Dielectric susceptibility of the Coulomb glass

We derive a microscopic expression for the dielectric susceptibility chi of a Coulomb glass, which corresponds to the definition used in classical ele ctrodynamics, the derivative of the polarization with respect to the electr ic field. The fluctuation-dissipation theorem tells us that chi is a functi on of the thermal fluctuations of the dipole moment of the system. We calcu late chi numerically for three-dimensional Coulomb glasses as a function of temperature and frequency. [S0163-1829(99)08201-6].