Phonon Scattering Induced by Jahn-Teller Impurities

Abstract

Jahn-Teller (JT) impurity ions strongly coupled to the vibrational modes of the host crystal give rise to low-energy excitations (inversely proportional to the JT stabilization energy, E_JT) which are associated with the rotational motion of the lattice distortion around the ion. These excitations serve as resonant scatterers for phonons of appropriate energies as is indeed indicated by thermal conductivity or acoustic attenuation experiments. In this paper we present a theoretical study of the scattering induced by doubly degenerate JT ions at low concentration subject to strong linear coupling with a continuum of lattice modes. The Hamiltonian is /1/

$$H = \sum\limits_\gamma {\sum\limits_i {h{\omega _i}} } (1/2p_{i\gamma }^2 + q_{i\gamma }^2 + {k_i}{q_{i\gamma }}{\sigma _\gamma }),(\gamma = \theta ,\varepsilon )$$

(1)

.