A random walk description of the heterogeneous glassy dynamics of attracting colloids

TL;DR

This study combines confocal microscopy experiments with a theoretical model to analyze the heterogeneous, non-Gaussian dynamics of attractive colloids near gel transition, revealing broad mobility distributions.

Contribution

It introduces a simple continuous time random walk model that accurately describes the broad tails in particle displacement distributions in attractive colloids.

Findings

Van Hove distributions show exponential tails, not Gaussian.

The CTRW model successfully explains the broad mobility heterogeneity.

Experimental data aligns with the theoretical predictions.

Abstract

We study the heterogeneous dynamics of attractive colloidal particles close to the gel transition using confocal microscopy experiments combined with a theoretical statistical analysis. We focus on single particle dynamics and show that the self part of the van Hove distribution function is not the Gaussian expected for a Fickian process, but that it reflects instead the existence, at any given time, of colloids with widely different mobilities. Our confocal microscopy measurements can be described well by a simple analytical model based on a conventional continuous time random walk picture, as already found in several other glassy materials. In particular, the theory successfully accounts for the presence of broad tails in the van Hove distributions that exhibit exponential, rather than Gaussian, decay at large distance.