Noguchi Ryo, Kobayashi Masaru, Kawaguchi Kaishu, Yamamori Wataru, Aido Kohei, Lin Chun, Tanaka Hiroaki, Kuroda Kenta, Harasawa Ayumi, Kandyba Viktor, Cattelan Mattia, Barinov Alexei, Hashimoto Makoto, Lu Donghui, Ochi Masayuki, Sasagawa Takao, Kondo Takeshi
Institute for Solid State Physics (ISSP), <a href="https://ror.org/057zh3y96">University of Tokyo</a>, Kashiwa, Chiba 277-8581, Japan.
Laboratory for Materials and Structures, <a href="https://ror.org/0112mx960">Tokyo Institute of Technology</a>, Yokohama, Kanagawa 226-8501, Japan.
Phys Rev Lett. 2024 Aug 23;133(8):086602. doi: 10.1103/PhysRevLett.133.086602.
We apply a topological material design concept for selecting a bulk topology of 3D crystals by different van der Waals stackings of 2D topological insulator layers, and find a bismuth halide Bi_{4}Br_{2}I_{2} to be an ideal weak topological insulator (WTI) with the largest band gap (∼300 meV) among all the WTI candidates, by means of angle-resolved photoemission spectroscopy (ARPES), density functional theory (DFT) calculations, and resistivity measurements. Furthermore, we reveal that the topological surface state of a WTI is not "weak" but rather robust against external perturbations against the initial theoretical prediction by performing potassium deposition experiments. Our results vastly expand future opportunities for fundamental research and device applications with a robust WTI.
我们应用一种拓扑材料设计概念，通过二维拓扑绝缘体层的不同范德华堆叠来选择三维晶体的体拓扑结构，并借助角分辨光电子能谱（ARPES）、密度泛函理论（DFT）计算和电阻率测量，发现卤化铋Bi₄Br₂I₂是所有弱拓扑绝缘体（WTI）候选材料中具有最大带隙（约300 meV）的理想弱拓扑绝缘体。此外，通过进行钾沉积实验，我们揭示出WTI的拓扑表面态并不“弱”，而是相对于最初的理论预测而言，对外部扰动具有很强的抗性。我们的结果极大地拓展了利用强抗性WTI进行基础研究和器件应用的未来机遇。
