Application: Polaron-Transport

Feynman et al. (R. P. Feynman, R. W. Hellwarth, C. K. Iddings, and P. M. Platzman, Phys. Rev. 127 1004 (1962), K. K. Thornber, R. P. Feynman, Phys. Rev. B 1, 4099 (1970)), and Janssen and Zwerger (N. Janssen and W. Zwerger, Phys. Rev. B 52, 9406 (1995)) have used the influence functional theory for the non-equilibrium polaron problem, i.e. the motion of a single electron coupled to optical phonons in a crystal. The periodic crystal potential is considered in the form of an effective band-mass $m^*$, and the potential $V$ is due to an accelerating, homogeneous force in which case the expansion Eq. (7.253) becomes exact.