Quenched pair breaking by interlayer correlations as a key to superconductivity in 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 leading pairing instability, $s\pm$-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. Based on this picture, we provide a possible reason of why superconductivity emerges only under high pressure.