Three-dimensional structure of a string-fluid complex plasma

M Y Pustylnik,V I Molotkov,A M Lipaev,V E Fortov,M Rubin-Zuzic,A V Zobnin,M H Thoma,G Joyce,D Erdle,H M Thomas,O Kononenko,V Nosenko,B Klumov,A D Usachev,O F Petrov

doi:10.1103/physrevresearch.2.033314

Abstract

Three-dimensional structure of complex (dusty) plasmas was investigated under long-term microgravity conditions in the International-Space-Station-based Plasmakristall-4 facility. The microparticle suspensions were confined in a polarity-switched dc discharge. The experimental results were compared to the results of the molecular dynamics simulations with the interparticle interaction potential represented as a superposition of isotropic Yukawa and anisotropic quadrupole terms. Both simulated and experimental data exhibited qualitatively similar structural features indicating the bulk liquid-like order with the inclusion of solid-like strings aligned with the axial electric field. Individual strings were identified and their size spectrum was calculated. The decay rate of the size spectrum was found to decrease with the enhancement of string-like structural features.

Highlights

Complex plasmas [1,2,3,4] are used in fundamental research as models for particle-resolved studies of generic classical condensed-matter phenomena
Bond angle distribution functions, and rotational invariants q4 and q6 exhibited fluid order, angular functions derived from the 3D pair correlation function showed clear axial peaks
Decay rate of the size spectrum of the string-like clusters was found to decrease on the increase of the axial peak

Summary

INTRODUCTION

Complex plasmas [1,2,3,4] are used in fundamental research as models for particle-resolved studies of generic classical condensed-matter phenomena. The 3D analysis of microparticle suspensions trapped by a polarity-switched discharge in the ground-based PK-4 setup showed the presence of crystalline order [21]. Complementary analysis of the same experimental data with the help of bond-orientational-order parameters [13] showed that the external fast oscillating electric field caused crystallization of the microparticle suspension and not the transition from isotropic to string fluid. [29], our work was done in an ISS-based facility This gave us sufficient time to investigate the 3D structure of our microparticle suspensions and to observe its evolution. Usage of dc electric field is not practical in complex plasmas since it causes instabilities in the microparticle suspensions [29,30,31] and under microgravity conditions their drift [31,32,33].

EXPERIMENT

SIMULATIONS

DATA ANALYSIS

RESULTS AND DISCUSSION

CONCLUSIONS