有效离子价态与Kagome超导体中的局域磁矩
Effective Ionic Valence and Local Magnetic Moment in Kagome Superconductors
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中文总结 AI 辅助
通过电子结构计算与Sn掺杂实验，发现kagome超导体中V/Ti为2+价态并存在局域离子磁矩，提出从纯巡游载流子图像转向包含局域自旋强关联的新范式。
中文摘要 AI 辅助
为了理解kagome超导体家族AV$_3$Sb$_5$（A = K, Rb, Cs）和ATi$_3$Bi$_5$（A = Rb, Cs）中出乎意料的相似性及其关联行为，我们研究了这些体系的Hartree尺度局域电子结构。我们的结果表明，V和Ti离子均为2+价态，因此相应的巡游载流子密度相似，而电子数目的差异则反映在其量子涨落的离子磁矩上。然而，由于这些材料中受挫的晶格几何结构，这类局域磁矩难以通过标准探针在实验上直接观测。为进行验证，我们系统地引入非磁性Sn杂质以在局域上缓解几何阻挫，并通过磁化率以及μ子自旋旋转或弛豫（$\mu$SR）测量，在实验上证明了明确定义的局域磁矩的存在。所有实验均发现，随着非磁性杂质水平的增加，磁化率系统性增大。我们所发现的离子磁矩提示了一种范式转变，即从仅考虑巡游载流子的现有图像，转向纳入局域离子自旋强关联的图像。相关的原子间及局域-巡游关联为这类新型超导材料中观测到的丰富关联行为提供了坚实基础。
英文摘要
In order to understand the unexpected similarity and the correlated behavior in kagome superconductor families AV$_3$Sb$_5$ (A = K, Rb, Cs) and ATi$_3$Bi$_5$ (A = Rb, Cs), we investigate the Hartree-scale local electronic structure of these systems. Our result indicates that V and Ti ions are both of 2+ valence such that the corresponding itinerant carrier densities are similar, and the difference in electron count is instead reflected in their quantum fluctuating ionic magnetic moments. However, due to the frustrated lattice geometry of these materials, such local moments are difficult to experimentally observe via standard probes. For verification, we systematically introduce nonmagnetic Sn impurities to locally relieve the geometric frustration and experimentally demonstrate the existence of well-defined local magnetic moments via magnetic susceptibility and muon spin rotation or relaxation ($μ$SR) measurements. All experiments discover a systematic increase of magnetic susceptibility upon increasing nonmagnetic impurity level. Our discovered ionic moments suggest a paradigm shift from the existing itinerant carrier-only picture to one incorporating strong correlation from local ionic spins. The associated interatomic and local-itinerant correlations offer a solid ground for the emergence of the observed rich correlated behavior in this new family of superconducting materials.
发表机构
- Shanghai Jiao Tong University（上海交通大学）
- University of Cambridge（剑桥大学）
- University of California Santa Barbara（加州大学圣塔芭芭拉分校）
- Leibniz Institute for Solid State and Materials Research（莱布尼茨固体与材料研究所）
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