Bogoliubov theory for mutually coherent hybrid atomic molecular condensates: Quasiparticles and superchemistry

Abstract

We investigate the equilibrium properties of a hybrid atomic and molecular Bose-Einstein condensate in the context of the Feshbach-resonant quantum many-body model. We analyze fully the mean-field solutions of the system for a general choice of interaction parameters. The quantum fluctuations of the system are obtained from the Bogoliubov theory that characterizes the quasiparticle excitations of the system. In particular we find that the excitation energies have two branches: a Goldstone mode and a second one containing a gap. Both gap energy and phonon velocities are functions of the composition, and our analysis indicates that for a large range of parameter space the system is unstable near a Feshbach resonance.