Theory of a mode-locked atom laser with toroidal geometry - art. no. 053602

We consider a possible technique for mode locking an atom laser, based on t he generation of a dark soliton in a ring-shaped Bose-Einstein condensate, with repulsive atomic interactions. The soliton is a kink, with angular mom entum per particle equal to (h) over bar /2. It emerges naturally when the condensate is stirred at the soliton velocity and cleansed with a periodic out coupler. The result is a replicating coherent field inside the atom las er, stabilized by topology. We give a numerical demonstration of the genera tion and stabilization of the soliton.