Quantum Tunneling across Spin Domains in a Bose-Einstein Condensate

Quantum tunneling was observed in the decay of metastable spin domains in gaseous Bose-Einstein condensates. A mean-field description of the tunneling was developed and compared with measurement. The tunneling rates are a sensitive probe of the boundary between spin domains, and indicate a spin structure which is prohibited in the bulk fluid. These experiments were performed with optically trapped $F=1\mathrm{}$ spinor Bose-Einstein condensates of sodium.