合成磁场下玻色—爱因斯坦凝聚体涡旋态的研究

发布时间：2018-04-23 13:12

本文选题：玻色-爱因斯坦凝聚 + 合成磁场　；参考：《北京科技大学》2016年博士论文

【摘要】：量子化涡旋是超流/超导体中的基本现象之一。对于中性原子气体,涡旋通常可以通过旋转框架方法得到。最近,在合成磁场实验中观察到了涡旋,并且人们期待它能够有效地加载大的角动量。本论文通过数值求解Gross-Pitaevskii (GP)方程对合成磁场中玻色.爱因斯坦凝聚体的涡旋形成问题进行了研究。对于约束在简谐势阱中的凝聚体,研究发现在相同的旋转频率下,合成磁场方法产生涡旋的效率低于旋转框架方法,这与人们的期待不同。在旋转框架下,有效约束势被旋转频率削弱了,约束越弱越容易产生涡旋：而在合成磁场中势阱的约束与旋转频率无关。增强原子间的相互作用有助于产生更多的涡旋,甚至能够形成Abrikosov涡旋晶格结构。此外还验证了费曼规则的有效性。其次,研究了简谐势阱和光晶格下的涡旋形成过程。发现光晶格的引入能够增加涡旋的数目,但是仍不能像旋转框架那样加载大的角动量。计算结果表明系统的化学势和能量随旋转频率的增加变化不大。最后,考虑了偶极相互作用对涡旋形成过程的影响。数值结果显示,涡旋形成过程在不同极化方向下表现出不同的行为。随着旋转频率的增加,涡旋数和涡旋行数比旋转框架中的少。
[Abstract]:Quantized vortex is one of the basic phenomena in superfluid / superconductor. For neutral atomic gases, vortices are usually obtained by rotating frames. Recently, a vortex has been observed in synthetic magnetic field experiments, and it is expected to be able to load large angular momentum effectively. In this paper, we numerically solve the Gross-Pitaevskii equation for Bose in synthetic magnetic field. The vortex formation of Einstein condensate has been studied. It is found that the efficiency of the synthetic magnetic field method to generate vortex is lower than that of the rotating frame method at the same rotating frequency for the condensate confined in the harmonic potential well, which is different from the expectation of people. In the rotating frame, the effective confinement potential is weakened by the rotation frequency, and the weaker the constraint is, the more easily the vortex is generated. However, in the synthetic magnetic field, the constraint of the potential well is independent of the rotation frequency. The enhancement of the interaction between atoms contributes to the formation of more vortices and even the formation of the Abrikosov vortex lattice structure. In addition, the validity of Feynman rule is verified. Secondly, the vortex formation process under the harmonic potential well and optical lattice is studied. It is found that the introduction of optical lattice can increase the number of vortices, but the large angular momentum can not be loaded as the rotating frame. The results show that the chemical potential and energy of the system change little with the increase of rotation frequency. Finally, the effect of dipole interaction on vortex formation is considered. Numerical results show that the vortex formation process exhibits different behavior in different polarization directions. With the increase of rotation frequency, the number of vortex and the number of vortex rows are less than those in the rotating frame.
【学位授予单位】：北京科技大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：O469

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