Tunable topological electronic structure of silicene on semiconducting Bi/Si(111)-root3xroot3 substrate: a first-principles
Chia-Hsiu Hsu1*, Zhi-Quan Huang1, Bo-Hung Chou1, Feng-Chuan Chuang1, Hsin Lin2, Arun Bansil3
1Department of Physics, National Sun Yat-Sen University, Kaohsiung, Taiwan
2Graphene Research Centre and Department of Physics, National University of Singapore, Singapore, Singapore
3Department of Physics, Northeastern University, Boston, Massachusetts, United States of America
* presenting author:Chia-Hsiu Hsu, email:shgosh2001@yahoo.com.tw
Using first-principles calculations to obtain the crystal and electronic structures, we show that the 1x1 phase of silicene is energetically more favorable than the root3xroot3 silicene superstructure on a semiconducting Bi/Si(111)-root3xroot3 substrate. The band gap of the system is found to be influenced strongly through the participation of Bi-orbitals, which possess a larger spin-orbit coupling strength compared to Si. In particular, the non-trivial (topological) band gap of a few meV in freestanding 1x1 silicene enlarges to 150 meV and becomes trivial in the presence of the substrate. We further show how an out-of-the-plane external electric field can be used to tune the band gap and restore the non-trivial topological phase

Keywords: first-principles calculations, silicene, Bi/Si(111), topological phase