环形运动势搅拌下偶极玻色-爱因斯坦凝聚体中的von Kármán涡街  

von Kármán vortex street in dipole BEC induced bya circular moving potential

作　　者：席忠红 赵永珍 王光弼 石玉仁[2,3] Xi Zhong-Hong;Zhao Yong-Zhen;Wang Guang-Bi;Shi Yu-Ren(Department of Physics and Hydropower Engineering,Gansu Normal College for Nationalities,Hezuo 747000,China;College of Physics and Electronic Engineering,Northwest Normal University,Lanzhou 730070,China;Laboratory of Atomic Molecular Physics&Functional Material of Gansu Province,Lanzhou 730070,China)

机构地区：[1]甘肃民族师范学院物理与水电工程系,合作747000 [2]西北师范大学物理与电子工程学院,兰州730070 [3]甘肃省原子分子物理与功能材料重点实验室,兰州730070

出　　处：《物理学报》2023年第8期77-83,共7页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:12065022);2022年陇原青年创新创业人才(个人)项目;2020年甘肃省高等教育教学成果培育项目(批准号:184);甘肃省2023年高校教师创新基金项目(批准号:2023B-219);甘肃民族师范学院教学成果培育项目(批准号:GNUNJXCGPY2216);甘肃省教育科学“十四五”规划2021年度课题(批准号:2060)资助的课题.

摘　　要：数值研究了偶极玻色-爱因斯坦凝聚体(Bose-Einstein condensate,BEC)在环形运动高斯势搅拌时的动力学行为.当高斯势运动速度和尺寸逐渐变化时,偶极BEC中将出现稳定层流、涡旋偶极子、Bénard–von Kármán(BvK)涡街以及混乱激发4种模式.结果表明高斯势在偶极BEC中圆周运动时产生涡街的条件非常苛刻,只有适当尺寸的高斯势以合适的速度运动时,尾流中周期性脱落的具有相同旋量的涡旋对稳定的分布在内外两个圆环上,形成BvK涡街.在实验参数下进行系统数值计算得到了不同偶极相互作用时的相图,讨论了偶极相互作用以及高斯势速度和尺寸对不同激发模式的影响.通过高斯势所受拖拽力的计算,分析了不同激发的物理学机制.The dynamical behaviors of a dipole Bose-Einstein condensate(BEC),which is stirred by a circular moving Gaussian potential,are numerically investigated by using the mean-field theory.In this work,the atom is assumed to polarize along the z-axis.Firstly,the stationary state of the system is obtained by solving the quasitwo-dimensional Gross-Pitaevskki equation numerically under periodic boundary conditions.And then,taking the obtained ground state as the initial condition,the dynamic evolution of the dipole BEC system is studied by the time-splitting Fourier spectrum method.Four types of emissions,namely,the stable laminar flow,vortex dipole,Bénard–von Kármán(BvK)vortex street and irregular turbulence,are observed in the wake when the velocity and size of the Gaussian potential change gradually.When the velocity of the Gaussian potential reaches the critical velocity of vortex excitation,vortex pairs with opposite circulations alternately fall off from the surface of the Gaussian potential.Owing to the interaction between the vortex dipoles,the dipoles rotate around their own centers.Finally,a ring structure will be formed and exist in the wake stably for a long time.With the increase of the velocity of Gaussian potential,the period of dipoles shedding is also shortened.For the appropriate velocity and size of the Gaussian potential,the vortex pairs with the same circulations will periodically fall off from the Gaussian potential and stably distributed on the inner and outer rings,forming BvK vortex street.Our caculation reveals that the conditions for forming BvK vortex street when the dipole BEC is stirred with a circular moving potential are very restricted.When the velocity or size of the Gaussian potential continues to increase,the phenomenon of the periodic vortex pairs shedding in the wake of the Gaussian potential will disappear,and the shedding pattern of the dipole BEC becomes irregular.Using experimental parameters,the parameter ranges of different dipole interactions are obtained through numerical

关 键 词：偶极Bose-Einstein 凝聚 偶极子 Bénard–von Kármán 涡街 

分 类 号：O469[理学—凝聚态物理]