环形势阱中自旋-轨道耦合旋转玻色-爱因斯坦凝聚体的基态

Ground state of spin-orbit coupled rotating ferromagnetic Bose-Einstein condensate in toroidal trap

研究了在环形势阱中自旋-轨道耦合旋转玻色-爱因斯坦凝聚体的基态结构.探索了自旋-轨道耦合作用和旋转效应对基态的影响.结果发现,在环形势阱下,基态结构呈现环形分布的half-skyrmion链.调节自旋-轨道耦合强度,不仅可以改变体系内half-skyrmion数量,而且能够调控half-skyrmion环形排列的对称性.随着旋转频率增大,体系从平面波相转化为环形对称排列的half-skyrmion链相,最后过渡到三角格子的half-skyrmion相.讨论了自旋相互作用和势阱形状对基态的影响.自旋-轨道耦合强度和旋转频率作为体系的调控参数,可用于控制不同基态相间的转化.

Realization of spinor Bose-Einstein condensate in an optical trap has made it possible to create a variety of topological nontrivial structures,due to the vector character of the order parameter.Recently,artificial spinorbit coupling in the spinor Bose-Einstein condensate,owing to coupling between the spin and the center-ofmass motion of the atom,provides an unprecedented opportunity to search for novel quantum states.As is well known,the potential well in the Bose-Einstein condensate is adjustable.The toroidal trap is an important model potential because of its simplicity and richness in physics.In particular,the spinor Bose-Einstein condensate under the toroidal trap has brought an ideal platform for studying fascinating properties of a superfluid,such as persistent flow and symmetry-breaking localization.For the case of the spin-orbit-coupled Bose-Einstein condensate,the previous studies of the toroidal trap mainly focused on the two-component or antiferromagnetic case.However,in the presence of a toroidal trap,there remains an open question whether the combined effects of the spin-orbit coupling and rotation can produce previously unknown types of topological excitations in the ferromagnetic Bose-Einstein condensate.In this work,by using quasi two-dimensional Gross-Pitaevskii equations,we study the ground state structure of spin-orbit coupled rotating ferromagnetic Bose-Einstein condensate in the toroidal trap.We concentrate on the effects of the spin-orbit coupling and the rotation on the ground states.The numerical results show that in the presence of a toroidal trap,the ground state structure is displayed as half-skyrmion chain with circular distribution.Adjusting the strength of spinorbit coupling not only changes the number of half-skyrmion in the system,but also controls the symmetry of half-skyrmion with circular distribution.As the rotation frequency increases,the system undergoes the transitions from the plane wave to the half-skyrmion chain with circular distribution,and eventually developing the half-skyrmion phase of triangular lattice.Next,we examine the effect of spin-independent interaction on spin-orbit coupled rotating spinor Bose-Einstein condensate.As the spin-independent interaction increases,the topological defects in the condensate increase due to the variation of the local magnetic order.We also discuss the influence of well shape on the ground state structure.These topological structures can be detected via the time-of-flight absorption imaging technique.The spin-orbit coupled spinor Bose-Einstein condensate in the toroidal trap is an important quantum platform,which not only opens up a new avenue for exploring the exotic topological structures,but also is crucial for realizing the transitions among different ground states.This work paves the way for futureexploring the topological defects and the corresponding dynamical stability in quantum system subjected to the toroidal trap.