Dynamic facilitation observed near the colloidal glass transition

TL;DR

This study experimentally confirms dynamic facilitation in colloidal suspensions near the glass transition, showing that mobile particles promote neighboring particle mobility, especially during cage-breaking events.

Contribution

First experimental evidence of dynamic facilitation in colloidal glasses, highlighting spatial and temporal correlations in particle mobility near the glass transition.

Findings

Highly mobile particles tend to have mobile neighbors in the recent past.

Facilitation peaks at the cage-breaking relaxation time.

Dynamic heterogeneity is maximized during facilitation.

Abstract

We present experimental confirmation of dynamic facilitation in monodisperse and bidisperse colloidal suspensions near the glass transition volume fraction. Correlations in particle dynamics are seen to exist not only in space (clusters and strings) but also as bubbles in space-time. Quantitatively, highly mobile particles are more likely (than immobile particles) to have nearest neighbors that were highly mobile in immediately preceding times. The interpretation is that a particle's mobility enables or facilitates the subsequent motion of its neighbors. Facilitation is most pronounced at the relaxation time that corresponds with cage-breaking, when dynamic heterogeneity is also maximized.