Correlated versus Ferromagnetic State in Repulsively Interacting Two-Component Fermi Gases

TL;DR

This paper critically examines experimental claims of ferromagnetism in repulsively interacting two-component Fermi gases, arguing that observed phenomena could also be explained by strongly correlated non-magnetic states, highlighting the need for domain observation.

Contribution

The paper clarifies that current experiments cannot definitively distinguish ferromagnetic states from correlated non-magnetic states in Fermi gases.

Findings

Experimental results are inconclusive for ferromagnetism

Observation of ferromagnetic domains is essential for confirmation

Current data can be explained by non-magnetic correlations

Abstract

Whether a spin-1/2 Fermi gas will become ferromagnetic as the strength of repulsive interaction increases is a long-standing controversial issue. Recently this problem is studied experimentally by Jo et al, Science, 325, 1521 (2009) in which the authors claim a ferromagnetic transition is observed. This work is to point out the results of this experiment can not distinguish whether the system is in a ferromagnetic state or in a non-magnetic but strongly short-range correlated state. A conclusive experimental demonstration of ferromagnetism relies on the observation of ferromagnetic domains.