| 题名 | 紧横向束缚和无序势场下的多组份玻色-爱因斯坦凝聚 |
| 作者 | 崔国栋 |
| 学位类别 | 博士 |
| 答辩日期 | 2013 |
| 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 | 多组份玻色-爱因斯坦凝聚，输运动力学，安德森局域化， 无序势场 |
| 其他题名 | Multi-component Bose-Einstein Condensate in tightly transverse confinement and disordered potential |
| 中文摘要 | 本论文通过数值求解Gross-Pitaevskii方程（GP）和非多项式非线性薛定谔方程（Nonpolynomial nonlinear Schrödinger equation, NPSE）来研究多组份玻色-爱因斯坦凝聚体（BEC）在横向紧束缚囚禁及无序势场下的基态和动力学特性。多组份凝聚体具有独特的性质，诸如相分离和自旋交换等现象。这里，在一维情形下，我们着重考虑紧的横向囚禁对雪茄状两组份凝聚体的可混-不可混相变的影响。此外，对双组份凝聚体在一维准周期外势场下的输运动力学也做了细致地研究。主要结果概述如下： 1.利用耦合GP和耦合NPSE方程研究了一维双组份玻色气体基态，发现横向囚禁效应对BEC波包的空间分布有显著影响。在高原子数密度或强原子间相互作用条件下，GP方程所引入的固定横向宽度假设不再精确。横向宽度和一维有效非线性耦合强度在空间上是非均匀分布。在实验和理论上，人们已发现双组份BEC在横向紧束缚下会存在波函数可混和不可混的量子相变。本论文在数值计算NPSE方程基础上，发现组份间原子相互作用强度及轴向阱频率能明显改变可混-不可混的相变临界点。 2. 凝聚态物理中，安德森局域化被认为是特定金属-绝缘体相变中的基本现象。近年来，无序势场中的超冷原子，比如激光散斑和无公度光晶格，可以用来解决一些远没有透彻理解的科学难题。论文探讨了态依赖无公度光晶格（即仅有一个组份的原子能感受准周期势场）的情况下的双组份玻色气体输运性质。如所预期的一样，会出现一种组份原子波包的空间局域化。进一步，发现另一不受无序势影响的组份被局域组份分裂，而不是弹道式的扩散。对组份间原子相互作用和粒子数比的影响也做了细致分析。这些结果可以用有效势模型来解释。 3. 最后，简单介绍过去几年里我做的一些实验工作，包括半导体激光器及其在饱和吸收光谱和稳频中的应用。 |
| 英文摘要 | In this thesis, we investigate ground state and dynamics of multi-component Bose-Einstein condensates (BECs) in the situation of tightly transverse confinement and disordered potential, respectively, by numerically solving Gross-Pitaevskii (GP) equation and nonpolynomial nonlinear Schrödinger equation (NPSE). Multi-component BECs have unique characteristics such as phase separation and spin exchange. Here we focus on the effect of the tightly transverse trapping on the miscibility-immiscibility transition of a cigar-shaped two-component BEC in one-dimension geometry. In addition, transport dynamics of such BEC experienced by a quasi-periodic external potential is also been investigated in detail. Main results are briefly reviewed as follows. 1. GP and NPSE equations are numerically solved to obtain the ground state of a multi-component Bose, and it is found that the wavefunction is strongly dependent on the transverse trapping. In the situations of dense gas or strong mutual atomic interaction, the assumption of the constant transverse width introduced by GP equation is not accurate. The transverse width and 1D effective nonlinear coupling strengths are inhomogeneous in space. The miscible and immiscible phases have been theoretically predicted by GP equation and demonstrated experimentally in the presence of tightly transverse confinement. As predicted by our NPSE calculations, however, the threshold of the miscibility-immiscibility transition has a remarkable dependence on inter-component interaction strength and axial trap frequency. 2. In condensed-matter physics, Anderson localization is now considered a fundamental phenomenon underlying certain metal-insulator transitions. In recent years, ultracold atoms in disordered potential, such as laser speckle and incommensurate optical lattice, have allowed one to address a variety of questions which are still far from understood. We investigate the transport of a two-component Bose gas in the presence of a state-dependent incommensurate optical lattice subject to one component. The appearance of the expected localized wavefunction of the component can be observed. Furthermore, it is found that another component free from disordered potential is split by the localized companion rather than diffuses ballistically. The influence of the inter-component atomic interaction and particle number ratio is also analyzed in detail. The results can be explained by effective potential model. 3. Finally, experimental works during several years including semiconductor laser and its applications in saturation absorption spectroscopy and frequency stabilization are also presented. |
| 语种 | 中文 |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/15755]  |
| 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 | 崔国栋. 紧横向束缚和无序势场下的多组份玻色-爱因斯坦凝聚[D]. 中国科学院上海光学精密机械研究所. 2013. |
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