  Motivated by the recent work in skyrmions and active chiral matter systems,
we examine pairs and small clusters of repulsively interacting point particles
in the limit where the dynamics is dominated by the Magnus force. We find that
particles with the same Magnus force can form stable pairs, triples and higher
ordered clusters or exhibit chaotic motion. For mixtures of particles with
opposite Magnus force, particle pairs can combine to form translating dipoles.
Under an applied drive, particles with the same Magnus force translate;
however, particles with different or opposite Magnus force exhibit a
drive-dependent decoupling transition. When the particles interact with a
repulsive obstacle, they can form localized orbits with depinning or unwinding
transitions under an applied drive. We examine the interaction of these
particles with clusters or lines of obstacles, and find that the particles can
become trapped in orbits that encircle multiple obstacles. Under an ac drive,
we observe a series of ratchet effects, including ratchet reversals, for
particles interacting with a line of obstacles due to the formation of
commensurate orbits. Finally, in assemblies of particles with mixed Magnus
forces of the same sign, we find that the particles with the largest Magnus
force become localized in the center of the cluster, while for mixtures with
opposite Magnus forces, the motion is dominated by transient local pairs or
clusters, where the translating pairs can be regarded as a form of active
matter.
