Superfluidity in Three-species Mixture of Fermi Gases across Feshbach Resonances

TL;DR

This paper extends the BEC-BCS crossover theory to a three-species Fermi gas mixture, revealing complex superfluid phases, phase transitions, and instabilities across Feshbach resonances with potential experimental signatures.

Contribution

It introduces a generalized multicomponent superfluid theory for three-species Fermi gases across Feshbach resonances, including phase transitions and instabilities.

Findings

Two-component Bose condensate at BEC side.

First-order quantum phase transition at BCS side.

Phase separation instability near critical regime.

Abstract

In this letter a generalization of the BEC-BCS crossover theory to a multicomponent superfluid is presented by studying a three-species mixture of Fermi gas across two Feshbach resonances. At the BEC side of resonances, two kinds of molecules are stable which gives rise to a two-component Bose condensate. This two-component superfluid state can be experimentally identified from the radio-frequency spectroscopy, density profile and short noise measurements. As approaching the BCS side of resonances, the superfluidity will break down at some point and yield a first-order quantum phase transition to normal state, due to the mismatch of three Fermi surfaces. Phase separation instability will occur around the critical regime.