Dynamics of Vortices in Bose-Einstein Condensates with Internal Degrees of Freedom

我们研究了气态玻色-爱因斯坦凝聚体中多电荷单量子涡旋的动力学。涡旋是通过控制磁阱中凝聚体的原子自旋来实现的。首先，我们利用众所周知的蒸发冷却程序在磁阱中创造了原子^<87 b> Rb的冷凝物。其次，我们通过将磁场偏置从0.5G改变为-0.5G来逆转凝聚体中的原子自旋。我们通过将场反转时间从1ms改为10ms来寻找最有效的涡生成时间。当反向时间为5ms时，旋涡的产生效率为100%。因为原子自旋为2，在我们的例子中，漩涡的电荷是4。涡旋消失约10ms，这是由于磁阱电位变形导致凝析油拉长导致磁场反转所致。为了避免这种情况的发生，我们尝试在光阱中用涡旋转移冷凝物。由于该陷阱的势形不受磁场的影响，因此冷凝物将被稳定地限制在陷阱中，并且漩涡的寿命有望延长。我们成功地将具有涡旋的凝聚体从磁阱转移到光阱。结果抑制了凝析油的膨胀，测量到的涡旋寿命约为20ms。我们有时在约20ms的捕获时间内测量到冷凝水中的两个漩涡。我们预计这些漩涡是由于一个四电荷单漩涡的衰变。作为未来的工作，我们希望详细展示这种动态。

We have studied the dynamics of the multi-charged single quantum vortex in gaseous Bose-Einstein condensates. The vortices were created by topological way which was realized by controlling the atomic spin in the condensates confined in a magnetic trap. First, we created the condensates of atomic ^<87>Rb in the magnetic trap by well known evaporative cooling procedure. Second, we reversed the atomic spins in the condensate by changing the magnetic bias field from 0.5G to -0.5G. We searched the most efficient time for vortex generation by changing the field-reverse time from 1ms to 10ms. The vortices were created in 100-% efficiency when the reverse time was 5ms. Because of the atomic spin of two, the charge of vortices is four in our case.The vortices were disappeared for about 10ms, because the condensates were elongated due to a deformation of magnetic trap potential resulting in the field reversal. In order to avoid this, we tried to transfer the condensates with vortex in the optical trap. Since the potential shape does not change by the magnetic fields for this trap, condensates would be stably confined in the trap, and the lifetime of vortex would be expected to lengthen.We successfully transferred the condensates with vortex from the magnetic trap to optical trap. As a result, the enlargement of the condensates was suppressed, and the measured lifetime of vortices was about 20ms. We sometimes measured two vortices in a condensate at the trap time of about 20ms. We expect that these vortices are due to decay of a four-charge single vortex. As a future work, we would like to demonstrate this dynamics in detail.