Effects of Attractive correlation on Topological Flat-bands Model

TL;DR

This paper investigates how attractive electron correlations influence topological flat-band insulators, revealing a quantum phase transition to a superconducting state driven by increasing attractive interactions.

Contribution

It introduces an extended attractive Kane-Mele-Hubbard model to study the impact of attractive correlations on topological insulators with flat bands, highlighting a novel phase transition.

Findings

Identified a quantum phase transition from topological insulator to superconductor with increasing attraction.

Discovered Cooperon-type gapped excitations near the transition on the TI side.

Showed the transition differs from traditional Fermi liquid-based superconductivity.

Abstract

In this paper, we study the effects of attractive correlation on the topological insulator ($TI$) with topological flat-bands using an extended attractive Kane-Mele-Hubbard model (KMHM). In the KMHM, we found a quantum phase transition from $TI$ to the superconductor ($SC$) state upon the increasing of the attractive Hubbard interaction $U$ at the mean field level. This type of $SC$ phase transition is different from the traditional $SC$ phase transition which develops from the gapless Fermi Liquid. Cooperon-type gapped excitations exist in the $TI$ side near this type of $SC$ phase transition.