Theory of Paraelectric Resonance and Relaxation

Abstract

The theory of paraelectric resonance (PER) and relaxation is reformulated to allow a consistent treatment of dynamic lattice processes, even in the case when coupling to the lattice is strong. A simple model Hamiltonian is used and certain response functions are calculated without using perturbation theory. It is shown that the main effect of the strong lattice coupling at low temperatures is to induce a renormalization of the tunneling parameter of the paraelectric dipoles. The structure of phonon sidebands in PER is discussed. The theory predicts a strong transfer of intensity from the PER lines to the sidebands above a certain characteristic temperature. A treatment is given of paraelectric relaxation using the same techniques. A calculation of the temperature dependence of dipole-lattice relaxation time agrees well with experiment with adjustment of two parameters.