Dynamical facilitation governs glassy dynamics in suspensions of colloidal ellipsoids

Abstract

One of the greatest challenges in contemporary condensed matter physics is to ascertain whether the formation of glasses from liquids is fundamentally thermodynamic or dynamic in origin. While the thermodynamic paradigm has dominated theoretical research for decades, the purely kinetic perspective of the dynamical facilitation (DF) theory has attained prominence in recent times. In particular, recent experiments and simulations have highlighted the importance of facilitation using simple model systems composed of spherical particles. However, an overwhelming majority of liquids possess anisotropy in particle shape and interactions and it is therefore imperative to examine facilitation in complex glass-formers. Here, we apply the DF theory to systems with orientational degrees of freedom as well as anisotropic attractive interactions. By analyzing data from experiments on colloidal ellipsoids, we show that facilitation plays a pivotal role in translational as well as orientational relaxation. Further, we demonstrate that the introduction of attractive interactions leads to spatial decoupling of translational and rotational facilitation, which subsequently results in the decoupling of dynamical heterogeneities. Most strikingly, the DF theory can predict the existence of reentrant glass transitions based on the statistics of localized dynamical events, called excitations, whose duration is substantially smaller than the structural relaxation time. Our findings pave the way for systematically testing the DF approach in complex glass-formers and also establish the significance of facilitation in governing structural relaxation in supercooled liquids.

22 pages, 3 main figues, 3 supplementary figures. Submitted to Proceedings of the National Academy of Sciences, USA, on the 15th of July, 2014

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Cited by in corpus (4)

• Direct measurements of growing amorphous order and non-monotonic dynamic correlations in a colloidal glass-former
• Deconstructing the glass transition through critical experiments on colloids
• Influence of an amorphous wall on the distribution of localized excitations in a colloidal glass-forming liquid
• Transmission of mobility via cooperative mechanisms in soft active matter