The inertial mass tensor of a polaron in an isotropic medium

Owing to a funadmentally erroneous approach to calculations of the effective polaron mass (calculations that use a model without spatial dispersion of the lattice polarizability), the polaron inertial mass has never before been distinguished from the mass as a measure of kinetic energy. In this paper we derive an expression for the tensor of the inertial mass of a large polaron. The tensor is found to be fully determined by two components: the longitudinal component, corresponding to the case where the force acting on the polaron is parallel to the polaron velocity, and the transverse component, corresponding to the case where the acceleration is perpendicular to the polaron velocity. The components of the polaron inertial mass tensor depend quasirelativistically on the polaron velocity due to the quasirelativistic compression of the polarization field in the direction of motion, which constitutes the effect of spatial dispersion of the lattice polarizability. We derive a formula that approximates the dependence of the components of the polaron mass tensor on all the parameters: the frequency and dispersion of the phonons, the polaron velocity, and the effective dielectric constant. Zh. éksp. Teor. Fiz. 115, 180–186 (January 1999)