Thermodynamics and excitations of Coulomb glass

Abstract

We have calculated the phase diagram and density of states of single-particle excitations of a lattice model of the Coulomb glass. We employ the replica method to average over disorder and then use linked-cluster expansion to obtain the free energy in the random phase approximation. We find that the system has a transition to an antiferromagnetic phase below a critical disorder. Above the critical disorder, the system has a glassy ``independent spin phase'' at zero temperature which crosses over to paramagnetic phase as the temperature is increased. In the antiferromagnetic phase, the single-particle excitation density [density of states (DOS)] has a feature including the gap at the Fermi level due to long-range order. To obtain DOS in the glassy phase, we analyze cavity-field equations for local magnetization (occupation). We obtain DOS at nonzero temperatures and find that with temperature the DOS at the Fermi level increases quadratically and the Coulomb gap decreases linearly.