Achieving ground-state polar molecular condensates by chainwise atom-molecule adiabatic passage

We generalize the idea of chainwise stimulated Raman adiabatic passage (STIRAP) [Kuznetsova \textit{et al.} Phys. Rev. A \textbf{78}, 021402(R) (2008)] to a photoassociation-based chainwise atom-molecule system, with the goal of directly converting two-species atomic Bose-Einstein condensates (BEC) into a ground polar molecular BEC. We pay particular attention to the intermediate Raman laser fields, a control knob inaccessible to the usual three-level model. We find that an appropriate exploration of both the intermediate laser fields and the stability property of the atom-molecule STIRAP can greatly reduce the power demand on the photoassociation laser, a key concern for STIRAPs starting from free atoms due to the small Franck-Condon factor in the free-bound transition.