Paper

Daily Overview: This post sorts papers by relevance to nickelate superconductors. Summaries are AI-generated and may contain errors. arXiv submission processing window: times are unavailable (UTC). 1. Observation of correlated plasmons in low-valence nickelates Relevance Score: 4.9427 Authors: Y. Shen, W. He, J. Sears, Xuefei Guo, Xiangpeng Luo, A. Roll, J. Li, J. Pelliciari, Xi He, I. Bozovic, Junjie Zhang, J. F. Mitchell, V. Bisogni, M. Mitrano, S. Johnston, M. P. M. Dean Link: http://arxiv.org/abs/2601.12160v1 Summary: Using resonant inelastic X-ray scattering (RIXS) at the oxygen K-edge, plasmon collective excitations were observed in the low-valence nickelate Pr4Ni3O8 and compared with the overdoped cuprate La₂₋ₓSrₓCuO₄. The experiments revealed that the nickelate plasmons exhibit dispersive behavior within the in-plane momentum, but with significantly lower velocity and stronger damping than the cuprate, and they become overdamped and disappear at much smaller momenta. Random phase approximation (RPA) calculations indicate that these differences originate from reduced electron hopping and enhanced long-range Coulomb interaction screening in the nickelate, where both the in-plane hopping integral and Coulomb interaction strength are substantially smaller than in the cuprate. Furthermore, the out-of-plane plasmons in the nickelate showed no discernible dispersion, possibly due to its trilayer coupling structure. Temperature-dependent studies found that the plasmons in Pr4Ni3O8 soften with increasing temperature, whereas in the cuprate the energy remains nearly constant while damping increases, suggesting the presence of additional correlations such as stripe fluctuations in the nickelate. These results reveal a unique charge screening landscape in nickelates, where weakened electron hopping and enhanced Coulomb screening are key distinguishing features from cuprates, potentially explaining the lower superconducting transition temperature of nickelates and providing quantitative experimental constraints for analogies between the two material families. ...

arXiv Daily: nickelate superconductors 2026-01-18

Daily Overview: This post sorts papers by relevance to nickelate superconductors. Summaries are AI-generated and may contain errors. arXiv submission processing window: times are unavailable (UTC). 1. 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. ...

arXiv Daily: nickelate superconductors 2026-01-12

Daily Overview: This post sorts papers by relevance to nickelate superconductors. Summaries are AI-generated and may contain errors. arXiv submission processing window: times are unavailable (UTC). 1. 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. ...

arXiv Daily: nickelate superconductors 2026-01-10

Daily Overview: This post sorts papers by relevance to nickelate superconductors. Summaries are AI-generated and may contain errors. arXiv submission processing window: times are unavailable (UTC). 1. 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. ...

arXiv Daily: nickelate superconductors 2026-01-05

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 “upper Hubbard” 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.

This study developed a megapascal-level high-pressure oxygen-assisted chemical synthesis route that successfully enabled the effective growth of infinite-layer nickelates extending to heavier rare earth elements, with composition (RE₁₋ᵧRE’ᵧ)₁₋ₓEuₓNiO₂ (RE/RE’: Pr, Nd, Sm, Gd, Dy). Hole doping was realized through Eu²⁺/Eu³⁺ valence variation. At the superconducting dome boundaries of Nd₁₋ₓEuₓNiO₂ and Pr₁₋ₓEuₓNiO₂ systems, robust uniaxial anisotropic magnetic-field reentrant superconductivity was observed, arising from the competition between Eu²⁺ 4f⁷ magnetic moments and magnetic fluctuations, while the optimally doped regions exhibited conventional high-temperature superconductivity with a critical current density reaching ~266 kA/cm² at 2 K, surpassing that of traditional Sr/Ca-doped systems. Further introduction of different RE′ magnetic ions allowed tuning of the exchange field strength and thereby modulation of quantum criticality, both enhancing the reentrant behavior and elevating T_c to 40.1 K. This work reveals the critical role of rare-earth 4f magnetic moments in modulating pairing strength and quantum criticality, establishing a synthetic foundation for utilizing the infinite-layer nickelate platform to investigate 4f-related unconventional superconductivity and quantum phase transitions.