Topological doping of repulsive Hubbard models

The spin configuration induced by single holes and hole pairs doped into stoichiometric, antiferromagnetic cuprates is considered. Unrestricted Hartree–Fock calculations for the three-band Hubbard model are employed to study spinpolaron and vortex-like (meron) solutions. Meron solutions for a single hole are found to be metastable with higher energy than spin polarons. We observe that the meron solution shifts from site-centered to bond-centered as the interaction is increased. Meron–antimeron solutions for hole pairs are found to be unstable. The results are in agreement with earlier findings for the one-band Hubbard model. However, we find that the Hubbard interaction of the one-band model has to be chosen similar to the one of the three-band model to obtain comparable results, not of the order of the charge-transfer gap, as previously expected. r 2003 Elsevier B.V. All rights reserved. PACS: 74.72. h; 75.50.Ee; 71.27.+a