Two-component Coulomb Glass in Disordered Superconducting Films

TL;DR

This paper introduces a two-component Coulomb glass model incorporating local electron-electron attraction, revealing non-universal Coulomb gaps and complex transport phenomena in disordered superconducting films.

Contribution

It proposes a novel two-component Coulomb glass model with local attraction, showing how it modifies the Coulomb gap and affects variable-range hopping transport.

Findings

Non-monotonic humps in the Coulomb gap due to local attraction.

A resistance peak as a function of local attraction strength.

Modification of the Coulomb gap from universality.

Abstract

Motivated by evidence of local electron-electron attraction in experiments on disordered insulating films, we propose a new two-component Coulomb glass model that combines strong disorder and long-range Coulomb repulsion with the additional possibility of local pockets of a short-range inter-electron attraction. This model hosts a variety of interesting phenomena, in particular a crucial modification of the Coulomb gap previously believed to be universal. Tuning the short-range interaction to be repulsive, we find non-monotonic humps in the density of states within the Coulomb gap. We further study variable-range hopping transport in such systems by extending the standard resistor network approach to include the motion of both single electrons and local pairs. In certain parameter regimes the competition between these two types of carriers results in a distinct peak in resistance as a function of the local attraction strength, which can be tuned by a magnetic field.