Low-frequency losses in silica glass at low temperature

Precise low-frequency internal friction measurements on vitreous silica, taken over a wide temperature (4 K < T < 300 K) and frequency range (40 Hz < nu < 14 kHz), show remarkable similarities, but also suggestive differences with recent light-scattering experiments. In the interval 30 K < T < 110 K, the exponent alpha(T) of the power-law relaxational spectrum at low frequencies turns out to be proportional to T - T-k, with a minimum at around T-k = 13 K. This phenomenon is interpreted as a manifestation of quenched spatial disorder. (C) 2009 Elsevier B.V. All rights reserved.