Wei-Jian Li, Shun-Li Yu, Shenjin Zhang, Fengfeng Zhang, Feng Yang, Zhimin Wang, Qinjun Peng, Hanqing Mao, Zhihai Zhu, Guodong Liu, Zuyan Xu, Yi-feng Yang, Tianping Ying, Lin Zhao, X. J. Zhou Link: http://arxiv.org/abs/2604.02922v1 Summary: By combining scanning tunneling microscopy/spectroscopy (STM/STS) and angle-resolved photoemission spectroscopy (ARPES), this study reveals the microscopic origin of local magnetic moments in the d-electron Kondo lattice of the bilayer kagome metal CsCr₆Sb₆. At low temperatures, STS shows an asymmetric suppression of the density of states near the Fermi level, consistent with a Fano line shape, while ARPES detects sharp quasiparticle peaks; these low-energy features disappear with increasing temperature, corresponding to the onset of Kondo hybridization. Concurrently, STS reveals symmetric hump structures at about ±50 mV, and ARPES identifies weakly dispersive features at approximately 50 meV below the Fermi level, which persist at higher temperatures. The separation in energy and temperature scales supports a two-stage picture: the kagome flat band first undergoes Mott splitting due to strong correlations, forming lower and upper Hubbard bands; the occupied lower Hubbard band provides local magnetic moments, which subsequently hybridize with itinerant electrons at low temperatures via Kondo hybridization. These results establish a direct spectroscopic link between Mott insulator physics and Kondo hybridization, offering a clear microscopic mechanism for the generation of local moments and Kondo lattice behavior in d-electron systems.\n3. Enhanced Kadowaki-Woods Ratio and Weak-Coupling Superconductivity in Noncentrosymmetric YPt$_2$Si$_2$ Single Crystals Relevance Score: 3.9483 Authors: Gustavo Gomes Vasques, Shyam Sundar, Deisy Aristizábal-Giraldo, Juan F. Castello-Arango, Rafael Sá de Freitas, Adriano Reinaldo Viçoto Benvenho, Takahiro Onimaru, Jorge M. Osorio-Guillén, Marcos A. Avila Link: http://arxiv.org/abs/2604.03408v1 Summary: In this study, single crystals of the non-centrosymmetric superconductor YPt₂Si₂ were successfully synthesized using the Sn flux method, with a superconducting transition temperature Tc of approximately 1.67 K. The crystal quality was confirmed by powder X-ray diffraction and Laue diffraction, and the superconducting and normal-state properties were investigated through electrical transport and specific heat measurements down to 0.5 K. Experimental results show that, unlike LaPt₂Si₂, YPt₂Si₂ does not exhibit a charge density wave transition in the normal state, but instead displays a relatively large Kadowaki-Woods ratio and a linear temperature dependence of resistivity in the 50–300 K range, suggesting unconventional normal-state behavior. Analysis of superconducting parameters indicates that YPt₂Si₂ is a type-II superconductor with weak electron-phonon coupling. The superconducting-state specific heat data can be well fitted by an isotropic two-gap model, and the positive curvature of the upper critical field near Tc further supports two-gap superconductivity. First-principles density functional theory calculations reveal that the superconducting state is BCS-type, mainly contributed by d electrons, with the McMillan-Allen-Dynes formula estimating a Tc of 1.8 K, consistent with the experimental value. This study unveils the coexistence of an enhanced Kadowaki-Woods ratio and weak-coupling two-gap superconductivity in YPt₂Si₂.\n4. Disorder-induced chirality in superconductor-ferromagnet heterostructures revealed by neutron scattering and multiscale modeling Relevance Score: 3.8819 Authors: Annika Stellhorn, Juan G. C. Palma, Alicia Backs, Anders Bergman, Angela B. Klautau, Emmanuel Kentzinger, Connie Bednarski-Meinke, Steffen Tober, Elizabeth Blackburn, Juri Barthel, Nina-Juliane Steinke, Helena M. Petrilli, Ivan P. Miranda Affiliations: Linnaeus University, Universidade Federal do Pará, European Spallation Source ERIC, Universidade de S˜ao Paulo, Uppsala University, Forschungszentrum Jülich GmbH, Lund University, Institut Laue-Langevin Link: http://arxiv.org/abs/2604.02824v1 Summary: This study systematically investigates the chiral origin in FePd and Nb/FePd heterostructures by combining structural characterization, polarized analysis grazing-incidence small-angle neutron scattering, first-principles calculations, and deep-learning-assisted multiscale modeling. Experimental results reveal partial L1₀ ordering, atomic intermixing, antiphase boundaries, and depth-dependent defect gradients in FePd layers, with finite net magnetic chirality observed at room temperature. Neutron scattering asymmetry indicates that the primary chiral contribution lies in-plane, accompanied by an out-of-plane component related to depth-dependent magnetic inhomogeneities. Theoretical calculations demonstrate that chemical disorder, especially when coupled with compositional gradients, can induce a finite Dzyaloshinskii–Moriya interaction, stabilizing chiral finite-q magnetic modulations with mixed Bloch–Néel character, and the in-plane modulation lengths from mesoscopic models align with the experimentally observed range. This work identifies disorder and compositional gradients as intrinsic microscopic sources of net chirality in FePd-based thin films, confirming that the observed chirality does not arise solely from interfacial effects.\n5. Engineering Electrochromism in Ni-Deficient NiO through Defect, Dopant, and Strain Coupling Relevance Score: 3.5850 Authors: Katarina Jakovljević, Ana S. Dobrota, Igor A. Pašti, Natalia V. Skorodumova Affiliations: University of Belgrade, Serbian Academy of Sciences and Arts, 5th Belgrade Gymnasium, Luleå University of Technology Link: http://arxiv.org/abs/2604.02952v1 Summary: This study systematically analyzed the electrochromic behavior of nickel-deficient NiO(001) surfaces doped with Cu, Sn, and V using density functional theory, and examined the insertion process of alkali metal ions at surface nickel vacancies. The results indicate that Li insertion contributes nearly complete electron donation (approximately +0.9 e), but the destination of the injected electrons depends on the doping element: for V doping, the framework-dominated charge compensation mechanism is preserved, achieving conventional bleaching by filling the hole states associated with vacancies; Sn actively captures the injected charges, inducing dopant-assisted optical transitions and reversing the electrochromic response; Cu causes intermediate redistribution of the spectrum, though the dopant is not significantly reduced. Replacing Li with Na or K in the V-doped system does not alter the switching mechanism, confirming that hole-state filling dominates the optical behavior. Although biaxial tensile strain is energetically favorable for Li insertion, it reduces the optical contrast by altering the defect electronic structure. These results establish dopant activity, vacancy stability, and lattice strain as key parameters for modulating the electrochromism of NiO-based materials.\n6. Microscopic NMR evidence for successive antiferroelectric and antiferromagnetic order in the van der Waals magnet CuCrP$_2$S$_6$ Relevance Score: 3.4744 Authors: C. S. Saramgi, L. F. Prager, S. Selter, Y. Shemerliuk, S. Aswartham, B. Büchner, H. -J. Grafe, K. M. Ranjith Link: http://arxiv.org/abs/2604.02898v1 Summary: Through systematic investigations using 31P and 65Cu nuclear magnetic resonance (NMR) on the layered van der Waals magnet CuCrP2S6, successive structural and magnetic phase transitions have been revealed: a high-temperature paraelectric state, a paraelectric-like antiferroelectric state near 185 K, a long-range antiferroelectric state below 150 K, and antiferromagnetic order below the Néel temperature TN = 30 K. The evolutions of NMR spectra, shifts, spin-lattice relaxation rate (T1−1), and spin-spin relaxation rate (T2−1) provide microscopic fingerprints of these transitions. Below the antiferroelectric transition, 31P spectra and T1−1 split, indicating the emergence of two inequivalent P sites. The nearly isotropic transferred hyperfine coupling is extracted via K-χ analysis, and the anisotropy of the NMR shift is attributed primarily to dipolar contributions, differing from Mn2P2S6 and Ni2P2S6. The intralayer ferromagnetic exchange interaction Jintra ≈ -4.9 K is derived from the Curie-Weiss temperature, consistent with the antiferromagnetic stacking of ferromagnetic layers along the c-axis. The Moriya high-temperature relaxation rate, incorporating P–P dimer cross-correlation effects, is also evaluated. The critical divergence of T1−1 near TN yields a critical exponent γ ≈ 0.45(4), placing CuCrP2S6 in the three-dimensional Heisenberg universality class. These results provide microscopic evidence for the coexistence and interplay between electric dipole order and quasi-two-dimensional magnetism in this material.\n7. Unraveling Intrinsic Thermal Conductivity in Layered Conductive MOF Single Crystals Relevance Score: 3.4671 Authors: Jinkun Guo, Dongyang Wang, Zhiyi Li, Haoyang Zhang, Jiaxiang Zhang, Zeyue Zhang, Lei Sun, Junliang Sun, Jiawei Zhou, Chongan Di, Jinhu Dou Link: http://arxiv.org/abs/2604.02657v1 Summary: This study, for the first time, measured the intrinsic thermal conductivity along the π-π stacking direction of three layered conductive MOF single crystals (Cu₃HHTP₂, Co₉HHTP₄, and Nd₃HHTP₂) using microfabricated suspended devices, revealing ultralow values ranging from 0.075 to 0.194 W m⁻¹ K⁻¹. A key finding is that Nd₃HHTP₂ exhibits a high electrical conductivity of 398 S cm⁻¹, yet its thermal conductivity (0.148 W m⁻¹ K⁻¹) is comparable to those of the other two MOFs with much lower electrical conductivities, indicating that the classical Wiedemann-Franz law does not apply in such complex porous materials. Structural characterization reveals that incommensurate modulation and in-plane correlated disorder in Nd₃HHTP₂ crystals induce strong phonon scattering, which is the primary cause of its ultralow thermal conductivity. These results unveil, for the first time, the intrinsic thermal transport properties of LCMOF single crystals and confirm their potential as ideal \u0026ldquo;phonon glass-electron crystal\u0026rdquo; materials.\n8. Observation of anomalous thermal Hall effect in altermagnets Relevance Score: 3.3989 Authors: Wenbo Wan, Xu Zhang, Yixuan Luo, Yanfeng Guo, Shiyan Li Affiliations: Fudan University, Shanghai Research Center for Quantum Sciences, Collaborative Innovation Center of Advanced Microstructures, ShanghaiTech University, Hefei National Laboratory Link: http://arxiv.org/abs/2604.03183v2 Summary: This study systematically measured the thermal Hall effect in two representative altermagnetic candidate materials, MnTe and CrSb, revealing anomalous phonon thermal Hall signals. Altermagnets, as a third class of collinear magnets, exhibit both the zero net magnetization of antiferromagnets and the spin splitting of ferromagnets, yet previous experiments have observed limited anomalous Hall effects. By shifting the detection paradigm from charge carriers to heat carriers and utilizing transverse temperature difference measurements under a temperature gradient, significant anomalous phonon thermal Hall effects were observed in both MnTe (a semiconductor with phonon-dominated heat transport) and CrSb (a metal with substantial electronic contributions), while no corresponding anomalous signals were detected in the electrical channel. After subtracting the electronic contribution (based on the Wiedemann–Franz law) and the conventional linear magnetic field background, the extracted anomalous phonon thermal Hall conductivity showed saturation behavior similar to that in ferromagnets, but with a saturation field (≥1 T) far exceeding the weak ferromagnetic component (~0.1 T) in the samples, indicating that the effect does not originate from net magnetization. The study suggests that the coupling between long-range magnetic order and phonons in altermagnets is the core mechanism, possibly arising from Berry curvature transferred through magnon-phonon hybridization. This finding establishes the anomalous phonon thermal Hall effect as an intrinsic characteristic of altermagnets, providing a sensitive probe for identifying such novel quantum magnets and directly linking the Néel vector to lattice vibrations, thus opening new prospects for low-loss phononic devices and thermally readable memories.\n9. Evolution from Landau Quantization to Discrete Scale Invariance Revealed by Quantum Oscillations in Topological Materials Relevance Score: 3.2848 Authors: Jiayi Yang, Nannan Tang, Yunxing Li, Jiawei Luo, Huakun Zuo, Gangjian Jin, Ziqiao Wang, Haiwen Liu, Yanzhao Liu, Donghui Guo, XinCheng Xie, Jian Wang, Huichao Wang Affiliations: Collaborative Innovation Center of Quantum Matter, Peking University, Sun Yet-sen University, ShanghaiTech University, Quantum Science Center of Guangdong–Hong Kong–Macao Greater Bay Area (Guangdong), Beijing Normal University, Huazhong University of Science \u0026amp; Technology, Hefei National Laboratory Link: http://arxiv.org/abs/2604.02630v1 Summary: In the topological material HfTe5, this study, through magnetotransport measurements under high magnetic fields, observes for the first time a continuous evolution from low-field Shubnikov-de Haas oscillations to high-field log-periodic oscillations in the same system, both modulated by Fermi surface anisotropy. This evolution maps the transition from single-particle Landau levels to interaction-driven discrete scale-invariant quasi-bound state spectra, with entry into the quantum limit being a necessary condition for the emergence of log-periodic oscillations. By tuning the carrier concentration, it is found that vacuum polarization effects can effectively renormalize impurity charges, thereby quantitatively explaining the dependence of the scaling factor on carrier density. The results reveal complex interplays among Landau quantization, many-body electronic screening, and scale symmetry breaking, establishing Dirac solids as a controllable platform for exploring relativistic vacuum effects and emergent symmetries.\n10. Proximate quantum spin liquids and Majorana continua in magnetically ordered Kitaev magnets Relevance Score: 3.1501 Authors: Peng Rao, Roderich Moessner, Johannes Knolle Link: http://arxiv.org/abs/2604.03099v2 Summary: In this paper, a Stoner-type theory based on Majorana partons is employed to calculate the inelastic neutron scattering intensity of the extended Kitaev model within the random phase approximation, systematically investigating the spin excitation spectra in magnetically ordered phases adjacent to the Kitaev quantum spin liquid. The method is first validated through the antiferromagnetic Heisenberg model (restoring the linear Goldstone mode), and then accurately captures the order-by-disorder effect in the Kitaev-Heisenberg limit, with the phase diagram agreeing qualitatively with existing numerical results. The key finding is that in the intermediate and high energy regions, broad multi-spinon continua emerge in the Brillouin zone, providing a new mechanism for magnon decay and spectral line broadening that is distinct from conventional multi-magnon decay processes. Finally, modeling of the candidate material α-RuCl₃ reveals strong anisotropy in its zigzag ground state and stability under an external magnetic field, while reproducing the experimentally observed broad scattering continuum. This work demonstrates that in magnetically ordered phases proximate to quantum spin liquids, the parton framework can self-consistently describe the spectroscopic features ranging from low-energy magnons to high-energy continua.\n11. A Route to Nonrelativistic Altermagnetic Spin Splitting via Ultrafast Light Relevance Score: 3.0784 Authors: Huang-Zhao-Xiang Chen, Lin-Ding Yuan, Wen-Hao Liu, Lin-Wang Wang, Jun-Wei Luo, Zhi Wang Affiliations: Chinese Academy of Sciences, Northwestern University, University of Chinese Academy of Sciences Link: http://arxiv.org/abs/2604.02790v2 Summary: This study proposes a non-equilibrium route to generate non-relativistic alternating magnetic spin splitting in antiferromagnets via ultrafast light, without relying on relativistic angular momentum transfer, static symmetry breaking, or external fields. Using real-time time-dependent density functional theory simulations, it demonstrates that linearly polarized light in the antiferromagnetic perovskite KNiF₃ effectively breaks time-reversal symmetry through photoexcited charge redistribution and subsequent lattice distortion, thereby inducing momentum-dependent alternating magnetic spin splitting. Photoexcitation populates antibonding states, elongating Ni-F bonds, and under constant-volume constraints triggers octahedral rotations, producing out-of-phase rotational modes such as a[0] b[0] c[-] and a[0] b[-] c[-], corresponding to g-wave and d-wave spin splitting patterns. These patterns are directly linked to peaks in the anomalous Hall conductivity and are achievable without spin-orbit coupling. The study also establishes symmetry selection rules (Γν⊂Sym2) and momentum selection rules (q=0) for driving phonon modes, providing a new mechanism for ultrafast manipulation of alternating magnetism and extending the realization of altermagnetic materials to non-equilibrium states.\n12. Nonlinear Magnetic Orbital Hall Effect Induced by Spin-Orbit Coupling Relevance Score: 3.0092 Authors: Hui Wang, Huiying Liu, Yanfeng Ge, Xukun Feng, Jiaojiao Zhu, Jin Cao, Cong Xiao, Shengyuan A. Yang, Lay Kee Ang Link: http://arxiv.org/abs/2604.02636v1 Summary: This paper proposes a spin-orbit coupling-induced second-order nonlinear magnetic orbital Hall effect, which emerges as an odd function of the Néel vector in collinear antiferromagnets with combined time-reversal and translational symmetry. Through first-principles calculations, the researchers discovered a pronounced orbital Berry curvature dipole mechanism in the prototypical antiferromagnetic material CuMnAs, enabling the nonlinear orbital response to surpass its spin counterpart by two orders of magnitude, while maintaining a significant non-perturbative enhancement even under weak spin-orbit coupling. This effect simultaneously achieves two key functionalities: first, the electrical control of the Néel vector in the source antiferromagnet enables writing an out-of-plane orbital torque on an adjacent perpendicularly magnetized ferromagnet; second, the sensitive response of the nonlinear magnetic orbital Hall conductivity to a 180° reversal of the Néel vector facilitates the electrical readout of antiferromagnetic order. This work unveils new possibilities in topological antiferromagnetic orbitronics arising from the synergistic interplay between nonlinear orbital transport and spin-orbit coupling.\n","permalink":"https://nickelates.uk/en/posts/2026-04-03-arxiv-daily/","summary":"\u003cblockquote\u003e\n\u003cp\u003e\u003cstrong\u003eDaily Overview\u003c/strong\u003e:\nToday\u0026rsquo;s highlights focus on an in-depth understanding of the electronic structure of mixed Ruddlesden-Popper nickelates. A key study employed time-resolved optical spectroscopy to reveal two high-energy electronic excitations in La₃Ni₂O₇ and their corresponding distinct density wave gaps, while elucidating the complex coupling behavior between phonons and electronic excitations, providing direct spectroscopic evidence for understanding many-body effects and the gap structure in this system. Additionally, several highly relevant studies from other systems offer insights into key physical issues underlying nickelate superconductivity. For example, the microscopic correlation between Mott insulator physics and Kondo hybridization observed in d-electron kagome lattices, and the anomalous phonon thermal Hall effect discovered in altermagnets, provide important references for exploring similar physical phenomena that may exist in nickelates from the perspectives of strongly correlated electronic states and novel magnetic excitations, respectively.\n\u003cstrong\u003earXiv submission processing window\u003c/strong\u003e: 2026-04-03 01:38 to 2026-04-03 19:11 UTC.\u003c/p\u003e","title":"arXiv Daily: nickelate superconductors 2026-04-03"},{"content":" Daily Overview: Today\u0026rsquo;s highlight focuses on the in-depth understanding of the electronic structure of hybrid Ruddlesden-Popper nickelates. [1] Using resonant inelastic X-ray scattering, a direct comparison of the electronic and magnetic excitations between trilayer La₄Ni₃O₁₀ and bilayer La₃Ni₂O₇ was conducted. It was found that the trilayer compound exhibits weaker electronic correlations and interlayer magnetic exchange, which explains why its superconducting transition temperature of approximately 30 K is significantly lower than that of the bilayer (~80 K), establishing interlayer magnetic coupling and electronic correlations as key parameters. [2] First-principles calculations revealed the strain tuning mechanism in La₃Ni₂O₇ thin films, demonstrating that biaxial compressive strain enhances the Jahn-Teller splitting energy as the core microscopic factor for optimizing superconductivity. The calculated results are consistent with experiments. These works provide important experimental and theoretical evidence for understanding the superconducting pairing mechanism in layered nickelates. arXiv submission processing window: 2026-04-01 22:40 to 2026-04-02 19:26 UTC.\n1. Dissecting superconductivity in the Ruddlesden-Popper nickelates: The role of electron correlation and interlayer magnetic exchange Relevance Score: 5.7332 Authors: Xiaoyang Chen, Zezhong Li, Mei Xie, Deyuan Hu, Yiu-Fung Chiu, Stefano Agrestini, Wenliang Zhang, Yi Lu, Meng Wang, Mirian Garcia-Fernandez, Donglai Feng, Ke-Jin Zhou Link: http://arxiv.org/abs/2604.01902v1 Summary: This study employs resonant inelastic X-ray scattering (RIXS) to directly compare the electronic and magnetic excitation properties of trilayer nickelate La₄Ni₃O₁₀ and bilayer La₃Ni₂O₇. The results show that La₄Ni₃O₁₀ exhibits more itinerant behavior, evidenced by broader Ni d-d orbital excitations and a stronger fluorescence background, indicating weaker electronic correlations than in the bilayer system. Despite the weaker correlations, clear collective spin excitations are observed, including dispersive acoustic and optical magnon branches as well as incommensurate spin density waves (SDW). Using linear spin-wave theory analysis, the interlayer superexchange interaction Jz is extracted to be approximately 22 meV, significantly smaller than that in La₃Ni₂O₇. The weaker electron correlations and reduced interlayer magnetic exchange together account for the substantially lower superconducting transition temperature of the trilayer compound (about 30 K) compared to the bilayer (about 80 K). This study establishes interlayer magnetic coupling and electronic correlations as key parameters for superconductivity in layered nickelates, providing important constraints for understanding the superconducting pairing mechanism in this emerging family.\n2. Jahn-Teller distortion on strained La$_3$Ni$_2$O$_7$ thin films Relevance Score: 5.4859 Authors: Yuxin Wang, Zhan Wang, Fu-Chun Zhang, Kun Jiang Link: http://arxiv.org/abs/2604.02191v2 Summary: This study systematically analyzed the electronic structure of strained La₃Ni₂O₇ thin films using density functional theory calculations, revealing that biaxial compressive strain primarily elongates the outer apical Ni–O bonds while leaving the inner apical Ni–O bonds nearly unchanged, thereby significantly enhancing the Jahn–Teller splitting energy Δ_JT, yet the interlayer d_z² orbital hopping parameter t_⊥^z exhibits only a weak variation. Given that superconductivity emerges only when the in-plane lattice constant falls below a critical value, these results identify strain-enhanced Δ_JT as a key microscopic tuning parameter. The calculated Fermi surface topology and Hall response agree well with angle-resolved photoemission spectroscopy (ARPES) and Hall measurements on LaAlO₃ and SrLaAlO₄ substrates, confirming that Jahn–Teller distortion plays a central role in optimizing superconductivity in bilayer nickelates.\n3. Electronic-Structure Correlations Governing Superconductivity in Nb-Based High-Entropy Alloys Relevance Score: 4.4172 Authors: Md Sabbir Hossen Bijoy, Vladislav Korostelev, Deva Prasaad Neelakandan, Harshil Goyal, Steven E. Porterfield, Youming Xu, Shuchen Li, Xi Chen, Mark Adams, Barton C. Prorok, Konstantin Klyukin, Chanho Lee, Fariborz Kargar Affiliations: Auburn University, University of California, Riverside Link: http://arxiv.org/abs/2604.01446v1 Summary: A systematic study of niobium-based body-centered cubic high-entropy alloys (from binary to quinary), combined with electrical transport, specific heat, and magnetization measurements as well as first-principles and Eliashberg analyses, reveals that superconducting critical properties exhibit a non-monotonic variation with alloy complexity, and alloys with significant lattice distortion can still achieve higher critical temperatures and upper critical fields. Theoretical analysis indicates that the position of the Nb d-band relative to the Fermi level is the primary factor determining the electron-phonon coupling strength, critical temperature, and upper critical field, while lattice distortion, as a secondary modifying factor, generally weakens the coupling. The study ultimately establishes a detailed correlation map linking superconducting performance to electronic structure fingerprints and vibrational characteristics, providing a mechanism-based strategy for designing superconducting high-entropy alloys with higher critical temperatures and upper critical fields.\n4. Superconductivity and fractionalized magnetic excitations in CeCoIn5 Relevance Score: 3.8987 Authors: Pyeongjae Park, Shang-Shun Zhang, Pietro M. Bonetti, Andrey A. Podlesnyak, Daniel M. Pajerowski, Matthew B. Stone, C. Petrovic, C. Stock, Subir Sachdev, Cristian D. Batista, Andrew D. Christianson Link: http://arxiv.org/abs/2604.02481v1 Summary: For the prototypical d-wave superconductor CeCoIn₅, researchers have revealed through high-resolution inelastic neutron scattering experiments and theoretical analysis the evolution of its magnetic excitation spectrum across the superconducting transition. The experiments show that in the superconducting state, a sharp, dispersive spin resonance mode emerges alongside a broad continuum, which persists into the normal state and exhibits strong antiferromagnetic correlations. A Kondo lattice theory model based on nearly fractionalized Fermi liquid (FL*) combined with d-wave pairing successfully reproduces these key features. This model indicates that both the quasi-localized f-electron magnetic moments above the superconducting transition temperature and the spin resonance in the superconducting state originate from common gauge field dynamics, thereby unifying spin fractionalization with unconventional superconductivity and providing a new framework for understanding quantum critical phenomena in strongly correlated metals.\n5. Chiral skyrmionic superconductivity from doping a Chern Ferromagnet Relevance Score: 3.7267 Authors: Miguel Gonçalves, Kun Yang, Shi-Zeng Lin Link: http://arxiv.org/abs/2604.02298v1 Summary: By doping a Chern ferromagnet, researchers have found that chiral superconductivity can be stabilized. Using exact diagonalization and density matrix renormalization group methods, they studied the hole-doped Kane-Mele-Hubbard model (relative to one electron per unit cell). The results show that under sufficiently strong interactions and Ising spin-orbit coupling, a magnon (spin-flip excitation) binds with two holes to form a Cooper pair. This Cooper pair simultaneously possesses finite spin chirality (indicating a non-coplanar skyrmion spin texture) and chiral f-wave symmetry. The pairing and spin chirality are determined by the Chern number/polarization of the parent Chern ferromagnet. Furthermore, as the Ising spin-orbit coupling increases, the interaction between skyrmion Cooper pairs changes from repulsive to attractive, revealing an intermediate spin-orbit coupling regime where the condensation of hole-skyrmion Cooper pairs can generate chiral superconductivity. These findings provide a new microscopic mechanism for chiral superconductivity and may be relevant to the recently observed superconductivity in MoTe₂ moiré superlattices.\n6. Detection of spin- and valley-polarized states in van der Waals materials via thermoelectric and non-reciprocal transport Relevance Score: 3.6618 Authors: Oladunjoye A. Awoga, Pauli Virtanen, Tero T. Heikkilä, Stefan Ilić Link: http://arxiv.org/abs/2604.02427v1 Summary: This work predicts the generation of thermoelectric effects and current rectification in hybrid junctions composed of Ising superconductors and spin-valley polarized materials. These effects arise from the interplay between the intrinsic Ising spin-orbit coupling of the materials, the spin splitting induced by an external exchange or Zeeman field, and valley polarization. It is found that an in-plane magnetic field induces valley-odd triplet correlations in the Ising superconductor, which, when coupled with the spin-valley polarized states of the adjacent material, break electron-hole symmetry, giving rise to a thermoelectric response termed Ising thermopower and nonreciprocal current rectification. The magnitudes of these effects are modulated by the degree of spin-valley polarization, and they exhibit different symmetries upon magnetic field reversal, enabling distinction from conventional spin-splitting contributions. These results provide an experimentally feasible approach to directly detect valley-polarized states in van der Waals heterostructures—such as those composed of few-layer transition metal dichalcogenides with twisted bilayer or rhombohedral graphene—via electrical transport measurements, which is of significant importance for valleytronics and the study of interaction-driven valley-ordered states.\n7. Magnetoelectric Coupling in Nickel-Cobalt Ferrite and Lanthanum Ferrite Heterostructure Composites: Experimental Evidence and Simulation-Driven Insights Relevance Score: 3.6337 Authors: Manjeet Seth Affiliations: Guru Ghasidas Vishwavidyalaya (CU) Link: http://arxiv.org/abs/2604.01565v1 Summary: This study synthesized heterojunction composites of nickel-cobalt ferrite (NCFO) and lanthanum ferrite (LFO) via the conventional solid-state reaction method, aiming to explore the magnetoelectric coupling performance of lead-free multiferroic materials. X-ray diffraction and Raman spectroscopy confirmed the successful combination of NCFO (cubic spinel phase) and LFO (orthorhombic perovskite phase), with a notable red shift in Raman peaks as the LFO content increased, indicating tensile strain at the interface. Temperature-dependent Raman measurements revealed reversible behavior across all samples in the range of 83 to 823 K. Magnetic property measurements demonstrated both spontaneous magnetization and ferroelectric polarization in the composites. The experimental results show that the composite material exhibits a significant magnetoelectric coupling effect, which can be modulated by external electric or magnetic fields. This study provides experimental evidence and a material basis for developing lead-free, environmentally friendly magnetoelectric coupling devices such as sensors, multistate memories, and energy harvesters.\n8. Bond-density-wave orders induced by geometric frustration in the kagome metal CeRu3Si2 Relevance Score: 3.5782 Authors: Ryo Misawa, Shunsuke Kitou, Rinsuke Yamada, Xiaolong Feng, Ryota Nakano, Priya Ranjan Baral, Yuiga Nakamura, Leslie M. Schoop, Yukitoshi Motome, Taka-hisa Arima, Xiuzhen Yu, Max Hirschberger Link: http://arxiv.org/abs/2604.01691v1 Summary: In the Kagome metal CeRu3Si2, researchers have identified bond density wave (BDW) orders induced by geometric frustration through synchrotron X-ray diffraction, real-space transmission electron microscopy, and model calculations. These orders are stable above room temperature and manifest as two types of long-period superlattices: one with harmonic modulation and the other exhibiting higher-order harmonics resulting in an anharmonic structure. The key finding is that this bond modulation is sublattice-selective: the interlayer bonds of the Ru1 and Ru2 sublattices undergo sinusoidal or square-wave oscillations, while the Ru3 sublattice is modulated in the opposite direction, such that the net bond length variation on each Kagome triangle satisfies a local \u0026ldquo;zero-sum constraint,\u0026rdquo; analogous to the charge neutrality condition in frustrated antiferromagnets. By deriving a pseudospin model, the authors demonstrate that this BDW order originates from the competition between sublattice-anisotropic Coulomb repulsion and geometric frustration, with the anharmonic square-wave state becoming more stable at low temperatures due to weakened screening effects. This work establishes the first analog of geometric frustration in chemical bond systems, extending frustration physics from spin and charge to bond order, and reveals that Kagome metals can host complex, frustration-constrained ordered states above room temperature.\n9. Suppression of the tendency toward antiferromagnetic order in the Dirac semimetal SrIrO$_3$ Relevance Score: 3.4555 Authors: Xiang Li, Xiaoting Li, Jiaqi Lin, Peng Dong, Jun Li, Mary H. Upton, Yifan Jiang, Dawei Shen, Haizhong Guo, Xuerong Liu Link: http://arxiv.org/abs/2604.02140v1 Summary: The spin dynamics of the Dirac semimetal SrIrO₃ and its Sn-substituted compounds were investigated using resonant inelastic X-ray scattering (RIXS). The results reveal that, despite the absence of long-range antiferromagnetic order in the pristine paramagnetic metallic state of SrIrO₃, its magnetic excitation intensity and energy dispersion are significantly higher than those of the long-range-ordered Sn-substituted samples, and its linewidth near the antiferromagnetic instability wavevector (1/2 1/2 1/2) is extremely narrow, approaching the instrumental resolution limit, indicating the existence of anomalously long-lived magnetic excitations. Temperature-dependent measurements show that the spectral weight of this magnetic excitation increases linearly with cooling but does not diverge, suggesting that the long-range order is suppressed by factors other than thermal fluctuations. Based on the band structure, this phenomenon is attributed to the high itinerancy of topologically protected Dirac fermions, whose motion destroys the coherence of the antiferromagnetic background via a mechanism akin to Nagaoka polarons, thereby preventing a magnetic ordering transition. This finding reveals the interplay between band topology and strong electronic correlations, and suggests that topological bands can serve as a new means of modulating charge-spin entanglement.\n10. Moiré Mott correlated mosaics in twisted bilayer 1T-TaS$_2$ Relevance Score: 3.4134 Authors: Ana Vera Montoto, Jose L. Lado, Adolfo O. Fumega Link: http://arxiv.org/abs/2604.02001v1 Summary: By constructing a Hubbard model and performing noncollinear mean-field decoupling with distance-dependent interlayer hopping terms, this paper systematically investigates the electronic structure of twisted bilayer 1T-TaS₂. The moiré pattern induces spatially varying interlayer coupling, quenching local magnetic moments in A-like stacking regions (with short interlayer distances) and forming a nonmagnetic insulating phase, while L-like regions (with larger interlayer distances) retain Mott insulating characteristics, resulting in a Mott-trivial mosaic superlattice. Spectral calculations reveal a larger hybridization gap in A-like regions and a smaller Mott gap in L-like regions, with the gap exhibiting moiré modulation in real space. Additionally, applying an interlayer bias enables controllable charge transfer, dynamically tuning the degree of local correlations and even quenching them entirely. This work demonstrates that twisted 1T-TaS₂ serves as a flexible platform for engineering hybrid correlated insulating phases with spatially modulated properties.\n11. Altermagnetism and Room-Temperature Metal-to-Insulator Transition in CsCr$_2$S$_2$O Relevance Score: 3.4113 Authors: Yi Liu, Chen-Chao Xu, Jin-Ke Bao, Bai-Jiang Lv, Hao Li, Jing Li, Yi-Qiang Lin, Hua-Xun Li, Yi-Ming Lu, Xin-Yu Zhao, Wu-Zhang Yang, Zhen-Yi Zhang, Xian-Yan Chen, Wen-he Jiao, Ji-Yong Liu, Bai-Ren Zhu, Guang-Han Cao Affiliations: Zhejiang University, National Key Laboratory of Neutron Science and Technology, Chinese Academy of Engineering Physics, Nanjing University, Zhejiang Laboratory, Hangzhou Normal University, Zhejiang University of Technology, Bruker Scientific Instruments Co., Ltd Link: http://arxiv.org/abs/2604.02114v1 Summary: This study synthesizes a layered chromium-based compound, CsCr₂S₂O, which exhibits C-type antiferromagnetic order below 326 K, forming a room-temperature d-wave altermagnet. A Verwey-type metal–insulator transition occurs at 305 K, accompanied by a tetragonal-to-orthorhombic structural distortion and Cr²⁺/Cr³⁺ stripe charge ordering, while the altermagnetic character persists across the phase transition. First-principles calculations reveal spin splitting energies of approximately 0.6 eV and 0.3 eV in the metallic and insulating states, respectively. This work achieves, for the first time, the coexistence of altermagnetism and a metal–insulator transition in a single material, providing a new platform for room-temperature spintronic applications.\n12. Insulator-to-Metal Transitions Driven by Quantized Formal Polarization Mismatch Relevance Score: 3.2704 Authors: Hongsheng Pang, Lixin He Link: http://arxiv.org/abs/2604.01530v1 Summary: This paper proposes an insulator-metal (IM) transition mechanism driven by mismatch of quantized form polarization (QFP), which is a symmetry-protected bulk invariant. When a material possesses low-symmetry insulating phases and high-symmetry phases that allow different QFP values, any continuous path connecting these two phases while preserving the symmetry of the low-symmetry phase necessarily undergoes an IM transition, because QFP remains invariant under symmetry-preserving evolution with an open gap, while the high-symmetry phase requires a distinct QFP value—this mismatch can only be resolved by gap closure. Validated through first-principles calculations (HSE functional) on two representative systems, two-dimensional InPS₃ and three-dimensional CdBiO₃, the polarization and energy gap along the structural evolution path are computed, confirming the mechanism: during evolution from the low-symmetry to the high-symmetry phase, QFP remains fixed, the gap progressively closes, the system enters a metallic state, and polarization vanishes; after passing the high-symmetry phase, the gap reopens. This work establishes QFP mismatch as a general symmetry constraint for phase evolution, revealing a new pathway for symmetry-driven IM transitions in high-symmetry materials, and this mechanism enables large polarization changes and gap modulation with minimal atomic displacements.\n13. Sign-Free Evidence for a d-Wave Superfluid Stiffness Dome in the Doped Hubbard Model Relevance Score: 3.2469 Authors: Xidi Wang, H. Q. Lin Link: http://arxiv.org/abs/2604.01737v1 Summary: We construct an effective single-particle Hamiltonian K_eff from the Monte Carlo average of the matrix logarithm of the imaginary-time propagator in determinant quantum Monte Carlo, converting the multiplicative sign problem into an additive framework such that K_eff is sign-free and captures the exact correlated single-particle spectrum including all self-energy effects. Application to the doped Hubbard model (t\u0026rsquo;/t = -0.30, U/t = 4) reveals a d-wave pseudogap emerging below the calculated transition temperature T*, with strong nodal–antinodal dichotomy. Three sign-free observables provide evidence consistent with spin-fluctuation pairing: the energy gap ratio R_g \u0026gt; 1 confirms d-wave symmetry (a temperature-independent correlated band-structure property); the superfluid stiffness ρ_s forms a dome over the doping range (L=8,10,12), peaking at 5–7 times the Berezinskii-Kosterlitz-Thouless threshold; and the antiferromagnetic structure factor S(π,π) remains approximately flat with doping, indicating that the dome originates from the Fermi-surface geometry response to uniform spin-fluctuation glue. The pseudogap increases monotonically as half-filling is approached, while ρ_s forms a dome, reproducing the Uemura relation between superfluid density and Tc in cuprates. Vertex corrections still require further quantification.\n14. Strong nonlinear thermoelectricity generation and close-to-Carnot efficient heat engines in Superconductor-Insulator-2D electron gas junctions Relevance Score: 3.0934 Authors: Leonardo Lucchesi, Federico Paolucci Link: http://arxiv.org/abs/2604.02123v1 Summary: This paper investigates a novel superconductor-insulator-two-dimensional electron gas tunnel junction (SISm) that achieves strong thermoelectric effects through nonlinear mechanisms. By simulating the parameter space of this junction, it is found that different operating regimes exhibit unique thermoelectric properties: the open-circuit Seebeck potential can reach 6.75Δ₀ (approximately 1.4 mV in aluminum), with an extremely large nonlinear Seebeck coefficient; when operating as a heat engine, its efficiency reaches up to 0.96η_C, approaching the Carnot efficiency, setting a record for solid-state device models. This junction leverages the band structure of the two-dimensional electron gas to explicitly break electron-hole symmetry, generating thermoelectric effects via quasiparticle tunneling, without the need to suppress supercurrents or employ complex ferromagnetic insulator processes. Different parameter regimes enable applications such as bistability (useful for thermal memory) and strong temperature response (for thermometry or radiation detection). Its performance surpasses that of similar junctions, and it can be fabricated using standard two-dimensional electron gas processes, significantly reducing manufacturing difficulty.\n15. Chiral Superconductivity in Periodically Driven Altermagnet/Superconductor Heterostructures Relevance Score: 3.0756 Authors: Xiaolin Wan, Zheng Qin, Fangyang Zhan, Junjie Zeng, Dong-Hui Xu, Rui Wang Link: http://arxiv.org/abs/2604.01596v1 Summary: This study proposes the application of elliptically polarized light driving in an alternating magnet/superconductor heterostructure to realize chiral topological superconductivity via Floquet engineering. Through calculations based on the Bogoliubov–de Gennes Hamiltonian and Chern numbers, it is found that for s-wave pairing, the system can transition from a trivial superconducting phase to a strong topological superconducting phase with an odd Chern number; for mixed s+d-wave pairing, the system can enter a higher-order chiral topological superconducting phase with a Chern number as high as four under the modulation of light amplitude and alternating magnetic strength, accompanied by multiple chiral Majorana edge modes. These exotic phases originate from the synergistic interplay of alternating magnetism, superconducting pairing, and periodic light fields. This work provides a universal optically driven platform for exploring and tuning high-Chern-number chiral topological superconducting states.\n16. Bond-Length-Driven Magnetic Transition in Quasi-One-Dimensional CrSb$X_3$ ($X$=S, Se) Relevance Score: 3.0565 Authors: Kang Lee, Hong-Suk Choi, K. -W. Lee Link: http://arxiv.org/abs/2604.01810v1 Summary: This study systematically investigates the magnetic ground state of quasi-one-dimensional insulators CrSbX₃ (X = S, Se) using first-principles calculations. Without introducing explicit Coulomb correlation U, the all-electron full-potential method yields a band gap consistent with experimental observations, indicating that the insulating nature can be attributed to band insulating characteristics rather than strong correlation effects. The key finding is that the magnetic order is highly sensitive to the Cr-Cr bond length d_Cr-Cr: elongating the bond length induces a first-order phase transition from antiferromagnetic to ferromagnetic, with a critical distance of approximately 3.53 Å. CrSbS₃, with a shorter bond length, lies near the phase transition boundary and exhibits an antiferromagnetic order, whereas CrSbSe₃, with a longer bond length, shows a stable ferromagnetic order, consistent with experiments. Exchange interaction analysis reveals that this phase transition is primarily driven by the sign reversal of the nearest-neighbor intrachain superexchange J₁ (switching from antiferromagnetic to ferromagnetic coupling as the bond length increases), while the direct intrachain exchange J₂ remains ferromagnetic and varies smoothly. This competitive mechanism manifests Bethe-Slater behavior in quasi-one-dimensional transition metal systems, providing critical insights into the magnetic origin of related compounds.\n17. Transport and Temperature 1: Exact spectrum and resistivity for the one-dimensional infinite-$U$ Hubbard model Relevance Score: 3.0530 Authors: Shuo Liu, Yuhao Ma, Hitesh J. Changlani, Philip W. Phillips, B. Andrei Bernevig Affiliations: Donostia International Physics Center (DIPC), Princeton University, University of Illinois at Urbana-Champaign, National High Magnetic Field Laboratory, IKERBASQUE, Florida State University Link: http://arxiv.org/abs/2604.02426v1 Summary: In the Hubbard model under the one-dimensional infinite interaction limit, researchers have, for the first time, derived a closed-form analytical expression for the charge Drude weight at arbitrary temperatures in the dilute doping regime (fixed number of holes) by constructing an exact explicit energy spectrum beyond the Bethe ansatz. In this limit, the current operator commutes with the Hamiltonian, causing the regular contribution to vanish and making the DC conductivity entirely determined by the Drude weight. The study reveals a linear temperature correction to the Drude weight at low temperature scales, which, after regularization (broadening the Drude peak), corresponds to an effective linear temperature resistivity. This result analytically uncovers a possible origin of the strange metal linear resistivity in strongly correlated two-dimensional systems and indicates that when the doping density is finite, the temperature dependence of resistivity transitions from linear to quadratic, highlighting the importance of exact analytical solutions for understanding small-scale numerical simulation results.\n18. Loop-level surrogate modeling of dopant-distribution effects in Ba(Zr,Ti)O$_3$ Relevance Score: 3.0407 Authors: Heiko Röthl, Elke Kraker, Julien Magnien, Manfred Mücke, Florian Mayer Affiliations: Materials Center Leoben Forschung GmbH Link: http://arxiv.org/abs/2604.02325v1 Summary: This study proposes an accelerated materials design workflow to systematically investigate the effect of the spatial distribution of zirconium (Zr) in barium titanate (BaTiO₃) on field-driven responses. The researchers generated continuous distribution configurations incorporating typical nanoscale patterns such as layers, rods, dots, and sheets using a parameterized description model, and computed polarization-electric field and strain-field hysteresis loops via first-principles parameterized effective Hamiltonian molecular dynamics. Subsequently, a conditional autoencoder surrogate model was trained to directly predict full hysteresis loops from distribution parameters, dramatically improving screening efficiency (reducing the time required to simulate approximately 10⁵ loops from millions of core hours to minutes). Based on the predicted loop database, the researchers screened for multifunctional objectives including energy storage performance, electromechanical response, and switching behavior, discovering that dopant distribution serves as an independent tuning parameter: layered, vertical sheet-like, and nanoscopic sheet-like distributions dominate different performance regimes. This work demonstrates that predicting full-field response curves enables loop-derived multi-objective design and rapid screening in doped ferroelectrics.\n19. Atomistic theory of the phonon angular momentum Hall effect Relevance Score: 3.0394 Authors: Daniel A. Bustamante Lopez, Verena Brehm, Dominik M. Juraschek Link: http://arxiv.org/abs/2604.01899v1 Summary: Based on the resonant approximation and coupling to a Langevin heat bath, this paper establishes an atomic theory of the phonon angular momentum Hall effect in finite lattices under non-equilibrium conditions. By deriving real-space analytical expressions, we obtain the phonon angular momentum current density, local accumulation, and conductivity tensor, revealing that the effect originates from the mixing of polarized vibrational modes induced by a temperature gradient, without requiring lattice chirality or inversion symmetry breaking. In minimal two-dimensional square and honeycomb lattice models, a longitudinal temperature gradient successfully drives a transverse phonon angular momentum current and produces characteristic angular momentum accumulation at the sample boundaries. Using first-principles force constants, this edge accumulation is further verified in real materials such as graphene, silicon, magnesium oxide, and barium titanate, with magnitudes on the order of 10⁻⁶–10⁻⁵ ħ per atom. The results demonstrate that the phonon angular momentum Hall effect is a universal non-equilibrium response in crystals, and the proposed framework can be widely applied for quantitative predictions across all materials.\n20. Terahertz optical activity near crystal field transitions of Tm3+ ions in magnetoelectric alumoborates Relevance Score: 3.0265 Authors: A. M. Kuzmenko, V. Yu. Ivanov, S. V. Garnov, A. Shuvaev, A. Pimenov, K. N. Boldyrev, I. A. Gudim, A. A. Mukhin Affiliations: Institute of Spectroscopy of the Russian Academy of Sciences, Siberian Branch of the Russian Academy of Sciences, Prokhorov General Physics Institute of the Russian Academy of Sciences, Vienna University of Technology Link: http://arxiv.org/abs/2604.02193v1 Summary: Using terahertz transmission spectroscopy, crystal field excitations within the ground state multiplet ³H₆ of Tm³⁺ ions were investigated in the magnetoelectric material TmAl₃(BO₃)₄ and the lightly doped Tm₀.₀₅Yb₀.₁Y₀.₈₅Al₃(BO₃)₄. These excitations are identified as magnetic dipole transitions from the ground state singlet A₁ to the next excited doublet E, which is split by the crystal field of D₃ symmetry. Clear fine structures observed at low temperatures exhibit distinct behaviors in the pure Tm borate and the lightly doped sample, consistent with differences in local crystal field distortions. Significant natural optical activity is found near the crystal field transitions, resulting in a maximum polarization rotation of up to 25 degrees. This optical activity can be quantitatively described by contributions from magnetic and electric dipole transitions to the dynamic magnetoelectric response, combined with a classification of local distortions.\n","permalink":"https://nickelates.uk/en/posts/2026-04-02-arxiv-daily/","summary":"\u003cblockquote\u003e\n\u003cp\u003e\u003cstrong\u003eDaily Overview\u003c/strong\u003e:\nToday\u0026rsquo;s highlight focuses on the in-depth understanding of the electronic structure of hybrid Ruddlesden-Popper nickelates. [1] Using resonant inelastic X-ray scattering, a direct comparison of the electronic and magnetic excitations between trilayer La₄Ni₃O₁₀ and bilayer La₃Ni₂O₇ was conducted. It was found that the trilayer compound exhibits weaker electronic correlations and interlayer magnetic exchange, which explains why its superconducting transition temperature of approximately 30 K is significantly lower than that of the bilayer (~80 K), establishing interlayer magnetic coupling and electronic correlations as key parameters. [2] First-principles calculations revealed the strain tuning mechanism in La₃Ni₂O₇ thin films, demonstrating that biaxial compressive strain enhances the Jahn-Teller splitting energy as the core microscopic factor for optimizing superconductivity. The calculated results are consistent with experiments. These works provide important experimental and theoretical evidence for understanding the superconducting pairing mechanism in layered nickelates.\n\u003cstrong\u003earXiv submission processing window\u003c/strong\u003e: 2026-04-01 22:40 to 2026-04-02 19:26 UTC.\u003c/p\u003e","title":"arXiv Daily: nickelate superconductors 2026-04-02"},{"content":" Daily Overview: The highlights of today\u0026rsquo;s work focus on an in-depth exploration of electronic structures and pairing symmetries in the field of nickel-based superconductivity. In [1], a theoretical design based on DFT+DMFT proposes that the cobalt-based layered compound La₄Co₂NiO₈Cl₂ exhibits strongly correlated electronic characteristics highly similar to those of superconducting La₄Ni₃O₁₀, including non-Fermi liquid behavior in the outer Co orbitals and flat bands near the M point, providing a theoretical candidate for the search of new cobalt-based high-temperature superconductors. In [2], researchers systematically calculated the electronic Raman response using a two-orbital bilayer model, indicating that Raman scattering can effectively distinguish between s±-wave and nodal d-wave pairing symmetries in bilayer nickelate La₃Ni₂O₇. In particular, the low-energy power-law behavior can clearly identify nodal states, offering a powerful means for experimentally determining the superconducting gap structure. Furthermore, [3] reports the observation of superconductivity at 16.3 K in the altermagnetic candidate material Na₂₋ₓV₂Se₂O. Its layered structure serves as a structural bridge between cuprates/nickelates and iron-based superconductors, expanding the correlated superconducting material system and providing valuable insights for understanding unconventional superconducting mechanisms. arXiv submission processing window: 2026-03-31 22:24 to 2026-04-01 17:59 UTC.\n1. Electronic structure and correlation of La$_4$Co$_2$NiO$_8$Cl$_2$: a theoretical proposal for a La$_4$Ni$_3$O$_{10}$-like high-temperature superconductor Relevance Score: 5.5717 Authors: Si-Yong Jia, Jing-Xuan Wang, Jian-Hong She, Rong-Qiang He, Zhong-Yi Lu Link: http://arxiv.org/abs/2604.01223v1 Summary: Building on the discovery of high-pressure superconductivity in trilayer nickelate La₄Ni₃O₁₀, this study employed density functional theory combined with dynamical mean-field theory (DFT+DMFT) to design and calculate the cobalt-based analogue La₄Co₂NiO₈Cl₂. By substituting the inner-layer Co in the high-pressure phase La₄Co₃O₁₀ with Ni and incorporating Cl to achieve electron doping, this compound acquires a crystal structure and strongly correlated electronic characteristics similar to those of superconducting La₄Ni₃O₁₀: the outer-layer Co orbitals exhibit strong effective mass enhancement and non-Fermi liquid behavior, while the inner-layer Ni behaves as a weakly correlated Fermi liquid; a flat band near the Fermi level originating from the outer-layer Co orbitals emerges around the M point; and there is pronounced orbital selectivity as well as local spin fluctuations mixing high-spin and low-spin states. These features are in close agreement with the key electronic states of La₄Ni₃O₁₀, indicating that La₄Co₂NiO₈Cl₂ is a promising candidate for realizing high-temperature superconductivity in cobalt-based layered compounds, providing a theoretical basis for subsequent experimental exploration.\n2. Detecting pairing symmetry of bilayer nickelates using electronic Raman scattering Relevance Score: 5.1912 Authors: Jun Zhan, Matías Bejas, Andreas P. Schnyder, Andrés Greco, Xianxin Wu, Jiangping Hu Link: http://arxiv.org/abs/2604.01027v1 Summary: Using a two-orbital bilayer model, this study systematically calculates the electronic Raman response in different Raman channels via both multiorbital and band-sum methods to distinguish the controversial pairing symmetry in the bilayer nickelate superconductor La₃Ni₂O₇. By comparing the Raman susceptibilities obtained from the multiorbital approach and the band-sum approximation, it is found that the Raman response can effectively differentiate various pairing symmetries and identify the Fermi-pocket-dependent gap sizes in fully gapped and nodal superconducting states. Specifically, nodal dₓ²⁻ᵧ²/dₓᵧ-wave pairing exhibits robust power-law behavior at low energies, distinctly different from fully gapped pairing; for s±-wave pairing, detailed gap anisotropy on the β pocket can be determined. The study also emphasizes the crucial role of multiorbital effects in shaping the Raman spectra, and points out that electronic Raman scattering, as a symmetry-resolving probe, provides a powerful means to determine the superconducting gap structure of unconventional superconductors, offering significant experimental implications for understanding the superconducting mechanism of bilayer nickelates.\n3. Emergent superconductivity at 16.3 K in an altermagnetic candidate Na$_{2-x}$V$_2$Se$_2$O with broken inversion symmetry Relevance Score: 4.3922 Authors: Y. Sun, Z. Yin, T. Zhang, L. Wang, B. Ruan, Y. Huang, J. He, W. Zhu, M. Ma, J. Bai, J. Cheng, Q. Dong, C. Li, P. Liu, Q. Liu, C. Zhang, G. Chen Affiliations: Shaanxi Normal University, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Chongqing University, Nanyang Normal University Link: http://arxiv.org/abs/2604.00838v1 Summary: By synthesizing a novel layered vanadium oxyselenide compound Na₂₋ₓV₂Se₂O, this study successfully observed superconductivity with a transition temperature of approximately 16.3 K. The material crystallizes in an orthorhombic space group Ammm, characterized by [V₂Se₂O] layers separated by double layers of Na⁺ ions, with the sodium sites only half-occupied, leading to inversion symmetry breaking. This compound exhibits a spin-density-wave (SDW)-like anomaly at around 85 K and shows quasi-two-dimensional electronic properties along with Dirac band dispersion near the Fermi level. Although the superconducting volume fraction of the current polycrystalline sample is only about 5%, this is the first observation of superconductivity at relatively high temperatures in candidate altermagnetic materials. This discovery not only opens a new route to exploring superconductivity in altermagnets but also provides a unique platform for investigating novel physical phenomena such as topological states, van Hove singularities, and finite-momentum superconductivity. Moreover, serving as a structural bridge between cuprate/nickelate and iron-based high-temperature superconductors, it is expected to expand the family of layered superconducting materials and enhance the understanding of unconventional superconductivity mechanisms.