Measurement of positive and negative scattering lengths in a Fermi gas of atoms
Preprint
- 13 February 2003
Abstract
An exotic superfluid phase has been predicted for an ultracold gas of fermionic atoms. This phase requires strong attractive interactions in the gas, or correspondingly atoms with a large, negative s-wave scattering length. Here we report on progress toward realizing this predicted superfluid phase. We present measurements of both large positive and large negative scattering lengths in a quantum degenerate Fermi gas of atoms. Starting with a two-component gas that has been evaporatively cooled to quantum degeneracy, we create controllable, strong interactions between the atoms using a magnetic-field Feshbach resonance. We then employ a novel rf spectroscopy technique to directly measure the mean-field interaction energy, which is proportional to the s-wave scattering length. Near the peak of the resonance we observe a saturation of the interaction energy; it is in this strongly interacting regime that superfluidity is predicted to occur. We have also observed anisotropic expansion of the gas, which has recently been suggested as a signature of superfluidity. However, we find that this can be attributed to a purely collisional effect.Keywords
All Related Versions
- Version 1, 2003-02-13, ArXiv
- Published version: Physical Review Letters, 90 (23), 230404.
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