Detection Of acoustic zone-boundary phonons by phonon difference absorption

Zusammenfassung

A new method for detection of zone-boundary phonons is reported. Phonons are detected by phonon difference absorption of far-infrared laser radiation. We present experimental results obtained for TlCl and TIBr crystals. Phonons are generated by nonradiative transitions in optically excited crystals. Our experiments indicate long-lived zone-boundary phonons at low crystal temperature and a strong decrease of the phonon lifetime with increasing temperature.