Fluctuating Mobility Generation and Transport in Glasses

TL;DR

This paper develops a theoretical model combining mode coupling theory and activated events to describe how mobility propagates in glasses during aging and rejuvenation, matching experimental observations.

Contribution

It introduces a fluctuating dynamical equations framework that captures mobility generation and facilitation effects in glasses, extending existing theories.

Findings

Mobility fronts propagate from the surface during rejuvenation.

The front speed aligns with experimental measurements.

The model explains surface-initiated melting in glasses.

Abstract

In the context of the random first order transition theory we use an extended mode coupling theory of the glass transition that includes activated events to account for spatiotemporal structures in aging and rejuvenating glasses. We numerically solve fluctuating dynamical equations for mobility and fictive temperature fields which capture both mobility generation through activated events and facilitation effects. Upon rejuvenating, a source of high mobility at a glass surface initiates a growth front of mobility which propagates into the unstable low mobility region. The speed of the front is consistent with experiments on the rejuvenation of stable glasses, which "melt" from their surface.