Ferromagnetism in a Repulsive Atomic Fermi Gas with Correlated Disorder

TL;DR

This study explores how correlated disorder influences ferromagnetic transitions in a two-component repulsive Fermi gas, revealing disorder-induced enhancement of ferromagnetism and shifts in transition points.

Contribution

It provides the first quantum Monte Carlo analysis of ferromagnetism in a disordered Fermi gas near the Anderson transition, highlighting disorder's role in magnetic phase transitions.

Findings

Disorder suppresses magnetic susceptibility at weak interactions.

Susceptibility diverges at weaker interactions due to disorder.

Disorder favors transitions to ferromagnetic phases.

Abstract

We investigate the zero-temperature ferromagnetic behavior of a two-component repulsive Fermi gas in the presence of a correlated random field that represents an optical speckle pattern. The density is tuned so that the (noninteracting) Fermi energy is close to the mobility edge of the Anderson localization transition. We employ quantum Monte Carlo simulations to determine various ground-state properties, including the equation of state, the magnetic susceptibility, and the energy of an impurity immersed in a polarized Fermi gas (repulsive polaron). In the weakly interacting limit, the magnetic susceptibility is found to be suppressed by disorder. However, it rapidly increases with the interaction strength, and it diverges at a much weaker interaction strength compared to the clean gas. Both the transition from the paramagnetic phase to the partially ferromagnetic phase, and the one from the partially to the fully ferromagnetic phase are strongly favored by disorder, indicating a case of order induced by disorder.