The Josephson frequency of resonantly coupled atomic and molecular condensates

Abstract

Motivated by recent experiments (Claussen et al 2003 Preprint cond-mat/0302195) we investigate the magnetic-field dependence of the Josephson frequency of coherent atom–molecule oscillations near a Feshbach resonance. Far off resonance this frequency is determined by two-atom physics. However, the Josephson frequency is relatively large in this case and a description purely in terms of scattering lengths turns out to be inadequate. In particular, we have to include the effective range parameter of the interatomic interaction in our calculations. Close to resonance, the frequency deviates from the two-body results due to various many-body shifts. Considering also the many-body effects, we find perfect agreement with the experimental results over the entire range of magnetic field.