Abstract

Bose condensates of ultracold atoms with nonzero total spin show ordered phases that combine superfluid and magnetic order in different ways. The topological defects (vortices and their generalizations) in such phases can be directly observed in experiments and are predicted to have some surprising consequences. In the two-dimensional polar condensate of sodium atoms, there is an unusual Berezinskii-Kosterlitz-Thouless transition into a paired phase induced by thermal fluctuations; this talk gives an analytical argument for this scenario as well as Monte Carlo results. In a rotated spinor condensate, the tunable interaction between vortices leads to a complicated vortex lattice phase diagram, including aperiodic structures as well as true lattices. The last part of the talk discusses some open questions raised by current experiments on condensate dynamics.