Single particle fluctuations and directional correlations in driven hard sphere glasses

TL;DR

This study uses simulations and experiments to analyze how shear rate and packing fraction influence particle fluctuations and correlations in hard sphere glasses, revealing complex behaviors driven by shear and thermal effects.

Contribution

It provides new insights into the interplay of shear, packing, and thermal fluctuations affecting particle dynamics and correlations in glassy systems.

Findings

Correlations increase as shear rate decreases above the glass transition.

Exponential tail broadening occurs with decreasing packing fraction, despite decreasing heterogeneity.

Anisotropy of dynamic correlations is addressed in the context of shear effects.

Abstract

Via event driven molecular dynamics simulations and experiments, we study the packing fraction and shear-rate dependence of single particle fluctuations and dynamic correlations in hard sphere glasses under shear. At packing fractions above the glass transition, correlations increase as shear rate decreases: the exponential tail in the distribution of single particle jumps broadens and dynamic four-point correlations increase. Interestingly, however, upon decreasing the packing fraction, a broadening of the exponential tail is also observed, while dynamic heterogeneity is shown to decrease. An explanation for this behavior is proposed in terms of a competition between shear and thermal fluctuations. Building upon our previous studies [Chikkadi et al, Europhys. Lett. (2012)], we further address the issue of anisotropy of the dynamic correlations.