Collective dynamics and phase transition of active matter in presence of orientation adapters

Abstract

In this work, the orientation adapter, a species of active particles that adapt their direction of motion from the other active particles, is introduced. The orientation adapters exist besides the usual Vicsek-like particles; both are self-driven, however, follow different interaction rules. We have studied the dynamics in high speed of the particles keeping dissimilar speeds for these different species. The effect of orientation adapters on the collective behaviour of the system is explored in this model. The orientational order-disorder phase transition is mainly studied in such systems. First, for equal density of both species, when the adapter speed $v_a=1.2v_0$ and usual particles speed $v_0=1.0$, both adapters and the usual particles form dense travelling bands and move in the same direction. Near the transition point, such bands appear and disappear over time, giving rise to the co-existence of two phases. The adapters and the usual particles both undergo a discontinuous transition. The nature of the transition is further confirmed by the existence of hysteresis in the order parameter under a continuously varying noise field. However, when the adapter velocity becomes much higher than the usual SPPs $v_a \approx 7v_0$, the formation of travelling bands disappears from the system, and the transition becomes continuous. The density ratio is also varied, keeping the velocities constant, and the phase transition is studied. For a high adapter velocity with $v_a=10v_0$, the continuous transition is found with low-density values of the adapters. The critical exponents related to the continuous transition are also determined.