Wake-mediated propulsion of an extra particle in a two-dimensional plasma crystal

We analyze in simulations and theory the self-propelled motion of an upstream ``extra'' particle in a two-dimensional plasma crystal. Experimental observations [1] showed that the extra particle is confined in a channel of two neighboring rows of particles and moves persistently through the crystal. We use the simple model of a pointlike ion wake charge to reproduce this intriguing effect in simulations. We show that the nonreciprocity of the particle interaction, owing to the plasma flow, is responsible for an asymmetric deformation of the channel that enables the self-propelled motion of the extra particle [2]. We find good agreement of the terminal extra-particle velocity with our theoretical considerations and with experiments. [1] C.-R. Du, V. Nosenko, S. Zhdanov, H. M. Thomas, G. E. Morfill. Channeling of particles and associated anomalous transport in a two-dimensional complex plasma crystal. Phys. Rev. E, 89:021101, 2014 [2] I. Laut, C. Räth, S. K. Zhdanov, V. Nosenko, G. Morfill, H. Thomas. Wake-mediated propulsion of an upstream particle in two-dimensional plasma crystals. Phys. Rev. Lett. 118:075002, 201