ac conductivity of a Coulomb glass from computer simulations

A method for calculating the photon-induced hopping ac conductivity of a Coulomb glass by computer simulation is proposed. Results obtained by using an effective relaxation algorithm for two three-dimensional models of a Coulomb glass are reported. The ac conductance data clearly demonstrate the transition from super-linear to a sub-quadratic power law. We argue that the same qualitative behavior should be expected for compensated semiconductors. It is shown that the transition is driven by the Coulomb energy of sites forming resonant pairs and not by the width of the Coulomb gap. \begin{thebibliography}{99} \bibitem{} S. A. Basylko, V. A. Onischouk, and A. Rosengren, Phys. Rev. B {\bf 70}, 024201 (2004). \end{thebibliography}