Two-step dissociation of a polaron in conjugated polymers

We have studied the electric-field-driven motion of a polaron by solving thetime-dependent Schr"{o}dinger equation nonadiabatically and the latticeequation of motion simultaneously. It is found that the polaron mayexperience two sequent transitions under high fields; one is thetransition from the subsonic to the supersonic state, and the other from thesupersonic to dissociated state. The acoustic mode is decoupled from thecharge when the polaron moves at a speed faster than the sound speed, andthen the optical mode is decoupled at the second transition to make thepolaron dissociate completely.