Phase Separation in Mixtures of Repulsive Fermi Gases Driven by Mass Difference

TL;DR

This paper demonstrates that in mixtures of repulsive fermions, a sufficiently large mass difference induces phase separation, with the phenomenon's nature varying across dimensions, and links it to ferromagnetic transitions in related systems.

Contribution

It reveals the conditions for phase separation in mass-imbalanced fermion mixtures and connects this to ferromagnetic transitions via Bethe Ansatz analysis.

Findings

Phase separation occurs in fermion mixtures with large mass differences.

Density profiles differ significantly between 1D and 3D mixtures.

Ferromagnetic transition occurs at resonance when repulsive interactions become attractive.

Abstract

We show that phase separation must occur in a mixture of fermions with repulsive interaction if their mass difference is sufficiently large. This phenomenon is highly dimension-dependent. Consequently, the density profiles of phase separated 3d mixtures are very different from those in 1d. Noting that the ferromagnetic transition of a spin-1/2 repulsive Fermi gas is the equal mass limit of the phase separation in mixtures, we show from the Bethe Ansatz solution that a ferromagnetic transition will take place in the scattering states when the repulsive interaction passes through resonance and becomes attractive.