Dynamical anomalies and structural features of active Brownian particles characterized by two repulsive length scales

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 behavior 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 characterized by new and more complex structures compared with the hexatic phase observed in single length scale systems. From the dynamic analysis, we find, to our knowledge, the first manifestation of a dynamic heterogeneity in active particles, reminiscent of the glassy dynamics widely studied in passive colloids.