We experimentally studied the spin-dependent collision dynamics of 87 Rb spin-2 Bose-Einstein condensates confined in an optical trap. The condensed atoms were initially populated in the ͉F =2,m F =0͘ state, and their time evolutions in the trap were measured in the presence of external magnetic field strengths ranging from 0.1 to 3.0 G. The atom loss rate due to inelastic two-body collisions was found to be 1.4͑2͒ ϫ 10 −13 cm 3 s −1 . Spin mixing in the F = 2 manifold developed dramatically for the first few tens of milliseconds, and the oscillations in the population distribution between different magnetic components were observed over a limited range of magnetic field strengths. The antiferromagnetic property of this system was deduced from the magnetic field dependence on the evolution of relative populations for each m F component.

No abstract

We have succeeded in magneto-optical trapping of Yb atoms decelerated by a Zeeman slower method. The number of the trapped atoms is more than about 1.3ϫ10 6 measured by light absorption. We have found the evidence of the branching from the 1 P 1 excited state to triplet states, and determined the lower limit on the branching ratio to be 1.2ϫ10 Ϫ7 .

We have succeeded in trapping a high density of rare-earth atom of ytterbium (Yb) in a crossed far-off resonance trap. The peak density reaches more than 10(14) cm(-3). With a new method of a delayed crossed far-off resonance trap, we have elucidated that the atoms became concentrated into the cross region by atom-atom collisions. We trap fermionic Yb atoms in the same way as bosonic ones.

We studied the dynamics of quadruply quantized vortices in 87 Rb Bose-Einstein condensates. Vortices were created in magnetically trapped condensates with hyperfine spin F ¼ 2 by employing topological phase imprinting technique, wherein the direction of atomic spin is adiabatically reversed by applying a bias magnetic field. Vortices were observed for a holding time of up to 10 ms. Disappearance of the vortices was attributed to considerable expansion and excitation of the condensates, which were caused by the distortion of the magnetic potential. In order to observe the long-term behavior of the vortices, we transferred the condensates to a crossed-type optical dipole force trap after creating the vortices. In this case, the vortices were observed for a holding time of up to 22 ms. We also observed density profiles, which indicated the presence of split vortices.