The itinerant ferromagnetic phase of the Hubbard model

TL;DR

This paper demonstrates the stability of itinerant ferromagnetism in the high-density regime of the 2D Hubbard model using quantum Monte Carlo, revealing a phase transition and supporting the kinetic mechanism of ferromagnetism.

Contribution

It introduces a new quantum Monte Carlo method to establish the stability of ferromagnetic phases in the Hubbard model, highlighting a phase transition and the role of degeneracy.

Findings

Stable saturated ferromagnetic phase at high density.

Discontinuous transition to paramagnetic phase with diverging susceptibility.

Supports kinetic mechanism for itinerant ferromagnetism.

Abstract

Using a newly developed quantum Monte Carlo technique, we provide strong evidence for the stability of a saturated ferromagnetic phase in the high-density regime of the two-dimensional infinite-U Hubbard model. By decreasing the electron density, a discontinuous transition to a paramagnetic phase is observed, accompanied by a divergence of the susceptibility on the paramagnetic side. This behavior, resulting from a high degeneracy among different spin sectors, is consistent with an infinite-order phase transition. The remarkable stability of itinerant ferromagnetism renews the hope to describe this phenomenon within a purely kinetic mechanism and will facilitate the validation of experimental quantum simulators with cold atoms loaded in optical lattices.