Abstract:
A new approach to the calculation of polaron electrical conductivity by functional
integration is proposed. By means of Kubo's formula the polaron conductivity is
expressed in terms of the two-time commutator Green's function, which can be
obtained by analytic continuation of a temperature-dependent Green's function of
current-current type. This last is expressed exactly in terms of an integral over
the electron paths. The calculation of this integral in the framework of the
variational principle for the polaron free energy leads in the zeroth order to the
results of Feynman, Hellwarth, Iddings, and Platzman. Expressions are obtained
for the effective mass and the polaron lifetime at low temperatures; a comparison
with the results of other studies is made. The origin of the incorrect low-temperature dependence in the expression for the drift mobility is discussed.