Study Of The Exciton-polaron System In Two-dimensional Parabolic Quantum Dot By Squeezed States Transformation Of Phonons

In the past decades, the study of low-dimensional material physics has received much attention. With the development of processing technology and nano-technology, it is possible to produce the quantum dot. Because quantum dot could be extensively used in different areas, that is made the study of quantum dot becoming one of the most important issues in modern physics.In the first chapter of my dissertation, first of all, the conceptions and the physical properties of exciton have been summarized. Then, we have introduced the research back ground and recent research achievements in quantum dot, especially concern on the research achievements of the model of quantum dot containing an exciton. There after, my work in this dissertation has been summarized.In the second chapter, firstly we have constructed the model of two-dimensional quantum dot in magnetic field which will be studied. Secondly, we can obtain the Hamiltonian of exciton-phonon system which is also expanded and simplified. Thirdly, the Hamiltonian of exciton-phonon system has been transformed by Lee-Low-Pines (LLP) unitary transformation. Fourthly, Hamiltonian including phonons has been squeezed by squeezing transformation and the ground-state energy of exciton-phonon system has been obtained by using averaging method.Fifthly, numerical results are presented for typical polar semiconductor of GaAs. Its parameters have been adopted by numerical calculation. Finally, the value data has been obtained. The results show that the ground-state energy of exciton-phonon system for parabolic quantum dots becomes larger with the characteristic frequency increases. It also becomes larger along with the increasing of the magnetic field. We also find that with the interaction strength of system increases, the ground-state energy and ground-state binding energy of exciton regularly reduce. Sixthly, because of limited space, we can only give the mathematical expression of excited-state wave functions and energy.In the last chapter of my dissertation, this article presents a summary of the main contents of my research, and has discussed and analyzed research work. At the same time, deficiency of the method been adopted by us have been summarized and give a prospect to the future research.