Cooperative Motion of Active Brownian Spheres in Three-Dimensional Dense Suspensions

TL;DR

This study investigates the behavior of self-propelled spherical particles in three-dimensional suspensions, revealing phase separation, cooperative motion, and scale-free correlations near the glass transition, advancing understanding of active matter dynamics.

Contribution

It provides new insights into phase separation and cooperative motion in 3D active Brownian particles without alignment mechanisms.

Findings

Phase separation into dilute and dense phases at high activity.

Long-lived cooperative particle motion in dense regimes.

Nearly scale-free spatial correlations near the glass transition.

Abstract

The structural and dynamical properties of suspensions of self-propelled Brownian particles of spherical shape are investigated in three spatial dimensions. Our simulations reveal a phase separation into a dilute and a dense phase, above a certain density and strength of self-propulsion. The packing fraction of the dense phase approaches random close packing at high activity, yet the system remains fluid. Although no alignment mechanism exists in this model, we find long-lived cooperative motion of the particles in the dense regime. This behavior is probably due to an interface-induced sorting process. Spatial displacement correlation functions are nearly scale-free for systems with densities close to or above the glass transition density of passive systems.