Collective chemical reactions and domain wall dynamics in an atomic Bose-Einstein condensate

Chemical reactions in the quantum degenerate regime proceed in a different manner than those of a thermal gas. At ultralow temperatures, quantum statistics can determine the chemical kinetics. We report on the formation of molecules from an atomic Bose-Einstein condensate (BEC) near a g-wave Feshbach resonance. The molecular formation rate below critical temperature greatly differs compared to the thermal regime where the chemical kinetics are affected by atom collisions.  When we induce a transition from atoms to molecules in the quantum degenerate regime, the molecular population oscillates at the frequency determined by the molecular binding energy. Our work demonstrates the quantum coherence of collective chemical reactions in a strongly interacting Bose gas.

 

In our second work, we investigate dynamics of domain walls in a BEC under a density-dependent gauge field. The density-dependent gauge field is created by modulation of the lattice potential and interatomic interactions which results in the creation of domains with different momenta. We observe the formation of domain walls due to the inhomogeneity of the atomic cloud density. We also study the dynamics of the domain walls in response to a synthetic electric field. By treating the domain walls as elementary excitations, we find the acceleration of the domain wall is twice as that of bare atoms and moves in the opposite direction.