Using laser beams to generate gauge potentials in cold atoms provides an opportunity to study interesting quantum phenomena in condensed matter physics. In this thesis, a scheme to manipulate atomic wave functions and generate spin current in a trapped BEC—whose ground state can be freely controlled to be a vortex or non-vortex state—has been studied and discussed. Laguerre-Gaussian beams, which carry non-zero orbital angular momentum, can be used to create coupling between the 2³S₁ and 2³P₁ states in ⁴He atoms. Wavefunctions in atoms interacting with these beams have been expressed in new dressed states. For atoms moving adiabatically, the coupling among the dressed states can be neglected through adiabatic approximation and centre of mass of atoms would experience both effective vecto...[ Read more ]

Using laser beams to generate gauge potentials in cold atoms provides an opportunity to study interesting quantum phenomena in condensed matter physics. In this thesis, a scheme to manipulate atomic wave functions and generate spin current in a trapped BEC—whose ground state can be freely controlled to be a vortex or non-vortex state—has been studied and discussed. Laguerre-Gaussian beams, which carry non-zero orbital angular momentum, can be used to create coupling between the 2³S₁ and 2³P₁ states in ⁴He atoms. Wavefunctions in atoms interacting with these beams have been expressed in new dressed states. For atoms moving adiabatically, the coupling among the dressed states can be neglected through adiabatic approximation and centre of mass of atoms would experience both effective vector potential and effective scalar potential. The eigenenergies and wavefunctions of a single atom have been calculated by computational methods. In addition, the ground-state energies, wavefunctions and spin current of many-body systems, in which the non-linear Gross-Pitaevskii particle-particle interaction is included, have been found. Comparing the result of a many-body system and those in the single particle system, the wavefunctions of the many-body system spread over a larger region than that in the single particle system, causing a significant difference in their spin current density. Also, the ground-state energy per particle in the many-body system is higher than that in the single particle system.