Many-Body Effects on Nonadiabatic Feshbach Conversion in Bosonic Systems

We investigate the dynamics of converting cold bosonic atoms to molecules when an external magnetic field is swept across a Feshbach resonance. Our analysis relies on a zero temperature quantum microscopic model that accounts for many-body effects, triggering the association process. We show that the picture of two-body molecular production depicted by Landau-Zener model is significantly altered due to many-body effects. In nonadiabatic regime, we derive an analytic expression for molecular conversion efficiency that explains the discrepancy between the prediction of Landau-Zener formula and experimental data[Hodby et al., Phys. Rev. Lett. {\bf 94}, 120402 (2005)]. Our theory is further extended to the formation of heteronuclear diatomic molecules and gives some interesting predictions.