Topological classification of vortex-core structures of spin-1   Bose-Einstein condensates
  We classify vortex-core structures according to the topology of the order parameter space. By developing a method to characterize how the order parameter changes inside the vortex core. We apply this method to the spin-1 Bose-Einstein condensates and show that the vortex-core structures are classified by winding numbers that are locally defined in the core region. We also show that a vortex-core structure with a nontrivial winding number can be stabilized under a negative quadratic Zeeman effect. 
Shingo Kobayashi, Yuki Kawaguchi, Muneto Nitta, and Masahito Ueda
cond-mat.quant-gas hep-ph hep-th