Subsonic and supersonic polarons in one-electron model of polyacetylene

Abstract

Free-moving polarons are investigated in the framework of new one-electron model of conjugated polymers. It is shown that on a dimerized lattice there exist free (in the absence of an external force like an electric field) stationary polarons, both subsonic and supersonic. Subsonic free polarons are observed in the velocity range from 0 to the speed of sound. Supersonic free polarons are observed in a limited range of velocities. There is a range of forbidden velocities between subsonic and supersonic free polarons. An analytical expression for the free polaron shape at different velocities is derived and confirmed in molecular dynamics simulations. The dynamics of subsonic and supersonic polarons in an electric field is different. It is shown that the subsonic polaron motion is not stationary and the velocity oscillations are associated with the periodic emission of tensile impulses in front of the polaron, taking away the energy received from the electric field. The supersonic polaron motion is stationary and the energy gained from the electric field is permanently transformed into oscillations behind the polaron.