Global superfluid phase diagram of three component fermions with magnetic ordering

TL;DR

This paper explores the complex phase diagram of a three-component fermion system with weak attraction, revealing novel phase transitions and multicritical points due to the interplay of superfluidity and magnetic order.

Contribution

It introduces a combined equation of motion and mean-field approach to analyze superfluid and magnetic ordering, uncovering new phase transitions and multicritical phenomena.

Findings

Discovery of new chemical potential-driven phase transitions

Identification of exotic multicritical points with O(2,2) symmetry

Modified phase boundaries due to interplay of orders

Abstract

We investigate a three component fermion mixture in the presence of weak attractive interactions. We use a combination of the equation of motion and the Gaussian variational mean-field approaches, which both allow for simultaneous superfluid and magnetic ordering in an unbiased way, and capture the interplay between the two order parameters. This interplay significantly modifies the phase diagram, especially the superfluid-normal phase boundaries. In the close vicinity of the critical temperature and for small chemical potential imbalances, strong particle-hole symmetry breaking leads to a phase diagram similar to the one predicted by Cherng et al. [Phys. Rev. Lett. 99, 130406 (2007)], however, the overall phase diagram is markedly different: new chemical potential-driven first and second order transitions and triple points emerge as well as more exotic second order multicritical points, and bicritical lines with O(2,2) symmetry. We identify the terms which are necessary to capture this complex phase diagram in a Ginzburg-Landau approach, and determine the corresponding coefficients.