物理学报2017，Vol.66Issue(13)：47-56,10.DOI:10.7498/aps.66.130305
具有面内四极磁场的旋转玻色-爱因斯坦凝聚体的基态结构研究
Ground state of a rotating Bose-Einstein condensate with in-plane quadrupole field
摘要
Abstract
Compared with the scalar Bose-Einstein condensate, the spinor Bose-Einstein condensate, in which internal degrees of freedom are essentially free, has aroused the great interest in the study of topological excitations. In particular, the spinor Bose-Einstein condensate with rotation provides a new opportunity for studying novel quantum states including a coreless vortex and vortex lattice. To date, in the presence of rotation, a great many of studies on the topological excitations have focused on the Bose-Einstein condensate system with the uniform Zeeman field or without external magnetic field. However, the ground state structure of a rotating Bose-Einstein condensate in the presence of in-plane gradient-magnetic-field remains an open question. In this work, by using the imaginary-time propagation method, we study the ground state structure of a rotating Bose-Einstein condensate with in-plane quadrupole field. We first examine the effect of in-plane quadrupole field on trapped spinor Bose-Einstein condensate. The numerical results show that Mermin-Ho vortex can be induced only by the cooperation between quadrupole field and rotation. When magnetic field gradient is increased, the vortices around Mermin-Ho vortex display the symmetrical arrangement. For an even larger magnetic field gradient strength, the system only presents the Mermin-Ho vortex because the in-plane quadrupole field can prevent the vortices around Mermin-Ho vortex from occurring. Next, we examine the effect of the rotation on trapped spinor Bose-Einstein condensate. A phase transition from a polar-core vortex to a Mermin-Ho vortex is found through applying a rotational potential, which is caused by the cooperation between the in-plane quadrupole field and the rotation. We further study the combined effects of spin exchange interaction and density-density interaction. The results confirm that in the presence of the quadrupole field both spin exchange interaction and density-density interaction, acting as controllable parameters, can control the number of the vortices around Mermin-Ho vortex. The corresponding number of the vortices shows step behavior with increasing the ratio between spin exchange interaction and density-density interaction, which behaves as hexagon, pentagon, square and triangle. It is found that two types of topology structures, i.e., the hyperbolic meron and half-skyrmion, can occur in the present system. These vortex structures can be realized via time-of-flight absorption imaging technique. Our results not only provide an opportunity to investigate the exotic vortex structures and the corresponding phase transitions in a controlled platform, but also lay the foundation for the study of topological defect subjected to gauge field and dipolar interaction in future.关键词
旋转玻色-爱因斯坦凝聚体/面内四极磁场/自旋交换相互作用/自旋结构Key words
rotating Bose-Einstein condensate/in-plane quadrupole field/spin-exchange interaction/spin texture引用本文复制引用
刘静思,李吉,刘伍明..具有面内四极磁场的旋转玻色-爱因斯坦凝聚体的基态结构研究[J].物理学报,2017,66(13):47-56,10.基金项目
国家重点研发计划"量子调控与量子信息"重点专项(批准号: 2016YFA0301500)和国家自然科学基金(批准号: 11434015, KZ201610005011)资助的课题. Project supported by the NKRDP (Grant No. 2016YFA0301500), and the National Natural Science Foundation of China (Grant Nos. 1143401, KZ201610005011). （批准号: 2016YFA0301500）
