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标题：High-temperature superconductivity from fine-tuning of Fermi-surface singularities in iron oxypnictides
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作者：A. Charnukha ; D. V. Evtushinsky ; C. E. Matt 等
期刊名称：Scientific Reports
电子版ISSN：2045-2322
出版年度：2015
卷号：5
期号：1
DOI：10.1038/srep18273
语种：English
出版社：Springer Nature
摘要：In the family of the iron-based superconductors, the RE FeAsO-type compounds (with RE being a rare-earth metal) exhibit the highest bulk superconducting transition temperatures ( T _c) up to 55 K and thus hold the key to the elusive pairing mechanism. Recently, it has been demonstrated that the intrinsic electronic structure of SmFe_0.92Co_0.08AsO ( T _c = 18 K) is highly nontrivial and consists of multiple band-edge singularities in close proximity to the Fermi level. However, it remains unclear whether these singularities are generic to the RE FeAsO-type materials and if so, whether their exact topology is responsible for the aforementioned record T _c. In this work, we use angle-resolved photoemission spectroscopy (ARPES) to investigate the inherent electronic structure of the NdFeAsO_0.6F_0.4 compound with a twice higher T _c = 38 K. We find a similarly singular Fermi surface and further demonstrate that the dramatic enhancement of superconductivity in this compound correlates closely with the fine-tuning of one of the band-edge singularities to within a fraction of the superconducting energy gap Δ below the Fermi level. Our results provide compelling evidence that the band-structure singularities near the Fermi level in the iron-based superconductors must be explicitly accounted for in any attempt to understand the mechanism of superconducting pairing in these materials.