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中国物理学会期刊

双组分玻色-爱因斯坦凝聚体中PT对称势下的异步量子Kármán涡街

CSTR: 32037.14.aps.73.20232003

Asynchronous quantum Kármán vortex street in two-component Bose-Einstein condensate with PT symmetric potential

CSTR: 32037.14.aps.73.20232003
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  • 数值研究了相混合态双组分玻色-爱因斯坦凝聚体(Bose-Einstein condensate, BEC)中PT (parity-time)对称势下的动力学. 在障碍势不同的宽度和速度下发现了异步量子Kármán涡街、斜向漂移涡旋偶极子、V字形涡旋对、无规则量子湍流以及各种尾迹的组合模式. 研究了作用在移动障碍势上的拖拽力, 分析了涡旋对产生的力学机理. 在不同障碍势宽度和速度下, 系统地模拟了异步量子Kármán涡街和其他尾迹模式的参数区域. 同样分析了PT对称势中具有增益-损耗强度的虚部对异步量子Kármán涡街稳定性的影响. 最后, 提供了一个实现异步量子Kármán 涡街的实验方案.

     

    The dynamics of a miscible two-component Bose-Einstein condensate (BEC) with PT (parity-time) symmetric potential are investigated numerically. The dynamical behaviors of the system is described by Gross-Pitaevskii (GP) equations under the mean-field theory. Firstly, the ground state of the system is obtained by the imaginary-time propagation method. Then dynamical behaviors are numerically simulated by the time-splitting Fourier pseudo-spectral approach under periodic boundary conditions. By adjusting the width and velocity of the obstacle potential, various patterns such as no vortex, oblique drifting vortex dipole, V-shaped vortex pairs, irregular quantum turbulence and combined modes are studied. It is noted that the shedding vortex pairs in components 1 and 2 are staggered, which is called “the asynchronous quantum Kármán vortex street”. Here, the ratio of the distance between two vortex pairs in one row to the distance between vortex rows is approximately 0.18, which is less than the stability criterion 0.28 of classical fluid. We calculated the drag force acting on the obstacle potential during generation of the asynchronous quantum Kármán vortex street. It is found that periodical oscillation of the drag force is generated via drifting up or down of the vortex pairs. Meanwhile, we analyzed the influence of the imaginary part of the PT symmetric potential with gain-loss for wake. The trajectory and frequency of the vortex are changed, due to the imaginary part breaks the local symmetry of the system. In addition, the imaginary part affects the stability of the asynchronous quantum Kármán vortex street. Lots of numerical simulations are carried out to determine the parameter regions of various vortex shedding modes. We also proposed an experimental protocol to realize the asynchronous quantum Kármán vortex street in the miscible two-component BEC with PT symmetric potential.

     

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