偶极旋量玻色—爱因斯坦凝聚体中的耦合自旋涡旋对

发布时间：2018-02-02 23:41

本文关键词： 偶极旋量玻色-爱因斯坦凝聚体双势阱平行(反平行)自旋涡旋对淬火动力学　出处：《山西大学》2016年博士论文　论文类型：学位论文

【摘要】：磁涡旋态由于其简单的拓扑结构以及丰富的动力学性质,在未来信息存储和通讯领域具有非常大的潜力。由于偶极相互作用强烈依赖外势的几何形状,能够将自旋自由度和轨道自由度耦合起来,其作用等效于一个有效磁场,使得原子自发地形成自旋涡旋态,类似于纳米磁性材料中的磁涡旋态。我们通过数值求解平均场近似下自旋1偶极旋量BEC的GP方程,研究系统在双势阱中的基态和磁性响应性质,得到两种不同的基态自旋涡旋对结构,并且通过实时演化研究其碰撞动力学和磁场淬火动力学,为实验提供依据。首先,我们研究自旋1偶极旋量BEC束缚在对称双势阱中的基态和磁性响应性质。我们主要研究自旋涡旋态,所以假设势阱在z方向被高度压缩。研究发现,由于双势阱的出现,产生了两种不同的自旋涡旋结构,即平行耦合涡旋对和反平行耦合涡旋对。我们还研究了耦合自旋涡旋对在横向静磁场下的磁响应,发现上下两层涡旋中心随磁场强度的增加而依次消失。其次,我们数值模拟了平均场理论下自旋1偶极旋量BEC系统中耦合自旋涡旋对的碰撞动力学和磁场淬火动力学。当系统制备到双势阱的基态后,突然撤掉双势阱,上下两层的涡旋开始碰撞,而且每次碰撞后两个涡旋的手征发生交换,其密度特征表明耦合平行涡旋对的碰撞是同相碰撞而耦合反平行涡旋对的碰撞是反相碰撞。当突然撤掉磁场后,单层凝聚体的涡旋中心开始做螺旋运动,它在x-y平面上的轨迹为椭圆,在y方向的投影为以固有频率和阻尼率衰减的阻尼振荡。自旋涡旋对的振荡模式可以通过初始磁场的强度以及高斯势垒的高度来调节,如平行涡旋对中两层涡旋的螺旋运动不同步,而反平行涡旋对中涡旋的运动轨迹为双螺旋结构,两层涡旋中心朝着相反的方向运动,但是振荡幅度相同。
[Abstract]:Magnetic vortex states have great potential in the future information storage and communication due to their simple topological structure and rich dynamic properties. The dipole interaction strongly depends on the geometry of the external potential. The spin degree of freedom can be coupled with the orbital degree of freedom, which is equivalent to an effective magnetic field, which makes the atom spontaneously form a spin vortex state. Similar to the magnetic vortex state in nanomagnetic materials, we numerically solve the GP equation of spin 1 dipole BEC in the mean field approximation, and study the ground state and magnetic response of the system in a double potential well. Two different ground state spin-vortex pair structures are obtained, and their collision dynamics and magnetic field quenching dynamics are studied through real time evolution, which provides the basis for the experiment. We study the ground state and magnetic response of the spin 1 dipole BEC binding in a symmetric double potential well. We mainly study the spin vortex state, so we assume that the potential well is highly squeezed in the z direction. It is found that the potential well is highly squeezed in the z direction. There are two different spin-vortex structures, parallel coupled vortex pair and anti-parallel coupled vortex pair. We also study the magnetic response of the coupled spin-vortex pair in the transverse static magnetic field. It is found that the vortex center of the upper and lower layers disappears with the increase of magnetic field intensity. We numerically simulate the collision dynamics and magnetic field quenching dynamics of the coupled spin-vortex pair in the spin 1 dipolar BEC system under the mean field theory. When the ground state of the double potential well is prepared by the system, the double potential well is suddenly removed. The vortex of the upper and lower layers begins to collide and the chiral exchange of the two vortices occurs after each collision. The density characteristics indicate that the collision of coupled parallel vortex pair is the same phase collision, and the collision of coupled antiparallel vortex pair is inverse phase collision. When the magnetic field is suddenly removed, the vortex center of the single layer condensate begins to spiral motion. Its trajectory on the x-y plane is elliptical. The projection in y direction is damping oscillation attenuated by natural frequency and damping rate. The oscillation mode of spin-vortex pair can be adjusted by the intensity of initial magnetic field and the height of Gao Si barrier. For example, the spiral motion of the two layers of the parallel vortex pair is out of sync, while the track of the anti-parallel vortex pair is a double-helical structure. The center of the two layers of vortex moves in the opposite direction, but the oscillation amplitude is the same.
【学位授予单位】：山西大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：O469

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