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

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。这种涡旋是通过控制磁囚禁中凝聚体中的原子自旋来实现的。首先，通过众所周知的蒸发冷却过程，我们在磁囚禁中产生了原子^&lt；87和Rb的凝聚态。其次，通过将磁场从0.5g改变到-0.5g，我们反转了凝聚态中的原子自旋。通过将场反转时间从1ms改变为10ms，我们寻找到了最有效的涡旋产生时间。当反转时间为5ms时，以100%的效率产生涡流。在我们的例子中，由于原子自旋为2，涡旋的电荷为4。涡旋消失了约10毫秒，这是因为凝聚体由于磁陷势的形变而拉长，导致磁场反转。为了避免这种情况，我们尝试将凝聚体与涡旋一起传输到光阱中。由于这种陷阱的势能形状不受磁场的影响，凝聚体将被稳定地限制在陷阱中，并且涡旋的寿命有望延长。结果表明，冷凝物的膨胀受到了抑制，测得的涡旋寿命约为20ms。我们有时在约20毫秒的捕获时间内测量凝聚体中的两个涡旋。我们认为这些涡旋是由于四电荷单涡旋的衰变所致。作为未来的工作，我们希望详细演示这种动力学。

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.