Laning and Clustering Transitions in Driven Binary Active Matter Systems

TL;DR

This study investigates how activity influences phase transitions in driven binary active matter, revealing that activity can both enhance and disrupt laning, leading to a novel clustered laning state.

Contribution

It introduces a simulation of active disks with run-and-tumble dynamics, uncovering how activity levels affect mobility and phase transitions in driven active matter systems.

Findings

Increasing activity can break up jammed states and increase mobility.

High activity levels induce a transition from laning to disordered states.

A new drive-induced clustered laning state is identified.

Abstract

It is well known that a binary system of non-active disks that experience driving in opposite directions exhibits jammed, phase separated, disordered, and laning states. In active matter systems, such as a crowd of pedestrians, driving in opposite directions is common and relevant, especially in conditions which are characterized by high pedestrian density and emergency. In such cases, the transition from laning to disordered states may be associated with the onset of a panic state. We simulate a laning system containing active disks that obey run-and-tumble dynamics, and we measure the drift mobility and structure as a function of run length, disk density, and drift force. The activity of each disk can be quantified based on the correlation timescale of the velocity vector. We find that in some cases, increasing the activity can increase the system mobility by breaking up jammed configurations; however, an activity level that is too high can reduce the mobility by increasing the probability of disk-disk collisions. In the laning state, the increase of activity induces a sharp transition to a disordered strongly fluctuating state with reduced mobility. We identify a novel drive-induced clustered laning state that remains stable even at densities below the activity-induced clustering transition of the undriven system.