Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science (IBS), Pohang 37673, Republic of Korea.
Department of Physics, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea.
Sci Rep. 2016 Sep 14;6:33193. doi: 10.1038/srep33193.
While two-dimensional (2D) topological insulators (TI's) initiated the field of topological materials, only very few materials were discovered to date and the direct access to their quantum spin Hall edge states has been challenging due to material issues. Here, we introduce a new 2D TI material, Sb few layer films. Electronic structures of ultrathin Sb islands grown on Bi2Te2Se are investigated by scanning tunneling microscopy. The maps of local density of states clearly identify robust edge electronic states over the thickness of three bilayers in clear contrast to thinner islands. This indicates that topological edge states emerge through a 2D topological phase transition predicted between three and four bilayer films in recent theory. The non-trivial phase transition and edge states are confirmed for epitaxial films by extensive density-functional-theory calculations. This work provides an important material platform to exploit microscopic aspects of the quantum spin Hall phase and its quantum phase transition.
虽然二维（2D）拓扑绝缘体（TI）开创了拓扑材料领域，但迄今为止仅发现了极少数材料，并且由于材料问题，直接访问其量子自旋霍尔边缘态具有挑战性。在这里，我们引入了一种新的 2D TI 材料，即 Sb 少层膜。通过扫描隧道显微镜研究了生长在 Bi2Te2Se 上的超薄 Sb 岛的电子结构。局域态密度的图谱清楚地表明，在三个双层的厚度范围内存在稳健的边缘电子态，与较薄的岛形成鲜明对比。这表明拓扑边缘态是通过最近理论预测的在三个和四个双层膜之间的二维拓扑相变出现的。通过广泛的密度泛函理论计算，对外延膜的非平凡相变和边缘态进行了确认。这项工作为开发量子自旋霍尔相及其量子相变的微观方面提供了一个重要的材料平台。
