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Ferromagnetism in multi--band Hubbard models: From weak to strong Coulomb repulsion

Karlo Penc·Hiroyuki Shiba·Frédéric Mila·Takuya Tsukagoshi
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Abstract

We propose a new mechanism which can lead to ferromagnetism in Hubbard models containing triangles with different on-site energies. It is based on an effective Hamiltonian that we derive in the strong coupling limit. Considering a one-dimensional realization of the model, we show that in the quarter-filled, insulating case the ground-state is actually ferromagnetic in a very large parameter range going from Tasaki's flat-band limit to the strong coupling limit of the effective Hamiltonian. This result has been obtained using a variety of analytical and numerical techniques. Finally, the same results are shown to apply away from quarter-filling, in the metallic case.

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Karlo Penc, Hiroyuki Shiba, Frédéric Mila, Takuya Tsukagoshi. 1996-03-06. Ferromagnetism in multi--band Hubbard models: From weak to strong Coulomb repulsion. https://doi.org/10.1103/physrevb.54.4056

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