Separate tuning of nematicity and spin fluctuations to unravel the origin of superconductivity in FeSe
Separate tuning of nematicity and spin fluctuations to unravel the origin of superconductivity in FeSe
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DOI：
10.1038/s41535-020-0211-y
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发表时间：
2020-01
影响因子：
5.7
通讯作者：
S. Baek;J. Ok;J. S. Kim;S. Aswartham;I. Morozov;D. Chareev;T. Urata;K. Tanigaki;Y. Tanabe
中科院分区：
文献类型：
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作者：
S. Baek;J. Ok;J. S. Kim;S. Aswartham;I. Morozov;D. Chareev;T. Urata;K. Tanigaki;Y. Tanabe
轨道和自旋自由度的相互作用是许多凝聚态现象的基本特征，包括高温超导、量子自旋液体和拓扑半金属。在铁基超导体(FeSCs)中，这导致超导电性出现在另外两个不稳定点附近：向列相和磁性。揭示向列相有序、自旋涨落和超导电性之间的相互关系一直是FeSCs研究的主要挑战，但它仍然存在争议。本文通过对掺入钴和硫作为控制参数的FeSe单晶的~(77)Se核磁共振测量表明，超导转变温度Tc与自旋涨落的强度成正比，而与向列相转变温度Tnem无关。因此，我们的观察结果直接表明，FeSe的超导电性本质上是由中间耦合区域中的自旋涨落驱动的，而向列相涨落对NTC有轻微的影响。
The interplay of orbital and spin degrees of freedom is the fundamental characteristic in numerous condensed matter phenomena, including high-temperature superconductivity, quantum spin liquids, and topological semimetals. In iron-based superconductors (FeSCs), this causes superconductivity to emerge in the vicinity of two other instabilities: nematic and magnetic. Unveiling the mutual relationship among nematic order, spin fluctuations, and superconductivity has been a major challenge for research in FeSCs, but it is still controversial. Here, by carrying out77Se nuclear magnetic resonance (NMR) measurements on FeSe single crystals, doped by cobalt and sulfur that serve as control parameters, we demonstrate that the superconducting transition temperatureTcincreases in proportion to the strength of spin fluctuations, while it is independent of the nematic transition temperatureTnem. Our observation therefore directly implies that superconductivity in FeSe is essentially driven by spin fluctuations in the intermediate coupling regime, while nematic fluctuations have a marginal impact onTc.