\n4. Directional-dependent Berezinskii-Kosterlitz-Thouless transition at EuO/KTaO$_3$(111) interfaces Relevance Score: 4.2430 Authors: Zongyao Huang, Zhengjie Wang, Xiangyu Hua, Huiyu Wang, Zhaohang Li, Shihao Liu, Zhiwei Wang, Feixiong Quan, Zhen Wang, Jing Tao, James Jun He, Ziji Xiang, Xianhui Chen Link: http://arxiv.org/abs/2604.00608v1 Summary: At the (111)-oriented interface between KTaO₃ and ferromagnetic EuO, a two-dimensional superconducting state exhibits a Berezinskii-Kosterlitz-Thouless (BKT) transition that depends on the direction of the in-plane bias current. When the current is applied along one of the [11(\\bar{2})] crystallographic axes of KTaO₃, the critical temperature T_BKT reaches its maximum, revealing a spontaneous breaking of the threefold rotational lattice symmetry. This directional dependence is consistently reflected in the nonreciprocal signals arising from superconducting fluctuations. Through carefully designed transport experiments—including L-shaped Hall bars and triple-beam devices—the researchers ruled out geometric effects and verified that the anisotropy in T_BKT does not originate from current-induced non-equilibrium effects. They attribute the phenomenon to interfacial phase separation, where a phase with a higher T_BKT self-organizes into quasi-one-dimensional textures extending along a specific [11(\\bar{2})] direction. These findings extend beyond conventional BKT physics and point toward an exotic state of matter emerging at the superconducting interface under ferromagnetic proximity.\n5. Uniaxial Compression-Induced Anisotropy and Electronic Dimensionality in the Iron-Based Superconductor FeSe Relevance Score: 4.1610 Authors: Alexy Bertrand, Masaki Mito, Kazuma Nakamura, Mahmoud Abdel-Hafiez Link: http://arxiv.org/abs/2604.01062v2 Summary: This study systematically investigates the evolution of the superconducting transition temperature (Tc) in the iron-based superconductor FeSe under three compression modes: in-plane, out-of-plane, and hydrostatic pressure. Experimental results show that at pressures below 0.6 GPa, Tc increases under all compression modes, consistent with the suppression of nematic order. However, once nematicity completely vanishes, Tc exhibits a pronounced direction dependence: out-of-plane compression, similar to hydrostatic pressure, leads to a sharp increase in Tc, while in-plane compression suppresses superconductivity. First-principles calculations reveal that in-plane compression causes the band formed by the hybridization of Se pz orbitals and Fe dx²-y² orbitals to cross the Fermi level along the Γ-Z direction, generating an additional metallic band that transforms the electronic structure from quasi-two-dimensional to three-dimensional, which likely corresponds to a Lifshitz-type topological change of the Fermi surface. Combining experimental and computational results, this study uncovers the strong anisotropy of FeSe superconductivity under uniaxial compression, rooted in changes to the structural and electronic dimensionality—maintaining the two-dimensional character of the electronic structure is crucial for sustaining high Tc, while the extra three-dimensional conduction channels induced by in-plane compression disrupt this condition. This work highlights the importance of uniaxial compression experiments in understanding the superconducting mechanism of the strongly correlated system FeSe.\n6. Microscopic Theory of Superionic Phase Transitions: Nonadiabatic Dynamics and Many-Body Effects Relevance Score: 3.7764 Authors: Jiaming Hu, Zhichao Guo, Jingyi Liang, Bartomeu Monserrat Link: http://arxiv.org/abs/2604.00665v1 Summary: This study proposes a unified theoretical framework to describe solid-state ion conduction, beginning with a review of the limitations of traditional approximation methods and then constructing a general lattice model applicable to both normal ionic conductors and superionic conductors. By incorporating the nonadiabatic cooperative jumping mechanism and many-body Coulomb interactions into a self-consistent mean-field scheme, the paper explicitly identifies these two effects as the fundamental driving forces for type I and type II superionic phase transitions, respectively: nonadiabatic cooperative jumping drives first-order phase transitions in type I, while many-body Coulomb interactions drive second-order phase transitions in type II. The model successfully reproduces key experimental observations, such as abrupt or continuous changes in conductivity, and systematically compares the similarities and differences between the two types of phase transitions within a unified framework. The conclusion indicates that this work provides a deep microscopic understanding of superionic phase transitions and offers theoretical guidance for the design and optimization of advanced solid-state ionic conductors.\n7. Spatially modulated morphotropic phase boundaries in a compressively strained multiferroic thin film Relevance Score: 3.5155 Authors: Ting-Ran Liu, Xiangwei Guo, Sajid Husain, Maya Ramesh, Pushpendra Gupta, Darrell Schlom, Ramamoorthy Ramesh, Yu-Tsun Shao Affiliations: Cornell University, University of Michigan, University of Southern California, University of California, Berkeley Link: http://arxiv.org/abs/2604.00288v1 Summary: Using multimodal diffraction electron microscopy, multislice electron ptychography, and electron backscatter diffraction, the compression-strain-induced coexisting rhombohedral (R\u0026rsquo;, MA) and tetragonal (T\u0026rsquo;, MC) phases forming a morphotropic phase boundary (MPB) in a 60 nm thick BiFeO₃ film grown on a LaAlO₃ substrate were characterized at multiscale levels. Two types of phase interfaces were observed: one is a flat MPB line extending over 1 mm with a quasi-period of approximately 20 μm, and the other is a novel sawtooth-like interface composed of alternating R\u0026rsquo;/R\u0026rsquo; and T\u0026rsquo;/T\u0026rsquo; twin domain zones. Atomic-scale imaging confirmed continuous polarization rotation at the MPB, with out-of-plane strain variations exceeding 15%, and revealed lattice dislocations of about 1.5° at the sawtooth interface, while dislocations in the MPB region were greater than 2.5°. Phase-field simulations indicated that the sawtooth interface originates from the balance between Landau energy and elastic energy. This discovery elucidates the self-organization mechanism of ordered phase interfaces under strain modulation, providing a new pathway for tuning their multifunctional properties via mesoscale strain engineering.\n8. Metallic d-wave altermagnetism in WFeB: a platform for electrically switchable perpendicular spin-splitter response Relevance Score: 3.5020 Authors: Eranga H. Gamage, Zhen Zhang, Subhadip Pradhan, Ajay Kumar, David R. Ramgern, V. Ovidiu Garlea, Yaroslav Mudryk, Saeed Kamali, Douglas Warnberg, Kirill D. Belashchenko, Vladimir Antropov, Kirill Kovnir Affiliations: Oak Ridge National Laboratory, Iowa State University, University of Nebraska-Lincoln, University of Tennessee Space Institute, Ames National Laboratory, Middle Tennessee State University Link: http://arxiv.org/abs/2604.00325v1 Summary: We successfully synthesized WFeB and confirmed it as a metallic d-wave altermagnet belonging to the broader TiNiSi-type family through neutron diffraction, Mössbauer spectroscopy, and magnetic measurements. First-principles calculations reveal that its magnetic ground state exhibits an alternating magnetic order, with an electronic structure featuring a non-relativistic spin splitting of approximately 100 meV near the Fermi level. Although the magnitude of the band splitting is modest, it can generate significant spin-split transport effects, demonstrating that even moderate band splitting enables efficient spin current generation. Symmetry analysis further indicates that films with specific orientations allow deterministic switching of the Néel vector via current-induced staggered torques, thereby electrically controlling the perpendicular spin-splitting response. These results establish WFeB and related TiNiSi-type antiferromagnets as an electrically switchable charge-to-spin conversion platform based on altermagnetic symmetry.\n9. Revealing buried ferroelectric topologies by depth-resolved electron diffraction imaging Relevance Score: 3.4874 Authors: Ting-Ran Liu, Koushik Jagadish, Xiangwei Guo, Maya Ramesh, Peter Meisenheimer, Harish Kumarasubramanian, Sajid Husain, Ann V. Ngo, Amir Avishai, Jayakanth Ravichandran, Darrell G. Schlom, Ramamoorthy Ramesh, Yu-Tsun Shao Affiliations: Cornell University, University of Michigan, University of Southern California, University of California, Berkeley, University of Wisconsin-Madison Link: http://arxiv.org/abs/2604.00483v1 Summary: This study proposes a depth-resolved electron diffraction imaging (DREDI) method based on scanning electron microscopy, enabling non-destructive polarization mapping with lateral resolution \u0026lt;50 nm and depth sensitivity \u0026lt;10 nm within sub-second timescales. By dynamically adjusting the electron beam energy (2–15 kV) to probe different depths, continuous polarization imaging spanning six orders of magnitude from nanometers to millimeters is achieved for the first time. In a 30 nm epitaxial BiFeO₃ thin film, DREDI reveals hidden three-dimensional polar topological evolution: regular 71° stripe domains at the surface, which transform into quadruple flux-closure vortices in the interior, and then split into asymmetric triple vertex structures near the bottom interface. Cross-sectional multiscale electron ptychography and phase-field simulations confirm that these buried configurations originate from strain heterogeneity and ferroelastic twinning in the SrRuO₃ electrode. Large-area analysis further demonstrates that such vertex-like defects form mesoscopic percolation networks above a critical scale of 4 μm. DREDI provides a new pathway for real-time, volumetric investigation of buried topological structures in ferroelectric nanomaterials.\n10. Excitations across the equilibrium and photoinduced `hidden\u0026rsquo; states of magnetoresistive manganites Relevance Score: 3.4763 Authors: Shiyu Fan, Feng Jin, Taehun Kim, Umesh Kumar, Zixun Zhang, Vivek Bhartiya, Jiemin Li, Brandon Yalin, Yanhong Gu, Mingqiang Gu, Wen Hu, Claudio Mazzoli, G. Lawrence Carr, Osor S. Barišić, Andrey S. Mishchenko, Valentina Bisogni, Sobhit Singh, Wenbin Wu, Jonathan Pelliciari Link: http://arxiv.org/abs/2604.00991v1 Summary: This study systematically compares excitations in the giant magnetoresistive manganite La₂/₃Ca₁/₃MnO₃ across its thermodynamic equilibrium phases (ferromagnetic metallic, antiferromagnetic insulating, and paramagnetic insulating) and a photoinduced long-lived \u0026ldquo;hidden\u0026rdquo; phase by combining near-infrared ultrafast photoexcitation (1030 nm, 250 fs pulses), in situ transport measurements, X-ray absorption spectroscopy, and resonant inelastic X-ray scattering. In the thermodynamic regime, an exponential correlation between polaron excitation and resistivity is experimentally established, confirming the system lies in the strong-coupling regime of the Holstein model. Upon exciting the antiferromagnetic insulating phase, a long-lived photoinduced phase absent in the equilibrium phase diagram is discovered, characterized by a significant softening of polaron excitations, partial suppression of Jahn-Teller distortions, and nearly unchanged Jahn-Teller active phonons, indicating that this state is not a direct transition to a metallic phase but rather a partially melted polaron state. By varying temperature, epitaxial strain, and photoexcitation fluence, a polaron phase diagram is constructed, revealing distinct spectroscopic fingerprints of each phase. This laser-resonant inelastic X-ray scattering approach provides a general platform for exploring photoinduced \u0026ldquo;hidden\u0026rdquo; phases in quantum materials under non-stroboscopic conditions.\n11. Contemporary Insights into Electronic Structure and Microscopic Transport in Nodal-Line Semimetals Relevance Score: 3.4692 Authors: Ashutosh S. Wadge, Pardeep K. Tanwar, Giuseppe Cuono, Carmine Autieri Link: http://arxiv.org/abs/2604.00596v2 Summary: Nodal line semimetals are a class of topological semimetals whose band crossings extend along one-dimensional manifolds in momentum space—such as closed loops, chains, or straight lines—rather than at discrete points. The stability of these nodes depends on crystal symmetries (e.g., mirror, spin-rotation, and nonsymmorphic operations), giving rise to unique topological invariants and surface states, such as drumhead-like surface states. This review summarizes the theoretical framework and experimental realizations of nodal line semimetals, with a focus on symmetry protection and the consequences of symmetry breaking. It discusses the classification of nodal line structures (types A, B, C, and types I/II/III), their evolution into other topological phases, and their signatures in electronic structure measurements (especially angle-resolved photoemission spectroscopy) and transport phenomena. By integrating symmetry analysis, band topology, and experimental observations, this review clarifies the connections among topology, magnetism, and measurable electronic responses, highlighting that nodal line semimetals exhibit rich physics in correlation-driven instabilities, anomalous magnetotransport, and quantum oscillations, and serve as a versatile platform for next-generation topological electronic functional devices and novel quantum phenomena beyond conventional frameworks.\n12. Magnetoelectric Control of Toroidal Moment in Ferroaxial Crystal PbMn$_{2}$Ni$_{6}$Te$_{3}$O$_{18}$ Relevance Score: 3.4496 Authors: Shungo Aoyagi, Shunsuke Kitou, Taka-hisa Arima, Yusuke Tokunaga Affiliations: University of Tokyo Link: http://arxiv.org/abs/2604.00526v1 Summary: By applying electric and magnetic fields in different configurations to the ferroaxial crystal PbMn₂Ni₆Te₃O₁₈, control over the orientation of the magnetic toroidal moment was achieved. The direction-dependent dichroism technique was successfully employed to visualize magnetic toroidal domains, confirming the intrinsic coupling among the magnetic toroidal moment, the crystal ferroaxial moment, and the magnetoelectric monopole. The experiment demonstrated for the first time a pure toroidal moment polarization reversal without quadrupolar contributions, and a significant directional dichroism signal was observed. This work not only provides an effective approach for manipulating the magnetic toroidal moment but also opens up new methods for studying ferroaxial ordering and multipolar coupling phenomena.\n13. Improving YBa$_2$Cu$_3$O$_{7-δ}$ annealing times through a combining-temperatures route Relevance Score: 3.4439 Authors: R. F. Luccas, L. Gallo Affiliations: CONICET-UNR, Universidad Nacional de Rosario Link: http://arxiv.org/abs/2604.00762v1 Summary: This study systematically measured the mass variation of fully deoxygenated YBa₂Cu₃O₇₋δ (YBCO) powder during isothermal oxidation at temperatures ranging from 300 °C to 800 °C, revealing that both the oxidation kinetics and the final oxygen saturation level are strongly temperature-dependent: oxidation proceeds rapidly at high temperatures but yields a low final oxygen content (high δ value), whereas low temperatures lead to slower oxidation yet achieve a more favorable oxygen saturation state (low δ value). Based on these findings, a strategy combining multiple oxidation temperatures is proposed to optimize overall processing time and the final δ value. Comparative experiments using a two-step oxidation protocol—first at a high temperature (691 °C) followed by a low temperature (394 °C)—demonstrated a reduction in oxidation time by approximately 30% when reaching δ \u0026lt; 0.1 and by approximately 60% when reaching δ ≈ 0.12. Given that the grain size of the powder used is comparable to the typical thickness of superconducting tapes, these results have direct practical implications for industrial applications.\n14. Magnetoelastic instabilities in kagome antiferromagnet Mn3-xGa Relevance Score: 3.3441 Authors: Linxuan Song, Feng Zhou, Guilin Lu, Liang Yao, Xuekui Xi, Yong-Chang Lau, Youguo Shi, Wenhong Wang Affiliations: Chinese Academy of Sciences, University of Chinese Academy of Sciences, Tiangong University Link: http://arxiv.org/abs/2604.00482v1 Summary: This paper systematically investigates the structural, magnetic, and transport properties of hexagonal Mn₃₋ₓGa alloys, revealing a series of compositionally tuned novel phenomena. By adjusting the Mn concentration, it is found that Mn-deficient samples exhibit volume compensation behavior akin to zero thermal expansion, while Mn-rich samples undergo a magnetoelastically driven field-assisted structural phase transition. These lattice instabilities are accompanied by correlated magnetic and transport anomalies, including metamagnetic transitions, negative magnetoresistance, and sign reversal of the anomalous Hall effect. First-principles calculations indicate that the Hall sign reversal originates from crystal symmetry breaking rather than simple magnetic moment reorientation. These results establish composition as a critical parameter for controlling magnetoelastic coupling in hexagonal Mn₃₋ₓGa, providing a unified framework for tuning structural, magnetic, and topological transport properties in kagome antiferromagnets, while reconciling conflicting observations in previous experiments.\n15. Robust $d$-wave altermagnetism in $\\mathrm{RbCr_2Se_2O}$ Relevance Score: 3.3231 Authors: San-Dong Guo Link: http://arxiv.org/abs/2604.00412v2 Summary: First-principles calculations predict that experimentally synthesized RbCr₂Se₂O is a robust d-wave altermagnetic metal, where the energy difference between the C-type and G-type antiferromagnetic configurations is significantly larger than that of other compounds in the same family, and this energy difference is insensitive to both electronic correlation strength and van der Waals interactions. Under in-plane uniaxial strain, the C-type configuration can generate a net total magnetic moment through the direct piezomagnetic effect (e.g., a magnetic moment of 0.39 μB under 3% compression), while the G-type configuration always retains zero total magnetic moment, thereby providing an experimental strategy to distinguish between apparent and hidden altermagnetism. This material is structurally similar to KV₂Se₂O and Rb₁₋δV₂Te₂O, all being d-wave altermagnets, and the findings hold universally for the XCr₂Y₂O (X = K, Rb, Cs; Y = S, Se, Te) family, further expanding the altermagnetic material family.\n16. Radio-Frequency-Driven Reshaping of the Mesoscale Charge-Density-Wave Landscape in 1T-TaS2 Thin-Film Devices Relevance Score: 3.2399 Authors: Maedeh Taheri, Zahra Ebrahim Nataj, Nick Sesing, Topojit Debnath, Tina T. Salguero, Roger K. Lake, Alexander A. Balandin Affiliations: University of California, Los Angeles, University of California, Riverside, University of Georgia Link: http://arxiv.org/abs/2604.00463v1 Summary: Radio-frequency (RF) driving directly reshapes the mesoscopic charge density wave (CDW) landscape in quasi-two-dimensional 1T-TaS2 thin films. Under combined RF and DC biasing, the hysteresis current–voltage characteristics associated with the nearly commensurate–incommensurate transition are strongly altered, exhibiting RF-driven collapse, branching, and multi-step features that depend on frequency and drive amplitude. In situ Raman measurements reveal enhanced intensity and narrowed linewidth of low-frequency CDW phonon modes, consistent with reduced dephasing and increased coherence of the periodic lattice distortion under RF driving. By combining an overdamped time-dependent Ginzburg–Landau description for the commensurate CDW with a morphological percolation resistance–capacitance transport model, simulations show that oscillatory driving anneals frustrated domain configurations, reduces domain wall density, and reorganizes the misfit network, while the transport model reproduces the resulting hysteresis, avalanche-like pathways, and RF-induced conductance steps. RF driving thus offers an effective route to control collective electron–phonon order and access metastable transport states in 1T-TaS2, with implications for reconfigurable RF electronics, memory, and unconventional computing based on correlated materials.\n17. Andreev-enhanced conductance quantization and gate-tunable induced superconducting gap in germanium Relevance Score: 3.2194 Authors: Elyjah Kiyooka, Chotivut Tangchingchai, Gonzalo Troncoso Fernandez-Bada, Boris Brun-Barriere, Simon Zihlmann, Romain Maurand, Francois Lefloch, Vivien Schmitt, Jean-Michel Hartmann, Manuel Houzet, Silvano De Franceschi Link: http://arxiv.org/abs/2604.00755v1 Summary: In Ge/SiGe quantum well heterostructures, the research team performed low-temperature transport measurements on high-mobility two-dimensional hole gases using split-gate quantum point contacts (QPCs) in proximity to aluminum superconducting contacts. Clear conductance quantization was observed (at least four plateaus), and Andreev reflection enhanced the conductance steps at zero magnetic field by approximately 40% compared to the normal state (with an out-of-plane magnetic field of 100 mT), in excellent agreement with the theoretical prediction for an interface transmission probability of 0.88. Furthermore, by tuning the QPC to the tunneling regime, the existence of a proximity-induced superconducting gap was directly demonstrated through local density of states spectroscopy, and this gap size was found to be continuously tunable by adjusting the carrier density of the two-dimensional hole gas via gate voltage. This work provides clear experimental evidence for quantum phenomena in superconductor-semiconductor hybrid systems under ballistic transport conditions.\n18. Nonreciprocal spin waves of helical magnetization states in CoFeB/NiFe bilayers Relevance Score: 3.1810 Authors: Claudia Negrete, Omar J. Suarez, Attila Kákay, Jorge A. Otálora Link: http://arxiv.org/abs/2604.00922v1 Summary: This study systematically investigates the nonreciprocal spin wave characteristics, particularly the frequency shift, of helical magnetic equilibrium states in CoFeB/NiFe bilayers by extending the dynamic matrix formalism to arbitrary non-collinear configurations along the thickness direction of heterogeneous multilayers. The results show that the frequency shift originates from distinct spin wave mode profiles along the bilayer thickness for counter-propagating modes at the same wavevector, leading to combined contributions from dynamic dipolar interactions and interlayer exchange interactions. Contrary to recent literature attributing the frequency shift solely to dipolar interactions, this work reveals that interlayer exchange interactions play a critical role, an effect previously overlooked. Additionally, the system is found to simultaneously achieve large frequency shifts and sub-100 nm spin wave wavelengths, which can be tuned or even enhanced by adjusting the external magnetic field to control the twist angle of the helical magnetization state and the thickness of the NiFe sublayer, offering significant implications for magnonic device applications. The established model and the physical mechanism explaining the frequency shift have been validated by recent simulations and experimental results.\n19. First principles study of thermoelectric properties of $\\text{Nb}_2\\text{Co}_2\\text{InSb}$ and $\\text{Nb}_2\\text{Co}_2\\text{GaSb}$ double half-Heuslers Relevance Score: 3.1676 Authors: Rajeev Ranjan Link: http://arxiv.org/abs/2604.00775v1 Summary: This work systematically investigates the thermoelectric properties of two double half-Heusler compounds, Nb₂Co₂InSb and Nb₂Co₂GaSb, using first-principles calculations. These materials can be regarded as derivatives of the parent half-Heusler compound NbCoSn (with a thermal conductivity of approximately 13–18 W/mK) where Sn sites are substituted by In/Ga and Sb, aiming to reduce lattice thermal conductivity through the introduction of mass disorder. The study considers two ordered phases and two special quasirandom structures (SQS). Energy analysis indicates that Nb₂Co₂InSb is most stable in the ordered phase, whereas Nb₂Co₂GaSb exhibits lower energy in the SQS phase. Using the Debye-Callaway model, the lattice thermal conductivity at room temperature is calculated to be in the range of 5.5–6.9 W/mK for Nb₂Co₂InSb and 4.7–5.8 W/mK for Nb₂Co₂GaSb, both less than half of that of NbCoSn, confirming the effective suppression of thermal conductivity by mass disorder. Electronic structure calculations reveal that the ordered phases have lower band gaps and higher carrier mobilities, leading to significantly superior power factors compared to the disordered phases. Integrating the electrical and thermal transport properties, these double half-Heusler compounds exhibit greater potential for thermoelectric applications than the parent ternary system.\n20. Strain-tunable multipiezo effects in Janus monolayer Cr2SSe: Selective reversal of valley polarization and single-spin-channel anomalous valley Hall effect Relevance Score: 3.1374 Authors: Quan Shen, Jianing Tan, Tao Yao, Wenhu Liao, Jiansheng Dong Affiliations: Jishou University Link: http://arxiv.org/abs/2604.00629v1 Summary: Through first-principles calculations, this work predicts that the Janus monolayer Cr₂SSe exhibits intrinsic inversion symmetry breaking while demonstrating strain-tunable multi-piezoelectric effects and unique valleytronic properties. The system shows significant spin splitting and band inversion at the X and Y high-symmetry points in the Brillouin zone, forming robust spin-valley locking, with valley degeneracy protected by diagonal mirror symmetry. Application of uniaxial strain can break this symmetry and simultaneously induce piezovalley, piezoelectric, and piezomagnetic responses, realizing multi-piezoelectric effects. Strain along orthogonal crystal directions produces opposite valley polarization, while under small compressive strain, selective reversal of valley polarization can be achieved, enabling independent control of valence and conduction band valleys and facilitating a single-spin-channel anomalous valley Hall effect. The maximum conduction band valley polarization reaches 57.6 meV under 4% tensile strain. These findings provide a pathway for low-power, nonvolatile manipulation of valley degrees of freedom and enhancement of spin transport efficiency, laying a theoretical foundation for the design of efficient valleytronic devices.\n","permalink":"https://nickelates.uk/en/posts/2026-04-01-arxiv-daily/","summary":"\u003cblockquote\u003e\n\u003cp\u003e\u003cstrong\u003eDaily Overview\u003c/strong\u003e:\nThe highlights of today\u0026rsquo;s work focus on an in-depth exploration of electronic structures and pairing symmetries in the field of nickel-based superconductivity. In [1], a theoretical design based on DFT+DMFT proposes that the cobalt-based layered compound La₄Co₂NiO₈Cl₂ exhibits strongly correlated electronic characteristics highly similar to those of superconducting La₄Ni₃O₁₀, including non-Fermi liquid behavior in the outer Co orbitals and flat bands near the M point, providing a theoretical candidate for the search of new cobalt-based high-temperature superconductors. In [2], researchers systematically calculated the electronic Raman response using a two-orbital bilayer model, indicating that Raman scattering can effectively distinguish between s±-wave and nodal d-wave pairing symmetries in bilayer nickelate La₃Ni₂O₇. In particular, the low-energy power-law behavior can clearly identify nodal states, offering a powerful means for experimentally determining the superconducting gap structure. Furthermore, [3] reports the observation of superconductivity at 16.3 K in the altermagnetic candidate material Na₂₋ₓV₂Se₂O. Its layered structure serves as a structural bridge between cuprates/nickelates and iron-based superconductors, expanding the correlated superconducting material system and providing valuable insights for understanding unconventional superconducting mechanisms.\n\u003cstrong\u003earXiv submission processing window\u003c/strong\u003e: 2026-03-31 22:24 to 2026-04-01 17:59 UTC.\u003c/p\u003e","title":"arXiv Daily: nickelate superconductors 2026-04-01"},{"content":" Daily Overview: Today\u0026rsquo;s paper overview does not directly target nickelate superconductors, but several studies have made key progress in superconducting pairing mechanisms, the coexistence of electronic liquid-crystal order and superconductivity, and methodology for strongly correlated surface states—all closely related to the unconventional superconducting mechanisms and layered structure issues currently of interest in the nickel-based superconductor field. In [1], Norman explains the anisotropic superconducting gap of KTaO₃ heterojunctions based on the Slater soft mode, emphasizing the importance of cooperative multi-phonon-mode pairing and providing an analogy for the role of electron-phonon coupling in nickel-based superconductivity. In [2], Butler et al. observe short-range electronic nematic order coexisting with superconductivity in NaAlSi; the spatial modulation of its superconducting gap suggests a possible intertwining of nematic order and superconducting order, similar to that in nickel-based superconductors. In [6], Klebl et al. propose a surface functional renormalization group method that offers an efficient numerical tool for treating strong correlations on the surfaces of quasi-two-dimensional nickelate systems and reveals that interlayer coupling can induce novel ordered phases beyond those in purely two-dimensional models. These results advance the understanding of unconventional superconductivity and its associated correlated electronic states from various perspectives. arXiv submission processing window: 2026-01-15 20:18 to 2026-01-16 19:16 UTC.\n1. Superconductivity from the Slater mode: Application to KTaO3 heterostructures Relevance Score: 4.3608 Authors: M. R. Norman Link: http://arxiv.org/abs/2601.10903v1 Summary: This study theoretically analyzes the electron pairing mechanism mediated by the Slater soft transverse optical phonon mode—a characteristic mode of quantum paraelectrics—to explain the superconductivity observed in the two-dimensional electron gas at KTaO3 hetero-interfaces. By performing explicit electron-phonon coupling calculations based on first-principles parameters and employing a bilayer approximation to describe the interfacial electronic structure, the linearized gap equation is solved. Key findings include: (1) the dependence of the superconducting transition temperature on different crystal orientations (111, 110, 001) qualitatively agrees with experiments, and the gap function exhibits significant band-index dependence and in-plane angular anisotropy; (2) the BCS coupling constant contributed solely by this soft mode is too small to quantitatively account for the observed absolute Tc values, indicating that pairing contributions from other optical phonons (e.g., high-frequency LO modes) must be introduced to enhance the coupling strength. This work places earlier phenomenological theories on a more rigorous microscopic foundation, reveals the crucial role of dynamic Rashba-type electron-phonon interaction in gap anisotropy, and suggests that superconductivity in the KTaO3 system results from the cooperative pairing of multiple phonon modes.\n2. Coexisting electronic smectic liquid crystal and superconductivity in a Si square-net semimetal Relevance Score: 4.1460 Authors: Christopher J. Butler, Toshiya Ikenobe, Ming-Chun Jiang, Daigorou Hirai, Takahiro Yamada, Guang-Yu Guo, Ryotaro Arita, Tetsuo Hanaguri, Zenji Hiroi Link: http://arxiv.org/abs/2601.10939v2 Summary: By scanning tunneling microscopy, researchers observed short-range charge stripe (electronic nematic-smectic liquid crystal) order on the surface of the half-metallic superconductor NaAlSi with a silicon square lattice structure, and this stripe order coexists with the superconducting state. Experiments reveal that the stripe order exhibits pronounced spatial fluctuations and weak pinning characteristics, with a wave vector incommensurate with the lattice, and displays two orthogonal directions with 90° rotational symmetry in two energy intervals above and below the Fermi level. Furthermore, the superconducting gap magnitude shows spatial modulation perpendicular to the stripe direction in phase with the local density of states, indicating that the superconducting order and smectic order are intertwined, forming a secondary \u0026ldquo;Cooper pair liquid crystal.\u0026rdquo; First-principles calculations suggest a possible driving mechanism: due to the extremely flat dispersion of two large flat hole pockets formed by silicon p orbitals near the Fermi surface, lifting degeneracy through a similar band Jahn-Teller effect can significantly reduce kinetic energy and induce nesting instability leading to translational symmetry breaking, thereby forming the smectic phase. This study realizes electronic liquid crystal behavior in a p-orbital electron system, providing a new paradigm for understanding the coexistence relationship between unconventional superconductivity and electronic liquid crystal states.\n3. Widefield NV Magnetic Field Reconstruction for Probing the Meissner Effect and Critical Current Density under Pressure Relevance Score: 4.0542 Authors: Kin On Ho, Cassandra Dailledouze, Martin Schmidt, Loïc Toraille, Marie-Pierre Adam, Jean-François Roch Affiliations: The University of Texas at Austin Link: http://arxiv.org/abs/2601.10838v1 Summary: Using wide-field nitrogen-vacancy (NV) center magnetic imaging, researchers quantitatively reconstructed the magnetic field distribution of HgBa₂Ca₂Cu₃O₈₊δ (Hg-1223) superconducting microcrystals under a pressure of 4 GPa. By fitting the NV ground-state Hamiltonian and considering the relative intensities of resonances, the local magnetic field magnitude and angle were obtained, and the temperature-dependent Meissner effect magnetic field expulsion was reconstructed. Comparing the derived parameters with the Brandt model, which describes the magnetic behavior of type-II superconductors, the critical current density j_c was extracted. The results show that j_c is approximately 10⁵ A/cm² at 120 K, consistent with literature values at ambient pressure. This work achieved the first wide-field quantitative reconstruction of the Meissner effect under pressure, providing an optical method for studying critical current density and offering new insights into the application of NV magnetometry in high-pressure superconductivity research.\n4. Majorana Zero Modes and Topological Nature in Bi2Ta3S6-family Superconductors Relevance Score: 3.9040 Authors: Yue Xie, Zhilong Yang, Ruihan Zhang, Sheng Zhang, Quansheng Wu, Gang Wang, Hongming Weng, Zhong Fang, Xi Dai, Zhijun Wang Link: http://arxiv.org/abs/2601.11175v1 Summary: This study reports that Bi₂Ta₃S₆ family superconductors exhibit nontrivial topological band properties, with their natural quantum well structure composed of alternating TaS₂ layers and honeycomb-like Bi layers, contributing superconductivity and topological characteristics, respectively. Through symmetry indicators and first-principles calculations, it is found that the topological properties originate entirely from the Bi layers, corresponding to a quantum spin Hall phase described by the p_x-p_y model. Using VASP2KP, the in-plane g-factors of zigzag and armchair edge states are calculated, showing strong anisotropy. Based on electron-phonon coupling and the McMillan formula, the superconducting transition temperatures of related compounds are estimated. Further combining experimental superconducting gaps with calculated g-factors, a phase diagram is obtained, indicating that in a Bi monolayer of Bi₂Ta₃S₆, an in-plane magnetic field greater than 2.62 T can generate corner Majorana zero modes, with a similar mechanism applicable to Majorana hinge modes in bulk materials. These natural quantum well superconductors provide an ideal platform for exploring topological superconductivity and Majorana zero modes.\n5. Conductance Oscillations in a Topological Insulator-Disordered Superconductor Hybrid Interface Relevance Score: 3.8162 Authors: Jagadis Prasad Nayak, Aviad Frydman, Gopi Nath Daptary Link: http://arxiv.org/abs/2601.11355v1 Summary: This study couples the topological insulator BiSbTeSe2 (BSTS) with the disordered superconductor amorphous indium oxide (a-InO), investigating proximity-induced superconductivity through resistance-temperature measurements and differential conductance spectroscopy. Even when InO is in the insulating state, a significant drop in low-temperature resistance is observed, indicating persistent superconducting correlations. The differential conductance spectra exhibit quasi-periodic oscillations at higher bias voltages, accompanied by a prominent zero-bias conductance peak; both features vanish at higher temperatures, corresponding to the critical temperature of superconducting islands in InO. By tuning the carrier density via gate voltage, the oscillation spacing varies with voltage, and analysis reveals that it follows the McMillan-Rowell mechanism, with an effective superconducting path length of approximately 50 nm. All superconducting characteristics disappear above 10 K, far exceeding the global superconducting transition temperature of InO. These results unveil the critical role of topological surface states in proximity-induced superconductivity and highlight the influence of superconducting fluctuations at the disordered superconductor/topological insulator hybrid interface, offering important insights into the understanding of novel quantum states in such systems.\n6. Surface Functional Renormalization Group for Layered Quantum Materials Relevance Score: 3.6744 Authors: Lennart Klebl, Dante M. Kennes Link: http://arxiv.org/abs/2601.11055v2 Summary: This paper proposes a surface functional renormalization group method, extending two-dimensional functional renormalization group to the surface or interface of three-dimensional systems for efficiently treating surface layer interactions. Using a semi-infinite stack of two-dimensional square lattices as a model, a Hubbard interaction is introduced on the surface layer, along with alternating interlayer couplings analogous to the SSH model. Through this method, the study explores the evolution of the phase diagram starting from the strongly correlated state of a decoupled two-dimensional surface layer upon adding interlayer coupling. The results indicate that, over most of the interlayer hopping parameter range, the physics of the two-dimensional system dominates, manifesting as antiferromagnetic, d-wave superconducting, and ferromagnetic correlations. However, at moderate interlayer coupling and intermediate interaction strengths, the superconducting state is split into two parts by a narrow region of incommensurate spin density wave and spin bond order, providing a possibility for realizing chiral spin bond order. This work offers a numerically efficient biased approach for studying strongly correlated surface electronic states of quasi-two-dimensional systems in a three-dimensional environment, and reveals that interlayer coupling can induce novel ordered phases beyond those of purely two-dimensional models.\n7. Oriented Triplet $p$-Wave Pairing from Fermi surface Anisotropy and Nonlocal Attraction Relevance Score: 3.5601 Authors: Shuning Tan, Ji Liu, Minghuan Zeng, Tao Ying, Zhangkai Cao, Ho-Kin Tang Link: http://arxiv.org/abs/2601.11267v1 Summary: Using the constrained-path quantum Monte Carlo method, we investigate the ground-state phase diagram of the two-dimensional attractive t-U-V Hubbard model with nearest-neighbor attraction V and spin-dependent hopping anisotropy α at a filling n≈0.85. Three phases are identified: on-site s-wave superfluid, Cooper pair Bose metal (CPBM), and oriented spin-equal triplet p-wave pairing. The nearest-neighbor attraction activates the odd-parity channel, while the hopping anisotropy suppresses competing s-wave coherence and selects the px/py polar axis, thereby lowering the critical |V_c| for the onset of triplet-dominant p-wave pairing. Channel-resolved Landau analysis yields a Landau p-wave scale V_c^L(α) that is consistent with the observed dependence of |V_c| on anisotropy. Our results demonstrate that nearest-neighbor interactions and Fermi surface anisotropy cooperate to generate oriented triplet p-wave pairing, suggesting possible realization in cold atoms and altermagnet platforms.\n8. Spontaneous Anomalous Hall Effect at Room Temperature in Antiferromagnetic Material NbMnAs Relevance Score: 3.5446 Authors: Yuki Arai, Junichi Hayashi, Keiki Takeda, Hideki Tou, Eiichi Matsuoka, Hitoshi Sugawara, Hisashi Kotegawa Link: http://arxiv.org/abs/2601.11088v1 Summary: Recent studies have shown that certain antiferromagnetic materials with the same symmetry breaking as ferromagnets can produce significant ferromagnetic responses. Here, we report a new antiferromagnetic material, NbMnAs, which exhibits a large anomalous Hall effect at zero magnetic field and room temperature, despite its very small net magnetization. Polycrystalline NbMnAs (near stoichiometric composition) enters an antiferromagnetic state below the Néel temperature T_N = 354 K, with a spontaneous magnetization of approximately 6 × 10⁻³ μB/Mn and an anomalous Hall effect; in contrast, single crystals grown by the flux method show a reduced T_N and increased spontaneous magnetization due to As-site vacancies. Electrical transport measurements reveal pronounced anomalous Hall hysteresis loops at zero field in both polycrystalline and single-crystal samples. The low-temperature anomalous Hall conductivity of the single crystal is about 20 S/cm, which, while smaller than those of Mn₃Sn and Mn₃Ge, is much higher than that of other room-temperature antiferromagnetic materials (such as MnTe and FeS). This anomalous Hall effect originates from the same magnetic point group symmetry as NbMnP, allowing a zero-field Hall voltage. Although the quality of the single crystals still requires improvement, NbMnAs represents a new material that generates a significant ferromagnetic response from antiferromagnetism at room temperature, with potential applications in spintronics and thermoelectrics.\n9. Visualization of Tunable Electronic Structure of Monolayer TaIrTe$_4$ Relevance Score: 3.3425 Authors: Sandy Adhitia Ekahana, Aalok Tiwari, Souvik Sasmal, Zefeng Cai, Ravi Kumar Bandapelli, I-Hsuan Kao, Jian Tang, Chenbo Min, Tiema Qian, Kenji Watanabe, Takashi Taniguchi, Ni Ni, Qiong Ma, Chris Jozwiak, Eli Rotenberg, Aaron Bostwick, Simranjeet Singh, Noa Marom, Jyoti Katoch Link: http://arxiv.org/abs/2601.11504v1 Summary: This study directly measured the band structure of monolayer TaIrTe₄ using micrometer-scale spatially resolved micro-angle-resolved photoemission spectroscopy. The experimentally observed dispersions quantitatively agree with density functional theory calculations using the Heyd-Scuseria-Ernzerhof hybrid functional, confirming its insulating ground state with no evidence of strong electronic correlation. Furthermore, a pronounced electron-hole asymmetry in the doping response was revealed: hole doping can be readily achieved via electrostatic gating, whereas electron doping (whether through gating or alkali metal deposition) does not induce a rigid upward shift of the Fermi level but instead leads to band renormalization and band gap narrowing. Experimental and theoretical results together demonstrate that induced charges reshape the band topology of monolayer TaIrTe₄ through band renormalization rather than rigid band shifts, revealing that doping can fundamentally alter the electronic structure beyond the conventional rigid band assumption.\n10. Nanoscale wireframe SQUID on a cantilever by corner lithography Relevance Score: 3.2411 Authors: Thijs J. Roskamp, Tim Horstink, Melissa J Goodwin, Erwin Berenschot, Edin Sarajilic, Roeland Huijink, Niels Tas, Hans Hilgenkamp Affiliations: Bruker Nano Surfaces \u0026amp; Metrology, University of Twente Link: http://arxiv.org/abs/2601.11331v1 Summary: This paper reports a method for fabricating nanoscale superconducting quantum interference devices (SQUIDs) at the tips of self-aligned superconducting cantilever probes. Using corner lithography, a nanowire framework with tunable tip structures is first formed on a silicon substrate through a molding process. Subsequently, niobium (Nb) is deposited via magnetron sputtering utilizing the shadowing effect, forming a self-aligned superconducting wire framework and device circuitry. A focused ion beam nanofabrication step then introduces a superconducting weak link at the tip, thereby constituting the SQUID. The effective diameter of the fabricated SQUID can be controlled from 100 nanometers to several micrometers, enabling operation in magnetic fields up to 1 tesla, with the nanowires in the framework serving as local flux modulators. This process enables batch fabrication of wafer-scale templates, offering a scalable manufacturing route for scanning probes based on tip-integrated superconducting devices.\n11. Raman scattering fingerprints of the charge density wave state in one-dimensional NbTe$_4$ Relevance Score: 3.2091 Authors: Natalia Zawadzka, Cem Sevik, Zahir Muhammad, Zia Ur Rehman, Weisheng Zhao, Adam Babiński, Maciej R. Molas Link: http://arxiv.org/abs/2601.11502v1 Summary: Here, we investigate the charge density wave state in quasi-one-dimensional NbTe₄ using Raman scattering spectroscopy. At 5 K, 25 phonon modes are observed in resonance-enhanced Raman spectra, and polarization measurements reveal a strong coupling between phonon mode symmetry and crystal symmetry, with mode polarization directions either parallel or perpendicular to the c-axis, which is the extended direction of the one-dimensional structure. Temperature-dependent Raman measurements identify a transition between commensurate and incommensurate charge density wave phases, accompanied by significant thermal hysteresis: the transition temperature is approximately 45 K upon cooling and 90 K upon warming. The hysteresis width varies with the heating rate, indicating a limited nucleation rate of charge density wave domains, a property that suggests potential for memory device applications.\n12. Unexpected Anisotropic Mn-Sb Anti-site Distribution and Van der Waals Epitaxy of MnSb2Te4 Relevance Score: 3.1537 Authors: Gustavo Chavez Ponce de Leon, Ahmad Dibajeh, Gert ten Brink, Majid Ahmadi, Bart Jan Kooi, George Palasantzas Affiliations: University of Groningen Link: http://arxiv.org/abs/2601.11353v1 Summary: In this study, MnSb2Te4 polycrystalline samples were synthesized via a two-step method using MnTe and Sb2Te3 as precursors, and their ferromagnetic/ferrimagnetic properties were confirmed by DC-SQUID magnetometry. High-resolution scanning transmission electron microscopy combined with energy-dispersive spectroscopy revealed an anisotropy in the Mn-Sb antisite distribution that breaks inversion symmetry: within a single septuple layer, one of the two Sb layers contains a higher Mn concentration. This sub-nanometer-scale asymmetric distribution resembles the recently proposed Janus materials, offering the potential to combine topological and magnetic properties with nonlinear optics and piezoelectric effects. Furthermore, to investigate the interplay among antisite defects, doping, topology, and magnetism, a van der Waals epitaxy method utilizing a Sb2Te3 seed layer on amorphous SiOx was introduced, and MnSb2Te4 thin films were successfully grown by pulsed laser deposition, as confirmed by scanning transmission electron microscopy. This approach enables compatibility with silicon-based architectures and allows gate tuning of the Fermi level, representing a critical step toward practical applications.\n13. Three-dimensional topological insulator feature of ternary chalcogenide Ge2Bi2Te5 Relevance Score: 3.1280 Authors: Shangjie Tian, Yuchong Zhang, Chenhao Liang, Yuqing Cao, Wenxin Lv, Xingyu Lv, Zhijun Wang, Tian Qian, Hechang Lei, Shouguo Wang Link: http://arxiv.org/abs/2601.11339v1 Summary: This study focuses on the ternary layered chalcogenide Ge₂Bi₂Te₅, where high-quality single crystals were grown via the self-flux method. Through a combination of electrical transport measurements, angle-resolved photoemission spectroscopy (ARPES), and first-principles calculations, it is confirmed to be a three-dimensional strong topological insulator. Electrical transport results reveal hole-type carrier-dominated metallic behavior, with the bulk electronic structure exhibiting a hole-type Fermi surface at the Fermi level. Using pump-probe ARPES, a Dirac point located 290 meV above the Fermi level is observed, corresponding to an unoccupied topological surface state with anisotropic dispersion and threefold symmetry. Theoretical calculations confirm a bulk band gap of approximately 50 meV and a nontrivial Z₂ topological invariant (000;1). This work demonstrates that Ge₂Bi₂Te₅ not only possesses topological insulator properties but also exhibits phase-change material characteristics, providing a multifunctional platform for exploring the integration of topological quantum states with nonvolatile memory technology.\n14. Disorder effects in two-dimensional flat-band system with next-nearest-neighbor hopping Relevance Score: 3.0938 Authors: Yue Heng Liu, Zi-Xiang Hu, Qi Li Link: http://arxiv.org/abs/2601.10932v1 Summary: 针对二维Lieb晶格，本研究采用转移矩阵方法，系统分析了复数次近邻跳跃对平带局域化机制的影响。研究发现，在弱无序条件下，拓扑边缘态能够有效缓解平带固有的几何局域化；而当引入关联无序时，系统表现出逆安德森转变现象，且拓扑边缘态在强无序环境下依然保持稳定。通过陈数计算进一步证实了该鲁棒性的根源。这些结果揭示了拓扑相变、平带物理与无序效应之间的内在联系，为相关研究构建了统一的理论平台。\n15. Two-dimensional Intrinsic Janus Structures: Design Principle and Anomalous Nonlinear Optics Relevance Score: 3.0909 Authors: Yang Li, Chengzhi Wu, Xuelian Sun, Liangting Ye, Yirui Lu, Hai-Qing Lin, Wenhui Duan, Bing Huang Link: http://arxiv.org/abs/2601.11167v1 Summary: We propose a first-principles alloy theory based on cluster expansion, which reveals the formation mechanism of intrinsic Janus structures in the distorted 1T phase among multiple competing phases by introducing cation-mediated strong repulsive interactions of anion-pair clusters and delicate competition among short-range clusters. This theory not only explains why intrinsic Janus structures are only occasionally observed in heteroelement alloys such as RhSeCl and BiTeI, but also accurately predicts a variety of easily synthesizable 1T-like intrinsic Janus materials. Taking RhSeCl as an example, we find that intrinsic Janus materials can exhibit anomalous second-harmonic generation (SHG) and unique quantum geometric effects, arising from strong lattice and chemical potential mirror symmetry breaking. Moreover, an unexpected new skin effect emerges in finite-thickness RhSeCl, accompanied by a hidden SHG effect in the bulk region. This theory paves the way for the design of intrinsic Janus materials from scratch, significantly accelerating the development of Janus science.\n16. Homogeneous Microwave Delivery for Quantum Sensing with Nitrogen-Vacancy Centers at High Pressures Relevance Score: 3.0838 Authors: Timothy A. Elmslie, Luca Basso, Adam Dodson, Jacob Henshaw, Andrew M. Mounce Link: http://arxiv.org/abs/2601.11725v1 Summary: To address the inhomogeneous microwave field transmission for nitrogen-vacancy (NV) centers in high-pressure diamond anvil cells, this study designed and characterized a novel slotted platinum foil microwave transmission line. Through zero-field and biased-field optically detected magnetic resonance (ODMR) measurements under pressures ranging from 1 to 48 GPa, and by calculating the microwave field intensity on the diamond anvil surface via Rabi frequency, it was found that the slotted design generates a more uniform and stronger microwave field than conventional metal wires, thereby enhancing the capability to detect spatial variations in samples during wide-field high-pressure measurements. The pressure-dependent ODMR linewidth was also experimentally determined, with the linewidth increasing after approximately 10 GPa due to the non-hydrostatic nature of the pressure medium. The study demonstrates that this slotted microwave line offers advantages in spatially resolved NV quantum sensing.\n17. Controlled Parity of Cooper Pair Tunneling in a Hybrid Superconducting Qubit Relevance Score: 3.0173 Authors: David Feldstein-Bofill, Leo Uhre Jacobsen, Ksenia Shagalov, Zhenhai Sun, Casper Wied, Shikhar Singh, Anders Kringhøj, Jacob Hastrup, András Gyenis, Karsten Flensberg, Svend Krøjer, Morten Kjaergaard Link: http://arxiv.org/abs/2601.11303v1 Summary: This study proposes a hybrid superconducting circuit element called the \u0026ldquo;harmonic parity qubit\u0026rdquo; (HPQ), which achieves active control of Josephson harmonic parity by forming a SQUID structure through the parallel connection of two aluminum oxide tunnel junctions (SIS-SIS arms) with a gate-voltage-tunable InAs/Al nanowire junction (S-Sm-S arm). Biased at half a magnetic flux quantum, the odd harmonics of the two arms cancel each other, suppressing the odd harmonic components by more than two orders of magnitude relative to even harmonics, resulting in a π-periodic double-well potential dominated by even harmonics. By performing flux-dependent spectroscopy measurements at 85 gate voltage points and fitting the complete circuit Hamiltonian, the Fourier harmonic distribution of the energy-phase relation is directly reconstructed, revealing three tunable regimes: conventional single Cooper pair tunneling, mixed harmonics, and even-harmonic-dominated behavior. This element can realize supercurrent carried by Cooper pairs, providing a compact and programmable new building block for Fourier engineering in superconducting quantum circuits, with potential applications in parity-protected qubits and beyond.\n18. Magnetization and anomalous Hall effect in SiO2/Fe/SiO2 trilayers Relevance Score: 3.0028 Authors: Sudhansu Sekhar Das, M. Senthil Kumar Affiliations: Indian Institute of Technology Bombay Link: http://arxiv.org/abs/2601.11001v1 Summary: SiO2/Fe/SiO2 sandwich-structured films were fabricated by sputtering, and the effect of Fe layer thickness (t_Fe) was systematically investigated. Structural characterization revealed that the Fe layer exhibited a nanocrystalline (110) texture, while the SiO2 layers were amorphous. Magnetic measurements indicated soft ferromagnetic behavior with strong in-plane anisotropy, and a complex temperature dependence of magnetization, involving coexistence of ferromagnetism and superparamagnetism. Hall effect measurements showed the presence of the anomalous Hall effect (AHE); as t_Fe decreased from 300 Å to 50 Å, the saturated anomalous Hall resistance (R_Ahs) increased by approximately 14 times, reaching a maximum of 2.3 Ω, which is about four orders of magnitude higher than that of bulk Fe. Compared with single-layer Fe films, the R_Ahs in the sandwich structure exhibited a maximum increase of 56%. The scaling relation R_s ∝ ρ^1.9 indicated that side-jump is the dominant mechanism of the AHE. In addition, the sensitivity S was enhanced by up to 156%. This study reveals the significant enhancement of the AHE by interface scattering from the insulating layers.\n","permalink":"https://nickelates.uk/en/posts/2026-01-16-arxiv-daily/","summary":"\u003cblockquote\u003e\n\u003cp\u003e\u003cstrong\u003eDaily Overview\u003c/strong\u003e:\nToday\u0026rsquo;s paper overview does not directly target nickelate superconductors, but several studies have made key progress in superconducting pairing mechanisms, the coexistence of electronic liquid-crystal order and superconductivity, and methodology for strongly correlated surface states—all closely related to the unconventional superconducting mechanisms and layered structure issues currently of interest in the nickel-based superconductor field. In [1], Norman explains the anisotropic superconducting gap of KTaO₃ heterojunctions based on the Slater soft mode, emphasizing the importance of cooperative multi-phonon-mode pairing and providing an analogy for the role of electron-phonon coupling in nickel-based superconductivity. In [2], Butler et al. observe short-range electronic nematic order coexisting with superconductivity in NaAlSi; the spatial modulation of its superconducting gap suggests a possible intertwining of nematic order and superconducting order, similar to that in nickel-based superconductors. In [6], Klebl et al. propose a surface functional renormalization group method that offers an efficient numerical tool for treating strong correlations on the surfaces of quasi-two-dimensional nickelate systems and reveals that interlayer coupling can induce novel ordered phases beyond those in purely two-dimensional models. These results advance the understanding of unconventional superconductivity and its associated correlated electronic states from various perspectives.\n\u003cstrong\u003earXiv submission processing window\u003c/strong\u003e: 2026-01-15 20:18 to 2026-01-16 19:16 UTC.\u003c/p\u003e","title":"arXiv Daily: nickelate superconductors 2026-01-16"},{"content":" Daily Overview: Dear readers, welcome to today\u0026rsquo;s overview of the latest papers in the field of nickelate superconductivity. Although the highlight works of today do not directly focus on nickelates, multiple papers are highly relevant to the core issues in the nickelate superconductivity field in terms of mechanisms, methods, or phenomena, making them worthy of close attention. For example, [5] reveals the critical role of correlated hopping interactions in driving superconducting phase transitions, providing a theoretical framework for understanding possible non-local correlation effects in nickelates; [11] proposes microwave Kerr/Faraday resonance as a sensitive probe for detecting time-reversal symmetry breaking in chiral superconductors, a technique that can be extended to the study of pairing symmetry in nickel-based superconductors; [12] reports the coexistence of magnetic and multipole orders and their constraints on superconducting pairing in CeRh₂As₂, offering analogies to the competition between spin fluctuations and superconductivity in nickelates; [14] uncovers multi-scale dynamic modulation structures in SrTiO₃, where lattice instability shares physical similarities with charge order and lattice coupling in nickelates; [15] constructs a theory of composite Bogoliubov Fermi liquids, providing a new paradigm for unconventional superconductivity in Chern bands, which may inspire theoretical exploration of topological superconducting states in nickelates. These works expand the understanding of strong correlations and unconventional superconductivity from different dimensions, offering research ideas and tools that can be applied to the nickelate superconductivity field. arXiv submission processing window: 2026-01-14 20:07 to 2026-01-15 18:50 UTC.