Inhomogeneous Insulator-Metal Transition in Conducting Polymers

A review of recent work on the insulator-metal transition (IMT) in conducting polymers is presented. The temperature dependence of the dielectric function [ε(ω)] of highly conducting polyaniline and polypyrrole, which cross the IMT as probed by δDC(T), has been measured over an unusually broad range of frequencies (6.5 GHz and 2 meV− 6 eV). These data demonstrate that the inhomogeneous disorder model is a more appropriate description for the IMT than the homogeneous three-dimensional Anderson model.