Paper

Daily Overview: Today’s highlight work focuses on the s+id mixed superconducting state induced by the synergistic effect of electronic correlations and electron-phonon coupling in infinite-layer nickelate superconductors. Investigations based on a combination of first-principles calculations and the fluctuation-exchange Migdal-Eliashberg theory reveal that spin fluctuations drive robust d-wave pairing in the Ni d_{x^2-y^2} orbital, while electron-phonon coupling induces an s-wave component in the interstitial orbitals. These two mechanisms synergistically form an s+id mixed superconducting state at a specific carrier density (e.g., n=0.9). The stability of this mixed state is highly sensitive to the local electron density. Local oxygen defects, by modulating the electron density, can create finite-sized domains with different pairing symmetries, thereby providing a microscopic explanation for the spatially inhomogeneous superconducting gap observed experimentally. These results profoundly underscore the crucial role of the synergy between correlation effects and electron-phonon coupling in determining the pairing symmetry of nickelate superconductors. arXiv submission processing window: 2026-07-15 00:00 to 2026-07-15 00:00 UTC. ...

arXiv Daily: nickelate superconductors 2026-07-15

Daily Overview: Today’s highlight focuses on the multi-dimensional advancement of pairing symmetry, thin-film property control, and high-pressure spectroscopic characterization in nickelate superconductors. Theoretical studies reveal that in pressurized La₃Ni₂O₇, correlation-driven self-energy renormalization fundamentally reshapes the pairing hierarchy: upon incorporating the dynamical mean-field self-energy, the dominant pairing symmetry reverses from the B₂g dxy state given by conventional RPA to an A₁g s± state, indicating that correctly accounting for the correlation renormalization of quasiparticles is essential for predicting the pairing symmetry of bilayer nickelates. On the experimental side, Nd₁₋ₓEuₓNiO₂ infinite-layer films grown by pulsed laser deposition exhibit a broad superconducting dome in the range 0.2 ≤ x ≤ 0.5, with an optimal superconducting transition temperature as high as about 31 K at x = 0.3, outperforming results from other vacuum epitaxy techniques, and both underdoped and overdoped regions display magnetic-field-enhanced and reentrant superconductivity induced by the polarization of Eu²⁺ local magnetic moments. Furthermore, a newly developed high-pressure soft point-contact Andreev reflection spectroscopy technique has detected, for the first time in the bilayer nickelate La₂PrNi₂O₇, a sharp zero-bias conductance peak whose evolution with temperature, magnetic field, and pressure is characteristic of unconventional superconductivity and possible d-wave pairing symmetry, thus providing direct evidence from the microscopic spectroscopic perspective for elucidating the pairing mechanism in nickelate superconductors. arXiv submission processing window: 2026-07-14 00:00 to 2026-07-14 00:00 UTC. ...

arXiv Daily: nickelate superconductors 2026-07-14

Daily Overview: Today’s highlighted work focuses on the elucidation of the electronic structure of low-n-layer tetragonal nickelates and the theoretical exploration of new electron doping strategies. One study employs the DFT+DMFT method to reveal layer-resolved correlation effects: in the undoped system, the electronic correlation of Ni-d orbitals increases with the number of layers, and the inner NiO₂ planes are generally more strongly correlated than the outer ones. Through an electron compensation strategy involving Cl substitution in the spacer layer, the nominal Ni valence is tuned to a level comparable to that of optimal superconducting systems, and it is predicted that these systems can enter a strongly correlated metallic regime, providing a feasible pathway to transform low-layer nickelates into potential superconducting candidates. Another work proposes achieving disorder-free electron doping in nickelates via a heterostructure approach: by inserting a wide-bandgap insulating LaXO₃ layer, La₂NiO₄ accepts extra electrons supplied by (LaO)⁺ layers. Many-body theoretical calculations predict that the superconducting transition temperature can exceed 50 K and even reach as high as 127 K. This method is also applicable to systems such as La₃Ni₂O₇, opening a general scheme for the comprehensive exploration of the electron doping phase diagram of nickelates. arXiv submission processing window: 2026-07-10 00:00 to 2026-07-10 00:00 UTC. ...

arXiv Daily: nickelate superconductors 2026-07-10

Daily Overview: Today’s highlighted work focuses on the structural identification of La₃Ni₂O₇ in its pressurized superconducting state. In [1], the authors employed high-pressure, variable-temperature Raman spectroscopy combined with polarization analysis to systematically track the structural evolution of La₃Ni₂O₇ single crystals under conditions down to 3 K and up to 32.7 GPa. They discovered a first-order structural phase transition from the orthorhombic Amam phase to the orthorhombic Fmmm phase at approximately 14.5 GPa, precisely where bulk superconductivity emerges. Polarization measurements further ruled out the possibility of a tetragonal I4/mmm phase, clearly establishing that the intrinsic structure of the pressurized superconducting state is orthorhombic Fmmm. This study reveals that a Ni–O–Ni bond angle of 180° is a key structural prerequisite for achieving a high superconducting transition temperature, laying an important foundation for understanding the superconducting mechanism of bilayer nickelates. arXiv submission processing window: 2026-07-08 00:00 to 2026-07-08 00:00 UTC. ...

arXiv Daily: nickelate superconductors 2026-07-08

Daily Overview: Today’s highlighted work focuses on deepening the understanding of pressure-induced structural phase transitions and oxygen-vacancy-related transport anomalies in nickelate superconductors. Synchrotron X-ray diffraction studies reveal that the bilayer nickelate La₂SmNi₂O₇ undergoes sequential monoclinic→orthorhombic→tetragonal structural transformations across the pressure range where superconductivity emerges, without the involvement of a displacive charge density wave. This provides precise constraints on bond angles and lattice parameters for the superconducting state. Transport theory work demonstrates that the sign reversal of the Hall coefficient in nickelate thin films originates from orbital-selective scattering by oxygen vacancies—in-plane oxygen vacancies strongly suppress the d_x²−y² orbital transport channel, causing the Hall coefficient to switch from negative to positive, whereas apical oxygen vacancies act in the opposite manner. This offers a microscopic picture to unify the diverse Hall responses observed experimentally as a function of oxygen stoichiometry. arXiv submission processing window: 2026-07-07 00:00 to 2026-07-07 00:00 UTC. ...

arXiv Daily: nickelate superconductors 2026-07-07