\n1. Growth and hydrostatic-pressure study of a type-II superconductor Bi$_2$Ta$_3$S$_6$ single crystal Relevance Score: 4.3421 Authors: Li Chenglin, Yang Yaling, Yang Zhilong, Deng Junze, Zhang Ruihan, Chen Weiwei, Pan Yue, Wang Yulong, Wang Xuhui, Wang Bosen, Wang Zhijun, Wang Gang Affiliations: University of Science and Technology Beijing, Aalto University, University of Chinese Academy of Sciences, Chinese Academy of Sciences Link: http://arxiv.org/abs/2601.10195v1 Summary: Using chemical vapor transport, high-quality Bi₂Ta₃S₆ single crystals with the P6₃/mcm space group, composed of alternating Ta-S layers and Bi layers, were successfully grown. Resistivity, magnetic susceptibility, and Hall effect measurements revealed a superconducting transition at 0.84 K with an upper critical field of 231 Oe (out-of-plane), characteristic of a typical type-II superconductor, exhibiting anisotropic Ginzburg-Landau parameters κₐb = 7.67 and κ_c = 4.50, and hole-dominated carriers. Under hydrostatic pressure, the superconducting transition temperature and upper critical field increased sharply at low pressures (to approximately 4 and 4.5 times their ambient values, respectively) before being slightly suppressed at higher pressures. First-principles calculations indicated the presence of nontrivial topological surface states on the (100) surface of Bi₂Ta₃S₆, offering a new direction for searching for intrinsic topological superconductors in layered transition metal dichalcogenides.\n2. Emergence of unconventional magnetic order in strain-engineered RuO2/TiO2 superlattices Relevance Score: 4.0541 Authors: Seung Gyo Jeong, Seungjun Lee, Jin Young Oh, Bonnie Y. X. Lin, Anand Santhosh, James M. LeBeau, Alexander J. Grutter, Woo Seok Choi, Tony Low, Valeria Lauter, Bharat Jalan Affiliations: University of Minnesota, Massachusetts Institute of Technology, Sungkyunkwan University, National Institute of Standards and Technology, Oak Ridge National Laboratory Link: http://arxiv.org/abs/2601.10518v1 Summary: Using hybrid molecular beam epitaxy, fully strained RuO₂/TiO₂ superlattices were grown on TiO₂(110) substrates. Polarized neutron reflectometry directly observed a finite magnetic moment in the compressively strained RuO₂ layers, providing conclusive evidence of an uncompensated magnetic order. Combined density functional theory and X-ray photoelectron spectroscopy analyses indicate that epitaxial strain shifts the Ru 4d states toward the Fermi level, triggering a Stoner-type instability that stabilizes the uncompensated magnetic order along the [001] direction. This work reveals that strain engineering can induce unconventional magnetic states in RuO₂ that are absent in the bulk material, offering a crucial pathway for exploring and controlling magnetic phases in such oxides.\n3. Multiple Andreev Reflection Effects in Asymmetric STM Josephson Junctions Relevance Score: 3.6752 Authors: Wan-Ting Liao, S. K. Dutta, R. E. Butera, C. J. Lobb, F. C. Wellstood, M. Dreyer Link: http://arxiv.org/abs/2601.09889v1 Summary: This study constructed a Josephson junction between a Nb tip and a Nb sample using scanning tunneling microscopy (STM), and measured current-voltage characteristics at 50 mK and 1.5 K by varying the tip–sample distance to tune the normal-state resistance Rn from 1 kΩ to 10 MΩ. As Rn decreased, the junction evolved from the phase diffusion regime to an underdamped small junction regime, and further to a point-contact regime. Significant multiple Andreev reflection (MAR) features were observed in the subgap structures, whose amplitude and onset energy sensitively depended on junction transparency and gap asymmetry. To interpret these spectra, the Averin–Bardas MAR theory was generalized to superconductors with unequal gaps, establishing a quantitative model applicable to asymmetric STM junctions. Fitting the data yielded the dependence of the electrode superconducting gaps, barrier transparency, and number of conducting channels on Rn. Combined with Josephson junction dynamics, the observed switching current, retrapping current, and finite resistance of the superconducting branch were also explained. The results demonstrate that accounting for intrinsic electrode asymmetry is crucial for reliably extracting transport parameters of STM-based superconducting weak links.\n4. Electronic structure theory of H$_{3}$S: Plane-wave-like valence states, density-of-states peak and its guaranteed proximity to the Fermi level Relevance Score: 3.6519 Authors: Ryosuke Akashi Link: http://arxiv.org/abs/2601.10016v1 Summary: Through first-principles calculations and wave function analysis, this study reveals the formation mechanism of the density-of-states peak in sulfur superhydride H₃S under high pressure. The results indicate that the valence wave functions exhibit a significant plane-wave-like character, and by analyzing the Fourier modes of the self-consistent potential and atomic pseudopotential, a near-uniform model that accurately reproduces the first-principles band structure with only a few parameters can be extracted. The density-of-states peak originates from the hybridization of specific plane waves, and the proximity between the Jones zone and the spherical Fermi surface of plane waves is the fundamental cause of multi-plane-wave hybridization, the formation of the density-of-states peak, and its stable position near the Fermi level. This theory not only resolves the minimal modeling of the electronic states of H₃S but also provides a generalizable mechanism for enhancing the superconducting transition temperature of pressure-induced superconductors by strengthening the density-of-states peak.\n5. Beyond Hubbard: the role of correlated hopping interaction in superconductors and quantum dot devices Relevance Score: 3.6475 Authors: Karol I. Wysokiński, Marcin M. Wysokiński Link: http://arxiv.org/abs/2601.10619v1 Summary: This study goes beyond the standard Hubbard model to systematically examine the central role of correlated hopping (CH) interactions in two strongly correlated systems. For superconductors, CH is revealed as a key mechanism driving the superconducting phase transition; as the system approaches the Mott metal–insulator transition, it significantly modifies the evolution of spectral functions and influences the structure and symmetry of the superconducting gap. For quantum dot devices, CH modulates the effective tunneling amplitude between the quantum dot and metallic electrodes; using non-equilibrium Green\u0026rsquo;s function methods to compute the differential conductance in a normal-metal–quantum-dot–normal-metal setup, the resulting characteristics clearly indicate the presence and sign of the CH interaction. These conclusions demonstrate that CH, as a ubiquitous nonlocal correlation effect, plays a non-negligible physical role in both strongly correlated superconductivity and nanoelectronic transport.\n6. Topological textures and emergent altermagnetic signatures in ultrathin BiFeO3 Relevance Score: 3.5080 Authors: George Fratian, Maya Ramesh, Xinyan Li, Evangelos Golias, Yousra Nahas, Sebastian Maria Ulrich Schultheis, Julian Skolaut, Marti Checa, Arundhati Ghosal, Jan Priessnitz, F. C. Fobasso Mbognou, Shashank Kumar Ojha, Shiyu Zhou, Alexander Qualls, Kai Litzius, Christoph Klewe, Peter Meisenheimer, Laurent Bellaiche, Libor Šmejkal, Darrell G. Schlom, Yimo Han, Sergei Prokhorenko, Ramamoorthy Ramesh, Paul Stevenson, Angela Wittmann, Lucas Caretta Affiliations: Northeastern University, Tel Aviv University, Cornell University, Czech Academy of Sciences, Rice University, Lawrence Berkeley National Laboratory, University of Arkansas, MAX IV Laboratory, University of California, Berkeley, Johannes Gutenberg-University Mainz, Brown University, Max Planck Institute for Chemical Physics of Solids, University of Augsburg, Oak Ridge National Laboratory, Leibniz-Institut für Kristallzüchtung, Max Planck Institute for the Physics of Complex Systems Link: http://arxiv.org/abs/2601.09970v1 Summary: This study employed short-circuit boundary conditions combined with an epitaxial strain strategy to stabilize a novel multiferroic phase in ultrathin BiFeO3 films with a thickness of only four unit cells, enabling simultaneous ferroelectricity and ferromagnetism at room temperature without a magnetically dead layer. First-principles calculations, spin symmetry analysis, atomic-resolution electron ptychography, and angle-resolved magnetic imaging revealed that the short-circuit electrostatic boundary condition in conjunction with epitaxial compressive strain drives a continuous second-order thickness-driven phase transition, transforming the film from a rhombohedral phase to a monoclinic Mc phase and forming a multiferroic topological texture. This texture also generates a time-reversal symmetry-breaking d-wave alternating magnetic signal, which was experimentally verified through magnetic circular dichroism spectroscopy. This discovery provides a viable pathway for realizing unconventional multiferroicity at device-relevant thicknesses, overcoming the functional limitations of vertical scaling in oxide electronics.\n7. Finite-momentum Cooper plasmons in superconducting terahertz microcavities Relevance Score: 3.4999 Authors: Alex M. Potts, Marios H. Michael, Gunda Kipp, Sara M. Langner, Hope M. Bretscher, Jonathan Stensberg, Kelson Kaj, Toru Matsuyama, Matthew W. Day, Felix Sturm, Abhay K. Nayak, Liam A. Cohen, Xiaoyang Zhu, Andrea Young, James McIver Affiliations: Columbia University, Center for Free-Electron Laser Science (CFEL), Max Planck Institute for the Structure and Dynamics of Matter Link: http://arxiv.org/abs/2601.10692v1 Summary: By integrating superconducting thin films into on-chip terahertz circuits, theoretical predictions and experimental confirmations have demonstrated that shielding phase modes can form superconducting microcavities, giving rise to finite-momentum standing-wave superfluid density resonances known as Cooper plasmons. Two Cooper plasmons were observed in NbN superconducting microcavities, with their resonance frequencies and linewidths independently reflecting the participating carrier density and dissipation at finite momentum, respectively. This study reveals emergent collective modes in integrated superconductor–circuit systems and establishes design principles for engineering or suppressing such plasmons, thereby providing a foundation for superconducting terahertz devices and circuits.\n8. Ultra-Stable Weyl Topology Driven by Magnetic Textures in the Shandite Compound Co3Sn2S(2-x)Sex Relevance Score: 3.4811 Authors: Dang Khoa Le, Eklavya Thareja, Bektur Konushbaev, Gina Pantano, Tom Saunderson, Manh-Huong Phan, Yuriy Mokrousov, Jacob Gayles Link: http://arxiv.org/abs/2601.09922v1 Summary: This study employs first-principles calculations to systematically investigate the magnetic structures and topological electronic properties of the Shandite family compounds Co₃Sn₂S₂, Co₃Sn₂SeS, and Co₃Sn₂Se₂. The results indicate that the magnetic configurations are primarily governed by exchange interactions and magnetocrystalline anisotropy, while the symmetry-allowed interlayer Dzyaloshinskii-Moriya interaction is negligible. A novel spin-chiral interaction arising from the topology of the kagome lattice is identified, which plays a dominant role in stabilizing the experimentally observed magnetic textures, with calculated SCI strengths of 0.78, 0.86, and 0.87 meV, respectively. Furthermore, it is found that short-wavelength magnetic textures can induce phase transitions of Weyl nodes: from type-I Weyl to type-II Weyl, and ultimately opening a band gap, leading to band flattening. Additionally, the calculated exchange stiffness coefficients and Curie temperatures align with experimental trends, and the magnetic anisotropy shows an easy axis perpendicular to the kagome plane. This newly discovered SCI and its associated electronic phase transitions provide new physical pathways for modulating transport properties in spintronic devices.\n9. Effects of Integrated Heatsinking on Superconductivity in Tantalum Nitride Nanowires at the 300 Millimeter Scale Relevance Score: 3.4607 Authors: Ekta Bhatia, Tharanga R. Nanayakkara, Chenyu Zhou, Tuan Vo, Wenli Collison, Jakub Nalaskowski, Stephen Olson, Soumen Kar, Hunter Frost, John Mucci, Brian Martinick, Ilyssa Wells, Thomas Murray, Corbet Johnson, Charles T Black, Mingzhao Liu, Satyavolu S Papa Rao Affiliations: NY Creates, Brookhaven National Laboratory, University at Albany (SUNY) Link: http://arxiv.org/abs/2601.10480v1 Summary: This study fabricated tantalum nitride (TaN) nanowires and TaN/copper (TaN/Cu) bilayer nanowires on 300 mm silicon wafers using a CMOS-compatible process, systematically evaluating the impact of integrated copper heat dissipation layers on superconducting performance. Through current-voltage curve hysteresis analysis and the Skocpol-Beasley-Tinkham (SBT) hot spot model, it was found that the copper layer enhanced the SBT slope parameter β and interfacial heat transfer efficiency by approximately 100 times, with the ratio of critical current to retrapping current approaching 1, confirming efficient heat dissipation capability. The zero-temperature Ginzburg-Landau coherence length of TaN nanowires was 7 nm, and the critical temperature was 4.1 K. Key parameters (critical dimensions, room-temperature resistance, residual resistance ratio, critical temperature, critical current) exhibited variations of less than 5% across the 300 mm wafer, demonstrating excellent process uniformity and scalability. These results indicate that TaN/Cu bilayer nanowires achieve a balance between superconducting performance and heat dissipation efficiency, providing a feasible pathway for wafer-scale fabrication of fast, large-area superconducting nanowire single-photon detector arrays, applicable in fields such as photonic quantum computing, cosmology, and neuromorphic computing.\n10. Superfluid Density, Penetration Depth, Condensate Density Relevance Score: 3.4603 Authors: Warren E. Pickett Link: http://arxiv.org/abs/2601.10578v1 Summary: This paper reviews the evolution of three concepts in superconductivity theory—superfluid density, penetration depth, and condensation density. The London theory introduced a linear relationship between superfluid density and penetration depth but did not provide a microscopic definition; the Ginzburg-Landau theory extended the expression for penetration depth through the order parameter and introduced a phase stiffness term; the BCS theory demonstrated that, at zero temperature, the penetration depth does not depend on particle density but rather on the density of states at the Fermi surface and the Fermi velocity. In the literature, superfluid density is often converted into a dimensionless normalized quantity to reflect the temperature dependence and symmetry of the energy gap, yet its absolute value is rarely provided. The author proposes and calculates the scalar superconducting electron condensation density, which is seldom discussed in conventional superconductors, and finds a simple relationship between it and the dynamic carrier density of the normal state at the critical temperature. Numerical examples of penetration depth and condensation density for several conventional superconductors are provided, clarifying the meaning of the term superfluid density in experimental analysis.\n11. Microwave Kerr/Faraday Resonance in Two-dimensional Chiral Superconductors Relevance Score: 3.4520 Authors: Taiki Matsushita, Jun\u0026rsquo;ichi Ieda, Yasufumi Araki, Takahiro Morimoto, Ilya Vekhter, Youichi Yanase Link: http://arxiv.org/abs/2601.10151v1 Summary: This study investigates the Kerr and Faraday effects in two-dimensional multi-band chiral superconductors, with a focus on the contribution of collective excitation modes—namely, the relative phase and amplitude oscillations between the two components of the chiral order parameter (clapping modes). Using the random phase approximation to calculate the optical conductivity tensor, it is found that these clapping modes lie within the quasiparticle excitation gap and exhibit long lifetimes (weak damping), dominating the magneto-optical response in the microwave frequency range. The Kerr and Faraday rotation angles show resonant enhancement as a function of optical frequency, with a sign reversal at the resonance point, and peak amplitudes ranging from 100 nrad to 10 μrad. Unlike single-band chiral superconductors, interband hybridization (e.g., sublattice transitions) in multi-band systems breaks translational invariance, allowing collective modes to couple efficiently to the optical field, thereby generating a transverse Hall response in the absence of an external magnetic field. This resonant signal lies below the quasiparticle excitation threshold, can be experimentally isolated, and is readily observable in candidate materials such as transition metal dichalcogenide bilayers and rhombohedral graphene. Therefore, microwave Kerr/Faraday resonance provides a universal and sensitive probe of time-reversal symmetry breaking in two-dimensional chiral superconductors.\n12. Basal-plane anisotropy of field-induced multipolar order in tetragonal CeRh$_2$As$_2$ Relevance Score: 3.4332 Authors: Konstantin Semeniuk, Burkhard Schmidt, Christophe Marcenat, Meike Pfeiffer, Albin Demuer, Lipsa Behera, Thierry Klein, Seunghyun Khim, Elena Hassinger Link: http://arxiv.org/abs/2601.10414v1 Summary: In the tetragonal compound CeRh₂As₂, the field-temperature phase diagrams for magnetic fields applied along the basal-plane [100] and [110] directions were investigated via resistivity and heat capacity measurements, revealing significant in-plane anisotropy: along [110], the transition temperature of phase I increases monotonically with increasing field, whereas along [100] it first decreases slightly and then rises rapidly at higher fields after entering phase II; the critical field of the phase I–II transition is 5.8 T and 8.4 T for [100] and [110], respectively. This anisotropy cannot be explained by simple dipolar magnetic order, because in a tetragonal system the in-plane dipolar components belong to the same irreducible representation and should exhibit isotropic field response. Combined with theoretical modeling, the results indicate the presence of a field-induced quasi-quartet state accompanied by coupling between antiferroquadrupolar and dipolar orders, which enhances the transition temperature and produces the observed anisotropy. While the existing model can partially describe the enhancement along [110], it fails to reproduce the experimental observations along [100], suggesting the need to further consider differences in quadrupolar component matrix elements, mixing of crystal electric field wavefunctions, and possible multipolar coupling mechanisms. These findings support the coexistence of magnetic and multipolar order in CeRh₂As₂, provide key constraints for understanding the pairing mechanism of its unconventional superconductivity, and guide the development of next-generation theoretical models.\n13. Ultra-low magnetization and hysteresis loss in APC Nb3Sn superconductors Relevance Score: 3.3873 Authors: X Xu, F Wan, X Peng, M Sumption Affiliations: The Ohio State University, Fermi National Accelerator Laboratory, Hyper Tech Research Incorporated Link: http://arxiv.org/abs/2601.09945v1 Summary: This study fabricated Nb3Sn superconducting wires with small sub-element dimensions containing artificial pinning centers (APC) via the internal oxidation method and investigated their workability. A 180-stack APC wire was successfully manufactured and drawn to diameters of 0.7 mm and 0.5 mm, corresponding to physical sub-element sizes (Dsub) of 34 μm and 24 μm (effective sub-element sizes Deff of 36 μm and 25 μm, respectively). Performance tests showed that the wire with Dsub of 34 μm exhibited a non-copper critical current density (Jc) above 13 T higher than that of the RRP wire used in the HL-LHC project (e.g., 36% higher at 4.2 K, 18 T), while its non-copper magnetization ΔM(1 T) at 1 T was only 29% of the RRP wire, and the non-copper hysteresis loss Qh(1–14 T) for a 1 T to 14 T cycle was 37% of the RRP value. The wire with Dsub of 24 μm surpassed the HL-LHC RRP wire in non-copper Jc above 17.5 T, with ΔM(1 T) and Qh(1–14 T) being only 17% and 23% of the RRP values, respectively. Additionally, its non-copper hysteresis loss for a ±3 T cycle met the ITER project specifications. These results indicate that APC wires achieve ultra-low magnetization and hysteresis loss through significantly reduced Jc at low fields and smaller effective sub-element sizes, while maintaining superior Jc performance at high fields, offering a key advantage for the sustainability of future collider magnets.\n14. Incipient modulated phase in Sr$_{1-x}$Ca$_{x}$TiO$_3$ Relevance Score: 3.2843 Authors: Benoît Fauqué, Daniel A. Chaney, Philippe Bourges, Stéphane Raymond, Arno Hiess, Paul Steffens, Benoît Baptiste, Luigi Paolasini, Alexeï Bosak, Kamran Behnia, Yasuhide Tomioka Link: http://arxiv.org/abs/2601.10516v1 Summary: Using inelastic neutron and X-ray scattering, this study reveals that in the ferroelectric Sr₁₋ₓCaₓTiO₃, dipolar fluctuations strongly couple with the c₄₄ transverse acoustic (TA) mode upon cooling, inducing its softening, and the maximum wavevector of this softening defines the characteristic length scale of nanoscale modulation. Calcium substitution enhances both the magnitude and wavevector of the softening by simultaneously strengthening ferroelectric and antiferrodistortive instabilities. Experiments demonstrate that in the modeled modulated state, nonlinear flexoelectric-phonon coupling tends to stabilize a modulation that cooperates with, rather than competes against, other lattice instabilities in SrTiO₃: in Ca-doped samples, TA mode softening intensifies with doping but does not lead to a static incommensurate order, instead manifesting as a dynamically modulated lattice instability. At the highest doping concentrations, the TA dispersion exhibits a \u0026ldquo;waterfall\u0026rdquo;-like behavior beyond mean-field flexoelectric theory. The study concludes that the quantum paraelectric phase of SrTiO₃ lies at the intersection of three lattice instabilities—ferroelectric, antiferrodistortive, and modulated—and its multiscale dynamic modulation structure (coexistence of short-range ferroelectric regions and extended modulation) provides a microscopic basis for understanding anomalous properties such as dielectric and thermal transport behavior, which can be tuned via strain, electric fields, and other means to design novel ferroic responses.\n15. Composite Bogoliubov Fermi liquid in a half-filled Chern band Relevance Score: 3.2465 Authors: Zhengyan Darius Shi, Pavel A. Nosov Link: http://arxiv.org/abs/2601.09924v1 Summary: In a zero-magnetic-field system with a half-filled Chern band, under conditions of inversion symmetry breaking and lattice rotational symmetry reduced to C3, composite fermions can form a superconducting state with a neutral gapless Bogoliubov Fermi surface via attractive interactions, termed the composite Bogoliubov Fermi liquid (CBFL). This phase exhibits incompressibility, quantized Hall conductance, and Pfaffian-like features such as topological ground-state degeneracy on a torus, while simultaneously displaying gapless metallic behaviors including linear specific heat, non-quantized thermal conductance, Landau damping of density fluctuations, and a $|\\mathbf{q}|^3$ non-analytic term in the equal-time structure factor, thereby distinguishing it from the conventional anomalous composite Fermi liquid (ACFL) and fully gapped Pfaffian phase. The theory is constructed based on the Ginzburg-Landau effective field theory, demonstrating that the local gauge field acquires mass via the Higgs mechanism, resulting in a single-electron gap, while quasiparticles on the neutral Bogoliubov Fermi surface contribute metallic thermodynamic and transport properties. This work provides a unified framework for understanding gapless topological phases induced by paired composite fermions in Chern bands beyond the Landau-level paradigm.\n16. Flat-band Ferromagnetism of SU$(N)$ Hubbard Model on the Kagome Lattices Relevance Score: 3.2170 Authors: Hao Jin, Wenxing Nie Link: http://arxiv.org/abs/2601.10549v1 Summary: This paper investigates the paramagnetic-ferromagnetic transition in the repulsive SU(N) Hubbard model on the Kagome lattice within a percolation framework. Utilizing the flat-band property, the model is rigorously mapped onto a classical N-state site percolation problem on a triangular lattice with nontrivial weights reflecting SU(N) symmetry. Through large-scale Monte Carlo simulations for SU(3), SU(4), and SU(10) symmetries, it is found that the critical particle density for ferromagnetism exceeds the standard percolation threshold and increases with N, indicating enhanced effective entropic repulsion. The simulation results reveal first-order transition characteristics with a critical density interval: as the density increases, the system sequentially undergoes a paramagnetic phase, a phase-separated regime with coexistence of macroscopic ferromagnetic domains and a paramagnetic background, and a fully percolated ferromagnetic phase. The study constructs the ground-state phase diagram and provides numerical evidence for the generalization of flat-band ferromagnetism in SU(N) systems.\n17. Comparison of SCAN+U and r2SCAN+U for Charge Density Wave Instability and Lattice Dynamics in CuTe Relevance Score: 3.0875 Authors: Seungha Ju, Sooran Kim Affiliations: Kyungpook National University Link: http://arxiv.org/abs/2601.10146v1 Summary: This study compares the descriptive capabilities of the meta-GGA functionals SCAN and r²SCAN (with/without Hubbard U) for charge density waves (CDW) in the quasi-one-dimensional material CuTe. By analyzing Te-Te bond modulations, phonon dispersions, and electronic structures, significant differences are found between the two functionals in capturing the structural and dynamical properties of CDW formation. r²SCAN+U reproduces the Te chain distortion in the CDW phase observed experimentally as well as the phonon soft mode at qCDW=(0.4,0.0,0.5) in the non-CDW phase, with atomic displacements of the soft mode consistent with experimental Te modulation; in contrast, SCAN exhibits unphysical phonon behavior. Although SCAN and r²SCAN are similar in electronic structure and optimized lattice constants, the results indicate that r²SCAN is more suitable than SCAN for describing CDW formation and lattice dynamics in CuTe.\n18. Classification and design of two-dimensional altermagnets Relevance Score: 3.0491 Authors: Sike Zeng, Dong Liu, Hongjie Peng, Chang-Chun He, Xiao-Bao Yang, Yu-Jun Zhao Link: http://arxiv.org/abs/2601.10183v2 Summary: According to spin group theory, this review provides a symmetry classification of two-dimensional altermagnets, categorizing them into d-wave, g-wave, and i-wave types, and systematically summarizes theoretically predicted candidate materials, with a particular emphasis on systems exhibiting large spin splitting. The core finding is that two-dimensional altermagnets, while maintaining zero net magnetization characteristic of antiferromagnets, display non-relativistic spin-polarized band structures akin to ferromagnets, with spin splitting protected by symmetry and amenable to modulation through various means. The article also outlines strategies for engineering two-dimensional altermagnetism, including stacking, multicomponent design, surface adsorption, electric field control, structural distortion, and strain. This review aims to integrate theoretical candidate materials with design routes to guide subsequent experimental realization, noting that the field remains predominantly theoretical with experimental validation lagging behind, yet two-dimensional systems, owing to their strong tunability and ease of integration, hold promise as a significant platform for spintronics.\n19. Hybrid superinductance with Al/InAs Relevance Score: 3.0225 Authors: Junseok Oh, Ido Levy, Tyler Cowan, Jacob Issokson, Archana Kamal, Javad Shabani, Andrew P. Higginbotham Link: http://arxiv.org/abs/2601.10023v1 Summary: We investigated a chain of Josephson junctions in an epitaxial Al/InAs heterostructure using microwave spectroscopy and found that its wave impedance exceeds the resistance quantum, thereby realizing superinductance. Due to the planar junction geometry, the devices exhibit extremely high plasma frequencies, and no deviation from ideal behavior due to dispersion is observed below 12 GHz. The internal quality factor decreases sharply with frequency, a trend well described by a simple resistively shunted junction model that predicts an inverse proportionality between quality factor and frequency, in agreement with experiments. No evidence of quantum phase slips is found experimentally, indicating that hybrid superinductance can overcome the performance limitations of conventional tunnel junctions. The loss may originate from intrinsic junction mechanisms in the diffusive limit, and short-junction devices exhibit higher quality factors due to larger Thouless energy. Although the current quality factors are limited, our devices are competitive for readout of spin qubits and parity qubits at intermediate frequencies, offering higher quality factors, smaller capacitance, and compact dimensions compared to conventional coil inductors.\n20. Trapping $\\tfrac{h}{2e}$ Flux in Metals Relevance Score: 3.0209 Authors: Zohar Komargodski, Fedor K. Popov Affiliations: Stony Brook University Link: http://arxiv.org/abs/2601.09847v1 Summary: This study investigates a novel phenomenon in the response of normal metals to localized magnetic flux. By self-consistently solving the coupled Schrödinger–Maxwell equations, the authors discover flux quantization effects in two geometric configurations—a metal disk pierced by a magnetic solenoid and a metal cylinder wrapped around the solenoid: due to the back-reaction of electrons, the metal ultimately traps a magnetic flux of either 0 or h/2e (half flux quantum). In the cylindrical geometry, analytical analysis reveals that the total flux decays exponentially to either 0 or half a flux quantum, with a capture length determined by the fine-structure constant and system dimensions. For a finite-sized disk, numerical calculations similarly demonstrate that the total magnetic flux is driven to either 0 or half a flux quantum, and this phenomenon is robust with respect to the initial solenoid flux. Moreover, when the solenoid is adiabatically switched off, a logarithmically enhanced local equilibrium current persists in the metal, concentrated near the solenoid, reflecting the perfect defect diamagnetism of the Fermi gas (i.e., a non-analytic dependence of the ground-state energy on external flux). These findings indicate that normal metals at mesoscopic scales can trap quantized magnetic flux analogously to superconductors, yet the underlying microscopic mechanism is fundamentally different from that of superconductivity.\n","permalink":"https://nickelates.uk/en/posts/2026-01-15-arxiv-daily/","summary":"\u003cblockquote\u003e\n\u003cp\u003e\u003cstrong\u003eDaily Overview\u003c/strong\u003e:\nDear readers, welcome to today\u0026rsquo;s overview of the latest papers in the field of nickelate superconductivity. Although the highlight works of today do not directly focus on nickelates, multiple papers are highly relevant to the core issues in the nickelate superconductivity field in terms of mechanisms, methods, or phenomena, making them worthy of close attention. For example, [5] reveals the critical role of correlated hopping interactions in driving superconducting phase transitions, providing a theoretical framework for understanding possible non-local correlation effects in nickelates; [11] proposes microwave Kerr/Faraday resonance as a sensitive probe for detecting time-reversal symmetry breaking in chiral superconductors, a technique that can be extended to the study of pairing symmetry in nickel-based superconductors; [12] reports the coexistence of magnetic and multipole orders and their constraints on superconducting pairing in CeRh₂As₂, offering analogies to the competition between spin fluctuations and superconductivity in nickelates; [14] uncovers multi-scale dynamic modulation structures in SrTiO₃, where lattice instability shares physical similarities with charge order and lattice coupling in nickelates; [15] constructs a theory of composite Bogoliubov Fermi liquids, providing a new paradigm for unconventional superconductivity in Chern bands, which may inspire theoretical exploration of topological superconducting states in nickelates. These works expand the understanding of strong correlations and unconventional superconductivity from different dimensions, offering research ideas and tools that can be applied to the nickelate superconductivity field.\n\u003cstrong\u003earXiv submission processing window\u003c/strong\u003e: 2026-01-14 20:07 to 2026-01-15 18:50 UTC.\u003c/p\u003e","title":"arXiv Daily: nickelate superconductors 2026-01-15"},{"content":" Daily Overview: Today\u0026rsquo;s highlights focus on deepening the understanding of the electronic structure of mixed Ruddlesden-Popper nickelates. [1] Polarization-resolved infrared spectroscopy reveals strong electrodynamic anisotropy induced by density-wave order in La₄Ni₃O₁₀, where the out-of-plane conductivity is sharply suppressed. The spin-density-wave order drives a redistribution of Ni-dz² orbital occupancy, effectively decoupling the Ni-O layers and significantly enhancing the two-dimensionality of the system. Additionally, [6] Monte Carlo simulations revisit the Jahn-Teller transition in correlated oxides, revealing that systems including layered nickelates (e.g., NaNiO₂) exhibit displacement-type transition characteristics. The behavioral differences between perovskites and layered nickelates arise from variations in lattice configurational entropy, offering new perspectives for understanding the structure-property relationships in nickelates. These two studies collectively advance the knowledge of electronic states and lattice dynamics in nickel-based superconductors and related systems. arXiv submission processing window: 2026-01-13 21:48 to 2026-01-14 19:00 UTC.\n1. Electronic layer decoupling driven by density-wave order in La$_4$Ni$_3$O$_{10}$ Relevance Score: 4.7620 Authors: Ziqiang Guan, Sophia F. R. TenHuisen, M. Tepie, Yifeng Zhao, Ezra Day-Roberts, Harrison LaBollita, Alexander M. Young, Xiaomeng Cui, Xinglong Chen, Filippo Glerean, Carl A. Guia, Mark P. M. Dean, Philip Kim, J. F. Mitchell, Antia S. Botana, Christopher C. Homes, Matteo Mitrano Link: http://arxiv.org/abs/2601.08997v1 Summary: Using polarization-resolved infrared spectroscopy, researchers probed the density wave phase transition in trilayer nickel oxide La₄Ni₃O₁₀. The results reveal that its low-energy electrodynamics exhibit strong anisotropy: metallic behavior in the in-plane direction but insulating character out-of-plane. In the ordered phase, the out-of-plane conductivity is sharply suppressed, leading to an increase in anisotropy by more than an order of magnitude. The authors attribute this enhancement to the redistribution of Ni-dz² orbital occupancy within the trilayer structure induced by spin density wave order, which effectively decouples the Ni-O interlayer electrons. Meanwhile, out-of-plane phonons display significant frequency shifts and splittings, consistent with features of electronically driven density wave instability. The study indicates that density wave order substantially reshapes the normal-state electronic properties of this nickel oxide and enhances its two-dimensional character.\n2. Electronic procrystalline state in moire structures Relevance Score: 4.2841 Authors: Hui Guo, Zihao Huang, Yixuan Gao, Haowei Chen, Hao Zhang, Qian Fang, Yuhan Ye, Xianghe Han, Zhongyi Cao, Jiayi Wang, Runnong Zhou, Zhilin Li, Chengmin Shen, Haitao Yang, Hui Chen, Wang Yao, Ziqiang Wang, Hong-Jun Gao Affiliations: Hefei National Laboratory, The University of Hong Kong, Boston College, University of Science and Technology Beijing, Chinese Academy of Sciences, University of Chinese Academy of Sciences Link: http://arxiv.org/abs/2601.09086v1 Summary: This study reports the first experimental observation of an electronic procrystalline state in an incommensurate moiré superlattice formed by monolayer metallic NiTe₂ and superconducting NbSe₂. This state exhibits long-range periodic charge modulation at the moiré scale, while within each moiré unit cell, a short-range disordered charge order with an approximate √3×√3 quasiperiodic structure emerges, a feature absent in pristine NiTe₂. Further experiments demonstrate that this electronic procrystalline order also persists in the superconducting state and coexists with the proximity-induced superconductivity. By tuning the thickness of NiTe₂, this electronic procrystalline state and its internal short-range charge order can be precisely modulated. This discovery reveals the potential of moiré platforms for understanding and controlling correlated quantum phases with such novel procrystalline order.\n3. Vanishing Phase Stiffness and Fluctuation-Dominated Superconductivity: Evidence for Inter-Band Pairing in UTe$_2$ Relevance Score: 4.2642 Authors: Sahas Kamat, Jared Dans, Shanta Saha, Daniel F. Agterberg, Johnpierre Paglione, B. J. Ramshaw Link: http://arxiv.org/abs/2601.09138v1 Summary: By measuring the elastic moduli and acoustic attenuation of UTe₂ under pressure via ultrasound, it is found that this heavy-fermion superconductor transitions from mean-field behavior at ambient pressure to a fluctuation-dominated state under high pressure, with the fluctuation region width comparable to the superconducting transition temperature T_c, making it the largest among known three-dimensional superconductors. At high pressure, the elastic modulus softens above T_c, and the acoustic attenuation remains anomalously high deep within the superconducting state—features attributed to an extremely low superfluid phase stiffness, resulting in a kinetic inductance in the clean limit comparable to that of granular aluminum. Analysis indicates that this exotic state is dominated by interband pairing mediated by ferromagnetic fluctuations, forming local Cooper pairs with coherence lengths of only a few lattice constants, whereas the SC1 phase retains conventional mean-field behavior. These findings provide crucial experimental evidence for understanding the multiple superconducting phases and pairing mechanisms in UTe₂.\n4. Quasiparticle to local moment crossover in bad metals Relevance Score: 4.0902 Authors: A. Chen, F. B. Kugler, P. Doležal, Y. Saito, A. Kawamoto, A. Georges, A. Pustogow Link: http://arxiv.org/abs/2601.09420v1 Summary: Through NMR and transport experiments, this study directly correlates the deviation from the Korringa law with the deviation of resistivity from Fermi liquid behavior (ρ_FL) in the organic conductor κ-[(BEDT-STF)x(BEDT-TTF){1-x}]_2Cu_2(CN)_3. From spin-lattice relaxation rate data, a gradual crossover from low-temperature quasiparticle-dominated to high-temperature localized magnetic moments is identified, and dynamical mean-field theory calculations accurately reproduce the transport data, revealing the manifestation of this crossover in the temperature evolution of the quasiparticle spectrum. For samples near the Mott insulator with dρ/dT\u0026lt;0 in the high-temperature region, Einstein relation analysis indicates that the bad-metal behavior with dρ/dT\u0026gt;0 primarily originates from the temperature dependence of the electronic compressibility rather than the diffusion constant.\n5. Nanoscale Spatial Tuning of Superconductivity in Cuprate Thin Films via Direct Laser Writing Relevance Score: 4.0892 Authors: Irene Biancardi, Valerio Levati, Jordi Alcalà, Thomas Günkel, Nicolas Lejeune, Alejandro V. Silhanek, Valeria Russo, Narcís Mestres, Daniela Petti, Anna Palau, Edoardo Albisetti Affiliations: Politecnico di Milano, ICMAB-CSIC, Universitat Autònoma de Barcelona, Université de Liège Link: http://arxiv.org/abs/2601.09513v1 Summary: This paper presents a nanoscale superconducting modulation method based on direct laser writing, which precisely tailors the superconducting transport and optical properties of YBa₂Cu₃O₇⁻δ (YBCO) thin films through maskless laser scanning under ambient atmospheric conditions to locally control the oxygen stoichiometry. By employing a 405 nm continuous-wave laser, multi-gray-scale patterning with sub-micrometer resolution is achieved. Scanning electron microscopy and electrostatic force microscopy reveal surface potential variations associated with oxygen deficiency in the patterned regions. Low-temperature magneto-optical imaging and transport measurements directly demonstrate spatial tuning of the critical temperature and carrier density with laser power, where higher laser power results in lower superconducting transition temperatures. Raman spectroscopy and reflectivity measurements confirm oxygen removal in the irradiated areas. This method enables rapid and scalable phase diagram modulation over large areas while avoiding material damage typically caused by conventional nanofabrication, thereby offering a new pathway for constructing high-performance superconducting functional nanostructures.\n6. Revisiting Jahn\u0026ndash;Teller Transitions in Correlated Oxides with Monte Carlo Modeling Relevance Score: 4.0605 Authors: Liam A. V. Nagle-Cocco, Andrew L. Goodwin, Clare P. Grey, Siân E. Dutton Link: http://arxiv.org/abs/2601.09705v3 Summary: This study revisits the Jahn-Teller transition in correlated oxides using Monte Carlo simulations with a simple Hamiltonian incorporating the JT amplitude ρ, where ρ is varied through the Metropolis algorithm. The simulation results reveal that the JT amplitude distribution in both perovskites (e.g., LaMnO₃) and layered nickelates (e.g., NaNiO₂) exhibits characteristics of a displacive transition rather than the traditionally assumed order-disorder type. This finding suggests that displacive JT transitions may be more common than previously hypothesized. Additionally, significant differences in transition behavior between perovskites and layered nickelates are observed, which are attributed to differences in the extensiveness of configurational entropy in the two lattice geometries, thereby highlighting the critical role of lattice geometry in determining the nature of the transition.\n7. Evolution from three-dimensional charge density wave to one-dimensional stripe order in CsV$_{3-x}$Ti$_x$Sb$_5$ Relevance Score: 3.9367 Authors: Qian Xiao, Xiangqi Liu, Zihao Huang, Xiquan Zheng, Shilong Zhang, Hui Chen, Hong-Jun Gao, Yanfeng Guo, Yingying Peng Affiliations: Collaborative Innovation Center of Quantum Matter, Peking University, Chinese Academy of Sciences, Guangdong University of Education, University of Chinese Academy of Sciences, ShanghaiTech University Link: http://arxiv.org/abs/2601.09257v1 Summary: By combining X-ray diffraction and scanning tunneling microscopy, this study reveals the dimensional evolution of charge density waves under titanium doping in the kagome metal CsV₃₋ₓTiₓSb₅. It is found that even an extremely small amount of titanium doping (x=0.009) can completely suppress the three-dimensional 2×2×4 charge density wave in the parent phase, reducing the remaining 2×2×2 charge density wave to quasi-two-dimensional order. Upon further increasing the titanium content to x=0.2, although no signature of charge density wave transition is observed in resistance measurements, diffraction and scanning tunneling microscopy data indicate the emergence of a (quasi-)one-dimensional stripe-like charge density wave with a short correlation length of about 20 Å, which undergoes a continuous second-order phase transition below approximately 56 K, with its intensity and correlation length gradually increasing as temperature decreases. These results elucidate the continuous dimensional evolution of charge density waves in CsV₃₋ₓTiₓSb₅, offering new insights into unconventional charge density waves and their interplay with superconductivity in kagome superconductors.\n8. Highly efficient superconducting diode effect in unconventional $p$-wave magnets Relevance Score: 3.8525 Authors: Igor de M. Froldi, Hermann Freire Link: http://arxiv.org/abs/2601.09783v1 Summary: This study systematically analyzes the formation of zero-momentum and finite-momentum superconducting phases in unconventional p-wave magnets using Ginzburg-Landau theory. The results show that although these magnetic phases can coexist with conventional pairing states at zero magnetic field, the Fulde-Ferrell (FF) phase generally becomes the dominant instability when a finite magnetic field is applied. By calculating the superconducting diode effect (SDE) efficiency of this finite-momentum pairing state, it is found that for experimentally relevant spin-splitting parameters, the system can achieve highly efficient nonreciprocal transport approaching 100%. The phase diagram reveals that the spin splitting of the p-wave magnet enhances the Pauli limit field, while the modulation wave vector of the FF phase is oriented along the antinodal direction, with efficiency monotonically increasing as temperature decreases. For candidate materials predicted by density functional theory, such as LaFeAsO and CeNiAsO, their spin-splitting ranges precisely correspond to the region of highest SDE efficiency. Therefore, these new materials provide an ideal platform for constructing energy-efficient logic circuits for classical and quantum computing.\n9. Unexpected type-II multiferroic phase in GdMnO3 under high magnetic fields Relevance Score: 3.6862 Authors: Ming Yang, Jun Chen, Junfeng Wang, Chao Dong, Chengliang Lu, Gang Xu, Jinguang Cheng, Jianshi Zhou, Shuai Dong Affiliations: University of Texas at Austin, Chinese Academy of Sciences, Southeast University, Huazhong University of Science and Technology Link: http://arxiv.org/abs/2601.09092v1 Summary: In a high-field study of GdMnO₃ single crystals, a previously unknown hidden phase was revealed using pulsed magnetic fields (up to 60 T) combined with multi-probe experiments including magnetization, electric polarization, and magnetostriction. This phase exhibits a giant magnetic-field-induced electric polarization of up to 1500 μC/m² and displays a continuous non-monotonic transition sequence of polar-nonpolar-polar-nonpolar during the up-sweep field process, enabling the construction of a complete magnetoelectric phase diagram. Simulations based on a classical spin model successfully reproduce this phase transition behavior, indicating that spin-lattice coupling is a key factor in generating this reentrant ferroelectric phase. This discovery not only extends the understanding of high-field behavior in perovskite multiferroic materials but also reveals the existence of previously unrecognized multiferroic phases in a system that has been studied for more than two decades.\n10. Chemical heterogeneity at conducting ferroelectric domain walls Relevance Score: 3.5393 Authors: Kasper A. Hunnestad, Guo-Dong Zhao, Mao-Hua Zhang, Tiannan Yang, Elzbieta Gradauskaite, Antonius T. J. van Helvoort, Morgan Trassin, Long-Qing Chen, Tadej Rojac, Dennis Meier Affiliations: University of Duisburg-Essen, Research Alliance Ruhr, Jožef Stefan Institute, ETH Zurich, Université Paris-Saclay, Norwegian University of Science and Technology (NTNU), The Pennsylvania State University Link: http://arxiv.org/abs/2601.09323v2 Summary: This study quantitatively analyzed the microscopic conduction mechanisms of 109° domain walls in the ferroelectric model system BiFeO₃ by combining conductive atomic force microscopy (cAFM) and atom probe tomography (APT). Experimental results revealed significant chemical heterogeneity at the domain walls: the types and concentrations of point defects—including accumulation or depletion of oxygen vacancies (V_O), bismuth vacancies (V_Bi), and iron vacancies (V_Fe)—varied substantially across different domain walls and even at different positions within the same domain wall, with variations exceeding 0.4 at.% and defect types switching rapidly at the nanometer scale. Such extreme chemical flexibility leads to spatially inhomogeneous conduction behavior, where distinct regions may rely on mechanisms such as modifications to the band structure or intermediate energy levels introduced by point defects. The findings indicate that multiple conduction mechanisms can coexist within a single domain wall, providing a unified framework for interpreting the diverse electronic behaviors reported previously and establishing the fundamental concept that the chemical composition of domain walls is directly correlated with their electrical properties.\n11. Coexistence of long-range magnetic order and dynamical magnetism in the V-based Kagome metals: A combined thermodynamic and $μ$SR study Relevance Score: 3.4252 Authors: Sheetal Devi, Yishui Zhou, Thomas J. Hicken, Zurab Guguchia, Hubertus Luetkens, Min-Kai Lee, Lieh-Jeng Chang, Yixi Su Link: http://arxiv.org/abs/2601.09046v1 Summary: Through combined heat capacity and muon spin relaxation (μSR) measurements, the low-temperature magnetic behavior of V-based Kagome metal single crystals RV₆Sn₆ (R = Tb, Dy, Ho, Er) was systematically investigated. Heat capacity data indicate clear long-range magnetic ordering phase transitions below 4 K for all compounds. However, μSR results reveal persistent spin fluctuations down to 50 mK within the magnetically ordered state, while the magnetic moments derived from hyperfine analysis of heat capacity are significantly lower than those of free R³⁺ ions, further confirming the presence of spin dynamics. These findings unveil the coexistence of static long-range magnetic order and dynamic magnetism in V-based Kagome metals, highlighting the crucial role of 4f electron anisotropy in shaping the magnetic ground state. Compared with Mn-based analogs RMn₆Sn₆, this system exhibits unique magnetic properties arising from the decoupling of the rare-earth sublattice from the nonmagnetic V Kagome network.\n12. Disorder-induced strong-field strong-localization in 2D systems Relevance Score: 3.3439 Authors: Yi Huang, Sankar Das Sarma Link: http://arxiv.org/abs/2601.09687v2 Summary: Recent STM experiments have directly observed three filling-factor-dependent quantum phases at the lowest Landau level in two-dimensional bilayer graphene: an incompressible fractional quantum Hall liquid, a compressible Wigner crystal with long-range hexagonal order and rotational symmetry breaking, and a randomly localized solid phase without spatial order. This paper demonstrates that the random localized phase at low filling corresponds to the recently proposed disorder-dominated strongly localized amorphous \u0026ldquo;Anderson solid\u0026rdquo; phase, which emerges at sample-dependent filling factors. To explain the transition to this phase, the authors adopt a strong localization approach that considers only disorder while neglecting interactions, calculating Landau level broadening using the self-consistent Born approximation, and derive a critical filling factor formula by equating the level broadening to the effective chemical potential. This formula qualitatively agrees with results from extremely disordered silicon MOS systems and clean bilayer graphene samples, indicating that when disorder is sufficiently strong, the entire lowest Landau level consists of localized states, preventing the formation of fractional quantum Hall effects or Wigner crystals. The study suggests that the gradual crossover from Wigner crystal to amorphous solid is more consistent with disorder-induced Anderson localization rather than pinning effects of the Wigner crystal, offering a new theoretical perspective for understanding disorder-induced strong localization in two-dimensional systems under high magnetic fields.\n13. Submicrometer tunnel ferromagnetic Josephson junctions with transmon energy scale Relevance Score: 3.3109 Authors: R. Satariano, R. Ferraiuolo, F. Calloni, H. G. Ahmad, D. Gatta, F. Tafuri, A. Bruno, D. Massarotti Link: http://arxiv.org/abs/2601.09591v1 Summary: We have fabricated submicron tunnel ferromagnetic Al/AlOₓ/Al/Ni₈₀Fe₂₀/Al Josephson junctions for qubit applications using the Manhattan process, with energy scales designed for the transmon regime. The current–voltage characteristics of these junctions are comparable to those of standard junctions in state-of-the-art transmons, confirming the high device quality and marking a critical step toward ferromagnetic transmons. Low-frequency characterization indicates that these junctions operate within the quantum phase diffusion limit, similar to conventional tunnel junctions with comparable characteristic energies. The results demonstrate that the ferromagnetic layer introduces no adverse effects on the DC transport properties, and application of a magnetic field further reveals that the superconducting branch resistance originates from the modulation of the binding energy by quantum phase fluctuations. Ultimately, mitigating quantum phase fluctuations is of key importance for advancing superconductor quantum circuit architectures.\n14. Spatially resolved collective modes in d-wave superconductors Relevance Score: 3.3002 Authors: Kazi Ranjibul Islam, Samuel Awelewa, Andrey V. Chubukov, Maxim Dzero Link: http://arxiv.org/abs/2601.09782v1 Summary: Using diagrammatic techniques and quasiclassical theory in the Keldysh-Nambu formalism, this paper analyzes the collective excitation modes of the d-wave superconducting order parameter in the presence of long-range Coulomb interactions. It is found that at zero temperature, the dispersion of the transverse mode (plasmon mode) is identical to that in s-wave superconductors; however, at finite temperatures, due to partial screening of the Coulomb potential by nodal quasiparticles, the transverse mode becomes softer and its damping rate increases significantly. The dispersion of the longitudinal mode depends on the momentum direction relative to the positions of the d-wave gap nodes, whereas its damping rate is momentum-independent. These results are of significant importance for understanding the anisotropic behavior of collective excitations in d-wave superconductors and for experimental observations.\n15. Viewpoint: On the Emergence of van der Waals Magnets: A Personal Reflection Relevance Score: 3.2590 Authors: Je-Geun Park Affiliations: Seoul National University Link: http://arxiv.org/abs/2601.09759v1 Summary: The observation of magnetic order in the van der Waals antiferromagnets FePS₃, NiPS₃, and MnPS₃ at the monolayer limit in 2016 marked a significant milestone in the field of two-dimensional physics. This article provides a personal perspective on the journey of this discovery, which originated from a seemingly simple question in the early 2010s: Can monolayer magnets sustain a (anti)ferromagnetic ground state? Amidst skepticism from the Mermin-Wagner theorem regarding the stability of long-range order in two dimensions, the research team selected transition metal phosphorus trisulfides (TMPS₃) as a platform due to their ease of exfoliation and ability to realize Ising, XY, and Heisenberg spin models. After years of effort, antiferromagnetic order was first confirmed in monolayer FePS₃ in 2016, consistent with Onsager\u0026rsquo;s solution for the two-dimensional Ising model. Subsequently, the discovery of ferromagnets such as Cr₂Ge₂Te₆ and CrI₃ in 2017 further established the universality of van der Waals magnetic materials. Since then, the field has rapidly expanded to include topological magnets, multiferroics, air-stable monolayer ferromagnets, and emerging helical textures in moiré engineering. The author summarizes three key insights: unfashionable seeds can grow, persistence is crucial, and skepticism drives cleaner experiments. The core conclusion is that the first decade (2016–2025) has demonstrated the existence of two-dimensional magnetism, while the next decade will focus on precise control, coupling, and integration, incorporating magnetism into the van der Waals toolkit alongside charge and valley degrees of freedom.\n16. Interactions of composite magnetic skyrmion-superconducting vortex pairs in ferromagnetic superconductors Relevance Score: 3.2242 Authors: Paul Leask, Calum Ross, Egor Babaev Link: http://arxiv.org/abs/2601.09396v1 Summary: This paper employs the Ginzburg-Landau theoretical framework to systematically investigate composite topological excitations (SVP) formed by magnetic skyrmions and superconducting vortex bound states in ferromagnetic superconductors, considering the Zeeman coupling between magnetization and the superconducting magnetic field. The study reveals that SVP can form energetically stable bound states, with their asymptotic interactions exhibiting a competition between short-range repulsion and long-range attraction, leading to aggregation phenomena. Numerical simulations demonstrate that the interaction forces between SVPs are orientation-dependent, enabling the formation of stable bound pairs at specific relative rotation angles. Through linearization analysis, the paper determines the characteristic decay lengths of the asymptotic forms of the superconducting order parameter, gauge field, and magnetization, revealing that the interactions are governed by the decay lengths of transverse magnetization perturbations and superconducting modes. These findings provide a field-theoretic foundation for understanding and controlling the long-range interactions of hybrid topological matter, and offer theoretical support for quantum computing platforms such as Majorana bound states.\n17. RKKY signatures as a probe for intrinsic magnetism and AI/QAH phase discrimination in MnBi$_2$Te$_4$ films Relevance Score: 3.1964 Authors: Ya-Xi Li, Zi-Jian Chen, Rui-Qiang Wang, Ming-Xun Deng, Hou-Jian Duan Link: http://arxiv.org/abs/2601.09303v2 Summary: This work systematically investigates the behavior of the RKKY interaction in MnBi₂Te₄ thin films under both dark and circularly polarized light illumination, aiming to utilize it as a probe to distinguish intrinsic magnetism, the axion insulator (AI) phase, and the quantum anomalous Hall (QAH) insulator phase. Under dark conditions, intrinsic magnetism gives rise to a more anisotropic RKKY spin model compared to nonmagnetic topological insulators, thereby providing distinguishing features; meanwhile, key band properties such as the energy gap, band degeneracy/splitting, and Fermi surface topological deformation leave distinct imprints on the RKKY interaction, enabling clear discrimination between even-layer (AI phase) and odd-layer (QAH phase) films through the Fermi energy dependence or spatial oscillation of coplanar impurities, or the presence or absence of spin frustration terms for non-coplanar impurities. Under off-resonant circularly polarized light, additional phase transition fingerprints emerge: the sign reversal of the spin frustration term in even-layer films and the chiral-selective double-valley structure of the collinear RKKY component in odd-layer films further enhance the discrimination capability. This work establishes the RKKY interaction as a sensitive magnetic probe capable of effectively distinguishing between the AI and QAH phases, thereby complementing conventional electrical transport measurements and providing new insights into the influence of intrinsic magnetism on the band structure of surface states.