Acoustic phonon power spectra in a periodic superlattice

We consider a Green function formalism, based on the frequency distribution, to study the propagation of acoustic phonon modes in a periodic superlattice. The calculations are based on the linear response function approach, which is very convenient to deal with this kind of problem. A damping term γ is included in a phenomenological way into the wavevector expression. In order to examine the phonon excitation, we also determine, by using the fluctuation‐dissipation theorem, their power spectra, which have many interesting properties. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)