Thermal Relaxation of Low-Energy Excitations in Vitreous Silica

Abstract

Strong thermal-relaxation effects have been observed in vitreous silica at low temperatures on a time scale of order ${10}^{3}$ s, which are attributed to slowly relaxing low-energy excitations intrinsic to the amorphous state. With the use of a simplified version of the tunneling model, a density of states is derived for these excitations, which is comparable in magnitude to the density of the fast-relaxing excitations derived from phonon-scattering experiments.