The boson peak in the vibrational spectra of glasses

Abstract

A hallmark of glasses is an excess of low-frequency, nonphononic vibrations, in addition to phonons. It is associated with the intrinsically nonequilibrium and disordered nature of glasses, and is generically manifested as a THz peak -- the boson peak -- in the ratio of the vibrational density of state (VDoS) and Debye's VDoS of phonons. Yet, the excess vibrations and the boson peak are not fully understood. Here, using reanalysis of experimental data, extensive computer simulations and a mean-field model, we show that the nonphononic part of the VDoS itself features both a universal power-law tail and a peak, entirely accounted for by quasi-localized nonphononic vibrations, whose existence was recently established. We explain the mild variation of the peak's frequency and magnitude with glasses' thermal history, along with the strong variation of the power-law tail. We also show that modes that populate the peak's region feature many coupled quasi-localized nonphononic vibrations, when their spatial structure is considered. Our results provide a unified physical picture of the low-frequency vibrational spectra of glasses, and in particular elucidate the origin, nature and properties of the boson peak.

6 pages and 4 figures + Supplementary Materials

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Cited by in corpus (12)

• Boson-peak vibrational modes in glasses feature hybridized phononic and quasilocalized excitations
• Stringlet Excitation Model of the Boson Peak
• Experimental evidence for the ${\omega }^4$ tail of the nonphononic spectra of glasses
• Testing the Heterogeneous-Elasticity Theory for low-energy excitations in structural glasses
• Revealing the Geometrical and Vibrational Properties of the Defects Driving the Boson Peak
• Enumerating low-frequency nonphononic vibrations in computer glasses
• A fresh look at the vibrational and thermodynamic properties of liquids within the soft potential model
• Unified study of viscoelasticity and sound damping in hard and soft amorphous solids
• Yielding and memory in a driven mean-field model of glasses
• Impact of elastic inhomogeneity on collective dynamical properties investigated by field theoretical description in real space
• Spotting structural defects in crystals from the topology of vibrational modes
• Resonant Coupling and the Non-Phononic Flat Band in Amorphous Solids