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 < ν < 14 kHz), show remarkable similarities, but also suggestive differences with recent light-scattering experiments. In the interval 30 K < T < 110 K, the exponent α ( 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.