Flat-band ferromagnetism induced by off-site repulsions

TL;DR

This paper investigates how adding off-site repulsions influences flat-band ferromagnetism in 1D lattice models, revealing a phase diagram where off-site interactions can promote ferromagnetic order at lower on-site repulsions.

Contribution

It demonstrates that off-site repulsions can enhance ferromagnetism in 1D Hubbard models, providing new insights into electron correlation effects in frustrated lattices.

Findings

Off-site repulsions reduce the critical on-site repulsion needed for ferromagnetism.

A phase diagram illustrating the influence of off-site interactions on ferromagnetic regions.

Ferromagnetism is stabilized in certain parameter regimes due to off-site repulsions.

Abstract

Density matrix renormalization group method is used to analyze how the nearest-neighbor repulsion V added to the Hubbard model on 1D triangular lattice and a railway trestle (t-t') model will affect the electron-correlation dominated ferromagnetism arising from the interference (frustration). Obtained phase diagram shows that there is a region in smaller-t' side where the critical on-site repulsion above which the system becomes ferromagnetic is reduced when the off-site repulsion is introduced.