Chirality transitions in a system of active flat spinners

Abstract

We study in this work the 2D dynamics of an experimental system of disk-shaped rotors, fluidized by turbulent upflow. Contrary to previous knowledge, our experiments show the same particle chiral geometry can produce flows with different chiralities. In particular, we unveil a conspicuous complex chiral flow, which displays multiple persistent vortexes with either sign, located randomly in the system. This peculiar phase mediates a continuous transition, which takes place as the kinetic energy input increases, from a flow with positive chirality (one vortex rotating in the same direction as particles spin) to a flow with negative chirality (one vortex in opposite sense to particle spin). We find that these surprising transitions are determined by the specific state of the statistical correlations between particle spin and translational velocity. We discuss how these correlations are determined in turn by the combined action of a series of mechanisms (for instance, heat dissipation at the boundaries, particle activity, average kinetic energy...), several of which are unveiled here.

15 pages, 6 figures (including supplementary material). To appear in Phys. Rev. Research (2022)

References in corpus (4)

• Emergent vortices in populations of colloidal rollers
• Purely hydrodynamic ordering of rotating disks at a finite Reynolds number
• Polar state memory in active fluids
• Thermal Schwinger Effect: Defect Production in Compressed Filament Bundles

Cited by in corpus (10)

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• Diffusive regimes in a two-dimensional chiral fluid
• Field-Theory of Active Chiral Hard Disks: A First-Principles Approach to Steric Interactions
• Analytical solution for the hydrodynamic resistance of a disk in a compressible fluid layer with odd viscosity on a rigid substrate
• Inertial Spinner Swarm Experiments: Spin Pumping, Entropy Oscillations and Spin Frustration
• Spin and velocity correlations in a confined two-dimensional fluid of disk-shaped active rotors
• Chirality, confinement and dimensionality govern re-entrant transitions in active matter
• Phase separation in a chiral active fluid of inertial self-spinning disks
• Odd elasticity in disordered chiral active materials
• Kinetic Theory of Chiral Active Disks: Odd Transport and Torque Density