Ferromagnetism in single-band Hubbard models with a partially flat band

TL;DR

This paper demonstrates that a single-band Hubbard model with a partially flat band exhibits ferromagnetic ground states, suggesting a potential pathway to metallic ferromagnetism in such models.

Contribution

It establishes that local stability of ferromagnetism ensures its global stability in these models, linking ferromagnetism to metallic behavior.

Findings

Ferromagnetic ground states are present in the model.

Local stability implies global stability of ferromagnetism.

Potential for metallic ferromagnetism in single-band Hubbard models.

Abstract

A Hubbard model with a single, partially flat band has ferromagnetic ground states. It is shown that local stability of ferromagnetism implies its global stability in such a model: The model has only ferromagnetic ground states if there are no single spin-flip ground states. Since a single-band Hubbard model away from half filling describes a metal, this result may open a route to metallic ferromagnetism in single band Hubbard models.