Observation of metastable states in spinor Bose-Einstein condensates
  Bose-Einstein condensates have been prepared in long-lived metastable excited states. Two complementary types of metastable states were observed. The first is due to the immiscibility of multiple components in the condensate, and the second to local suppression of spin-relaxation collisions. Relaxation via re-condensation of non-condensed atoms, spin relaxation, and quantum tunneling was observed. These experiments were done with F=1 spinor Bose-Einstein condensates of sodium confined in an optical dipole trap. 
H.-J. Miesner, D.M. Stamper-Kurn, J. Stenger, S. Inouye, A. Chikkatur,   and W. Ketterle