A repulsive atomic gas in a harmonic trap on the border of itinerant ferromagnetism

TL;DR

This paper investigates the behavior of a repulsive atomic Fermi gas near ferromagnetism, proposing a non-equilibrium model that aligns well with experimental observations of phase transitions influenced by magnetic defects and losses.

Contribution

It introduces a non-equilibrium theoretical framework accounting for defect dynamics and losses, explaining experimental results on ferromagnetic transition in ultracold Fermi gases.

Findings

The adiabatic transition occurs at weaker interactions than observed experimentally.

The non-equilibrium model quantitatively matches experimental data.

Magnetic defects and three-body losses significantly influence phase behavior.

Abstract

Alongside superfluidity, itinerant (Stoner) ferromagnetism remains one of the most well-characterized phases of correlated Fermi systems. A recent experiment has reported the first evidence for novel phase behavior on the repulsive side of the Feshbach resonance in a two-component ultracold Fermi gas. By adapting recent theoretical studies to the atomic trap geometry, we show that an adiabatic ferromagnetic transition would take place at a weaker interaction strength than is observed in experiment. This discrepancy motivates a simple non-equilibrium theory that takes account of the dynamics of magnetic defects and three-body losses. The formalism developed displays good quantitative agreement with experiment.