立方钙钛矿SrFeO$_3$中配体空穴态的实空间观测
Real-Space Observation of Ligand Hole State in Cubic Perovskite SrFeO$_3$
AI总结：
本研究针对过渡金属氧化物中配体空穴实空间分布未被观测的问题，通过高能X射线衍射与核差分傅里叶合成法，首次在立方钙钛矿SrFeO$_3$中观测到配体空穴的实空间分布，揭示了Fe异常价态的成因及与体系物性的关联。
摘要：
过渡金属氧化物化合物中有时会出现异常高价态。在这类体系中，空穴往往主要占据配体$p$轨道，从而产生有趣的物理性质，例如铜酸盐的超导性以及铁酸盐丰富的磁相。然而，此前从未有人在实空间中观测到配体空穴的分布。本文报道了通过高能X射线衍射实验以及采用核差分傅里叶合成法的精确电子密度分析，成功观测到立方钙钛矿SrFeO$_3$中价电子的空间分布。研究揭示了由Fe 3$d$与O 2$p$轨道杂化形成的配体空穴的实空间图像。Fe的异常价态归因于配体空穴的显著贡献，这与该体系的金属性以及不存在姜-泰勒（Jahn-Teller）畸变相关。
英文摘要：
An anomalously high valence state sometimes shows up in transition-metal oxide compounds. In such systems, holes tend to occupy mainly the ligand $p$ orbitals, giving rise to interesting physical properties such as superconductivity in cuprates and rich magnetic phases in ferrates. However, no one has ever observed the distribution of ligand holes in real space. Here, we report a successful observation of the spatial distribution of valence electrons in cubic perovskite SrFeO$_3$ by high-energy X-ray diffraction experiments and precise electron density analysis using a core differential Fourier synthesis method. A real-space picture of ligand holes formed by the orbital hybridization of Fe 3$d$ and O 2$p$ is revealed. The anomalous valence state in Fe is attributed to the considerable contribution of the ligand hole, which is related to the metallic nature and the absence of Jahn-Teller distortions in this system.
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