2006/09/06 by Andreas Mielke, Mielke, Andreas
Materials Science · Physics and Astronomy · #FOS: Physical sciences #Magnetism in coordination complexes #Quantum many-body systems #Strongly Correlated Electrons (cond-mat.str-el) #Theoretical and Computational Physics #cond-mat.str-el
paper · pdf · doi:10.48550/arxiv.cond-mat/0609142
8 pages. To be published in J. Phys. A, Math. Gen
openalex publication_date 2006/09/06 · arxiv created 2012/04/03 · arxiv updated 2012/04/04 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
It is well known that the Hubbard model on a line graph has a flat band and ferromagnetic ground states in a certain density range. We show that for a Hubbard model on a line graph of a planar bipartite graph the ferromagnetic ground state is stable if one adds a special contribution to the kinetic energy which lifts the degeneracy of the lowest single particle state. Stability holds for sufficiently strong repulsion U. The model has extended single particle eigenstates, no degeneracy, and no band gap. It is therefore a good candidate for metallic ferromagnetism.