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题名	光晶格中超冷原子的能谱和相变的研究
作者	韩玖荣
学位类别	博士
答辩日期	2005
授予单位	中国科学院上海光学精密机械研究所
导师	王育竹
关键词	光晶格 超冷原子 量子相变 能谱 费米化玻色气体
其他题名	Energy Spectrum and Quantum Phase TRansition of Ultracold Atoms in OPtical Lattices
中文摘要	原子在光晶格中的运动完全可类比于电子在固体晶格中的运动，因此光晶格提供了独特的机遇探索一些只有凝聚态物理才能理解的物理现象。本文从光晶格的基本概念、特性出发讨论了超冷原子在光晶格存在的情况下的量子相变。首先综述了光晶格中超冷原子的量子相变的研究现状。在第二章里我们研究了光晶格中两分量玻色爱因斯坦凝聚原子的能谱，其能带结构可以用来决定超流一莫特绝缘体转变的临界条件；并且讨沦了玻色一玻色近邻相互作用对能带结构和相变的影响：我们还讨论了通过调节实验参数在实验上观察这些新相以及它们的转变的可能性。第三章研究了超冷玻色一费米混合物在光晶格中的能谱和量子相变，玻色原子有两个能带，费米原子只有一个能带。由路径积分方法我们得到了玻色一费米混合物的相图，相图浓赖于实验参数。我们着重讨沦了费米子的存在是怎样影响玻色子的超流到M。tt一绝缘相变的：在特定的超低温的条件下，玻色子能够表现为费米子的行为。这种费米化的气体建立了一种全新的量子态物质叫做TG气体。这是美国物理学家Girardeau在1960年预台的，已经由德国和美国物理学家于2004年在实验上证实。第四章我们用微扰展开和格林函数方法研究了光晶格中费米化的玻色子的能谱。费米化的玻色子非常象没有相互作用的无自旋的费米子。能谱分裂成两个能带。我们用玻格留波夫方法也得到的泪应的基态能量和准粒子激发谱。我们发现准粒子激发潜相应于能隙。两种万法得到的结果能很好地相符。第五章给出了结论和今后工作的展望。
英文摘要	The motion of the atom in an optical lattice is analogous fully to that of an electron in a solid state crystals. Therefore the optical lattice provides a particular opportunity to explore some physics phenomena, which are understood in condensate matter physics. This dissertation starts with the basic conception of optical lattice, presents the quantum phase transition of ultra-cold atoms in optical lattices. First we summarize the advance in studying quantum phase transition of ultra-cold atom in optical lattices. In Chapter 2, we investigate he energy spectrum of two-component Bose-Einstein condensates in optical lattices. The energy bands can be used to determine the superfluity Mott-insulator phase transition. We also discuss the effect of nearest neighboring interaction between atoms on the energy spectrum and phase transition. According to the phase diagrams, we discuss the possibility of observing the superfluity and Mott-insulator phases of two component condensates by adjusting the actual parameters in future experiments. In chapter 3, we show the energy band structure of an ultracold atomic Bose-Fermi mixture in optical lattices: two energy bands for bosonic atom and a single band for fermionic atom. The energy band structure can determine the superfluity Mott-insulator phase transition. We find the phase diagram of the mixture by means of path integral, and the phase transition depending on the experimental parameters. We discuss the effect of fermions on the bosonic phase transition from superfluity to Mott-insulator. Under special conditions, bosons exhibit fermionic properties. Such a fermionized Bose gas constitutes a novel quantum state of matter called a Tonks-Girardeau gas. It was predicted almost 40 years ago by US physicist Marvin D. Girardeau in 1960, and realized last year by US physicists and Germany physicists. In chapter 4, we investigate the energy spectrum of ground state and quasi-particle excitation spectrum of hard-core bosons, which behave very much like spinless noninteracting fermions. in optical lattices by means of the perturbation expansion and Green's function. The energy spectrum splits into two energy bands. We also find corresponding energy of ground state and excitation spectrum of quasi-particle with Bogoliubov approach. The excitation spectrum of quasi-particle corresponds to energy gap. The results obtained with two methods are in good agreement. The conclusion and the outlook are presented in chapter 5.
语种	中文
内容类型	学位论文
源URL	[http://ir.siom.ac.cn/handle/181231/15532]
专题	上海光学精密机械研究所_学位论文
推荐引用方式 GB/T 7714	韩玖荣. 光晶格中超冷原子的能谱和相变的研究[D]. 中国科学院上海光学精密机械研究所. 2005.

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