The low temperature anharmonic attenuation of transverse hypersonic waves in anisotropic cubic crystals

Abstract

The low temperature attenuation of transverse hypersonic waves in cubic media due to the anharmonic interactions with thermal phonons is discussed. The effect of elastic anisotropy on the allowed three phonon processes is treated in detail. Allowed processes where transverse hypersonic waves interact with thermal phonons on the same acoustic branch of the phonon spectrum as themselves are predicted to exist. These processes are expected, however, to be very sensitive to lattice dispersion. This can cause a lower temperature dependence for the hypersonic attenuation than the T⁴ predicted for higher branch allowed processes in isotropic media by Landau and Rumer (1937).