Lane Formation in Driven Binary Complex Plasmas on the International Space Station

We conducted a series of experiments to study lane formation in complex plasma, using the PK-3 Plus Laboratory in the International Space Station. In our experiments, small (driven) microparticles penetrate into a cloud of large (background) particles, revealing a strong tendency toward lane formation: When the driving force is strong enough, particles of both sorts form interpenetrating lines. Typically, the lanes exhibit a considerable anisotropic structural order accompanied by an enhancement of their (unidirectional) mobility. Laning is quantified locally in terms of the anisotropic scaling index. Using a ??nematic?? order parameter, the observed time-resolved lane-formation process is compared to a set of computer simulations of a binary Yukawa model with Langevin dynamics. This not only yields a best fit but also reveals a strong influence of the initial experimental conditions on the dynamics of lane formation.