非线性相互作用的自旋-轨道耦合玻色-爱因斯坦凝聚体的淬火动力学

Quench dynamics of a spin-orbital coupled Bose-Einstein condensate with nonlinear interactions

研究了在二维自旋-轨道耦合的相互作用超冷玻色气体中存在一维光晶格时,超流条纹相到超固相的非平衡动力学.通过研究这一动力学过程中的缺陷(位相空间中的涡旋)及波函数的变化行为,利用涡旋数及波函数的交叠等描述方法,确定了考虑光晶格深度随时间线性变化的量子淬火动力学过程的转变时间.发现在转变时间之前,体系对于淬火过程没有响应.当演化时间超过转变时间后,系统开始迅速响应,涡旋数及体系的波函数开始迅速变化.当演化时间足够长时,系统将达到稳态.另外还发现,在上述动力学过程中,由于体系中自旋-轨道耦合的存在,系统在空间中的密度分布与自旋在空间中的结构始终相伴生,即具有拓扑结构的磁斯格明子(反斯格明子)的中心位置始终与体系密度分布的极小值位置相对应.

In this work,we study the non-equilibrium quench dynamics from the superfluid stripe phase to the supersolid phase of a two dimensional spin-orbital coupled interacting Bose-Einstein condensate in the presence of a one dimensional optical lattice.The quench protocol here is constructed through varying the lattice depth linearly with the evolution time.By using the time-dependent Gutzwiller method,various physical quantities,such as the vortex number and the overlap of wave-function,have been investigated with respect to the quench time.Through analyzing the dynamical behavior of the above physical quantities,we find out the transition time of the quench procedure,which captures the freeze out time indicating the moment that the system catches the quench speed beginning to evolve quickly.Before the transition time,the dynamics is frozen and the state of the system cannot follow the changes in the Hamiltonian.While passing the transition time,we find that there are significant alterations to both the vortex number and the wave-function.At the transition time,on one hand the vortex number abruptly increases from zero;on the other hand the overlap of wave-function departures from 1 shortly.These signatures indicate that the system evolves rapidly when passing the transition time.Furthermore,we also find that due to the presence of spin-orbital coupling,the spin texture represents a periodic magnetic structure accompanying with the emergence of the supersolid dynamically.It is shown that during the quench procedure,the density distribution of the system are always accompanied with the spatial structure of spin texture,i.e.,the central position of topological spin skyrmion(antiskyrmion)corresponding to the minimum position of the density distribution.The topological charge of the above spin structures also shows interesting dynamical properties.We find that the quantized topological charge appears with the emergence of the supersolid dynamically.