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Science 11 May 2007:
Vol. 316. no. 5826, pp. 867 - 870
DOI: 10.1126/science.1140749
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Reports

Pairing Without Superfluidity: The Ground State of an Imbalanced Fermi Mixture

C. H. Schunck,* Y. Shin, A. Schirotzek, M. W. Zwierlein,{dagger} W. Ketterle

We used radio-frequency spectroscopy to study pairing in the normal and superfluid phases of a strongly interacting Fermi gas with imbalanced spin populations. At high spin imbalances, the system does not become superfluid even at zero temperature. In this normal phase, full pairing of the minority atoms was observed. Hence, mismatched Fermi surfaces do not prevent pairing but can quench the superfluid state, thus realizing a system of fermion pairs that do not condense even at the lowest temperature.

Department of Physics, MIT-Harvard Center for Ultracold Atoms, and Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.

{dagger} Present address: Institut für Physik, AG Quantum, Staudinger Weg 7, 55128 Mainz, Germany.

* To whom correspondence should be addressed. E-mail: chs{at}mit.edu

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Science. ISSN 0036-8075 (print), 1095-9203 (online)