Dynamics of Holstein Polaron in a Chain with Thermal Fluctuations

Source abstract

Numerical modeling is used to investigate the dynamics of a polaron in a chain with small random perturbations and under the influence of a constant electric field. In the semiclassical Holstein model the region of existence of polarons in the thermodynamic equilibrium state depends not only on the temperature but also on the chain length. Therefore when we compute the dynamics from the initial polaron data, the mean displacement of the charge mass center differs, for different-length chains at the same temperature. For a large radius polaron, it is shown numerically that the “mean polaron displacement” (which takes account only of the polaron peak and its position) behaves similarly for different-length chains during the time when the polaron persists. A similar slope of the polaron displacement enables one to find the polaron mean velocity and, by analogy with the charge mobility, assess the “polaron mobility”. For a small radius polaron, simulations of the dynamics demonstrate a switching mode between an immobile polaron and a delocalized state. The position of a new polaron is not related to the position of the previous one; charge transfer occurs in the delocalized state.