Electronic properties of highly doped trans-polyacetylene.

Abstract

The evolution of the density of states at the Fermi energy for a single chain of highly doped trans-polyacetylene is studied as a function of the dopant concentration. The studies are focused on the metallic state of the polymer, which is obtained for dopant concentrations above y\ensuremath{\sim}6%. Two types of lattice structures are considered: the soliton lattice and the polaron lattice. An effective potential due to the dopant counterions is included. The calculations are restricted to perfectly ordered samples. It is shown that the soliton lattice exhibits metallic properties only at very high doping levels. The polaron lattice is shown to exhibit a finite density of states at the Fermi energy, which in the metallic regime compares favorably with the experimental result both in magnitude and as concerns the evolution with increasing dopant concentration.