Spin-spiral instability of the Nagaoka ferromagnet in the crossover between square and triangular lattices

Abstract

We study the hard-core Fermi-Hubbard model in the crossover between square and triangular lattices near half-filling. As was recognized by Nagaoka in the 1960s, on the square lattice the presence of a single hole leads to ferromagnetic spin ordering. On the triangular lattice, geometric frustration instead leads to a spin-singlet ground state, which can be associated with a 120-degree spiral order. On lattices which interpolate between square and triangular, there is a phase transition at which the ferromagnetic order becomes unstable to a spin spiral. We model this transition, finding the exact location of the spin-spiral instability.

9 pages, 2 figures; close to the published version

References in corpus (7)

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• Kinetic Magnetism in Triangular Moiré Materials
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