The inertial mass tensor of a polaron in an isotropic medium

Owing to a fundamentally erroneous approach to calculations of the effectiv e polaron mass (calculations that use a model without spatial dispersion of the lattice polarizability), the polaron inertial mass has never before be en distinguished from the mass as a measure of kinetic energy. In this pape r we derive an expression for the tensor of the inertial mass of a large po laron. The tensor is found to be fully determined by two components: the lo ngitudinal component, corresponding to the case where the force acting on t he polaron is parallel to the polaron velocity, and the transverse componen t, corresponding to the case where the acceleration is perpendicular to the polaron velocity. The components of the polaron inertial mass tensor depen d quasirelativistically on the polaron velocity due to the quasirelativisti c compression of the polarization field in the direction of motion, which c onstitutes the effect of spatial dispersion of the lattice polarizability. We derive a formula that approximates the dependence of the components of t he polaron mass tensor on all the parameters: the frequency and dispersion of the phonons, the polaron velocity, and the effective dielectric constant . (C) 1999 American Institute of Physics. [S1063-7761(99)01601-7].