\n18. Electronic structure and elasticity of the Ta-W solid solution Relevance Score: 3.1133 Authors: Kareem Abdelmaqsoud, John R. Kitchin, Michael Widom Link: http://arxiv.org/abs/2601.09690v1 Summary: Through density functional theory calculations, this paper systematically investigates the relationship between electronic structure and elastic constants in Ta-W binary solid solutions. It is found that the shear modulus exhibits a slope anomaly near the equiatomic ratio as tungsten content varies, which coincides with a sharp change in the density of states at the Fermi level. Using crystal orbital Hamilton population analysis, the variation in d-orbital bonding and antibonding interactions between neighboring atoms with valence electron count is revealed: at low tungsten content, electron filling of bonding orbitals enhances the shear modulus, but next-nearest-neighbor antibonding interactions suppress its growth; when the valence electron count exceeds 5.5, both bonding and antibonding strengths weaken, leading to a flattening of the shear modulus trend while the bulk modulus continues to rise. Wave function analysis indicates that differences in orbital symmetry under various deformation modes explain the origin of elastic anisotropy. This electronic structure mechanism also applies to other alloy systems in Groups V and VI, where the Pugh\u0026rsquo;s ratio peaks near the equiatomic ratio, suggesting that tantalum-rich alloys are more ductile than tungsten-rich alloys. This study provides an electronic-level explanation for understanding the brittle-to-ductile transition in transition metal alloys.\n19. The Diffusion Kinetics of Ba Cations in Perovskite BaTiO$_3$: A Combined Tracer Diffusion and Metadynamics Study Relevance Score: 3.0709 Authors: Sylvia Koerfer, Bianca Dißmann, Norman Schier, Han-Ill Yoo, Manfred Martin, Roger A. De Souza Affiliations: Seoul National University, RWTH Aachen University Link: http://arxiv.org/abs/2601.09344v1 Summary: This study combines tracer diffusion experiments with metadynamics (MtD) simulations to investigate the diffusion behavior of Ba cations in cubic-phase perovskite BaTiO₃. Experimentally, ¹³⁰BaTiO₃ thin films were used as diffusion sources, and single-crystal samples were annealed in the temperature range of 1348–1498 K, with the diffusion profiles of ¹³⁰Ba determined by time-of-flight secondary ion mass spectrometry (ToF-SIMS) to obtain the Ba tracer diffusion coefficients (DBa). MtD simulations calculated the diffusion coefficients of Ba vacancies (DvBa) under various vacancy mechanisms, revealing that adjacent oxygen vacancies significantly enhance DvBa, while neighboring titanium vacancies have an even more pronounced effect. A comprehensive comparison of DBa and DvBa results indicates that Ba diffusion in the samples most likely occurs through the migration of defect associates rather than the migration of isolated Ba vacancies. Additionally, this study highlights the potential risks of relying solely on activation enthalpy to interpret diffusion data.\n20. Ferroelectric polarization mapping through pseudosymmetry-sensitive EBSD reindexing Relevance Score: 3.0083 Authors: Claire Griesbach, Tizian Scharsach, Morgan Trassin, Dennis M. Kochmann Affiliations: ETH Zürich Link: http://arxiv.org/abs/2601.09627v1 Summary: This study developed a simulated pattern matching-based electron backscatter diffraction (EBSD) re-indexing technique for mapping local polarization directions in ferroelectric materials. To address the challenge that the extremely small unit cell aspect ratio in ferroelectrics results in highly similar Kikuchi diffraction patterns from different polarization domains, the paper proposes an improved preprocessing workflow, including optimized pattern processing, a pseudosymmetry-sensitive neighborhood pattern averaging method, and global sample-detector geometry calibration based on digital image correlation. Additionally, a new pseudosymmetry confidence index is introduced, which not only evaluates pattern similarity but also considers the trend of dissimilarity with patterns of other domain variants. Using barium titanate single crystals and lead zirconate titanate polycrystals as model systems, the method successfully distinguished six polarization directions, with single-crystal results validated by piezoresponse force microscopy. The paper notes that this technique is applicable not only to ferroelectrics but also to any material exhibiting crystallographic pseudosymmetry, thereby extending the capability of EBSD for fine orientation analysis.\n","permalink":"https://nickelates.uk/en/posts/2026-01-14-arxiv-daily/","summary":"\u003cblockquote\u003e\n\u003cp\u003e\u003cstrong\u003eDaily Overview\u003c/strong\u003e:\nToday\u0026rsquo;s highlights focus on deepening the understanding of the electronic structure of mixed Ruddlesden-Popper nickelates. [1] Polarization-resolved infrared spectroscopy reveals strong electrodynamic anisotropy induced by density-wave order in La₄Ni₃O₁₀, where the out-of-plane conductivity is sharply suppressed. The spin-density-wave order drives a redistribution of Ni-dz² orbital occupancy, effectively decoupling the Ni-O layers and significantly enhancing the two-dimensionality of the system. Additionally, [6] Monte Carlo simulations revisit the Jahn-Teller transition in correlated oxides, revealing that systems including layered nickelates (e.g., NaNiO₂) exhibit displacement-type transition characteristics. The behavioral differences between perovskites and layered nickelates arise from variations in lattice configurational entropy, offering new perspectives for understanding the structure-property relationships in nickelates. These two studies collectively advance the knowledge of electronic states and lattice dynamics in nickel-based superconductors and related systems.\n\u003cstrong\u003earXiv submission processing window\u003c/strong\u003e: 2026-01-13 21:48 to 2026-01-14 19:00 UTC.\u003c/p\u003e","title":"arXiv Daily: nickelate superconductors 2026-01-14"},{"content":" Daily Overview: In today\u0026rsquo;s overview of papers on nickel-based superconductivity, there is no study directly centered on nickelates, but a theoretical work on graphene superconductivity is closely related to current hot topics in nickel-based superconductivity. Using the self-consistent Bogoliubov–de Gennes method, this work reveals how the \u0026ldquo;kinetic blocking\u0026rdquo; mechanism in strain-engineered graphene leads to the formation of quasi-one-dimensional filamentary structures of the superconducting order parameter at geometric nodes, presenting a pairing density wave state with sign reversal. This mechanism provides a theoretical framework for understanding the recently observed filamentary superconductivity in nickelate thin films, indicating that strain gradients can achieve spatial selectivity of the superconducting state by decoupling internal degrees of freedom, thereby expanding our understanding of quantum phase modulation with geometric origins. arXiv submission processing window: 2026-01-12 22:51 to 2026-01-13 19:32 UTC.\n1. Kinetic Blockade and Filamentary Pair Density Waves in Strain-Engineered Graphene Relevance Score: 4.0025 Authors: Tao Zhou Link: http://arxiv.org/abs/2601.08586v1 Summary: Using the self-consistent Bogoliubov–de Gennes method to investigate superconductivity in strain-engineered graphene, a \u0026ldquo;kinetic blocking\u0026rdquo; mechanism is revealed: the strain-induced pseudomagnetic field leads to sublattice polarization, spatially separating the electronic wave functions, thereby suppressing the enhancement of pairing by the high density of states in flat-band regions and preventing the formation of superconducting condensates there. Conversely, the superconducting order parameter is significantly enhanced at geometric nodes, forming quasi-one-dimensional filamentary structures and exhibiting a sign-alternating pairing density wave state that preserves time-reversal symmetry. Nonmagnetic impurities in this PDW state induce zero-energy resonant peaks, which can serve as key signatures for experimental detection. This study shows that strain gradients achieve spatial selectivity of the superconducting state by decoupling internal degrees of freedom (such as graphene’s A/B sublattices), offering a theoretical framework for understanding the filamentary superconductivity recently observed in nickelate thin films and revealing the unique geometric origin of strain engineering in modulating quantum phases of Dirac materials.\n2. Nodal Superconductivity of UTe$_2$ Probed by Field-Angle-Resolved Specific Heat on a Crystal with $T_{\\rm c}=2.1$ K Relevance Score: 3.8234 Authors: Kaito Totsuka, Yohei Kono, Yusei Shimizu, Ai Nakamura, Atsushi Miyake, Dai Aoki, Yasumasa Tsutsumi, Kazushige Machida, Shunichiro Kittaka Link: http://arxiv.org/abs/2601.08201v2 Summary: Researchers performed field-angle-resolved specific heat measurements on high-quality single crystals of the spin-triplet superconductor UTe₂ with a critical temperature of 2.1 K. The experimental results show that when the magnetic field is precisely aligned along the b-axis, the low-temperature specific heat increases linearly with the field, in stark contrast to the rapid rise in specific heat at low fields in other directions. This pronounced anisotropy indicates that the Fermi velocity of nodal quasiparticle excitations is predominantly along the b-axis. Combining the characteristic field-angle dependence of the specific heat and the upper critical field, the experimental results qualitatively agree with two theoretical models: one featuring a point-node superconducting gap structure with B₂u symmetry under a strong spin-orbit coupling scenario, and the other a line-node structure with B₃u symmetry under a finite spin-orbit coupling classification, where the line nodes are confined to the flat regions of a quasi-two-dimensional Fermi surface. These findings provide crucial thermodynamic evidence for determining the pairing symmetry of UTe₂, contributing to a deeper understanding of its spin-triplet superconductivity.\n3. Vacuum-dressed superconductivity in NbN observed in a high-$Q$ terahertz cavity Relevance Score: 3.6631 Authors: Hongjing Xu, Andrey Baydin, Qinyan Yi, I-Te Lu, Ningxu Zhu, T. Elijah Kritzell, Jacques Doumani, Dasom Kim, Fuyang Tay, Angel Rubio, Junichiro Kono Affiliations: Rice University Link: http://arxiv.org/abs/2601.08191v1 Summary: This study experimentally observed, using terahertz time-domain spectroscopy, that the superconductivity of niobium nitride thin films is modified by quantum vacuum electromagnetic fluctuations in a high-quality-factor one-dimensional photonic crystal cavity without an external driving field. By comparing the optical responses of the films in free space and within the cavity, significant cavity-induced changes in optical conductivity were detected. Theoretical modeling indicates that these changes originate from a reduction of approximately 13% in superfluid density and a slight decrease of about 2% in the superconducting energy gap due to vacuum fluctuations. This work directly demonstrates that quantum vacuum fluctuations in a dark cavity can non-intrusively manipulate the ground-state properties of BCS superconductors, providing an experimental platform for engineering material ground states via vacuum-matter coupling and opening a new frontier in cavity material science.\n4. Bound States from Berry Curvature and Chiral Superconductivity Relevance Score: 3.5083 Authors: Daniil Karuzin, Zhiyu Dong, Leonid Levitov Affiliations: Landau Institute for Theoretical Physics Link: http://arxiv.org/abs/2601.08055v2 Summary: This study investigates the two-body problem in electronic bands with Berry curvature and reveals that it supports chiral non-s-wave bound states (nonzero angular momentum). In the presence of a Fermi sea, these interactions give rise to chiral pairing problems, resulting in multiple superconducting phases that break time-reversal symmetry and form cascading chiral topological states with different angular momenta, where the phase of the order parameter winds around the Fermi surface by 2πm (m = 1, 3, 5, \u0026hellip;). The sequence of phase transitions is governed by the Berry curvature flux Φ = b k_F² / 2; as Φ increases, the system undergoes a series of first-order phase transitions that are nearly periodic with period 2 in Φ, realizing a quantum geometric analogue of the Little-Parks effect—oscillations in the critical temperature Tc. This work reveals how Berry curvature fundamentally reshapes superconducting pairing, producing experimentally detectable signatures of chiral superconducting order.\n5. Large room temperature anomalous Nernst effect coupled with topological Nernst effect from incommensurate spin structure in a Kagome antiferromagnet Relevance Score: 3.4739 Authors: Jiajun Ma, Jiaxing Liao, Yazhou Li, Yuwei Zhang, Jialu Wang, Jinke Bao, Yan Sun, Shuang Jia, Yuke Li Affiliations: Hangzhou Normal University, Chinese Academy of Sciences, Peking University Link: http://arxiv.org/abs/2601.08239v1 Summary: In the Kagome antiferromagnet ErMn₆Sn₆, through single-crystal growth and transport measurements, the research team observed an anomalous Nernst effect (ANE) as large as approximately 1.3 μV K⁻¹ at room temperature, comparable to the highest values reported in known magnetic materials, originating from strong Berry curvature in momentum space (Chern-gapped Dirac fermions). More surprisingly, a significant topological Nernst effect (TNE) coexists in the helical antiferromagnetic state, detectable at room temperature and peaking at about 0.2 μV K⁻¹ at 180 K, with its origin attributed to a non-zero real-space scalar spin chirality arising from the incommensurate spin structure along the c-axis. This work not only reveals the mechanism of the coexistence of anomalous and topological transverse thermoelectric effects in incommensurate antiferromagnetic systems, but also demonstrates the potential for room-temperature thermoelectric applications based on the Nernst effect, providing an important platform for developing new thermoelectric materials and understanding transport in topological spin textures.\n6. Nodal-line-enhanced quantum geometric effects: anomalous and nonlinear Hall effects in the parity-mixed antiferromagnet NbMnP Relevance Score: 3.3741 Authors: Ibuki Terada, Vu Thi Ngoc Huyen, Yuki Yanagi, Michi-To Suzuki Affiliations: Osaka University, Tohoku University, Osaka Metropolitan University, Toyama Prefectural University Link: http://arxiv.org/abs/2601.08317v1 Summary: This study theoretically investigates the intrinsic anomalous Hall effect and nonlinear Hall effect induced by Bloch band quantum geometry in the parity-mixed antiferromagnetic metal NbMnP, using first-principles calculations and the Wannier interpolation method. The results reveal that the intrinsic Hall response in NbMnP is predominantly governed by strongly enhanced Berry curvature and Berry connection polarizability dipoles on specific mirror planes, with these enhanced geometric quantities arising from the gap opening of nodal lines induced by spin-orbit coupling. These findings demonstrate that NbMnP can serve as a model system for studying nodal line transport phenomena in parity-mixed antiferromagnets, where the magnetic structure comprises both even- and odd-parity components, and symmetry breaking simultaneously permits the anomalous Hall effect and nonlinear Hall effect.\n7. Effect of Niobium Doping on the Crystal Structure and Hydrogen Sorption Properties of TiFe: Combined Synchrotron X-ray Diffraction and Extended X-ray Absorption Fine Structure Study Relevance Score: 3.1209 Authors: Abhishek Banerjee, Stefano Deledda, Olena Zavorotynska Affiliations: Institute for Energy Technology, University of Stavanger Link: http://arxiv.org/abs/2601.08935v1 Summary: This study synthesized two TiFe alloys with different niobium stoichiometric ratios using arc melting, and systematically investigated the effects of niobium doping on the crystal structure and hydrogen storage properties of TiFe intermetallic compounds through synchrotron powder X-ray diffraction and extended X-ray absorption fine structure analysis. Hydrogen absorption tests (50±2°C, 40±2 bar) demonstrated that niobium doping significantly improves the activation process and hydrogen absorption/desorption kinetics of the TiFe matrix without compromising total hydrogen storage capacity. Rietveld refinement and EXAFS data analysis revealed that niobium atoms preferentially occupy sites in the secondary titanium phase, and this selective occupancy promotes the hydrogenation performance of the alloy. The study further elucidated niobium-induced lattice expansion and structural changes after hydrogen adsorption/desorption cycles, providing direct structural evidence for optimizing TiFe-based hydrogen storage materials through elemental substitution.\n8. Pressure-Induced Martensitic Phase Transformation and Microstructure Evolution in nanograined $\\text{Fe}\\text{-}7\\%\\text{Mn}$ Alloy Relevance Score: 3.0991 Authors: Mrinmay Sahu, Sorb Yesudhas, Valery I. Levitas, Dean Smith Affiliations: Iowa State University, Argonne National Laboratory Link: http://arxiv.org/abs/2601.08202v1 Summary: This study employed in situ high-pressure synchrotron X-ray diffraction to investigate the structural phase transition and microstructural evolution of nanocrystalline Fe-7%Mn alloy under hydrostatic pressure. It was observed that the body-centered cubic phase at ambient conditions began transforming to the hexagonal close-packed phase at 11.4 GPa, with the two-phase coexistence region extending to 15.9 GPa, after which the pure hexagonal close-packed phase remained stable up to the maximum pressure of 30.3 GPa. X-ray diffraction analysis indicated that the phase transition followed a diffusionless Burger\u0026rsquo;s martensitic path, where the (110) close-packed plane of the bcc phase transforms into the (002) close-packed plane of the hcp phase, with the orientation relationship (110)b ∥ (0001)h. As pressure increased, grain size and microstrain exhibited significant changes during the phase transition, notably a sharp anomaly in microstrain at approximately 10 GPa, suggesting that microstructural alterations preceded the structural phase transformation. This work provides detailed experimental evidence for understanding the phase transition mechanisms and microstructural evolution of Fe-Mn alloys under high pressure.\n9. Coupling of Klein-Andreev Resonant States in Bi$_2$Sr$_2$CaCu$_2$O$_{8+x}$-graphene-Bi$_2$Sr$_2$CaCu$_2$O$_{8+x}$ Devices Relevance Score: 3.0761 Authors: Sharadh Jois, Jose L. Lado, Genda Gu, Qiang Li, Ji Ung Lee Affiliations: SUNY Polytechnic Institute, Brookhaven National Laboratory, University at Albany, SUNY, Aalto University, Stony Brook University Link: http://arxiv.org/abs/2601.08637v1 Summary: In Bi₂Sr₂CaCu₂O₈₊ₓ (BSCCO)-graphene-BSCCO devices, the research team observed a coupling effect between Klein tunneling and Andreev reflection resonant states (KARS) by varying the spacing L between the two BSCCO-graphene interfaces from tens of nanometers to several micrometers. This coupling manifests as a power-law decay of the resonance period with increasing L, approaching the single-junction limit when L exceeds 1 micrometer. Experiments revealed an increased period in short junctions, indicating strong hybridization of the two KARS cavities due to transport modes in graphene. Single-particle spectral function calculations support this length dependence, confirming long-range coupling of resonant states through the intermediate graphene region. This work demonstrates strong coupling of KARS cavities in high-temperature superconductor-graphene junctions, offering a new pathway for constructing quantum circuits and unconventional Josephson junctions.\n10. Frustrated Magnetism in FeGe$_3$O$_4$ with a Chiral Trillium Network Relevance Score: 3.0652 Authors: Matt Boswell, Mingyu Xu, Haozhe Wang, Mouyang Cheng, N. Li, X. F. Sun, Haidong Zhou, Huibo Cao, Mingda Li, Weiwei Xie Affiliations: Michigan State University, Massachusetts Institute of Technology, Anhui University, University of Tennessee, Oak Ridge National Laboratory Link: http://arxiv.org/abs/2601.08947v1 Summary: FeGe₃O₄ is a newly synthesized compound that crystallizes in the non-centrosymmetric cubic space group P2₁3, in which Fe atoms form a unique trillium lattice with nearest-neighbor Fe–Fe distances of approximately 4.2 Å, and Ge²⁺ ions mediate magnetic interactions through Fe–Ge–Fe pathways. Magnetization measurements reveal significant nonlinear field-dependent magnetization at 2 K, reaching a maximum magnetic moment of 2.55 μB/Fe²⁺ at 70 kOe without saturation; combined data from magnetic susceptibility, specific heat, and neutron scattering indicate that short-range magnetic interactions commence near 5 K, yet no long-range magnetic order is detected down to 0.06 K. Specific heat analysis demonstrates strong geometric frustration: only about 34% of the expected magnetic entropy is recovered at 2.4 K. These results establish FeGe₃O₄ as a rare geometrically frustrated trillium lattice magnet, offering a promising platform for exploring novel quantum magnetic phenomena.\n","permalink":"https://nickelates.uk/en/posts/2026-01-13-arxiv-daily/","summary":"\u003cblockquote\u003e\n\u003cp\u003e\u003cstrong\u003eDaily Overview\u003c/strong\u003e:\nIn today\u0026rsquo;s overview of papers on nickel-based superconductivity, there is no study directly centered on nickelates, but a theoretical work on graphene superconductivity is closely related to current hot topics in nickel-based superconductivity. Using the self-consistent Bogoliubov–de Gennes method, this work reveals how the \u0026ldquo;kinetic blocking\u0026rdquo; mechanism in strain-engineered graphene leads to the formation of quasi-one-dimensional filamentary structures of the superconducting order parameter at geometric nodes, presenting a pairing density wave state with sign reversal. This mechanism provides a theoretical framework for understanding the recently observed filamentary superconductivity in nickelate thin films, indicating that strain gradients can achieve spatial selectivity of the superconducting state by decoupling internal degrees of freedom, thereby expanding our understanding of quantum phase modulation with geometric origins.\n\u003cstrong\u003earXiv submission processing window\u003c/strong\u003e: 2026-01-12 22:51 to 2026-01-13 19:32 UTC.\u003c/p\u003e","title":"arXiv Daily: nickelate superconductors 2026-01-13"},{"content":" Daily Overview: Today\u0026rsquo;s highlight work is focused on deepening the understanding of the electronic structure of mixed Ruddlesden-Popper nickelates. In [1], a systematic study using soft X-ray absorption spectroscopy tracked the topotactic reduction process of PrNiOₓ thin films from the perovskite to the infinite-layer structure. By combining Ni L-edge and O K-edge spectroscopy with cluster model calculations, it was revealed that none of the samples exhibit a pure d⁹ configuration; even in the superconducting state, significant hole doping is present, and oxygen 2p holes persist. This result directly challenges previous assumptions regarding the hole doping limit and indicates that the self-doping effect, together with oxygen non-stoichiometry, leads to a complex hole doping mechanism, providing key experimental constraints for understanding the electronic ground state of nickelate superconductivity. arXiv submission processing window: 2026-01-12 01:00 to 2026-01-12 18:44 UTC.\n1. From perovskite to infinite-layer nickelates: hole concentration from x-ray absorption Relevance Score: 5.0157 Authors: R. Pons, M. Flavenot, K. Fürsich, E. Schierle, E. Weschke, M. R. Cantarino, E. Goering, P. Nagel, S. Schuppler, G. Kim, G. Logvenov, B. Keimer, R. J. Green, D. Preziosi, E. Benckiser Link: http://arxiv.org/abs/2601.07710v2 Summary: This study systematically investigated the evolution of PrNiOₓ thin films at various intermediate stages of topological reduction (x = 2–3) using soft X-ray absorption spectroscopy. By comparing Ni L-edge experimental spectra with single-cluster and double-cluster ligand-field model calculations, it was found that none of the samples exhibited a pure d⁹ electronic configuration. Quantitative analysis based on the charge sum rule revealed that even in the most reduced films, the average number of Ni 3d holes remained 1.35, while superconducting samples displayed higher hole counts, challenging previous assumptions regarding the hole doping limit. Concurrent changes in the O K-edge absorption spectra during reduction indicated the presence of O 2p holes even in the most reduced films. Collectively, these results suggest that a complex hole doping mechanism arises from the interplay between self-doping effects and oxygen non-stoichiometry.\n2. Prediction of superconductivity in mass-asymmetric electron-hole bilayers Relevance Score: 4.1325 Authors: Luca Nashabeh, Liang Fu Link: http://arxiv.org/abs/2601.07729v2 Summary: This study investigates a bilayer system with balanced densities but asymmetric effective masses of electrons and holes. By independently tuning the carrier density and interlayer spacing, the system exhibits a rich quantum phase diagram, including exciton condensates, Wigner crystals, and, under a large hole-electron mass ratio, a mixed phase of electron liquid and hole crystal analogous to two-dimensional metallic hydrogen. The phase diagram is quantitatively delineated using multicomponent Hartree-Fock and Hartree-Fock-Bogoliubov methods, and the effective electron-electron attraction mediated by acoustic plasmons is analyzed via the Pines method, which predicts a superconducting state within the classical BCS framework. The propagation velocity of acoustic plasmons is related to the compressibility of the system; the electron compressibility is calculated using the Hartree-Fock method, from which the superconducting transition temperature is derived. The results show that at intermediate densities and large mass asymmetry, the transition temperature can reach experimentally accessible values (e.g., tens of Kelvin under specific parameters), with the strongest superconductivity occurring at intermediate rather than very low densities. This work predicts plasmon-mediated superconductivity driven by Coulomb interactions and discusses its feasibility in transition metal dichalcogenide van der Waals heterostructures, offering a tunable platform for exploring novel superconducting states.\n3. Decoupled interband pairing in a bilayer iron-based superconductor evidenced by ultrahigh-resolution ARPES Relevance Score: 4.0883 Authors: Shichong Wang, Yuanyuan Yang, Yang Li, Wenshan Hong, Huaxun Li, Shaofeng Duan, Lingxiao Gu, Haoran Liu, Jiongyu Huang, Jianzhe Liu, Dong Qian, Guanghan Cao, Huiqian Luo, Wentao Zhang Link: http://arxiv.org/abs/2601.07380v1 Summary: Using ultrahigh-resolution angle-resolved photoemission spectroscopy (ARPES), researchers have directly observed experimental evidence of a weakly coupled multiband superconducting state in bilayer iron-based superconductors ACa₂Fe₄As₄F₂ (A = K, Cs). The K compound exhibits two distinct superconducting transition temperatures (33.5 K and 22 K) corresponding to two sets of bands split by bilayer coupling, as confirmed by temperature-dependent superconducting gaps and spectral weight near the Fermi level, whereas the Cs compound shows only a single conventional transition. These observations agree well with a weakly coupled two-band model based on Eilenberger theory, clearly identifying the suppression of interband pairing interaction as the key mechanism. Further high-resolution data confirm a nodeless gap and exclude pseudogap behavior at the Brillouin zone center. By exploring quantum phenomena in the weak-coupling limit of multiband systems, this discovery opens a pathway for engineering exotic superconductivity through band-selective pairing control.\n4. Interplay of Charge and Magnetic Orders in SmNiC$_2$ Mediated by Electron-Phonon Interaction Relevance Score: 3.8861 Authors: A. von Ungern-Sternberg Schwark, A. -A. Haghighirad, R. Heid, P. H. McGuinness, N. Maraytta, A. Eich, M. Merz, A. Bosak, D. A. Chaney, A. Chumakova, A. Pawbake, C. Faugeras, M. Le Tacon, S. M. Souliou Link: http://arxiv.org/abs/2601.07255v1 Summary: This study systematically investigates the competition between charge density wave (CDW) and ferromagnetic order in SmNiC₂ using inelastic X-ray scattering, Raman spectroscopy, and first-principles calculations. Experiments directly identify soft-phonon-driven incommensurate CDW (I-CDW) and reveal a second Kohn anomaly at the commensurate CDW (C-CDW) wave vector, indicating the coexistence and competition of two ordering tendencies. Upon cooling, the softening behaviors of the two soft phonons exhibit opposite temperature evolutions, uncovering the competition between I-CDW and C-CDW: the C-CDW tendency is stronger at room temperature, but the I-CDW phonon softens more rapidly with decreasing temperature, eventually locking into I-CDW long-range order while suppressing the complete softening of C-CDW. Raman spectroscopy detects the collective amplitude mode of the CDW, which abruptly disappears at the ferromagnetic transition temperature; surprisingly, despite the ferromagnetic state destroying the Fermi surface nesting condition, the Kohn anomalies at both wave vectors persist. Moreover, intrinsic phonons in Raman spectra show significant renormalization associated with the opening of the electronic energy gap, along with Fano line shapes, further confirming strong electron-phonon coupling. The combined results indicate that electron-phonon interactions in SmNiC₂ not only serve as the primary driving force for CDW formation but also play a central role in modulating the balance between charge and magnetic orders, with their evolution determining the ultimate stability of the competing phases.\n5. Magnetic field decouples nodeless surface and nodal bulk orders in PdTe Relevance Score: 3.7954 Authors: Atanu Mishra, Ghulam Mohmad, Kiran Bansal, Mohd Monish, Pankaj Kumar, Chandrasekhar Yadav, Goutam Sheet Affiliations: Indian Institute of Science Education and Research (IISER) Mohali, Indian Institute of Technology Mandi Link: http://arxiv.org/abs/2601.07493v2 Summary: This study employed magnetic-field-dependent Andreev reflection spectroscopy at sub-Kelvin temperatures to perform spectroscopic measurements on the candidate topological superconductor PdTe, successfully distinguishing its nodeless surface superconducting component from the nodal bulk superconducting component. Under zero magnetic field, the spectra exhibited a BCS-type gap structure, indicating that the surface superconducting state dominates the transport. Upon applying a weak magnetic field, the Andreev-enhanced conductance associated with surface states was abruptly suppressed at approximately 0.35 kG, whereas the conductance residual originating from the nodal bulk state persisted up to higher magnetic fields, with the entire process accompanied by significant hysteresis. The results demonstrate that the nodal bulk superconducting gap facilitates the early entry of magnetic flux vortices, thereby disrupting the fragile surface superconductivity. These findings establish a magnetic-field-tunable decoupling mechanism between surface and bulk superconductivity and elucidate how distinct gap topologies collectively shape the global superconducting order in multichannel systems.\n6. Observation of Time-Reversal Symmetry Breaking in the Type-I Superconductor YbSb$_2$ Relevance Score: 3.6517 Authors: Anshu Kataria, Shashank Srivastava, Dibyendu Samanta, Pushpendra Yadav, Poulami Manna, Suhani Sharma, Priya Mishra, Joel Barker, Adrian D. Hillier, Amit Agarwal, Sudeep Kumar Ghosh, Ravi Prakash Singh Link: http://arxiv.org/abs/2601.07460v1 Summary: In the type-I superconductor YbSb₂, spontaneous internal magnetic fields below the superconducting transition temperature were observed via zero-field μSR measurements; combined with transverse-field μSR and specific heat data, a fully gapped type-I superconducting state was confirmed. First-principles calculations indicate that YbSb₂ is a Z₂ topological metal with Dirac nodal lines. Symmetry analysis based on Ginzburg-Landau theory identifies the antisymmetric nonunitary triplet as the most likely superconducting ground state, which supports gapless Majorana surface modes. These results establish YbSb₂ as the first type-I superconductor exhibiting concurrent time-reversal symmetry breaking, triplet pairing, and nontrivial topology, providing a unique platform for studying the coexistence of topological superconductivity and type-I superconductivity.\n7. Emergent Cooperative Superstructures via Order-Disorder Kinetics in Molecule-Intercalated NbSe2 Relevance Score: 3.6407 Authors: Taiga Ueda, Hideki Matsuoka, Shungo Aoyagi, Shunsuke Kitou, Yijin Zhang, Fumihiko Kimura, Kenta Hagiwara, Masato Sakano, Takahiro Iwagaki, Yuiga Nakamura, Kyoko Ishizaka, Tomoki Machida, Masayuki Suda, Taka-hisa Arima, Naoya Kanazawa Affiliations: Japan Synchrotron Radiation Research Institute (JASRI), Nagoya University, The University of Electro-Communications, RIKEN, The University of Tokyo Link: http://arxiv.org/abs/2601.07216v1 Summary: In molecularly intercalated NbSe₂, researchers discovered a novel cooperative superstructure (CSS) phase using synchrotron X-ray diffraction: the ordering of intercalated organic molecules induces long-period distortions in the host NbSe₂ lattice, forming a moiré structure due to lattice mismatch, accompanied by a reduction in crystal symmetry. Resistivity and thermal quenching measurements indicate that this phase transition is governed by anomalously slow order-disorder kinetics, allowing the CSS phase to be selectively obtained under standard laboratory cooling rates, with the slow dynamics arising from the coupling between molecular motion and the host lattice. This finding suggests that molecular ordering can serve as a new pathway for designing heterogeneous interfaces, enabling thermally programmable superstructures.\n8. Ising Supercriticality and Universal Magnetocalorics in Spiral Antiferromagnet Nd$_3$BWO$_9$ Relevance Score: 3.5556 Authors: Xinyang Liu, Enze Lv, Xueling Cui, Han Ge, Fangyuan Song, Zhaoming Tian, Gang Su, Kan Zhao, Junsen Xiang, Peijie Sun, Wei Li Link: http://arxiv.org/abs/2601.07810v3 Summary: In the spiral antiferromagnet Nd₃BWO₉, low-temperature thermodynamic and magnetocaloric measurements have identified a phase boundary in the magnetic field-temperature phase diagram that terminates at a critical endpoint (CEP, μ₀Hc ≈ 1.04 T, Tc ≈ 0.3 K), where the metamagnetic transition line ends. Above the CEP, the system enters the Ising supercritical region, and its crossover line follows the scaling law of the three-dimensional Ising universality class, with specific heat, magnetic susceptibility, and magnetocaloric measurements all confirming this universal scaling behavior. Notably, a divergence of the magnetic Grüneisen ratio (Γ_H ∝ 1/t^{β+γ-1}, β+γ ≈ 1.563) is observed near the CEP, reflecting extremely high magnetic field sensitivity. Through adiabatic demagnetization experiments starting from initial conditions of 2 K and 4 T, the material achieves a minimum cooling temperature of 195 mK, benefiting from the supercritical magnetocaloric effect and topological cooling near zero entropy at the near-zero spin-flip field (approximately 0.36 T). The study demonstrates that the low critical temperature and high spin density arising from spin frustration make Nd₃BWO₉ an efficient refrigerant in the sub-Kelvin regime, with a volumetric entropy change much larger than that of conventional paramagnetic salts. Moreover, this supercritical magnetocaloric effect is universal and can be extended to other strongly Ising anisotropic magnets such as spin ice systems.\n9. Reconfigurable Oxide Nanoelectronics by Tip-induced Electron Delocalization Relevance Score: 3.4681 Authors: Chengyuan Huang, Changjian Ma, Mengke Ha, Longbing Shang, Zhenlan Chen, Qing Xiao, Zhiyuan Qin, Danqing Liu, Haoyuan Wang, Dawei Qiu, Qianyi Zhao, Ziliang Guo, Yanling Liu, Dingbang Chen, Chengxuan Ye, Zhenhao Li, Chang-Kui Duan, Guanglei Cheng Link: http://arxiv.org/abs/2601.07494v1 Summary: This study proposes a \u0026ldquo;water-free\u0026rdquo; conductive atomic force microscopy (cAFM) lithography method that operates under vacuum and low-temperature conditions. By performing oxygen vacancy engineering at the LaAlO₃/SrTiO₃ interface, nonvolatile and reconfigurable control of the nanoscale interfacial polaron-electron liquid transition at mK temperatures is achieved, with a line resolution of 0.85 nm. Combining first-principles calculations and a drift-diffusion model, tip-induced electromigration of oxygen vacancies is confirmed as the key mechanism. This method overcomes the limitations of conventional cAFM, which can only operate in air with simultaneous device degradation, enabling in situ reconfigurable device fabrication and characterization at mK temperatures, thereby providing a universal Hubbard toolbox for programmable quantum phase engineering in correlated oxides.\n10. Revealing altermagnetic Fermi surfaces with two Kondo impurities Relevance Score: 3.4677 Authors: Qiong Qin, Toshihiro Sato, Marcin Raczkowski, Jeroen van den Brink, Congjun Wu, Fakher F. Assaad Link: http://arxiv.org/abs/2601.07138v1 Summary: We propose a phase-sensitive method based on two Kondo impurities to probe the Fermi surface symmetry of altermagnetism using spin-resolved scanning tunneling microscopy. Employing finite-temperature quantum Monte Carlo simulations, we analyze the spin splitting of Kondo resonances, whose spatial distribution sensitively reflects the underlying altermagnetic order symmetry: when impurities are aligned along the nodal direction, SU(2) spin symmetry is restored and the resonances exhibit no spin splitting; along the antinodal direction, a spin-dependent asymmetry with opposite signs emerges, and its Fourier transform directly maps the altermagnetic symmetry. The inter-impurity spin correlation functions display anisotropy, with differences between longitudinal and transverse components arising from the modulation of RKKY interactions by the altermagnetic Fermi surface splitting. This method provides a phase-sensitive probe of altermagnetism at the single-particle level and reveals the competition among Kondo screening, RKKY coupling, and altermagnetism: at low temperatures, the magnitude of spin splitting increases with inter-impurity distance, while spin anisotropy is most pronounced at short distances. This work establishes a theoretical framework for studying the interplay of these quantum effects in a minimal system.\n11. Low-temperature Spark Plasma Sintering of fine refractory composite powders core-shell: A case of the powders W@Ni Relevance Score: 3.4001 Authors: A. V. Nokhrin, E. A. Lantcev, L. S. Alekseeva, N. V. Malekhonova, M. S. Boldin, Yu. V. Blagoveshchenskiy, N. V. Isaeva, A. V. Terentyev, K. E. Smetanina, N. V. Sakharov, N. V. Melekhin, V. D. Chupriyanova Affiliations: Lobachevsky University, Russian Academy of Sciences Link: http://arxiv.org/abs/2601.07888v1 Summary: This study investigates the low-temperature spark plasma sintering (SPS) mechanism of fine-grained W@Ni core-shell composite powders. Two types of W+10%Ni powders were prepared: a simple mixture of W and Ni powders (W+Ni) and a chemically metallized core-shell structure (W@Ni) with Ni deposited on submicron W particles. The powders were annealed in hydrogen to reduce oxygen and oxide content, followed by solid-state sintering at temperatures of 1000–1150°C, pressures of 40–80 MPa, heating rates of 50–500°C/min, and holding times of 0–20 min. The samples achieved high relative densities and fine grain sizes. The SPS activation energy for the mixed powder was close to that of grain boundary diffusion, while the key densification mechanism for W@Ni particles was Coble creep. Increasing the sintering temperature enhanced the solubility of W in Ni, leading to the precipitation of more secondary Ni4W particles during cooling. Compared to grain growth, changes in phase composition had a greater impact on the mechanical properties of the tungsten alloy.\n12. Anisotropic anomalous Hall effect in distorted kagome GdTi3Bi4 Relevance Score: 3.3448 Authors: Avdhesh K. Sharma, Bo Tai, Subhajit Roychowdhury, Premakumar Yanda, Ulrich Burkhardt, Xiaolong Feng, Claudia Felser, Chandra Shekhar Affiliations: Indian Institute of Science Education and Research Bhopal, Max Planck Institute for Chemical Physics of Solids Link: http://arxiv.org/abs/2601.07578v1 Summary: The Kagome magnet GdTi3Bi4, featuring distorted Ti-based Kagome layers interwoven with Gd zigzag chains along the a-axis, exhibits an antiferromagnetic order below 15 K. Through variable-temperature and variable-field electrical transport measurements along different directions, this study reveals that when the magnetic field is parallel to the c-axis, the sample displays an exceptionally high anomalous Hall conductivity of up to 410 S/cm at 2 K, which completely vanishes when the field is aligned with the a-axis. This phenomenon contradicts the conventional expectation that the anomalous Hall effect scales proportionally with magnetization, despite the similar magnetization behavior in both directions. First-principles calculations indicate that the Gd 4f sublattice breaks time-reversal symmetry, and in conjunction with spin-orbit coupling, the magnetization direction governs the orbital hybridization of Ti t2g bands, thereby redistributing Berry curvature hotspots and giving rise to this orientation-selective anomalous Hall conductivity. These findings establish GdTi3Bi4 as a platform for studying directional anomalous Hall effects, highlighting the intricate coupling between magnetism and electronic structure, and offering new insights for exploring novel quantum phenomena.\n13. Field-induced magnetic phase transitions and transport anomalies in GdAlSi Relevance Score: 3.2966 Authors: Zheng Li, Sheng Xu, Yi-Yan Wang, Tian-Hao Li, Shu-Xiang Li, Jin-Jin Wang, Jun-Jian Mi, Qian Tao, Zhu-An Xu Link: http://arxiv.org/abs/2601.07275v1 Summary: By successfully synthesizing high-quality GdAlSi single crystals and systematically investigating their magnetic and transport properties, this work reveals two successive antiferromagnetic transitions in the material, with critical temperatures of 31.9 K and 31.1 K, respectively. When the applied magnetic field exceeds 8 T, a third magnetic transition is further induced, giving rise to a series of metamagnetic phase transitions that collectively form a tree-like phase diagram. This complex magnetic behavior originates from the interaction between localized Gd-4f moments and itinerant conduction electrons, likely mediated by the Dzyaloshinskii–Moriya interaction. Transport measurements show significant step-like anomalies in magnetoresistance across phase boundaries, accompanied by pronounced hysteresis loops resulting from moment-flipping processes. This work not only establishes GdAlSi as an important platform for studying correlated topological states but also demonstrates the potential for engineering topological phase transitions in Weyl semimetals through manipulation of magnetic symmetry.\n14. Ultrafast control of spin order by linearly polarized light in noncollinear antiferromagnetic metals Relevance Score: 3.2728 Authors: J. Kimak, M. Nerodilova, K. Carva, S. Ghosh, J. Zelezny, T. Ostatnicky, J. Zemen, F. Johnson, D. Boldrin, F. Rendell-Bhatti, B. Zou, A. P. Mihai, X. Sun, F. Yu, E. Schmoranzerova, L. Nadvornik, L. F. Cohen, P. Nemec Link: http://arxiv.org/abs/2601.07753v1 Summary: In the noncollinear antiferromagnetic metals Mn₃NiN and Mn₃GaN, nonthermal ultrafast control of the spin order is achieved solely through the polarization direction of linearly polarized femtosecond laser pulses. Using transient magneto-optical pump-probe experiments based on the Voigt effect, sub-picosecond magnetic order changes and subsequent picosecond relaxation processes are observed. The magneto-optical response strongly depends on the relative orientation of the pump and probe polarization planes, exhibiting a linear polarization dependence as high as 95%, a value unprecedented among metallic magnets. This effect is present in both materials and remains robust over a wide range of excitation wavelengths, fluences, and temperatures. Symmetry analysis and microscopic modeling indicate that photo-induced spin torques alone cannot fully explain the observed dynamics, leading to the proposal that the formation of a laser-induced transient spin spiral state serves as the possible excitation mechanism.\n15. Role of Disorder in Governing the Magnetic Properties of Cu2IrO3 Relevance Score: 3.2413 Authors: Priyanka Yadav, Sumit Sarkar, Vishal Kumar, Sanjay Singh, Martin A Karlsen, Martin Etter, Sourav Chowdhury, Subhajit Nandy, Yogesh Singh Link: http://arxiv.org/abs/2601.07379v1 Summary: We synthesized Cu₂IrO₃ samples with significant antisite disorder (approximately 25%) via a topotactic reaction, and characterized their global and local structures using X-ray diffraction, extended X-ray absorption fine structure (EXAFS), and X-ray pair distribution function (PDF) analyses, combined with XPS and XANES for charge state determination. The results reveal the coexistence of mixed valence states of Cu¹⁺/Cu²⁺ and Ir⁴⁺/Ir³⁺, where antisite disorder and charge redistribution jointly induce competing antiferromagnetic interactions and magnetic frustration, leading to the formation of dynamically fluctuating antiferromagnetic clusters near 80 K and their freezing below 29 K. This finding highlights the critical role of synthesis condition-dependent disorder in determining the magnetic ground state of Cu₂IrO₃.\n16. Hidden half-metallicity Relevance Score: 3.2183 Authors: San-Dong Guo, Pan Zhou Link: http://arxiv.org/abs/2601.07128v1 Summary: This paper introduces the concept of \u0026ldquo;hidden half-metallicity,\u0026rdquo; wherein in magnets with symmetry-enforced net zero magnetization, the global electronic structure does not exhibit half-metallic characteristics, but two symmetry-related sectors independently achieve 100% spin polarization, thereby obtaining robust spin-selective functionality through the layer degree of freedom. Due to the vanishing net magnetic moment, stray fields and magnetic instabilities are suppressed, making this half-metallic state more stable than conventional ferromagnetic half-metals. Using first-principles calculations, the authors verify this mechanism in bilayer CrS₂ with PT symmetry: although the global band structure is spin-degenerate and lacks half-metallicity, the lower and upper layers each retain half-metallic features with opposite spins. Under an external electric field, the system transforms into a fully compensated ferrimagnetic metal, yet the hidden half-metallicity persists, and the electric field can tune the spin degrees of freedom. Furthermore, this concept is preliminarily confirmed in altermagnetic bilayer structures. This study establishes a general paradigm for stabilizing half-metallic behavior through symmetry-protected hidden sectors, opening new avenues for designing and discovering novel half-metallic phases.\n17. Sliding Charge Density Wave observed through Band Structure Relevance Score: 3.1990 Authors: S. Mandal, D. Ghoneim, A. A. Sinchenko, V. L. R. Jacques, K. Wang, L. Ortega, J. Avila, P. Dudin, A. Tejeda, D. Le Bolloch Link: http://arxiv.org/abs/2601.07417v1 Summary: In incommensurate charge density wave (CDW) systems, the sliding phenomenon can generate an additional current, typically observed through transport or diffraction measurements, but theoretically also manifesting in the band structure. In this study, we employ angle-resolved photoemission spectroscopy (ARPES) to probe band structure changes in the quasi-two-dimensional material TbTe₃ under an applied current. Fermi surfaces and band dispersions are measured both below and above the threshold current (approximately 30 mA), with focus on the CDW gap region. The results show that a positive current shifts the left-side band upward and the right-side band downward, while a negative current produces the opposite effect; the gap energy shifts by approximately 12 meV, and the direction of the shift reverses upon current reversal. This effect is not evident in the non-CDW reference band, indicating that the electric field mainly influences CDW-related bands. These small but systematic band shifts are consistent with predictions of k-space symmetry breaking in the sliding CDW theory, providing experimental evidence for observing sliding CDW via band structure.\n18. High isothermal magnetocaloric effect in La(Fe,Si)13 based alloys Relevance Score: 3.1270 Authors: A. P. Kamantsev, Yu. S. Koshkid`ko, O. E. Kovalev, N. Yu. Nyrkov, A. V. Golovchan, A. A. Amirov, A. M. Aliev Affiliations: Galkin Donetsk Institute for Physics and Technology, Russian Academy of Sciences Link: http://arxiv.org/abs/2601.07478v1 Summary: This study directly measured the adiabatic temperature change ΔT and isothermal entropy change ΔQ of LaFe₁₁.₆Si₁.₄ and LaFe₁₁.₇₈Mn₀.₄₁Si₁.₃₂H₁.₆ alloys under a magnetic field of μ₀H = 1.8 T. The experiments demonstrated that both samples exhibited high repeatability of the ΔQ effect under cyclic magnetic field application, which is crucial for magnetic refrigeration systems. Notably, the LaFe₁₁.₇₈Mn₀.₄₁Si₁.₃₂H₁.₆ alloy displayed excellent isothermal magnetocaloric effect near its Curie temperature of approximately 275 K, with a maximum ΔQ of 3400 J/kg, which is 2.5 times that of pure Gd at room temperature under the same field. The ΔT of this alloy was about 4.5 K, comparable to that of Gd. Furthermore, density functional theory calculations were employed to investigate the effects of Cr and Co doping on the structural and magnetic properties of LaFe₁₃₋ₓSiₓ-based alloys: Cr incorporation led to a reduced equilibrium volume and lattice compression, which is expected to increase the Curie temperature, while Co incorporation caused lattice expansion, which is expected to lower the Curie temperature. These results provide theoretical guidance for optimizing the magnetocaloric performance of La(Fe,Si)₁₃-based alloys and confirm their potential as high-efficiency magnetic refrigeration materials under low to moderate magnetic fields.\n19. Percolation-Driven Magnetotransport due to Structural and Microstructural Evolution in Ultrathin Si/Fe Bilayers Relevance Score: 3.0950 Authors: S. S. Das, M. Senthil Kumar Affiliations: Indian Institute of Technology Bombay, The University of Tokyo Link: http://arxiv.org/abs/2601.07115v1 Summary: This study systematically analyzes the evolution of structural, microstructural, and magnetotransport properties in Si/Fe bilayer films as a function of Fe layer thickness (10–200 Å). XRD, HRTEM, and magnetization measurements reveal that when the Fe thickness falls below 30 Å, the film transitions from a continuous metallic film to a percolating granular network structure. The longitudinal resistivity ρ and anomalous Hall resistivity ρ_{AHS} exhibit pronounced divergence near the percolation threshold, with the evolution of the purely electronic conduction channel ρ being more gradual than that of the magnetically coupled channel ρ_{AHS}. Percolation analysis of the structural, magnetic, and magnetotransport data yields critical exponents in the range of 0.78–1.16, consistent with the characteristics of a two-dimensional disordered system. The scaling relationship between ρ_{AHS} and ρ in the anomalous Hall effect reveals a mechanism transition: in low-resistivity samples with thickness exceeding 30 Å, mixed intrinsic/side-jump contributions dominate with minor skew scattering (n ≈ 1.42), whereas in high-resistivity samples with thickness ≤ 30 Å, skew scattering becomes dominant (n = 0.62), a transition that coincides precisely with the emergence of intergranular structural and magnetic connectivity. The findings highlight the intrinsic correlations among microstructure, morphology, magnetism, and Hall transport within the percolation framework.\n20. Magnons in multiorbital Hubbard models, from Lieb to kagome Relevance Score: 3.0455 Authors: Teng-Fei Ying, Hugo U. R. Strand, Benjamin T. Zhou, Erik G. C. P. van Loon Link: http://arxiv.org/abs/2601.07562v2 Summary: This study systematically investigates the magnetic order and magnetic excitations in the half-filled Hubbard model as it continuously transitions from the Lieb lattice to the kagome lattice, employing a real-time two-particle response function method based on the self-consistent Hartree-Fock approximation combined with the Bethe-Salpeter equation (random phase approximation). By constructing the U-t\u0026rsquo; phase diagram, typical magnetic states such as paramagnetic, ferrimagnetic, and antiferromagnetic phases are identified, along with their corresponding magnetic excitation spectra. The results reveal that, in addition to gapless Goldstone magnons, there exist gapped Higgs magnon bands in the symmetry-broken ferrimagnetic and antiferromagnetic phases, originating from amplitude fluctuations of the spontaneous symmetry-breaking order parameter. At the Lieb limit, the high density of states at the Fermi level induced by the flat band leads to ferromagnetic order even for small U; as the interpolation parameter t\u0026rsquo; increases, the flat band disperses, raising the critical interaction U. Near the kagome limit, spin frustration gives rise to a narrow range of antiferromagnetic order. Furthermore, by applying a staggered magnetic field, an alternating magnetic state can be metastably obtained, whose magnetic susceptibility exhibits a combined symmetry of rotation and spin-flip. This study elucidates the dependence of magnetic phases and magnon spectra on lattice geometry and electronic correlations in multi-orbital Hubbard models.\n","permalink":"https://nickelates.uk/en/posts/2026-01-12-arxiv-daily/","summary":"\u003cblockquote\u003e\n\u003cp\u003e\u003cstrong\u003eDaily Overview\u003c/strong\u003e:\nToday\u0026rsquo;s highlight work is focused on deepening the understanding of the electronic structure of mixed Ruddlesden-Popper nickelates. In [1], a systematic study using soft X-ray absorption spectroscopy tracked the topotactic reduction process of PrNiOₓ thin films from the perovskite to the infinite-layer structure. By combining Ni L-edge and O K-edge spectroscopy with cluster model calculations, it was revealed that none of the samples exhibit a pure d⁹ configuration; even in the superconducting state, significant hole doping is present, and oxygen 2p holes persist. This result directly challenges previous assumptions regarding the hole doping limit and indicates that the self-doping effect, together with oxygen non-stoichiometry, leads to a complex hole doping mechanism, providing key experimental constraints for understanding the electronic ground state of nickelate superconductivity.\n\u003cstrong\u003earXiv submission processing window\u003c/strong\u003e: 2026-01-12 01:00 to 2026-01-12 18:44 UTC.\u003c/p\u003e","title":"arXiv Daily: nickelate superconductors 2026-01-12"},{"content":" Daily Overview: Hello readers, welcome to today\u0026rsquo;s rapid overview of papers in the nickel-based superconductivity field. Although no paper directly focuses on nickelates today, several works are highly relevant to the core issues currently under investigation in this field, from perspectives such as superconducting pairing mechanisms, interface physics, and materials preparation. Among them, [3] systematically studies the FFLO superconducting states driven by two types of alternating magnetic order—(d_{xy}) and (d_{x^{2}-y^{2}})—in two-dimensional lattices, revealing the stabilization conditions over a wide parameter range at low fillings, providing theoretical clues for exploring possible finite-momentum pairing in nickel-based superconductors. [1] reviews mechanisms such as Ising pairing and superconductor/ferromagnet proximity effects in van der Waals superconducting electronics; the concepts of interfacial tunability and nonreciprocal transport discussed therein offer insights for understanding interface superconductivity in nickelate heterostructures. [5] definitively rules out magnetic order in RuO₂ using X-ray linear dichroism, and this conclusion also holds methodological reference value for clarifying the controversy over spin configurations in nickelates. Additionally, [4] presents the epitaxial synthesis and electronic structure characterization of metastable TaO₂ thin films, demonstrating stabilization strategies for oxide metastable phases, which may provide process inspiration for phase engineering of nickelate thin films. Collectively, these works enrich the physical and materials understanding relevant to nickel-based superconductivity from different perspectives. arXiv submission processing window: 2026-01-10 20:02 to 2026-01-11 18:19 UTC.\n1. Van der Waals superconducting electronics: materials, devices and circuit integration Relevance Score: 3.8746 Authors: Angelo Di Bernardo, Elke Scheer Affiliations: University of Konstanz, University of Salerno Link: http://arxiv.org/abs/2601.07018v1 Summary: Van der Waals superconductors, owing to their atomically thin layered structures and stackable heterojunction characteristics, exhibit unique advantages in superconducting electronics. This review systematically summarizes their physical mechanisms, including Ising pairing, band inversion, and the proximity effect at superconductor/ferromagnet interfaces, which endow these materials with properties such as high in-plane critical fields, electrostatic tunability, and non-reciprocal transport that are unattainable in conventional superconductors. Based on these features, the review surveys various van der Waals superconducting devices, such as gate-tunable devices, superconducting diodes, and circuit elements for qubit readout and control. Although preliminary experimental evidence has emerged for topological superconductivity, conclusive proof is still lacking and requires further precisely controlled studies. Finally, the paper discusses wafer-scale growth and deterministic assembly techniques, identifying them as critical pathways for transitioning van der Waals devices from prototypes to practical applications in low-temperature electronics and quantum technologies.