Greiner Markus, Regal Cindy A, Jin Deborah S
JILA, National Institute of Standards and Technology and Department of Physics, University of Colorado, USA.
Nature. 2003 Dec 4;426(6966):537-40. doi: 10.1038/nature02199. Epub 2003 Nov 26.
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 superconductors. In atomic Fermi gas experiments superfluidity has not yet been demonstrated; however, long-lived molecules consisting of locally paired fermions have been reversibly created. 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.
在费米子原子的稀薄气体中实现超流性，类似于金属中的超导性，是超冷气体研究的一个长期目标。在这样的费米子超流体中，应该可以调节相互作用强度，并在两个极限之间连续调节系统：巴丁-库珀-施里弗（BCS）型超流体（涉及动量空间中的相关原子对）和玻色-爱因斯坦凝聚体（BEC），其中空间上局部的原子对结合在一起。BCS型超流性和BEC极限之间的这种转变长期以来一直是理论研究的热点，部分原因是高温超导体的发现。在原子费米气体实验中，超流性尚未得到证实；然而，由局部配对的费米子组成的长寿命分子已被可逆地创造出来。在这里，我们报告了直接观察到仅通过调节超冷原子费米气体中的相互作用强度而产生的分子玻色-爱因斯坦凝聚体。这种物质状态代表了预测的BCS-BEC连续体的一个极端情况。
