二维功能化MXene氮化物拓扑绝缘体的理论预测
Theoretical Prediction of Two-Dimensional Functionalized MXene Nitrides as Topological Insulators
摘要：
近年来，二维（2D）过渡金属碳化物和氮化物，即MXene，在电子和能量存储应用中引起了广泛的关注。由于大的自旋轨道耦合（SOC）和在费米能级处的类狄拉克带的存在，理论上已经提出一些MXene将是拓扑绝缘体（TI）。到目前为止，所有预测的TI MXene都属于过渡金属碳化物，其过渡金属原子为W，Mo或Cr。在这里，第一性原理和Z2指数计算的基础上，我们证明了一些MXene氮化物也可以是TI。我们发现，Ti3N2F2是一个二维TI，而Zr3N2F2是一个半金属与非平凡的带拓扑结构，可以变成一个二维TI时，晶格被拉伸。我们还发现，拉伸应变可以将Hf_3N_2F_2半导体转换为二维TI。由于Ti是合成MXene中最常用的过渡金属元素之一，我们期望我们的预测可以促进MXene作为TI器件的未来应用。
英文摘要：
Recently, two-dimensional (2D) transition metal carbides and nitrides, namely, MXenes have attracted lots of attention for electronic and energy storage applications. Due to a large spin-orbit coupling (SOC) and the existence of a Dirac-like band at the Fermi energy, it has been theoretically proposed that some of the MXenes will be topological insulators (TIs). Up to now, all of the predicted TI MXenes belong to transition metal carbides, whose transition metal atom is W, Mo or Cr. Here, on the basis of first-principles and Z2 index calculations, we demonstrate that some of the MXene nitrides can also be TIs. We find that Ti3N2F2 is a 2D TI, whereas Zr3N2F2 is a semimetal with nontrivial band topology and can be turned into a 2D TI when the lattice is stretched. We also find that the tensile strain can convert Hf3N2F2 semiconductor into a 2D TI. Since Ti is one of the mostly used transition metal element in the synthesized MXenes, we expect that our prediction can advance the future application of MXenes as TI devices.
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