Relaxation effects in disordered many-electron systems with Coulomb interaction

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Abstract
A Monte Carlo investigation of the Coulomb glass, i.e. a disordered many-electron system with long-range Coulomb interaction, is presented. By means of the Metropolis algorithm, thermodynamic properties are calculated. The relaxation of the correlation between the electronic configurations of different states visited during the random walk of the Monte Carlo procedure is quantitatively investigated. A slight modification of the algorithm allows us to determine not only the ground state but also the (nearly) complete spectrum of the low-energy excitations. A detailed analysis of the electronic configurations of these excitations shows that in most cases the ground state can only be reached by the displacement of several electrons. With this knowledge we examine the relaxation behaviour of the system by a diagonalization of the transition matrix, which comprises the transition rates between every pair of states up to a given energy. Usually a complex pattern of relevant relaxation paths has to be taken into account, comprising not only one-electron hopping but also many-electron displacements over short as well as over long distances. Consequently, several time scales are important for the overall relaxation process, typical of glassy behaviour.