The phase transition in ground state configurations of a vortex lattice in an AMBEC

We study the ground state vortex configurations in a trapped atomic-molecular Bose-Einstein condensate with nontrivial angular momentum imposed in the system. We have confirmed a zero-temparature phase transition in the ground state vortex configurations between a rectangular lattice and a triangular paired vortex configuration, with rotational speed of the condensate as a parameter, analytically and numerically. A new type of dynamics involving the paired vortex lattice is also discussed.