Electron Hopping Conduction in the Soliton Model of Polyacetylene

It is shown that at low temperatures a novel conduction mechanism, phonon assisted hopping between soliton bound states (intersoliton hopping), may be the dominant conduction process in lightly doped polyacetylene. The theory is developed from a more general phenomenological viewpoint than previously, and the model independent aspects of the transport are stressed. It is found that the theory successfully accounts for experiments in polyacetylene which simultaneously show the hallmarks of solitons (e.g. no increase in the number of spins upon doping, a highly one-dimensional spin mobility, a qualitative dependence on cis to trans isomerization) and the characteristics of hopping transport (e.g. a strongly frequency and electric field dependent conductivity). It is further suggested that, since the theoretical considerations that lead to the conclusion that intersoliton hopping is important in polyacetylene are quite general, the same basic transport process may be important in many quasi-one dimensional semiconductors.