Evidence for superfluidity of ultracold fermions in an optical lattice
Evidence for superfluidity of ultracold fermions in an optical lattice
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DOI：
10.1038/nature05224
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发表时间：
2006-10-26
期刊：
影响因子：
64.8
通讯作者：
Ketterle, W.
中科院分区：
文献类型：
--
作者：
Chin, J. K.;Miller, D. E.;Ketterle, W.
周期势中超流费米子对的研究对于理解晶体材料中的超导电性具有重要的意义。通过使用冷原子气体，可以在高度可控的环境中研究各种凝聚态物质模型。光学晶格中的弱排斥费米子可以在低温下发生d波配对(1)，这可能是铜氧化物高温超导的一种机制(2)。晶格势还可以显著提高S波超流的临界温度。最近在大体积原子气体方面的实验进展包括观察到费米子对凝聚和高温超流(3-8)。在光学晶格中用费米子(9-11)和玻色子束缚对(12，13)进行的实验已经被报道，但还没有讨论超流行为。在这里，我们报道了当费米子原子对的凝聚体从光学晶格中释放时，观察到明显的干涉峰，这意味着长程有序(超流体的一种特性)。从概念上讲，这意味着现在已经在晶格势中建立了S波对和费米子对的相干性，在晶格势中，原子的输运是通过量子力学隧穿而不是简单的传播发生的。这些观测是针对费什巴赫共振两侧的相互作用而进行的。对于较大的晶格深度，相干以可逆的方式丢失，可能是由于从超流体到绝缘体的转变。光学晶格中这种强相互作用的费米子可以用来研究一类具有带间耦合和原子-分子耦合的新的哈密顿量(14)。
The study of superfluid fermion pairs in a periodic potential has important ramifications for understanding superconductivity in crystalline materials. By using cold atomic gases, various models of condensed matter can be studied in a highly controllable environment. Weakly repulsive fermions in an optical lattice could undergo d-wave pairing(1) at low temperatures, a possible mechanism for high temperature superconductivity in the copper oxides(2). The lattice potential could also strongly increase the critical temperature for s-wave superfluidity. Recent experimental advances in bulk atomic gases include the observation of fermion-pair condensates and high-temperature superfluidity(3-8). Experiments with fermions(9-11) and bosonic bound pairs(12,13) in optical lattices have been reported but have not yet addressed superfluid behaviour. Here we report the observation of distinct interference peaks when a condensate of fermionic atom pairs is released from an optical lattice, implying long-range order ( a property of a superfluid). Conceptually, this means that s-wave pairing and coherence of fermion pairs have now been established in a lattice potential, in which the transport of atoms occurs by quantum mechanical tunnelling and not by simple propagation. These observations were made for interactions on both sides of a Feshbach resonance. For larger lattice depths, the coherence was lost in a reversible manner, possibly as a result of a transition from superfluid to insulator. Such strongly interacting fermions in an optical lattice can be used to study a new class of hamiltonians with interband and atom - molecule couplings(14).