Effective model and pairing tendency in the bilayer Ni-based superconductor La3Ni2O7

Abstract

Since the discovery of cuprates, the origin of high-Tc superconductivity has been an outstanding puzzle. Recently, high-Tc superconductivity was observed in a bilayer nickelate La3Ni2O7 under pressure, whose structure hosts the apical oxygen between two layers, distinct from multilayer cuprates. Motivated by this discovery, we investigate its electronic structure using first-principles calculations and superconducting instabilities from both weak-coupling and strong-coupling perspective. Based on the first-principles band structures, we construct a bilayer two-orbital model on a square lattice, consisting of dx2−y2 and dz2 orbitals, which accurately captures the low-energy electronic properties. Within this model, we study pairing instability using both functional renormalization group approach and multiorbital t−J model. An s±-wave pairing with sign-reversal gaps on different Fermi surfaces is revealed, reminiscent of iron-based superconductors. The Ni-dz2 orbital and its associated interlayer and intralayer exchange couplings are found to be crucial for the high-Tc superconductivity. Our study provides valuable insights into the unique nature of electronic structure and superconductivity in La3Ni2O7 and contributes to the understanding of unconventional superconductivity.

Source-reported materials — not catalogue approval

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