Atomic beam study of Nb in the vortex state

Truman R. Brown

Karl-Peter Marzlin, Weiping Zhang, Ewan M. Wright

A coherent coupler is proposed to spin a Bose-Einstein condensate composed of ultracold alkali atoms into a vortex state. The proposal is based on a Raman transition induced by two copropagating ${\ensuremath{\sigma}}^{+}$ and ${\ensuremath{\sigma}}^{\ensuremath{-}}$ polarized Laguerre-Gaussian laser beams with different frequencies. We show that the transfer of angular momentum of photons to the condensed atoms through a Raman transition leads to a coherent coupling of the ground-state condensate to a rotating condensate in a vortex state. The detection of such a vortex state is discussed.

L. E. Helseth

P. B. Blakie, R. J. Ballagh, Charles W. Clark

We demonstrate how a topological atom laser can be realized by output coupling a trapped vortex state with a Raman scattering process. We find a linearized analytic solution from which a generalized resonance condition for Raman output coupling is developed. Using numerical simulations of a two component Gross-Pitaevskii equation in two and three dimensions the output beam from a trapped central vortex state is analyzed for cases of pulsed and continuous coupling where the vortex core is either transverse or parallel to the direction of propagation. We show how the parameters of the Raman light fields control the spatial phase of the output beam.

P. G. Kevrekidis

Anal Bhowmik, Pradip Kumar Mondal, Sonjoy Majumder +1 more

The exchange of orbital angular momentum (OAM) between paraxial optical vortex and a Bose-Einstein condensate (BEC) of atomic gases is well known. In this paper, we develop a theory for the microscopic interaction between matter and an optical vortex beyond paraxial approximation. We show how superposition of vortex states of BEC can be created with a focused optical vortex. Since the polarization or spin angular momentum (SAM) of the optical field is coupled with OAM of the field, in this case, these angular momenta can be transferred to the internal electronic and external center-of-mass motion of atoms provided both the motions are coupled. We propose a scheme for producing the superposition of matter-wave vortices using Gaussian and a focused Laguerre-Gaussian beam. We study how two-photon Rabi frequencies of stimulated Raman transitions vary with focusing angles for different combinations of OAM and SAM of optical states. We demonstrate the formation of vortex-antivortex structure and discuss interference of three vortex states in a BEC.