Paper

Daily Overview: Today’s highlights focus on deepening the understanding of the electronic structure of hybrid Ruddlesden-Popper nickelates. In [1], the research team, using ultra-low-temperature scanning tunneling microscopy/spectroscopy, observed for the first time in (La,Pr)₃Ni₂O₇ films an energy-symmetric, flat-bottom U-shaped superconducting gap with zero residual density of states and a gap exceeding 40 meV, achieving zero-resistance temperatures above 20 K at ambient pressure. The temperature- and magnetic-field-dependent characteristics of the gap indicate a nodeless gap function at very low temperatures, revealing the nature of high-temperature superconductivity in bilayer nickel oxides. In [2], by comparing the spin and orbital excitations of undoped infinite-layer PrNiO₂ and insulating CaCuO₂ using momentum-resolved and polarization-resolved RIXS, it was found that both support three-dimensional antiferromagnetic order with similar three-dimensional spin-spin correlations. However, the Ni-dxy peak energy is significantly lower and the dispersion direction is opposite, attributed to different orbital superexchange coupling mechanisms. Meanwhile, spin fluctuations in the nickelate have lower energy, and doped charges are more localized. These two works, from the perspectives of superconducting gap and magnetic orbital dynamics, respectively, deepen the understanding of the electronic structure and pairing mechanism in nickel-based superconductors. arXiv submission processing window: 2026-05-18 00:00 to 2026-05-18 00:00 UTC. ...

arXiv Daily: nickelate superconductors 2026-05-18

Daily Overview: The May 16 digest keeps two papers that are directly relevant to nickelate superconductivity. The first uses atomic-resolution scanning tunneling microscopy and spectroscopy to observe a nodeless U-shaped superconducting gap in (La,Pr)₃Ni₂O₇ films, emphasizing that oxygen-content control is essential for obtaining intrinsic spectra. The second proposes a shear-stress-constrained superconductivity picture, using local constrained deformation of the Ni-O framework to connect superconductivity in high-pressure bulk and epitaxial thin-film Ruddlesden-Popper nickelates. Together, these two works provide complementary views on pairing signatures, sample sensitivity, and reproducibility in nickelate superconductors. ...

arXiv Daily: Nickelate superconductors 2026-05-16

Daily Overview: Today’s highlights focus on an in-depth understanding of the intrinsic electronic structure and mechanical constraint mechanisms of superconductivity in hybrid Ruddlesden-Popper nickelates. In [1], the research team, using atomic-resolution scanning tunneling microscopy, observed for the first time a nodeless U-shaped superconducting gap (approximately 14 and 20 meV) in (La,Pr)₃Ni₂O₇ ultrathin films, revealing that oxygen content control is key to obtaining the intrinsic superconducting gap. This provides direct atomic-scale evidence for nodeless pairing symmetry in bilayer nickelates. Meanwhile, [2] proposes from a mechanical perspective a shear-stress-constrained superconductivity (SSCS) framework, stating that the metastable RP lattice can enter the superconducting state only within a local shear strain window of the Ni-O framework. This view consistently explains the effects of pressure, substrate, oxygen stoichiometry, and other factors on superconductivity, and unifies phenomena in bulk high-pressure and epitaxial thin films within the same physical picture. These two works advance the understanding of core issues in the field of nickel-based superconductivity—intrinsic pairing symmetry and conditions for superconducting phase stability—from the perspectives of experimental observation and theoretical unification, respectively. arXiv submission processing window: 2026-05-15 00:00 to 2026-05-15 00:00 UTC. ...

arXiv Daily: nickelate superconductors 2026-05-15

Daily Overview: Today’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. ...

arXiv Daily: Nickelate superconductors 2026-05-14

Daily Overview: Today’s highlights focus on an in-depth understanding of the superconducting state and transport properties of bilayer Ruddlesden-Popper nickelates. In [1], Meng Zhang and Xi Yan systematically review the experimental progress of bilayer nickelate superconducting thin films under ambient pressure, pointing out that the reproducibility of pure-phase films, the microscopic origin of the two-step superconducting transition, the effects of oxygen defects and substrate doping, and the position of the Ni 3d({z^2})-derived γ band remain unresolved core issues. They call for establishing a more quantitative correlation among crystal structure, orbital reconstruction, and superconductivity. In [2], Seiichiro Onari et al., using a multi-orbital tight-binding model, reveal the crucial role of quasi-quantum metric terms in the temperature dependence of the Hall coefficient. This effect originates from orbital-selective renormalization induced by spin fluctuations in the Ni d({z^2}) orbital, successfully explaining the experimentally observed T-linear resistivity and the increase of the Hall coefficient with decreasing temperature. This provides a unified theoretical framework for understanding non-Fermi liquid transport in bilayer nickelates. arXiv submission processing window: 2026-05-13 00:00 to 2026-05-13 00:00 UTC. ...

arXiv Daily: nickelate superconductors 2026-05-13