arXiv 2210.044032022-10cond-mat.quant-gas

玻色-爱因斯坦凝聚体中高斯障碍物的最小临界速度

Minimum critical velocity of a Gaussian obstacle in a Bose-Einstein condensate

Haneul Kwak, Jong Heum Jung, Yong-il Shin

备注：: 9 pages, 7 figures
DOI：: 10.1103/PhysRevA.107.023310

摘要：

当超流体流过障碍物时，在超过某个临界速度时，可以在尾流中产生量子化涡流。在Kwon等人的实验[Phys. Rev. A 91，053615（2015）]中，使用移动排斥高斯势测量原子玻色-爱因斯坦凝聚体（BEC）的临界速度$v_c$，并且当障碍物的势高$V_0$接近凝聚体化学势$μ$时，$v_c$最小化。在这里，我们数值研究的演变的临界涡脱落在二维BEC与增加$V_0$，并表明，最小$v_c$在临界强度$V_{0c}\approx μ$的结果从本地密度降低和涡钉扎效应的排斥障碍。研究了$v_c$下方运动障碍物周围超流的空间分布。当$V_0$增加到$V_{c0}$时，障碍物尖端的粒子密度减小，在临界强度时，突然形成一个涡旋偶极子，并被移动的障碍物拖曳，表明涡旋钉扎的开始。最小$v_c$与障碍物尺寸$σ$呈现幂律缩放，如$v_c\sim σ^{-γ}$与$γ\approx 1/2$。

英文摘要：

When a superfluid flows past an obstacle, quantized vortices can be created in the wake above a certain critical velocity. In the experiment by Kwon et al. [Phys. Rev. A 91, 053615 (2015)], the critical velocity $v_c$ was measured for atomic Bose-Einstein condensates (BECs) using a moving repulsive Gaussian potential and $v_c$ was minimized when the potential height $V_0$ of the obstacle was close to the condensate chemical potential $μ$. Here we numerically investigate the evolution of the critical vortex shedding in a two-dimensional BEC with increasing $V_0$ and show that the minimum $v_c$ at the critical strength $V_{0c}\approx μ$ results from the local density reduction and vortex pinning effect of the repulsive obstacle. The spatial distribution of the superflow around the moving obstacle just below $v_c$ is examined. The particle density at the tip of the obstacle decreases as $V_0$ increases to $V_{c0}$ and at the critical strength, a vortex dipole is suddenly formed and dragged by the moving obstacle, indicating the onset of vortex pinning. The minimum $v_c$ exhibits power-law scaling with the obstacle size $σ$ as $v_c\sim σ^{-γ}$ with $γ\approx 1/2$.

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英文摘要：

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