Spin Josephson vortices in two tunnel-coupled spinor Bose gases.

We study topological excitations in spin-one Bose-Einstein condensates trapped in an elongated double-well optical potential. This system hosts a new topological defect, the spin Josephson vortex (SJV), which forms due to the competition between the interwell atomic tunneling and short-range ferromagnetic two-body interaction. We identify the spin structure and formation dynamics of the SJV and determine the phase diagram of the system. By exploiting the intrinsic stability of the SJV, we propose a dynamical method to create SJVs under realistic experimental conditions.