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Transition from collisionless to hydrodynamic behavior in an ultracold Fermi gas
1JILA, Quantum Physics Division, National Institute of Standards and Technology, University of Colorado, Boulder, Colorado 80309, USA.
Physical Review Letters
|November 3, 2001
Abstract:
Relative motion in a two-component, trapped atomic gas provides a sensitive probe of interactions. By studying the lowest frequency excitations of a two-spin-state gas confined in a magnetic trap, we have explored the transition from the collisionless to the hydrodynamic regime. As a function of collision rate, we observe frequency shifts as large as 6% as well as a dramatic, nonmonotonic dependence of the damping rate. The measurements agree qualitatively with expectations for behavior in the collisionless and hydrodynamic limits and are quantitatively compared to a classical kinetic model.