EFFECTS OF INTERCHAIN INTERACTIONS ON THE ELECTRONIC-STRUCTURE OF HEAVILY-DOPED TRANSPOLYACETYLENE

The effects of interchain interactions on the geometrical and electronic structure of heavily doped trans-polyacetylene are studied in detail. The interchain interactions include electron hopping, electron-electron repulsion, and the potential due to counterions associated with neighboring chains. The optimized geometry corresponds to that of a soliton lattice for dopant concentration up to 12.5%, which is the highest concentration included in this study. The interchain interactions reduce the energy gap around the Fermi energy considerably. A sharp transition into a metallic state is observed at dopant concentrations around 9%. The metallic state is understood from the fact that the optimized dimerization amplitude is small in the case of a strongly interacting soliton lattice. In this situation, the Peierls gap is of the same magnitude as the broadening of the energy bands due to interchain interactions. The effects of disorder on the electronic structure are also discussed. Three-dimensional delocalization of the electronic states is observed for realistic values of the interchain-hopping strength.