Low-frequency internal friction in silica glass

Published a new paper from N.i.P.S Laboratory: Low-frequency internal friction in silica glass, EPL 80 50008, 2007

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Low-frequency internal friction in silica glass, F. Travasso et al 2007 EPL 80 50008

F. 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

Precise low-frequency internal friction measurements on vitreous silica, taken over a wide temperature (4 K<T<300 K) and frequency range (40 Hz<f<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 the exponent, thus signalling the onset of a competing relaxation mechanism with much higher an activation energy.