Self-Sustained Non-Equilibrium Co-existence of Fluid and Solid States in a Strongly Coupled Complex Plasma System

TL;DR

This paper investigates a complex plasma system exhibiting a unique non-equilibrium coexistence of solid and fluid states, driven by plasma energy conversion, with experimental and simulation evidence highlighting localized instabilities and energy transfer mechanisms.

Contribution

It provides the first detailed experimental and theoretical analysis of non-equilibrium coexistence of solid and fluid states in a complex plasma system due to plasma-mediated energy conversion.

Findings

Evidence of non-equilibrium coexistence of solid and fluid states.

Plasma-mediated non-reciprocal interactions cause localized heating and instabilities.

Simulations confirm structural nonuniformity and local instability development.

Abstract

A complex (dusty) plasma system is well known as a paradigmatic model for studying the kinetics of solid-liquid phase transitions in inactive condensed matter. At the same time, under certain conditions a complex plasma system can also display characteristics of an active medium with the micron-sized particles converting energy of the ambient environment into motility and thereby becoming active. We present a detailed analysis of the experimental complex plasmas system that shows evidence of a non-equilibrium stationary coexistence between a cold crystalline and a hot fluid state in the structure due to the conversion of plasma energy into the motion energy of microparticles in the central region of the system. The plasma mediated non-reciprocal interaction between the dust particles is the underlying mechanism for the enormous heating of the central subsystem, and it acts as a micro-scale energy source that keeps the central subsystem in the molten state. Accurate multiscale simulations of the system based on combined molecular dynamics and particle-in-cell approaches show that strong structural nonuniformity of the system under the action of electostatic trap makes development of instabilities a local process. We present both experimental tests conducted with a complex plasmas system in a DC glow discharge plasma and a detailed theoretical analysis.