SOLITON DIFFUSION IN POLYACETYLENE

Abstract

Making use of the Su, Schrieffer and Heeger (SSH) model for polyacetylene, we study theoretically the soliton difusion in pristine trans-(CH)x. The soliton in the SSH model couples linearly both optical and acoustic phonons. Since the coupling to the optical phonon is stronger, the optical phonon dominates the soliton diffusion in high temperature (T>400K). However, below the room temperature the acoustic phonon dominates the soliton diffusion. For temperature T>To≡2mc2, where m is the soliton mass and c is the acoustic phonon velocity, the soliton relaxation is determined by the single phonon process. This process results in the diffusion constant DαT1/2(2-d), where d is the dimensionality of the acoustic phonon. For T