Observation of Phase Separation in a Strongly-Interacting Imbalanced   Fermi Gas
  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. 
Y. Shin, M. W. Zwierlein, C. H. Schunck, A. Schirotzek, W. Ketterle