Ground-state energy and effective mass of the intermediate-radius polaron in small-bandwidth polar materials.

Abstract

The ground-state properties of the dielectric polaron in small-bandwidth materials (nonadiabatic limit) are investigated in a regime intermediate between that of the small- and that of the large-radius polarons. This is done using a polaron Hamiltonian that explicitly includes the periodic potential and in which the effective-mass approximation has not been made from the beginning. A Fr\"ohlich-type electron-phonon interaction is also used. The ground-state energy is then calculated from a variational ansatz used by Emin to describe the small-polaron regime. For small bandwidth, in the nonadiabatic regime, an intermediate polaron behavior is found with a smooth transition between the small-coupling band polaron regime and the strong-coupling self-trapped state. The corresponding behavior of the effective mass is also calculated and corrections to the continuum approximation are given. The relevance of the present calculations for metal oxides is discussed.