Novel Quantum States Of Laser-Dressed Ultracold Atoms

According to the theory of quantum optics,laser can not only induce the transition between the levels of the atoms,but also drastically change the level structures and the properties of the eigenfunctions.Taking the atoms and the lasers as a whole,one realizes a laser-dressed atom system.The abundant level structures of the ultracold atomic gases and the progress in laser dressing technology make it possible to realize various new quantum models,and explore exotic states of matter and macroscopic quantum phenomena.In this thesis we focus on the two hot issues in ultracold atomic systems,involving spin-orbit coupling induced by Raman laser dressing and long-range softcore interaction induced by Rydberg dressing.We explore possible novel quantum states and unconventional quantum hydrodynamics by investigating the influences of spin-orbit coupling and long-range soft-core interaction on the ground-state and dynamical properties of the ultracold atom systems.We first study the supersolid phases induced by Rashba spin-orbit coupling and long-range soft-core interactions.We reveal that a dimensionless number,which is defined as the product of the Rashba-ring radius in the momentum space and the blockade radius in the real space,plays a crucial role in determining the ground-state structures.By adjusting the dimensionless number and the interatomic interaction,we predict the type-II stripe phase,which breaks both the time-reversal and spatial translational symmetries,and the two-dimensional supersolid,which breaks the spatial translational symmetry in two directions.We predict that discrete vortices,which breaks the rotational symmetry,and high-order vortices described by a radial quantum number can be stabilized in the unit cells of the supersolid.These exotic vortices have been created in laser beams,but are hard to be realized in a conventional superfluid.We also investigate the rotation of ultracold atomic gases induced by Dresselhuas spin-orbit coupling and Ioffe-Pritchard magnetic field.We demonstrate that the IoffePritchard magnetic field polarizes the local spin,and makes the direction of the spin towards to that of the magnetic field.Because the Dresselhaus spin-orbit coupling couples the spin of the atoms and their orbital movement,this gives rise to particle currents along the azimuthal direction,then induces the rotation of the ultracold atomic gases.We indicate that the Dresselhuas spin-orbit coupling and the Ioffe-Pritchard magnetic field make the system obtain an effective gauge potential along the azimuthal direction.This gauge potential accumulates a Aharonov-Bohm geometric phase factor,and induces the rotation of atoms.This is distinct from the usual rotation induced by artificial gauge magnetic fields,and provides a new system to study the AharonovBohm effects.We observe coaxially arranged annular vortex arrays,which are distinct from the Abrikosov vortex lattice in a conventional superfluid.We also investigate the exotic dynamics of bright solitons in spin-1 Bose-Einstein condensates with the presence of equal Rashba-Dreselhaus spin-orbit coupling.Using the variational ansatz method,we derive the equation of motion,which describes the dynamics of the spin and center of mass of the solitons induced by spin-orbit coupling,and obtain the exact solution.We reveal that the spin-orbit coupling couples the spin and the center-of-mass motion of the soliton.When the spin of the soliton oscillates periodically among the three components,the center of mass will also oscillate periodically in the real space with the same frequency.The oscillation frequency depends on the strengths of the spin-orbit coupling and the Raman coupling.The validity of the variational ansatz method has also been verified by direct numerical simulations based on the Gross-Pitaevskii equation.The present investigation deepens the understanding of spin-orbit coupling,supersolid,vortex and soliton,and predict various exotic quantum states,such as supersolid,discrete vortex and high-order vortex.This provides a theoretical basis for quantum simulation and precision measurement based on ultracold atoms.