Evaluation of the electron-TO-phonon interaction in polar crystals from experimental data

The aim of this study was to determine the strengths of the coupling of electrons with the polar long-wavelength transverse optical (TO) vibrations from infrared spectroscopy data. This determination is made by means of a simple relationship between the electron-TO-phonon interaction constant and material parameters, based on a parametrization of the electron-TO-phonon coupling in terms of the long-range dipole-dipole interaction. The combination of experimental data employed here allowed us to calculate directly the relevant constants for a number of representative polar insulators and to show that in ferroelectrics the interband electron-TO-phonon interaction at the Γ point is essentially strong. In these calculations, infrared spectroscopy methods proved to be an effective tool for study of the main properties of electron interaction with polar long-wavelength TO phonons.