Collective oscillations of an imbalanced Fermi gas: axial compression modes and polaron effective mass.
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.
Nascimbène
S
S
Laboratoire Kastler Brossel, CNRS, UPMC, Ecole Normale Supérieure, 24 rue Lhomond, 75231 Paris, France.
Navon
N
N
Jiang
K J
KJ
Tarruell
L
L
Teichmann
M
M
McKeever
J
J
Chevy
F
F
Salomon
C
C