Scaling Description of the Relaxation Dynamics and Dynamical Heterogeneity of an Active Glass-forming Liquid

TL;DR

This paper investigates how activity influences the relaxation dynamics and heterogeneity in active glass-forming liquids, revealing enhanced density fluctuations, a transition to sub-Arrhenius relaxation, and size-dependent effects through a unified scaling theory.

Contribution

It introduces a novel scaling theory based on effective temperature to explain the relaxation spectrum and dynamical crossover in active glasses across different activity levels.

Findings

Activity enhances density fluctuations more than passive systems.

Active glasses exhibit sub-Arrhenius relaxation at high activity.

Large system size effects emerge at high activity levels.

Abstract

Active glasses refer to a class of driven non-equilibrium systems that share remarkably similar dynamical behavior as conventional glass-formers in equilibrium. Glass-like dynamical characteristics have been observed in various biological systems from micro to macro length scales. As activity induces additional fluctuations in the system, studying how they couple with density fluctuations is an interesting question to address. Via extensive molecular dynamics simulations, We show that activity enhances density fluctuations more strongly than its passive counterpart. Increasing activity beyond a limit results in the sub-Arrhenieus-type relaxation behavior in active glasses. We also propose a unified scaling theory that can rationalize the relaxation spectrum over a broad parameter range using the concept of an effective temperature. In particular, we show that our scaling theory can capture the dynamical crossover from super to sub-Arrhenius relaxation behavior by changing activity from small to large values. Furthermore, We present non-trivial system size dependencies of the relaxation time at large activity limits that have not been found in any passive systems or even in active systems at small activities.