Collective motion of self-propelled chiral particles in a noisy environment

Chiral active matter has garnered widespread attention due to its ubiquitous presence in nature. This article, based on the basic idea of the Vicsek model, adopts a distance-dependent Fermi-type interaction and achieves the chirality by a rotation matrix to describe the collective motion of chiral self-propelled particles influenced by noise. The collective motion of the particles exhibits complex dependencies on the box size, particle chirality, noise strength, and velocity magnitude. Especially intriguing, it is observed that under medium box size and weak chirality, the system’s order parameter initially increases and then decreases with the enhancement of chirality; under weak noise conditions, the order parameter shows a similar trend of first increasing and then decreasing with the noise strength. The mechanism behind the former is revealed by the time correlation of the order parameter, while the latter is explained by the spatial correlation of velocity fluctuations. Based on the medium box size and weak noise, the order parameter evolves from low-order to high-order with increasing velocity magnitude. Additionally, it is proposed to use the maximum variance of the order parameter to delineate the boundary between the high-order and low-order. The findings and analyses allow us to achieve global order by adjusting the combination of the aforementioned factors.