Microscopic structure in a two-dimensional liquid-like dusty plasma
Creators: name: Zhuravlyov, Vitaliy
Publisher: name: University of Iowa
Year: 2023
Subjects: subject: dusty plasma
subject: dynamic structure factor
subject: hyperuniformity
subject: static structure factor
subject: strongly coupled plasma
subject: public abstract
subject: Condensed Matter Physics
subject: FOS: Physical sciences

description: The main physical system that I am studying in this thesis is a dusty plasma. It is defined as a collection of electrons, ions, neutral gas molecules, and solid microspheres. These solid microspheres, the so-called dust particles, typically attain a large negative charge in the laboratory setting. This massive charge allows the particles to be levitated in a plasma and since they are large enough to reflect laser light, the dust particles can be imaged by a video camera. Another consequence of having a large charge is that the collection of dust particles can exist in crystalline and liquid-like states. This condition is known as strong coupling.
description: One of the main advantages of a dusty plasma is that you can analyze those crystalline or liquid-like structures using microscopic particle positions. This allows researchers like me to study the microscopic structure of liquids on essentially an “atomic” level.
description: In this thesis, I am interested in studying two types of structural quantities: static structure factor and dynamic structure factor. Static structure factor can be thought of as a diffraction pattern or an inverse measure of atomic arrangements in a substance like solid or liquid. Dynamic structure factor is essentially a generalization of static structure factor: in addition to spatial variation in structure, the dynamic structure factor also reveals how the structure evolves with time or frequency.
description: The first two projects that I describe in this thesis are mainly concerned with the static structure factor S(k). In the first of those two projects, I investigate how small the values of S(k) are at long wavelengths, i.e., small wavenumbers k. I analyze both experimental and simulation data of a two-dimensional (2D) dusty plasma in a liquid-like state. I found that the values of S(k) at small k are especially small compared to other liquids that were previously investigated in various experiments. This comparison suggests that a 2D dusty plasma liquid might be closer to an exotic and relatively new concept of hyperuniformity, which requires those values of S(k) to be very small at small k. In other words, systems like 2D dusty plasma liquids might lead toward creating hyperuniform materials with exotic properties.
description: In the second project, I further investigate the values of S(k) using simulation data. Since simulation data were in general consistent with the experiment in the first project, I exploited the fact that one can investigate a parameter space more thoroughly and freely using simulation data. This study revealed that there is a noticeable finite-size effect in S(k) at small k. To study those finite-size effects, I test some formulas that I either found in the literature or empirically designed with the help of my collaborators. I also suggest procedures that can be used to correct those finite-size effects using those formulas that were shown to accurately model those effects.
description: Finally, in the last project, I investigated the high-frequency behavior of the dynamic structure factor using both experimental and simulation data. I found that the dynamic structure factor did not decay fast enough for the so-called frequency moments to converge. This result might question the validity of some theories that use those moments. Those theories attempt to describe the shape of the dynamic structure factor, and if they are invalid, then there would be a need for new theories.