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 , in agreement with the most recent theoretical predictions.
- Received 15 July 2009
DOI:https://doi.org/10.1103/PhysRevLett.103.170402
©2009 American Physical Society