A unified picture of phonon anomalies in crystals and glasses

Abstract

Phonon spectra in solids often display anomalies that defy the simple Debye law, most prominently the van Hove singularity in crystals and the boson peak in glasses. Although traditionally regarded as distinct, both features are increasingly recognized as sharing a common physical origin. In a recent work, G. Ding et al. (Nat. Phys. 2025) propose a resonant-damping model that unifies these anomalies within a single framework. By coupling phonon damping to vibrational softening, their theory explains why some materials exhibit van Hove peaks, others boson peaks, and many show both. This advance extends earlier ideas and theories of Baggioli and Zaccone on the competition between phonon propagation and damping, while also connecting to microscopic mechanisms such as nonaffine motions in glasses. The resonant-damping paradigm thus offers a promising step toward a unified understanding of vibrational anomalies across ordered and disordered solids.

Figures (1)

• Figure 1: (Color online) Unified picture of vibrational anomalies. Left: phonon damping functions derived from resonant scattering reproduce both Rayleigh-like ($\Gamma \propto q^4$) behavior at low wavevectors and resonant softening at higher $q$, consistent with data from glasses and crystals. Right: the resulting vibrational density of states (VDOS) explains boson peaks in glasses (silica, blue) and van Hove-like features in high-entropy alloys (FeCoCrNi HEA, green), in comparison with the Debye model. Adapted from Ding et al.Ding2025.