Daily Overview: Today’s highlights focus on an in-depth understanding of the electronic structure of mixed Ruddlesden-Popper nickelates. In [1], first-principles simulations reveal a precise correspondence between the enhancement of electronic correlation strength driven by structural phase transitions and the superconducting dome in La₃Ni₂O₇, clarifying the key role of A-site cations in the pressure-tuned evolution of correlations. In [2], random phase approximation analysis from an itinerant electron perspective shows that the strength of Hund’s coupling determines the competition between superconducting pairing symmetry (s-wave or d-wave) and magnetic ordering wave vectors ((π/2, π/2) or (π, π)) in the bilayer nickelate system, providing crucial theoretical support for understanding the unconventional mechanism of nickelate superconductivity. arXiv submission processing window: 2026-02-25 00:00 to 2026-02-25 00:00 UTC.

1. First-Principles Evidence for Strongly Correlated Superconductivity Driven by Structural Variations in La$_3$Ni$_2$O$_7$

Summary: This study systematically analyzes the electronic correlation behavior of La₃Ni₂O₇ within the superconducting pressure range using first-principles simulations combined with constrained random phase approximation and ab initio molecular dynamics. The results show that, accompanying the structural phase transition, the effective on-site repulsion of Ni e_g orbitals is significantly enhanced, attributed to the dynamic balance between orbital localization and competing screening channels, particularly the spacer-layer La bands. This enhancement region aligns remarkably well with the experimentally observed right-triangular superconducting dome, reaching a peak correlation strength at 18 GPa that corresponds to the highest superconducting critical temperature. Finite-temperature simulations further clarify the boundaries of the structural phase diagram, while calculations on Ac₃Ni₂O₇ confirm the critical role of A-site cations in the pressure-driven evolution of electronic correlations. These findings directly reveal how structural changes drive unconventional superconductivity by modulating the strength of electronic correlations.

2. Superconductivity and magnetism in bilayer nickelates: itinerant perspective

Summary: This study systematically explores superconductivity and magnetism in bilayer nickelates from the perspective of itinerant electrons. Based on recent angle-resolved photoemission spectroscopy measurements on compressively strained thin films, the researchers constructed a model via tight-binding fitting and introduced standard local repulsive interactions among partially filled eg orbitals: intraorbital Coulomb interaction U, interorbital Coulomb interaction U′, Hund’s coupling JH, and pair hopping JP. Using the random phase approximation, the bare interactions are renormalized through particle-hole fluctuations to obtain effective pairing interactions. The results show that in the strong Hund’s coupling regime, s-wave superconductivity and (π/2, π/2) spin density wave are stable ground states, while in the weak Hund’s coupling regime, d-wave pairing and (π, π) spin density wave dominate as the ground states. These findings are qualitatively consistent with previous density matrix renormalization group studies, highlighting the crucial role of Hund’s coupling in determining the superconducting pairing symmetry and magnetic wave vector in this system.