Two-level model of dielectric loss in glasses

Abstract

The two-level model of a glass of Anderson, Halperin, and Varma (AHV) is applied to calculate the dielectric relaxation loss. With the AHV model the loss function tends to a constant at low frequencies in contrast to experiment. Therefore, a modification of their probability distribution is considered, which, while retaining the essential structure, takes account of the fact that the AHV probability distribution overestimates the low frequency modes and does not therefore lead to hydrodynamic behavior. This is done by a low frequency cutoff which is shown not only to restore the correct behavior of the loss function as the frequency tends to zero but also to lead to power law behavior at intermediate frequencies as observed experimentally.