Multi-mode dynamics of a coupled ultracold atomic-molecular system

We analyze the coherent multi-mode dynamics of a system of coupled atomic and molecular Bose gases. Starting from an atomic Bose-Einstein condensate with a small thermal component, we observe a complete depletion of the atomic and molecular condensate modes on a short time scale due to significant population of excited states. Giant coherent oscillations between the two condensates for typical parameters are almost completely suppressed. Our results cast serious doubts on the common use of the 2-mode model for description of coupled ultracold atomic-molecular systems and should be considered when planning future experiments with ultracold molecules.