Two internal hyperfine states of a Bose-Einstein condensate in a dilute magnetically trapped gas of ${}^{87}\mathrm{Rb}$ atoms are strongly coupled by an external field that drives Rabi oscillations between the internal states. Due to their different magnetic moments and the force of gravity, the trapping potentials for the two states are offset along the vertical axis, so that the dynamics of the internal and external degrees of freedom are inseparable. The rapid cycling between internal atomic states in the displaced traps results in an adiabatic transfer of population from the condensate ground state to its first antisymmetric topological state. This has a pronounced effect on the internal Rabi oscillations, modulating the fringe visibility in a manner reminiscent of collapses and revivals. We present a detailed theoretical description based on zero-temperature mean-field theory.

• Received 28 April 1999

DOI:https://doi.org/10.1103/PhysRevA.61.033612