Resonant scattering and thermal transport in orientational glasses

Abstract

In the orientational glass KBr:KCN, we provide a natural explanation for the plateau in the thermal conductivity, which is a universal feature of all amorphous insulators. We show that the angular oscillation modes of the CN ions have a sharply peaked density of states in the THz range. These modes, in addition to contributing to the specific heat, resonantly scatter the thermal phonons in the plateau region. We discuss the possibility of localization of phonons in a narrow band due to this strong scattering. We speculate about the applicability of these ideas to structural glasses.