Rotational Fluxons of Bose-Einstein Condensates in Coplanar Double-Ring   Traps
  Rotational analogs to magnetic fluxons in conventional Josephson junctions are predicted to emerge in the ground state of rotating tunnel-coupled annular Bose-Einstein condensates (BECs). Such topological condensate-phase structures can be manipulated by external potentials. We determine conditions for observing macroscopic quantum tunneling of a fluxon. Rotational fluxons in double-ring BECs can be created, manipulated, and controlled by external potential in different ways than possible in the solid state system, thus rendering them a promising new candidate system for studying and utilizing quantum properties of collective many-particle degrees of freedom. 
J. Brand, T. J. Haigh, U. Z\"ulicke