Volume 78, Number 3, May 2007
Article Number 36001
Number of page(s) 6
Section Condensed Matter: Structural, Mechanical and Thermal Properties
Published online 16 April 2007
EPL, 78 (2007) 36001
DOI: 10.1209/0295-5075/78/36001

Dynamic-to-static crossover in the acoustic attenuation of $\chem{v\tx{-}GeO_2}$

G. Baldi1, 2, P. Benassi3, 2, L. E. Bove4, 2, S. Caponi1, 2, E. Fabiani5, D. Fioretto6, 2, A. Fontana1, 2, A. Giugni3, 2, M. Nardone3, 2, M. Sampoli7, 2 and F. Scarponi6

1  Dipartimento di Fisica, Università di Trento - 38050 Povo, Trento, Italy
2  Research Center SOFT INFM-CNR, c/o Università di Roma "La Sapienza" - 00185 Roma, Italy
3  Dipartimento di Fisica, Università di L'Aquila - 67010 Coppito, L'Aquila, Italy
4  Departement Physique des Milieux Denses CNRS-IMPMC, Universitè Paris 6 - F-75015 Paris, France
5  Universitè Joseph Fourier c/o Institut de Biologie Structurale and CRG-IN13 at Institut Laue-Langevin (ILL) - B.P. 156 Grenoble Cedex 9, France
6  Dipartimento di Fisica, Università di Perugia - 06123 Perugia, Italy
7  Dipartimento di Energetica, Università di Firenze - 50139 Firenze, Italy

received 11 September 2006; accepted in final form 15 March 2007; published May 2007
published online 16 April 2007

The acoustic attenuation of vitreous germania (v-GeO2) has been measured over more than three decades in frequency, by means of neutron scattering at high-frequency (THz), visible light scattering and the newly developed technique of Brillouin ultraviolet scattering at lower frequencies (15$\hbox{--} $50 GHz). The experiments are supported by a molecular dynamics study of a simulated sample of v-GeO2. The temperature dependence, from 80 K up to the glass transition temperature, shows a persistence of the dynamical nature of the attenuation in the GHz range and a simultaneous increase of the contribution coming from the structural disorder. At higher frequencies clear evidences of a crossover to a region where the attenuation is induced only by the topological disorder are found.

63.50.+x - Vibrational states in disordered systems.
78.35.+c - Brillouin and Rayleigh scattering; other light scattering.
61.12.Ex - Neutron scattering (including small-angle scattering).

© Europhysics Letters Association 2007