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Emergence of a molecular Bose–Einstein condensate from a Fermi gas

Nature volume 426, pages 537540 (04 December 2003) | Download Citation

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Abstract

The realization of superfluidity in a dilute gas of fermionic atoms, analogous to superconductivity in metals, represents a long-standing goal of ultracold gas research. In such a fermionic superfluid, it should be possible to adjust the interaction strength and tune the system continuously between two limits: a Bardeen–Cooper–Schrieffer (BCS)-type superfluid (involving correlated atom pairs in momentum space) and a Bose–Einstein condensate (BEC), in which spatially local pairs of atoms are bound together. This crossover between BCS-type superfluidity and the BEC limit has long been of theoretical interest, motivated in part by the discovery of high-temperature superconductors1,2,3,4,5,6,7,8,9,10. In atomic Fermi gas experiments superfluidity has not yet been demonstrated; however, long-lived molecules consisting of locally paired fermions have been reversibly created11,12,13,14,13. Here we report the direct observation of a molecular Bose–Einstein condensate created solely by adjusting the interaction strength in an ultracold Fermi gas of atoms. This state of matter represents one extreme of the predicted BCS–BEC continuum.

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Acknowledgements

We thank L. D. Carr, E. A. Cornell, C. E. Wieman, W. Zwerger and I. Bloch for discussions, and J. Smith for experimental assistance. This work was supported by NSF and NIST. C.A.R. acknowledges support from the Hertz Foundation.

Author information

Affiliations

  1. JILA, National Institute of Standards and Technology and Department of Physics, University of Colorado, USA

    • Markus Greiner
    •  & Cindy A. Regal
  2. Quantum Physics Division, National Institute of Standards and Technology, Boulder, Colorado 80309-0440, USA

    • Deborah S. Jin

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Competing interests

The authors declare that they have no competing financial interests.

Corresponding author

Correspondence to Markus Greiner.

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https://doi.org/10.1038/nature02199

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