Polarized Fermi condensates with unequal masses: Tuning the tricritical point

TL;DR

This paper investigates how unequal masses in a two-component Fermi gas affect the phase diagram, tricritical point, and stability of exotic pairing states, revealing new topological features at unitarity.

Contribution

It demonstrates the evolution of the tricritical point with mass ratio and analyzes the stability of various pairing states in mass-imbalanced Fermi gases.

Findings

Tricritical point shifts smoothly from BEC to BCS side with increasing mass ratio.

Interior gap state is unstable to phase separation.

Finite temperature phase diagram becomes topologically distinct for mass ratio r > 3.95.

Abstract

We consider a two-component atomic Fermi gas within a mean-field, single-channel model, where both the mass and population of each component are unequal. We show that the tricritical point at zero temperature evolves smoothly from the BEC- to BCS-side of the resonance as a function of mass ratio r. We find that the interior gap state proposed by Liu and Wilczek is always unstable to phase separation, while the breached pair state with one Fermi surface for the excess fermions exhibits differences in its DoSs and pair correlation functions depending on which side of the resonance it lies. Finally, we show that, when r > 3.95, the finite temperature phase diagram of trapped gases at unitarity becomes topologically distinct from the equal mass system.