Determination of the Superfluid Gap in Atomic Fermi Gases by   Quasiparticle Spectroscopy
  We present majority and minority radiofrequency (RF) spectra of strongly interacting imbalanced Fermi gases of Li-6. We observed a smooth evolution in the nature of pairing correlations from pairing in the superfluid region to polaron binding in the highly polarized normal region. The imbalance induces quasiparticles in the superfluid region even at very low temperature. This leads to a local bimodal spectral response, which allows us to determine the superfluid gap \Delta and the Hartree energy U. 
Andre Schirotzek, Yong-il Shin, Christian H. Schunck and Wolfgang   Ketterle