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arXiv · 1205.0425

Magnetic transitions in strong coupling expansions for nearly degenerate states

Raymond Fresard·Christian Hackenberger·Thilo Kopp
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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.

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Raymond Fresard, Christian Hackenberger, Thilo Kopp. 2012-05-14. Magnetic transitions in strong coupling expansions for nearly degenerate states. https://doi.org/10.1002/andp.201200031

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