Structure And Dynamics In Binary Complex Plasma

The structure of matter and its dynamics have always been important frontier topics in the fields of statistical physics,condensed matter physics,and materials science.Complex plasma is a special plasma composed of electrons,ions,neutral gases and solid or liquid mesoscopic particles.Complex plasma has the characteristics of direct measurement of particle motion and controllable external field.As a soft matter model system,it can not only study the properties of matter at the macroscopic scale from the perspective of fluid,but also study the physical properties of matter at the atomic scale from the perspective of dynamics.In the background introduction of the first chapter,we briefly reviewed the research history of complex plasmas,and introduced the outstanding features and basic properties of complex plasmas.We then introduce the structure and various dynamical phenomena of complex plasmas under gravitational conditions.With the development of microgravity experiments in recent years,we introduce the research status of complex plasma fluctuation phenomena and crystallization phenomena under microgravity conditions.The second chapter mainly introduces the experimental device,simulation method,machine learning method,structural analysis method and statistical analysis method used in this paper.In Chapter 3,the structural and vibrational properties of particles in quasi-two-dimensional nonreciprocal systems are studied,and the stable structures of quasi-two-dimensional particles under different confinement potentials and wake charges are given.The research shows that:(1)Under the joint influence of confinement potential and wake,there are many stable structures except hexagonal in the quasi-two-dimensional non-reciprocal system.(2)By adjusting the size of the confinement potential,the structural evolution of particles from single-layer hexagonal to double-layer hexagonal to double-layer tetragonal can be realized.(3)The spectral properties of the tetragonal crystal structure in the quasi-two-dimensional nonreciprocal system are studied.In Chapter 4,on the basis of the vibrational fluctuations in Chapter 3,the properties of the externally excited compressive fluctuations in quasi-two-dimensional nonreciprocal systems are studied.In the ground experiment,the laser excited the solitary wave to propagate in the crystal and the non-crystal,combined with the Langevin dynamics simulation to study the difference of the solitary wave propagation in different structures.The results show that the macroscopic performance of the solitary wave in the disordered system and the crystal system is similar,but the microscopic performance is obviously different.The wave front of the solitary wave propagates unevenly in the disordered system,and the structural reconstruction is more likely to occur.Chapter 5 studies the Mach cone fluctuations formed by individual particles and their propagation effects at the interface under microgravity conditions.Supersonic particles passing through the particle interface were observed in space station experiments,and the effect of supersonic particles passing through the bidisperse particle interface was studied in combination with Langevin dynamics simulations.The results show that:(1)multiple interface fluctuations will be formed when supersonic particles cross the interface,(2)different crossing directions and speeds of supersonic particles will lead to different interpenetration effects.Chapter 6 studies the phase transition process in bidisperse complex plasma under microgravity conditions,induces different crystallization paths through different experimental conditions,and studies the crystallization mechanism by combining simulations.The effect of the external confinement potential on the crystallization process is studied.Under the directional force,the particles mainly grow layered crystals;under the microgravity condition,the parabolic confinement potential under the joint action of the ion drag force and the electric field force can induce two crystal growth paths,one is from the edge to the inner growth Layered crystal growth,one is a non-layered crystal that grows from the inside to the edge.The results of experiments and simulations under microgravity conditions show that particles exhibit different kinetic behaviors under different crystallization paths,and the crystallization rate of layered crystals significantly exceeds that of non-layered crystals.In addition,the particle cloud interface structure undergoes a rapid evolution process in the layered crystallization process,while the particle cloud interface particles always evolve slowly in the non-layered crystallization process.The main factors affecting the interface structure are the confinement potential and the interaction potential between particles.In chapter 7,aiming at the situation that some particles are difficult to track in the experimental analysis process,the experimental diagnosis method is improved by using machine learning methods.This part of the research uses Langevin dynamics simulation combined with the optical display properties of particles to construct a training set,which provides a method to obtain a sufficient training set in the case of insufficient video recording of complex plasma experiments,and applies this method to phase transition experiments.In Chapter 8,we summarize the content of this paper and look forward to future research.