Correlation between crystalline order and vitrification in colloidal monolayers

TL;DR

This study explores how local crystalline order relates to the slowing down of dynamics in a quasi-2D colloidal system, revealing that local structure influences dynamics but their characteristic lengthscales do not scale together near vitrification.

Contribution

It provides experimental evidence linking local hexagonal order to dynamical heterogeneity in colloidal monolayers, highlighting the complex relationship between structure and dynamics.

Findings

Local hexagonal regions are more dynamically slow.

Dynamic heterogeneity lengthscales do not scale with structural lengthscales.

Polydispersity suppresses crystallization while still showing structural-dynamical correlations.

Abstract

We investigate experimentally the relationship between local structure and dynamical arrest in a quasi-2d colloidal model system which approximates hard discs. We introduce polydispersity to the system to suppress crystallisation. Upon compression, the increase in structural relaxation time is accompanied by the emergence of local hexagonal symmetry. Examining the dynamical heterogeneity of the system, we identify three types of motion : "zero-dimensional" corresponding to beta-relaxation, "one-dimensional" or stringlike motion and "two-dimensional" motion. The dynamic heterogeneity is correlated with the local order, that is to say locally hexagonal regions are more likely to be dynamically slow. However we find that lengthscales corresponding to dynamic heterogeneity and local structure do not appear to scale together approaching the glass transition.