Strong-coupling superconductivity and pseudogap in topological flat bands: a quantum Monte Carlo study

We study a two-dimensional model of an isolated narrow topological band at partial filling with local attractive interactions. Exact quantum Monte Carlo calculations show that the ground state is a superconductor with a critical temperature that scales linearly with the interaction strength. We also find a broad pseudogap regime at temperatures above the superconducting phase that exhibits strong pairing fluctuations and a tendency towards electronic phase separation. We discuss the possible relevance of superconductivity in this unusual regime to the Physics of flat band Moiré materials, and as a route to designing higher temperature superconductors.