\n2. Comparison of Two-Level System Microwave Losses in Pure Bulk Microcrystalline Nb2O5 and NbO2 Oxide Samples Relevance Score: 3.7877 Authors: Vishal Ganesan, Jiankun Zhang, Drew G. Wild, Alexey Bezryadin Link: http://arxiv.org/abs/2601.06668v4 Summary: This study employs a superconducting three-dimensional microwave cavity to directly compare the two-level system (TLS) microwave loss characteristics of commercial pure microcrystalline Nb₂O₅ and NbO₂ bulk powders. The oxide powders were mixed with nail polish and coated onto a sapphire substrate, which was then placed at the region of maximum electric field within a niobium cavity; the loss was characterized by measuring the intrinsic quality factor at varying microwave powers and temperatures. Control experiments confirmed that neither the empty cavity nor the bare sapphire substrate exhibited measurable TLS loss. For the Nb₂O₅ samples, the quality factor decreased significantly at low power, and the power and temperature dependence conformed to predictions of the standard tunneling model, with a fitted exponent β indicating the presence of interacting TLSs, thereby demonstrating that the TLS loss originates from either the Nb₂O₅ bulk phase or the oxide-vacuum interface. In contrast, the NbO₂ samples displayed no TLS loss characteristics across the entire power range. Based on these results, the paper proposes that if the native oxide layer on practical niobium cavities were primarily composed of high-quality microcrystalline NbO₂ rather than Nb₂O₅, it could potentially reduce TLS loss, offering a material-level reference for strategies to isolate oxide-specific loss in superconducting quantum devices.\n3. Altermagnetism-driven FFLO superconductivity in finite-filling 2D lattices Relevance Score: 3.6170 Authors: Xia-Ji Liu, Hui Hu Link: http://arxiv.org/abs/2601.06735v1 Summary: This paper systematically investigates finite-momentum FFLO superconducting states driven by two types of altermagnetic order—d_{xy}-wave and d_{x^{2}-y^{2}}-wave—at finite doping in the two-dimensional square-lattice Hubbard model. Methodologically, it combines the mean-field Bogoliubov–de Gennes equation solution for the superconducting phase with a pairing instability analysis of the normal state based on the Thouless criterion, and introduces next-nearest-neighbor hopping into the single-particle dispersion. The key findings reveal that the two altermagnetic orders have markedly different stabilizing effects on the FFLO state: d_{xy}-wave altermagnetism supports FFLO superconductivity over a broad parameter regime at low doping, whereas d_{x^{2}-y^{2}}-wave order induces FFLO pairing only in a narrow range at high doping. Furthermore, van Hove singularities in the density of states suppress FFLO superconductivity. The conclusion indicates that these results provide theoretical guidance for the experimental exploration of altermagnetism-induced FFLO states in real materials with more complex electronic structures.\n4. Synthesis of epitaxial TaO$_2$ thin films on Al$_2$O$_3$ by suboxide molecular-beam epitaxy and thermal laser epitaxy Relevance Score: 3.4461 Authors: Yorick A. Birkhölzer, Anna S. Park, Noah Schnitzer, Jeffrey Z. Kaaret, Benjamin Z. Gregory, Tomas A. Kraay, Tobias Schwaigert, Matthew R. Barone, Brendan D. Faeth, Felix V. E. Hensling, Iris C. G. van den Bosch, Ellen M. Kiens, Christoph Baeumer, Enrico Bergamasco, Markus Grüninger, Alexander Bordovalos, Suresh Chaulagain, Nikolas J. Podraza, Waldemar Tokarz, Wojciech Tabis, Matthew J. Wahila, Suchismita Sarker, Christopher J. Pollock, Shun-Li Shang, Zi-Kui Liu, Nongnuch Artrith, Frank M. F. de Groot, Nicole A. Benedek, Andrej Singer, David A. Muller, Darrell G. Schlom Affiliations: University of Toledo, AGH University of Krakow, University of Cologne, University of Twente, Cornell University, Binghamton University, Utrecht University, Max Planck Institute for Solid State Research, Leibniz-Institut für Kristallzüchtung, The Pennsylvania State University Link: http://arxiv.org/abs/2601.06716v3 Summary: This study successfully epitaxially stabilized metastable TaO₂ thin films on r-plane sapphire (Al₂O₃(1-102)) substrates using suboxide molecular beam epitaxy (S-MBE) and thermal laser epitaxy (TLE), achieving single-orientation, single-domain anisotropic strain growth. Microstructural characterization was performed via synchrotron X-ray diffraction and scanning transmission electron microscopy, while X-ray absorption/photoelectron spectroscopy and electron energy-loss spectroscopy confirmed the +4 valence state of tantalum. Optical property measurements revealed a Mott gap of 0.3 eV for the tantalum 5d electrons. Density functional theory and group theory analyses indicated the limited stability of rutile-phase TaO₂ and unveiled a possible hidden metal-insulator transition accompanying its structural phase transition (to a distorted rutile phase), analogous to NbO₂. This work expands the understanding of tantalum oxides and lays the foundation for their integration into next-generation electronic and photonic devices.\n5. Absence of magnetic order in epitaxial RuO2 revealed by X-ray linear dichroism Relevance Score: 3.1072 Authors: Siyu Wang, Chao Wang, Yanan Yuan, Jiangxiao Li, Fangfang Pei, Daxiang Liu, Chunyu Qin, Jiefeng Cao, Yamei Wang, Tianye Wang, Jiayu Liu, Jieun Lee, Guanhua Zhang, Christoph Klewe, Chenchao Yu, Fan Zhang, Dongsheng Song, Kai Chen, Weisheng Zhao, Dawei Shen, Ziqiang Qiu, Mengmeng Yang, Bin Hong, Qian Li Affiliations: University of California at Berkeley, Lawrence Berkeley National Laboratory, Anhui University, Chinese Academy of Sciences, University of Science and Technology of China, Beihang University Link: http://arxiv.org/abs/2601.06791v1 Summary: This study systematically examined the magnetic ordering of epitaxial RuO₂ thin films using X-ray linear dichroism (XLD) combined with photoemission electron microscopy and multiple-scattering calculations. Experimental results showed that the XLD signals of RuO₂ were almost independent of temperature and the direction of the cooling magnetic field, which significantly contradicted the magnetically ordered XLD signals predicted by multiple-scattering calculations, strongly suggesting a nonmagnetic origin for RuO₂. Furthermore, RuO₂ films grown on TiO₂ substrates with different orientations exhibited markedly distinct XLD signals at the Ru M₃ edge and O K edge, attributable to low-symmetry crystal field effects. These findings unambiguously demonstrate the absence of magnetic ordering in RuO₂ while establishing XLD measurements as a powerful tool for probing magnetic materials with low symmetry.\n6. Case study of an exploratory high voltage NASICON-based Na$_4$NiCr(PO$_4$)$_3$ cathode material for sodium-ion batteries Relevance Score: 3.0914 Authors: Madhav Sharma, Pooja Sindhu, Rajendra S. Dhaka Link: http://arxiv.org/abs/2601.07012v1 Summary: This study systematically explores a novel NASICON-type Na₄NiCr(PO₄)₃ cathode material aimed at achieving high voltage and multi-electron reactions. X-ray diffraction Rietveld refinement confirmed the stable existence of a rhombohedral NASICON framework, with Raman and infrared spectroscopy further validating the structural features. X-ray photoelectron spectroscopy revealed that Cr is in the +3 oxidation state and Ni exhibits a mixed +2/+3 valence state. Bond valence energy landscape analysis indicated a three-dimensionally interconnected sodium-ion migration network with an energy barrier of 0.468 eV. Electrochemical tests demonstrated that the material delivers a favorable charge capacity at approximately 4.5 V, yet no sodium-ion intercalation was observed during discharge, resulting in negligible discharge capacity. Post-cycling analysis confirmed the structural integrity of the crystal, and although the ion migration energy barrier exhibited a reversal after cycling, ion transport remained feasible, suggesting that irreversible capacity is not primarily due to ionic transport limitations but rather stems from the material\u0026rsquo;s inherently poor electronic conductivity. These findings elucidate the key challenges in achieving stable reversible capacity within this system and underscore the necessity of doping, structural modification, and electrolyte optimization to realize its potential as a high-voltage cathode material.\n","permalink":"https://nickelates.uk/en/posts/2026-01-11-arxiv-daily/","summary":"\u003cblockquote\u003e\n\u003cp\u003e\u003cstrong\u003eDaily Overview\u003c/strong\u003e:\nHello readers, welcome to today\u0026rsquo;s rapid overview of papers in the nickel-based superconductivity field. Although no paper directly focuses on nickelates today, several works are highly relevant to the core issues currently under investigation in this field, from perspectives such as superconducting pairing mechanisms, interface physics, and materials preparation. Among them, [3] systematically studies the FFLO superconducting states driven by two types of alternating magnetic order—(d_{xy}) and (d_{x^{2}-y^{2}})—in two-dimensional lattices, revealing the stabilization conditions over a wide parameter range at low fillings, providing theoretical clues for exploring possible finite-momentum pairing in nickel-based superconductors. [1] reviews mechanisms such as Ising pairing and superconductor/ferromagnet proximity effects in van der Waals superconducting electronics; the concepts of interfacial tunability and nonreciprocal transport discussed therein offer insights for understanding interface superconductivity in nickelate heterostructures. [5] definitively rules out magnetic order in RuO₂ using X-ray linear dichroism, and this conclusion also holds methodological reference value for clarifying the controversy over spin configurations in nickelates. Additionally, [4] presents the epitaxial synthesis and electronic structure characterization of metastable TaO₂ thin films, demonstrating stabilization strategies for oxide metastable phases, which may provide process inspiration for phase engineering of nickelate thin films. Collectively, these works enrich the physical and materials understanding relevant to nickel-based superconductivity from different perspectives.\n\u003cstrong\u003earXiv submission processing window\u003c/strong\u003e: 2026-01-10 20:02 to 2026-01-11 18:19 UTC.\u003c/p\u003e","title":"arXiv Daily: nickelate superconductors 2026-01-11"},{"content":" Daily Overview: Dear readers, welcome to today\u0026rsquo;s overview of the latest papers in the field of nickel-based superconductivity. The highlight of today\u0026rsquo;s work focuses on a deeper understanding of the electronic structure of hybrid Ruddlesden–Popper nickelates. In [1], a theoretical study employing a molecular orbital basis to treat the quarter-filled bilayer system reveals the emergence of Kugel–Khomskii physics and predicts a novel maximal spin-layer entangled phase, providing a specific theoretical framework for understanding composite entanglement in bilayer nickelate superconductors. Additionally, [5] investigates the coexistence of superconductivity and charge density waves (CDW) in correlated systems using the Green\u0026rsquo;s function method, exploring the impact of next-nearest-neighbor hopping on competition—a topic closely related to the interplay between CDW and superconductivity in nickel-based superconductors, and thus worthy of attention. arXiv submission processing window: 2026-01-09 21:54 to 2026-01-10 17:32 UTC.\n1. Emergence of Kugel-Khomskii physics in quarter-filled bilayer correlated systems Relevance Score: 4.3718 Authors: Guijing Duan, Yunlong Wang, Zhiguang Liao, Changle Liu, Rong Yu Link: http://arxiv.org/abs/2601.06440v1 Summary: This study investigates a quarter-hole-filled two-orbital bilayer Hubbard model inspired by transition metal bilayer systems. By explicitly treating the strong interlayer bonding of the dz2 orbital in a molecular orbital basis and projecting out high-energy electronic states, we derive a low-energy effective Kugel-Khomskii Hamiltonian that describes the coupling between electron spins and layer pseudospins. Combining Weiss mean-field theory with generalized flavor-wave theory, we reveal a rich ground-state phase diagram, including ferromagnetic and antiferromagnetic phases accompanied by layer-staggered charge-density order, a layer-coherent phase with spontaneous interlayer quantum coherence, and a novel maximal spin-layer entangled phase. This entangled phase arises from an emergent O(4) symmetry that is spontaneously broken to O(3), and its excitation spectrum features three gapless Goldstone modes that are entangled. The results suggest a geometry-driven mechanism for realizing composite entanglement in strongly correlated bilayer systems, and provide a concrete theoretical framework for understanding bilayer nickelate superconductors and other multi-component correlated materials.\n2. Superconductivity in epitaxial PtSb(0001) thin films Relevance Score: 4.2146 Authors: C. Müller, S. P. Bommanaboyena, A. Badura, T. Uchimura, F. Husstedt, B. V. Schwarze, S. Banerjee, M. Ledinský, J. Michalicka, M. Míšek, M. Šindler, T. Helm, S. Fukami, F. Krizek, D. Kriegner Link: http://arxiv.org/abs/2601.06504v1 Summary: This paper reports the epitaxial growth of PtSb(0001) thin films on SrF₂(111) substrates, with X-ray diffraction, atomic force microscopy, and scanning transmission electron microscopy confirming their single-crystalline quality and hexagonal structure. Electrical transport measurements reveal a superconducting transition temperature of approximately 1.72 K, and the broadening of the transition under magnetic fields along with a finite upper critical field indicate type-II superconductivity. Fitting the temperature dependence of the upper critical field for different orientations using the anisotropic Ginzburg-Landau model yields in-plane and out-of-plane coherence lengths of approximately 55 nm and 14 nm, respectively, for a 50 nm thick film. Current-voltage characteristics show a substantial critical current, with a critical current density of approximately 6 × 10⁴ A/cm² at 0.5 K. These results establish epitaxial PtSb as a superconducting thin-film platform within the NiAs-type material family, compatible with lattice-matched heterostructures.\n3. Weakly spin-dependent band structures of antiferromagnetic perovskite LaMO$_3$ (M = Cr, Mn, Fe) Relevance Score: 3.6152 Authors: Takuya Okugawa, Kaoru Ohno, Yusuke Noda, Shinichiro Nakamura Link: http://arxiv.org/abs/2601.06422v1 Summary: This study systematically calculated the electronic bands of 15 different antiferromagnetic structures for the antiferromagnetic perovskites LaCrO₃, LaMnO₃, and LaFeO₃ using spin-polarized first-principles density functional theory (DFT) with the Hubbard U correction. A remarkably simple rule was discovered: by examining the symmetry operations that map up-spin atoms to down-spin atoms, one can conveniently determine which wavevectors in the band structure exhibit spin splitting or remain spin degenerate. For the most stable spin configuration corresponding to the experimentally observed structure of each material, the calculated spin splitting is extremely small. This property offers potential advantages in electrode applications, as it enables direction-independent spin current, thereby facilitating improved electrochemical performance.\n4. Dynamic nanoscale spatial heterogeneity in a perovskite to brownmillerite topotactic phase transformation Relevance Score: 3.4138 Authors: Nicolò D\u0026rsquo;Anna, Erik S. Lamb, Robin Glefke, Daseul Ham, Ishmam Nihal, Su Yong Lee, Yayoi Takamura, Oleg Shpyrko Link: http://arxiv.org/abs/2601.06365v1 Summary: Using in situ Bragg X-ray photon correlation spectroscopy (XPCS), this study reveals nanoscale spatial and dynamic heterogeneity during the perovskite-to-brownmillerite topological phase transition in La₀.₇Sr₀.₃CoO₃ thin films under constant reducing conditions. The experiment identifies two distinct time scales in the phase transition: a faster time scale associated with domain growth remains stable, corresponding to a domain wall velocity of 6 ± 0.5 × 10⁻⁴ nm/s, while a slower time scale related to temperature-driven domain depinning exhibits accelerating dynamics following an aging power law with an exponent of −2.2 ± 0.5. Pre-existing domains comprising approximately 0.2% of the material serve as nucleation centers before the brownmillerite transition. The slower time scale accelerates by nearly an order of magnitude over 9000 seconds (2.5 hours), indicating that even when the phase transition appears macroscopically complete, nanoscale domain and domain wall motions continue to evolve and accelerate. This work confirms Bragg XPCS as an effective tool for studying nanoscale dynamics during phase transitions and suggests that such continuously evolving heterogeneity may significantly impact the electrical properties of phase-change devices.\n5. Coexistence of superconductivity and charge density wave in a correlated regime Relevance Score: 3.4101 Authors: E. J. Calegari, L. C. Prauchner, A. C. Lausmann, S. G. Magalhaes Link: http://arxiv.org/abs/2601.06326v1 Summary: This study employs the Green’s function formalism together with the Hubbard-I approximation to investigate the coexistence of superconductivity (SC) and charge density wave (CDW) in correlated systems by introducing a repulsive Coulomb interaction U, while also analyzing the influence of next-nearest-neighbor hopping t1 on the pure CDW state. The results indicate that when t1 is small, the CDW and superconducting gaps compete on the same region of the Fermi surface; as t1 increases, the competition weakens, and the system may enter a coexistent SC and CDW state. Additionally, the effect of temperature on the coexistence region is examined. This model provides a theoretical basis for understanding the interplay between superconductivity and CDW in strongly correlated systems.\n6. Altermagnetism in exactly solvable model: the Ising-Kondo lattice model Relevance Score: 3.2590 Authors: Miaomiao Zhao, Wei-Wei Yang, Yin Zhong Link: http://arxiv.org/abs/2601.06511v2 Summary: This study employed an accurate lattice Monte Carlo method to introduce an alternating next-nearest-neighbor hopping term caused by nonmagnetic atoms into the Ising-Kondo lattice model, which is commonly used to describe heavy fermion materials, thereby investigating the existence of an alternating magnetic phase. The results demonstrate that this model exhibits key characteristics of d-wave alternating magnetism near half-filling, including spin-split quasiparticle bands and spectral functions, and this phase remains stable across a wide range of interaction strengths, doping levels, hopping amplitudes, and temperatures, underscoring its robustness. Analysis of nonmagnetic impurity effects further confirmed the d-wave symmetry of the alternating magnetic phase. These findings provide a solid theoretical foundation for studying alternating magnetic phases in f-electron compounds and open new avenues for exploring their unique magnetic and electronic properties.\n7. Magnetic exchange coupled nonreciprocal devices for cryogenic memory Relevance Score: 3.1706 Authors: Josep Ingla-Aynés, Lina Johnsen Kamra, Franklin Dai, Yasen Hou, Shouzhuo Yang, Peng Chen, Oleg A. Mukhanov, Jagadeesh S. Moodera Link: http://arxiv.org/abs/2601.06632v1 Summary: This study proposes a device platform based on exchange coupling, where an ultrathin superconductor (vanadium) is sandwiched between two ferromagnetic insulators (EuS). By tuning the relative parallel or antiparallel alignment of the magnetization directions of the ferromagnetic insulators, the superconducting exchange coupling strength is modulated, enabling the switching of the superconducting state for nonvolatile memory. Utilizing heat-assisted magnetic recording technology, individual memory cells are selectively switched via local heating induced by current pulses while maintaining the superconducting state of adjacent cells. Below the critical temperature, devices with antiparallel alignment exhibit a significant zero-field superconducting diode effect, with an efficiency exceeding ±60% and reaching up to 80%, along with reproducibility and scalability. The device also features three residual states (forward, reverse, and low-current blocking), applicable to superconducting programmable logic circuits. The authors suggest that integrating this platform with superconducting single-flux-quantum circuits could enhance the energy efficiency and functionality of classical and quantum computing, and enable on-chip integration of topological qubits.\n8. ZnO/ZnS heterostructures as hole reservoir to boost Ni foam energy storage performance Relevance Score: 3.0451 Authors: Alessia Fischetti, Giacometta Mineo, Daniela Russo, Francesco Salutari, Claudio Lentini Campallegio, Elena Bruno, Jordi Arbiol, Giorgia Franzò, Salvatore Mirabella, Vincenzina Strano, M. Chiara Spadaro Affiliations: Catalan Institute of Nanoscience and Nanotechnology (ICN2), CNR, ICREA, University of Catania Link: http://arxiv.org/abs/2601.06509v2 Summary: The study synthesized ZnO/ZnS heterostructured nanomaterials on nickel foam (NF) and graphene paper (GP) via a hydrothermal method and systematically evaluated their energy storage performance. Scanning and transmission electron microscopy combined with energy-dispersive spectroscopy revealed that after sulfidation, cubic sphalerite ZnS nanoparticles formed on the surface of ZnO nanorods, constructing a heterostructure. Cyclic voltammetry tests showed that the ZnO/ZnS electrode loaded on NF exhibited significant pseudocapacitive behavior, whereas the GP-based electrode displayed only pure capacitive characteristics, indicating that the NF substrate itself plays a dominant role in the pseudocapacitive response. Further Mott-Schottky and open-circuit potential measurements revealed that the ZnS decoration layer acts as a hole reservoir, effectively enhancing the charge storage efficiency of NF. The study elucidated a synergistic mechanism between the substrate and nanomaterial: the hole storage capability of ZnS enhances the redox reactivity of NF, thereby significantly improving overall electrochemical performance. This work provides key insights into understanding the substrate contribution and the role of heterostructures in electrochemical energy storage.\n","permalink":"https://nickelates.uk/en/posts/2026-01-10-arxiv-daily/","summary":"\u003cblockquote\u003e\n\u003cp\u003e\u003cstrong\u003eDaily Overview\u003c/strong\u003e:\nDear readers, welcome to today\u0026rsquo;s overview of the latest papers in the field of nickel-based superconductivity. The highlight of today\u0026rsquo;s work focuses on a deeper understanding of the electronic structure of hybrid Ruddlesden–Popper nickelates. In [1], a theoretical study employing a molecular orbital basis to treat the quarter-filled bilayer system reveals the emergence of Kugel–Khomskii physics and predicts a novel maximal spin-layer entangled phase, providing a specific theoretical framework for understanding composite entanglement in bilayer nickelate superconductors. Additionally, [5] investigates the coexistence of superconductivity and charge density waves (CDW) in correlated systems using the Green\u0026rsquo;s function method, exploring the impact of next-nearest-neighbor hopping on competition—a topic closely related to the interplay between CDW and superconductivity in nickel-based superconductors, and thus worthy of attention.\n\u003cstrong\u003earXiv submission processing window\u003c/strong\u003e: 2026-01-09 21:54 to 2026-01-10 17:32 UTC.\u003c/p\u003e","title":"arXiv Daily: nickelate superconductors 2026-01-10"},{"content":" Daily Overview: Today’s highlights focus on several studies that, while not directly addressing nickelates, investigate physical mechanisms highly relevant to core issues in nickel-based superconductivity. Among them, the research on Jahn-Teller effect-driven lifting of molecular orbital degeneracy and orbital liquid state in NbSeI provides a microscopic picture for understanding the coupling between orbital order and structural distortion in nickelates. The coexistence of Cr-kagome flat bands and Yb-4f correlated flat bands in YbCr₆Ge₆ offers an important analogy for the mechanism of superconductivity driven by hybridization between wide and narrow bands in nickelates. Meanwhile, the symmetry engineering design of perovskite altermagnets provides methodological insights for controlling magnetoelectric coupling in nickel-based heterostructures. Collectively, these works expand the understanding of the origin of unconventional superconductivity in correlated electron systems from the perspectives of electronic correlations, orbital physics, and symmetry control. arXiv submission processing window: 2026-01-08 20:22 to 2026-01-09 19:29 UTC.\n1. NiTi Single Crystal Growth by Micro-Pulling-Down Method: Experimental Setup and Material Characterization Relevance Score: 3.7047 Authors: Timon Sieweke, Chris Luther, Martin Wortmann, Lauritz Schnatmann, Felicitas Werner, Olga Kuschel, Laila Bondzio, Inga Ennen, Judith Bünte, Karsten Rott, Oluwaseyi Oluwabi, Moritz Loewenich, Joachim Wollschläger, Andreas Hütten, Jan Frenzel, Gabi Schierning, Alexander Kunzmann Affiliations: University of Duisburg-Essen, Center for Nanointegration Duisburg-Essen (CENIDE) and Nano Energie Technik Zentrum (NETZ), Research Alliance Ruhr, Bielefeld University, University of Osnabrück, Ruhr University Bochum Link: http://arxiv.org/abs/2601.05645v1 Summary: In this study, a self-made micro-pulling-down (μPD) apparatus was constructed for growing NiTi shape memory alloy single crystals. The device operates under vacuum, pulling crystals downward through a small orifice at the bottom of the crucible, and effectively reduces oxygen contamination by utilizing the low density of oxides, which float on the melt surface. A graphite crucible heated by direct current power supply was employed, and with a millimeter-sized orifice and adjustable pulling rate, rapid and flexible single crystal preparation was achieved. The grown NiTi crystals were comprehensively characterized using electron backscatter diffraction (EBSD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), hot gas extraction, and differential scanning calorimetry (DSC). The results demonstrate that the μPD method can successfully produce NiTi single crystals, and since the phase transformation characteristics are highly sensitive to doping, this approach facilitates the introduction of various dopant elements during growth, thereby providing an effective material preparation route for further in-depth study of martensitic transformation and its applications.\n2. Topological Superconductivity in Altermagnetic Heterostructures on a Honeycomb Lattice Relevance Score: 3.6236 Authors: George McArdle, Brian Kiraly, Peter Wadley, Adam Gammon-Smith Link: http://arxiv.org/abs/2601.05662v1 Summary: By constructing a heterostructure model of an alternating magnet and superconductor on a honeycomb lattice, this study demonstrates that the topological superconducting state depends on the underlying lattice structure. Using a tight-binding model, we find that the topological phase diagram is richer than that on a square lattice, including chiral edge modes corresponding to nonzero Chern numbers and Majorana corner modes that signify higher-order topological superconducting phases. The emergence of corner modes requires sublattice asymmetry, such as asymmetric hopping or sublattice energy differences, while the d-wave symmetry of the exchange coupling also influences the topological phases. Analysis of disorder effects shows that edge modes are topologically robust against vacancies and other boundary defects, but corner modes are sensitive to microscopic details: vacancies can generate low-energy bound states that are difficult to distinguish from corner modes. This work indicates that careful consideration of lattice structure and disorder is necessary for experimental realization, and that the honeycomb lattice itself can provide new topological physics distinct from that of square lattices.\n3. Observation of magnon torques mediated by orbital hybridization at the light metal/antiferromagnetic insulator interface Relevance Score: 3.6187 Authors: Yuchen Pu, Guoyi Shi, Hua Bai, Xinhou Chen, Chenhui Zhang, Zhaohui Li, Mehrdad Elyasi, Hyunsoo Yang Affiliations: National University of Singapore, Tohoku University Link: http://arxiv.org/abs/2601.05725v1 Summary: In Cr/NiO/ferromagnet heterostructures, researchers have observed magnon torques arising from interfacial orbital hybridization and inversion symmetry breaking, with an effective spin Hall conductivity of 2.45 × 10^5 ħ/(2eΩm), twice that of the best conventional magnon torque systems. This approach leverages the orbital Hall effect or orbital Rashba-Edelstein effect of the light metal Cr, converting interfacial orbital angular momentum accumulation into spin angular momentum, thereby exciting magnons in NiO and exerting torque on the adjacent ferromagnetic layer. Experiments have achieved magnetization switching of a perpendicularly magnetized CoFeB layer at room temperature with a switching power density as low as 0.136 mW/μm². The magnon torque efficiency varies with NiO thickness, peaking at 0.097 at 25 nm, with a fitted magnon diffusion length of 28.9 nm. This work not only significantly enhances the efficiency of magnon torques but also provides critical experimental evidence for understanding the microscopic mechanism of magnon injection, demonstrating a novel pathway for efficient magnetization manipulation without the need for materials with strong spin-orbit coupling.\n4. Molecular Orbital Degeneracy Lifting in a Tetrahedral Cluster System NbSeI Relevance Score: 3.6128 Authors: Keita Kojima, Youichi Yamakawa, Ryutaro Okuma, Shunsuke Kitou, Hayato Takano, Jun-ichi Yamaura, Yusuke Tokunaga, Taka-hisa Arima, Yoshihiko Okamoto Affiliations: the University of Tokyo, Nagoya University Link: http://arxiv.org/abs/2601.05562v1 Summary: In NbSeI, the molecular orbital degeneracy of Nb₄ tetrahedral clusters is lifted by two distinct mechanisms: below 106 K, the system undergoes a cooperative Jahn-Teller distortion to form an orthorhombic molecular orbital ordered insulator, where the tetrahedra distort in a three-in-one-out pattern, splitting the triply degenerate t₂ molecular orbitals into a singlet low-energy orbital and a doublet high-energy orbital, with the two 4d electrons occupying the low-energy orbital to yield a nonmagnetic state; above 106 K, the average crystal structure reverts to face-centered cubic symmetry, but X-ray diffraction analysis reveals significant local displacements at Nb sites (approximately 0.06–0.08 Å), indicating that the tetrahedra still undergo uncooperative Jahn-Teller distortions comparable in magnitude to those at low temperatures, with no long-range superstructure or strong diffuse scattering, possibly corresponding to a molecular orbital liquid or orbital frozen state. Both mechanisms render the system a nonmagnetic insulator, in stark contrast to the flat-band metal predicted by the average structure, while first-principles calculations and tight-binding models show that the narrow t₂ band primarily arises from antibonding molecular orbitals of Nb₄ clusters, with strong breathing-type structural distortions leading to weak intercluster coupling.\n5. Noncollinear spin structure in Dy-doped classical ferrimagnet Relevance Score: 3.5551 Authors: Anupam K. Singh, Katayoon Mohseni, Verena Ney, Andreas Ney, Yicheng Guan, Ilya Kostanovski, Malleshwararao Tangi, Mostafa I. S. Marzouk, Manuel Valvidares, Pierluigi Gargiani, Jean-Marc Tonnerre, P. F. Perndorfer, P. A. Buczek, Arthur Ernst, Holger L. Meyerheim, Stuart S. P. Parkin Link: http://arxiv.org/abs/2601.05762v1 Summary: Using soft X-ray spectroscopy (XMCD and XRMR) combined with theoretical calculations, a helical non-collinear spin structure was discovered in Dy-doped NiZAF thin films. XMCD and Kerr measurements revealed a significant enhancement of out-of-plane magnetic moments at low temperatures (\u0026lt;200 K), indicating a spin tilting from in-plane to out-of-plane, with spin tilt angles of approximately 29° and 44° for Fe and Ni, respectively, forming a non-collinear arrangement. XRMR directly unveiled the helical spin structure, stemming from local strain fields induced by Dy doping that break inversion symmetry and thereby elicit the Dzyaloshinskii-Moriya interaction. The Dy ions themselves do not contribute net magnetization. This study realizes a non-collinear spin structure in spinel ferrites, providing a new pathway for exploring chiral magnetic domains and topological spin textures, with potential applications in low-damping oxide spintronic devices.\n6. Intertwined atomic-nanoscale-microscale structures via intralayer anisotropic Fe-chains in the layered ferromagnet FePd2Te2 Relevance Score: 3.4688 Authors: Manyu Wang, Chang Li, Bingxian Shi, Shuo Mi, Xiaoxiao Pei, Shuming Meng, Yanyan Geng, Fei Pang, Rui Xu, Li Huang, Wei Ji, Hong-Jun Gao, Peng Cheng, Le Lei, Zhihai Cheng Affiliations: Henan Academy of Sciences, Chinese Academy of Sciences, Renmin University of China Link: http://arxiv.org/abs/2601.05481v1 Summary: Using scanning tunneling microscopy and atomic force microscopy, this study directly reveals atomic-to-nano-to-microscale hierarchical structures driven by intralayer anisotropic Fe chains in the layered ferromagnetic crystal FePd₂Te₂. Experimentally observed orthogonal corrugation morphologies at multiple scales originate from twin-domain effects dictated by Fe chain orientations. Atomic-scale imaging further resolves Fe chains in the middle sublayer and two types of Te atoms in the top sublayer, indicating that Pd atoms/vacancies play a crucial role in the formation of intralayer anisotropic Fe chains and interlayer structural alignment. Based on a model of Pd atoms filling Pd vacancies within the layer, thermally induced and strain-related surface layer structural transitions are discussed. This work provides deep insights into understanding this exotic layered magnetic material and opens new perspectives for tuning its anisotropic structures and properties from atomic to micrometer scales.\n7. Symmetry-Driven Unconventional Magnetoelectric Coupling in Perovskite Altermagnets: From Bulk to the Two-Dimensional Limit Relevance Score: 3.4026 Authors: Zhou Cui, Ziye Zhu, Xunkai Duan, Bowen Hao, Xianzhang Chen, Jiayong Zhang, Tong Zhou Link: http://arxiv.org/abs/2601.05602v1 Summary: This study systematically investigates the dimensional evolution from bulk to two-dimensional (2D) limit and the unconventional magnetoelectric coupling mechanisms in perovskite altermagnets through symmetry analysis and first-principles calculations. The results reveal that altermagnetism can persist at the 2D limit but is strongly constrained by the magnetic configuration, with only C-type antiferromagnetic order supporting this property. Using mode decomposition calculations, the authors uncover the microscopic mechanism by which symmetry-restricted multimode coupling simultaneously controls both ferroelectric polarization and altermagnetic spin splitting. To address the limitation that non-C-type antiferromagnetic orders cannot generate altermagnetism in 2D systems, the paper proposes strategies such as superlattice engineering, shear strain, electric fields, and substrate engineering to expand feasible systems by breaking specific symmetries, even achieving ferroelectric fully compensated ferrimagnets. These findings highlight the critical role of dimensionality in symmetry-driven magnetoelectric coupling and provide theoretical guidance for designing electrically controllable 2D spintronic and multiferroic devices.\n8. On the Novel Superfluidity in the Second Layer of $^4$He on Graphite Relevance Score: 3.3286 Authors: Jun Usami, Hiroshi Fukuyama Link: http://arxiv.org/abs/2601.05719v1 Summary: By simultaneously measuring the torsional oscillator response and heat capacity of second-layer ⁴He films on the same graphite substrate down to 30 mK, this study resolves the density scale uncertainty previously caused by substrate heterogeneity and provides the first direct evidence for a novel superfluid phase within the quantum liquid crystal (QLC) region. This phase exhibits both superfluidity and enhanced viscoelasticity over a finite density range, lacks a well-defined Berezinskii-Kosterlitz-Thouless transition temperature, and displays a logarithmic temperature dependence of the superfluid density. Analysis using a random Josephson network model indicates that this anomalous behavior arises from percolation of superfluid islands induced by the graphite microcrystalline structure rather than from an intrinsic property of the system. The experiments also find no superfluid response in the pure solid phase, ruling out supersolidity. These results strongly support the superfluid liquid crystal hypothesis and clarify previous controversies regarding the origin of superfluidity in the second layer of ⁴He.\n9. Thermally Configurable Multi-Order Polar Skyrmions in Multiferroic Oxide Superlattices Relevance Score: 3.3172 Authors: Kefan Liu, Yuhui Huang, Xiangwei Guo, Yongjun Wu, Juan Li, Zijian Hong Link: http://arxiv.org/abs/2601.05950v1 Summary: This study employs BiFeO₃ (BFO)-based multiferroic superlattices as a model system and proposes, through phase-field simulations, a thermal modulation strategy for stabilizing and reversibly tuning the topological order of multi-order polar skyrmions. The results reveal that temperature variation can drive a sequential transition from polar solitons to 1π, 2π, 3π, and 4π skyrmion states; analysis of a closed heating-cooling path indicates that the 2π skyrmion exhibits the widest thermal stability window, extending up to 600 K. Leveraging this robustness, doping BFO with 2% Sm effectively reduces the phase transition temperature, enabling stable existence of the 2π skyrmion at room temperature. This work not only deepens the fundamental understanding of multi-order polar topological structures but also provides a feasible strategy for the application of tunable topological configurations in practical memory devices.\n10. Cooperative concurrence of 4f and 3d flat bands in kagome heavy-fermion metal YbCr6Ge6 Relevance Score: 3.3139 Authors: Wenxin Lv, Pengcheng Ma, Tianqi Wang, Shangjie Tian, Ying Ma, Shouguo Wang, Xiao Zhang, Zhonghao Liu, Hechang Lei Affiliations: Anhui University, Beijing University of Posts and Telecommunications, Ningbo University, Renmin University of China Link: http://arxiv.org/abs/2601.05829v1 Summary: This paper reports on YbCr6Ge6, a material simultaneously featuring a Cr-kagome lattice and Yb-4f electrons, which exhibits heavy-fermion behavior and an antiferromagnetic ground state with a transition temperature TN = 3 K, significantly higher than other Yb-containing kagome metals. Angle-resolved photoemission spectroscopy measurements reveal the coexistence near the Fermi level of a geometric flat band arising from the Cr-kagome lattice and a correlated flat band derived from localized Yb-4f electrons. More importantly, the hybridization between the Yb-4f flat band and the kagome conduction band, together with the high density of states of the Cr-kagome flat band at the Fermi level, provides a microscopic mechanism for the heavy-fermion behavior and enhanced antiferromagnetism. This study demonstrates that kagome heavy-fermion metals not only enable the synergistic coexistence of two distinct types of flat bands but also offer an ideal material platform for exploring novel correlated topological quantum phenomena.\n11. Crystalline-dependent magnon torques in all-sputtered Hf/Cr2O3/ferromagnet heterostructures Relevance Score: 3.3113 Authors: Yuchen Pu, Guoyi Shi, Chenhui Zhang, Xinhou Chen, Hanbum Park, Hyunsoo Yang Affiliations: National University of Singapore Link: http://arxiv.org/abs/2601.05737v1 Summary: We fabricated Hf/antiferromagnetic Cr2O3/ferromagnet sandwich structures and systematically investigated the dependence of magnon torque on the crystal structure of Cr2O3. Experimental results show that the magnon torque is significantly enhanced when the Néel vector of Cr2O3 is parallel to the spin polarization direction generated in Hf, while it is suppressed when the two are perpendicular. The magnon torque efficiency was estimated to be -0.134 via in-plane second harmonic Hall measurements, and this torque was used to achieve perpendicular magnetization switching of CoFeB with a critical switching current density of 4.09×10^7 A/cm². Additionally, the spin angular momentum loss caused by the insertion of Cr2O3 is lower than that of polycrystalline NiO. This work reveals the modulation effect of the antiferromagnetic crystal structure on magnon torque and expands the potential application of magnon torque in low-power spintronic devices.\n12. Anomalous pressure dependence of the bulk modulus and Yb valence in cubic YbPd Relevance Score: 3.3069 Authors: B. Tegomo Chiogo, V. Balédent, J. -P. Rueff, E. Saïman, V. Poree, T. Schweitzer, D. Wong, C. Schulz, T. Mazet, A. Chainani, D. Malterre, K. Habicht Link: http://arxiv.org/abs/2601.05766v2 Summary: This study utilizes resonant X-ray emission spectroscopy (RXES) combined with the Birch-Murnaghan equation of state to analyze the anomalous variations in the Yb valence state and bulk modulus of cubic YbPd under pressure, with a particular focus on behavior near the charge-order (CO) transition. In the low-temperature (30 K) CO phase, the Yb 4f valence state remains nearly unchanged at pressures below approximately 1.5 GPa, and then gradually increases; whereas in the room-temperature normal phase, the Yb valence state exhibits an anomalous decrease in the low-pressure region (\u0026lt;1.6 GPa), followed by saturation, with no structural phase transition occurring throughout this process. X-ray diffraction measurements show that the unit cell volume decreases with increasing pressure, with an inflection point observed at approximately 1.6 GPa. Compressibility analysis indicates lattice stiffening before the inflection point, followed by counterintuitive pressure-induced softening after it, with the pressure derivative of the bulk modulus changing from positive to negative. This compressibility minimum behavior is analogous to the compressibility maximum observed during structural phase transitions such as the γ-α transition in cerium metal, but with the opposite sign. The study suggests that the coupling between the Yb valence state and lattice stiffness may originate from the Kondo volume collapse mechanism, where the Kondo temperature increases rapidly at low pressures and then saturates, leading to a transition from lattice stiffening to softening. These findings reveal YbPd as an ideal platform for simulating the Kondo volume collapse model in strongly correlated electron systems.\n13. Structural and magnetic properties of co-sputtered epitaxial Fe-Sn kagome thin films Relevance Score: 3.2538 Authors: Callum Brennan-Rich, Sean M. Collins, Stuart Micklethwaite, Zabeada Aslam, Trevor Almeida, Stephen McVitie, Rik M. Drummond-Brydson, Christopher H. Marrows Link: http://arxiv.org/abs/2601.05735v1 Summary: This study employed co-sputtering to grow high-quality epitaxial Fe-Sn thin films on sapphire substrates with a platinum seed layer, and by adjusting the deposition rates of Fe and Sn, Fe₃Sn₂, FeSn, and their mixed phases were prepared. The crystal structures of the films were characterized using X-ray diffraction and four-dimensional scanning transmission electron microscopy, and 4D-STEM phase mapping quantitatively confirmed that the phase content of each film was consistent with expectations. Magnetic measurements revealed that the magnetization behavior of the pure-phase samples corresponded to the ferromagnetic phase content, while the mixed-phase films exhibited unique temperature-dependent coercivity behaviors not observed in the pure phases. The results indicate that this method enables precise control over the phase composition of the films, and new magnetic phenomena were discovered in the mixed phases, highlighting the importance of controlling growth parameters to achieve the target phases.\n14. Layered CrGe1-xSe3+y with Cr Kagome Lattice and Antiferromagnetic Ordering Relevance Score: 3.2398 Authors: Jeremy G. Philbrick, Chaoguo Wang, Xin Gui, Tai Kong Affiliations: The University of Arizona, University of Pittsburgh Link: http://arxiv.org/abs/2601.05360v1 Summary: A new layered material, CrGe₁₋ₓSe₃₊ᵧ, was synthesized and characterized, with its crystal structure determined by single-crystal X-ray diffraction and transmission electron microscopy. The material crystallizes in the space group R-3m, featuring a bilayer Kagome lattice of chromium atoms intercalated between disordered Ge-Se layers. Magnetic susceptibility measurements reveal antiferromagnetic ordering below approximately 50 K, in stark contrast to the ferromagnetic behavior of the isostructural compound CrGeTe₃. The effective magnetic moment of chromium is about 3.9 μB/Cr, consistent with the Cr³⁺ oxidation state. This finding indicates that despite theoretical predictions of a ferromagnetic CrGeSe₃ phase analogous to CrGeTe₃, the actual synthesis preferentially forms this antiferromagnetic Kagome phase, thereby limiting the existence of a pure ferromagnetic phase. This work expands the understanding of the chemical stability boundaries of two-dimensional magnetic materials.\n15. Unraveling the effects of anionic vacancies and temperature on mechanical properties of NbC and NbN: Insights from Quantum Mechanical Study Relevance Score: 3.2309 Authors: P. W. Muchiri, K. K. Korir, N. W. Makau, M. O. Atambo, G. O. Amolo Affiliations: Moi University, The Technical University of Kenya, University of Eldoret Link: http://arxiv.org/abs/2601.05712v1 Summary: This study systematically investigates the effects of temperature (300–1500 K) and anion vacancies on the mechanical properties of rock-salt, zinc-blende, and wurtzite NbC and NbN using ab initio molecular dynamics simulations. The results reveal that elastic constants, bulk modulus, shear modulus, and Young’s modulus decrease nonlinearly with increasing temperature and defect concentration. Hardness and toughness analyses based on the Pugh ratio and Poisson’s ratio indicate a ductile-to-brittle transition sensitive to structure, defect level, and thermal effects. Vacancy migration energies calculated using the nudged elastic band method exhibit significant structural dependence, with the rock-salt structure showing the highest migration barrier and the wurtzite structure the lowest. These findings elucidate the interplay between defects and temperature in NbC and NbN, providing theoretical guidance for optimizing their performance in high-temperature and wear-resistant applications.\n16. Coupled Spin-lattice Dynamics across a Magnetostructural Phase Transition Relevance Score: 3.0941 Authors: Lokanath Patra, Zeyu Xiang, Yubi Chen, Bolin Liao Link: http://arxiv.org/abs/2601.05458v1 Summary: This study systematically investigates the coupled evolution of magnetization and phonon dispersion across the magnetostructural phase transition in MnAs using first-principles spin-lattice dynamics simulations. The simulations quantitatively reproduce the experimentally observed Curie temperature, lattice contraction, and free-energy crossing between the hexagonal and orthorhombic phases. It is found that below the Curie temperature, the magnetic-field-induced hardening of soft phonon modes contributes significant lattice entropy, enhancing the total isothermal entropy change by approximately 23% under a 5 T field. However, the lattice entropy change associated with the structural phase transition itself has an opposite sign, partially counteracting the field-induced phonon hardening contribution, and this competition mechanism explains the long-standing controversy in magnetocaloric entropy measurements. Furthermore, the strong field dependence of the phonon spectrum near the phase transition endows the lattice thermal conductivity with substantial tunability, highlighting MnAs as a promising platform for magnetic-field-controlled thermal switches. This work establishes a unified microscopic picture of spin-lattice coupling in first-order magnetocaloric materials, providing a principle-based foundation for designing enhanced thermal and heat transport functionalities.\n17. Mechanical control of magnetic exchange and response in GdRu$_2$Si$_2$: A computational study Relevance Score: 3.0821 Authors: Sagar Sarkar, Rohit Pathak, Arnob Mukherjee, Anna Delin, Olle Eriksson, Vladislav Borisov Affiliations: KTH Royal Institute of Technology, Uppsala University Link: http://arxiv.org/abs/2601.05696v1 Summary: This study systematically investigates the modulation of magnetism in the centrosymmetric material GdRu₂Si₂ under uniaxial strain using first-principles density functional theory. DFT calculations first reveal the significant sensitivity of exchange interactions and magnetocrystalline anisotropy to specific structural distortions; these parameters are then incorporated into a classical spin model to construct complete magnetic phase diagrams under compressive and tensile strains. The key finding is that approximately 2% compressive strain serves as an effective tuning parameter, substantially expanding the stability region of topologically nontrivial phases driven by (\\vec{Q}{100}) by shifting the critical magnetic field and raising the energy scale of the favorable magnetic wavevector, whereas tensile strain promotes an alternative magnetic ordering wavevector (\\vec{Q}{110}), leading to distinctly different ground-state behavior. This work not only quantitatively elucidates the structural-magnetic coupling mechanism in GdRu₂Si₂ but also establishes strain engineering as a powerful tool for manipulating and optimizing topologically nontrivial magnetic phases in centrosymmetric magnets.\n18. Anomalously High Phonon Thermal Conductivity Driven by Weak Electron-Phonon Coupling in Weyl Semimetals TaAs and TaP Relevance Score: 3.0555 Authors: Xianyong Ding, Xin Jin, Dengfeng Li, Jing Fan, Peng Yu, Xiaoyuan Zhou, Xiaolong Yang, Rui Wang Link: http://arxiv.org/abs/2601.05522v2 Summary: By solving the Boltzmann transport equation using first-principles calculations, it is found that heat transport in the Weyl semimetals TaAs and TaP is dominated by phonons, overturning the conventional understanding that electrons dominate thermal conductivity in metals. Due to the extremely low density of electronic states near the Fermi level caused by Weyl nodes, electron-phonon coupling is very weak. Meanwhile, the acoustic bunching and a wide frequency gap in the phonon spectrum suppress both three-phonon and four-phonon scattering processes. Consequently, the phonon thermal conductivity of TaP along the z-axis at room temperature reaches as high as 171 W/mK, more than five times its electronic thermal conductivity of 33 W/mK; in TaAs, the phonon contribution also significantly exceeds the electronic contribution. The strong phonon thermal conductivity causes the Lorenz number to deviate substantially from the Wiedemann–Franz law, and this phonon-dominated heat transport appears to be universal among topological semimetals. This work deepens the understanding of heat transport mechanisms in topological semimetals and provides new insights for discovering high-thermal-conductivity materials.\n19. Symmetry-engineered and electrically tunable in-plane anomalous Hall effect in oxide heterostructures Relevance Score: 3.0431 Authors: Kunjie Dai, Zhen Wang, Wenfeng Wu, Feng Jin, Enda Hua, Nan Liu, Jingdi Lu, Jinfeng Zhang, Yuyue Zhao, Linda Yang, Kai Liu, Huan Ye, Qiming Lv, Zhengguo Liang, Ao Wang, Dazhi Hou, Yang Gao, Shengchun Shen, Jing Tao, Liang Si, Wenbin Wu, Lingfei Wang Affiliations: Northwest University, Chinese Academy of Sciences, University of Science and Technology of China Link: http://arxiv.org/abs/2601.05462v1 Summary: This study constructs a symmetry engineering platform based on CaRuO₃/La₂/₃Ca₁/₃MnO₃/CaRuO₃ epitaxial heterojunctions on NdGaO₃(110) substrates, realizing electrically tunable in-plane anomalous Hall effect (IP-AHE). Through the synergistic interplay of mirror symmetry breaking and in-plane uniaxial magnetic anisotropy, the IP-AHE signal is explicitly coupled to the symmetry breaking induced by the CaRuO₃ buffer layer and faithfully reproduces the ferromagnetic hysteresis loop. By employing ionic liquid gating to achieve reversible protonation, the symmetry breaking is in situ reconfigured, enabling broad-range electrical modulation and on-off switching of the IP-AHE. This platform transforms stringent mirror symmetry breaking constraints into an effective control knob, opening new pathways for exploring nontrivial magnetic orders in planar geometries and developing programmable Hall-effect functional devices.\n20. Sizes of Ferroelectricity Appearance and Disappearence in Nanosized Hafnia-Zirconia:Landau-type Theory Relevance Score: 3.0342 Authors: Anna N. Morozovska, Eugene A. Eliseev, Sergei V. Kalinin, Maksym V. Strikha Affiliations: National Academy of Sciences of Ukraine, University of Tennessee, Taras Shevchenko National University of Kyiv Link: http://arxiv.org/abs/2601.06267v1 Summary: Using the Landau-Ginzburg-Devonshire free energy functional (incorporating high-order powers of polar, nonpolar, and antipolar order parameters, as well as trilinear and biquadratic coupling terms), this study analytically calculates the strain-dependent critical dimensions for the emergence and disappearance of out-of-plane spontaneous polarization in epitaxial hafnium oxide films and nanodots. The results show that the critical thickness for ferroelectric disappearance is determined by the size dependence of the depolarization field and correlation effects, whereas the critical thickness for ferroelectric emergence is governed by the size dependence of the effective misfit strain, where the onset of misfit dislocations and lateral strain relaxation must be considered. The theory analyzes the effects of size and misfit strain on the phase diagram and polarization switching barrier, and indicates that the derived analytical expressions can be extended to hafnium-zirconium oxide solid solutions provided that the relevant free energy parameters can be obtained from first-principles calculations.\n","permalink":"https://nickelates.uk/en/posts/2026-01-09-arxiv-daily/","summary":"\u003cblockquote\u003e\n\u003cp\u003e\u003cstrong\u003eDaily Overview\u003c/strong\u003e:\nToday’s highlights focus on several studies that, while not directly addressing nickelates, investigate physical mechanisms highly relevant to core issues in nickel-based superconductivity. Among them, the research on Jahn-Teller effect-driven lifting of molecular orbital degeneracy and orbital liquid state in NbSeI provides a microscopic picture for understanding the coupling between orbital order and structural distortion in nickelates. The coexistence of Cr-kagome flat bands and Yb-4f correlated flat bands in YbCr₆Ge₆ offers an important analogy for the mechanism of superconductivity driven by hybridization between wide and narrow bands in nickelates. Meanwhile, the symmetry engineering design of perovskite altermagnets provides methodological insights for controlling magnetoelectric coupling in nickel-based heterostructures. Collectively, these works expand the understanding of the origin of unconventional superconductivity in correlated electron systems from the perspectives of electronic correlations, orbital physics, and symmetry control.\n\u003cstrong\u003earXiv submission processing window\u003c/strong\u003e: 2026-01-08 20:22 to 2026-01-09 19:29 UTC.\u003c/p\u003e","title":"arXiv Daily: nickelate superconductors 2026-01-09"},{"content":" Daily Overview: Dear readers, welcome to today’s research highlights in the nickel-based superconductivity field. Although none of the papers in today’s list directly focus on nickelate superconductors, several studies are highly relevant to the core issues currently facing nickel-based superconductivity, particularly in terms of electronic structure, superconducting mechanisms, and computational methods. Among them, RIXS studies on the local electronic structure of Ni²⁺ in the pyrochlore antiferromagnet NaCaNi₂F₇ reveal that its octahedral environment is highly robust against A-site disorder, allowing comparisons to the electronic structure stability of the NiO₂ planes in nickel-based superconductors in terms of such local effects. Research on the condensation mechanism of cuprate superconductors reveals bosonic statistical characteristics of strong coupling between pairon excitations and the condensate, and the proposed picture of an energy-dependent gap proportional to the spin-exchange energy may provide insights into understanding similar spin-fluctuation-mediated pairing in nickelates. The discovery of chiral topological order on the surface of the cluster Mott insulator Nb₃Br₈ and its explanation of the zero-field diode effect suggest that surface states in layered correlated systems can give rise to topological superconducting phases under weak correlations, echoing possible interfacial superconducting mechanisms in nickel-based superconductor thin films. Furthermore, the hDMFT method, which achieves full five-orbital DMFT calculations for Ba₂IrO₄ and Ba₂RhO₄, significantly reduces computational costs and provides a feasible pathway for future multi-orbital correlated calculations involving the full d manifold in nickelates. arXiv submission processing window: 2026-01-08 03:40 to 2026-01-08 19:07 UTC.