Charge glass in two-dimensional arrays of capacitively coupled grains with random offset charges

TL;DR

This paper investigates how random offset charges affect the insulator-conductor transition in 2D arrays of capacitively coupled grains, revealing disorder-induced suppression of charge order and the emergence of a charge glass phase.

Contribution

It introduces a detailed analysis of the impact of disorder on charge glass formation and conduction in 2D Josephson junction arrays, supported by Monte Carlo simulations and experimental consistency.

Findings

Disorder destroys charge ordering at finite temperatures in the thermodynamic limit.

Conductance remains linear and thermally activated, with nonlinear effects at a decreasing crossover voltage.

Large disorder leads to behavior consistent with a charge glass phase and experimental observations.

Abstract

We study the effect of random offset charges in the insulator to conductor transition in systems of capacitively coupled grains, as realized in two-dimensional arrays of ultrasmall Josephson junctions. In presence of disorder, the conductive transition and charge ordering at nonzero gate voltages are both destroyed for any degree of disorder $\sigma$ at finite temperatures $T$, in the thermodynamic limit, but crossover effects will dominate at length scales smaller than $\xi_{\sigma, T}=T^{-\nu} f(\sigma T^{-\nu})$, where $\nu $ is the thermal critical exponent of the zero-temperature charge glass transition. The conductance is linear and thermally activated but nonlinear behavior sets in at a crossover voltage which decreases as temperature decreases. For large disorder, the results are supported by Monte Carlo dynamics simulations of a Coulomb gas with offset charges and are consistent with the thermally activated behavior found in recent experiments.