Nonhomogeneity of phase state in a dusty plasma monolayer with nonreciprocal particle interactions

A monolayer—quasi-two-dimensional finite system—of Yukawa particles in a harmonic trap is under consideration. The effect of monolayer nonhomogeneity on dynamic properties and melting is studied. The results for two models of particle interactions are compared. The first model includes the reciprocal Yukawa potential and electrostatic harmonic trap. The second model additionally employs the point charge approximation of plasma wakes. It accounts for the nonreciprocity of interactions and anomalous heating of particle motion observed in dusty plasma experiments. It is demonstrated that in the point-wake model, both out-of-plane and in-plane kinetic energies of particles are radially dependent. This effect transforms the spatial distribution of dynamic characteristics in the monolayer. We show that the nonuniformity of monolayer properties might lead to several nonuniform melting scenarios and several scenarios of phase coexistence in the system. In the monolayer without nonreciprocal interactions, molten periphery coexists with a solid core. In the monolayer with plasma wakes, the opposite scenario is observed due to the joint effect of nonreciprocity and structural nonuniformity in the system. A perspective method to determine the position of the phase boundary is proposed.