Prediction of two-dimensional topological insulator by forming surface alloy on Au/Si(111) substrate
Chia-Hsiu Hsu1*, Feng-Chuan Chuang1, Hsin-Lei Chou1, Christian P. Crisostomo1, Zhi-Quan Huang1, Shih-Yu Wu1, Chien-Cheng Kuo1, Wang-Chi V. Yeh2, Hsin Lin3,4, Arun Bansil5
1Department of Physics, National Sun Yat-Sen University, Kaohsiung, Taiwan
2Department of Physics, National Dong Hwa University, Hualien, Taiwan
3Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, Singapore, Singapore
4Department of Physics, National University of Singapore, Singapore, Singapore
5Department of Physics, Department of Physics, Boston, USA
* presenting author:Chia-Hsiu Hsu,
Two-dimensional (2D) topological insulators (TIs), which can be integrated into the modern silicon industry, are highly desirable for spintronics applications. Here, using fi rst-principles electronic structure calculations, we show that the Au/Si(111)-√3 substrate can provide a new platform for hosting 2D-TIs obtained through the formation of surface alloys with a honeycomb pattern of adsorbed atoms. We systematically examined elements from groups III to VI of the periodic table at 2/3 monolayer coverage on Au/Si(111)-√3, and found that In, Tl, Ge, and Sn adsorbates result in topologically nontrivial phases with band gaps varying from 0 to 72 meV. Our scanning tunneling microscopy and low-energy electron diff raction experiments con rm the presence of the honeycomb pattern when Bi atoms are deposited on Au/Si(111)-√3 in accord with our theoretical predictions. Our fi ndings pave the way for using surface alloys as a potential new route for obtaining viable 2D-TI platforms.

Keywords: topological insulators, first-principles calculation, surface alloy, Au/Si(111)