arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1111.1026cond-mat.supr-concond-mat.mtrl-sci
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超导体K0 1.6 + xSe2的局域结构:大结构无序的证据

Local Structure of the Superconductor K0.8Fe1.6+xSe2: Evidence of Large Structural Disorder

T. A. Tyson, T. Yu, S. J. Han, M. Croft, G. D. Gu, I. K. Dimitrov, Q. Li

摘要:

本文用X射线吸收谱研究了Tc = 32.6K的K0.8Fe_(1.6)+xSe_2超导单晶的局域结构。近边光谱表明Fe的平均价态为2+。通过铁、硒和钾的K边测量研究了铁、钾和硒位的室温结构。在最近邻的Fe-Se键中,Se和Fe位的结构表现出高度的有序性。另一方面,结合Se和K的局部结构测量揭示了K层中非常高水平的结构无序。在Fe位点的温度依赖性测量表明,Fe-Se原子相关性遵循超导体LaFeAsO0.89F0.11中的Fe-As相关性-具有相同的有效爱因斯坦温度(刚度)。在K0.8Fe1.6+ xSe 2中,最近邻Fe-Fe键具有比LaFeAsO0.89F0.11更低的爱因斯坦温度和更高的结构无序。中等Fe位和高K位结构无序与在这类材料中看到的高正常状态电阻率一致。对于更高的壳层,第二近邻铁-铁相互作用的增强被发现低于Tc,并表明Fe磁性离子对之间的相关性超出了第一邻居是重要的,在这些材料中的磁序和超导性的模型。

英文摘要:

The local structure of superconducting single crystals of K0.8Fe1.6+xSe2 with Tc = 32.6 K was studied by x-ray absorption spectroscopy. Near-edge spectra reveal that the average valence of Fe is 2+. The room temperature structure about the Fe, K and Se sites was examined by iron, selenium and potassium K-edge measurements. The structure about the Se and Fe sites shows a high degree of order in the nearest neighbor Fe-Se bonds. On the other hand, the combined Se and K local structure measurements reveal a very high level of structural disorder in the K layers. Temperature dependent measurements at the Fe sites show that the Fe-Se atomic correlation follows that of the Fe-As correlation in the superconductor LaFeAsO0.89F0.11 - having the same effective Einstein temperature (stiffness). In K0.8Fe1.6+xSe2, the nearest neighbor Fe-Fe bonds has a lower Einstein temperature and higher structural disorder than in LaFeAsO0.89F0.11. The moderate Fe site and high K site structural disorder is consistent with the high normal state resistivity seen in this class of materials. For higher shells, an enhancement of the second nearest neighbor Fe-Fe interaction is found just below Tc and suggests that correlations between Fe magnetic ion pairs beyond the first neighbor are important in models of magnetic order and superconductivity in these materials.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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