The BCS-BEC crossover and the unitary fermi gas
The BCS-BEC crossover and the unitary fermi gas
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DOI：
10.1007/978-3-642-21978-8_1
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发表时间：
2012
影响因子：
15.1
通讯作者：
M. Randeria;W. Zwerger;M. Zwierlein
中科院分区：
文献类型：
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作者：
M. Randeria;W. Zwerger;M. Zwierlein
最近在超冷费米气体中Bardeen-Cooper-Schrieffer（BCS）到Bose Einstein凝聚（BEC）的实验和理论研究进展令人兴奋。在这些冷原子实验之前，超导体和超流体都是已知的，并且相当好地理解，它们都牢牢地处于两个极限之一。它们要么被著名的费米系统中的BCS配对理论很好地描述，要么可以用具有排斥相互作用的玻色子的BEC来理解。这是第一次，超冷费米气体表现出的行为，只要转动旋钮，就可以跨越从BCS到BEC的整个范围。虽然这种交叉在理论上已经被预测，但它在实验室中的实际实现是一个重大进步[1，2]，并导致了对位于交叉中间的非常强的相互作用的酉状态的性质的深入研究。我们现在知道，幺正费米气体具有显著的普适性质，这是由标度不变性引起的，它与核物理学和弦理论等各种领域都有联系。
There has been great excitement about the recent experimental and theoretical progress in elucidating the Bardeen-Cooper-Schrieffer (BCS) to Bose Einstein condensation (BEC) crossover in ultracold Fermi gases. Prior to these cold atom experiments, all known, and reasonably well understood, superconductors and superfluids were firmly in one of the two limits. Either they were well described by the celebrated BCS theory of pairing in Fermi systems, or they could be understood in terms of the BEC of bosons, with repulsive interactions. For the first time, the ultracold Fermi gases exhibited behavior that, with the turn of a knob, could be made to span the entire range from BCS to BEC. While such a crossover had been theoretically predicted, its actual realization in the laboratory was a major advance [1, 2], and led to intense investigation of the properties of the very strongly interacting, unitary regime that lies right in the middle of the crossover. We now understand that the unitary Fermi gas has remarkable universal properties, arising from scale invariance, and has connections with fields as diverse as nuclear physics and string theory.