Interchain interaction effects on polaron–bipolaron transition on conducting polymers

Abstract

We investigate the effects of interchain interaction on the polaron–bipolaron transition on conjugated polymer. We use a Su-Schrieffer-Heeger model modified to include interchain interaction, an external electric field and electron–electron interaction via extended Hubbard terms. We study the dynamics within the time-dependent unrestricted Hartree-Fock approximation. We find that adding a hole in interacting conducting polymer chains bearing a single positively charged polaron leads to the direct transition of polaron to bipolaron state. The transition which is produced is single-polaron to bipolaron transition whose excitation spectrum explains the experimental data. The competing mechanism of two polarons merging to form a bipolaron is also observed under special circumstances. We also find that depending on how fast the hole is inserted, a structure that contains a bipolaron coupled to a breather is created. The bipolaron-breather pair can be decoupled under the action of an external electric field.