Université Grenoble Alpes, CEA, INAC-PHELIQS, F-38000 Grenoble, France.
Institute of Solid State Physics, Vienna University of Technology, Wiedner Hauptstrasse 8-10, Vienna 1040, Austria.
Nat Commun. 2017 Feb 23;8:14480. doi: 10.1038/ncomms14480.
Superconductivity is a unique manifestation of quantum mechanics on a macroscopic scale, and one of the rare examples of many-body phenomena that can be explained by predictive, quantitative theories. The superconducting ground state is described as a condensate of Cooper pairs, and a major challenge has been to understand which mechanisms could lead to a bound state between two electrons, despite the large Coulomb repulsion. An even bigger challenge is to identify experimentally this pairing mechanism, notably in unconventional superconductors dominated by strong electronic correlations, like in high-Tc cuprates, iron pnictides or heavy-fermion compounds. Here we show that in the ferromagnetic superconductor UCoGe, the field dependence of the pairing strength influences dramatically its macroscopic properties like the superconducting upper critical field, in a way that can be quantitatively understood. This provides a simple demonstration of the dominant role of ferromagnetic spin fluctuations in the pairing mechanism.
超导性是量子力学在宏观尺度上的独特表现，也是为数不多的可以用可预测、定量理论解释的多体现象之一。超导基态被描述为库珀对的凝聚态，主要的挑战是要理解哪些机制可以导致两个电子之间形成束缚态，尽管存在着巨大的库仑排斥力。更大的挑战是要在实验上识别出这种配对机制，特别是在强电子相关主导的非常规超导体中，如高温铜氧化物、铁磷化物或重费米子化合物。在这里，我们表明在铁磁超导体 UCoGe 中，配对强度的磁场依赖性极大地影响了其宏观性质，如超导上临界场，这种影响可以用定量的方式理解。这为铁磁自旋涨落在配对机制中起主导作用提供了一个简单的例证。
