Melting transition of two-dimensional complex plasma crystal in the DC glow discharge

Abstract: The formation of self-consistent dust crystal and its melting is a well known phenomenon in rf generated plasma but remains challenging in DC glow discharge plasma. Here, we report the melting of a two dimensional dusty plasma crystal, suspended in the cathode sheath of a DC glow discharge plasma. The experiments are carried out in a $\Pi-$shaped Dusty Plasma Experimental (DPEx) device where a stationary crystal of melamine formaldehyde particles is formed between the confining strips in a background of Argon plasma. The stable structure breaks and leads to a fluid state on reducing the neutral pressure.% and even reaches to a gas like states at very low pressure. The neutral pressure range where this melting transition is observed is an order of magnitude less than what reported in rf discharge plasma. The transition is confirmed by evaluating the variation in different characteristic parameters such as the pair correlation function, voronoi diagram, local bond order, defect fraction and dust temperature as a function of background neutral pressure. The transition is attributed to an increase in effective particle temperature which we believe is occurred due to increase in charge fluctuation and ion streaming. The special feature of the device that helps formation of dust crystal and its melting in DC glow discharge can be implemented to study various phenomena associated with dust crystal in dc glow discharge plasma devices.