Universal temperature dependence of the thermal conductivity of clathrate compounds, molecular crystals, and glasses at low temperatures

Abstract

A new approach is used to analyze the experimental data on the temperature dependence of low-temperature thermal conductivity κ(T) of some typical disordered complex crystals: clathrate hydrates (tetrahydrofuran, methane, xenon), Sr8Ga16Ge30 and p-type Ba8Ga16Ge30 clathrate compounds, YSZ ceramics, molecular structural glasses of 1-propanol, glycerol and D-ethanol exhibiting glass-like behavior of κ(T), and some representatives of regular complex crystals: tetrahydrofuran clathrate hydrate, n-type Ba8Ga16Ge30 clathrate compound, CsDy(MoO4)2 layered crystal, 1-propanol, and D-ethanol. A universal approach to normalizing low-temperature thermal conductivity is proposed, based on the theoretical model of hybridized Klinger-Kosevich excitations. The low-temperature universal behavior of the thermal conductivity of both crystalline and amorphous solids is shown to be a result of the same phenomenon: the hybridization of acoustic and low-lying optical branches.