Translational Dynamics of Rod-like Particles in Supercooled Liquids: Probing Dynamic Heterogeneity and Amorphous Order

TL;DR

This paper demonstrates how the translational dynamics of rod-like probe particles in supercooled liquids can reveal the growth of dynamic heterogeneity and static correlations, providing a new experimental approach to study glassy systems.

Contribution

It introduces a unified scaling theory linking probe dynamics to correlation lengths and proposes a simple experimental method to measure these length-scales in supercooled liquids.

Findings

Probe particle dynamics reflect growth of dynamical heterogeneity.

Scaling theory successfully explains observed behaviors.

Method enables experimental measurement of static and dynamic correlations.

Abstract

The use of probe molecules to extract the local dynamical and structural properties of complex dynamical systems is an age-old technique both in simulations and experiments. A lot of important information which is not immediately accessible from the bulk measurements can be accessed via these local measurements. Still, a detailed understanding of how a probe particle's dynamics are affected by the surrounding liquid medium is not very well understood, especially in the supercooled temperature regime. This work shows how translational dynamics of a rod-like particle immersed in a supercooled liquid can give us information on the growth of the correlation length scale associated with dynamical heterogeneity and the multi-body static correlations in the medium. A unified scaling theory rationalizes all the observed results leading to the development of a novel yet simple method that is accessible in experiments to measure the growth of these important length-scales in molecular glass-forming liquids.