Adiabatic Association of Ultracold Molecules via Magnetic Field Tunable Interactions
K Goral, T Koehler, S A. Gardiner, Eite Tiesinga, Paul S. Julienne
We consider in detail the situation of applying a time dependent external magnetic field to a 87Rb atomic Bose-Einstein condensate held in a harmonic trap, in order to adiabatically sweep the interatomic interactions across a Feshbach resonance to produce diatomic molecules. To this end we use the microscopic many-body theory of T. Koehler and K. Burnett [Phys. Rev. A 65, 033601 (2002)]. This approach properly accounts for both the microscopic binary collision physics and the macroscopic coherent nature of the inhomogeneous atomic Bose-Einstein condensate. We explore different, experimentally accessible, parameter regimes, and compare the predictions of Landau-Zener, configuration interaction, and two level mean field calculations with those of the microscopic many-body approach. We find that there can be significant production of burst atoms, i.e. correlated pairs of unbound atoms with comparatively high relative momentum. This stems from the existence of collective excitations induced by the effect of the time dependent magnetic field on the inhomogeneous atomic Bose-Einstein condensate. We therefore show that Landau-Zener, configuration interaction, and two level mean field models, which exclude the possibility of burst production by considering only atomic Bose-Einstein condensate and molecular fractions, omit potentially significant physics, as will homogeneous gas considerations, including local density approximations, as there would be no prediction of collective excitations. We show how, by the appropriate manipulation of experimentally accessible parameters, it is possible to substantially suppress the production of burst atoms, thereby optimizing the possible to approximately regain the idealized predictions for the molecular conversion efficiency given by two level models.
Journal of Physics B-Atomic Molecular and Optical Physics
, Koehler, T.
, Gardiner, S.
, Tiesinga, E.
and Julienne, P.
Adiabatic Association of Ultracold Molecules via Magnetic Field Tunable Interactions, Journal of Physics B-Atomic Molecular and Optical Physics
(Accessed February 22, 2024)