Universal Density of Low Frequency States in Amorphous Solids at Finite Temperatures

TL;DR

This paper demonstrates that amorphous solids at finite temperatures still exhibit a universal low-frequency vibrational density of states, similar to the zero-temperature case, provided the structure is stabilized before thermal diffusion occurs.

Contribution

It extends the known zero-temperature universal density of states in amorphous solids to finite temperatures, showing stability of this property up to T_g/3.

Findings

Universal density of states persists at finite temperatures

Stability of average particle positions is crucial

Universal law applies around thermally averaged configurations

Abstract

It has been established that the low frequency quasi-localized modes of amorphous solids at zero temperature exhibit universal density of states, depending on the frequencies as $D(\omega) \sim \omega^4$. It remains an open question whether this universal law extends to finite temperatures. In this Letter we show that well quenched model glasses at temperatures as high as $T_g/3$ possess the same universal density of states. The only condition required is that {\em average} particle positions stabilize before thermal diffusion destroys the cage structure of the material. The universal density of quasi-localized low frequency modes refers then to vibrations around the thermally averaged configuration of the material.