Effect of screening on the relaxation dynamics in a Coulomb glass

This paper examines the relaxation dynamics of a two-dimensional Coulomb glass lattice model with high disorder. The study aims to investigate the effects of disorder and Coulomb interactions on glassy dynamics by computing the eigenvalue distribution of the linear dynamical matrix using the mean-field approximation. The findings highlight the significance of the single-particle density of states (DOS) as the main controlling parameter affecting the relaxation at intermediate and long times. For the model with unscreened Coulomb interactions, our results indicate that the depletion of the DOS near the Fermi level leads to logarithmic decay at intermediate times. As the relaxation progresses to longer times, a power-law decay emerges, with the exponent approaching zero as the disorder strength increases, suggesting the manifestation of logarithmic decay at high disorders. The effects of screening of interactions on the dynamics are also studied at various screening and disorder strengths. The findings reveal that screening leads to the filling of the gap in the density of states, causing deviation from logarithmic decay at intermediate disorders. Moreover, in the strong disorder regime, the relaxation dynamics are dominated by disorder, and even with screened Coulomb interactions, the electronic relaxation remains similar to the unscreened case. The time at which crossover to exponential decay occurs increases with increasing disorder and interaction strength.