Yang Xue-Ying, Li Xiao-Lin, Tang Na, Zhou Zhi-Kun, Song Lin, Zhang Juan, Shi Yu-Ren
College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070, People's Republic of China.
Key Laboratory of Atomic and Molecular Physics and Functional Materials of Gansu Province, Lanzhou 730070, People's Republic of China.
Phys Rev E. 2020 Sep;102(3-1):032217. doi: 10.1103/PhysRevE.102.032217.
The dynamics of pseudo-spin-1/2 Bose-Einstein condensates with weak spin-orbit coupling through a moving obstacle potential are studied numerically. Four types of wakes are observed and the phase diagrams are determined for different spin-orbit coupling strengths. The conditions to form Bénard-von Kármán vortex street are rather rigorous, and we investigate in detail the dynamical characteristics of the vortex streets. The two point vortices in a pair rotate around their center, and the angular velocity and their distance oscillate periodically. The oscillation intensifies with increasing spin-orbit coupling strengths, and it makes part of the vortex pairs dissociate into separate vortices or combine into single ones and destroys the vortex street in the end. The width b of the street and the distance l between two consecutive vortex pairs of the same circulation are determined by the potential radius and its moving velocity, respectively. The b/l ratios are independent of the spin-orbit coupling strength and fall in the range 0.19-0.27, which is a little smaller than the stability criterion 0.28 for classical fluids. Proper b/l ratios are necessary to form Bénard-von Kármán vortex street, but the spin-orbit coupling strength affects the stability of the street patterns. Finally, we propose a protocol to experimentally realize the vortex street in ^{87}Rb spin-orbit-coupling Bose-Einstein condensates.
通过移动障碍物势对具有弱自旋 - 轨道耦合的伪自旋 - 1/2玻色 - 爱因斯坦凝聚体的动力学进行了数值研究。观察到四种类型的尾流，并确定了不同自旋 - 轨道耦合强度下的相图。形成贝纳德 - 冯·卡门涡街的条件相当严格，我们详细研究了涡街的动力学特性。一对中的两个点涡围绕它们的中心旋转，角速度和它们之间的距离周期性振荡。随着自旋 - 轨道耦合强度的增加，振荡加剧，这使得部分涡对解离成单独的涡或合并成单个涡，最终破坏涡街。涡街的宽度b和具有相同环流的两个连续涡对之间的距离l分别由势半径及其移动速度决定。b/l比与自旋 - 轨道耦合强度无关，落在0.19 - 0.27范围内，这比经典流体的稳定性判据0.28略小。适当的b/l比对于形成贝纳德 - 冯·卡门涡街是必要的，但自旋 - 轨道耦合强度会影响涡街图案的稳定性。最后，我们提出了一种在(^{87}Rb)自旋 - 轨道耦合玻色 - 爱因斯坦凝聚体中通过实验实现涡街的方案。
