Superconducting pairing from repulsive interactions of fermions in a flat-band system

TL;DR

This paper demonstrates that in a 1D flat-band system, repulsive interactions can induce pairing, and the addition of attractive interactions and multiple flat bands significantly enhance superconductivity, challenging traditional paradigms.

Contribution

It reveals that repulsive interactions can lead to pairing in flat-band systems and explores how attractive components and multiple bands further boost superconductivity.

Findings

Repulsive interactions induce finite pairing energy in the Creutz ladder.

Adding attractive interactions shifts the system toward superconductivity.

Multiple flat bands lead to a remarkable enhancement of superconductivity.

Abstract

Fermion systems with flat bands can boost superconductivity by enhancing the density of states at the Fermi level. We use quasiexact numerical methods to show that repulsive interactions between spinless fermions in a one-dimensional (1D) flat-band system, the Creutz ladder, give a finite pairing energy that increases with repulsion, though charge quasi-order (QO) remains dominant. Adding an attractive component shifts the balance in favor of superconductivity and the interplay of two flat bands further yields a remarkable enhancement of superconductivity, well outside of known paradigms for 1D fermions.