Paper

Daily Overview: Today’s highlights focus on deepening the understanding of the electronic structure of hybrid Ruddlesden–Popper nickelates. Two resonant inelastic X‑ray scattering studies reveal, from the perspectives of doping and strain respectively, the intrinsic connection between spin excitations and superconductivity in bilayer nickelates: in La₃₋ₓSrₓNi₂O₇ thin films, beyond the superconducting dome, coherent spin excitations undergo magnetic collapse, with their quenching occurring concurrently with the reconstruction of the apical‑oxygen‑mediated d_(z²)–p_z–d_(z²) orbitals, clearly indicating that maintaining a local d_(z²) magnetic structure and robust interlayer apical‑oxygen coupling is a fundamental prerequisite for achieving high‑temperature superconductivity. Meanwhile, strain engineering of La₃Ni₂O₇ thin films demonstrates that compressive strain enhances the interlayer antiferromagnetic superexchange J_z accompanied by the emergence of superconductivity, while tensile strain markedly suppresses spin excitations and d_(z²)‑related excitations, providing direct spectroscopic evidence for the theoretical picture of pairing promoted by interlayer antiferromagnetic superexchange. In addition, a first‑principles calculation reveals a unique bipartite electronic system in a new bilayer nickel oxide, La₃Ni₂O₅F, where conventional Ni dpσ hole carriers coexist with E* electron carriers originating from interstitial electronic states, forming a cylindrical electron Fermi surface and velocity‑parallel potential Dirac points. This two‑component electronic configuration is expected to induce unconventional superconducting behavior, offering a possible route toward new designs of apical‑oxygen‑free nickelate superconductors. arXiv submission processing window: 2026-06-10 00:00 to 2026-06-10 00:00 UTC. ...

arXiv Daily: nickelate superconductors 2026-06-10

Daily Overview: Today’s highlights focus on an in-depth analysis of the microscopic mechanisms and low-energy physics of superconductivity in bilayer nickelates. One study constructs a pairing theory based on interlayer triplon excitations, successfully reproducing the double-peak structure and opposite gap signs observed in experimental tunneling spectra. It identifies interband s± pairing as the dominant characteristic and reveals that the α band, despite its smaller density of states, hosts the larger superconducting gap. Another work employs density functional theory combined with cluster dynamical mean-field theory to show that the low-energy states are formed by the hybridization of a dynamic singlet from interlayer 3z²−r² orbitals with itinerant x²−y² orbitals. It further elucidates the qualitatively distinct tuning of orbital selectivity and itinerancy by hydrostatic pressure and in-plane strain, providing a unified framework for understanding the experimental discrepancies between bulk and strained thin films. arXiv submission processing window: 2026-06-08 00:00 to 2026-06-08 00:00 UTC. ...

arXiv Daily: nickelate superconductors 2026-06-08

Daily Overview: Today’s highlight focuses on an in-depth discussion of the microscopic mechanism and a unified theoretical framework for superconductivity in bilayer nickelate superconductors at ambient pressure. On the experimental front, epitaxial strain engineering has successfully stabilized the high-pressure phase in La₃Ni₂O₇ thin films and induced ambient-pressure superconductivity, yet the Fermi surface topology revealed by angle-resolved photoemission spectroscopy remains controversial, possibly related to growth conditions and elemental diffusion. Pathways to enhance the transition temperature include optimizing film quality and chemical substitution with rare-earth elements. From a theoretical perspective, studies have further elucidated the spin-fluctuation enhancement mechanism driven by Fermi surface nesting, pointing out that nesting between the δ pocket and γ pocket composed of (d_{z^2}) antibonding orbitals can significantly enhance (s^\pm)-wave pairing and form a superconducting dome in the low-hole-doping region. More importantly, a unified theory based on a two-component model has been proposed. Through interlayer superexchange coupling and hybridization, it successfully explains the two distinct doping phase diagrams in pressurized bulk samples and thin films, the anomalous normal-state transport behavior, and the competition between superconductivity and the Kondo effect, and it predicts that reducing interlayer magnetic coupling can realize bulk superconductivity at ambient pressure, with the electron-doped system possibly achieving a higher transition temperature. arXiv submission processing window: times are unavailable (UTC). ...

arXiv Daily: nickelate superconductors 2026-06-04

Daily Overview: Today’s highlight focuses on deepening the understanding of the electronic structure of mixed Ruddlesden-Popper nickelates. Specifically, Ezra Day-Roberts et al. employed a combined DFT and DMFT approach to systematically compare the electronic structure, magnetism, and correlation effects of infinite-layer nickelate LaNiO₂ under electron and hole doping. They discovered a significant asymmetry: hole doping strongly suppresses the self-doping effect of the rare-earth 5d electron pockets, whereas electron doping enlarges these pockets without effectively hole-doping the Ni-d_{x²-y²} orbitals, leading to markedly different magnetic behaviors—hole doping rapidly suppresses antiferromagnetic order, while under electron doping, the antiferromagnetic state remains the ground state. Despite these pronounced differences, electronic correlations are consistently dominated by the Ni-d_{x²-y²} orbital, indicating that a single-band description can be applied to both doping scenarios. This provides a key theoretical basis for understanding nickelate superconductivity and its analogy with copper oxides. arXiv submission processing window: 2026-06-02 00:00 to 2026-06-02 00:00 UTC. ...

arXiv Daily: nickelate superconductors 2026-06-02

Daily Overview: Today’s highlight focuses on deepening the understanding of the electronic structure of mixed Ruddlesden-Popper nickelates. In [1], X-ray absorption spectroscopy systematically probed the unoccupied states of infinite-layer La₁₋ₓCaₓNiO₂, revealing that Ni–O covalency undergoes an orbital-selective crossing near the superconducting dome. This crossing coincides with the sign reversal of the Hall coefficient and the decline in superconducting critical temperature, providing key experimental evidence for establishing a unified orbitally resolved phase diagram. [2] used polarized ultrafast spectroscopy to uncover significant electronic nematicity in the normal state of bilayer La₃Ni₂O₇, while the trilayer La₄Ni₃O₁₀ exhibits isotropy, suggesting that the breaking of two-fold rotational symmetry may promote superconducting pairing in bilayer systems. [3] first-principles calculations show that the superconducting transition temperature of freestanding infinite-layer Nd₀.₈₅Sr₀.₁₅NiO₂ films increases monotonically under pressure. The physical origin lies in lattice compression increasing the Ni-3d orbital bandwidth and weakening relative electronic correlations, thereby alleviating the overly strong correlation effects induced by the low valence state of Ni. These three works elucidate the intrinsic relationship among electronic structure, correlation effects, and superconductivity in nickel-based superconductors from different perspectives. arXiv submission processing window: 2026-06-01 00:00 to 2026-06-01 00:00 UTC. ...

arXiv Daily: nickelate superconductors 2026-06-01