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Stability of ferromagnetism in the Hubbard model on the kagomé lattice

Akinori Tanaka·Hiromitsu Ueda
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Abstract

The Hubbard model on the kagomé lattice has highly degenerate ground states (the flat lowest band) in the corresponding single-electron problem and exhibits the so-called flat-band ferromagnetism in the many-electron ground states as was found by Mielke. Here we study the model obtained by adding extra hopping terms to the above model. The lowest single-electron band becomes dispersive, and there is no band gap between the lowest band and the other band. We prove that, at half-filling of the lowest band, the ground states of this perturbed model remain saturated ferromagnetic if the lowest band is nearly flat.

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Akinori Tanaka, Hiromitsu Ueda. 2002-09-18. Stability of ferromagnetism in the Hubbard model on the kagomé lattice. https://doi.org/10.1103/physrevlett.90.067204

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