Dynamics of disordered dipolar systems

Abstract

The electrical response of defect centres, which are distributed randomly in space and interact via electrostatic forces, is examined by Monte Carlo simulation of dipolar lattice gas models. Coulomb interactions are found to have a profound influence on the a.c. conductivity or the dielectric loss spectrum, when the interaction strength becomes comparable to or exceeds the thermal energy. In that case we observe “nearly constant loss behaviour” in an intermediate frequency range, known as a universal phenomenon in disordered materials. For the same model we describe a dynamic pair approximation which qualitatively reproduces the simulated spectra. Our results suggest reconsideration of the question of consistency of the “asymmetric double well potential (ADWP)” model in attempts to interpret constant loss spectra measured at low temperature.