Phonon participation in superlattice heat transport

Phonon spectra as well as thermodynamic characteristics of superlattices are analyzed using the method of two-time temperature Green's functions. The phonon dispersion law is found in "cut-off" case. Internal energy of the system, as well as specific heat and coefficient of thermal conductivity are determined. The temperature dependence coefficient of thermal conductivity of a superlattice is compared to ones of bulk structures and thin films. It has been shown that, at extremely low temperatures, superlattice and film coefficient of thermal conductivity are practically equal and in the same time considerably lower than the specific heat of bulk sample.