Racah materials: role of atomic multiplets in intermediate valence systems.
Racah materials: role of atomic multiplets in intermediate valence systems.
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DOI：
10.1038/srep15429
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发表时间：
2015-10-22
影响因子：
4.6
通讯作者：
Katsnelson MI
中科院分区：
文献类型：
--
作者：
Shick AB;Havela L;Lichtenstein AI;Katsnelson MI
我们解开了中间价化合物 SmB6 的非磁性绝缘态的长期谜团。在有效离散安德森杂质模型的局域密度近似（LDA）和精确对角化（ED）的组合中，发现SmB6中的Sm原子具有f壳占据<n4f> = 5.6的中间价基态。该基态是单重态，第一个激发三重态的能量高出~3 meV。 SmB6 是 LDA 中已有的窄带绝缘体，直接带隙约为 10 meV。电子相关性增加了带隙，现在带隙变得间接。因此，多体效应与间接带隙的形成有关，这对于 SmB6 中的“拓扑近藤绝缘体”的想法至关重要。此外，还考虑了锕系元素类似物 PuB6，并发现了 Pu 原子的中间价单线态基态。我们认为[Sm, Pu]B6属于一类新的具有多轨道“Kondo-like”单线基态的中间价材料。讨论了在此类 Racah 材料中与配体态不同杂化的复杂自旋轨道 f n–f n+1 多重态结构的关键作用。
We address the long-standing mystery of the nonmagnetic insulating state of the intermediate valence compound SmB6. Within a combination of the local density approximation (LDA) and an exact diagonalization (ED) of an effective discrete Anderson impurity model, the intermediate valence ground state with the f-shell occupation 〈n4f〉 = 5.6 is found for the Sm atom in SmB6. This ground state is a singlet, and the first excited triplet state ~3 meV higher in the energy. SmB6 is a narrow band insulator already in LDA, with the direct band gap of ~10 meV. The electron correlations increase the band gap which now becomes indirect. Thus, the many-body effects are relevant to form the indirect band gap, crucial for the idea of “topological Kondo insulator" in SmB6. Also, an actinide analog PuB6 is considered, and the intermediate valence singlet ground state is found for the Pu atom. We propose that [Sm, Pu]B6 belong to a new class of the intermediate valence materials with the multi-orbital “Kondo-like" singlet ground-state. Crucial role of complex spin-orbital f n–f n+1 multiplet structure differently hybridized with ligand states in such Racah materials is discussed.