Superconductivity, pseudogap, and phase separation in topological flat bands

Abstract

Can superconductivity exist even if the electron kinetic energy is completely quenched, as in a flat band? This is fundamentally a nonperturbative problem, since the interaction strength is the only relevant energy scale. Here, the authors study a two-dimensional model of an isolated Chern band at partial filling with local attractive interactions. Their quantum Monte Carlo calculations demonstrate unambiguously that the ground state is a superconductor, emerging from an incoherent Cooper-pair liquid at temperatures above a critical temperature. Strikingly, the latter scales almost linearly with the interaction strength.