Experimental verification of stable bismuthene on Si(111)-α-(√3×√3)-Au
BHEIM LLONA1*, Hsin-Lei Chou1, Shih-Yu Wu1, Liang-Wei Lan1, Chien-Cheng Kuo1
1Department of Physics, National Sun Yat-sen University, Kaohsiung, Taiwan
* Presenter:BHEIM LLONA, email:bheim.llona@gmail.com
Bismuthene, a bismuth honeycomb structure two-dimensional topological insulator (2D-TI), was predicted theoretically to grow on Si(111)-α-(√3x√3)-Au-substrate[1,2]. However, its existence still lacks direct experimental confirmation. Here, we realized experimentally, a stable bismuth honeycomb structure on a two-dimensional-electron gas Au/Si(111)-surface with direct access to its quantum-spin-Hall (QSH) edge states through electron beam evaporation epitaxial method[3]. The electronic properties of the interior and edge states of bismuthene islands were then probed concurrently via a scanning tunneling spectroscopy (STS) and a mapping of differential tunneling conductance (dI/dV). The results confirmed that the conducting edge states exist within the energy bandgap of the system. The STS spectra showed well-localized edge states with a metallic characteristic that appears at the boundary bridging the two different topological phases with an insulative interior universal bandgap of ~0.8 eV for the 2D-TI bismuthene. The topological edge states were observed with high tunneling conductance as indicated by its high dI/dV intensity compared to its weak interior states as reflected on the dI/dV mapping. Our experimental results demonstrated that the bismuthene in honeycomb geometry with an almost planar edge is a 2D-TI with accessible robust edge conductance.

[1] Chuang, F.-C., Yao, L.-Z., Huang, Z.-Q., Liu, Y.-T., Hsu, C.-H., Das, T., Lin, H., and Bansil, A., Nano Lett., (2014) 14, 2505−2508.
[2] Chuang, F.-C.Hsu, C.-H., Chou, H.-L., Crisostomo, C.-P., Huang, Z.-Q., Wu, S.-Y., Kuo, C.-C., Yeh, W.-C., Lin, H. and Bansil, A., Phys. Rev. B (2016) 93, 035429.
[3] Wu, S.-Y., Hsu, C.-H., Yeh, W.-C., Lin, H., Chuang, F.-C., Kuo, C.-C., Phys. Rev. B (2014) 90, 235407.

Keywords: Bismuthene, Scanning tunneling spectroscopy, Topological edge state, Two-dimensional topological insulator