The Energy Gap And Impurity Modes In A One-Dimensional Dusty Plasma Crystal Chain

Dusty, or complex, plasmas are ionized gases in which submicron-to-micron sized particles, usually called dust grains, are embedded. Dusty plasmas are widely found in astrophysical environments and laboratories. In recent years, this field has attracted much attention all over the world. The study on electrostatic dusty plasma waves is a fundamental area in dusty plasma researches. Lattice waves in the dusty plasma crystals are typical electrostatic modes. Laboratory observations of dusty plasma crystals have thus opened a new research area in dusty plasma physics. A dusty plasma crystal is a strongly coupled system. Easily controllable and macroscopically observable in experiments, it is then a perfect model for studying phase transition and important properties of solid state matters in a macroscopic level. Many key plasma parameters can be obtained in electrostatic dusty plasma wave studies which therefore have become a very important diagnostic method for dusty plasmas.The lattice waves in dusty plasmas have been studied in this thesis. In the first two chapters, a brief review of dusty plasmas and crystals has been made, including basic concepts, general study methods and recent research progresses.In Chapter 3, by considering different characteristics of various dust particles, horizontal lattice waves in a one-dimensional dust plasma crystal containing two types of particles are investigated. In laboratory environments, the mass and charge of individual dust particle may be different from each other. Due to the faster electron thermal velocity than that of ions, dust particles are usually negatively charged. Thus they can be approximated as negative point charges. Assuming that a one-dimensional dust chain consists of the two types of dust particles, the dispersion relations of the longitudinal and transverse lattice waves are derived and discussed. It is shown that an energy gap is formed in such a plasma crystal chain.In the fourth chapter, based on the result in the previous chapter we add a new impurity dust particle in the one-dimensional dust chain. Horizontal lattice waves are then investigated in such a case. The dispersion relations of the longitudinal and transverse waves are derived and discussed. It is shown that the impurity effect leads to the formation of a new impurity mode in the energy gap.The thesis is then concluded by a brief summary.