Ferromagnetic Ground State of Two-Band Hubbard Model with One Electron per Site |
| J. Schulenburg and J. Richter Institut für Theoretische Physik, Universität Magdeburg, P.O. Box 4120, 39016 Magdeburg, Germany |
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| We study the multiband mechanism to favour a ferromagnetic insulating ground state within a two-band Hubbard model. Besides perturbation theory we use exact diagonalization studies to examine the ground state of chains and 2D-lattices. According to second order perturbation theory the exact diagonalization yields a fully polarized ferromagnetic ground state, if the hopping between two ground state orbitals of neighbouring atoms tgg is small and the hopping between a ground state orbital and an excited orbital tge dominates. However, in contrast to the suggestion from the second order perturbation theory this ferromagnetic state is stable only for very small hopping integrals U≫ tge>tgg. For larger t ge quantum interference effects lead to complex magnetic structures. |
| DOI: 10.12693/APhysPolA.91.367 PACS numbers: 75.10.Lp, 75.30.Et, 75.40.Mg, 75.50.Dd |