Two-fermion bound state in a Bose-Einstein condensate
  A nonlinear Schr\"odinger equation is derived for the dynamics of a beam of ultracold fermionic atoms traversing a Bose-Einstein condensate. The condensate phonon modes are shown to provide a nonlinear medium for the fermionic atoms. A two-fermion bound state is predicted to arise, and the signature of the bound state in a nonlinear atom optics experiment is discussed. 
Weiping Zhang, Han Pu, Chris P. Search, Pierre Meystre and E. M.   Wright