Sound attenuation at terahertz frequencies and the boson peak of vitreous silica.
The propagation and damping of the acoustic excitations in vitreous silica is measured at terahertz frequencies using inelastic x-ray scattering. The apparent sound velocity shows a marked dispersion with frequency while the sound attenuation undergoes a crossover from a fourth to a second power law frequency dependence. This finding solves a recent controversy concerning the location of this crossover in vitreous silica, clarifying that it occurs at the position of the glass-characteristic excess of vibrational modes known as boson peak, and thus establishing a direct connection between boson peak and acoustic dispersion curves.
Baldi
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European Synchrotron Radiation Facility, BP220, 38043 Grenoble, France. giacomo.baldi@esrf.fr
Giordano
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Monaco
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Ruta
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