Attraction-Induced Cluster Fragmentation and Local Alignment in Active Particle Systems

We numerically studied active Brownian particles with attractive interactions. Contrary to our intuition, the attractive force between particles disrupts the formation of a single cluster observed in motility-induced phase separation, giving rise to a multi-cluster state characterized by a power-law distribution of cluster sizes. Remarkably, the self-propulsion directions spontaneously align within each cluster, resulting in enhanced cluster motility despite the absence of alignment interactions. This study revealed the intricate role of attractive interactions in the aggregation of motile systems.