Vortex Coupler for Atomic Bose-Einstein Condensates

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 {sigma}{sup +} and {sigma}{sup {minus}} 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. {copyright} {ital 1997} {ital The American Physical Society}