Hund's rule, interorbital hybridization, and high-Tc superconductivity in the bilayer nickelate La3Ni2O7

Abstract

Understanding the pairing mechanism in bilayer nickelate superconductors constitutes a fascinating quest. Here we investigate the intriguing interplay between Hund's rule coupling and interorbital hybridization in a two-orbital model for bilayer nickelates, using a comprehensive tensor network approach: density matrix renormalization group for finite-size systems, infinite projected entangled-pair states in the thermodynamic limit, and thermal tensor networks for finite-temperature properties. We explain the pressure-dependent high-Tc superconductivity observed in experiments by identifying three distinct superconductive (SC) regimes: hybridization dominant, Hund's rule dominant, and the hybrid-Hund synergistic SC regimes. In these SC regimes, both dx2−y2 and dz2 orbitals exhibit algebraic pairing correlations with similar Luttinger parameters KSC. However, the former exhibits a much stronger amplitude than the latter, with a distinctly higher SC characteristic temperature Tc*, below which the pairing susceptibility diverges as χSC(T)∼1/T2−KSC. With realistic model parameters, we find the pressurized La3Ni2O7 falls into the Hund's rule dominated SC regime. As hybridization further enhances with pressure, it leads to significant interorbital frustration and in turn suppresses the SC correlations, explaining the rise and fall of high-Tc superconductivity under high pressure. Our results offer a comprehensive understanding of the interlayer pairing in superconducting La3Ni2O7.

Source-reported materials — not catalogue approval

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