Magnetic transitions in strong coupling expansions for nearly degenerate states
arXiv:1205.0425 · doi:10.1002/andp.201200031
Abstract
We consider a strong coupling expansion for a two-band Hubbard model on two sites with nearly degenerate states. A comparative analysis is performed for different schemes of perturbation theory which are applicable to systems with nearly degenerate states. A fourth order approach which builds on a four-dimensional low-energy subspace with nearly degenerate states captures accurately the transition from an antiferromagnetic to a ferromagnetic ground state at large on-site Coulomb interaction.
arXiv comment15 pages, 6 figures; version corrects typos and other minor mistakes
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