\n1. Studies of superconductivity of Fe chalcogenides in films grown by PLD technique Relevance Score: 4.1255 Authors: Atsutaka Maeda, Tomoki Kobayashi, Fuyuki Nabeshima Link: http://arxiv.org/abs/2601.04558v1 Summary: This review summarizes the superconductivity research on iron chalcogenide thin films (FeSe, FeSe1-yTey, etc.) grown by pulsed laser deposition (PLD), with a focus on the electronic phase diagram, normal-state and superconducting properties, and comparisons with bulk single crystals, molecular beam epitaxy (MBE) thin films, and exfoliated crystals. It is noted that there exist three types of superconductivity in Fe-based chalcogenide superconductors: one with both electron and hole Fermi surfaces and a Tc of about 40 K, a second type with only electron Fermi surfaces and Tc between 40 and 50 K, and a third type potentially realized in ultrathin films on oxide substrates with high Tc (\u0026gt;65 K); however, most evidence for high Tc currently comes from spectroscopic measurements such as STM and ARPES, while transport measurements yield zero-resistance temperatures of only about 30 K, and superconductivity above 65 K has not yet been confirmed by electrical resistance measurements. The advantages of PLD films include the ability to prepare large-area single crystals, non-equilibrium synthesis to extend the composition range (e.g., achieving full-composition FeSe1-yTey with Tc enhanced by a factor of 1.5 compared to bulk), and systematic tuning of physical properties via substrate strain. The study reveals that under strain control, the trends of Tc and nematic transition temperature in epitaxial films are consistent with those in bulk single crystals, demonstrating that they belong to the same world; carrier density increases with compressive strain, accompanied by a corresponding rise in Tc. The electronic phase diagram shows that Te substitution causes a sharp increase in Tc in the non-nematic region of FeSe, whereas S substitution only leads to a gradual decrease in Tc, with the emergence of an anomalous short-range magnetic order. It is concluded that thin films are comparable to bulk materials, and strain is the key to understanding the enhancement of superconductivity, yet the mechanism of interface-induced high Tc and its transport verification remain important challenges.\n2. Discovery of a new weberite-type antiferroelectric: La3NbO7 Relevance Score: 4.0846 Authors: Louis Alaerts, Jesse Schimpf, Xinyan Li, Jiongzhi Zheng, Ella Banyas, Jeffrey B. Neaton, Sinéad M. Griffin, Yimo Han, Lane W. Martin, Geoffroy Hautier Affiliations: University of California, Berkeley, Lawrence Berkeley National Laboratory, Rice University, Dartmouth College Link: http://arxiv.org/abs/2601.04916v2 Summary: Through large-scale first-principles screening, researchers identified a new family of weberite-type antiferroelectrics among approximately 5,000 materials, with La₃NbO₇ predicted to exhibit antiferroelectricity. Synthesis and characterization of epitaxial thin films confirmed this prediction: the hysteresis loops displayed the double-loop characteristic of antiferroelectrics, and an antipolar ground-state structure was observed via transmission electron microscopy. The antiferroelectric mechanism in La₃NbO₇ is relatively simple, belonging to the Kittel type, involving a single soft-mode motion of niobium atoms within oxygen octahedra, resulting in a small volume change during the field-induced phase transition. This material combines a high threshold field with a high breakdown field (approximately 6 MV/cm), offering potential for energy storage applications. Furthermore, the weberite-type family allows flexible tuning of electrical properties through substitution at the rare-earth or niobium/tantalum sites, demonstrating a successful example of data-driven discovery of new antiferroelectrics from theory to experiment and providing a blueprint for the future design of ferroic materials.\n3. Acoustic signatures of the field-induced electronic-topological transitions in YbNi$_4$P$_2$ Relevance Score: 4.0717 Authors: E. -O. Eljaouhari, B. V. Schwarze, K. Kliemt, C. Krellner, F. Husstedt, J. Wosnitza, S. Zherlitsyn, G. Zwicknagl, J. Sourd Link: http://arxiv.org/abs/2601.05126v1 Summary: We investigated the magnetoelastic properties of YbNi4P2 single crystals at low temperatures and under magnetic fields along the [001] direction using ultrasonic measurements, observing a series of sound velocity anomalies consistent with previously reported cascades of electronic topological transitions. By employing both longitudinal and transverse acoustic modes, we identified multiple transitions, among which the disappearance of the 34 T quantum oscillation frequency at 6.2 T directly confirmed the vanishing of a small Fermi surface orbit. Parameters such as effective masses were obtained through analysis of quantum oscillations. Combining a microscopic model applicable to strongly correlated systems, we examined the electron-phonon coupling of each acoustic mode in reciprocal space, revealing that acoustic modes of different symmetries exhibit varying sensitivities to different transitions. The results demonstrate that the wave-vector selectivity of ultrasonic experiments can effectively probe Fermi surface reconstruction processes in strongly correlated electron systems.\n4. Stability of the Local Ni$^{2+}$ Electronic Structure to $A$-site Disorder in the Pyrochlore Antiferromagnet NaCaNi$_2$F$_7$ Relevance Score: 3.9757 Authors: M. F. DiScala, A. de la Torre, J. W. Krizan, J. Wouters, V. Bisogni, J. Pelliciari, R. J. Cava, K. W. Plumb Link: http://arxiv.org/abs/2601.05236v1 Summary: The effect of A-site disorder on the electronic structure of Ni²⁺ in the pyrochlore antiferromagnet NaCaNi₂F₇ was investigated using Ni L-edge resonant inelastic X-ray scattering (RIXS). Experimental results show that Ni²⁺ resides in a nearly ideal octahedral coordination environment, with all spectral features well described by introducing a slight trigonal compression of −200 meV under D₃d symmetry. Through fitting with a single-ion crystal-field model, anisotropic g-factors g∥ = 2.26 and g⊥ = 2.27 were extracted, yielding an effective paramagnetic moment μeff = 3.2 μB, consistent with magnetic susceptibility measurements. To model Na¹⁺/Ca²⁺ disorder, RIXS spectra were calculated based on a distribution of actual crystal-field parameters, but the results showed no significant difference compared to the disorder-free model, indicating that the local electronic structure of Ni²⁺ is highly robust against A-site disorder within experimental resolution. F K-edge RIXS confirmed the highly ionic nature of the Ni–F bonds, with a charge-transfer energy of approximately 7.6 eV. This work reveals the robustness of the NiF₆ octahedral environment in NaCaNi₂F₇, providing a benchmark for understanding the relationship between single-ion physics and magnetism on the pyrochlore lattice.\n5. Multigap nodeless superconductivity in Dirac semimetal PdTe Relevance Score: 3.9478 Authors: Fengrui Shi, Weilong Qiu, Chufan Chen, Chunqiang Xu, Yan Zhang, Hao Zheng, Yuwei Zhou, Dongting Zhang, Mengwei Xie, Huiqiu Yuan, Shiyan Li, Yang Liu, Chao Cao, Xiaofeng Xu, Xin Lu Link: http://arxiv.org/abs/2601.04712v1 Summary: This study systematically investigates the superconducting gap structure of Dirac semimetal PdTe single crystals using point-contact spectroscopy, finding that the differential conductance curves deviate from single-gap behavior and can be well fitted by a two-gap Blonder-Tinkham-Klapwijk model, yielding a large gap ΔL with 2ΔL = 3.7 k_BT_c and a small gap ΔS with 2ΔS ranging from 1.1 to 2.2 k_BT_c, along with weak interband scattering. The differences in conductance spectra at various contact points are attributed to the topological anisotropy of the Fermi surfaces corresponding to the distinct gaps. Specific heat data further support a two-gap s-wave model, with the large gap contributing approximately 90–95% of the electronic specific heat. The temperature dependence indicates that the large gap follows BCS behavior, while the small gap deviates from BCS and exhibits a long tail, suggesting that weak interband scattering leads to the closure of both gaps at the same superconducting transition temperature. The study confirms that PdTe exhibits nodeless multiband superconductivity and proposes that the large gap likely originates from the quasi-two-dimensional π band, while the small gap arises from the three-dimensional σ band.\n6. Oxygen distribution and segregation at grain boundaries in Nb and Ta-encapsulated Nb thin films for superconducting qubits Relevance Score: 3.9183 Authors: Jaeyel Lee, Dieter Isheim, Zuhawn Sung, Francesco Crisa, Sabrina Garattoni, Mustafa Bal, Cameron J. Kopas, Josh Y. Mutus, Hilal Cansizoglu, Jayss Marshall, Kameshwar Yadavalli, Dominic P. Goronzy, Mark C. Hersam, David N. Seidman, Alex Romanenko, Anna Grassellino, Akshay A. Murthy Affiliations: Rigetti Computing, Fermi National Accelerator Laboratory, Northwestern University Link: http://arxiv.org/abs/2601.05326v1 Summary: This study utilizes atom probe tomography (APT) and transmission electron microscopy (TEM) to perform atomic-scale analysis of oxygen distribution and grain boundary segregation in niobium (Nb) thin films and tantalum-coated niobium (Ta/Nb) thin films used for superconducting qubits. The results reveal that oxygen segregates at grain boundaries in both types of films, and a higher oxygen concentration within Nb grains correlates with a greater degree of segregation at grain boundaries, indicating that controlling oxygen impurities during film deposition and processing is critical for reducing grain boundary segregation. Specifically, the oxygen enrichment factor (Cgb/Cgrain) at grain boundaries in Nb films is 2.7 ± 0.3; in Ta-coated Nb films, the enrichment factor at Nb grain boundaries slightly decreases to 2.3 ± 0.3, while that at grain boundaries within the Ta capping layer itself reaches 3.0 ± 0.3. It is hypothesized that the Ta capping layer can trap oxygen, thereby influencing the inward diffusion of oxygen and its segregation behavior at grain boundaries in the underlying Nb film. Furthermore, increased oxygen concentrations both within Nb grains and at grain boundaries are associated with a suppression of the superconducting critical temperature (Tc). These comparative analyses of chemical and charge transport properties provide atomic-scale insights into a potential mechanism of decoherence in superconducting qubits.\n7. Condensation mechanism of high-$T_c$ cuprates: the key role of pairon excitations Relevance Score: 3.8565 Authors: Yves Noat, Alain Mauger, William Sacks Link: http://arxiv.org/abs/2601.04655v1 Summary: This paper reveals that the condensation mechanism in high-temperature cuprate superconductors involves strong coupling between the condensate and pairon excited states. The authors present an accessible formal framework that provides a theoretical basis for the energy-dependent gap function Δ(E), which is proportional to the effective spin-exchange energy J_eff and is free of retardation effects (such as those arising from spin fluctuations or phonon-mediated coupling). The fundamental parameters of the superconducting state are the condensation energy per pair β_c and the antinodal gap Δ_p, both of which can be quantitatively extracted by fitting quasiparticle spectra from tunneling experiments. The model also derives an explicit formula for the critical temperature applicable to arbitrary doping, revealing that T_c is proportional to β_c rather than Δ_p, in stark contrast to conventional superconductors. The numerical factor β_c/k_BT_c ≈ 2.24 originates from pair excitations of the condensate, which obey Bose statistics, and the excitation spectrum exhibits a mini-gap of approximately 1 meV. These results strongly suggest that the same all-electronic mechanism operates across the entire T_c dome.\n8. Direct Observation of the Spillover of High Magnetic Field-induced SC3 Superconductivity Outside the Spin-Polarized State in UTe2 Relevance Score: 3.7856 Authors: Zheyu Wu, Hanyi Chen, Theodore I. Weinberger, Mengmeng Long, David Graf, Andrej Cabala, Vladimir Sechovsky, Michal Valiska, Gilbert G. Lonzarich, F. Malte Grosche, Alexander G. Eaton Link: http://arxiv.org/abs/2601.04594v2 Summary: This study reports magnetotransport measurements on high-quality UTe₂ single crystals (residual resistivity ratio of 605) under steady magnetic fields up to 45 tesla with rotation in the b-c plane, unambiguously observing the spillover of the high-field-induced SC3 superconducting phase beyond the first-order phase boundary of the spin-polarized state. It is found that the low-temperature resistance drops to zero at field strengths below the high-temperature metamagnetic transition field, directly proving that part of the SC3 superconducting region extends outside the polarized paramagnetic state. This phenomenon is consistent with a theoretical model in which SC3 electron pairing is mediated by quantum critical fluctuations. In addition, a broad onset region of SC3 is observed at lower fields around approximately 27.3 tesla, coinciding with the region where the exotic linear-in-resistance behavior and the highest upper critical field and critical temperature of SC3 are observed in pulsed-field experiments, further supporting the hypothesis that SC3 originates from a quantum critical point. The results reveal a non-coincident boundary relationship between the SC3 superconducting phase and the spin-polarized state, which is significant for understanding the unconventional superconducting mechanism in UTe₂.\n9. A First-principles Study of Weyl Nodal Loop and Multiple Sets of Weyl Points in Trigonal PtBi$_2$ Relevance Score: 3.7554 Authors: Lin-Lin Wang Affiliations: Iowa State University, Ames National Laboratory Link: http://arxiv.org/abs/2601.05123v1 Summary: Using first-principles calculations combined with a tight-binding model constructed from Wannier functions, this work systematically investigates the band crossings between the valence band maximum and conduction band minimum throughout the entire Brillouin zone of the trigonal phase γ-PtBi₂. The study reveals a mirror-symmetry-protected Weyl nodal loop (WNL) and multiple sets of Weyl points (WPs). Among them, Set 1 WPs located approximately 0.07 eV above the Fermi level (EF), along with the WNL and the bulk band gap region, exhibit robustness against variations in structural parameters, whereas the number and positions of the other WPs are highly sensitive to the buckling amplitude of Bi layers—the primary difference between two experimentally determined structural parameters: with larger buckling, the number of WP sets reduces to two, while with smaller buckling, it increases to five. Furthermore, two-dimensional Fermi surfaces, Fermi arcs, and quasiparticle interference spectra for different structures are calculated, showing good agreement with angle-resolved photoemission spectroscopy and scanning tunneling spectroscopy experiments, and predicting new Fermi arc features at higher energies. This work details the evolution of the WNL, multiple WP sets, Fermi arcs, and quasiparticle interference in γ-PtBi₂, providing crucial theoretical support for understanding its topological superconductivity-related experimental observations.\n10. Correlative Ultrafast Imaging of a Propagating Photo-Driven Phase Transition Using 4D STEM Relevance Score: 3.6253 Authors: Arthur Niedermayr, Jianyu Wu, Bertina Fisher, Ido Kaminer, Jonas Weissenrieder Affiliations: Technion–Israel Institute of Technology, KTH Royal Institute of Technology Link: http://arxiv.org/abs/2601.05018v1 Summary: This paper proposes the use of ultrafast four-dimensional scanning transmission electron microscopy (U-4D STEM), combined with nanobeam electron diffraction and structured optical excitation, to achieve spatiotemporally resolved imaging of structural transitions and strain dynamics in the photoinduced phase-change material vanadium dioxide (VO₂). By recording the laser-induced insulator-metal phase transition in real time, the study directly observes the propagation of the structural phase transition on picosecond timescales along with the accompanying generation of local strains. This method enables simultaneous virtual imaging and quantitative strain mapping, revealing how atomic-scale symmetry breaking produces lattice distortions and drives macroscopic property changes. Experimental findings show that the strain field dynamically evolves with the phase transition and in turn influences the transition process, whereas conventional bright-field imaging cannot distinguish between the phase transition and mechanical responses. Ultrafast 4D STEM improves signal-to-noise ratio and reduces electron dose damage by selecting multiple diffraction spots through post-processing. This work establishes a direct correlation between electronic, structural, and mechanical responses, providing key insights into the ultrafast switching mechanisms of strongly correlated oxides under nonequilibrium conditions.\n11. Control of the MoTe$_2$ Fermi Surface by Nb Doping Relevance Score: 3.6124 Authors: Andrew P. Weber, Iñigo Robredo, Philipp Rüssmann, Maxim Ilyn, Arnaud Magrez, Philippe Bugnon, Nan Xu, Vladimir Strocov, J. Hugo Dil, J. Enrique Ortega, Julen Ibañez-Azpiroz Link: http://arxiv.org/abs/2601.05197v1 Summary: First-principles calculations and angle-resolved photoemission spectroscopy experiments demonstrate that tuning the chemical potential below 0.4 eV can significantly alter the bulk and surface electronic structures of the candidate Weyl semimetal MoTe₂. The calculations predict multiple Lifshitz transitions among electron and hole Fermi pockets with distinct orbital characters. Experiments confirm that 18% Nb substitution for Mo reduces the occupancy of bulk and (001) surface bands, effectively inducing a chemical potential shift of approximately 0.3 eV. Using polarization-controlled soft X-ray angle-resolved photoemission spectroscopy, the orbital character and dimensionality of bulk broadband are analyzed, and it is found that alkali metal deposition on the surface increases the surface band filling. These results indicate that this layered material can readily access diverse electronic property regimes through simple chemical potential tuning, providing an effective route for modulating its conductive characteristics.\n12. Optical Signatures and Quantum Geometry in Proximity-Induced Topological Superconductors Relevance Score: 3.5845 Authors: Myungjun Kang, Yogeshwar Prasad, Nikhil Danny Babu, Rasoul Ghadimi, Jae Hoon Kim, Sangmo Cheon Link: http://arxiv.org/abs/2601.04635v1 Summary: This paper theoretically investigates the long-wavelength optical response of topological insulator-superconductor (TI-SC) heterostructures and proposes the interfacial thin-layer conductivity as a layer-selective probe for directly detecting proximity-induced superconductivity. Using a minimal TI-SC model, they demonstrate that the proximity effect at a buried interface can generate a two-dimensional topological superconducting phase supporting Majorana edge modes. The optical conductivity is calculated via the Bogoliubov-de Gennes slab model and the Kubo formula, with a thickness extrapolation protocol introduced to isolate the interface contribution. The results reveal that the interface conductivity exhibits a robust, thickness-independent coherent peak whose energy is determined by the proximity-induced superconducting gap, clearly distinguishing it from the pair-breaking features of the parent superconductor and the response from the gapless Dirac cone on the top surface. Moreover, the low-frequency spectral weight satisfies the quantum metric sum rule, quantitatively linking the optical response to the quantum geometry of the proximitized interface states. This work proposes that terahertz/infrared spectroscopy measurements of interfacial thin-layer conductivity can serve as a noninvasive diagnostic method for probing Majorana-hosting TI-SC interfaces.\n13. Anisotropic magnon transport in an antiferromagnetic trilayer heterostructure: is BiFeO$_3$ an altermagnet? Relevance Score: 3.5648 Authors: Sajid Husain, Maya Ramesh, Qian Song, Sergei Prokhorenko, Shashank Kumar Ojha, Surya Narayan Panda, Xinyan Li, Yousra Nahas, Yogesh Kumar, Pushpendra Gupta, Tenzin Chang, Alan Ji-in Jung, Rogério de Sousa, James G. Analytis, Lane W. Martin, Zhi Yao, Sang-Wook Cheong, Laurent Bellaiche, Manuel Bibes, Darrell G. Schlom, Ramamoorthy Ramesh Link: http://arxiv.org/abs/2601.04578v1 Summary: We report the observation of anisotropic spin wave transport in LaFeO₃/BiFeO₃/LaFeO₃ antiferromagnetic sandwich heterostructures. By utilizing nonlocal spin Hall effects to excite and detect spin waves in the BiFeO₃ layer, we find that the ultrathin BiFeO₃ layer, due to its confined state, serves as an efficient channel for spin wave propagation, which can be electrically modulated via its magnetoelectric coupling. Experimental results reveal pronounced anisotropy in spin transport and a sign reversal of the inverse spin Hall voltage, associated with a nontrivial antiferromagnetic state stabilized in BiFeO₃ by low lattice symmetry and suppression of the spin cycloid. Density functional theory calculations confirm that this state exhibits symmetry-protected spin-split bands, a hallmark of altermagnets. Thus, non-cycloidal BiFeO₃ emerges as a prototype material simultaneously possessing ferroelectricity and altermagnetism, where electric fields can directly manipulate its altermagnetic order, opening new avenues for electrically controlled spin devices based on novel magnetic states.\n14. Towards understanding the defect properties in the multivalent A-site Na$_{0.5}$Bi$_{0.5}$TiO$_3$-based perovskite ceramics Relevance Score: 3.4262 Authors: Pengcheng Hu, Chinmay Chandan Parhi, Jurij Koruza, Andreas Klein Link: http://arxiv.org/abs/2601.04725v1 Summary: This study proposes a defect model incorporating cation vacancies, anion vacancies, and antisite defects to explain the non-stoichiometric behavior of multivalent A-site Na₀.₅Bi₀.₅TiO₃ (NBT)-based perovskite ceramics. By preparing a series of samples with varying A-site non-stoichiometry and A:B ratios, the oxygen partial pressure and temperature-dependent conductivity were measured using DC and AC techniques to distinguish ionic and electronic contributions to conduction. The results show that Na-excess samples (regardless of the A:B ratio) are dominated by ionic conduction with p-type electronic conductivity, achieving a maximum total conductivity of 4×10⁻⁴ S/cm at 450°C; in contrast, Bi-excess samples exhibit stronger insulating behavior with n-type electronic conductivity, with conductivities only on the order of 10⁻⁸ S/cm at 450°C. These conductivity results strongly validate the proposed defect model, which provides a concise description of the defect chemistry of NBT-based ceramics and offers important guidance for tailoring properties through optimized sample processing.\n15. Triple-well ferroelectricity and kagome-like Chern flat band in two-dimensional multiferroic CuVP$_2$Se$_6$ Relevance Score: 3.3561 Authors: Brian Anchico, Jingyi Duan, Haojie Sun, Minjun Wang, Mikhail Talanov, Wei Jiang Link: http://arxiv.org/abs/2601.04846v1 Summary: Through first-principles calculations, this work reveals that monolayer CuVP₂Se₆ simultaneously possesses tunable triple-well ferroelectric phase transitions and spin-polarized Chern flat bands, with the ferroelectric and paraelectric phases exhibiting very close energies that can be reversibly switched by moderate strain or external electric fields, and during the phase transition, flat bands akin to a kagome lattice emerge near the Fermi level, which can be described by a three-orbital tight-binding model on a triangular lattice; moreover, the system displays significant magnetic anisotropy and a Chern insulating state dependent on magnetization orientation—when the magnetization direction is perpendicular to the plane, the Chern number is C=±1, whereas when the magnetic moment turns in-plane, the Chern number becomes trivial—thereby establishing monolayer CuVP₂Se₆ as a promising multiferroic material platform for exploring electrically tunable flat-band correlation effects and topological magnetism.\n16. Surface chiral Abelian topological order on multilayer cluster Mott insulators Relevance Score: 3.2894 Authors: Xu-Ping Yao, Chao-Kai Li, Gang v. Chen Link: http://arxiv.org/abs/2601.05185v1 Summary: Based on the specific surface termination of multilayer-stacked cluster Mott insulators, such as Nb₃Br₈, it is proposed in this paper that chiral Abelian topological order can emerge on the surface of such materials. Through first-principles calculations and slave-rotor mean-field theory, the authors find that when the surface state corresponds to a triangular-lattice Hubbard model, the mean-field solution reveals that under weak to intermediate correlation strength, the four sublattices can independently evolve into either a chiral spin liquid (CSL) or a dimer state, with the 4-CSL phase being energetically dominant and possessing a total Chern number of ±4. This CSL exhibits symmetry-broken chiral edge modes and fractional excitations. Further calculations of the electronic spectral function show that within the characteristic energy window, the spectral weight concentrates at specific momentum points, suggesting detectability via angle-resolved photoemission spectroscopy. This surface topological order naturally explains the field-free diode effect observed in Nb₃Br₈/NbSe₂ Josephson junctions, offering a new perspective for understanding the intersection of correlated electrons and topological phases in cluster Mott insulators.\n17. How semiconducting are ferroelectrics: The fundamental, optical and transport gaps of Na$_{0.5}$Bi$_{0.5}$TiO$_3$-BaTiO$_3$ and NaNbO$_{3}$ Relevance Score: 3.2679 Authors: Pengcheng Hu, Nicole Bein, Chinmay Chandan Parhi, Tadej Rojac, Barbara Malič, Mohammad Amirabbasi, Anton Volodin, Karsten Albe, Jurij Koruza, Andreas Klein Link: http://arxiv.org/abs/2601.04721v1 Summary: There exist three distinct types of band gaps in ferroelectrics: the fundamental band gap, the optical band gap, and the transport band gap, which differ significantly due to the presence of localized polaron charges. In this study, by combining optical measurements, X-ray photoelectron spectroscopy, and temperature- and oxygen-partial-pressure-dependent conductivity measurements, the various band gaps of Na₀.₅Bi₀.₅TiO₃-BaTiO₃ and NaNbO₃ were systematically determined. The results show that the fundamental band gaps (the energy difference between the top of the valence band and the bottom of the conduction band in the ground state) of both materials are approximately 4.5 eV; the optical band gaps (involving polaron electron–hole pair excitation) are 3.25–3.45 eV and 3.5 eV, respectively; while the transport band gaps (determined by polaron trap energy levels) are about 1.4 eV and 3.3 eV, respectively. This discrepancy arises from the localization effect induced by polarons, such that the energy transfers corresponding to optical absorption and electrical transport are much smaller than the ground-state energy difference between band edges. The work emphasizes that distinguishing these band gaps is crucial for understanding the semiconducting behavior of ferroelectrics in energy conversion and catalytic applications, and points out that their band gap characteristics resemble those of organic semiconductors, requiring considerations beyond conventional band theory.\n18. Affordable Five-Orbital Dynamical Mean-Field Theory for Layered Iridates and Rhodates Relevance Score: 3.2373 Authors: Léo Gaspard, Cyril Martins Link: http://arxiv.org/abs/2601.04832v1 Summary: For layered iridates and rhodates, full d-orbital dynamical mean-field theory (DMFT) calculations of spin-orbit-coupled systems have long been hindered by the high computational cost and sign problem of numerical exact solvers, leading previous studies to adopt simplified models that neglect e_g states. This work presents, for the first time, full five-orbital DMFT calculations including spin-orbit coupling for Ba2IrO4 and Ba2RhO4, revealing that correlation effects significantly shift the e_g energy levels primarily through static mean-field corrections rather than dynamical fluctuations. Based on this finding, the authors propose a hybrid dynamical mean-field theory (hDMFT) that treats the e_g orbitals and their coupling to the low-energy t_{2g} manifold at the mean-field level while retaining exact DMFT for the t_{2g} orbitals, thereby drastically reducing computational cost while maintaining near-quantitative accuracy. The establishment of this method enables practical and efficient studies of the full d-manifold in layered iridates and rhodates, making previously infeasible systematic calculations as functions of temperature, doping, and pressure possible.\n19. Giant and Oscillatory Junction Magnetoresistance via RKKY-like Spin Coupling in Spin-Gapless Mn$_2$CoAl/SiO$_2$/p-Si Heterostructures Relevance Score: 3.1851 Authors: Nilay Maji, Subham Mohanty, Pujarani Dehuri Affiliations: National Institute of Technology Rourkela Link: http://arxiv.org/abs/2601.05303v2 Summary: Highly ordered inverse Heusler alloy Mn₂CoAl thin films (XA chemical order ~0.97, Curie temperature ~590 K) were fabricated by magnetron sputtering, and a Mn₂CoAl/native SiO₂/p-Si heterostructure was constructed. Experimental results confirm that Mn₂CoAl exhibits spin-gapless semiconductor characteristics: the resistivity shows weak temperature dependence with a negative temperature coefficient of only about -4.2×10⁻⁹ Ω·m·K⁻¹, and the magnetoresistance exhibits unsaturated linear behavior over a wide range of magnetic fields and temperatures. With only a single ferromagnetic electrode, the heterojunction shows a giant positive junction magnetoresistance (~825% at 10 K and ~134% at room temperature). By systematically varying the SiO₂ tunnel barrier thickness, a repeatable oscillatory sign reversal of the junction magnetoresistance is observed, accompanied by a monotonic decay in amplitude. This behavior reflects the modulation of spin-selective tunneling mediated by interfacial phase-coherent carriers as a function of thickness, which can be phenomenologically described by a function analogous to the RKKY interaction, without invoking conventional metallic exchange coupling. These results demonstrate that the Mn₂CoAl/native SiO₂/p-Si heterostructure is a robust and scalable platform for room-temperature spin-selective transport, with potential applications in semiconductor-compatible spin filters, magnetic field sensors, and reconfigurable spin logic devices.\n20. Single-enantiomer spin polarisers in superconducting junctions Relevance Score: 3.1762 Authors: Lorenz Meyer, Nicolas Néel, Jörg Kröger Link: http://arxiv.org/abs/2601.04772v1 Summary: This study utilizes a superconducting scanning tunneling microscope (STM) tip functionalized with a manganese atomic cluster to generate Yu-Shiba-Rusinov (YSR) resonance states in a junction where a single heptahelicene enantiomer is adsorbed on a Pb(111) surface, serving as a spin-sensitive probe to investigate the chirality-induced spin selectivity (CISS) effect. By avoiding ambiguities inherent in conventional methods such as ferromagnetic electrodes and magnetization reversal, the experiment directly measures the signal intensity of YSR states in the differential conductance spectrum, revealing a significant dependence on the chirality (left- or right-handed) of the enantiomer, with the signal strength changing symmetrically upon reversal of the current direction. This indicates that a single enantiomer acts as a spin polarizer rather than a spin filter, dominating spin-selective electron transport. After excluding contributions from substrate spin polarization, adsorption site differences, electrostatic field effects (such as work function variations or electric dipole modifications), and the spin–orbit coupling of lead, the experimental results provide clear evidence of the CISS effect at the single-molecule level, confirming the spin-polarizing function of enantiomers in a superconducting junction and demonstrating the irrelevance of electrostatic interactions in this model system.\n","permalink":"https://nickelates.uk/en/posts/2026-01-08-arxiv-daily/","summary":"\u003cblockquote\u003e\n\u003cp\u003e\u003cstrong\u003eDaily Overview\u003c/strong\u003e:\nDear readers, welcome to today’s research highlights in the nickel-based superconductivity field. Although none of the papers in today’s list directly focus on nickelate superconductors, several studies are highly relevant to the core issues currently facing nickel-based superconductivity, particularly in terms of electronic structure, superconducting mechanisms, and computational methods. Among them, RIXS studies on the local electronic structure of Ni²⁺ in the pyrochlore antiferromagnet NaCaNi₂F₇ reveal that its octahedral environment is highly robust against A-site disorder, allowing comparisons to the electronic structure stability of the NiO₂ planes in nickel-based superconductors in terms of such local effects. Research on the condensation mechanism of cuprate superconductors reveals bosonic statistical characteristics of strong coupling between pairon excitations and the condensate, and the proposed picture of an energy-dependent gap proportional to the spin-exchange energy may provide insights into understanding similar spin-fluctuation-mediated pairing in nickelates. The discovery of chiral topological order on the surface of the cluster Mott insulator Nb₃Br₈ and its explanation of the zero-field diode effect suggest that surface states in layered correlated systems can give rise to topological superconducting phases under weak correlations, echoing possible interfacial superconducting mechanisms in nickel-based superconductor thin films. Furthermore, the hDMFT method, which achieves full five-orbital DMFT calculations for Ba₂IrO₄ and Ba₂RhO₄, significantly reduces computational costs and provides a feasible pathway for future multi-orbital correlated calculations involving the full d manifold in nickelates.\n\u003cstrong\u003earXiv submission processing window\u003c/strong\u003e: 2026-01-08 03:40 to 2026-01-08 19:07 UTC.\u003c/p\u003e","title":"arXiv Daily: nickelate superconductors 2026-01-08"},{"content":" Daily Overview: In today\u0026rsquo;s paper overview, although no studies directly focusing on nickelates were reported, multiple works are highly relevant to the core issues in nickel-based superconductivity in terms of physical mechanisms and research methods. Among them, [2] demonstrates, through the La₁₋ₓCeₓFeSiH solid solution system, how Kondo entanglement between 3d and 4f correlated electrons finely tunes the competition and coexistence of superconductivity and magnetic order, providing a valuable paradigm for understanding the interaction between nickel 3d and rare-earth 4f electronic states in nickelates. [4] theoretically extends the fluctuation conductivity theory in the ultra-clean limit to multicomponent superconductors, clarifying gauge invariance and critical behavior; its analytical framework for transport signals in multiband systems has direct reference value for nickel-based multiband superconductors. Furthermore, the topological nodal-line superconducting phase realized by coupling in-plane ferromagnetism with conventional s-wave superconductivity in [1], along with the mechanism of band tilting and nodal structure generation, offers new insights for exploring similar topological superconducting states in nickel-based heterostructures. Together, these works enrich the research perspectives on superconducting mechanisms and quantum phase control in correlated electron systems. arXiv submission processing window: 2026-01-07 02:11 to 2026-01-07 19:00 UTC.\n1. In-plane ferromagnetism-driven topological nodal-point superconductivity with tilted Weyl cones Relevance Score: 4.2195 Authors: Maciej Bazarnik, Levente Rózsa, Ioannis Ioannidis, Eric Mascot, Philip Beck, Krisztián Palotás, András Deák, László Szunyogh, Stephan Rachel, Thore Posske, Roland Wiesendanger, Jens Wiebe, Kirsten von Bergmann, Roberto Lo Conte Affiliations: HUN-REN Wigner Research Centre for Physics, University of Groningen, University of Hamburg, Budapest University of Technology and Economics Link: http://arxiv.org/abs/2601.03929v1 Summary: Via low-temperature scanning tunneling spectroscopy experiments, a double-peak low-energy feature in the local density of states near the Fermi level was observed in a heterostructure composed of a single-atom-thick in-plane ferromagnetic cobalt monolayer and a conventional s-wave superconductor niobium (110). Combining first-principles calculations, atomistic spin dynamics simulations, and theoretical analyses based on an effective low-energy model and tight-binding model, this feature is attributed to a topological nodal-line superconducting phase driven by in-plane ferromagnetism, with the band structure exhibiting tilted Weyl cones. Unlike typical topological superconductors that possess a gap, this system realizes a gapless nodal superconducting state due to the combined action of in-plane magnetization and effective time-reversal symmetry, with the nodes deviating from the Fermi level and causing the tilting of the Weyl cones. This study demonstrates that the combination of in-plane ferromagnetism and conventional superconductors is an effective route for designing two-dimensional topological quantum phases.\n2. Superconductivity, Kondo physics and magnetic order: Tuning the groundstate in the La$_{1-x}$Ce$_x$FeSiH solid solution through the interplay between $3d$ and $4f$ correlated electrons Relevance Score: 4.1696 Authors: J. Sourd, B. Vignolle, E. Gaudin, S. Burdin, S. Tencé Link: http://arxiv.org/abs/2601.04097v1 Summary: This study systematically investigates the modulation of the ground state by cerium concentration in La₁₋ₓCeₓFeSiH solid solutions (0 ≤ x ≤ 1). Experimental results show that at low cerium concentrations (x ≤ 0.20), the system exhibits superconductivity originating from Fe 3d electrons, which is suppressed with increasing Ce substitution. In the intermediate concentration range (0.07 ≤ x ≤ 0.50), a single-ion Kondo effect is observed with no magnetic phase transition down to 2 K; specifically, in the region 0.07 ≤ x ≤ 0.20, the single-ion Kondo effect coexists with the superconducting ground state. For x \u0026gt; 0.50, Kondo coherence and heavy fermion liquid behavior emerge, while at high concentrations (x ≥ 0.85), signs of magnetic ordering are detected at low temperatures. By introducing characteristic temperature scales for superconductivity, the Kondo effect, and magnetic ordering, a rich phase diagram is constructed with cerium content as the sole tuning parameter. This phase diagram reveals Kondo entanglement between 3d and 4f correlated electrons and indicates an unusual transition from a superconducting state dominated by 3d electrons to a Kondo coherent state involving both 3d and 4f electrons. These findings provide new insights into the competition and coexistence of complex electronic states via chemical substitution.\n3. High-pressure synthesis of quantum magnet M-YbTaO4 with a stretched diamond lattice Relevance Score: 3.7265 Authors: Nicola D. Kelly, Xuan Liang, Siân E. Dutton, Kazunari Yamaura, Yoshihiro Tsujimoto Link: http://arxiv.org/abs/2601.03834v1 Summary: Monoclinic scheelite-type M-YbTaO₄, featuring spin-1/2 Yb³⁺ ions arranged on a geometrically frustrated \u0026ldquo;stretched diamond\u0026rdquo; lattice, was synthesized via high-pressure technology at 6 GPa and 1800 °C. Magnetic susceptibility and specific heat measurements reveal no long-range magnetic order above 1.8 K, with behavior consistent with a J_eff = 1/2 Kramers doublet that splits under an applied magnetic field. High-pressure synthesis also stabilizes the M-phase across the entire YbNb_xTa₁-xO₄ solid solution (0 \u0026lt; x \u0026lt; 1), whereas under ambient pressure, Ta-rich compositions favor the competing M′ phase. Some high-pressure-synthesized Nb-Ta mixed samples exhibit color changes, indicating oxygen deficiencies, but become white upon annealing. Varying the Nb/Ta ratio or annealing conditions has little effect on the bulk magnetic properties. This study highlights the role of high-pressure synthesis in preparing novel quantum magnets and confirms M-YbTaO₄ as a promising spin liquid candidate with strong geometric frustration.\n4. Fluctuation conductivity in ultraclean multicomponent superconductors Relevance Score: 3.5443 Authors: Sondre Duna Lundemo, Asle Sudbø Link: http://arxiv.org/abs/2601.04308v2 Summary: This paper employs functional integral techniques to derive the Gaussian fluctuation action in the ultra-clean limit for extreme type-II multicomponent superconductors with multi-band Fermi surfaces, thereby obtaining the gauge-invariant electromagnetic linear response kernel and subsequently calculating the optical conductivity tensor. The study indicates that in a disorder-free, translation-invariant system, the necessary condition for a nonzero dissipative part of the longitudinal conductivity arises indirectly from the multicomponent nature of both the impending superconducting order and the parent metallic state. Under these conditions, the enhancement of DC conductivity by fluctuations near the critical point exhibits the same critical behavior as in the diffusive limit. This work extends the theory of ultra-clean fluctuation conductivity to the multicomponent case, verifies gauge invariance, and reveals nontrivial transport signatures due to the multicomponent nature.\n5. Electronic Structure of UGe$_{2\\pm x}$ Thin Films from Photoelectron Spectroscopy Relevance Score: 3.3839 Authors: Sonu George Alex, Oleksandr Romanyuk, Ivan Zorilo, Alexander Andreev, Frank Huber, Thomas Gouder, Petr Malinsky, Maliha Siddiqui, Alexander B. Shick, Evgenia A. Tereshina-Chitrova Link: http://arxiv.org/abs/2601.03902v2 Summary: UGe₂±ₓ thin films (0≤x≤1) with varying stoichiometry were fabricated by triode sputtering, and their electronic structures were investigated using in-situ X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS). The XPS and UPS results reveal that all films exhibit a metallic valence band dominated by U-5f states near the Fermi level, along with broad incoherent features at higher binding energies, while the spectral line shapes remain qualitatively unchanged across the entire compositional range. The experimental spectra of UGe₂ films are well reproduced by calculations using density functional theory combined with exact diagonalization of the multiconfigurational U-5f shell (DFT+U(ED)). This study demonstrates that the U-Ge electronic framework in UGe₂ thin films is remarkably robust against moderate stoichiometric deviations, providing a reliable electronic structure benchmark for future investigations of interface- and heterostructure-driven electronic phenomena in uranium-based systems.\n6. Layer Hall effect induced by altermagnetism Relevance Score: 3.2600 Authors: Fang Qin, Rui Chen Link: http://arxiv.org/abs/2601.03937v3 Summary: This study proposes a scheme for realizing the layer Hall effect in a ferromagnetic topological insulator Bi₂Se₃ by proximity coupling with a d-wave altermagnet. By applying an altermagnet and an in-plane magnetic field near one surface, the energy gap of the corresponding Dirac cone can be opened, leading to an altermagnet-induced half-quantized Hall effect. When the top and bottom surfaces are respectively coupled to altermagnets with antiparallel Néel vectors, the Hall contributions from the two surfaces cancel each other, resulting in a layer Hall effect with zero net Hall conductance; if the Néel vectors are parallel, a fully quantized anomalous Hall effect emerges. Further analysis shows that the Hall conductance varies with the direction of the in-plane magnetic field, and a perpendicular electric field can render the layer Hall effect observable. This work provides a new route to engineering altermagnet-induced topological phases in ferromagnetic topological insulators.\n7. Structural heterogeneity-induced enhancement of transverse magneto-thermoelectric conversion revealed by thermoelectric imaging in functionally graded materials Relevance Score: 3.2504 Authors: Sang J. Park, Ravi Gautam, Takashi Yagi, Rajkumar Modak, Hossein Sepehri-Amin, Ken-ichi Uchida Affiliations: National Institute for Materials Science, National Institute of Advanced Industrial Science and Technology, The University of Tokyo Link: http://arxiv.org/abs/2601.03581v1 Summary: A functional gradient material (FGM) with continuous structural heterogeneity was fabricated by annealing amorphous metals under a spatial temperature gradient, and lock-in thermography (LIT) was employed to achieve spatial mapping of transverse thermoelectric conversion with high spatial and temperature resolution. The study revealed that the anomalous Ettingshausen effect (transverse charge-heat conversion) exhibits a pronounced non-monotonic response, with its maximum occurring in the atomic heterogeneity region (well before the crystallization stage), an enhancement that is not captured by conventional structural characterization or longitudinal transport measurements. Combined scanning transmission electron microscopy and atom probe tomography confirmed that this enhancement originates from microstructural heterogeneity induced by Fe-based crystalline alloys and Cu nanoclusters embedded in the amorphous matrix. This work establishes temperature-gradient-annealed FGM combined with LIT as a powerful approach for uncovering structural-heterogeneity-driven transverse electronic transport and designing high-performance flexible materials.\n8. Anisotropic second-harmonic generation in superconducting nanostructures Relevance Score: 3.2240 Authors: Sara Memarzadeh, Maciej Krawczyk, Armen Gulian, Jaroslaw W. Klos Link: http://arxiv.org/abs/2601.03989v1 Summary: By numerically solving the time-dependent Ginzburg-Landau equation, this study analyzes the nonlinear electrodynamic behavior of superconducting nanocubes under non-collinear excitation of static and microwave magnetic fields. The results show that when the microwave field is applied perpendicular to the static field, the magnetization component parallel to the static field generates a significant second harmonic response, which is greatly enhanced when the static field approaches the successive vortex nucleation threshold and the Meissner current tends to saturate. The origin of the second harmonic is attributed to the combined effect of Meissner current saturation and the nonlinear oscillation of normal-phase indentations. Its signal is spatially separated from the first harmonic component and not masked by it, exhibiting anisotropic characteristics. This finding reveals the influence of device geometry on nonlinear high-frequency response, providing a design basis for controllable high-frequency nonlinear superconducting devices.\n9. Wigner solid or Anderson solid \u0026ndash; 2D electrons in strong disorder Relevance Score: 3.1520 Authors: Aryaman Babbar, Zi-Jian Li, Sankar Das Sarma Link: http://arxiv.org/abs/2601.03521v1 Summary: This paper critically analyzes recent scanning tunneling microscopy (STM) and transport experiments on two-dimensional electron gases with random quenched impurities, demonstrating that the reported low-density \u0026ldquo;solid\u0026rdquo; phase is not an interaction-driven Wigner crystal but an Anderson solid formed by random impurity localization. Through transport calculations based on the Ioffe-Regel-Mott (IRM) criterion using experimentally measured mobilities and impurity densities, as well as small-system exact diagonalization (ED) phase diagram simulations, the authors show that the observed solid-liquid transition density closely matches the IRM strong localization density, far exceeding the theoretically predicted disorder-free Wigner crystallization density. Under strong disorder, the solid phase exhibits an extremely short spatial correlation length (much less than one lattice constant), displays amorphous characteristics, and is adiabatically connected to the infinite-disorder Anderson fixed point rather than the zero-disorder Wigner crystal fixed point. The ED phase diagram further reveals the competition between interaction and disorder: a Wigner phase in the weak-disorder strong-interaction regime, an Anderson localized phase in the strong-disorder weak-interaction regime, and a disorder-enhanced liquid or reentrant solid region between them. The conclusion states that the \u0026ldquo;solid\u0026rdquo; observed in current STM experiments is primarily a disorder-dominated Anderson solid, whose transport behavior can be fully explained by the IRM criterion rather than being evidence of Wigner crystallization; the experimental data are consistent with the theoretical phase diagram, indicating that the system has four distinct fixed points (Fermi liquid, Wigner crystal, Anderson solid, and strongly coupled electron glass), but the predominant phase at zero field is the Anderson solid.\n10. Magnetoluminescence of ZnMnSe/BeMnTe heterostructures with type-II band alignment at millikelvin temperatures Relevance Score: 3.1013 Authors: Dennis Kudlacik, Linda Kersting, Nataliia E. Kopteva, Mladen Kotur, Dmitri R. Yakovlev, Manfred Bayer Link: http://arxiv.org/abs/2601.04046v1 Summary: This study systematically investigates a type-II band-aligned Zn₀.₉₉Mn₀.₀₁Se/Be₀.₉₃Mn₀.₀₇Te diluted magnetic semiconductor heterostructure using magneto-optical spectroscopy at ultralow temperatures down to 16 mK. By measuring the giant Zeeman splitting of direct excitons in an external magnetic field, the temperature of the Mn spin system was evaluated, reaching a minimum of 270 mK under the lowest excitation power of 2.5 nW. Meanwhile, the circular polarization degrees of direct and indirect optical transitions were demonstrated to be sensitive indicators for monitoring laser-induced heating of the Mn spin system. The heteromagnetic structure design with different Mn concentrations (1% Mn in ZnMnSe layer and 7% Mn in BeMnTe layer) effectively reduced the heating effect of photogenerated carriers on the Mn spin system. A key finding is the observation of a spin glass phase formation in the Be₀.₉₃Mn₀.₀₇Te layer at a critical temperature of 400 mK. This work provides important experimental evidence for the thermodynamic behavior and spin dynamics of the Mn spin system in diluted magnetic semiconductors at ultralow temperatures.\n11. muT2-NMR: Micro-Scale Correlation Relaxometry for in-situ High-Pressure Nuclear Magnetic Resonance Relevance Score: 3.0378 Authors: Thomas Meier, Meng Yang, Yishan Zhou, Yunhua Fu, Rui Zhang, Ziliang Wang, Tianyao Zheng, Rajesh Jana, Takeshi Nakagawa Link: http://arxiv.org/abs/2601.03545v1 Summary: In recent years, frequency-domain high-pressure nuclear magnetic resonance (NMR) in diamond anvil cells (DAC) has been used to study condensed matter under extreme compression, but spin interactions and sample heterogeneity often lead to severe spectral overlap, making it difficult to distinguish chemically similar subspecies. This paper proposes a time-domain relaxation measurement framework specifically designed for DAC experiments—muT2-NMR. This method encodes the longitudinal relaxation time (T1) of the sample via saturation recovery, detects the transverse relaxation time (T2) using the Carr-Purcell-Meiboom-Gill (CPMG) sequence, and recovers the corresponding relaxation time distribution from sub-nanoliter volume samples through two-dimensional inverse Laplace transformation. Experimental validation was performed on three hydrogen-containing molecular solids—formamide, melamine, and trifluoroacetamide—at pressures up to 72 GPa. The results demonstrate that even when frequency-domain spectral lines severely overlap, muT2-NMR can clearly distinguish different molecular subunits or dynamic regions in the relaxation domain, and the method maintains robust relaxation features even with significantly reduced scan numbers and acquisition times. This study establishes relaxation correlation spectroscopy as a practical tool, opening new avenues for high-resolution detection of dynamics and microscopic heterogeneity in molecular solids under high pressure.\n","permalink":"https://nickelates.uk/en/posts/2026-01-07-arxiv-daily/","summary":"\u003cblockquote\u003e\n\u003cp\u003e\u003cstrong\u003eDaily Overview\u003c/strong\u003e:\nIn today\u0026rsquo;s paper overview, although no studies directly focusing on nickelates were reported, multiple works are highly relevant to the core issues in nickel-based superconductivity in terms of physical mechanisms and research methods. Among them, [2] demonstrates, through the La₁₋ₓCeₓFeSiH solid solution system, how Kondo entanglement between 3d and 4f correlated electrons finely tunes the competition and coexistence of superconductivity and magnetic order, providing a valuable paradigm for understanding the interaction between nickel 3d and rare-earth 4f electronic states in nickelates. [4] theoretically extends the fluctuation conductivity theory in the ultra-clean limit to multicomponent superconductors, clarifying gauge invariance and critical behavior; its analytical framework for transport signals in multiband systems has direct reference value for nickel-based multiband superconductors. Furthermore, the topological nodal-line superconducting phase realized by coupling in-plane ferromagnetism with conventional s-wave superconductivity in [1], along with the mechanism of band tilting and nodal structure generation, offers new insights for exploring similar topological superconducting states in nickel-based heterostructures. Together, these works enrich the research perspectives on superconducting mechanisms and quantum phase control in correlated electron systems.\n\u003cstrong\u003earXiv submission processing window\u003c/strong\u003e: 2026-01-07 02:11 to 2026-01-07 19:00 UTC.\u003c/p\u003e","title":"arXiv Daily: nickelate superconductors 2026-01-07"},{"content":" Daily Overview: Based on the list of papers you provided, today\u0026rsquo;s daily overview does not include studies directly focused on the field of nickelate superconductors. However, several works discuss physical mechanisms or research methods highly relevant to the core issues currently concerning nickelate superconductivity, making them worthy of attention. The following is the overall introduction prepared for today\u0026rsquo;s post: — Dear readers, welcome to today\u0026rsquo;s daily overview of the field of nickelate superconductors. Although the highlighted works today do not directly study nickelates, they focus on key topics such as superconducting pairing mechanisms, electron-phonon coupling modulation, nematic orbital anisotropy, and the competition between charge density waves and superconductivity, providing important references for understanding nickelate superconductivity. For example, [1] proposes interlayer charge-transfer ferroelectric fluctuations as a pairing mechanism for van der Waals superconductors; [2] significantly enhances the superconducting transition temperature of A15-type LaH5.75 via Ba doping; [3] real-space images orbital nematicity in iron-based superconductors using laser PEEM; [5] reveals the competition between CDW and superconductivity in Janus MoXH monolayers; [8] explores electron pairing mechanisms without phonon mediation based on a two-band model. These findings expand the understanding of unconventional superconductivity and complement the current concerns in the nickelate superconductor field regarding electronic structure, pairing mechanisms, and competing orders. arXiv submission processing window: 2026-01-05 21:10 to 2026-01-06 19:28 UTC.\n1. Interlayer Charge-Transfer Ferroelectric Fluctuations as a Pairing Mechanism in van der Waals Superconductors Relevance Score: 4.3186 Authors: Ankan Biswas, Jagannath Sutradhar, Sudip Kumar Saha, Avraham Klein, Jonathan Ruhman Link: http://arxiv.org/abs/2601.03352v1 Summary: This paper proposes interlayer charge transfer ferroelectric fluctuations as a pairing mechanism for the microscopic origin of unconventional superconductivity in van der Waals superconductors. By constructing a theoretical model of two coupled layers with interlayer breathing and shear phonon modes, we find that weak interlayer bonding can actually generate significant pairing interactions through charge transfer. The theory indicates that proximity to a ferroelectric or antiferroelectric quantum critical point can provide a strong coupling pairing channel; in a two-dimensional model that includes SU(2) symmetry and in-plane isotropy, accidental degeneracy of interlayer triplets emerges, which can be realized even when the in-plane gap is s-wave. Furthermore, interlayer Josephson coupling (arising from static magnetism or paramagnetic correlations) can stabilize an s+is-type time-reversal symmetry breaking superconducting state, which couples to magnetization when at least two mirror symmetries are absent. These results are directly applicable to candidate chiral van der Waals superconductors such as 4Hb-TaS₂ and sliding ferroelectric metals like bilayer MoTe₂, indicating that ferroelectric fluctuations represent an important route to unconventional pairing in van der Waals systems and motivating experimental searches for chiral multicomponent superconducting states.\n2. Enhanced Electron-Phonon Coupling and Superconductivity in Ba-Alloyed A15 LaH5.75 Relevance Score: 4.1727 Authors: Jakkapat Seeyangnok, Udomsilp Pinsook, Graeme J Ackland Link: http://arxiv.org/abs/2601.02966v1 Summary: This study systematically investigates the effects of Ba doping on the structural stability, lattice dynamics, and superconductivity of A15-type LaH5.75 using first-principles calculations. The results show that after partial substitution of La with Ba, La0.75Ba0.25H5.75 remains dynamically stable in the pressure range of 120–200 GPa, whereas pure LaH5.75 exhibits phonon imaginary frequencies under the PBE functional, indicating instability. Ba2+ substitution for La3+ reduces the electron count, disrupts the formation of H2 units, and shifts the Fermi level, thereby significantly enhancing electron-phonon coupling. The calculated superconducting transition temperature is approximately 183 K, nearly twice that of pure LaH5.75 under the same pressure. In contrast, Hf substitution does not yield a stable compound. This work broadens the alloy design principles for A15-type hydride superconductors, demonstrating that doping can effectively tune the Fermi level position and electron-phonon coupling strength, providing specific guidance for the experimental realization of novel high-temperature superconducting phases.\n3. Energy-Resolved Real-Space Imaging of Orbital Nematicity in an Fe-Based Superconductor Relevance Score: 4.1382 Authors: Asato Onishi, Zifan Xu, Cédric Bareille, Yoichi Kageyama, Shigeyuki Ishida, Hiroshi Eisaki, Kota Ishihara, Kenichiro Hashimoto, Toshiyuki Taniuchi, Takasada Shibauchi Link: http://arxiv.org/abs/2601.02707v1 Summary: Using 5.82 eV laser-excited photoemission electron microscopy (laser-PEEM) combined with an energy-selecting slit, the linear dichroism (LD) contrast in the nematic domains of Ba₁₋ₓNaₓFe₂As₂ (x≈0.08) was imaged in real space. A sign reversal of the LD contrast was observed at approximately 0.4 eV below the Fermi level, directly revealing a reversal of the electronic orbital anisotropy within the same domain. This behavior originates from the energy-dependent redistribution of spectral weight between the d_xz and d_yz states: near the Fermi level, the d_yz orbital dominates, while at deeper binding energies (below ~0.4 eV), the d_xz orbital prevails. These results provide the first observation of an energy-dependent sign change of orbital anisotropy in coexisting nematic domains without applied strain, indicating that the transfer of spectral weight from coherent to incoherent bands is anisotropic, thereby highlighting the crucial role of orbital-selective coherence in the nematic phase of iron-based superconductors. Temperature-dependent analysis reveals that this sign reversal occurs below the nematic transition temperature, and the LD signal tends to follow the temperature dependence of the magnetic order parameter, further supporting an energy-dependent spectral weight transfer mechanism. This study provides real-space evidence for understanding orbital selectivity and superconducting pairing mechanisms in the nematic phase.