Evidence of Bose-Einstein Condensation in an Atomic Gas with Attractive Interactions
- 28 August 1995
- journal article
- research article
- Published by American Physical Society (APS) in Physical Review Letters
- Vol. 75 (9), 1687-1690
- https://doi.org/10.1103/physrevlett.75.1687
Abstract
Evidence for Bose-Einstein condensation of a gas of spin-polarized Li atoms is reported. Atoms confined to a permanent-magnet trap are laser cooled to 200 μK and are then evaporatively cooled to lower temperatures. Phase-space densities consistent with quantum degeneracy are measured for temperatures in the range of 100 to 400 nK. At these high phase-space densities, diffraction of a probe laser beam is observed. Modeling shows that this diffraction is a sensitive indicator of the presence of a spatially localized condensate. Although measurements of the number of condensate atoms have not been performed, the measured phase-space densities are consistent with a majority of the atoms being in the condensate, for total trap numbers as high as atoms. For Li, the spin-triplet -wave scattering length is known to be negative, corresponding to an attractive interatomic interaction. Previously, Bose-Einstein condensation was predicted not to occur in such a system.
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