Guo Xiaoqiu, Yu Ruixin, Jiang Jingwen, Ma Zhuang, Zhang Xiuwen
Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen, 518060, China.
Phys Chem Chem Phys. 2021 May 5;23(17):10545-10550. doi: 10.1039/d1cp00736j.
Topological insulation is widely predicted in two-dimensional (2D) materials realized by epitaxial growth or van der Waals (vdW) exfoliation. Such 2D topological insulators (TI's) host many interesting physical properties such as the quantum spin Hall effect and superconductivity. Here, we extend the search of 2D TI's into the exfoliatable non-vdW 2D crystals. We find that three-dimensional Dirac semimetals A3Bi (A = Na, K, Rb) (P3[combining macron]c1) can be exfoliated into 2D materials with exfoliation energies of 0.479-0.990 J m-2. Our careful examination of the topological invariants of exfoliated A3Bi monolayers/multilayers by using two well-established approaches reveals that bilayer and tetralayer Na3Bi are 2D TI's. It is found that the band gap of 2D TI's can be significantly increased by external strain. We further find that the predicted 2D TI's possess interesting hidden Rashba-like spin textures. Our results suggest a new arena to search for two-dimensional topological insulators and spintronic materials.
拓扑绝缘现象在通过外延生长或范德华（vdW）剥离实现的二维（2D）材料中被广泛预测。这类二维拓扑绝缘体（TI）具有许多有趣的物理特性，如量子自旋霍尔效应和超导性。在此，我们将二维TI的探索扩展到可剥离的非vdW二维晶体。我们发现三维狄拉克半金属A3Bi（A = Na、K、Rb）（P3[combining macron]c1）可以被剥离成二维材料，其剥离能为0.479 - 0.990 J m-2。我们通过两种成熟的方法仔细研究了剥离后的A3Bi单层/多层的拓扑不变量，结果表明双层和四层Na3Bi是二维TI。研究发现，二维TI的带隙可通过外部应变显著增加。我们进一步发现，预测的二维TI具有有趣的隐藏类Rashba自旋纹理。我们的结果为寻找二维拓扑绝缘体和自旋电子材料开辟了一个新领域。
