Nonlinear waves and inelastic effects in complex plasmas

Complex (dusty) plasmas are mixtures of micron-sized spheres with ion-electron plasmas. These spheres collect ions and electrons and acquire large negative electric charges. Due to collective interaction, they form crystal- or liquid-like structures. These structures can propagate linear and nonlinear waves such as solitons, and exhibit phase transitions. Our experiments were performed in a radio-frequency capacitively coupled gas discharge. Plastic microspheres were introduced into the plasma where they levitated above a powered electrode. A monolayer hexagonal lattice was formed, which was excited by applying electrostatic pulses. A series of experiments were performed in order to study soliton propagation in an inhomogeneous lattice, interaction of two counter-propagating solitons, as well as the influence of deformations on the crystal structure. The experiments were compared with molecular dynamics simulations based on the 5-th order Runge-Kutta solver of the equations of motion.