Anomalous detection‐energy dependence of coherent phonon in bismuth thin films

Abstract

Coherent phonons in semimetal Bi thin films have been studied by using a spectrally‐resolved pump‐probe technique. It is found that the intensity of the coherent phonon with A1g symmetry in the Bi thin film changes with the detection energy. The detection‐energy dependence of the coherent phonon intensity indicates that the phonon intensity has two peaks at the energies shifted by about twice the phonon energy from the central energy of the pulse laser. We discuss the origin of the detection‐energy dependence of the phonon intensity from the viewpoint of the generation mechanism of the coherent phonon. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)