Phonon participation in superlattice heat capacity

Phonon spectra as well as thermodynamic characteristics of superlattices are analyzed using the method of two-time dependent Green's functions. The internal energy of the system and specific heat are determined. The temperature related behaviour of the specific heat of a superlattice is compared to specific heats of bulk structures and thin films. It has been shown that, at extremely low temperatures, superlattice and film specific heats are practically equal and considerably lower than the specific heat of bulk sample.