Thermal conductivity due to two-component gas of thermal excitations

Abstract

The effective thermal conductivity of a continuous medium containing a two-component gas of thermal excitations and scattering centers is calculated. The result is valid for any relation between the times of interactions of various thermal excitations with one another and with scattering centers. It is shown that, in addition to partial and flow contributions, the effective thermal conductivity also contains a component associated with diffusion of thermal excitation gas. The obtained expressions, which are valid for any energy–momentum relation, are used for calculating effective thermal conductivities due to thermal excitations of solids and quantum liquids, such as longitudinal and transverse phonons, phonons and magnons, and phonons and rotons. Proceeding from universal relations, the limiting cases of rapid and slow stabilization of equilibrium between thermal excitations of different types in the systems under investigation are considered. This makes it possible to refine the results obtained by other authors and to determine the region of their applicability.