Relation between Heterogeneous Frozen Regions in Supercooled Liquids and Non-Debye Spectrum in the Corresponding Glasses

• Published in: Physical review letters 2019-10, Vol.123 (15), p.155502-155502, Article 155502
• Main Authors: Paoluzzi, Matteo, Angelani, Luca, Parisi, Giorgio, Ruocco, Giancarlo
• Format: Article
• Language: English
• Subjects: Attenuation; Divergence; Excitation; Frequency spectrum; Phonons; Power law; Temperature dependence
• ISSN: 0031-9007; 1079-7114
• DOI: 10.1103/PhysRevLett.123.155502

Recent numerical studies on glassy systems provide evidence for a population of non-Goldstone modes (NGMs) in the low-frequency spectrum of the vibrational density of states D(ω). Similarly to Goldstone modes (GMs), i.e., phonons in solids, NGMs are soft low-energy excitations. However, differently from GMs, NGMs are localized excitations. Here we first show that the parental temperature T* modifies the GM/NGM ratio in D(ω). In particular, the phonon attenuation is reflected in a parental temperature dependency of the exponent s(T*) in the low-frequency power law D(ω)∼ωs(T*), with 2≤s(T*)≤4. Second, by comparing s(T*) with s(p), i.e., the same quantity obtained by pinning a p particle fraction, we suggest that s(T*) reflects the presence of dynamical heterogeneous regions of size ξ3∝p. Finally, we provide an estimate of ξ as a function of T*, finding a mild power law divergence, ξ∼(T*−Td)−α/3, with Td the dynamical crossover temperature and α falling in the range α∈[0.8,1.0].