Coulomb gap in disordered systems

Abstract

The properties of low-energy excitations in a disordered system with localized electrons are discussed. A simple model and a self-consistent method for the calculation of the density of states are proposed. It is argued that in a three-dimensional system there are in fact no low-energy one-particle excitations, but many-particle charged excitations exist and determine the d.c. conductivity of the system. Formulae are given for the density of states of such excitations and for the d.c. conductivity.