Department of Physics, National Sun Yat-Sen University , Kaohsiung 804, Taiwan.
Nano Lett. 2014 May 14;14(5):2505-8. doi: 10.1021/nl500206u. Epub 2014 Apr 18.
We use first-principles electronic structure calculations to predict a new class of two-dimensional (2D) topological insulators (TIs) in binary compositions of group III elements (B, Al, Ga, In, and Tl) and bismuth (Bi) in a buckled honeycomb structure. We identify band inversions in pristine GaBi, InBi, and TlBi bilayers, with gaps as large as 560 meV, making these materials suitable for room-temperature applications. Furthermore, we demonstrate the possibility of strain engineering in that the topological phase transition in BBi and AlBi could be driven at ∼6.6% strain. The buckled structure allows the formation of two different topological edge states in the zigzag and armchair edges. More importantly, isolated Dirac-cone edge states are predicted for armchair edges with the Dirac point lying in the middle of the 2D bulk gap. A room-temperature bulk band gap and an isolated Dirac cone allow these states to reach the long-sought topological spin-transport regime. Our findings suggest that the buckled honeycomb structure is a versatile platform for hosting nontrivial topological states and spin-polarized Dirac fermions with the flexibility of chemical and mechanical tunability.
我们使用第一性原理电子结构计算来预测一类新的二维（2D）拓扑绝缘体（TI），它们由 III 族元素（B、Al、Ga、In 和 Tl）和铋（Bi）的二元化合物在褶皱的蜂窝状结构中组成。我们在原始 GaBi、InBi 和 TlBi 双层中发现了带反转，带隙高达 560 meV，使这些材料适合于室温应用。此外，我们还展示了应变工程的可能性，即在 BBi 和 AlBi 中拓扑相变可以在约 6.6%的应变下驱动。褶皱结构允许在锯齿形和扶手椅边缘形成两种不同的拓扑边缘状态。更重要的是，对于扶手椅边缘，我们预测了孤立的狄拉克锥边缘状态，狄拉克点位于 2D 体带隙的中间。室温下的体带隙和孤立的狄拉克锥允许这些状态达到长期以来寻求的拓扑自旋输运状态。我们的研究结果表明，褶皱蜂窝状结构是一个多功能平台，可容纳具有化学和机械可调性的非平凡拓扑状态和自旋极化的狄拉克费米子。
