Short and long range correlated motion observed in colloidal glasses and liquids

TL;DR

This study uses confocal microscopy to analyze particle motion in dense colloidal suspensions, revealing spatially correlated dynamics that grow modestly near the glass transition, with correlations influenced by the pair correlation function.

Contribution

It provides detailed measurements of dynamic correlation lengths and their dependence on proximity to the glass transition in colloidal glasses and liquids.

Findings

Correlations decay exponentially with particle separation.

Dynamic length scale is approximately 2-3 particle diameters.

Correlations are influenced by the pair correlation function g(r).

Abstract

We use a confocal microscope to examine the motion of individual particles in a dense colloidal suspension. Close to the glass transition, particle motion is strongly spatially correlated. The correlations decay exponentially with particle separation, yielding a dynamic length scale of O(2-3 sigma) (in terms of particle diameter sigma). This length scale grows modestly as the glass transition is approached. Further, the correlated motion exhibits a strong spatial dependence on the pair correlation function g(r). Motion within glassy samples is weakly correlated, but with a larger spatial scale for this correlation.