Itinerant ferromagnetism in a Fermi gas with contact interaction: Magnetic properties in a dilute Hubbard model

TL;DR

This study uses advanced quantum Monte Carlo simulations to investigate the magnetic properties of a dilute Hubbard model, finding no evidence of ferromagnetic phase transition and supporting a paramagnetic Fermi liquid ground state.

Contribution

It provides the first comprehensive quantum Monte Carlo analysis of itinerant ferromagnetism in a dilute Hubbard model with contact interactions.

Findings

No ferromagnetic phase transition observed.

Ground state consistent with a paramagnetic Fermi liquid.

Finite-size effects minimized with large lattices.

Abstract

Ground state properties of the repulsive Hubbard model on a cubic lattice are investigated by means of the auxiliary-field quantum Monte Carlo method. We focus on low-density systems with varying on-site interaction $U/t$, as a model relevant to recent experiments on itinerant ferromagnetism in a dilute Fermi gas with contact interaction. Twist-average boundary conditions are used to eliminate open-shell effects and large lattice sizes are studied to reduce finite-size effects. The sign problem is controlled by a generalized constrained path approximation. We find no ferromagnetic phase transition in this model. The ground-state correlations are consistent with those of a paramagnetic Fermi liquid.