Hydrogenated ultra-thin tin films predicted as two-dimensional topological insulators
Zhi-Quan Huang1*, Bo-Hung Chou1, Chia-Hsiu Hsu1, Feng-Chuan Chuang1, Yu-Tzu Liu2, Hsin Lin2, Arun Bansil3
1Department of Physics, National Sun Yat-Sen University, Kaohsiung 804, Taiwan
2Graphene Research Centre and Department of Physics, Graphene Research Centre and Department of Physics, Singapore, Singapore
3Department of Physics, Northeastern University, Boston, Massachusetts 02115, United States of America
* presenting author:黃志權, email:d992030001@student.nsysu.edu.tw
Using thickness-dependent first-principles electronic structure calculations, we predict that hydrogenated ultra-thin films of tin harbor a new class of two-dimensional (2D) topological
insulators (TIs). A single bilayer (BL) tin film assumes a 2D-TI phase, but it transforms into a trivial insulator after hydrogenation. In contrast, tin films with 2 and 3 BLs are found to be trivial insulators, but hydrogenation of 2 to 4 BL films results in a non-trivial TI phase. For 1 to 3 BLs, H-passivation converts the films from being metallic to insulating. Moreover, we examined iodine-terminated tin films up to 3 BLs, and found these to be non-trivial, with the films becoming semi-metallic beyond 1 BL. In particular, the large band gap of 340 meV in an iodine-terminated tin bilayer is not sustained in the iodine-terminated 2BL and 3BL tin films.

Keywords: 2D topological insulators, topological phase transition, quantum spin Hall effect, tin thin films, first-principles calculations