Dynamical anomalies and structural features of Active Brownian Particles characterised by two repulsive length scales

TL;DR

This study investigates how active Brownian particles with a two-length-scale repulsive potential exhibit unique structural and dynamical behaviors, including complex phases and anomalous dynamics, depending on the ratio of interaction strengths.

Contribution

It introduces a novel model of active particles with two repulsive length scales and uncovers new structural phases and first evidence of anomalous dynamics in such systems.

Findings

Complex structures emerge during motility-induced phase separation.

The dense phase shows more intricate arrangements than in single-scale systems.

First observation of anomalous dynamics in active particles with two-length-scale interactions.

Abstract

In this work we study a two-dimensional system composed by Active Brownian Particles (ABPs) interacting via a repulsive potential with two-length-scales, a soft shell and a hard-core. Depending on the ratio between the strength of the soft shell barrier and the activity, we find two regimes: If this ratio is much larger or smaller than 1, the observed behaviour is comparable with ABPs interacting via a single length-scale potential. If this ratio is similar to 1, the two length-scales are relevant for both structure and dynamical properties. On the structural side, when the system exhibits a motility induced phase separation, the dense phase is characterised by new and more complex structures compared with the hexatic phase observed in single length-scale systems. On the dynamical side, as far as we are aware, this is the first representation of an anomalous dynamics in active particles.