Wave mode coupling due to plasma wakes in two-dimensional plasma crystals: In-depth view

TL;DR

This paper investigates how plasma wakes influence wave mode coupling in 2D plasma crystals, leading to instabilities and melting, by analyzing theoretical predictions and experimental signatures.

Contribution

It provides a comprehensive analysis of wake-mediated wave coupling, identifying key experimental fingerprints and critical parameter dependencies in 2D plasma crystals.

Findings

Identification of hybrid mode emergence

Critical angular dependence of instability

Distinct thresholds for mode coupling

Abstract

Experiments with two-dimensional (2D) plasma crystals are usually carried out in rf plasma sheaths, where the interparticle interactions are modified due to the presence of plasma wakes. The wake-mediated interactions result in the coupling between wave modes in 2D crystals, which can trigger the mode-coupling instability and cause melting. The theory predicts a number of distinct fingerprints to be observed upon the instability onset, such as the emergence of a new hybrid mode, a critical angular dependence, a mixed polarization, and distinct thresholds. In this paper we summarize these key features and provide their detailed discussion, analyze the critical dependence on experimental parameters, and highlight the outstanding issues.