paper

Ferromagnetism in the Hubbard model with orbital degeneracy in infinite dimensions

arXiv:cond-mat/9804096 · doi:10.1103/PhysRevB.58.R567

Abstract

We study the ferromagnetism due to orbital degeneracy in the Hubbard model in infinite dimensions. The model contains the intraorbital repulsion , the interorbital repulsion , the exchange (Hund coupling) and the pair hopping , where all of them originate from the on-site Coulomb interaction. The ground state of the effective one-site problem was obtained by exact diagonalizations. At the 1/4-filling, we found two insulating phases; one is a ferromagnetic phase with alternating orbital order and the other is antiferromagnetic one with uniform orbital order. If electrons are doped into the 1/4-filling, the ferromagnetic phase still survives and becomes metallic, while the antiferromagnetic phase disappears. This result indicates that the double-exchange mechanism is relevant to stabilize metallic ferromagnetism in infinite dimensions.

4 pages, Revtex, 3 figures, corrected some typos and references, to be published in Phys. Rev. B (Rapid Communication)

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