Self-reverting vortices in chiral active matter

TL;DR

This paper predicts a new class of self-reverting vortices in chiral active matter, arising from attraction and chirality, which can oscillate or maintain constant vorticity, expanding understanding of collective behaviors.

Contribution

It introduces a novel type of collective vortex behavior in chiral active particles driven by attraction and chirality without alignment interactions.

Findings

Emergence of self-reverting vortices with oscillating vorticity.

Vortices can have constant or periodically reversing vorticity.

Theoretical and simulation results support the existence of these vortices.

Abstract

There is currently a strong interest in the collective behavior of chiral active particles that can propel and rotate themselves. In the presence of alignment interactions for many chiral particles, chiral self-propulsion can induce vortex patterns in the velocity fields. However, these emerging patterns are non-permanent, and do not induce global vorticity. Here we combine theoretical arguments and computer simulations to predict a so-far unknown class of collective behavior. We show that, for chiral active particles, vortices with significant dynamical coherence emerge spontaneously. They originate from the interplay between attraction interactions and chirality in the absence of alignment interactions. Depending on parameters, the vortices can either feature a constant vorticity or a vorticity that oscillates periodically in time, resulting in self-reverting vortices. Our results may guide future experiments to realize customized collective phenomena such as spontaneously rotating gears and patterns with a self-reverting order.