Universality of ac conduction in disordered solids
Abstract
The striking similarity of ac conduction in quite different disordered solids is discussed in terms of experimental results, modeling, and computer simulations. After giving an overview of experiment, a macroscopic and a microscopic model are reviewed. For both models the normalized ac conductivity as a function of a suitably scaled frequency becomes independent of details of the disorder in the extreme disorder limit, i.e., when the local randomly varying mobilities cover many orders of magnitude. The two universal ac conductivities are similar, but not identical; both are examples of unusual nonpowerlaw universalities. It is argued that ac universality reflects an underlying percolation determining dc as well as ac conductivity in the extreme disorder limit. Three analytical approximations to the universal ac conductivities are presented and compared to computer simulations. Finally, model predictions are briefly compared to experiment.
 Publication:

Reviews of Modern Physics
 Pub Date:
 July 2000
 DOI:
 10.1103/RevModPhys.72.873
 Bibcode:
 2000RvMP...72..873D
 Keywords:

 72.10.Bg;
 01.30.Rr;
 72.10.Bg;
 01.30.Rr;
 General formulation of transport theory;
 Surveys and tutorial papers;
 resource letters;
 General formulation of transport theory;
 Surveys and tutorial papers;
 resource letters