Dynamic phase transition induced by active molecules simulating a facilitation mechanism in a supercooled liquid

TL;DR

This study uses active particles to explore facilitation effects in supercooled liquids, revealing a phase transition linked to structural aggregation and increased fluidization when active particle dynamics match the material's natural mobility timescale.

Contribution

It introduces a novel simulation of facilitation in supercooled liquids using active particles, demonstrating a phase transition driven by matching timescales.

Findings

Activation causes fluidization and increased heterogeneity.

A phase transition occurs with structural aggregation of active molecules.

Fluidization sharply increases at the transition point.

Abstract

The purpose of this work is to use active particles to study the effect of facilitation on supercooled liquids. To this end we investigate the behavior of a model supercooled liquid doped with intermittently active and intermittently slowed particles. To simulate a facilitation mechanism, the active particles are submitted intermittently to a force following the mobility of the most mobile molecule around, while the slowed particles are submitted to a friction force. We observe upon activation, a fluidization of the whole medium simultaneously to a large increase of the dynamic heterogeneity. This effect is reminiscent of the fluidization observed with molecular motors doping of the medium. When the mobility characteristic time used in the facilitation mechanism matches the physical time characterizing the spontaneous mobility aggregation of the material, we observe a phase transition associated with a structural aggregation of active molecules. This transition is accompanied by a sharp increase of the fluidization and dynamic heterogeneity.