\n4. Electronic band structure reconstruction in Ni$_{x}$ZrTe$_{2}$ Relevance Score: 4.0282 Authors: Pedro H. A. Moya, Marli R. Cantarino, Lucas E. Correa, Leandro R. de Faria, Rodrigo M. C. Huamani, Wendell S. Silva, Claude Monney, Antonio J. S. Machado, Fernando A. Garcia Link: http://arxiv.org/abs/2601.02647v1 Summary: This study systematically investigates the electronic structures of ZrTe₂ and its nickel-intercalated compound NiₓZrTe₂ (x≈0.05) using angle-resolved photoemission spectroscopy (ARPES). In NiₓZrTe₂, two flat bands originating from Ni 3d orbitals are identified at binding energies of approximately -0.7 eV and -1.2 eV, and these bands remain stable across the entire temperature range. More critically, at low temperatures, the electronic structure of NiₓZrTe₂ undergoes a reconstruction with a halved periodicity along the k_z direction, exhibiting a commensurate band-folding feature with a wave vector q=(0,0,π). Combined with previous macroscopic measurements of heat capacity and resistivity, this electronic structure reconstruction is closely associated with a structural instability induced by Ni intercalation at around 287 K, providing direct spectroscopic evidence for the correlation between intercalation-induced structural phase transitions and electronic band reconstruction.\n5. Charge Density Wave Order and Superconductivity in Janus MoXH Monolayers Relevance Score: 4.0276 Authors: Jakkapat Seeyangnok, Udomsilp Pinsook, Graeme J Ackland Link: http://arxiv.org/abs/2601.02959v1 Summary: Through first-principles calculations, phonon analysis, electronic susceptibility, and molecular dynamics simulations, this paper systematically investigates the origin, stability, and correlation with superconductivity of charge density wave (CDW) order in Janus MoXH (X=S, Se) monolayers. The study reveals that these materials exhibit an intrinsic commensurate CDW ground state in both the 2H and 1H phases, driven by soft phonon modes at the M point of the Brillouin zone; electronic susceptibility analysis demonstrates that this instability does not arise from Fermi surface nesting but is dominated by strong momentum-dependent electron-phonon coupling. The CDW structural reconstruction completely eliminates the imaginary phonon modes in the high-symmetry metallic phase and reduces the total energy of the system. The interplay between CDW and superconductivity is material-dependent: in 1T-MoSH, CDW formation enhances low-frequency phonon contributions and electron-phonon coupling, thereby increasing the superconducting transition temperature; whereas in 1T-MoSeH and 2H-MoSeH, the CDW phase suppresses electron-phonon coupling and weakens superconductivity. Additionally, thermal fluctuations, compressive strain, and carrier doping can selectively suppress the CDW order and restore the superconducting phase. These results uncover Janus MoXH monolayers as tunable two-dimensional platforms for exploring lattice-driven charge order and its competition with superconductivity.\n6. Altermagnetic superconducting diode effect from non-collinear compensated magnetism in Mn$_3$Pt Relevance Score: 3.9064 Authors: Constantin Schrade, Sujit Manna, Mathias S. Scheurer Link: http://arxiv.org/abs/2601.03348v1 Summary: This study develops a theoretical framework to explain the experimentally observed superconducting diode effect in heterostructures composed of Mn₃Pt and a superconductor. Through symmetry analysis and calculations based on a breathing kagome lattice model, the research reveals how the non-collinear altermagnetic spin structure in Mn₃Pt, despite the absence of net magnetization and in the presence of spin-orbit coupling, induces spin splitting of the electronic bands; when combined with interface proximity coupling, this splitting ultimately gives rise to the superconducting diode effect. Furthermore, the study demonstrates that the angular dependence of the critical current can serve as an effective probe of the magnetic order type, providing an experimental means to distinguish different magnetic configurations. This work deepens the understanding of novel superconducting phenomena in hybrid systems of altermagnets and superconductors, and facilitates the discovery of additional candidate materials for constructing altermagnet-superconductor hybrid devices.\n7. Altermagnetic Superconducting Diode Effect in Mn$_{3}$Pt/Nb Heterostructures Relevance Score: 3.8340 Authors: Saurav Sachin, Mathias S. Scheurer, Constantin Schrade, Sujit Manna Link: http://arxiv.org/abs/2601.03366v1 Summary: By constructing heterojunctions of Nb thin films with noncollinear altermagnets Mn₃Pt (T₁ and T₂ phases), this study experimentally confirms the superconducting diode effect under zero magnetic field. Unlike conventional mechanisms relying on spin-orbit coupling or ferromagnetic net magnetization, this effect originates from the spin splitting of electronic bands by the altermagnetic order without generating stray fields. In Mn₃Pt/Nb heterojunctions, although the T₂ phase exhibits fully compensated magnetic order and the T₁ phase is nearly compensated, both superconducting states display significant nonreciprocal critical currents, with diode efficiency reaching up to 50% and high sensitivity to the magnetic order form. By varying the stoichiometry of Mn₃Pt, the T₁ and T₂ phases can be tuned; their distinct symmetries lead to differences in anomalous Hall effect and superconducting diode behavior: the T₁ phase generates finite Berry curvature due to chirality, whereas the T₂ phase, constrained by mirror symmetry, exhibits no net Berry curvature. Transport measurements reveal a notable suppression of the superconducting state by the altermagnetic order, with the Nb superconducting transition temperature decreasing from 8.3 K to 7.6 K. The current-voltage characteristics show pronounced diode efficiency at zero field, which first increases and then decreases with rising temperature. This work establishes a new material paradigm for magnetization-free superconducting diodes, providing a platform for dissipationless spintronics and symmetry detection, and advancing the experimental exploration of noncollinear altermagnetic superconductors.\n8. Electron pairing in model with two overlapping bands Relevance Score: 3.6943 Authors: Igor N. Karnaukhov Link: http://arxiv.org/abs/2601.02973v1 Summary: This study investigates the mechanism of electron pairing in a two-band Hubbard model, where electrons from different bands interact via local single-particle and two-particle hybridization. Using the Schrieffer-Wolff transformation to construct an effective theory, it is found that two-particle hybridization can induce an effective attraction among conduction-band electrons, thereby counteracting the direct Hubbard repulsion and leading to η-pairing. The pairing energy is determined by the interaction constant and is independent of the band width. This mechanism differs from conventional Cooper pairing, as it does not rely on phonon mediation but instead depends on indirect electron-electron interactions, offering an explanation for the high-temperature superconductivity observed in hydrogen-rich materials under high pressure, such as LaH₁₀. The study shows that when one band lies above the Fermi level, an effective attraction arises among conduction-band electrons, forming electron pairs with nonzero momentum, which provides a criterion for experimental verification of unconventional superconducting pairing mechanisms. This work presents a simple electron-electron pairing framework for understanding the nature of high-temperature superconductivity.\n9. Inverse magnetic melting effect in vdW-like Kondo lattice CeSn$_{0.75}$Sb$_2$ Relevance Score: 3.6426 Authors: Hai Zeng, Yiwei Chen, Zhuo Wang, Shuo Zou, Kangjian Luo, Yang Yuan, Meng Zhang, Yongkang Luo Link: http://arxiv.org/abs/2601.02820v2 Summary: This paper reports the growth and physical properties of quasi-two-dimensional van der Waals Kondo lattice single crystals of CeSn₀.₇₅Sb₂. Through transport, magnetic, and thermodynamic measurements, the material is found to exhibit fragile antiferromagnetic order and a cluster glass ground state, both of which are highly sensitive to applied magnetic fields. Under a low in-plane magnetic field at low temperatures, the antiferromagnetic phase transforms directly or via an intermediate cluster glass phase into a polarized paramagnetic phase, constituting an inverse magnetic melting effect that restores the broken translational/rotational symmetry. This work provides a rare example of the inverse magnetic melting effect in van der Waals heavy fermion materials and enriches the physical implications of the conventional Kondo lattice model.\n10. Observation of spin-valley locked nodal lines in a quasi-2D altermagnet Relevance Score: 3.4240 Authors: Quanxin Hu, Xingkai Cheng, Qingchen Duan, Yudong Hu, Bei Jiang, Yusen Xiao, Yaqi Li, Mojun Pan, Liwei Deng, Changchao Liu, Guanghan Cao, Zhengtai Liu, Mao Ye, Shan Qiao, Zhanfeng Liu, Zhe Sun, Anyuan Gao, Yaobo Huang, Ruidan Zhong, Junwei Liu, Baiqing Lv, Hong Ding Affiliations: Hefei National Laboratory, Hong Kong University of Science and Technology, Shanghai Jiao Tong University, New Cornerstone Science Laboratory, Chinese Academy of Sciences, University of Science and Technology of China, Zhejiang Institute of Photoelectronics, Collaborative Innovation Center of Advanced Microstructures, Zhejiang University, Nanjing University Link: http://arxiv.org/abs/2601.02883v1 Summary: Using high-resolution spin- and angle-resolved photoemission spectroscopy combined with first-principles calculations, researchers have observed a novel spin-valley-locked nodal line phase in the quasi-two-dimensional layered altermagnet Rb-intercalated V₂Te₂O. In this material, both spin-degenerate nodal lines and spin nodal lines coexist near the Fermi level: the spin-degenerate nodal lines are formed by the crossing of bands with opposite spins, while the spin nodal lines exhibit uniform spin polarization within the same valley but opposite spin polarization between symmetrically paired valleys—a feature termed spin-valley-locked nodal lines, a unique topological phase exclusive to altermagnets. By employing a side-cutting technique to directly measure out-of-plane band dispersion, the two-dimensional nature of these nodal lines was confirmed. This discovery not only reveals unexplored topological phases in altermagnets where valley-locked spins serve as an additional quantum degree of freedom, but also establishes the potential of RbV₂Te₂O for applications in spintronics, valleytronics, and moiré-engineered quantum devices.\n11. Influence of controlled disorder on the dipolar spin ice state of Ho-based pyrochlores Relevance Score: 3.4117 Authors: A. A. Aczel, B. R. Ortiz, Y. Luo, G. Pokharel, P. M. Sarte, C. dela Cruz, J. Liu, G. Sala, S. D. Wilson, B. A. Frandsen, J. A. M. Paddison Link: http://arxiv.org/abs/2601.02555v2 Summary: This study investigates the stability of the dipolar spin ice state in Ho-based pyrochlores Ho₂GaSbO₇ and Ho₂ScSbO₇ by introducing controlled chemical disorder through non-magnetic B-site cation mixing. Neutron diffraction and pair distribution function analyses reveal that Ho₂GaSbO₇ exhibits only charge disorder, whereas Ho₂ScSbO₇ displays both charge and size disorder due to the significant ionic radius difference between Sc³⁺ and Sb⁵⁺, manifested as a shortened cation ordering correlation length and enhanced local structural distortion. Nevertheless, bulk thermodynamic measurements and magnetic diffuse scattering demonstrate that both materials retain the characteristic signatures of the dipolar spin ice state, including Ising moments constrained by ice rules and magnetic monopole excitations. Low-energy inelastic neutron scattering further uncovers broadened magnetic excitations within the spin ice state, a feature absent in disorder-free Ho pyrochlores, indicating that disorder induces splitting of the non-Kramers doublet, equivalent to a random transverse field effect. Overall, the results suggest that controlled disorder introduces tunable transverse-field-driven quantum fluctuations in Ho-based pyrochlores, yet the dipolar spin ice state exhibits remarkable robustness against such disorder.\n12. Strain Engineering of Intrinsic Anomalous Hall and Nernst Effects in Altermagnetic MnTe at Realistic Doping Levels Relevance Score: 3.3265 Authors: Weiwei Chen, Ziyu Zhou, Jie Meng, Weiyi Wang, Ye Yang, Zhongjun Li Link: http://arxiv.org/abs/2601.02913v1 Summary: This work, employing the k·p effective model, elucidates the microscopic mechanism underlying the suppression of the anomalous Hall effect in hexagonal MnTe—a prototypical g-wave altermagnet—at experimentally relevant hole doping concentrations (∼10¹⁹ cm⁻³): near the valence band top, the antisymmetric Berry curvature contribution cancels out in momentum space due to the rotational symmetry of the Fermi surface. The study proposes that introducing volume-conserving biaxial strain can break this crystal symmetry, eliminating the Berry curvature cancellation and thereby boosting the anomalous Hall conductivity by several orders of magnitude, while simultaneously significantly enhancing the anomalous Nernst effect through Fermi surface distortion. Spin texture analysis confirms that the strain-induced transport enhancement does not generate a net magnetization, ensuring that the signal originates from the intrinsic topology of the altermagnet rather than from piezomagnetic effects. This strain engineering strategy offers a viable pathway for experimentally detecting and tuning the anomalous Hall and Nernst effects in systems with zero net magnetization.\n13. Spectroscopic Demarcation of Emergent Photons and Spinons in a Dipolar-Octupolar Quantum Spin Liquid Relevance Score: 3.2661 Authors: Bin Gao, Zhengbang Zhou, Tingjun Zhang, Andrey Podlesnyak, Sang-Wook Cheong, Yong Baek Kim, Pengcheng Dai Link: http://arxiv.org/abs/2601.03202v1 Summary: In the dipole-octupole (DO) pyrochlore Ce₂Zr₂O₇, the theoretically predicted π-flux quantum spin ice (QSI) state simultaneously hosts gapless emergent photons and a spinon continuum, but these modes are difficult to resolve at zero field due to spectral overlap and near-zero-energy nonmagnetic scattering. In this study, neutron scattering experiments were performed under a magnetic field applied along the [1,1,1] direction, employing a same-temperature high-field background subtraction scheme instead of the conventional high-temperature subtraction method. By exploiting the selective coupling of the magnetic field to the dipole degrees of freedom, the photon mode was isolated. The experiments revealed that a weak field of about 0.15 T suppresses the low-energy photon weight, while the high-energy spinon continuum, though somewhat hardened, remains robust. Combined with gauge mean-field theory and exact diagonalization calculations, these results provide spectroscopic evidence for the π-flux QSI state and establish an effective field-tuned protocol for studying DO-QSL materials.\n14. Anomalous Hall transport in Mn$_{3}$Sn$_{0.5}$X$_{0.5}$C (X = Ge and Zn) Relevance Score: 3.1117 Authors: Sunil Gangwar, C. S. Yadav Link: http://arxiv.org/abs/2601.02833v1 Summary: This study investigates the anomalous Hall transport properties in Ge- and Zn-doped Mn₃SnC antiperovskite compounds, specifically Mn₃Sn₀.₅Ge₀.₅C (MSGC) and Mn₃Sn₀.₅Zn₀.₅C (MSZC). MSGC undergoes a paramagnetic to coexisting antiferromagnetic/ferromagnetic transition at approximately 300 K, while MSZC exhibits a paramagnetic to ferromagnetic transition at 240 K followed by a ferromagnetic to ferrimagnetic transition at 170 K. Analysis of longitudinal resistivity indicates that electron-phonon and electron-magnon scattering dominate the transport behavior. By measuring the Hall resistivity and separating the anomalous and normal Hall components, it is found that the anomalous Hall effect arises from the combined contributions of skew scattering and the intrinsic Berry curvature mechanism, with electron-phonon and electron-magnon scattering playing significant roles in skew scattering at high temperatures. The Tian-Ye-Jin scaling model further confirms the contributions of defect, phonon, and magnon scattering to the anomalous Hall resistivity. Compared to undoped Mn₃SnC, Ge and Zn doping significantly enhance the anomalous Hall conductivity, reaching 26 Ω⁻¹cm⁻¹ for MSGC and 200 Ω⁻¹cm⁻¹ for MSZC at 1.8 K, with anomalous Hall angles of 1.5% and 8%, respectively. The study demonstrates that doping effectively improves anomalous Hall transport performance by altering the magnetic structure and enhancing scattering mechanisms.\n15. $\\mathbb{Z}_L$ symmetry breaking in SU(N) Fermi-Hubbard dots at zero and finite temperature Relevance Score: 3.0764 Authors: Loïc Herviou, Elodie Campan, Pierre Nataf Link: http://arxiv.org/abs/2601.02590v1 Summary: This paper investigates the SU(N) Fermi-Hubbard model on a chain, demonstrating that attractive interaction U leads to Z_L symmetry breaking in the limit of large color number N and particle number with small lattice size L. By combining exact diagonalization with full SU(N) symmetry, a generalized L-level Holstein-Primakoff transformation, the Hartree-Fock method, and a large-N saddle-point approximation of the partition function, the authors extend previous results for two lattice sites to L ≥ 3 sites and finite temperatures. At zero temperature, the ground state exhibits L-fold degeneracy when U \u0026lt; U_c ≈ -1/N; at finite temperature, the critical temperature T_c is proportional to N and the magnitude of U (T_c ∝ -NU), indicating that this phase transition is particularly relevant for large-N fermionic systems. This study reveals the competition between quantum and thermal fluctuations in finite-size systems and provides a theoretical framework for understanding symmetry-breaking behavior in strongly correlated systems at both zero and finite temperatures.\n16. ESR Investigations of the Magnetic Anisotropy in $κ$-(BETS)$_2$Mn[N(CN)$_{2}$]$_3$ Relevance Score: 3.0481 Authors: Zhijie Huang, Marvin Schmidt, Savita Priya, Mark Kartsovnik, Natalia Kushch, Martin Dressel Link: http://arxiv.org/abs/2601.02936v1 Summary: Using X-band electron spin resonance spectroscopy, the magnetic properties of the two-dimensional molecular conductor κ-(BETS)₂Mn[N(CN)₂]₃ were systematically investigated, with a focus on the temperature and angular dependences of the spin susceptibility, g-factor, and linewidth. It was found that, due to the π-d coupling between π electrons and Mn²⁺ ions, a rearrangement of π spins occurs at low temperatures: the g-factor exhibits a large shift, the in-plane anisotropy reverses upon cooling, the linewidth broadens significantly, and the spin susceptibility increases during cooling with an inflection point near the phase transition temperature. Through careful analysis of the angular dependences of g(θ) and ΔH(θ), the effects of anisotropic Zeeman interaction and spin-phonon coupling were revealed. The results indicate the existence of two magnetically distinct BETS molecular chains, and the possibility of an alternating magnetic order in this system is discussed.\n17. The interplay between topology, defects and chiral order in the nearly-commensurate charge density wave of 1T-TaS2 Relevance Score: 3.0427 Authors: Michael Verhage, Martin Lee, Kees Flipse Link: http://arxiv.org/abs/2601.03379v1 Summary: In the nearly commensurate charge density wave (NC-CDW) of 1T-TaS₂, researchers reconstructed the full CDW order parameter through holographic analysis of scanning tunneling microscopy data and introduced a chiral order parameter directly linked to topological defects. This method revealed two distinct types of topological defects: vortex pairs in high-strain regions and glassy solitons or incommensurate networks. The study found that perturbations such as strain drive vortex nucleation and annihilation, leaving behind solitons pinned by disorder, while an electric field can induce soliton and incommensurate network motion, enabling controllable chirality switching through local melting of the order parameter. These results demonstrate the coupling mechanism between topological defects and chirality, providing a theoretical foundation for electric-field control of chirality at room temperature.\n18. Novel fast Li-ion conductors for solid-state electrolytes from first-principles Relevance Score: 3.0363 Authors: Tushar Singh Thakur, Loris Ercole, Nicola Marzari Link: http://arxiv.org/abs/2601.03151v1 Summary: This study proposes a high-throughput computational screening method for discovering novel fast lithium-ion conductors for application in all-solid-state electrolytes. From sources including the Crystallography Open Database, Inorganic Crystal Structure Database, and Materials Science Data Platform, over 30,000 lithium-containing experimental structures were screened; electronic insulators were identified through automated calculations, and molecular dynamics simulations using the ball-and-spring model—a method 200–500 times faster than density functional theory—were performed on approximately 1,000 structures to evaluate lithium-ion diffusivity. Subsequently, full first-principles molecular dynamics simulations were conducted on about 60 of the most promising unknown fast ionic conductors to compute their activation energy barriers. The results show that Li₇NbO₆ exhibits a notable ionic conductivity of approximately 5 mS/cm at room temperature. The paper also details the complete screening workflow, including a self-consistent procedure to enhance the accuracy of the ball-and-spring model, as well as methods for automated computation execution and result analysis. This study successfully identifies multiple new fast conductors, providing an efficient route for the discovery of solid-state electrolyte materials.\n19. Wafer-scale High-k SrTiO3 Dielectrics with Rational Barrier-layer Design for Low Leakage and High Charge Density Relevance Score: 3.0124 Authors: Majid Mohseni, Shivasheesh Varshney, Seung Gyo Jeong, Amber Walton, C. Daniel Frisbie, Bharat Jalan Affiliations: University of Minnesota Link: http://arxiv.org/abs/2601.02619v1 Summary: By hybrid molecular beam epitaxy, this study uniformly grew SrTiO₃ thin films on Nb:SrTiO₃, CaSnO₃/Nb:SrTiO₃, and 2-inch SiO₂/p-Si substrates, systematically comparing the effects of different barrier layers on dielectric properties. The results show that introducing a thin barrier layer beneath SrTiO₃ effectively suppresses leakage current and extends the usable voltage window; specifically, the ultra-wide-bandgap SiO₂ barrier layer enables a charge density exceeding 5×10¹³ cm⁻² at room temperature, a fivefold improvement over devices without a barrier layer. However, the low dielectric constant of SiO₂ reduces total capacitance, making its thickness a critical design parameter. The CaSnO₃ barrier layer also reduces leakage, but to a lesser extent. This work demonstrates that rational barrier layer engineering—including wafer-scale integration on silicon substrates—provides a clear pathway to achieving higher charge densities in SrTiO₃-based dielectric devices.\n20. Signatures of moiré intralayer biexcitons and exciton-phason coupling in WSe2/WS2 heterostructures Relevance Score: 3.0014 Authors: Ranju Dalal, Harsimran Singh, Rwik Dutta, Hariharan Swaminathan, Kenji Watanabe, Takashi Taniguchi, Mit H Naik, Manish Jain, Akshay Singh Affiliations: National Institute for Materials Science, University of Texas at Austin, Indian Institute of Science Link: http://arxiv.org/abs/2601.03045v1 Summary: By optically suppressing ultrafast charge transfer to interlayer excitons in WSe₂/WS₂ heterostructures, the dynamics of moiré intralayer excitons (IALX) were investigated, revealing a long lifetime (τ \u0026gt; 1000 ps) attributed to localized Wannier excitons and in-plane charge transfer characteristics. For the first time, moiré intravalley biexcitons were observed with a binding energy of approximately 16 meV, stabilized by the confinement of the moiré potential. Torsion-angle-dependent GHz oscillations were observed in the IALX dynamics, resulting from strong coupling between moiré IALX and phasons (ultrasoft shear phonon modes) on the order of ~10 μeV. These findings indicate that moiré superlattices can serve as interacting hybrid quantum systems for engineering nonequilibrium phenomena and GHz optoelectronic devices.\n","permalink":"https://nickelates.uk/en/posts/2026-01-06-arxiv-daily/","summary":"\u003cblockquote\u003e\n\u003cp\u003e\u003cstrong\u003eDaily Overview\u003c/strong\u003e:\nBased on the list of papers you provided, today\u0026rsquo;s daily overview does not include studies directly focused on the field of nickelate superconductors. However, several works discuss physical mechanisms or research methods highly relevant to the core issues currently concerning nickelate superconductivity, making them worthy of attention. The following is the overall introduction prepared for today\u0026rsquo;s post: — Dear readers, welcome to today\u0026rsquo;s daily overview of the field of nickelate superconductors. Although the highlighted works today do not directly study nickelates, they focus on key topics such as superconducting pairing mechanisms, electron-phonon coupling modulation, nematic orbital anisotropy, and the competition between charge density waves and superconductivity, providing important references for understanding nickelate superconductivity. For example, [1] proposes interlayer charge-transfer ferroelectric fluctuations as a pairing mechanism for van der Waals superconductors; [2] significantly enhances the superconducting transition temperature of A15-type LaH5.75 via Ba doping; [3] real-space images orbital nematicity in iron-based superconductors using laser PEEM; [5] reveals the competition between CDW and superconductivity in Janus MoXH monolayers; [8] explores electron pairing mechanisms without phonon mediation based on a two-band model. These findings expand the understanding of unconventional superconductivity and complement the current concerns in the nickelate superconductor field regarding electronic structure, pairing mechanisms, and competing orders.\n\u003cstrong\u003earXiv submission processing window\u003c/strong\u003e: 2026-01-05 21:10 to 2026-01-06 19:28 UTC.\u003c/p\u003e","title":"arXiv Daily: nickelate superconductors 2026-01-06"},{"content":" Daily Overview: Today’s highlight focuses on a deeper understanding of the electronic structure of mixed Ruddlesden–Popper nickelates. In [1], a study using polarization-resolved ultrafast spectroscopy reveals electronic nematicity with broken twofold rotational symmetry at low temperatures in bilayer La₃Ni₂O₇, while the trilayer La₄Ni₃O₁₀ remains isotropic. This finding suggests a potential link between nematic fluctuations and high-pressure superconducting pairing. Additionally, the study of the Ruddlesden–Popper double perovskite oxide Sr₃Co₂O₇ in [5] proposes a mechanism for charge-disproportionation-driven polar antiferromagnetic metal, a model that may provide insights into the synergy between layered structure and electronic correlations in nickelates. arXiv submission processing window: 2026-01-05 00:23 to 2026-01-05 19:00 UTC.\n1. Electronic Nematicity Revealed by Polarized Ultrafast Spectroscopy in Bilayer La$_3$Ni$_2$O$_7$ Relevance Score: 5.7100 Authors: Qi-Yi Wu, De-Yuan Hu, Chen Zhang, Hao Liu, Bo Chen, Ying Zhou, Zhong-Tuo Fu, Chun-Hui Lv, Zi-Jie Xu, Hai-Long Deng, Meng-Wu Huo, H. Y. Liu, Jun Liu, Yu-Xia Duan, Dao-Xin Yao, Meng Wang, Jian-Qiao Meng Link: http://arxiv.org/abs/2601.01702v1 Summary: Using polarized ultrafast pump-probe spectroscopy, the researchers comparatively investigated the normal-state electronic dynamics of bilayer La₃Ni₂O₇ and trilayer La₄Ni₃O₁₀ single crystals under ambient pressure. Both materials exhibit a density-wave transition accompanied by the opening of a quasiparticle relaxation bottleneck, yet their electronic responses display markedly different symmetries: trilayer La₄Ni₃O₁₀ remains optically isotropic across the entire temperature range, whereas bilayer La₃Ni₂O₇ shows clear twofold (C₂) rotational symmetry breaking—i.e., electronic nematicity—at low temperatures. This nematicity manifests in the anisotropy of slow quasiparticle relaxation dynamics and effective gap scale, and below 115 K it competes with a secondary isotropic order, leading to a non-monotonic temperature dependence of the nematic signal. This work reveals the presence of electronic nematic fluctuations in bilayer nickelates, which are absent in the trilayer system, suggesting a close relationship between electronic nematicity and high-pressure superconducting pairing in La₃Ni₂O₇, thereby providing key insights into the microscopic mechanism of this class of nickel-based superconductors.\n2. Evidence of anisotropic bulk superconductivity in disorder-induced ZrTe$_{3-x}$ Relevance Score: 4.3215 Authors: P. Manna, C. Patra, T. Agarwal, S. Srivastava, S. Sharma, P. Mishra, R. P. Singh Link: http://arxiv.org/abs/2601.01815v1 Summary: Through magnetic susceptibility, specific heat, and transport measurements, this study systematically investigates the superconductivity of disordered ZrTe₃₋ₓ (x=0.2) single crystals. The charge density wave is completely suppressed, and a bulk anisotropic type-II superconductivity with a transition temperature T_c=3.59(4) K is observed. Angle-dependent upper critical field measurements and the Berezinskii-Kosterlitz-Thouless transition confirm the intrinsic quasi-two-dimensional nature of superconductivity in this system. Experimental data indicate that the upper critical field is significantly lower than the Pauli limit, with orbital limit effects dominating the destruction of the superconducting state; calculations of the coherence length, penetration depth, and Ginzburg-Landau parameters further confirm the characteristics of a strong type-II superconductor. The second-order phase transition observed in specific heat measurements and the estimated electron-phonon coupling constant support an electron-phonon pairing mechanism. This study provides clear evidence for understanding disorder-induced quasi-two-dimensional superconducting systems.\n3. Fermi-surface-sheet dependent electron-phonon coupling in a borocarbide superconductor YNi$_2$B$_2$C Relevance Score: 4.3160 Authors: Taichi Terashima, Hiroyuki Takeya, Hisatomo Harima Link: http://arxiv.org/abs/2601.01700v1 Summary: This study presents de Haas-van Alphen (dHvA) oscillation measurements and band structure calculations for the borocarbide superconductor YNi₂B₂C. Improved band calculations successfully explain the origin of the previously unassigned large-frequency β and ζ oscillations. By comparing the experimental effective masses with band masses, the electron-phonon coupling strength for each orbit is determined, clearly revealing a Fermi surface sheet dependence: the electron-phonon coupling on band 28 is very weak, nearly vanishing when the magnetic field is parallel to the c-axis. This finding is consistent with previous experimental observations of dHvA oscillations from this orbit even at very low fields in the mixed state. This study provides crucial data for a precise understanding of electron-phonon coupling and holds significant reference value for current research on electron-phonon coupling-driven high-temperature superconductivity in high-pressure hydrides.\n4. Multiple nodal superconducting phases and order-parameter evolution in pressurized UTe$_2$ Relevance Score: 4.0871 Authors: Shuo Zou, Fengrui Shi, Zhuolun Qiu, Jialong Zhang, Yan Zhang, Weilong Qiu, Zhuo Wang, Hai Zeng, Yinina Ma, Zheyu Wu, Andrej Cabala, Michal Valiska, Ning Li, Zihan Yang, Kaixin Ye, Jiawen Zhang, Yanan Zhang, Kangjian Luo, Binbin Zhang, Alexander G. Eaton, Chaofan Zhang, Gang Li, Jianlin Luo, Wen Huang, Huiqiu Yuan, Xin Lu, Yongkang Luo Link: http://arxiv.org/abs/2601.01843v1 Summary: Through point-contact spectroscopy measurements on pressurized UTe₂ (001) surfaces, a zero-bias conductance peak was observed, confirming the existence of Andreev bound states and strongly indicating that the superconducting order parameter contains a p_z component. Quantitative analysis based on the extended Blonder-Tinkham-Klapwijk model reveals that the most likely superconducting pairing representations for UTe₂ under ambient and applied pressure are B_{2u} or B_{3u}, and the distinct superconducting phases (SC1, SC2, SC3) can be distinguished by a single parameter ⟨Δ_z⟩/⟨Δ_{x(y)}⟩, i.e., the relative weight of p_z-wave versus p_{x(y)}-wave pairing. These results impose strict constraints on the superconducting order parameter of UTe₂ and provide key spectroscopic evidence for the existence of multiple nodal superconducting phases under pressure tuning.\n5. Charge disproportionation as a possible mechanism towards polar antiferromagnetic metal in molecular orbital crystal Relevance Score: 4.0051 Authors: Yang Shen, Shuai Qu, Gang Li, Pu Yu, Guang-Ming Zhang Link: http://arxiv.org/abs/2601.02048v1 Summary: This paper proposes charge disproportionation as a possible mechanism for realizing polar antiferromagnetic metals in molecular orbital crystals with a negative charge-transfer energy gap, and validates it through first-principles DFT+U and density matrix renormalization group calculations on the representative Ruddlesden-Popper double perovskite oxide Sr₃Co₂O₇. The study finds that, due to the negative charge-transfer character of Co⁴⁺ and strong interlayer coupling, localized molecular orbitals formed from Co d_z² and d_xz/yz orbitals via hybridization with apical oxygen p orbitals preferentially emerge within each bilayer unit, developing antiferromagnetic order through Hubbard repulsion. Hund\u0026rsquo;s-rule-driven charge disproportionation leads to occupation imbalance of the remaining d_xy and d_x²-y² orbitals on different Co atoms within the same bilayer, breaking inversion symmetry and thereby producing polar metallicity. Meanwhile, this charge disproportionation mechanism causes conducting carriers to interact with interlayer localized spins via Hund coupling, generating in-plane double-exchange ferromagnetism. This molecular orbital formulation further provides an effective Hamiltonian for modeling the unconventional coexistence of metallicity, polarity, and antiferromagnetism in Sr₃Co₂O₇, potentially serving as a unifying framework broadly applicable to bilayer Ruddlesden-Popper perovskite oxides.\n6. Visualizing the low-energy electronic structure of the triplet superconductor UTe$_2$ through quasiparticle interference Relevance Score: 3.8705 Authors: Anuva Aishwarya, Hans Christiansen, Sheng Ran, Nicholas P. Butch, Brian M. Andersen, Andreas Kreisel, Shanta R. Saha, Johnpierre Paglione, Vidya Madhavan Affiliations: Washington University in St. Louis, Harvard University, University of Illinois at Urbana-Champaign, Canadian Institute for Advanced Research, University of Maryland, National Institute of Standards and Technology, University of Copenhagen Link: http://arxiv.org/abs/2601.02192v1 Summary: This study employs low-temperature spectroscopic imaging techniques to reveal the low-energy electronic structure of the spin-triplet superconductor UTe₂ (0-11) surface via quasiparticle interference. By introducing 1% thorium doping to create scattering centers, the signal detection of uranium-derived bands using scanning tunneling microscopy is enhanced. Quasiparticle interference images show that the scattering wave vectors primarily originate from the uranium d and f electron bands, which are closely associated with the formation of charge density waves (CDW) and pair density waves (PDW). Tunneling spectra reveal a gap-like feature at approximately -1 meV, with a corresponding CDW transition temperature of about 6.6 K, consistent with the known onset temperature of CDW. When the CDW is suppressed by an applied magnetic field, small circular Fermi pockets with strong dispersion emerge near the Fermi level, originating from strong f-electron correlation effects. Comparison with band structures calculated using a tight-binding model confirms that the interference patterns arise from electron scattering between cylindrical Fermi surfaces. This work clarifies the momentum-space structure of low-energy quasiparticles on the UTe₂ surface, providing key experimental evidence for understanding its unconventional spin-triplet superconductivity and interplay with intertwined orders such as CDW and PDW, while supporting the central role of f electrons in forming topological surface states and exotic quantum phenomena.\n7. Spin-correlation Driven Ferroelectric Quantum Criticality in a Perovskite Quantum Spin-liquid System, Ba3CuSb2O9 Relevance Score: 3.7184 Authors: Sayan Ghosh, Gourab Roy, Ekta Kushwaha, Mohit Kumar, Tathamay Basu Affiliations: Rajiv Gandhi Institute of Petroleum Technology Link: http://arxiv.org/abs/2601.01906v3 Summary: In the perovskite quantum spin liquid system Ba3CuSb2O9, experiments reveal spin-correlation-driven ferroelectric quantum criticality. The inverse dielectric constant follows a T² scaling, indicating that the material behaves as a quantum paraelectric without ferroelectric ordering, a hallmark of three-dimensional displacive ferroelectric quantum critical points. Magnetic measurements show no long-range magnetic order down to 1.8 K, but instead exhibit a power-law dependence of the inverse magnetic susceptibility χ⁻¹ ∝ T^(3/2), consistent with the Hertz-Millis theory of antiferromagnetic quantum critical fluctuations. Combined with known spin-orbit-lattice entanglement, these signatures reveal strong coupling between spin dynamics and the polar lattice. This work demonstrates that spin correlations drive ferroelectric quantum critical behavior in the absence of long-range order, and provides a new platform for exploring coupled quantum criticality in this material family via chemical or external pressure tuning.\n8. Enhancement of antiferromagnetic spin fluctuations in UTe$_2$ under pressure revealed by $^{125}$Te NMR Relevance Score: 3.7100 Authors: Devi Vijayan Ambika, Qing-Ping Ding, Corey E. Frank, Sheng Ran, Nicholas P. Butch, Yuji Furukawa Link: http://arxiv.org/abs/2601.02280v1 Summary: This study utilized 125Te nuclear magnetic resonance measurements to investigate in detail the relationship between the superconducting phases (SC1 and SC2) and magnetic fluctuations in single-crystal UTe2 under pressures ranging from 0 to 2.05 GPa. By comparing the temperature dependence of the nuclear spin-lattice relaxation rate divided by temperature (1/T1T) and the Knight shift along the a, b, and c crystallographic axes, direct evidence indicates that with increasing pressure, antiferromagnetic spin fluctuations are significantly enhanced while ferromagnetic fluctuations are suppressed. Combined with the distinct behaviors of the two superconducting phases under pressure (the Tc of SC1 decreases with pressure, while that of SC2 increases), these results support that ferromagnetic fluctuations are more conducive to the formation of SC1, whereas antiferromagnetic fluctuations are crucial for SC2. This finding clarifies the roles of different types of magnetic fluctuations in the multiple superconducting phases of UTe2, providing key insights into understanding its unconventional spin-triplet superconducting mechanism.\n9. Competing phases and domain structures of ferroelectric perovskites: the benefit of epitaxial (110) growth Relevance Score: 3.5725 Authors: Lan-Tien Hsu, Takeshi Nishimatsu, Anna Grünebohm Link: http://arxiv.org/abs/2601.02118v3 Summary: This study systematically investigates the effects of (110)-oriented strain on the phase and domain structures of three typical ferroelectric perovskite thin films—BaTiO₃, KNbO₃, and PbTiO₃—using first-principles-based effective Hamiltonian molecular dynamics simulations. Compared with conventional (100) orientation, (110) strain stabilizes a variety of metastable nanoscale configurations even at small strain values, including multi-domain structures with either in-plane or out-of-plane domain wall normals, heterophase coexistence in BaTiO₃ and KNbO₃, and complex superdomain patterns as well as antiferroelectric-like domains in PbTiO₃. These metastable structures hold promise for achieving large reversible functional responses, such as dielectric, piezoelectric, or electrocaloric effects. The findings reveal the advantages of (110)-oriented growth in tuning phase stability and domain engineering in ferroelectric thin films, offering new avenues for developing highly tunable functional devices.\n10. Emergent Spin Supersolids in Frustrated Quantum Materials Relevance Score: 3.5466 Authors: Yixuan Huang, Seiji Yunoki, Sadamichi Maekawa Link: http://arxiv.org/abs/2601.01890v2 Summary: In recent years, spin supersolids have been discovered in frustrated triangular lattice quantum antiferromagnets, providing a material platform beyond solid helium for the realization of supersolid states. The core feature of such spin supersolids is the coexistence of longitudinal spin order (breaking lattice translational symmetry) and transverse spin order (spontaneously breaking spin U(1) symmetry). Through systematic thermodynamic and spectroscopic experiments, combined with advanced numerical calculations, self-consistent phase diagrams have been established in candidate materials, including regions of low-field Y-shaped, intermediate-field up-up-down (UUD), and high-field V-shaped spin supersolids. The minimal theoretical model, such as the XXZ Heisenberg model, can well describe the global phase diagram, ground-state properties, and collective excitation spectra, and the experimentally observed gapless Goldstone modes and roton-like minima are consistent with numerical predictions. Moreover, the giant magnetocaloric effect observed in candidate materials offers potential for efficient demagnetization cooling, while the theoretically proposed dissipationless spin supercurrent holds promise for spin transport and spintronics. This review systematically summarizes the recent progress on spin supersolids in frustrated triangular lattice quantum antiferromagnets, compares experimental and theoretical results, and discusses characteristic spin transport phenomena as well as future directions for developing spin supersolids into functional quantum materials.\n11. An altermagnetic materials library in intercalated transition-metal dichalcogenides Relevance Score: 3.3982 Authors: Ezra Day-Roberts, Huan Wu, Onur Erten, A. S Botana Link: http://arxiv.org/abs/2601.02481v1 Summary: This study systematically investigates altermagnetism in intercalated transition metal dichalcogenides (TMDs) of the general formula T$_y$MX$_2$ (where T is a 3d transition metal, M is Nb or Ta, X is S or Se, and y = 1/3 or 1/4) using first-principles calculations. Symmetry analysis reveals that when the intercalated atoms exhibit A-type antiferromagnetic ordering within the 2H-structured TMD host, the materials belong to g-wave altermagnets. By calculating the energies of various magnetic configurations—ferromagnetic, A-type antiferromagnetic, and stripe antiferromagnetic—several candidate materials with stable A-type antiferromagnetic ground states were identified, such as V$_{1/3}$NbS$_2$ and Fe$_{1/4}$NbSe$_2$. These materials exhibit pronounced spin splitting near the Fermi level, reaching up to 100 meV. The competition between RKKY and superexchange interactions in determining the magnetic order is also discussed, revealing the regulatory effects of intercalated atom species and concentration on magnetism. This work provides a material library and design principles for realizing altermagnetism in layered two-dimensional materials.\n12. Emergent Anomalous Hall Effect in the Eu-Based Compound with a Diamond Network: The Centrosymmetric Cubic Antiferromagnet EuTi$_2$Al$_{20}$ Relevance Score: 3.3969 Authors: Ryuji Higashinaka, Kohsuke Sato, Ryosei Ideura, Masahiro Kawamata, Tatsuma D. Matsuda Link: http://arxiv.org/abs/2601.01788v1 Summary: This study investigates the centrosymmetric cubic antiferromagnet EuTi₂Al₂₀, in which magnetic Eu²⁺ ions form a diamond network. Below the Néel temperature TN = 3.3 K, the sample undergoes an antiferromagnetic transition, and two metamagnetic transitions (Hm₁ = 1.7 T, Hm₂ = 2.8 T) are observed along the [100] direction at 1.9 K, with a step-like magnetization behavior that defines an intermediate field-induced phase (Phase II). Resistivity and Hall effect measurements reveal that in Phase II, both the resistivity and Hall resistivity are significantly enhanced and remain nearly independent of the magnetic field; moreover, this phase exists in all field directions, but the transport response exhibits moderate directional dependence. The Hall resistivity cannot be fitted using conventional normal and anomalous Hall terms, suggesting the presence of a topological Hall effect. This feature is distinctly different from the strong direction-selective behavior of skyrmion lattice phases in many 4f electron compounds, indicating that Phase II may host a topological spin texture different from conventional skyrmion lattices. As temperature increases, the Phase II region contracts, and the associated anomalies disappear above approximately 3.5 K. This study provides an important candidate system for exploring novel topological magnetic structures based on centrosymmetric lattices.\n13. Instabilities of the Fractionalized Dirac Semimetal in the Kitaev-Kondo Model Relevance Score: 3.3817 Authors: Jennifer Lin, Frank Krüger Link: http://arxiv.org/abs/2601.02110v2 Summary: We study a honeycomb Kondo lattice model where Dirac conduction electrons are coupled to a spin-1/2 Kitaev quantum spin liquid. For weak Kondo coupling, the spin fractionalizes into a massless Dirac mode and three gapped vison Majorana fermions. Through second-order perturbation theory, the Kondo coupling generates local Hubbard repulsion and spin-spin interactions among the conduction electrons, as well as vertex couplings between electrons and massless Majorana fermions. We analyze the low-energy effective field theory using perturbative renormalization group (RG), taking into account additional density-density interactions generated during the RG flow. The results show that, regardless of the sign of the Kitaev coupling and the Fermi velocity ratio, the critical behavior is always governed by a single fixed point, at which the conduction electrons decouple from the Majorana fermions, while all electronic interactions (including the newly generated density-density repulsion) acquire finite positive values. Analysis of the magnetic susceptibility exponent further reveals that the leading instability of this fractionalized Fermi liquid is toward an antiferromagnetic spin density wave state, while superconducting pairing is suppressed.\n14. Magnetoelastic properties in the high-temperature magnetic phase of the skyrmion compound GdRu$_2$Si$_2$ Relevance Score: 3.3674 Authors: J. Sourd, D. A. Mayoh, G. Balakrishnan, M. Uhlarz, J. Wosnitza, S. Zherlitsyn Link: http://arxiv.org/abs/2601.01977v1 Summary: We investigated the magnetoelastic properties of skyrmion compound GdRu₂Si₂ single crystals under magnetic fields applied along the [001] and [110] directions. Ultrasound measurements revealed a series of sound velocity anomalies consistent with the previously reported complex phase diagram, with a focus on the recently discovered high-temperature magnetic phase (Phase VI). Experiments showed that this phase is easily suppressed when the field is applied along [001], but remains robust along [110]. We introduced a Landau theory and a microscopic toy model to describe the elastic response at zero field, and by qualitatively reproducing the anomalous behavior of different acoustic modes, we proposed a possible magnetic structure for this high-temperature phase. These results reveal magnetoelastic coupling between the localized Gd moments and itinerant Ru electrons via the RKKY interaction, providing key insights into the understanding of the complex magnetism in this system.\n15. Superconducting diode effect in fractal superconductors: fractional-order Ginzburg-Landau theory for Josephson junctions Relevance Score: 3.3560 Authors: Yuriy Yerin, Iman Askerzade Link: http://arxiv.org/abs/2601.02187v1 Summary: This paper establishes a fractional Ginzburg-Landau (GL) theoretical framework to describe nonreciprocal transport in Josephson junctions composed of fractal superconductors or superconducting media with nonlocal correlations. It is found that nonreciprocity and the superconducting diode effect arise from the coupling between the Lifshitz invariant and fractional dynamics, which effectively characterizes fractal geometry and finite-range memory effects. The authors adopt two complementary approaches: in the fractional integral GL formulation, integration over fractal space yields analytic solutions, revealing how rectification varies with the fractal dimension of the medium and the strength of the Lifshitz drift; in the fractional derivative formulation based on Agrawal’s variational principle and left-right Caputo operators, gauge-invariant free energy, GL equation, and current density are obtained. Using a two-mode plane-wave approximation, compact expressions for the current-phase relation and diode efficiency are derived, and the mapping of rectification amplitude onto the parameter space of fractional dynamics and Lifshitz/memory order is plotted. Exact one-sided solutions based on the Prabhakar function further confirm robust and tunable nonreciprocity, including near-ideal diode responses. This study indicates that by engineering fractal (fractional) transport through tuning the fractional order and Lifshitz strength, nearly perfect superconducting diodes can be achieved without external magnetic fields or geometric ratchets. In the integer limit of local dynamics and Lifshitz drift, both constructions reduce to the standard φ0 Josephson junction.\n16. Symmetric topological Mott insulator and Mott semimetal Relevance Score: 3.3521 Authors: Boran Zhou, Ya-Hui Zhang Link: http://arxiv.org/abs/2601.02485v1 Summary: This paper introduces the concept of symmetric topological Mott insulators (STMI), which goes beyond the Slater determinant picture within the Hartree-Fock framework. Through a bilayer Haldane-Hubbard model composed of localized orbitals on sublattice A and itinerant electrons on sublattice B, the authors find that tuning the sublattice potential drives an exciton pairing transition from BEC to BCS, resulting in a topological Mott insulator with Chern number C=1 per flavor. Extending to a single-layer spin model, an STMI with both charge edge modes and bulk local magnetic moments is obtained. At the quantum critical point between the STMI and a trivial Mott insulator, the system exhibits a Mott semimetal phase with a Dirac cone at the Γ point in its energy spectrum. Finally, the theory is applied to the AA-stacked MoTe₂/WSe₂ system, proposing that the ferromagnetic Chern insulator phase can be viewed as a descendant of the symmetric Mott semimetal at low temperatures. This work reveals symmetry-preserving topological Mott phases beyond mean-field theory in strongly correlated topological bands, offering a new mechanism for understanding correlated topological states in moiré materials.\n17. Electronic correlations and topology in Kondo insulator PuB$_6$ Relevance Score: 3.2611 Authors: K. Gofryk, S. Zhou, N. Poudel, N. Dice, D. Murray, T. Pavlov, C. Marianetti Link: http://arxiv.org/abs/2601.02312v1 Summary: Through low-temperature magnetotransport measurements and first-principles calculations, this study confirms that PuB₆ exhibits characteristics of a topological Kondo insulating state. Experimentally, single-crystal microflakes were extracted from polycrystalline multiphase samples using focused ion beam microfabrication, and the temperature-dependent resistivity shows a transition from high-temperature thermally activated behavior (with an energy gap of approximately 20 meV) to a low-temperature plateau, with resistivity decreasing as the surface-to-volume ratio increases, indicating surface-dominated conduction at low temperatures. The transverse magnetoresistance at 2 K exhibits a power-law dependence (MR ~ H^{1.3-1.4}), arising from mixed transport involving bulk parabolic bands and surface Dirac cones. Theoretically, the GGA+U method (U = 4 eV) combined with spin-orbit coupling successfully reproduces the topological band inversion, nontrivial Z₂ topological invariant (1;111), and (100) surface Dirac cones previously predicted by DMFT, while also calculating the phonon spectrum to verify structural stability at a computational cost far lower than that of DMFT. These results support PuB₆ as a strongly correlated topological insulator and demonstrate that GGA+U can efficiently describe its electronic, topological, and lattice properties.\n18. Anharmonic lattice dynamics study of phonon transport in layered and molecular-crystal indium iodides Relevance Score: 3.1418 Authors: Takuma Shiga, Yoshikazu Mizuguchi, Hiroshi Fujihisa Affiliations: Tokyo Metropolitan University, National Institute of Advanced Industrial Science and Technology (AIST), Toyota Technological Institute Link: http://arxiv.org/abs/2601.01766v1 Summary: This study systematically investigates phonon transport properties in layered indium iodide (InI) and molecular crystal indium iodide (InI₃) from both particle and wave perspectives using first-principles anharmonic lattice dynamics. The calculated lattice thermal conductivities of both materials remain below 1 W/m·K over a wide temperature range. Notably, the influence of wave-like phonon transport varies with composition: in InI₃, the wave contribution is comparable to the particle-like Peierls contribution, whereas in InI it is nearly negligible. For the experimentally reported high-pressure phase of InI₃, multiple ordered stacking models were constructed based on indications of stacking faults and partial indium site disorder; these models exhibit no significant energetic preference and yield similar lattice thermal conductivities, suggesting that in-plane thermal transport is predominantly governed by the vibrational properties of the In₂I₆ layers themselves rather than the specific stacking sequence. This work provides important insights into the mechanisms of phonon transport in structurally complex layered and molecular crystal systems.\n19. Topological Magnons and Giant Orbital Nernst Effect in a Zigzag Kitaev Antiferromagnet Relevance Score: 3.0690 Authors: Shreya Debnath, Saurabh Basu Link: http://arxiv.org/abs/2601.02342v1 Summary: This study constructs a model of a zigzag-ordered antiferromagnet incorporating extended Kitaev interactions and Dzyaloshinskii-Moriya interaction (DMI), and systematically investigates the topological phases and transport properties of magnons under an external magnetic field. Utilizing the linearized Holstein-Primakoff transformation and the Bogoliubov–de Gennes formalism, it is found that the hybridization of spin-up and spin-down magnons opens a bulk band gap, giving rise to a non-trivial topological phase characterized by a finite Chern number, chiral edge states, and a non-zero thermal Hall conductivity. Furthermore, the magnon orbital magnetic moment and its contribution to the Nernst response are considered, revealing that even without an external magnetic field, the system can exhibit a giant orbital Nernst conductance, which is more sensitive than the thermal Hall conductance in distinguishing different topological phases. In contrast, for the Néel-ordered configuration, even with DMI and Kitaev interactions, the Chern number vanishes, and both the thermal Hall and orbital Nernst conductances are significantly suppressed. This work unveils the high sensitivity of magnon orbital transport to band topology, offering a new route to realize topological magnon states in antiferromagnets with zero net magnetization.\n20. Boltzmann theory of the inverse Edelstein effect in a two-dimensional Rashba gas Relevance Score: 3.0621 Authors: Irene Gaiardoni, Mattia Trama, Alfonso Maiellaro, Claudio Guarcello, Francesco Romeo, Roberta Citro Link: http://arxiv.org/abs/2601.02473v1 Summary: This work systematically investigates the inverse Edelstein effect in a heterogeneous system composed of a ferromagnetic layer coupled with a Rashba two-dimensional electron gas, employing semiclassical Boltzmann theory. By deriving analytical expressions for charge and spin currents, the authors reveal how interfacial exchange interaction and spin-orbit coupling cooperatively modulate the spin-to-charge conversion efficiency, giving rise to distinct transport regimes. A key achievement is the derivation of closed-form analytical solutions, which facilitate a direct understanding of the underlying physics and enable transparent, quantitative comparison with experimental data from complex oxide interfaces such as LaAlO₃/SrTiO₃. The study demonstrates that parameters such as the chemical potential and Rashba coupling strength play critical roles in the conversion efficiency, and the theoretical framework provides a robust reference benchmark for experimental measurements.\n","permalink":"https://nickelates.uk/en/posts/2026-01-05-arxiv-daily/","summary":"\u003cblockquote\u003e\n\u003cp\u003e\u003cstrong\u003eDaily Overview\u003c/strong\u003e:\nToday’s highlight focuses on a deeper understanding of the electronic structure of mixed Ruddlesden–Popper nickelates. In [1], a study using polarization-resolved ultrafast spectroscopy reveals electronic nematicity with broken twofold rotational symmetry at low temperatures in bilayer La₃Ni₂O₇, while the trilayer La₄Ni₃O₁₀ remains isotropic. This finding suggests a potential link between nematic fluctuations and high-pressure superconducting pairing. Additionally, the study of the Ruddlesden–Popper double perovskite oxide Sr₃Co₂O₇ in [5] proposes a mechanism for charge-disproportionation-driven polar antiferromagnetic metal, a model that may provide insights into the synergy between layered structure and electronic correlations in nickelates.