Journal of Statistical Physics, Vol. 65, Nos. 1/2, 1991, p. 317-361.
This work deals with the quantum dynamics of a narrow-band particle
interacting with phonons and static disorder. The present theory is exact in the
limit of small bandwidth compared with the Debye energy, and covers various
regimes in the parameter space of temperature and disorder strength. Therefore,
the theory provides a unified framework for studying when and how the particle
motion changes from coherent bandlike behavior to incoherent hopping as the
temperature and/or disorder strength are increased. The theory also includes
the double-well problem as a special case, where rather complete description of
the particle motion is obtained.