Department of Physics, Yunnan University, Kunming 650091, China.
Phys Chem Chem Phys. 2019 Feb 6;21(6):2899-2909. doi: 10.1039/c8cp06391e.
Bismuth based (Bi-based) materials exhibit promising potential for the study of two-dimensional (2D) topological insulators or quantum spin Hall (QSH) insulators due to their intrinsic strong spin-orbit coupling (SOC). Herein, we theoretically propose a new inversion-asymmetry topological phase with tunable Rashba effect in a 2D bismuthene monolayer, which is driven by the sublattices half-oxidation (SHO). The nontrivial topology is identified by the SHO induced p-p band inversion at the Γ point, the Z2 topological number, and the metallic edge states. Interestingly, the SOC opens a band gap as large as 0.26 eV at Γ, which is twice as large as that of the freestanding bismuthene monolayer, revealing a predominant contribution of the orbital filtering effect. Inversion-symmetry breaking leads to a substantial Rashba constant of 11.5 eV Å near the valence band top, which is about twice as large as that of the freestanding bismuthene monolayer due to the SHO effect. In particular, the topological insulator-to-topological semimetal phase-transition and the tunable Rashba effect were achieved by exerting a moderate strain. We demonstrate that 3% stretching is the most desirable strain to obtain superior properties. Hexagonal boron nitrogen (h-BN) is proposed to serve as a suitable substrate for SHO-Bi in practical applications. Our findings not only provide a new route to engineering a 2D inversion-asymmetry topological insulator but also represent a significant advance in the exploration of 2D Bi-based topological materials.
铋基（Bi-based）材料由于其固有强自旋轨道耦合（SOC），在二维（2D）拓扑绝缘体或量子自旋霍尔（QSH）绝缘体的研究中显示出有前景的潜力。在此，我们理论上提出了一种新的具有可调拉什巴效应的二维二硒化铋单层的反演不对称拓扑相，该相由亚晶格半氧化（SHO）驱动。非平凡拓扑通过在 Γ 点处由 SHO 诱导的 p-p 带反转、Z2 拓扑数和金属边缘态来识别。有趣的是，SOC 在 Γ 处打开了高达 0.26 eV 的带隙，是自由二硒化铋单层的两倍，表明轨道滤波效应的主要贡献。反演对称性的破坏导致价带顶附近 Rashba 常数高达 11.5 eV Å，由于 SHO 效应，是自由二硒化铋单层的两倍。特别是，通过施加适度的应变可以实现拓扑绝缘体到拓扑半导体的相变和可调的 Rashba 效应。我们证明 3%的拉伸是获得优异性能的最理想应变。六方氮化硼（h-BN）被提议作为 SHO-Bi 在实际应用中的合适衬底。我们的发现不仅为工程 2D 反演不对称拓扑绝缘体提供了新途径，而且也代表了 2D Bi 基拓扑材料探索的重大进展。
