Phase separation, edge currents, and Hall effect for active matter with Magnus dynamics

Abstract

We examine run-and-tumble disks in two-dimensional systems where the particles also have a Magnus component to their dynamics. For increased activity, we find that the system forms a motility-induced phase-separated (MIPS) state with chiral edge flow around the clusters, where the direction of the current is correlated with the sign of the Magnus term. The stability of the MIPS state is non-monotonic as a function of increasing Magnus term amplitude, with the MIPS region first extending down to lower activities followed by a break up of MIPS at large Magnus amplitudes into a gel-like state. We examine the dynamics in the presence of quenched disorder and a uniform drive and find that the bulk flow exhibits a drive-dependent Hall angle. This is a result of the side jump effect produced by scattering from the pinning sites and is similar to the behavior found for skyrmions in chiral magnets with quenched disorder.

Active Magnus particles without pinning or drift force in the presence of gradually increasing Magnus terms showing a a rotating cluster mode, b a rotating cluster with clear shear banding at its edge, c a sheared band spanning the system, and d a disordered state where neither clusters nor shear bands can form. The colors indicate the net displacement of the particles, while the arrows show the rotation or shear directions