Interlayer valence bonds and two-component theory for high- Tc superconductivity of La3Ni2 O7 under pressure

Abstract

The recent discovery of high-Tc superconductivity in bilayer nickelate La3Ni2O7 under high pressure has stimulated great interest concerning its pairing mechanism. We argue that the weak coupling model from the almost fully filled dz2 bonding band cannot give rise to its high Tc, and thus propose a strong coupling model based on local interlayer spin singlets of Ni-dz2 electrons due to their strong on-site Coulomb repulsion. This leads to a minimal effective model that contains local pairing of dz2 electrons and a considerable hybridization with near quarter-filled itinerant dx2-y2 electrons on nearest-neighbor sites. Their strong coupling provides a unique two-component scenario to achieve high-Tc superconductivity. Our theory highlights the importance of the bilayer structure of superconducting La3Ni2O7 and points out a potential route for the exploration of more high-Tc superconductors.