Superconductivity, pseudogap, and phase separation in topological flat bands: a quantum Monte Carlo study

TL;DR

This study uses quantum Monte Carlo simulations to explore superconductivity, pseudogap phenomena, and phase separation in a model of a topological flat band with attractive interactions, revealing insights into high-temperature superconductivity.

Contribution

It provides the first numerically exact analysis of superconductivity and competing phases in a topological flat band model with local attraction, highlighting the role of phase separation and fluctuations.

Findings

Superconductivity with a critical temperature scaling linearly with interaction strength.

Presence of a broad pseudogap regime with strong pairing fluctuations.

Introduction of nearest neighbor attraction leads to phase separation and suppresses superconductivity.

Abstract

We study a two-dimensional model of an isolated narrow topological band at partial filling with local attractive interactions. Numerically exact quantum Monte Carlo calculations show that the ground state is a superconductor with a critical temperature that scales nearly 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; introducing a small nearest neighbor attraction suppresses superconductivity entirely and results in phase separation. We discuss the possible relevance of superconductivity in this unusual regime to the physics of flat band moir\'{e} materials, and as a route to designing higher temperature superconductors.