Phase Transition in Dusty Plasmas

Abstract

We discuss the microphysical processes that trigger phase transitions in a dusty plasma not in thermodynamic equilibrium and subject to ion streaming. For pressures below the critical pressure P, for condensation, the grains acquire a large random kinetic energy and form a weakly coupled fluid. If pressure is increased to greater than P-c the grains lose their kinetic energy and reach a strongly coupled crystalline state. The dust heating in the fluid phase is due to an ion-dust two-stream instability, which is stabilized at P > P-c by the combined effect of ion-neutral and dust-neutral collisions. When the pressure is decreased from the crystalline state to below the critical pressure P-m for melting, transverse phonons are destabilized by ion streaming, which destroys the short range ordering of the dust grains and triggers melting. It is found that P-m < Pc. For P-m < P < P-c mixed phase states can exist. Although the system is not in thermodynamic equilibrium, the process resembles closely to a first order phase transition.