  Ultrathin ferromagnets with frustrated exchange and the Dzyaloshinskii-Moriya
interaction can support topological solitons such as skyrmions and
antiskyrmions, which are metastable and can be considered particle-antiparticle
counterparts. When spin-orbit torques are applied, the motion of an isolated
antiskyrmion driven beyond its Walker limit can generate skyrmion-antiskyrmion
pairs. Here, we use atomistic spin dynamics simulations to shed light on the
scattering processes involved in this pair generation. Under certain conditions
a proliferation of these particles and antiparticles can appear with a growth
rate and production asymmetry that depend on the strength of the chiral
interactions and the dissipative component of the spin-orbit torques. These
features are largely determined by scattering processes between antiskyrmions,
which can be elastic or result in bound states or annihilation.
