2002/03/31 by V. L. Gurevich, D. A. Parshin, H. R. Schober
Physics and Astronomy · #cond-mat.dis-nn #cond-mat.stat-mech
paper · pdf · doi:10.1103/physrevb.67.094203
published as Phys. Rev. B 67, 094203 (2003) · LaTeX, 8 pages, 6 figures
arxiv created 2003/01/13 · arxiv updated 2009/11/30
We show that a \em vibrational instability of the spectrum of weakly interacting quasi-local harmonic modes creates the maximum in the inelastic scattering intensity in glasses, the Boson peak. The instability, limited by anharmonicity, causes a complete reconstruction of the vibrational density of states (DOS) below some frequency ωc, proportional to the strength of interaction. The DOS of the new \em harmonic modes is independent of the actual value of the anharmonicity. It is a universal function of frequency depending on a single parameter -- the Boson peak frequency, ωb which is a function of interaction strength. The excess of the DOS over the Debye value is ∝ω4 at low frequencies and linear in ω in the interval ωb ≪ ω≪ ωc. Our results are in an excellent agreement with recent experimental studies.