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Ferromagnetism in an itinerant electron system: Hubbard model on complete graph

D. F. Wang
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Abstract

In this work, the ground states of the Hubbard model on complete graph are studied, for a finite lattice size $L$ and arbitrary on-site energy $U$. We construct explicitly the ground states of the system when the number of the electrons $N_e \ge L+1$. In particular, for $N_e=L+1$, the ground state is ferromagnetic with total spin $s_g=(N_e-2)/2$.

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D. F. Wang. 1996-04-18. Ferromagnetism in an itinerant electron system: Hubbard model on complete graph. https://arxiv.org/abs/cond-mat/9604121

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