Beijing Key Laboratory of Nanophotonics and Ultrafine Optoelectronic Systems, School of Physics, Beijing Institute of Technology, Beijing 100081, China.
Nanoscale. 2017 Jun 22;9(24):8207-8212. doi: 10.1039/c7nr01992k.
Two-dimensional (2D) large band-gap topological insulators (TIs) with highly stable structures are imperative for achieving dissipationless transport devices. However, to date, only very few materials have been experimentally observed to host the quantum spin Hall (QSH) effect at low temperature, thus obstructing their potential application in practice. Using first-principles calculations, herein, we predicted a new 2D TI in the porous allotrope of a bismuth monolayer, i.e. bismuthylene, its geometrical stability was confirmed via phonon spectrum and molecular dynamics simulations. Analysis of the electronic structures reveals that bismuthylene is a native QSH state with a band gap as large as 0.28 eV at the Γ point, which is smaller than that (0.50 eV) of the buckled Bi (111) and suitable for room temperature applications. Notably, it has a much lower energy than flattened Bi and a higher energy than buckled Bi (111)…” [corrected] and flattened Bi films; thus, bismuthylene is feasible for experimental realization. Interestingly, the topological properties can be retained under strains within the range of -6%-3% and electrical fields up to 0.8 eV Å. A heterostructure was constructed by sandwiching bismuthylene between BN sheets, and the non-trivial topology of bismuthylene was retained with a sizable band gap. These findings provide a platform to design a large-gap QSH insulator based on the 2D bismuthylene films, which show potential applications in spintronic devices.
二维（2D）大带隙拓扑绝缘体（TI）具有高度稳定的结构，对于实现无耗散输运器件至关重要。然而，迄今为止，只有极少数材料在低温下被实验观察到具有量子自旋霍尔（QSH）效应，从而阻碍了它们在实际中的潜在应用。本文通过第一性原理计算，预测了一种新的二维 TI，即在铋单层的多孔同素异形体中，即铋烯，其几何稳定性通过声子谱和分子动力学模拟得到了证实。电子结构分析表明，铋烯是一种本征的 QSH 态，在 Γ 点的带隙高达 0.28eV，小于（0.50eV）褶皱的 Bi（111）和适用于室温应用的带隙。值得注意的是，它的能量比平坦的 Bi 低，比褶皱的 Bi（111）和平坦的 Bi 薄膜高；因此，铋烯是可行的实验实现。有趣的是，拓扑性质可以在-6%-3%的应变范围内和高达 0.8eV Å的电场下保留。通过将铋烯夹在 BN 片之间构建了异质结构，保留了铋烯的非平凡拓扑结构和相当大的带隙。这些发现为设计基于二维铋烯薄膜的大带隙 QSH 绝缘体提供了一个平台，有望在自旋电子器件中得到应用。
