In a bilayered system of particles with wake-mediated interactions, the action-reaction symmetry for the effective forces between particles of different layers is broken. Under quite general conditions we show that, if the interaction nonreciprocity exceeds a certain threshold, this creates an active dispersion of self-propelled clusters of Brownian particles. The emerging activity promotes unusual melting scenarios and an enormous diffusivity in the dense fluid. Our results are obtained by computer simulation and analytical theory and can be verified in experiments with colloidal dispersions and complex plasmas.
The wake potential in a plasma is characterized by a complicated (non-exponential) screening. However, the resulting deviations from the Yukawa model of the wake-mediated interactions were shown to have only a minor quantitative effect on the dynamics.42,43
Given the vertical separation of particles within an active unit, we refrain from the term active molecules used in Ref. 6.