A Kene–Mele-type nearest-neighbor tight-binding model on a pyrochlore lattice is known to be a topological insulator in some parameter region. It is an important task to realize a topological insulator in a real compound, especially in an oxide that is stable in air. In this paper we systematically performed band structure calculations for six pyrochlore oxides A2B2O7 (A = Sn, Pb, Tl; B = Nb, Ta), which are properly described by this model, and found that heavily hole-doped Sn2Nb2O7 is a good candidate. Surprisingly, an effective spin–orbit coupling constant λ changes its sign depending on the composition of the material. Furthermore, we calculated the band structure of three virtual pyrochlore oxides, namely In2Nb2O7, In2Ta2O7 and Sn2Zr2O7. We found that Sn2Zr2O7 has a band gap at the k = 0 (Γ) point, similar to Sn2Nb2O7, though the band structure of Sn2Zr2O7 itself differs from the ideal nearest-neighbor tight-binding model. We propose that the co-doped system (In,Sn)2(Nb,Zr)2O7 may become a candidate of the three-dimensional strong topological insulator.

中文翻译：

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烧绿石氧化物中可能的三维拓扑绝缘体

已知烧绿石晶格上的 Kene-Mele 型最近邻紧束缚模型是某些参数区域中的拓扑绝缘体。在真实化合物中实现拓扑绝缘体是一项重要任务，尤其是在空气中稳定的氧化物中。在本文中，我们系统地对六种烧绿石氧化物 A2B2O7 (A = Sn, Pb, Tl; B = Nb, Ta) 进行了能带结构计算，该模型正确描述了这些，发现重空穴掺杂的 Sn2Nb2O7 是一个很好的候选者. 令人惊讶的是，有效的自旋轨道耦合常数 λ 会根据材料的成分改变其符号。此外，我们计算了三种虚拟烧绿石氧化物的能带结构，即 In2Nb2O7、In2Ta2O7 和 Sn2Zr2O7。我们发现 Sn2Zr2O7 在 k = 0 (Γ) 点有一个带隙，类似于 Sn2Nb2O7，尽管 Sn2Zr2O7 本身的能带结构与理想的最近邻紧束缚模型不同。我们提出共掺杂系统 (In,Sn)2​​(Nb,Zr)2O7 可能成为三维强拓扑绝缘体的候选者。