Influence of interaction softness in phase separation of active particles

TL;DR

This study investigates how the softness of inter-particle repulsion influences motility-induced phase separation in active Brownian particles, revealing that increased softness delays phase separation and can be characterized by a single lengthscale.

Contribution

It introduces a scaling framework linking interaction softness to phase separation dynamics and properties in active particle systems.

Findings

Increased softness reduces phase separation ability.

A single lengthscale explains post-separation properties.

Phase separation time is highly sensitive to softness.

Abstract

Using a minimal model of active Brownian discs, we study the effect of a crucial parameter, namely the softness of the inter-particle repulsion, on motility-induced phase separation. We show that an increase in particle softness reduces the ability of the system to phase-separate and the system exhibit a delayed transition. After phase separation, the system state properties can be explained by a single relevant lengthscale, the effective inter-particle distance. We estimate this lengthscale analytically and use it to rescale the state properties at dense phase for systems with different interaction softness. Using this lengthscale, we provide a scaling relation for the time taken to phase separate which shows a high sensitivity to the interaction softness.