Vortex, Skyrmion, and elliptical domain-wall textures in the two-dimensional Hubbard model

The spin and charge texture around doped holes in the two-dimensional Hubba rd model is calculated within an unrestricted spin rotational invariant sla ve-boson approach. In the first part, we examine in detail the spin structu re around two holes doped in the half-filled system where we have studied c luster sizes up to 10 X 10. It turns out that the most stable configuration corresponds to a vortex-antivortex pair that has lower energy than the Nee l-type bipolaron even when one takes the far field contribution into accoun t. We also obtain Skyrmions as local minima of the energy functional but wi th higher total energy than the vortex solutions. Additionally, we have inv estigated the stability of elliptical domain walls for commensurate hole co ncentrations. We find that (i) these phases correspond to local minima of t he energy functional only in case of partially filled walls, (ii) elliptica l domain walls are only stable in the low-doping regime. [S0163-1829(98)016 47-6].