Glass transitions in two-dimensional suspensions of colloidal ellipsoids

TL;DR

This study reveals a two-step glass transition in 2D colloidal ellipsoid monolayers, showing distinct rotational and translational transitions, with cooperative particle motion and diverging cluster sizes near the transitions.

Contribution

It provides experimental evidence of separate rotational and translational glass transitions and characterizes the cooperative dynamics and clustering behavior in 2D colloidal ellipsoids.

Findings

Rotational glass transition occurs at lower density than translational.

Fast-moving particles form clusters with power-law size distributions.

Divergence of mean cluster sizes near glass transitions.

Abstract

We observed a two-step glass transition in monolayers of colloidal ellipsoids by video microscopy. The glass transition in the rotational degree of freedom was at a lower density than that in the translational degree of freedom. Between the two transitions, ellipsoids formed an orientational glass. Approaching the respective glass transitions, the rotational and translational fastest-moving particles in the supercooled liquid moved cooperatively and formed clusters with power-law size distributions. The mean cluster sizes diverge in power law as approaching the glass transitions. The clusters of translational and rotational fastest-moving ellipsoids formed mainly within pseudo-nematic domains, and around the domain boundaries, respectively.