半导体KFe $_{0.8}$ Ag $_{1.2}$ Te $_2$中的互穿磁序和互穿磁序
Intertwined magnetic and nematic orders in semiconducting KFe$_{0.8}$Ag$_{1.2}$Te$_2$
摘要：
铁pnictides的超导电性出现从金属母体化合物表现出交织的条纹型磁秩序和磁秩序，与巡回电子建议是必不可少的。在这里，我们使用X射线和中子散射表明，一个类似的纠缠态实现在半导体KFe $_{0.8}$ Ag $_{1.2}$ Te $_2$（K $_5$ Fe $_4$ Ag $_6$ Te $_{10}$）没有巡回电子。我们发现在KFe $_{0.8}$ Ag $_{1.2}$ Te $_2$中Fe原子形成孤立的$2\times2$块，由Ag原子隔开。长程磁序集在低于$T_{\rm N}\approx35$ K，与磁矩内的$2\times2$铁块排序成条纹型配置。一个有序伴随着磁性转变，表现为结构扭曲，打破了晶格的四重旋转对称。KFe $_{0.8}$ Ag $_{1.2}$ Te $_2$和铁磷属元素化物母体化合物中的磁序在大小和它们与磁序的关系上是相似的，表明它们有共同的起源。由于KFe $_{0.8}$ Ag $_{1.2}$ Te $_2$是一种没有巡游电子的半导体，这表明局域磁矩磁相互作用是其磁序和磁序不可或缺的，这种相互作用可能在铁基超导性中起关键作用。
英文摘要：
Superconductivity in the iron pnictides emerges from metallic parent compounds exhibiting intertwined stripe-type magnetic order and nematic order, with itinerant electrons suggested to be essential for both. Here we use X-ray and neutron scattering to show that a similar intertwined state is realized in semiconducting KFe$_{0.8}$Ag$_{1.2}$Te$_2$ (K$_5$Fe$_4$Ag$_6$Te$_{10}$) without itinerant electrons. We find Fe atoms in KFe$_{0.8}$Ag$_{1.2}$Te$_2$ form isolated $2\times2$ blocks, separated by nonmagnetic Ag atoms. Long-range magnetic order sets in below $T_{\rm N}\approx35$ K, with magnetic moments within the $2\times2$ Fe blocks ordering into the stripe-type configuration. A nematic order accompanies the magnetic transition, manifest as a structural distortion that breaks the fourfold rotational symmetry of the lattice. The nematic orders in KFe$_{0.8}$Ag$_{1.2}$Te$_2$ and iron pnictide parent compounds are similar in magnitude and how they relate to the magnetic order, indicating a common origin. Since KFe$_{0.8}$Ag$_{1.2}$Te$_2$ is a semiconductor without itinerant electrons, this indicates that local-moment magnetic interactions are integral to its magnetic and nematic orders, and such interactions may play a key role in iron-based superconductivity.
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