Dusty Plasma Liquid Crystal Analogues

This study examines dusty plasma structures (mixtures of ions, electrons, neutrals, and micron-sized dust particles) using data from the Plasmakristall-4 (PK-4) facility on board the International Space Sstation. Dust grains immersed in plasma become negatively charged and can self-organize into strongly coupled fluids and crystalline structures. Microgravity dusty plasmas have been observed to form extended field-aligned filaments in the DC discharge of the PK-4 experiments, which have been compared to the filamentary state in electrorheological (ER) fluids. However, pair correlation functions and other structural analysis of the filamentary state of dusty plasma suggests that meaningful comparisons can be made between those structures and liquid crystals (LCs) with rod-shaped molecules. Specifically, we demonstrate that the coupling between dust particles within filamenrs is crystal-like, while the coupling across filaments is liquid-like. In addition to common orientation along a director axis (nematic behavior), the dust filaments also appear to align in large-scale nested structures, or shells (smectic behavior). In this talk we will demonstrate the liquid crystal properties of microgravity dusty plasma and propose ways to study universality of liquid crystal phase transitions and pattern formation using a dusty plasma analogue.