Itinerant ferromagnetism of a repulsive atomic Fermi gas: a quantum Monte Carlo study

Abstract

We investigate the phase diagram of a two-component repulsive Fermi gas at T=0 by means of quantum Monte Carlo simulations. For a given value of the positive s-wave scattering length, both purely repulsive and purely attractive model potentials are considered in order to analyze the limits of the universal regime where the details of interatomic forces can be neglected. The equation of state of both balanced and unbalanced systems is calculated as a function of the interaction strength and the critical density for the onset of ferromagnetism is determined. The energy per particle of the strongly polarized gas is calculated and parametrized in terms of the physical properties of repulsive polarons, which are relevant for the stability of the fully magnetized ferromagnetic state. Finally, we analyze the phase diagram in the polarization/interaction plane under the assumption that only phases with homogeneous magnetization can be produced.