\n\u003cstrong\u003earXiv submission processing window\u003c/strong\u003e: 2026-01-05 00:23 to 2026-01-05 19:00 UTC.\u003c/p\u003e","title":"arXiv Daily: nickelate superconductors 2026-01-05"},{"content":" Daily Overview: Dear readers, welcome to today’s rapid overview of papers in the nickel-based superconductivity field. Although no studies directly targeting nickelates are included today, the work in [1] on the orbital separation between charge order and superconductivity in the cuprate La₂₋ₓSrₓCuO₄ is highly relevant to ongoing discussions in the nickel-based superconductivity field regarding multi-band electronic structure competition. That study, employing X-ray spectroscopy and c-axis uniaxial pressure, found that compressional strain drives an orbital separation between superconductivity (originating from the d_{x²-y²} state) and charge order (gradually shifting to the d_{z²} channel), suggesting that similar multi-order coexistence in nickel oxide superconductors also requires descriptions beyond a single-band model. arXiv submission processing window: 2026-01-03 23:26 to 2026-01-04 19:16 UTC.\n1. Orbital Separation of Charge Order and Superconductivity in La$_{2-x}$Sr$_{x}$CuO$_4$ Relevance Score: 4.4269 Authors: I. Biało, O. Gerguri, L. Martinelli, J. Küspert, J. Choi, M. Garcia-Fernandez, S. Agrestini, K. J. Zhou, E. Weschke, T. Kurosawa, N. Momono, M. Oda, C. Lin, Q. Wang, J. Chang Affiliations: PSI Center for Neutron and Muon Sciences CNM, The Chinese University of Hong Kong, European Synchrotron Radiation Facility, Hokkaido University, SLAC National Accelerator Laboratory, Muroran Institute of Technology, Universität Zürich, Korea Advanced Institute of Science \u0026amp; Technology (KAIST), Helmholtz-Zentrum Berlin für Materialien und Energie, Diamond Light Source Link: http://arxiv.org/abs/2601.01643v2 Summary: This study systematically investigates charge order in underdoped La₂₋ₓSrₓCuO₄ (x=0.125) using X-ray absorption spectroscopy (XAS) and oxygen K-edge resonant inelastic X-ray scattering (RIXS) combined with c-axis uniaxial pressure. The experiments reveal that compressive c-axis strain modifies charge order exclusively within the superconducting state, exhibiting pronounced polarization dependence: charge order is suppressed in the d_{x²-y²} channel while enhanced in the d_{z²} channel. XAS spectra further uncover strain-induced simultaneous changes in the oxygen pre-edge and upper Hubbard band, indicating enhanced d_{z²} orbital hybridization. These results demonstrate that c-axis pressure drives an orbital separation between superconductivity (originating from d_{x²-y²} states) and charge order (progressively shifting to the d_{z²} channel). This separation mechanism enables the coexistence of both orders in cuprates with minimal competition and suggests that the multi-order phase diagram of La₂₋ₓSrₓCuO₄ cannot be faithfully described by the single-band model typically used to depict cuprate physics.\n2. Isotropic Superconductivity in Room-temperature Superconductor LaSc$_{2}$H$_{24}$ Relevance Score: 4.2278 Authors: Zefang Wang, Wenbo Zhao, Yuan Ma, Hanyu Liu, Yanming Ma Link: http://arxiv.org/abs/2601.01398v1 Summary: This study systematically reveals the superconducting mechanism of the room-temperature superconductor LaSc₂H₂₄ through first-principles calculations and solutions of the anisotropic Migdal-Eliashberg equations. It is found that the introduction of scandium (Sc) transforms the anisotropic double gaps of LaH₁₀ into the isotropic single gap of LaSc₂H₂₄, thereby enhancing the superconducting critical temperature. This enhancement originates from the dual role of Sc 3d electrons: on one hand, the Sc-induced Jahn-Teller effect elongates specific interlayer H-H bonds, promoting hydrogen metallization and softening corresponding phonon modes, which strengthens electron-phonon coupling (EPC); on the other hand, Sc 3d electrons restructure the electronic configuration into an MgB₂-like architecture, forming Sc-H-Sc σ and π bonding states with EPC intensity comparable to that of LaH₁₀. More importantly, the strong hybridization between Sc and the hydrogen cages effectively merges the high-EPC H-H states with the extensive Sc-H states on the Fermi surface, avoiding gap separation and establishing a continuous distribution of large EPC constants. This work identifies Sc-induced gap unification as the core mechanism for achieving room-temperature superconductivity in LaSc₂H₂₄, providing a theoretical blueprint for designing superior ternary hydride superconductors.\n3. Exploring the Thermodynamic, Elastic, and Optical properties of LaRh2X2 (X = Al, Ga, In) low Tc Superconductors through First-Principles Calculations Relevance Score: 4.2243 Authors: Md. Hasan Shahriar Rifat, Mirza Humaun Kabir Rubel, Md. Borhan Uddin, Apon Kumar Datta, Md. Mijanur Rahaman, Jubair Hossan Abir Link: http://arxiv.org/abs/2601.01300v2 Summary: Through first-principles density functional theory calculations using the CASTEP code, this paper systematically investigates for the first time the structural, mechanical, elastic, electronic, vibrational, thermophysical, and optical properties of LaRh₂X₂ (X = Al, Ga, In) low-temperature superconductors. The optimized lattice parameters agree well with experimental values, and the Born stability criteria along with negative formation energies confirm the mechanical and thermodynamic stability of these materials. Poisson’s ratio and Pugh’s ratio indicate ductile characteristics, while low Debye temperatures, melting points, and Vickers hardness suggest relatively soft materials. Electronic band structures and densities of states reveal metallic behavior; charge density and Mulliken analysis indicate mixed covalent, ionic, and metallic bonding, and the coexistence of hole-type and electron-type sheets on the Fermi surface suggests possible multiband superconductivity. Phonon dispersions show that LaRh₂Al₂ and LaRh₂Ga₂ are dynamically stable, whereas LaRh₂In₂ exhibits dynamic instability likely associated with structural phase transitions. Optical property analysis points to potential for high-density optical data storage, and the electron-phonon coupling constant of approximately 0.56 indicates that these materials are weakly coupled low-temperature superconductors.\n4. Tripling of the Superconducting Critical Current Density in BaFe$_2$(As$_{1-x}$P$_x$)$_2$ Retained After Pressure Release Relevance Score: 3.7986 Authors: Jiangteng Liu, Alex Lopez, Zhaoyu liu, Jiun-Haw Chu, Serena Eley Link: http://arxiv.org/abs/2601.01328v1 Summary: This study employed a commercial pressure cell to perform magnetization measurements on overdoped BaFe₂(As₀.₆₂P₀.₃₈)₂ single crystals, systematically investigating the effects of hydrostatic pressure (up to 1.08 GPa) and its subsequent release at room temperature on the superconducting critical current density and vortex dynamics. The results show that pressure has a negligible effect on the superconducting critical temperature, but significantly enhances the critical current density Jc, substantially reduces the thermally activated vortex motion rate S, and alters the dominant vortex pinning mechanism. More importantly, these effects are irreversible: after pressurization and depressurization at room temperature, the crystal retains the enhanced Jc and reduced S. At 8 K and 0.5 T, after one to two pressure cycles, Jc increases by a factor of three and S decreases by over 40%. Furthermore, the second magnetization peak at 22 K disappears after pressure cycling, and analysis indicates that the pinning mechanism transitions from being dominated by δκ pinning to a mixture of δTc and surface pinning. These findings demonstrate the potential of pressure cycling as a simple method for enhancing the critical current density of superconductors, offering a promising alternative to traditional strategies such as chemical doping or the introduction of artificial pinning centers.\n5. Common sublattice-pure van Hove singularities in the kagome superconductors $\\textit{A}$V$_{3}$Sb$_{5}$ ($\\textit{A}$ = K, Rb, Cs) Relevance Score: 3.7178 Authors: Yujie Lan, Yuhao Lei, Congcong Le, Brenden R. Ortiz, Nicholas C. Plumb, Milan Radovic, Xianxin Wu, Ming Shi, Stephen D. Wilson, Yong Hu Affiliations: University of California Santa Barbara, Hefei National Laboratory, Chinese Academy of Sciences, Paul Scherrer Institute, Chongqing University, Zhejiang University, RIKEN Link: http://arxiv.org/abs/2601.01428v1 Summary: Using high-resolution polarization-dependent angle-resolved photoemission spectroscopy, this study systematically reveals a unified normal-state electronic structure in the Kagome superconductor family AV₃Sb₅ (A = K, Rb, Cs), which deviates significantly from density functional theory predictions. Several common pure sublattice van Hove singularities (VHS) are found near the Fermi level, originating from strong hybridization between V-d and Sb-p orbitals, rather than from the previously assumed mixed-sublattice type. Experimental evidence indicates that such hybridization-driven pure sublattice VHS can significantly promote bond order fluctuations, likely serving as a key factor underlying the unconventional charge density wave order in this system. Orbital-selective renormalization effects are also observed, with Sb-p orbital-dominated bands showing particularly pronounced deviations from DFT calculations. These findings provide direct spectroscopic evidence for hybridization-driven VHS formation in Kagome metals and establish a unified framework for understanding the intertwined electronic instabilities—such as charge density wave, superconductivity, and electronic chirality—in AV₃Sb₅.\n6. Sol-Gel-Derived NiO/ZnO Thin Films with Single and Heterostructure Layers for Electrochemical Energy Storage Relevance Score: 3.6040 Authors: Miss Nourin Nurain Amina, Md Noushad Hossain, Muhammad Shahriar Bashar, Munira Sultana, Md. Salahuddin Mina Link: http://arxiv.org/abs/2601.01479v2 Summary: Single-layer and heterostructured NiO/ZnO thin films were fabricated on fluorine-doped tin oxide (FTO) substrates using sol-gel and spin-coating techniques, with NaCl doping employed to enhance the capacitive performance of ZnO. The morphology, structure, and optical properties of the films were characterized by scanning electron microscopy, X-ray diffraction, and UV-visible spectroscopy, revealing that the direct bandgaps of ZnO and Na-doped ZnO ranged from 3.17 to 3.31 eV, while NiO exhibited a wider bandgap of 3.81 eV. Electrochemical performance was evaluated in a three-electrode system with 1 M KOH electrolyte using cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy. The results showed that the single-layer NiO film achieved a specific capacitance of 1.391 F/g, whereas the NiO/ZnO heterostructure significantly improved charge storage capacity due to synergistic effects, reaching a maximum specific capacitance of 1.627 F/g at a current density of 2.0 mA/cm². Furthermore, sodium doping effectively enhanced the capacitive performance of ZnO. This study demonstrates the potential of sol-gel-derived oxide heterostructures and doped thin films as low-cost, scalable electrode materials for supercapacitors, suitable for portable electronic devices and energy storage systems.\n7. Atomic structure and formation mechanism of a newly discovered charge density wave in the m=2 monophosphate tungsten bronze Relevance Score: 3.5129 Authors: Arianna Minelli, Elen Duverger-Nedellec, Olivier Perez, Alain Pautrat, Adrien Girard, Johnathan Bulled, Marek Mihalkovič, Marc de Boissieu, Alexei Bosak Affiliations: University of Oxford, Sorbonne Université, Univ. Bordeaux, European Synchrotron Radiation Facility, University of Grenoble Alpes, Slovak Academy of Sciences, Oak Ridge National Laboratory, University of Caen Basse-Normandie Link: http://arxiv.org/abs/2601.01606v1 Summary: In the family of monophosphate tungsten bronzes, the m=2 member was previously considered the only compound that does not undergo electronic instability at low temperatures. This study, through diffraction and resistivity measurements, reveals the existence of a charge density wave (CDW) phase in this compound, with a transition temperature of 290 K and an incommensurate modulation vector q=0.245b*+ξc*. Using diffuse and inelastic X-ray scattering to investigate pre-transitional dynamics, a Kohn anomaly was clearly observed. By combining structural analysis and electronic transport measurements, and aided by molecular dynamics simulations, the paper systematically elucidates the contributions of lattice and electrons in the phase transition, revealing that this newly discovered electronic instability is not entirely driven by an electronic CDW but results from the interplay between structural and electronic factors.\n8. Imaging Intermediate Melting Phases of Dual Magnetic-Field-Stabilized Wigner Crystals Relevance Score: 3.3603 Authors: Chaofei Liu, Jianwang Zhou, Wenao Liao, Zeyu Jiang, Chao Zhang, Tingfei Guo, Tianyou Zhai, Wenhao Zhang, Ying-Shuang Fu, Qi-Kun Xue Affiliations: Beijing Computational Science Research Center, Huazhong University of Science and Technology, Wuhan Institute of Quantum Technology, Southern University of Science and Technology Link: http://arxiv.org/abs/2601.01531v1 Summary: This study directly imaged the melting intermediate phase of dual Wigner crystals stabilized by high magnetic fields in a monolayer VCl3/graphene system using scanning tunneling microscopy (STM). Under strong magnetic fields, two distinct Wigner crystals with significantly different critical temperatures (Tc) and lattice periods formed: one with a record-high Tc and high electron density, which gradually melted upon reducing the magnetic field through an orientationally ordered intermediate nematic phase; the other with a lower Tc exhibited an anomalous electron liquid intermediate phase during melting, characterized by an energy-independent modulation period. First-principles calculations confirmed that the band-selective occupation of electrons transferred at the interface is the microscopic mechanism driving the formation of the dual Wigner crystals. Atomic-scale real-space imaging revealed markedly different melting pathways for the two crystals, providing critical insights into the microscopic phase transition from order to disorder in Wigner crystals and constructing a phase diagram parameterized by both quantum and thermal fluctuations.\n9. Generating unconventional spin-orbit torques with patterned phase gradients in tungsten thin films Relevance Score: 3.3488 Authors: Lauren J. Riddiford, Anne Flechsig, Shilei Ding, Emir Karadza, Niklas Kercher, Tobias Goldenberger, Elisabeth Müller, Pietro Gambardella, Laura J. Heyderman, Aleš Hrabec Affiliations: ETH Zurich, PSI Link: http://arxiv.org/abs/2601.01429v1 Summary: By using direct-write laser annealing to pattern spin-orbit torque at the mesoscale in tungsten thin films, current-induced magnetization switching without an external magnetic field was achieved. The study utilized transmission electron microscopy, resistivity, and second harmonic measurements to track the continuous crystalline phase transition of the tungsten film from the β-phase with high spin-orbit coupling and high resistivity to the α-phase with low spin-orbit coupling and low resistivity as the laser fluence increased. By patterning gradients of varying steepness within the tungsten phase, spin-orbit torque channels were formed, and when combined with the CoFeB interface, sufficiently strong gradients enabled magnetization switching in magnetic wires without the need for an external magnetic field. This method leverages the unique microstructure of mixed-phase tungsten to achieve precise control over local electron current density, direction, and spin-orbit torque efficiency, providing a new approach for designing efficient spintronic devices.\n10. Predicting Coherent B2 Stability in Ru-Containing Refractory Alloys Through Thermodynamic Elastic Design Maps Relevance Score: 3.2323 Authors: Avik Mahata Link: http://arxiv.org/abs/2601.01326v1 Summary: This study proposes a physically guided machine learning framework that integrates high-throughput density functional theory calculations, random forest screening, and symbolic regression to overcome the inherent contradiction between high stability and low elastic strain in ruthenium-based B2 intermetallic compounds. By deriving closed-form physical laws, the framework quantifies the penalty of lattice strain on solution temperature: a 1% lattice mismatch leads to an approximate 200°C reduction in solution temperature. This finding indicates that simply maximizing thermodynamic driving force is insufficient to achieve a stable B2 phase; multicomponent alloying is a structural necessity. Experimental validation supports the symbolic regression design rules and indicates that ternary additions such as Al and Ti act as lattice regulators, effectively eliminating elastic penalties. This work establishes a rigorous, constraint-based alloy design protocol, providing a theoretical foundation for precisely constructing zero-mismatch, high-stability microstructures, thereby overcoming the bottleneck of ruthenium-based refractory alloys in high-temperature applications.\n11. Electrical Regulation of Transverse Spin Currents in Unconventional Magnetic Ferroeletrics Relevance Score: 3.2139 Authors: Yudi Yang, Zhuang Qian, Ruichun Xiao, Yuanyuan Xu, Hua Wang, Shi Liu, Congjun Wu Link: http://arxiv.org/abs/2601.01499v1 Summary: Using first-principles calculations and symmetry analysis, this study confirms that the hexagonal multiferroic material YMnO₃ is an ideal system for realizing the unconventional magnetic β-phase, which features a non-collinear, non-coplanar antiferromagnetic order and exhibits intrinsic spin-momentum locking along with topological spin texture. It is found that, without the need for relativistic spin-orbit coupling, an electric field perpendicular to the thin film can generate a transverse pure spin current in this system, and this spin current is closely tied to the ferroelectric polarization of the material: symmetry analysis shows that the spin current response is allowed only when the system possesses ferroelectric polarization that breaks inversion symmetry, while it is strictly forbidden at 180° domain walls where polarization vanishes. Based on this mechanism, the authors propose a nonvolatile spin transistor design that switches spin current conductance by modulating the ferroelectric domain wall density via gate voltage: a uniformly polarized single-domain state corresponds to a high-conductance “on” state, whereas a high-density domain wall state suppresses spin current generation, corresponding to an “off” state. This work provides a material realization and physical blueprint for all-electrically controlled, low-energy-consumption antiferromagnetic spintronic devices.\n12. Manipulating Anomalous Transport via Crystal Symmetry in 2D Altermagnets Relevance Score: 3.0417 Authors: Dan Li, Shuaiyu Wang, Jiabin chen, Zeling Li, Chaoxi Cui, Lei Li, Lei Wang, Zhi-Ming Yu, Xiaodong Zhou, Xiao-Ping Li Link: http://arxiv.org/abs/2601.01564v1 Summary: This paper proposes a new method for controlling anomalous transport in two-dimensional altermagnets via crystal symmetry engineering. Based on symmetry analysis, it is shown that two-dimensional altermagnets with an out-of-plane Néel vector themselves do not exhibit an anomalous Hall effect; once the crystal symmetry connecting the two magnetic sublattices is broken, an anomalous Hall response is immediately induced, and the sign of both the anomalous Hall conductivity and the anomalous Nernst conductivity can be flexibly reversed through manipulation of the symmetry-breaking term. Using a tight-binding model and first-principles calculations, the scheme is validated with the two-dimensional altermagnet Cr₂O₂ as an example: under continuous uniaxial strain, this material can sequentially exhibit the anomalous Hall effect and the quantum anomalous Hall effect, and the sign of both effects can be flipped simply by rotating the strain direction by C₄z. Furthermore, the anomalous Nernst effect and its sign reversal are also revealed. This work provides a novel strategy for manipulating anomalous transport via crystal symmetry, with significant application potential.\n13. Recent Progress in Ultrafast Dynamics of Transition-Metal Compounds Studied by Time-Resolved X-ray Techniques Relevance Score: 3.0152 Authors: Hiroki Wadati, Kohei Yamamoto, Kohei Yamagami Link: http://arxiv.org/abs/2601.01354v1 Summary: X-ray absorption spectroscopy and X-ray magnetic circular dichroism have long been essential element-specific tools for probing the electronic and magnetic properties of transition metal compounds. In recent years, the development of femtosecond lasers has opened new avenues for studying non-equilibrium dynamics in condensed matter, but conventional optical techniques lack element and orbital specificity, making it difficult to disentangle coupled charge, spin, and lattice responses in complex materials. The advent of X-ray free-electron lasers and laboratory-based high-harmonic generation sources has extended X-ray absorption and scattering techniques into the femtosecond time domain. Time-resolved X-ray absorption spectroscopy, X-ray magnetic circular dichroism, and resonant soft X-ray scattering now provide direct and complementary access to element- and momentum-resolved ultrafast dynamics. This review summarizes recent advances in these techniques, focusing on laser-induced demagnetization, spin-state transitions, and changes in valence and structure of transition metal compounds in pump–probe experiments. It also discusses progress in tabletop high-harmonic generation-based X-ray spectroscopy and its integration with large-scale X-ray free-electron laser facilities. These developments offer powerful means to visualize the evolution of charge, spin, orbital, and lattice degrees of freedom under non-equilibrium conditions, providing new insights into the ultrafast control of quantum materials.\n","permalink":"https://nickelates.uk/en/posts/2026-01-04-arxiv-daily/","summary":"\u003cblockquote\u003e\n\u003cp\u003e\u003cstrong\u003eDaily Overview\u003c/strong\u003e:\nDear readers, welcome to today’s rapid overview of papers in the nickel-based superconductivity field. Although no studies directly targeting nickelates are included today, the work in [1] on the orbital separation between charge order and superconductivity in the cuprate La₂₋ₓSrₓCuO₄ is highly relevant to ongoing discussions in the nickel-based superconductivity field regarding multi-band electronic structure competition. That study, employing X-ray spectroscopy and c-axis uniaxial pressure, found that compressional strain drives an orbital separation between superconductivity (originating from the d_{x²-y²} state) and charge order (gradually shifting to the d_{z²} channel), suggesting that similar multi-order coexistence in nickel oxide superconductors also requires descriptions beyond a single-band model.\n\u003cstrong\u003earXiv submission processing window\u003c/strong\u003e: 2026-01-03 23:26 to 2026-01-04 19:16 UTC.\u003c/p\u003e","title":"arXiv Daily: nickelate superconductors 2026-01-04"},{"content":" Daily Overview: Today\u0026rsquo;s highlights focus on multi-angle advances in superconductivity mechanisms, orbitronics, and exciton physics. Although these studies are not directly targeting nickelate superconductors, the enhanced electron-phonon coupling, orbital Hall effect in light 3d metals, and spectroscopic signatures of local exciton pair breaking involved are closely related to the pairing mechanisms, orbital manipulation, and quantum critical behavior currently of interest in nickel-based superconductivity. [1] First-principles calculations reveal that applying 12% biaxial tensile strain to the two-dimensional carbon allotrope THO-graphene can achieve a superconducting transition temperature of 45 K, providing an example of strain-tuned electron-phonon coupling. [2] The demonstration of vertical magnetization switching driven by the orbital Hall effect in the light 3d transition metal nitride VN, with an orbital torque efficiency up to -0.41, offers new insights for designing orbitronic devices. [3] Using scanning tunneling spectroscopy, subgap states induced by a single Te vacancy impurity that break exciton pairs are observed in the excitonic insulator Ta₂Pd₃Te₅, revealing atomic-scale fingerprints of local de-pairing effects. arXiv submission processing window: 2026-01-03 07:22 to 2026-01-03 08:30 UTC.\n1. Strain-triggered high-temperature superconducting transition in two-dimensional carbon allotrope Relevance Score: 4.0864 Authors: Tian Yan, Ru Zheng, Jin-Hua Sun, Fengjie Ma, Xun-Wang Yan, Miao Gao, Tian Cui, Zhong-Yi Lu Link: http://arxiv.org/abs/2601.01100v1 Summary: Through first-principles calculations, this study demonstrates that applying biaxial tensile strain alone can induce a superconducting transition in THO-graphene, a two-dimensional carbon allotrope composed of triangular, hexagonal, and octagonal rings. While free-standing THO-graphene is not superconducting, the application of strain significantly enhances electron-phonon coupling, enabling electron pairing and the emergence of superconductivity. At a critical biaxial tensile strain of 12%, the superconducting transition temperature reaches up to 45 Kelvin, representing the highest record among two-dimensional elemental superconductors. The study reveals the mechanism by which strain enhances electron-phonon coupling through increasing the density of states at the Fermi level and softening specific in-plane vibrational modes, providing an important paradigm for purely strain-engineered metal-to-superconductor transitions in two-dimensional systems.\n2. Efficient magnetization switching driven by orbital torque originating from light 3d-transition-metal nitrides Relevance Score: 3.5860 Authors: Gaurav K. Shukla, Yoshio Miura, Mayank K. Singh, Shinji Isogami Affiliations: National Institute for Materials Science, Kyoto Institute of Technology Link: http://arxiv.org/abs/2601.01115v1 Summary: This study demonstrates a method for achieving perpendicular magnetization switching by utilizing the orbital Hall effect (OHE) in light 3d transition metal nitride VN. By growing [Co/Pt]3 multilayers as the ferromagnetic layer on (111)-textured face-centered cubic VN layers, second harmonic Hall measurements reveal that the orbital torque efficiency of the VN(7.5 nm)/[Co/Pt]3 structure reaches as high as -0.41, significantly outperforming ferromagnetic reference samples such as Co, Py, and CoFeB, indicating that the orbital current originating from VN is efficiently converted into spin current in the [Co/Pt]3 ferromagnetic layer. Under an applied in-plane magnetic field, fully current-driven magnetization switching is achieved, while partial field-free switching is realized without an external field, with critical current densities comparable to those of tungsten-based spin-orbit torque devices. First-principles calculations confirm that VN exhibits a large orbital Hall conductivity and a small spin Hall conductivity near the Fermi level. These results suggest that the combination of light 3d transition metal nitrides with (111)-oriented Co/Pt ferromagnetic multilayers holds promise for maximizing the magnetization switching efficiency in orbitronic devices.\n3. Spectral Visualization of Excitonic Pair Breaking at Individual Impurities in Ta2Pd3Te5 Relevance Score: 3.2427 Authors: Lianzhi Yang, Deguang Wu, Hanbo Zhang, Yao Zhang, Xiutong Deng, Chao Zhang, Tianyou Zhai, Wenhao Zhang, Youguo Shi, Rui Wang, Chaofei Liu, Ying-Shuang Fu Affiliations: Wuhan Institute of Quantum Technology, Huazhong University of Science and Technology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Nanjing University Link: http://arxiv.org/abs/2601.01096v1 Summary: Using scanning tunneling spectroscopy, this study observes exciton pair breaking induced by individual Te vacancy impurities in the excitonic insulator Ta₂Pd₃Te₅. These impurities generate a pair of sub-gap spectral peaks within the exciton gap, whose energies vary with defect configuration and can be continuously tuned by the tip electric field, indicating controllable impurity scattering. Spatial mapping reveals that these sub-gap states exhibit anisotropic electron-hole coupling characteristics, and combined with mean-field model analysis, they are attributed to exciton pair breaking. In regions of strong electron-hole imbalance, a second pair of lower-energy sub-gap states is also observed, revealing the interplay of pair breaking between different excitonic order parameters. This work provides atomic-scale spectroscopic fingerprints of local exciton depairing, offering key insights into the critical behavior of exciton condensation.\n","permalink":"https://nickelates.uk/en/posts/2026-01-03-arxiv-daily/","summary":"\u003cblockquote\u003e\n\u003cp\u003e\u003cstrong\u003eDaily Overview\u003c/strong\u003e:\nToday\u0026rsquo;s highlights focus on multi-angle advances in superconductivity mechanisms, orbitronics, and exciton physics. Although these studies are not directly targeting nickelate superconductors, the enhanced electron-phonon coupling, orbital Hall effect in light 3d metals, and spectroscopic signatures of local exciton pair breaking involved are closely related to the pairing mechanisms, orbital manipulation, and quantum critical behavior currently of interest in nickel-based superconductivity. [1] First-principles calculations reveal that applying 12% biaxial tensile strain to the two-dimensional carbon allotrope THO-graphene can achieve a superconducting transition temperature of 45 K, providing an example of strain-tuned electron-phonon coupling. [2] The demonstration of vertical magnetization switching driven by the orbital Hall effect in the light 3d transition metal nitride VN, with an orbital torque efficiency up to -0.41, offers new insights for designing orbitronic devices. [3] Using scanning tunneling spectroscopy, subgap states induced by a single Te vacancy impurity that break exciton pairs are observed in the excitonic insulator Ta₂Pd₃Te₅, revealing atomic-scale fingerprints of local de-pairing effects.\n\u003cstrong\u003earXiv submission processing window\u003c/strong\u003e: 2026-01-03 07:22 to 2026-01-03 08:30 UTC.\u003c/p\u003e","title":"arXiv Daily: nickelate superconductors 2026-01-03"},{"content":" Daily Overview: Dear readers, welcome to today\u0026rsquo;s quick overview of papers in the field of nickel-based superconductivity. Although no new papers directly studying nickelates were published today, several works explore physical mechanisms highly relevant to the current core issues in nickel-based superconductivity. Among them, [1] reveals the promotion of superconducting transition temperature by nematic fluctuations in CuxTiSe₂ through elastoresistance measurements, providing a material platform for the nematic fluctuation-mediated superconducting mechanism—nematic order and its fluctuations being one of the electronic states of great interest in the nickel-based superconductivity field. Meanwhile, [4] theoretically investigates the robustness of flat-band superconductivity in kagome lattices under disorder, finding that preserving flat-band degeneracy effectively resists disorder-induced degradation. This conclusion offers insights into understanding the possible flat-band electronic structures in nickelates and their superconductivity-enhancing effects. These works enrich the physical picture closely related to nickel-based superconductivity from different perspectives. arXiv submission processing window: 2026-01-02 02:52 to 2026-01-02 17:11 UTC.\n1. Nematic-fluctuation-mediated superconductivity in CuxTiSe2 Relevance Score: 4.1367 Authors: Xingyu Lv, Yang Fu, Shangjie Tian, Ying Ma, Shouguo Wang, Cedomir Petrovic, Xiao Zhang, Hechang Lei Link: http://arxiv.org/abs/2601.00723v1 Summary: This study investigates the evolution of electronic nematic fluctuations in Cu-intercalated TiSe₂ single crystals using an elastoresistance measurement system. Experimental results show that the elastoresistance coefficient of pristine TiSe₂ exhibits Curie-Weiss-law divergence at high temperatures, confirming the presence of nematic fluctuations. As the Cu intercalation content increases, the characteristic temperature T* of the nematic fluctuations is progressively suppressed, approaching zero near the optimal superconducting doping concentration (x ≈ 0.09); further increasing the Cu content leads to a negative T*, and superconductivity is concomitantly suppressed. These results indicate that critical fluctuations of the nematic phase transition play a key role in enhancing the superconducting transition temperature in CuxTiSe₂, providing a unique material platform for understanding the nematic fluctuation-mediated superconducting mechanism.\n2. AI-Guided Computational Design of a Room-Temperature, Ambient- Pressure Superconductor Candidate: Grokene Relevance Score: 3.7607 Authors: DEARDAO DeSci Collaborative Team, Yanhuai Ding Affiliations: Xiangtan University, DEARDAO Decentralized Science Initiative Link: http://arxiv.org/abs/2601.00931v1 Summary: This study proposes a novel two-dimensional superlattice named Grokene, derived from graphene, identified through an AI-guided materials discovery workflow utilizing large language models. Computational simulations reveal that Grokene possesses a high electron-phonon coupling constant (approximately 3.8) and a significant logarithmically averaged phonon frequency (approximately 1650 K), yielding mean-field critical temperatures of about 325 K and 310 K as calculated by the Allen-Dynes formula and the fully anisotropic Eliashberg equation, respectively, indicating its potential for room-temperature superconductivity under ambient pressure. However, its strict two-dimensional nature induces phase fluctuations, restricting the observable superconducting transition in a monolayer to approximately 120 K under the Berezinskii-Kosterlitz-Thouless mechanism. To elevate the BKT temperature to room temperature, the authors propose strategies such as few-layer stacking, substrate or gate engineering, optimization of the superlattice structure, and doping levels. This integrated workflow combines AI-driven materials discovery with advanced many-body theories including DFPT/EPW, Eliashberg, and RPA, providing a systematic and reproducible framework for exploring novel superconductors. The study recommends experimental synthesis and comprehensive characterization to evaluate these computational predictions and investigate pathways toward practical ambient-pressure superconductivity.\n3. Doping induced itinerant ferromagnetism and enhanced ferroelectricity in BL-InSe Relevance Score: 3.5413 Authors: Junlan Shi, Li Chen, Jiani Zhang, Botao Fu Link: http://arxiv.org/abs/2601.00574v1 Summary: Using first-principles calculations, this study predicts that ferroelectricity can be generated in bilayer InSe through interlayer sliding, and ferromagnetism can be induced via carrier doping. The energetically most stable AB stacking spontaneously breaks the out-of-plane mirror symmetry, yielding switchable vertical polarization (saturation polarization of 0.089 pC/m) with a low polarization reversal barrier of 28.8 meV per unit cell. Unexpectedly, low-concentration hole doping not only fails to suppress ferroelectric polarization but actually enhances it due to anomalous layer-dependent electron occupation—holes preferentially occupy the top layer—contrary to the conventional screening effect. Meanwhile, the unique Mexican-hat-shaped valence band of bilayer InSe gives rise to a van Hove singularity, and hole doping induces itinerant half-metallic ferromagnetism, with the interlayer spin density difference linearly dependent on doping concentration and switchable by reversing the polarization direction. These results demonstrate the possibility of realizing coexisting ferroelectric and ferromagnetic orders in originally nonpolar, nonmagnetic bilayer InSe, offering a feasible platform for constructing voltage-tunable multiferroic materials through stacking and doping.\n4. Superconductivity in the kagome Hubbard model under the flat-band-preserving disorder Relevance Score: 3.4956 Authors: Jicheol Kim, Dong-Hee Kim Link: http://arxiv.org/abs/2601.00540v1 Summary: We studied disordered flat-band superconductivity in the attractive Hubbard model on a kagome lattice, comparing disorder that preserves the flat band (FBP) with random hopping disorder that destroys the flat-band degeneracy (HOP). Using Bogoliubov–de Gennes mean-field calculations, we found that the superfluid weight is significantly more robust under FBP disorder, although the system still undergoes a superconductor–insulator transition at sufficiently strong disorder. In the weak-coupling limit, the superfluid weight under FBP disorder exhibits an almost linear dependence on the interaction strength, confirming the persistent flat-band character, whereas HOP disorder leads to the exponential behavior characteristic of dispersive bands. Furthermore, through exact diagonalization of the single-particle density matrix, we identified occupation spectral structures attributed to flat-band states, revealing the connection between the resilience of flat bands and the enhanced robustness of superconductivity. These results indicate that preserving the flat-band degeneracy in flat-band systems can effectively counteract the detrimental effects of disorder on superconductivity.\n5. About the origin of the magnetic ground state of Tb$_{2}$Ir$_{2}$O$_{7}$ Relevance Score: 3.4494 Authors: Y. Alexanian, E. Lhotel, J. Robert, S. Petit, E. Lefrançois, P. Lejay, A. Hadj-Azzem, F. Damay, J. Ollivier, B. Fåk, R. Ballou, S. De Brion, V. Simonet Link: http://arxiv.org/abs/2601.00749v1 Summary: This study systematically investigates the peculiar magnetic ground state of Tb₂Ir₂O₇ using neutron diffraction, inelastic neutron scattering (down to dilution temperatures), and heat capacity measurements. The experiments reveal that below 1.5 K, the Tb³⁺ magnetic moments not only adopt an all-in-all-out (AIAO) order induced by the Ir molecular field along the local Ising axis but also exhibit an antiferromagnetic component perpendicular to this axis (attributed to the Γ₉ representation), with this composite magnetic structure remaining unchanged at lower temperatures. Crystal field excitations are observed at high energies (~5.9 meV and ~11.2 meV), while low-energy magnetic excitations with dispersive features (~1.5 meV and ~2.8 meV) behave like excitons. A mean-field model based on crystal field effects, Tb-Tb bilinear interactions, and the Ir molecular field (supplemented by RPA calculations) reproduces the existence of magnetic order and the main characteristics of the excitation spectrum, but the predicted ordering temperature is significantly lower than the experimental value (~15 K), indicating that more complex interactions (such as greater Ir contributions or disorder effects) are required to fully explain the observations. The heat capacity shows only a broad anomaly around ~15 K rather than a sharp second-order phase transition peak, suggesting that the ordering transition may be frustrated or associated with short-range correlations.\n6. Electronic-Entropy-Driven Solid-Solid Phase Transitions in Elemental Metals Relevance Score: 3.1970 Authors: S. Azadi, S. M. Vinko, A. Principi, T. D. Kuehne, M. S. Bahramy Link: http://arxiv.org/abs/2601.00740v1 Summary: Using finite-temperature density functional theory, we computed the thermodynamic phase diagrams of 17 elemental metals with hexagonal close-packed (hcp), face-centered cubic (fcc), and body-centered cubic (bcc) structures. By evaluating the Helmholtz free energy differences as a function of electronic temperature (up to 7 eV), we identified solid-solid phase transitions driven entirely by electronic entropy. The studied systems include Zr, Ti, Cd, Zn, Co, Mg (hcp); Ni, Cu, Ag, Al, Pt, Pb (fcc); and Cr, W, V, Nb, Mo (bcc) in their ground-state structures. Except for Mg and Pb, all systems undergo one or two solid-solid phase transitions induced solely by electronic entropy. Transition electronic temperatures were extracted from the free energy crossing points, and systematic trends were analyzed. The results demonstrate that under strong electronic excitation, electronic entropy is a key factor determining the structural stability of metals.\n7. High-Temperature Deformation Behavior of Co-Free Non-Equiatomic CrMnFeNi Alloy Relevance Score: 3.1604 Authors: F. J. Dominguez-Gutierrez, M. Frelek-Kozak, G. Markovic, M. A. Strozyk, A. Daramola, M. Traversier, A. Fraczkiewicz, A. Zaborowska, T. Khvan, I. Jozwik, L. Kurpaska Affiliations: Institute for Technology of Nuclear and Other Mineral Raw Materials, University of Edinburgh, National Centre for Nuclear Research, Mines Saint-Etienne Link: http://arxiv.org/abs/2601.00619v1 Summary: This study systematically investigates the high-temperature plastic deformation behavior of a cobalt-free, non-equiatomic CrMnFeNi high-entropy alloy (HEA-1) through a combined experimental and computational approach. The alloy is designed to maintain a stable face-centered cubic (fcc) phase over a wide temperature range and to balance stacking fault energy for enhanced work hardening capability and ductility. Tensile tests reveal a decrease in strength with increasing temperature, attributed to thermally activated deformation mechanisms and microstructural evolution. Molecular dynamics simulations capture the variations in dislocation motion, stacking fault formation, and twin nucleation with strain and temperature in both single-crystal and polycrystalline models. Electron backscatter diffraction (EBSD) experiments confirm the generation of twins and grain boundary activity during deformation, while Schmid factor maps elucidate local slip and anisotropic deformation characteristics. Compared to the classic Cantor alloy (which contains cobalt), this cobalt-free alloy exhibits higher strength at elevated temperatures, primarily due to the elimination of cobalt, while maintaining good twinning-induced plasticity through controlled nickel content and stacking fault energy, thereby retaining excellent mechanical properties at high temperatures.\n","permalink":"https://nickelates.uk/en/posts/2026-01-02-arxiv-daily/","summary":"\u003cblockquote\u003e\n\u003cp\u003e\u003cstrong\u003eDaily Overview\u003c/strong\u003e:\nDear readers, welcome to today\u0026rsquo;s quick overview of papers in the field of nickel-based superconductivity. Although no new papers directly studying nickelates were published today, several works explore physical mechanisms highly relevant to the current core issues in nickel-based superconductivity. Among them, [1] reveals the promotion of superconducting transition temperature by nematic fluctuations in CuxTiSe₂ through elastoresistance measurements, providing a material platform for the nematic fluctuation-mediated superconducting mechanism—nematic order and its fluctuations being one of the electronic states of great interest in the nickel-based superconductivity field. Meanwhile, [4] theoretically investigates the robustness of flat-band superconductivity in kagome lattices under disorder, finding that preserving flat-band degeneracy effectively resists disorder-induced degradation. This conclusion offers insights into understanding the possible flat-band electronic structures in nickelates and their superconductivity-enhancing effects. These works enrich the physical picture closely related to nickel-based superconductivity from different perspectives.\n\u003cstrong\u003earXiv submission processing window\u003c/strong\u003e: 2026-01-02 02:52 to 2026-01-02 17:11 UTC.\u003c/p\u003e","title":"arXiv Daily: nickelate superconductors 2026-01-02"},{"content":" Daily Overview: In today\u0026rsquo;s paper overview, although there is no direct study on nickelate superconductors, several works explore physical mechanisms closely related to the core issues of nickel-based superconductivity. [1] analyzes the masking of the ferromagnetic quantum critical point by spin density waves in NbFe₂, providing a new experimental paradigm for understanding possible quantum critical behavior in infinite-layer nickelates. [4] constructs a unified topological phase diagram of the quantum Hall and superconducting vortex lattice states, revealing the mechanism by which Landau level mixing induces topological superconductivity in the weak-pairing limit, offering insights for designing topological phases in nickel-based superconductors. Additionally, [5] investigates the effect of electron-hole asymmetry on Δ_T noise in superconducting quantum point contacts, providing a theoretical framework for studying non-equilibrium transport at nickel-based superconducting interfaces. These works enrich the understanding of related physical phenomena from different perspectives. arXiv submission processing window: 2025-12-31 20:20 to 2026-01-01 17:44 UTC.\n1. Spin-density wave of ferrimagnetic building blocks masking the ferromagnetic quantum-critical point in NbFe2 Relevance Score: 3.5614 Authors: T. Poulis, G. Mani, J. Sturt, W. J. Duncan, H. Thoma, V. Hutanu, B. Ouladdiaf, I. Kibalin, M. H. Lemee, P. Manuel, A. Neubauer, C. Pfleiderer, F. M. Grosche, P. G. Niklowitz Link: http://arxiv.org/abs/2601.00101v1 Summary: In the metallic magnet NbFe₂, a longitudinal spin-density wave (SDW) structure that masks the ferromagnetic quantum critical point has been fully resolved for the first time through spherical neutron polarimetry and high-intensity single-crystal neutron diffraction. This SDW exhibits long-wavelength, incommensurate modulation with a low average magnetic moment, formed by the stacking of ferrimagnetic building blocks—composed of antiferromagnetically coupled ferromagnetic sheets—along the c-axis. The magnetization cancels only on a mesoscopic scale of approximately 50–90 Å, indicating a local resemblance to the ferromagnetic parent phase and an unconventional emergence rooted in the underlying ferromagnetic quantum criticality. This discovery provides key experimental evidence for understanding how the ferromagnetic quantum critical point is supplanted by a modulated order in clean band magnets.\n2. Engineering Ideal 2D Type-II Nodal Line Semimetals via Stacking and Intercalation of van der Waals Layers Relevance Score: 3.4921 Authors: Li Chen, Junlan Shi, Jiani Zhang, Botao Fu Link: http://arxiv.org/abs/2601.00407v1 Summary: This study proposes a bottom-up strategy for constructing ideal two-dimensional type-II nodal line semimetals through van der Waals layer stacking and atomic intercalation. Using monolayer hexagonal aluminum nitride (h-AlN) as a prototype, the fluorine-intercalated bilayer AlN system (F@BL-AlN) exhibits symmetry-protected type-II nodal rings at the Fermi level after preserving the mirror symmetry (ℳ_z) and modulating interlayer hybridization. First-principles calculations reveal that fluorine intercalation not only tunes the interlayer coupling strength but also precisely pins the Fermi level at the nodal line energy position via charge redistribution, thereby stabilizing the type-II semimetallic phase. The electronic structure of this system can be continuously tuned by an external electric field and biaxial strain, and the enhanced density of states at the nodal line gives rise to van Hove singularities, which further induce spontaneous ferromagnetic ordering, resulting in a ferromagnetic topological semimetallic state. This work provides a universal platform for designing two-dimensional type-II nodal line semimetals and offers clear guidance for their experimental realization.\n3. High-pressure structural and lattice-dynamics study of Yttria-Stabilized Zirconia Relevance Score: 3.4381 Authors: Shennan Hu, Baihong Sun, Wenting Lu, Shiyu Feng, Bihan Wang, Hirokazu Kadobayashi, Yuzhu Wang, Xingya Wang, Lili Zhang, Bora Kalkan, Azkar Saeed Ahmad, Elissaios Stavrou Link: http://arxiv.org/abs/2601.00302v1 Summary: This study employed in situ synchrotron X-ray diffraction and Raman spectroscopy to investigate the room-temperature high-pressure structural evolution of 3 mol% and 8 mol% yttria-doped yttria-stabilized zirconia (YSZ) up to 40 GPa in diamond anvil cells. Through combined analysis of the two techniques, pressure-induced transformations toward higher symmetry structures were observed: under initial compression, the small amount of monoclinic phase present under ambient conditions gradually transformed to the tetragonal phase, a process completed at approximately 10 GPa; for 3YSZ, the resulting single tetragonal phase then transformed to the t\u0026rsquo;\u0026rsquo; phase at higher pressures, further converting to the cubic phase above 28 GPa; for 8YSZ, the tetragonal and t\u0026rsquo;\u0026rsquo; phases coexisted up to 31 GPa, subsequently transforming together to the cubic phase, which remained stable to the maximum pressure. All phase transitions were fully reversible upon decompression with minimal hysteresis, with only the ambient monoclinic phase essentially disappearing. This work emphasizes that because XRD is insensitive to oxygen displacement and Raman spectroscopy struggles to distinguish the tetragonal from the t\u0026rsquo;\u0026rsquo; phase, their combined use is crucial for accurately unraveling high-pressure phase transitions in YSZ; moreover, the study reveals a potential pathway for achieving \u0026ldquo;structural purification\u0026rdquo; of YSZ by eliminating the monoclinic phase under high pressure, which may optimize material properties.\n4. Unified topological phase diagram of quantum Hall and superconducting vortex-lattice states Relevance Score: 3.3481 Authors: Daniil S. Antonenko, Liang Fu, Leonid I. Glazman Link: http://arxiv.org/abs/2601.00108v2 Summary: This paper constructs the global topological phase diagram of a two-dimensional electron gas under a quantized magnetic field and the proximity effect of a superconducting vortex lattice, by analyzing the Bogoliubov–de Gennes Hamiltonian with arbitrary ratios of pairing strength, magnetic field, and chemical potential. The key finding is that Landau level mixing plays a crucial role, splitting the integer quantum Hall transition line into a sequence of phase transitions protected by the symmetry of the superconducting vortex lattice, characterized by larger jumps in Chern numbers of both signs, even in the weak-pairing limit. When the chemical potential is tuned to the energy of a given Landau level, weak pairing induces either trivial or topological superconductivity depending on the level index. The resulting phase diagram is highly nontrivial, containing multiple topological superconducting phases with chiral quasiparticle edge modes, providing a complete picture for understanding the unified topological behavior of the quantum Hall effect and superconductivity.\n5. $Δ_T$ Noise from Electron-Hole Asymmetry in Normal and Superconducting Quantum Point Contacts Relevance Score: 3.3116 Authors: Sachiraj Mishra, Colin Benjamin Link: http://arxiv.org/abs/2601.00402v1 Summary: This study focuses on the behavior of Δ_T noise in two-terminal hybrid nanostructures: normal metal–quantum dot contact–normal metal (NQN) and normal metal–quantum dot contact–superconductor (NQS). Unlike previous symmetric junctions with insulating barriers, the quantum dot contact breaks electron–hole symmetry, enabling a finite thermovoltage under zero total charge current. At this thermovoltage, the paper self-consistently calculates the Δ_T noise and reveals significant differences from electron–hole symmetric junctions. Key findings include: the Δ_T noise in NQN and NQS junctions exhibits oscillations as a function of Fermi energy, a phenomenon absent in insulating barrier junctions; Andreev reflection in NQS junctions enhances the Δ_T noise compared to NQN junctions, with a maximum enhancement factor of 16, though this ratio decreases with rising temperature due to thermal activation of quasiparticle transport above the superconducting gap. Additionally, the behavior of the normalized Δ_T noise (analogous to the Fano factor) is systematically analyzed. This work establishes the first self-consistent framework for analyzing Δ_T noise in superconducting hybrid junctions with broken electron–hole symmetry, clearly demonstrating how Andreev reflection fundamentally reshapes Δ_T noise beyond the zero thermovoltage regime, offering a more comprehensive picture of charge fluctuations in non-equilibrium transport under linear response.\n6. Sample thickness dependence of structural and magnetic properties in $α$-RuCl$_3$ Relevance Score: 3.2831 Authors: Paige Harford, Ezekiel Horsley, Subin Kim, Young-June Kim Link: http://arxiv.org/abs/2601.00210v1 Summary: By employing mechanical exfoliation to control the thickness of α-RuCl3 single crystals and utilizing magnetization measurements, this paper systematically investigates the thickness dependence of structural and magnetic phase transitions. A non-destructive exfoliation protocol was successfully applied to thin crystals down to approximately 30 μm, revealing improved sample quality after exfoliation. Initially, high-quality thick samples exhibited a single magnetic ordering transition near 7 K, whereas with decreasing thickness, additional magnetic features progressively emerged at 10 K and 12 K. These extra features appeared both in damage-free exfoliation and in exfoliation that introduced damage, accompanied by changes in the structural thermal hysteresis: the hysteresis range of thick samples shrank upon exfoliation, while thin samples retained a larger hysteresis interval. By comparing samples of different initial quality and thickness (S1, S2, S3), the authors attribute the 10 K/12 K magnetic features to the persistent residual C2/m structure that fails to fully transform into the R structure at low temperatures. This work establishes a reliable non-destructive exfoliation method and elucidates the structural origin of multiple magnetic anomalies in small-sized or low-quality samples, indicating that the completeness of the structural phase transition is a crucial factor determining magnetic behavior.\n7. Magnon Superlattices around Skyrmions in Frustrated Magnets Relevance Score: 3.2043 Authors: Adarsh Hullahalli, Christos Panagopoulos, Christina Psaroudaki Link: http://arxiv.org/abs/2601.00363v1 Summary: Based on atomic-scale skyrmions in centrosymmetric frustrated magnets, this study reveals a new class of real-space crystal-like localized modes arising from the hybridization of magnons with topological spin textures possessing helicity degrees of freedom, using linear spin-wave theory and Landau-Lifshitz-Gilbert equation simulations. The results show that when the magnon wavelength matches the skyrmion size, strong interference effects occur, leading to the formation of a magnon superlattice shaped by both the internal structure of the skyrmions and the Mexican-hat-type magnon dispersion. Furthermore, helicity-driven nonlinear dynamics produce dispersive magnon bands with nontrivial Chern numbers within the first magnon gap. These findings provide fundamental insights into magnon behavior in complex spin environments and establish frustrated magnets as versatile platforms for manipulating spin excitations at the atomic scale.\n8. Spectral Sampling of Boron Diffusion in Ni Alloys: Cr and Mo Effects on Bulk and Grain Boundary Transport Relevance Score: 3.0939 Authors: Tyler D. Doležal, Rodrigo Freitas, Ju Li Affiliations: Air Force Institute of Technology, Massachusetts Institute of Technology Link: http://arxiv.org/abs/2601.00117v1 Summary: This study introduces a spectral sampling framework to quantify the diffusion activation energy of boron in nickel alloys and reveals the effects of chromium and molybdenum on bulk diffusion and interstitial transport at grain boundaries. In bulk diffusion, the distribution of boron migration energy barriers exhibits modality dependent on solute type and spatial arrangement: both chromium and molybdenum increase barriers in symmetric cages but introduce directional asymmetry in partially decorated environments. Extending the framework to the Σ5⟨100⟩{210} symmetric tilt grain boundary, it is found that chromium preserves in-plane low-barrier mobility while suppressing out-of-plane transport, directing boron into favorable mid-plane voids; molybdenum, in contrast, reduces boron mobility across all directions, leading to an additional two orders of magnitude decrease in average diffusivity at 800°C and a five-order reduction in out-of-plane transport relative to chromium. Both elements promote segregation via negative segregation energies but through distinct mechanisms: chromium facilitates rapid redistribution and stabilization of boron at interfacial sites, consistent with the formation of chromium-enriched borides; molybdenum creates deeper and more uniform segregation wells that strongly anchor boron. These complementary behaviors explain the experimental prevalence of chromium- and molybdenum-enriched borides at grain boundaries and carbide interfaces in nickel-based superalloys. This work establishes spectral sampling as a transferable framework for interpreting diffusion in disordered alloys and designing doping strategies to control transport at complex interfaces.\n","permalink":"https://nickelates.uk/en/posts/2026-01-01-arxiv-daily/","summary":"\u003cblockquote\u003e\n\u003cp\u003e\u003cstrong\u003eDaily Overview\u003c/strong\u003e:\nIn today\u0026rsquo;s paper overview, although there is no direct study on nickelate superconductors, several works explore physical mechanisms closely related to the core issues of nickel-based superconductivity. [1] analyzes the masking of the ferromagnetic quantum critical point by spin density waves in NbFe₂, providing a new experimental paradigm for understanding possible quantum critical behavior in infinite-layer nickelates. [4] constructs a unified topological phase diagram of the quantum Hall and superconducting vortex lattice states, revealing the mechanism by which Landau level mixing induces topological superconductivity in the weak-pairing limit, offering insights for designing topological phases in nickel-based superconductors. Additionally, [5] investigates the effect of electron-hole asymmetry on Δ_T noise in superconducting quantum point contacts, providing a theoretical framework for studying non-equilibrium transport at nickel-based superconducting interfaces. These works enrich the understanding of related physical phenomena from different perspectives.\n\u003cstrong\u003earXiv submission processing window\u003c/strong\u003e: 2025-12-31 20:20 to 2026-01-01 17:44 UTC.\u003c/p\u003e","title":"arXiv Daily: nickelate superconductors 2026-01-01"}]