Edge and interfacial states in a two-dimensional topological insulator: Bi(111) bilayer on Bi2Te2Se
Edge and interfacial states in a two-dimensional topological insulator: Bi(111) bilayer on Bi2Te2Se
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DOI：
10.1103/physrevb.89.155436
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发表时间：
2014-04-29
影响因子：
3.7
通讯作者：
Yeom, Han Woong
中科院分区：
文献类型：
--
作者：
Kim, Sung Hwan;Jin, Kyung-Hwan;Yeom, Han Woong
利用扫描隧道光谱（STS）和第一性原理计算研究了二维拓扑绝缘体Bi（111）双分子层及其边缘的电子态。在Bi2Te2Se晶体上外延生长出有序的双层薄膜和边缘呈锯齿状的岛屿。计算表明，由于Bi与Bi2Te2Se之间的强相互作用，Bi双分子层的带隙闭合，形成一个新的但较小的杂化隙。然而，双分子层的拓扑性质和拓扑边缘状态只有通过能量转移才能保持。利用STS对边缘增强的局部态密度进行了清晰的识别和可视化，与计算结果吻合较好。这是拓扑边缘态的明显标志，它对应于量子自旋霍尔态。Bi和Bi2Te2Se之间的界面态也在带隙区域内被识别。这种状态表现出微妙的边缘调制，这在以前被解释为拓扑边缘状态的证据。
The electronic states of a single Bi(111) bilayer and its edges, suggested as a two-dimensional topological insulator, are investigated by scanning tunneling spectroscopy (STS) and first-principles calculations. Well-ordered bilayer films and islands with zigzag edges are grown epitaxially on a cleaved Bi2Te2Se crystal. The calculation shows that the band gap of the Bi bilayer closes with a formation of a new but small hybridization gap due to the strong interaction between Bi and Bi2Te2Se. Nevertheless, the topological nature of the Bi bilayer and the topological edge state are preserved only with an energy shift. The edge-enhanced local density of states are identified and visualized unambiguously by STS in good agreement with the calculation. This is a clear sign of the topological edge state, which corresponds to the quantum spin Hall state. The interfacial state between Bi and Bi2Te2Se is also identified inside the band gap region. This state exhibits a subtle edge modulation, which was previously interpreted as the evidence of the topological edge state.