Polarized Fermi Condensates with Unequal Masses: Tuning the Tricritical Point

M. M. Parish, F. M. Marchetti, A. Lamacraft, and B. D. Simons 2007. Physical Review Letters

# 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 density of states and pair correlation functions depending on which side of the resonance it lies. Finally, we show that, when $$r\gtrsim 3.95$$, the finite-temperature phase diagram of trapped gases at unitarity becomes topologically distinct from the equal mass system.