Confinement controlled dynamical structural rearrangement in a quasi-2D dusty plasma crystal

Abstract

In this work, we present experimental results on the structural transition of a two-dimensional dust crystal through controlled adjustment of its radial confinement while keeping all other discharge parameters constant. The experiments are performed in an L-shaped Dusty Plasma Experimental device in a DC glow discharge argon plasma environment. Initially, a purely 2D dust crystal is formed inside a circular confining ring at the interface of the plasma-cathode sheath region. This monolayer with a hexagonal lattice configuration of the dust particles gets buckled when the sheath thickness around the radial confinement ring is reduced. A bilayer with a square lattice configuration emerges in the dust system due to the onset of a transverse instability. The multiple crystalline domains at this lower confinement show signatures of a constant structural rearrangement in the system. The timescale associated with this rearrangement is quantified from the bond-orientational correlation function. It is found that the heterogeneous cooperative micro-motion of particles in the quasi-layered system is responsible for the rearrangement over the passage of time.