Creation of a persistent current and vortex in a Bose-Einstein condensate of alkali-metal atoms

It is shown theoretically that a persistent current can be continuously created in a Bose-Einstein condensate (BEC) of alkali-metal atoms confined in a multiply connected region by making use of a spin degree of freedom of the order parameter of a BEC. We demonstrate that this persistent current is easily transformed into a vortex. Relaxation processes of these BEC after the confining field is turned off are also studied, so that our analyses are compared with time-of-flight experiments. The results are shown to clearly reflect the existence of a persistent current.