Itinerant ferromagnetism in dilute SU(N) Fermi gases

TL;DR

This paper provides exact analytic calculations of the energy and magnetic phase transitions in dilute SU(N) Fermi gases, revealing how spin affects the order and critical density of ferromagnetic transitions, with implications for ultracold atom experiments.

Contribution

It extends previous results by including spin polarization effects at second order, offering precise insights into ferromagnetic phase transitions in SU(N) Fermi gases.

Findings

Second-order corrections change the ferromagnetic transition to first-order for spin 1/2.

Higher spins lead to always first-order transitions.

Critical density decreases with increasing spin, easing experimental observation.

Abstract

We present exact analytic results for the energy of a SU(N) repulsive Fermi gas as a function of the spin-channel occupation at second order in the gas parameter. This is an extension of an old result that now incorporates the degree of polarization of the system. Therefore, the magnetic properties of the gas can be obtained, free from numerical uncertainties. For spin 1/2 we find that second-order corrections change the itinerant ferromagnetic transition from continuous to first-order. Instead, for spin larger than 1/2 the phase transition is always of first-order type. The transition critical density reduces when the spin increases, making the phase transition more accessible to experiments with ultracold dilute Fermi gases. Estimations for Fermi gases of Yb and Sr with spin 5/2 and 9/2, respectively, are reported.