Anharmonic Decay of Zone-Boundary Phonons Observed by a New Method of Phonon Detection

Abstract

A new method for detection of zone-boundary phonons is presented. Phonons generated by nonradiative transitions in thallium halide crystals are detected by phonon difference absorption with use of time-resolved far-infrared laser spectroscopy. Our experiments, performed at crystal temperatures between 3 and 20 K, give experimental evidence of strongly-temperature-dependent anharmonic lifetimes of transverse-acoustic zone-boundary phonons.