We demonstrate that edge currents develop in active chiral matter due to boundary shielding over a wide range of densities corresponding to a gas, fluid, and crystal. The system is composed of spinning disk-shaped grains with chirally arranged tilted legs confined in a circular vibrating chamber. The edge currents are shown to increasingly drive circulating bulk flows with area fraction as percolating clusters develop due to increasing spin-coupling between neighbors mediated by frictional contacts. Edge currents are observed even in the dilute limit. While, at low area fraction, the average flux vanishes except within a distance that is of the order of a particle diameter of the boundary, the penetration depth grows with increasing area fraction until a solid-body rotation is achieved corresponding to the highest packing, where the particles are fully caged with hexagonal order and spin in phase with the entire packing. A coarse-grained model, based on the increased collisional interlocking of the particles with area fraction and the emergence of order, captures the observed flow fields. © 2023 American Physical Society.
Physical Review E
Petroff, Alexander P.; Whittington, Christopher; and Kudrolli, Arshad, "Density-mediated spin correlations drive edge-to-bulk flow transition in active chiral matter" (2023). Physics. 7.
Published source must be acknowledged with citation:
Petroff, Alexander P., Christopher Whittington, and Arshad Kudrolli. "Density Mediated Spin Correlations Drive Edge to Bulk Flow Transition in Active Chiral Matter." Physical Review E, 108, 1, 2023.