STRUCTURE AND DYNAMICS OF DEFECTS IN 2D COMPLEX VECTOR FIELD

Minimal orbits of the energy functional of a complex 2D vector field may belong to the strata with different topology, depending on the sign of nonlinear terms breaking the SU(2) symmetry. This gives rise to either linearly or circularly polarized states (LP and CP), which possess different sets of defects. The CP vortices have two alternative core structures, with either vanishing amplitude or reversed polarization in the inner core. In the LP state, there are two topological charges associated with the rotation of either argument or director. Vortices carrying a unit argument or director charge have a ''punched'' core with a vanishing amplitude, while vortices carrying two half-unit charges have a circularly polarized core. The punched core structure is unstable when the symmetry breaking is not sufficiently strong. In the CP state, this leads to transition to the alternative repolarized structure, while in the LP state it signals splitting of unit-charged vortices into a pair of half-unit-charged vortices. Vortices separated by distances large compared to the core size interact in the same way as vortices in a complex scalar field, and interactions due to argument and director charges are independent to the leading order.