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arXiv 0909.0480cond-mat.supr-con
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Fe-Se-Te超导体的局域原子结构

The local atomic structure of superconducting Fe-Se-Te

Martin C. Lehman, Despina Louca, Kazumasa Horigane, Anna Llobet, Ryotaro Arita, Sungdae Ji, Naoyuki Katayama, Shun Konbu, Kazuma Nakamura, Peng Tong, Tae-Yeong … 展开作者

Martin C. Lehman, Despina Louca, Kazumasa Horigane, Anna Llobet, Ryotaro Arita, Sungdae Ji, Naoyuki Katayama, Shun Konbu, Kazuma Nakamura, Peng Tong, Tae-Yeong Koo, Kazuyoshi Yamada

摘要:

我们报告的第一个本地原子结构的研究,通过对密度函数(PDF)分析的中子衍射数据,并显示直接相关的本地坐标TC在新发现的超导FeSe 1-xTex。Te对Se的等价取代例如在FeSe0.5Te0.5中使Tc与a-FeSe相比增加两倍而不改变载流子浓度,但平均而言降低硫属元素-Fe键角。然而,我们发现,局部对称性低于平均P4/nmm晶体对称性,因为Se和Te离子不共享相同的网站,导致两个不同的z坐标,表现出两种类型的键角与Fe。Fe和Se之间的夹角确实从FeSe中的~ 104.02 °增加到FeSe 0.5Te 0.5中的~ 105.20 °。同时,基于自旋密度泛函理论的从头计算得到了Se和Te具有不同z坐标的优化结构,与实验一致。Fe-Se键中的价电荷分布与Fe-Te键中的价电荷分布不同。因此,这种硫属化物的超导性与局部结构环境密切相关,直接影响到多带磁性,其中离子晶格的调制可以改变价电子的分布。

英文摘要:

We report on the first local atomic structure study via the pair density function (PDF) analysis of neutron diffraction data and show a direct correlation of local coordinates to TC in the newly discovered superconducting FeSe1-xTex. The isovalent substitution of Te for Se such as in FeSe0.5Te0.5 increases Tc by twofold in comparison to a-FeSe without changing the carrier concentration but, on average, decreases the chalcogen-Fe bond angle. However, we find that the local symmetry is lower than the average P4/nmm crystal symmetry, because the Se and Te ions do not share the same site, leading to two distinct z-coordinates that exhibit two types of bond angles with Fe. The angle indeed increases from ~ 104.02o in FeSe to ~105.20o in FeSe0.5Te0.5 between Fe and Se. Simultaneously, ab-initio calculations based on spin density function theory yielded an optimized structure with distinct z-coordinates for Se and Te, in agreement with the experiment. The valence charge distribution in the Fe-Se bonds was found to be different from that in the Fe-Te bonds. Thus, superconductivity in this chalcogenide is closely related to the local structural environment, with direct implications on the multiband magnetism where modulations of the ionic lattice can change the distribution of valence electrons.

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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