Reentrant phase separation behavior of active particles with anisotropic Janus interaction.

Recent studies showed substantial evidence of dynamic clustering and phase separation in active particle systems, but the role of anisotropic interaction between the particles has not been addressed yet. Here we investigate the phase separation of active particles that experience an anisotropic Janus interaction with tunable strength in two dimensional space by using Langevin dynamics simulations. Interestingly, we find that phase separation shows a re-entrance behavior with variation of the Janus interaction strength: while small Janus interaction can enhance the formation of living clusters and phase separation, large Janus interaction would destroy the large cluster. We explain this nontrivial phenomenon via the competition between the self-propulsion and the short-ranged Janus interaction: while self-propulsion can lead to clustering of the active particles, the Janus interaction favors the formation of states with attractive sides close to each other and repulsive sides staying apart.