title: Pairing and phase separation in a polarized Fermi gas.
abstract: We report the observation of pairing in a gas of atomic fermions with unequal numbers of two components. Beyond a critical polarization, the gas separates into a phase that is consistent with a superfluid paired core surrounded by a shell of normal unpaired fermions. The critical polarization diminishes with decreasing attractive interaction. For near-zero polarization, we measured the parameter beta = -0.54 +/- 0.05, describing the universal energy of a strongly interacting paired Fermi gas, and found good agreement with recent theory. These results are relevant to predictions of exotic new phases of quark matter and of strongly magnetized superconductors.
authors.affiliation: Department of Physics and Astronomy and Rice Quantum Institute, Rice University, Houston, TX 77251, USA.
authors.forename: Guthrie B
authors.initials: GB
authors.lastname: Partridge
authors.forename: Wenhui
authors.initials: W
authors.lastname: Li
authors.forename: Ramsey I
authors.initials: RI
authors.lastname: Kamar
authors.forename: Yean-An
authors.initials: YA
authors.lastname: Liao
authors.forename: Randall G
authors.initials: RG
authors.lastname: Hulet