摘要:
最近发现的插层三元铁硒超导体AyFexSe2（A=K,Rb,Cs和/或Tl）显示诸多新颖现象.为了澄清这些现象,作者分别计算了没有铁空位的基于完整四方FeSe层的AFe2Se2,含有四分之一铁空位的4×2或2×2超结构的AFe1.5Se2,以及含有五分之一铁空位的槡5×槡5超结构的A0.8Fe1.6Se2三种情况下的电子结构和相应的磁构型,发现AFe2Se2是双共线反铁磁的半金属,而AFe1.5Se2和A0.8Fe1.6Se2则是分别具有数十和数百毫电子伏特能隙的反铁磁半导体,并分别处于共线反铁磁长程序和区块化棋盘反铁磁长程序中.作者还分析和讨论了AyFexSe2的这些基本电子结构可能对超导性质的影响.
Abstract:
The newly discovered intercalated ternary iron-selenide superconductors AyFexSe2 （A=K, Rb, Cs, and/or Tl） show novel phenomena. To clarify these phenomena, we have carried out first-principles electronic structure calculations on AFe2Se2 with perfect tetragonal FeSe layers, AFe1.5Se2with one-quarter Fe vacancies ordered in the 4×2 or 2×2 superstructure, and A0.8Fe1.6Se2 with one-fifth Fe vacancies in the 5 × 5 superstructure. We find that the AFe2Se2 compounds are bi-collinear antiferromagnetic semimetals, while both AFe1.5Se2 and A0.8Fe1.6Se2 are antiferromagnetic semiconductors with band gaps of dozens and hundreds of meV, respectively; their ground states are in a collinear antiferromagnetic order and blocked checkerboard antiferromagnetic order, respectively. The underlying physics is discussed.
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