Excitations at the crossover: the case of cubic KOsO3 with an incommensurate spin structure

We propose a RIXS experiment to identify the magnetic interaction and electronic structure in the perovskite KOsO3 synthesized recently. KOsO3 has a simple cubic perovskite structure and remains magnetic up to 800 K. The refinement of neutron diffraction gives an incommensurate spin structure below TN. KOsO3 remains a good conductor to the lowest temperature. The unusual spin structure suggests that KOsO3 may be at the crossover from localized to itinerant electronic behaviour. RIXS has been used to identify correlation fluctuations in the metallic phase above TN in the orthorhombic NaOsO3, which is a key factor to attribute the puzzling metal-insulator transition to the Mott transition in the perovskite. This proposal aims to construct a microscopic picture of the electronic state at the crossover by studying a variety of electron/orbital excitations with RIXS probe.

我们提出一项共振非弹性X射线散射（Resonant Inelastic X-ray Scattering, RIXS）实验，以鉴定近期合成的钙钛矿（perovskite）材料KOsO₃中的磁相互作用与电子结构。KOsO₃具有简单立方钙钛矿结构，且可保持磁性至800开尔文；中子衍射精修结果显示，其在奈耳温度（Neél temperature, T_N）以下存在非公度自旋结构。该材料在极低温度下仍为良导体，其反常的自旋结构暗示，KOsO₃可能处于局域电子行为向巡游电子行为转变的交叉区域。此前，RIXS已被用于鉴定斜方晶系的NaOsO₃中奈耳温度以上金属相的关联涨落，而这一关联涨落现象正是将该体系中令人费解的金属-绝缘体转变归因于钙钛矿莫特转变的关键因素。本实验方案旨在通过RIXS探针研究多种电子/轨道激发，构建该交叉区域内电子态的微观图像。