Existence and stability of atomic-molecular Bose-Einstein condensates
  We analyze the model of an atomic Bose-Einstein condensate (BEC) parametrically coupled to a molecular BEC via a photoassociation process. We show that an interplay of nonlinear inter- and intra-species interactions leads to the formation of mutually trapped states of a hybrid condensate, which are spatially localized even without a trap. The untrapped atomic-molecular condensates with a large number of atoms in either fraction are shown to be dynamically stable in the framework of a mean field theory. 
Benedict J. Cusack, Tristram J. Alexander, Elena A. Ostrovskaya, and   Yuri S. Kivshar