具有拓扑非平凡能隙的高屈曲R3锡烯
High-buckled R3 stanene with topologically nontrivial energy gap
摘要：
锡烯被预测为二维拓扑绝缘体（2DTI）。它的低屈曲原子几何结构和增强的自旋轨道耦合有望引起显著的量子自旋霍尔（QSH）效应。然而，迄今为止，大多数实验生长的锡烯显示金属状态，没有真正的间隙，可能是由于与衬底的化学耦合和衬底施加的应力。在这里，我们展示了一个有效的方式调整的原子屈曲的锡烯打开一个拓扑非平凡的能隙。通过调节生长动力学，我们在Bi（111）衬底上不仅得到了低屈曲的1x1锡烯，而且得到了出乎意料的高屈曲的R3xR3锡烯。扫描隧道显微镜（STM）研究结合密度泛函理论（DFT）计算证实了R3xR3锡烯是一个畸变的1x1结构，在每三个1x1晶胞中有一个高屈曲的Sn。高屈曲的R3xR3锡烯有利于在Γ点处的大能带反转，并且自旋轨道耦合打开拓扑非平凡的能隙。在STM测量和DFT计算中验证的边缘态的存在进一步证实了R3xR3锡烯的拓扑结构。这项研究提供了一种替代的方式来调整单层2DTI材料的拓扑结构。
英文摘要：
Stanene has been predicted to be a two-dimensional topological insulator (2DTI). Its low-buckled atomic geometry and the enhanced spin-orbit coupling are expected to cause a prominent quantum spin hall (QSH) effect. However, most of the experimentally grown stanene to date displays a metallic state without a real gap, possibly due to the chemical coupling with the substrate and the stress applied by the substrate. Here,we demonstrate an efficient way of tuning the atomic buckling in stanene to open a topologically nontrivial energy gap. Via tuning the growth kinetics, we obtain not only the low-buckled 1x1 stanene but also an unexpected high-buckled R3xR3 stanene on the Bi(111) substrate. Scanning tunneling microscopy (STM) study combined with density functional theory (DFT) calculation confirms that the R3xR3 stanene is a distorted 1x1 structure with a high-buckled Sn in every three 1x1 unit cells. The high-buckled R3xR3 stanene favors a large band inversion at the Γ point, and the spin orbital coupling open a topologically nontrivial energy gap. The existence of edge states as verified in both STM measurement and DFT calculation further confirms the topology of the R3xR3 stanene. This study provides an alternate way to tune the topology of monolayer 2DTI materials.
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