Sound attenuation at terahertz frequencies and the boson peak of vitreous silica

Phys Rev Lett. 2010 May 14;104(19):195501. doi: 10.1103/PhysRevLett.104.195501. Epub 2010 May 11.


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.