Persistently Non-Gaussian Metastable Liquids

TL;DR

This paper investigates the persistent non-Gaussian behavior of particle dynamics in dense, metastable liquids, revealing universal large deviations across various glassy systems driven by different fluctuations.

Contribution

It uncovers the universal presence of non-Gaussian tails in particle motion within metastable liquids, regardless of the type of driving fluctuations, highlighting fundamental dynamical features.

Findings

Non-Gaussian tails persist over multiple decades in time.

Particle dynamics are universally affected by large deviations.

Non-ergodic and non-time-reversal symmetric behaviors are observed.

Abstract

Particles undergoing Fickian diffusion within smooth energy landscapes exhibit Gaussian statistics. However, this Gaussian behavior is often elusive in complex liquids, where particle dynamics within spontaneously fluctuating or spatio-temporally heterogeneous environments lead to a breakdown of ergodicity and time-reversal symmetry. This is usually caused by extreme particle movements or sudden dynamical arrest. Such situations are prevalent in dense metastable liquids exhibiting slow flow or cooperative movements, facilitated by cage-breaking. We investigate the dynamics of glassy systems driven by either thermal, external, or environmental fluctuations. Despite their differences, our findings reveal that particle motion is universally affected by large deviations, resulting in non-Gaussian tails persisting over multiple decades in time. We further discuss the underlying dynamical aspects.