Growing length and time scales in glass forming liquids

TL;DR

This study investigates the growth of length and time scales in glass-forming liquids through simulations, revealing that relaxation times are governed by configurational entropy rather than dynamical heterogeneity, challenging existing theories.

Contribution

It demonstrates that relaxation times are determined by configurational entropy across temperatures, contrasting with the growth of dynamical heterogeneity length scales.

Findings

Relaxation times do not scale with system size as dynamical heterogeneity does.

Relaxation times follow the Adam-Gibbs relation with configurational entropy.

Heterogeneity length scale shows deviations from theoretical predictions.

Abstract

We study the growing time scales and length scales associated with dynamical slow down for a realistic glass former, using computer simulations. We perform finite size scaling to evaluate a length scale associated with dynamical heterogeneity which grows as temperature decreases. However, relaxation times which also grow with decreasing temperature, do not show the same kind of scaling behavior with system size as the dynamical heterogeneity, indicating that relaxation times are not solely determined by the length scale of dynamical heterogeneity. We show that relaxation times are instead determined, for all studied system sizes and temperatures, by configurational entropy, in accordance with the Adam-Gibbs relation, but in disagreement with theoretical expectations based on spin-glass models that configurational entropy is not relevant at temperatures substantially above the critical temperature of mode coupling theory. The temperature dependence of the heterogeneity length scale shows significant deviations from theoretical expectations, and the length scale one may extract from the system size dependence of the configurational entropy has much weaker temperature dependence compared to the heterogeneity length scale at all studied temperatures. Our results provide new insights into the dynamics of glass-forming liquids and pose serious challenges to existing theoretical descriptions.