Heterogeneity and growing lengthscales in the dynamics of kinetically constrained lattice gases in two dimensions

TL;DR

This paper investigates dynamical heterogeneity and lengthscale growth in two kinetically constrained lattice gas models, revealing how these features relate to glass-forming behavior and violations of the Stokes-Einstein relation.

Contribution

It provides a comparative analysis of strong and fragile glassformers using kinetically constrained models, highlighting the growth of dynamical lengthscales and heterogeneity.

Findings

Heterogeneous dynamics with broad timescale distributions

Greater violation of Stokes-Einstein relation in fragile glassformer

Quantitative growth of dynamical lengthscales with increasing density

Abstract

We study dynamical heterogeneity and growing dynamical lengthscales in two kinetically constrained models, namely, the one- and two-vacancy assisted triangular lattice gases. One of the models is a strong glassformer and the other is a fragile glassformer. Both exhibit heterogeneous dynamics with broadly distributed timescales as seen in the distribution of persistence times. We show that the Stokes-Einstein relation is violated, to a greater degree in the fragile glassformer, and show how this violation is related to dynamic heterogeneity. We extract dynamical lengthscales from structure factors of mobile particles and show, quantitatively, the growth of this lengthscale as density increases. We comment on how the scaling of lengths and times in these models relates to that in facilitated spin models of glasses.