Resonant attenuation of acoustic phonons in metallic superlattices

The attenuation rate of high-frequency sound waves (phonons) in a bulk metal was calculated by Pippard assuming the free-electron model and the deformation-potential coupling of the electron-phonon interaction. We study the correction to the Pippard theory in a metallic superlattice. A remarkable feature that we predict is the existence of the resonant absorption of the phonons by electrons. This happens due to the alteration of the band structures of electrons arising from their Brillouin-zone folding.