Local fluctuations in the aging of a simple glass

TL;DR

This paper investigates the physical origin of dynamical heterogeneities in aging glasses by testing a proposed mechanism against simulations and suggesting experimental application.

Contribution

It introduces a test of a physical mechanism for dynamical heterogeneities in glasses using simulation data and proposes applying this analysis to experimental colloidal glass data.

Findings

Simulation results support the predicted universal scaling of fluctuations.

The proposed mechanism explains some features of dynamical heterogeneities.

Potential for experimental validation using confocal microscopy data.

Abstract

The presence of dynamical heterogeneities, i.e. nanometer-scale regions containing molecules rearranging cooperatively at very different rates compared to the bulk, is increasingly being recognized as crucial in our understanding of the glass transition, from the non-exponential nature of relaxation, to the divergence of the relaxation times. Recently, dynamical heterogeneities have been directly observed experimentally. However a clear physical picture for the origin of these heterogeneities is still lacking. Here we investigate a possible physical mechanism for the origin of dynamical heterogeneities in the non-equilibrium dynamics of structural glasses. We test the predictions regarding universal scaling of fluctuations derived from this mechanism against simulation results in a simple binary Lennard-Jones glass model, and find that to a first approximation they are satisfied. We also propose to apply the same kind of analysis to experimental data from confocal microscopy in colloidal glasses.