Phase Separation in Binary Mixtures of Active Brownian Particles*

Active systems are composed of self-propelled (i.e. active) particles that locally convert energy into motion and exhibit emergent collective behaviors, such as fish schooling and bird flocking. Most works, so far, have focused on monodisperse, one-component active systems or binary mixtures where only one species is active (the other is Brownian). However, real systems are heterogeneous and may consist of several active components (e.g. active processes in the cell). We perform overdamped Brownian dynamics simulations of binary active systems, where both species are active. The difference between the species is only their activity (Péclet number). We find that our binary active systems also demonstrate motility-induced phase separation but we also see a separation between more and less active species that is driven by the ratio of their respective activities. We discuss the dynamics of mixed-activity clusters and how they vary as a function of activity and density.