Producing flow in racetrack atom circuits by stirring
Producing flow in racetrack atom circuits by stirring
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DOI：
10.1103/physreva.102.063324
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发表时间：
2020-04
影响因子：
2.9
通讯作者：
Benjamin Eller;Olatunde Oladehin;Daniel Fogarty;C. Heller;C. Clark;M. Edwards
中科院分区：
文献类型：
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作者：
Benjamin Eller;Olatunde Oladehin;Daniel Fogarty;C. Heller;C. Clark;M. Edwards
我们研究了在“跑道”势中，玻色-爱因斯坦凝聚体如何通过一个宽的矩形势垒搅拌来产生宏观流动。这个势是由两个被长度为$L$的直通道隔开的半圆形通道组成的，如果$L=0，则为环势。我们给出了一大组模拟结果，在不同的屏障高度、搅拌速度、赛道几何形状和温度条件下，赛道冷凝物与障碍物搅拌。我们发现，搅拌很容易在环状和非环状几何结构中产生循环，但产生的确切流量很复杂。因此，我们还研究了搅拌过程中产生流动的机理。我们发现，环流是由涡旋/反涡对的交换引起的，该涡对最初是由势垒使冷凝物在压低密度区回流而产生的。当屏障强度达到临界值时，这些旋涡交换事件迅速接连发生，从而产生的循环的流动速度足以超过屏障的搅拌速度。最初局限在涡流交换中的涡流通过涡流交换过程中产生的扰动对转化为跑道周围的宏观流动。每一对均由沿反搅拌方向运动的涡/反涡对和沿搅拌方向运动的压缩波组成。这张制造流动的机制图将使搅拌时间表的设计能够产生所需的流动量。
We present a study of how macroscopic flow can be produced in Bose-Einstein condensate confined in a "racetrack" potential by stirring with a wide rectangular barrier. This potential consists of two half-circle channels separated by straight channels of length $L$ and is a ring potential if $L=0$. We present the results of a large set of simulations where racetrack condensates stirred with a barrier under varying conditions of barrier height, stir speed, racetrack geometry, and temperature. We found that stirring was readily able to produce circulation in ring and non-ring geometries but that the exact amount of flow produced was complicated. We therefore also studied the mechanism by which flow was produced in the stirring process. We found that circulation was induced by the swap of a vortex/anti-vortex pair that was initially created by backflow of the condensate in the region of depressed density by the barrier. When the barrier strength reached a critical value a number of these vortex-swap events occurred in rapid succession so that flow speed of the circulation produced was enough to exceed the stir speed of the barrier. Flow that was initially localized in the vortices involved in the vortex swap was converted into macroscopic flow around the racetrack by pairs of disturbances each generated during the vortex swap. Each pair consisted of a vortex/anti-vortex pair moving in the anti-stir direction and a compression wave moving in the stir direction. This picture of the mechanism for making flow will enable the design of stirring schedules that create a desired amount of flow.