Low-frequency internal friction in silica glassF. Travasso1, 2, P. Amico1, 2, L. Bosi1, 2, F. Cottone1, 2, A. Dari1, 2, L. Gammaitoni1, 2, H. Vocca1, 2 and F. Marchesoni2, 3, 4
1 Dipartimento di Fisica, Università di Perugia - I-06123 Perugia, Italy
2 Istituto Nazionale di Fisica Nucleare, VIRGO Project Sezione di Perugia - I-06123 Perugia, Italy
3 Dipartimento di Fisica, Università di Camerino - I-62032 Camerino, Italy
4 Michigan Center for Theoretical Physics, The University of Michigan - Ann Arbor, MI 48109-1120, USA
received 14 May 2007; accepted in final form 9 October 2007; published December 2007
published online 31 October 2007
Precise low-frequency internal friction measurements on vitreous silica, taken over a wide temperature (4 K < T < 300 K) and frequency range (40 Hz < < 14 kHz), show remarkable similarities, but also suggestive differences with recent light scattering experiments. In the interval 30 K < T < 110 K, the exponent of the power law relaxational spectrum turns out to be proportional to T-Tk, with a minimum at around Tk = 13 K. This phenomenon is interpreted as a manifestation of thermal activation in an asymmetric double well system, the asymmetry being associated to quenched spatial disorder. For T > 160 K the loss angle develops a distinct step-like structure followed by a plateau, both independent of , thus signalling the onset of a competing relaxation mechanism with much higher an activation energy.
04.80.Nn - Gravitational wave detectors and experiments.
61.43.Fs - Glasses.
62.40.+i - Anelasticity, internal friction, stress relaxation, and mechanical resonances.
© Europhysics Letters Association 2007