Vortices in Quantum Spin Systems

We examine spin vortices in ferromagnetic quantum Heisenberg models with planar anisotropy on two–dimensional lattices. The symmetry properties and the time evolution of vortices built up from spin–coherent states are studied in detail. Although these states show a dispersion typical for wave packets, important features of classical vortices are conserved. Moreover, the results on symmetry properties provide a construction scheme for vortex–like excitations from exact eigenstates, which have a well–controlled time evolution. Our approach works for arbitrary spin length both on triangular and square lattices. PACS numbers: 75.10.Jm, 75.10.Hk