Effects of geometrical frustration on ferromagnetism in the Hubbard model on the Shastry-Sutherland lattice

TL;DR

This study investigates how geometrical frustration influences ferromagnetism in the Hubbard model on the Shastry-Sutherland lattice, revealing that specific frustration parameters stabilize ferromagnetism linked to the density of states shape.

Contribution

It demonstrates that geometrical frustration can stabilize ferromagnetism in the Hubbard model, depending on the shape of the noninteracting density of states, which is a novel insight.

Findings

Ferromagnetism is stabilized at high electron concentrations with specific frustration parameters.

Single peaked density of states at the band edge promotes ferromagnetism.

Multiple peaks in the density of states suppress ferromagnetism.

Abstract

The small-cluster exact-diagonalization calculations and the projector quantum Monte Carlo method are used to examine the competing effects of geometrical frustration and interaction on ferromagnetism in the Hubbard model on the Shastry-Sutherland lattice. It is shown that the geometrical frustration stabilizes the ferromagnetic state at high electron concentrations ($n \gtrsim 7/4$), where strong correlations between ferromagnetism and the shape of the noninteracting density of states are observed. In particular, it is found that ferromagnetism is stabilized only for these values of frustration parameters, which lead to the single peaked noninterating density of states at the band edge. Once, two or more peaks appear in the noninteracting density of states at the band egde the ferromagnetic state is suppressed. This opens a new route towards the understanding of ferromagnetism in strongly correlated systems.