Self-Diffusion in 2D Dusty Plasma Liquids: Numerical Simulation Results

TL;DR

This study uses Brownian dynamics simulations to analyze self-diffusion in 2D dusty plasma liquids, revealing how damping influences diffusion behavior and reconciling previous conflicting experimental and simulation results.

Contribution

It provides detailed numerical insights into the transition from super-diffusion to sub-diffusion in 2D dusty plasma liquids based on damping effects.

Findings

Super-diffusion is most significant at very low damping rates.

VAF exhibits a combined $t^{-1}$ and exponential decay at intermediate coupling.

Transition from super-diffusion to sub-diffusion with increasing damping.

Abstract

We perform Brownian dynamics simulations for studying the self-diffusion in two-dimensional (2D) dusty plasma liquids, in terms of both mean-square displacement and velocity autocorrelation function (VAF). Super-diffusion of charged dust particles has been observed to be most significant at infinitely small damping rate $\gamma$ for intermediate coupling strength, where the long-time asymptotic behavior of VAF is found to be the product of $t^{-1}$ and $\exp{(-\gamma t)}$. The former represents the prediction of early theories in 2D simple liquids and the latter the VAF of a free Brownian particle. This leads to a smooth transition from super-diffusion to normal diffusion, and then to sub-diffusion with an increase of the damping rate. These results well explain the seemingly contradictory scattered in recent classical molecular dynamics simulations and experiments of dusty plasmas.