Investigation of 3D-Quantized Ring Vortices in Rotating Coupled Atom-Molecular BEC

Abstract

We study the coupled atom-molecular quantized ring vortices of 87Rb Bose-Einstein Condensates (BEC) trapped in a rotating three dimensional (3D) anisotropic cylindrical trap both in time independent and time-dependent Gross-Pitaevskii approaches. For atom to molecular conversion and vice-versa 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 (nz) quantum numbers at a fixed azimuthal quantum number l=2, give rise to different structure 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 presence and absence of external decays is the signature of coherence due to the atom-molecular coupling. This coherence is also implemented in the evolution of coupled atomic and molecular vortices. Intensity of molecular ring vortices grows with progress in time in 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 oscillation out of phase during evolution. Dependence of the atom-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 formation of atom-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.