Observation of Phase Separation in a Strongly-Interacting Imbalanced Fermi Gas

TL;DR

This paper reports the direct observation of phase separation in a strongly interacting imbalanced Fermi gas, revealing a shell structure with a superfluid core surrounded by a normal phase, using advanced imaging techniques.

Contribution

First direct in situ imaging of phase separation in a strongly interacting imbalanced Fermi gas, demonstrating the spatial structure of superfluid and normal regions.

Findings

Identification of a shell structure with superfluid core and normal outer region

Observation of density profile changes during phase transition

Evidence of phase separation driven by spin imbalance

Abstract

We have observed phase separation between the superfluid and the normal component in a strongly interacting Fermi gas with imbalanced spin populations. The in situ distribution of the density difference between two trapped spin components is obtained using phase-contrast imaging and 3D image reconstruction. A shell structure is clearly identified where the superfluid region of equal densities is surrounded by a normal gas of unequal densities. The phase transition induces a dramatic change in the density profiles as excess fermions are expelled from the superfluid.