Structure and Phase transitions of Yukawa balls

TL;DR

This review discusses the structural properties, phase transitions, and dynamic behaviors of Yukawa balls, a type of finite spherical dusty plasma crystal, highlighting experimental observations and theoretical models that explain their static and dynamic features.

Contribution

It provides a comprehensive overview of experimental and theoretical studies on Yukawa balls, including new insights into their shell structures, phase transitions, and excitation properties.

Findings

Experimental observations match simple theoretical models.

Shell structures and metastable states are clearly identified.

Normal modes and dynamic behaviors are characterized.

Abstract

In this review, an overview of structural properties and phase transitions in finite spherical dusty (complex) plasma crystals -- so-called Yukawa balls -- is given. These novel kinds of Wigner crystals can be directly analyzed experimentally with video cameras. The experiments clearly reveal a shell structure and allow to determine the shell populations, to observe metastable states and transitions between configurations as well as phase transitions. The experimental observations of the static properties are well explained by a rather simple theoretical model which treats the dust particles as being confined by a parabolic potential and interacting via an isotropic Yukawa pair potential. The excitation properties of the Yukawa balls such as normal modes and the dynamic behavior, including the time-dependent formation of the crystal requires, in addition, to include the effect of friction between the dust particles and the neutral gas. Aside from first-principle molecular dynamics and Monte Carlo simulations several analytical approaches are reviewed which include shell models and a continuum theory. A summary of recent results and theory-experiment comparisons is given and questions for future research activities are outlined.