Critical role of interlayer dimer correlations in the superconductivity of La$_3$Ni$_2$O$_7$

Abstract

The recent discovery of superconductivity in La$_3$Ni$_2$O$_7$ with $T_\mathrm{c} \simeq 80~\mathrm{K}$ under high pressure opens up a new route to high-$T_\mathrm{c}$ superconductivity. This material realizes a bilayer square lattice model featuring a strong interlayer hybridization unlike many unconventional superconductors. A key question in this regard concerns how electronic correlations driven by the interlayer hybridization affect the low-energy electronic structure and the concomitant superconductivity. Here, we demonstrate using a cluster dynamical mean-field theory that the interlayer electronic correlations (IECs) induce a Lifshitz transition resulting in a change of Fermi surface topology. By solving an appropriate gap equation, we further show that the dominant pairing instability (intraorbital $s$-wave/interorbital $d_{x^2-y^2}$-wave) is enhanced by the IECs. The underlying mechanism is the quenching of a strong ferromagnetic channel, resulting from the Lifshitz transition driven by the IECs. Our finding establishes the role of IECs in La$_3$Ni$_2$O$_7$ and potentially paves the way to designing higher-\Tc nickelates