Intertwined Electron Pairing in the Bilayer Two-orbital Kanamori-Hubbard Model: a Unified Picture of Two Superconductivities in $\mathrm{La_3Ni_2O_7}$

TL;DR

This study uses cellular dynamical mean-field theory to reveal two intertwined s-wave superconducting states in La3Ni2O7, each with distinct origins, and highlights the role of orbital hybridization and doping in their emergence.

Contribution

It provides a unified theoretical framework explaining the coexistence of two different superconducting mechanisms in La3Ni2O7 based on a bilayer two-orbital Kanamori-Hubbard model.

Findings

Two intertwined s± wave superconductivities with distinct origins.

Superconductivity driven by Hund's coupling at low doping and hybridization at higher doping.

Comparable maximum transition temperatures for both pairing states.

Abstract

The mechanism of superconductivity in $\mathrm{La_3Ni_2O_7}$ bulk and film superconductors remains actively debated. Here, we investigate the bilayer two-orbital Kanamori-Hubbard model for $\mathrm{La_3Ni_2O_7}$ using cellular dynamical mean-field theory. We discover two intertwined $s_{\pm}-$ wave superconductivities with distinct physical origins. We show that when the $d_{z^2}$ orbital is under-doped, electron pairing associated to Hund's coupling $J_H$ prevails. As $d_{z^2}$ hole-doping $\delta_z$ increases, a second superconductivity, which is largely insensitive to $J_H$ but exhibiting a critical reliance on the $d_{z^2}$ - $d_{x^2-y^2}$ hybridization $V$, arises. These two primary pairing states exhibit comparable maximum transition temperatures $T_c$, and evolve from one to the other following a smooth $T_c$ versus $\delta_z$ relation. A stark particle-hole asymmetry is observed in the superconducting phase diagram, indicating the crucial role played by the $\gamma-$ band of $d_{z^2}$ orbital in pairing. Our results present a picture unifying the two possible pairing mechanisms in $\mathrm{La_3Ni_2O_7}$ superconductors. We discuss the implications of our findings to recent experiments.