Fluctuating Phases and Fluctuating Relaxation Times in Glass Forming Liquids

TL;DR

This paper introduces a new method to extract local relaxation times and phase fields in glass-forming liquids from particle position data, revealing how fluctuations relate to dynamical heterogeneities.

Contribution

A novel technique for determining the full space and time dependent local relaxation times and phase fields from experimental or simulation data in glass-forming systems.

Findings

The phase field is well-defined when analyzing dependence on snapshot number.

Fluctuations of the phase field effectively describe long-range heterogeneities.

The method enables detailed study of dynamical heterogeneities in glass-forming liquids.

Abstract

The presence of fluctuating local relaxation times, $\tau_r(t)$ has been used for some time as a conceptual tool to describe dynamical heterogeneities in glass-forming systems. However, until now no general method is known to extract the full space and time dependent $\tau_r(t)$ from experimental or numerical data. Here we report on a new method for determining the local phase field, $\phi_r(t) = \int^{t} dt'/\tau_r(t')$ from snapshots $\{r(t_i)\}_{i=1...M}$ of the positions of the particles in a system, and we apply it to extract $\phi_r(t)$ and $\tau_r(t)$ from numerical simulations. By studying how the phase field depends on the number of snapshots, we find that it is a well defined quantity. By studying fluctuations of the phase field, we find that they describe heterogeneities well at long distance scales.