Surface Vibrational Modes and Reflection Time of Phonons in a Finite-Size Superlattice.

Abstract

We discuss the interaction of bulk phonons with surface vibrational modes in a finite-size superlattice. The incident phonons injected normally on the superlattice from a substrate are perfectly reflected, i.e., the reflection ratee is unity irrespective of frequency. However, these phonons come back to the substrate with a large time delay when the frequency coincides with an eigenfrequency of the surface mode. This is due to the resonant interaction of the incident phonons with a surface vibrational mode. The results suggest that the surface vibrational modes are detectable from the other side of the surface by a time-resolved phonon reflection experiment.