Investigation into 3D-quantized ring vortices in rotating coupled atomic-molecular BEC

摘要

We study the coupled atomic-molecular quantized ring vortices of Rb-87 Bose-Einstein condensates trapped in a rotating 3D anisotropic cylindrical trap using both time-independent and time-dependent Gross-Pitaevskii approaches. For atomic to molecular conversion and vice versa, a two-photon Raman photoassociation scheme has been used. Atomic and molecular stationary state solutions show that the different number of nodes and crests formed in the density profile (as a function of r and z) for different combinations of radial (n) and axial (n(z)) quantum numbers at a fixed azimuthal quantum number l = 2, give rise to different structures around the 3D ring vortex centered at r = 0. We have considered both spontaneous and induced decays and compared the results with those without considering the decays. The out-of-phase oscillation of atomic and molecular numbers in two vortex states, both in the presence and absence of external decays, is the signature of coherence due to the atomic-molecular coupling. This coherence is also implemented in the evolution of coupled atomic and molecular vortices. The intensity of molecular ring vortices grows with time at the expense of that of atomic ring vortices, and vice versa. It is found that the intensity of the coupled atomic and molecular ring vortices starts to oscillate out of phase during evolution. Dependence of the atomic-molecular conversion efficiency and the lifetime of the system on the laser intensity of photoassociation lasers and the total number of atoms in two different vortex states reveals that the formation of atomic-molecular coupled vortices and the efficiency of formation can be controlled by varying these parameters. Linear stability analysis of vortex states as a function of different system parameters shows that the atomic vortices are more stable than molecular vortices, and the stable atomic and molecular vortices can be achieved by controlling these parameters.