Non‐linear conductivity in Coulomb glasses

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 have compared results for two different models: a regular square lattice with only diagonal disorder and a random array of sites with diagonal and off‐diagonal disorder. We have found that for moderate fields the logarithm of the conductivity is proportional to$\sqrt{E}/T^2$ , reproducing experimental results. We have also found that in the nonlinear regime the site occupancy in the Coulomb gap follows a Fermi‐Dirac distribution with an effective temperature T eff higher than the phonon bath temperature T.