Creation and Stability of Vortices in a Dilute Trapped Bose Gas

稀俘获玻色气体中涡旋的产生和稳定性

• 批准号: 9971518
• 负责人: Alexander Fetter
• 金额: $ 24.6万
• 依托单位: Stanford University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-05-15 至 2002-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9971518&HistoricalAwards=false
• 关键词: Creation; Stability; Vortices; Dilute; Trapped

9971518FetterThis grant will support theoretical research which investigates the connections between concepts developed for superfluid helium and stationary and rotating Bose-Einstein condensates formed from cold alkali atoms. One of the major current issues in this field is the creation, stability, and detection of quantized vortices in a simply connected condensate and quantized circulation in a multiply connected condensate. This research will use the known general theoretical description of a dilute Bose gas at low tempertaure to study the critical angular velocity for the creation of a vortex in rotating nonaxisymmetric condensates, where the rotating trap walls impart angular momentum to the atom, both in the nearly ideal limit of a small condensate and in the opposite limit of a large condensate. This introduces seveal new conceptual features. The analysis will be extended to include the creation of quantized circulation in a similar doubly connected nonaxisymmetric condensate.For a nonrotating axisymmetric condensate containing a singly quantized vortex, one single normal mode has a negative frequency, which indicates a potential instability. An external rotation raises this frequency and eventually makes it positive (thus stabilizing the vortex). This situation has been analyzed in detail for a vortex in a small nearly ideal condensate, where the negative-frequency normal mode involves a motion of the vortex core relative to the center of mass of the condensate. The opposite limit of a vortex in a large axisymmetric condensate has been studied with several different methods. The proposed generalization to a rotating nonaxisymmetric condensate is especially important in connection with possible experimental schemes for vortex creation, both in the small-condensate and large-condensate limits.For this superfluid helium films, the vortex lines become simply two-dimensional pancake vortices. This behavior makes it interesting to investigate the behavior of pancake vortices in a nearly two-dimensional condensate with extreme axial symmetry. In addition, there is the intriguing question whether such trapped systems can ever attain the strict two-dimensional limit.%%%This grant will support theoretical research which investigates the connections between concepts developed for superfluid helium (a fluid which flows without resistance) and stationary and rotating Bose-Einstein condensates formed from cold alkali atoms. Bose-Einstein condensates were predicted many years ago, but only recently have been observed in the laboratory. One of the major current issues in this field is the creation, stability, and detection of quantized vortices in a simply connected condensate and quantized circulation in a multiply connected condensate. This research will study various configurations of these condensates.***

这笔赠款将支持理论研究，研究超流氦概念与由冷碱原子形成的静止和旋转的玻色-爱因斯坦凝聚体之间的联系。这一领域当前的主要问题之一是单连通凝析油中量子化涡旋的产生、稳定性和检测，以及多连通凝析油中量子化循环的产生、稳定性和检测。这项研究将使用已知的低温下稀玻色气体的一般理论描述来研究在旋转的非轴对称凝聚体中产生涡旋的临界角速度，在旋转的非轴对称凝聚体中，旋转的囚禁壁给原子提供角动量，无论是在小凝聚体的接近理想极限下，还是在大凝聚体的相反极限下。这引入了几个新的概念特征。分析将扩展到包括在类似的双连通非轴对称凝聚体中产生量子化环流。对于包含单个量子化涡旋的非旋转轴对称凝聚体，一个单一简正模的频率为负，这表明存在潜在的不稳定性。外部旋转提高了这一频率，并最终使其为正数(从而稳定了涡旋)。对于小而接近理想的凝析油中的涡旋，详细地分析了这种情况，其中负频简正模涉及涡核相对于凝析油质量中心的运动。本文用几种不同的方法研究了大型轴对称凝析油中涡旋的反极限。对于旋转的非轴对称凝聚体，无论是在小凝聚态还是大凝聚态，涡旋线都是简单的二维薄饼状涡旋，这对于可能的实验方案尤其重要。这一行为使得研究具有极端轴对称的近二维凝聚体中的煎饼旋涡的行为变得很有趣。此外，还有一个耐人寻味的问题是，这样的囚禁系统是否能达到严格的二维极限。这笔拨款将支持理论研究，调查超流氦(一种无阻力流动的流体)概念与由冷碱原子形成的静止和旋转的玻色-爱因斯坦凝聚体之间的联系。玻色-爱因斯坦凝聚态在很多年前就被预测出来了，但直到最近才在实验室中观察到。这一领域当前的主要问题之一是单连通凝析油中量子化涡旋的产生、稳定性和检测，以及多连通凝析油中量子化循环的产生、稳定性和检测。这项研究将研究这些凝析油的各种构型。