Soft-mode dynamics model of boson peak and high frequency sound in glasses: “inelastic” Ioffe–Regel crossover and strong hybridization of excitations

Abstract

A theoretical model of the vibrational “high frequency dynamics”, including both the boson peak (BP) and high frequency sound (HFS), is proposed for a glass. The model is an elastic continuum containing acoustic vibrations interacting with soft-mode vibrational excitations. The interaction gives rise to an “inelastic” Ioffe–Regel crossover (IRC) and related strong hybridization of the two types of excitations. The spectrum of the renormalized excitations looks as if the acoustic branch is broken into two parts separated by a narrow pseudogap related to the IRC states. For these excitations, the density of states is approximately calculated in accord with the definition of the IRC, which may exhibit features similar to those of the BP and HFS.