The Study On The Physical Property Of Spin-orbit Coupled Dipolar Cold Atom Gases

In the field of optical lattice clock,the physical character of the cold atom provides us the theoretical guidance for the study of influencing factors on optical clock quality,and for the selection of the optical lattice clock atom source.It also point out a correct direction for using optical clock experimental platform to study extensive physical problems and enlarging the application scope of it.The ground state structure and dynamics are the two main ways demonstrating the physical character of cold atom gases.Exploring the ground state and dynamics of the cold atom gases in different conditions will strongly support the experimental physicists to master the ways of quantum manipulation.In this dissertation,we will perform the detailed study on the ground-state structures,dynamics and quantum manipulations of the cold atom gases.Based on the mean field theory,we firstly obtain the Gross-Pitaevskii energy equations(Gross-Pitaevskii equations)of the cold atom gases under various conditions.By using a variety of numerical simulation methods,such as the central difference method,image-time propagation method,real-time propagation method,time-splitting method,we will investigate the ground-state structures and dynamics of the system.We mainly focus on the effects of tunable interaction,spin-orbit coupling,dipole-dipole interaction,various external potential,and other parameters,on the physical properties of the system.The main content including the following three aspects:(1)The ground-state structures of cold atom gases under adjustable interactions.We mainly focus on the ground-state structures of a two-component cold atom gases confined in a harmonic plus quartic potential.Compared with the case of single-component one,the two-component system possesses inter-component interaction,thus can induce more rich ground-state structures,involving single-line vortices,multi-line vortices,ring phase,stripe phase,rhombus vortex lattice,ring vortex chains.(2)The ground-state structures of the cold atom gases with spin-orbit coupling.We have investigated the ground-state structures of a two-component cold atom gases confined in the extreme elongation harmonic plus quartic potential traps and the concentrically coupled annular traps by means of changing the strength and direction of the spin-orbit coupling.The main results are listed as follow.In the extreme elongation harmonic plus quartic potential traps,we found that the anisotropic spin-orbit coupling can induce various ground state structures,such as stripe,single-line vortices and snakeskin piebald,if the intra-component interactions of the two components are equal to each other.However,if the intra-component interactions are unequal,both the isotropic and anisotropic spin-orbit coupling can induce vortex chain in the centre of the trap,with the residual vortices appearing in pairs.The residual vortices repulse(attract)each other for isotropic(anisotropic)spin-orbit coupling.In the concentrically coupled annular traps,we found that the spin-orbit coupling can manipulate the ground state density distribution into azimuthal phase separation,radial phase separation and phase coexistence,and lead to various vortex structures and spin textures.(3)The ground states and dynamics of cold atom gases with dipole-dipole interaction.We have investigated the ground state of cold atom gases in both non-rotation and rotation cases.In the non-rotation case,the dipole-dipole interaction can control the quantum transition between the radial phase separation and azimuthal phase separation.In the rotation case,it is found that various ground-state phases and the related vortex structures,such as polygonal vortex clusters and vortex necklaces,can be obtained via a proper choice of the dipolar interaction and rotational frequency.We have also considered a rotating two-component Bose–Einstein condensate,which consists of both dipolar and scalar Bose atoms,confined in a harmonic plus optical lattice potential.Our results show that the number of vortices and its related vortex structures of such a system depend strongly on the dipole-dipole interaction.We have also investigated the formation and nonlinear dynamics of vortices in cold atom gases with the presence or absence of dipole-dipole interaction.When the dipole-dipole interaction is absent,we found that vortex shedding can formed in the wake of the moving impenetrable potential.For moderate moving velocity,the shedding period and associated patterns depends on the radius of the potential,and V-shaped,periodic or complex wakes are formed.For high moving velocity,both vortex pair and vortex dipole can be formed simultaneously.It is found that the dipole-dipole interaction can greatly influence the dynamics of vortices when the velocity of potential exceeds some critical value.It can lead to the formation of vortex pairs,vortex dipoles and simple vortex,as well as Karman vortex street.