Spontaneous rotation can stabilise ordered chiral active fluids

TL;DR

This paper develops a dynamical theory showing that spontaneous rotation in chiral active fluids stabilizes ordered phases and suppresses chaotic defect formation, offering insights into biological and synthetic active matter.

Contribution

It introduces the first complete dynamical theory for orientationally ordered chiral particles in 2D, revealing stabilization effects of intrinsic rotation.

Findings

Rotating chiral particles form remarkably stable phase-coherent states.

Intrinsic rotation suppresses defect separation and chaotic flows.

Chirality acts as a stabilization mechanism in active systems.

Abstract

Active hydrodynamic theories are a powerful tool to study the emergent ordered phases of internally driven particles such as bird flocks, bacterial suspension and their artificial analogues. While theories of orientationally ordered phases are by now well established, the effect of chirality on these phases is much less studied. In this paper, we present the first complete dynamical theory of orientationally ordered chiral particles in two-dimensional incompressible systems. We show that phase-coherent states of rotating chiral particles are remarkably stable in both momentum-conserved and non-conserved systems in contrast to their non-rotating counterparts. Furthermore, defect separation -- which drives chaotic flows in non-rotating active fluids -- is suppressed by intrinsic rotation of chiral active particles. We thus establish chirality as a source of dramatic stabilization in active systems, which could be key in interpreting the collective behaviours of some biological tissues, cytoskeletal systems and collections of bacteria.