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

Abstract: The mechanism of pairing 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 find two intertwined $s_{\pm}$-wave superconductivities with distinct physical origins under enhanced Hund's coupling $J_H$. We show that when $d_{z^2}$ orbital is half-filled and its bonding band lies below Fermi level, electron pairing associated to $J_H$ prevails. As $d_{z^2}$ orbital is hole-doped, this superconducting state becomes suppressed and a second superconductivity, which is largely insensitive to $J_H$ but exhibiting a critical reliance on $d_{z^2}$ - $d_{x^2-y^2}$ hybridization $V$, arises. These two pairing states exhibit comparable maximum transition temperatures and evolve continuously from one to the other with varying $d_{z^2}$ doping, resulting a smooth $T_c$ versus doping evolution. The dependence on various physical parameters of the two superconductivities is studied. Our results present a unified picture reconciling the debate about the role of $d_{z^2}$ orbital in pairing. We discuss the relevance of our results to recent experiments on superconducting $\mathrm{La_3Ni_2O_7}$ films.