Extremely strong-coupling superconductivity in artificial two-dimensional Kondo lattices
Extremely strong-coupling superconductivity in artificial two-dimensional Kondo lattices
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DOI：
10.1038/nphys2112
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发表时间：
2011-11-01
期刊：
影响因子：
19.6
通讯作者：
Matsuda, Y.
中科院分区：
文献类型：
--
作者：
Mizukami, Y.;Shishido, H.;Matsuda, Y.
当相互作用的电子被限制在低维度时，电子-电子相关效应会显着增强，这通常会促使系统表现出在其他情况下极不可能的行为。具有最强电子相关性的超导性是在重费米子化合物中实现的，该化合物包含局域磁矩的致密晶格，与大量传导电子相互作用，形成三维近藤晶格(1)。超导性是否能持续有效地将这些材料的维数从三维降低到二维仍然是一个悬而未决的问题。在这里，我们报告了在这样一个最终强关联的重电子系统中对超导性的观察，该系统被限制在二维 Ce 原子方晶格（二维近藤晶格）内，这是通过制造由重费米子 CeCoIn5（参考文献 4）和传统金属 YbCoIn5 交替层构成的外延超晶格（2,3）来实现的。超晶格的场-温度相图表现出极不寻常的行为，包括上临界场相对于转变温度的显着增强。这意味着将超导电子对结合在一起的力由于二维化而呈现出极强的耦合性质。
When interacting electrons are confined to low dimensions, the electron-electron correlation effect is enhanced dramatically, which often drives the system into exhibiting behaviours that are otherwise highly improbable. Superconductivity with the strongest electron correlations is achieved in heavy-fermion compounds, which contain a dense lattice of localized magnetic moments interacting with a sea of conduction electrons to form a three-dimensional Kondo lattice(1). It had remained an unanswered question whether superconductivity would persist on effectively reducing the dimensionality of these materials from three to two. Here we report on the observation of superconductivity in such an ultimately strongly correlated system of heavy electrons confined within a two-dimensional square lattice of Ce atoms (two-dimensional Kondo lattice), which was realized by fabricating epitaxial superlattices(2,3) built of alternating layers of heavy-fermion CeCoIn5 (ref. 4) and conventional metal YbCoIn5. The field-temperature phase diagram of the superlattices exhibits highly unusual behaviours, including a striking enhancement of the upper critical field relative to the transition temperature. This implies that the force holding together the superconducting electron pairs takes on an extremely strong-coupled nature as a result of two-dimensionalization.