Nonlinear conductivity of two-dimensional Coulomb glasses

TL;DR

This paper investigates the nonlinear electrical response of two-dimensional Coulomb glasses, revealing that under strong fields, the system's behavior can be described by an effective temperature and follows a Fermi-Dirac distribution.

Contribution

It introduces a Monte Carlo simulation approach to analyze nonlinear conductivity and demonstrates the emergence of an effective temperature governing the system's behavior.

Findings

Site occupancy follows a Fermi-Dirac distribution with an effective temperature.

Nonlinear conductivity resembles linear conductivity at the effective temperature.

Effective temperature relates to dissipated power through a specific mathematical expression.

Abstract

We have studied the nonlinear conductivity of two-dimensional Coulomb glasses. We have used a Monte Carlo algorithm to simulate the dynamic of the system under an applied electric field $E$. We found that in the nonlinear regime the site occupancy in the Coulomb gap follows a Fermi-Dirac distribution with an effective temperature $T_{\rm eff}$, higher than the phonon bath temperature $T$. The value of the effective temperature is compatible with that obtained for slow modes from the generalized fluctuation-dissipation theorem. The nonlinear conductivity for a given electric field and $T$ is fairly similar to the linear conductivity at the corresponding $T_{\rm eff}$. We found that the dissipated power and the effective temperature are related by an expression of the form $(T_{\rm eff}^\alpha-T^\alpha)T_{\rm eff}^{\beta-\alpha}$.