NUMERICAL STUDY OF VORTICES IN A 2-DIMENSIONAL XY MODEL WITH INPLANE MAGNETIC-FIELD

Many physical systems of interest can be mapped into the planar rotato r and XY magnetic models with a magnetic field applied within the easy plane. In this work we study how the shape and energy of a vortex-ant ivortex pair depends on the applied field and on the pair separation. Our results show a new feature: the energy related to the vortex-antiv ortex pair has a coefficient which depends strongly on the applied fie ld. For large separation of the pair, the energy increases roughly wit h the square root of the field and linearly with the pair separation.