Berlin 2024 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 13: Glasses and Glass Transition (joint session CPP/DY)

CPP 13.1: Hauptvortrag

Montag, 18. März 2024, 16:15–16:45, H 0107

The boson peak in the vibrational spectra of glasses — •Edan Lerner — Institute for Theoretical Physics, University of Amsterdam, Science Park 904, Amsterdam, Netherlands

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. In my contribution I will provide direct numerical evidence that vibrations near the boson peak consist of hybridizations of phonons with many quasilocalized excitations; the latter have recently been shown to generically populate the low-frequency tail of the vibrational spectra of structural glasses quenched from a melt and of disordered crystals. I will next use a reanalysis of experimental data, extensive computer simulations and a mean-field model, to 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. Our results provide a unified physical picture of the low-frequency vibrational spectra of glasses, and in particular shed basic light on the origin, nature and properties of the boson peak.

Keywords: Glass; Boson peak; Vibrational Spectrum; Soft excitations