Ultracold Atomic Gases Modulated By Laser And Induced Spin-orbit Coupling Effect

Laser has been applied more and more deeply in industrial production,daily life,science and technology.The application of laser in ultracold atomic gas system can realize laser cooling and trapping of atomic gas,generate different types of atomic potentials and prepare artificial gauge fields.With help of these technologies,topological superconductivity,superfluid,quantum spin Hall effect,supersolid state and other novel quantum phenomena can be simulated in ultracold atomic gases.However,a noteworthy heating effect exists in the generation of artificial gauge field in alkali-metal ultracold atomic gas with less mass.In this paper,a method to induce effective spin-orbit coupling effect in ultracold atomic gas without direct Raman laser coupling is studied through spin-exchange interaction between atoms.In addition to avoiding heating effect of alkali-metal ultracold atomic gas with less mass,effective spin-orbit coupling with spatial modulated intensity of target ultracold atomic gas is achieved.Firstly,applications of laser in ultracold atomic gas are introduced.Ultracold atomic gas is prepared by laser cooling,laser trapping and evaporative cooling.Taking three-level system as an example,artificial gauge field in ultracold atomic gas is introduced and dynamic characteristics of neutral atoms in artificial gauge field are analyzed.Based on two-photon Raman process,linear spin-orbit coupling scheme is introduced and characteristics of single particle spectrum are analyzed.Secondly,two-atom system composed of different neutral atoms is studied.Spin-exchange interaction exists between atom with spin-orbit coupling and atom without spin-orbit coupling.For the two-atom system,correlation function between two kinds of atoms is calculated,entanglement properties between different degrees of freedom of target ultracold atom under spin-exchange interaction are verified.The symmetry characteristics of two-atom system are analyzed and ground state degeneracy properties of system are studied.Calculating probability distribution curves of neutral atom without direct spin-orbit coupling varied with momentum and spin shows that spin and momentum degrees of freedom of neutral atom are obviously coupled.Finally,based on Gross-Pitaevskii equation satisfied by dynamic characteristics of the mixed gas under mean field approximation,second order central difference method and imaginary time evolution method are utilized to solve the ground state of mixed ultracold atomic Bose gases.Based on quantum states of the spin-orbit coupled Bose-Einstein condensate,the induced spin-orbit coupling effect in mixed Bose-Einstein condensates composed of different kinds of atoms is studied.The influences of external potentials,interatomic interaction intensity and atom number on induced spin-orbit coupled quantum states are analyzed.A method to realize efficient space-dependent spin-orbit coupling distribution in target ultracold atomic gas is proposed.