Decay cascades of acoustic phonons in calcium fluoride

Abstract

The temporal evolution of a spatially homogeneous non-equilibrium distribution of non-dispersive acoustic phonons is investigated for small occupation numbers in the presence of impurities as incoherent elastic scatterers. The phonon-phonon interaction governing the spontaneous decay via cubic anharmonicity is accounted for quantitatively on the basis of non-linear elasticity theory. The theoretical results are compared with the experimental data of Happek er al.