title: Collective oscillations of an imbalanced Fermi gas: axial compression modes and polaron effective mass.
abstract: We investigate the low-lying compression modes of a unitary Fermi gas with imbalanced spin populations. For low polarization, the strong coupling between the two spin components leads to a hydrodynamic behavior of the cloud. For large population imbalance we observe a decoupling of the oscillations of the two spin components, giving access to the effective mass of the Fermi polaron, a quasiparticle composed of an impurity dressed by particle-hole pair excitations in a surrounding Fermi sea. We find m*/m = 1.17(10), in agreement with the most recent theoretical predictions.
authors.affiliation: Laboratoire Kastler Brossel, CNRS, UPMC, Ecole Normale Supérieure, 24 rue Lhomond, 75231 Paris, France.
authors.forename: S
authors.initials: S
authors.lastname: Nascimbène
authors.forename: N
authors.initials: N
authors.lastname: Navon
authors.forename: K J
authors.initials: KJ
authors.lastname: Jiang
authors.forename: L
authors.initials: L
authors.lastname: Tarruell
authors.forename: M
authors.initials: M
authors.lastname: Teichmann
authors.forename: J
authors.initials: J
authors.lastname: McKeever
authors.forename: F
authors.initials: F
authors.lastname: Chevy
authors.forename: C
authors.initials: C
authors.lastname: Salomon