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Structure and Dynamics of Vortices in a Bose Condenstate with Spin Degree of Freedom

具有自旋自由度的玻色凝聚体中涡旋的结构和动力学

基本信息

批准号：
11640361
负责人：
NAKAHARA Mikio
金额：
$ 1.73万
依托单位：
Kinki University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2000
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-11640361/
关键词：
Bose Condensation Alkali atoms Hyperfine Spin Vortices Homotopy Group Textures 渦糸永久流基本群テクスチャー

项目摘要

・It is shown that a vortex can be continuously created in a Bose-Einstein condensate (BEC) of alkali atoms with |F|=1 confined in a multiply connected region by making use of a spin degree of freedom of the order parameter of a BEC.The mutiple-connecedness is realised by introducing an optical plug along the center of the vortex. The BEC stays within a weak-field seeking state during the time evolution thanks to the optical plug. This is demonstrated explicitly by solving the generalised Gross-Pitaevskii (GP) equation numerially.・This scenario is also analysed from a topological point of view. It is shown that the fundamental group π_1(SO(3))=Z_2 makes it possible to create a doubly-quantised vortex continuously from a vortex-free state.・An optical plug must be introduced in the above scenario since the weakfield seeking state and the strong-field seeking state have degenerate levels along the axis when the axial magnetic field vanishes during the creation of a vortex. It should be noted, however, that this happens only at a moment of time and at a single point in a plane. Thus it is expected that those particles taking part in the Majorana flops are negligible This conjecture is assured by solving the generalised GP equation numerically.・We also studied a BEC with |F|=2 and found that a vortex with four units of circulation is created in the present scenario.

利用玻色-爱因斯坦凝聚体(BEC)的自旋自由度，利用玻色-爱因斯坦凝聚体(BEC)序参数的自旋自由度，在BEC的多连通区域内连续产生涡旋，并在BEC中心引入光学塞子，实现多连通。由于光塞的作用，BEC在时间演化过程中保持在弱场寻道状态。通过数值求解广义Gross-Pitaevskii(GP)方程，证明了这一点。·还从拓扑的角度分析了这一设想。结果表明，基本群π_1(SO(3))=Z_2使得从无涡旋状态连续产生双量子化涡旋成为可能。·在上述场景中必须引入光学插头，因为在涡旋产生期间，当轴向磁场消失时，弱场寻道状态和强场寻道状态沿轴具有简并能级。然而，应该注意的是，这种情况只发生在某个时刻和平面上的一个点上。因此，通过数值求解广义GP方程，可以认为参与Majorana Flopps的粒子是可以忽略的。·我们还研究了|F|=2的BEC，发现在本方案中产生了一个具有四个环流单位的涡旋。