Observation of Coulomb gap in the quantum spin Hall candidate single-layer 1T'-WTe2

Ye-Heng Song, Zhen-Yu Jia, Dongqin Zhang, Xin-Yang Zhu, Zhi-Qiang Shi, Huaiqiang Wang, Li Zhu, Qian-Qian Yuan, Haijun Zhang, Ding-Yu Xing, Shao-Chun Li
2018 Nature Communications  
The two-dimensional topological insulators (2DTI) host a full gap in the bulk band, induced by spin-orbit coupling (SOC) effect, together with the topologically protected gapless edge states. However, the SOC-induced gap is usually small, and it is challenging to suppress the bulk conductance and thus to realize the quantum spin Hall (QSH) effect. In this study, we find a novel mechanism to effectively suppress the bulk conductance. By using the quasiparticle interference (QPI) technique with
more » ... I) technique with scanning tunneling spectroscopy (STS), we demonstrate that the QSH candidate single-layer 1T'-WTe$_2$ has a semi-metal bulk band structure with no full SOC-induced gap. Surprisingly, in this two-dimensional system, we find the electron interactions open a Coulomb gap which is always pinned at the Fermi energy (E$_F$). The opening of the Coulomb gap can efficiently diminish the bulk state at the E$_F$ and is in favor of the observation of the quantized conduction of topological edge states.
doi:10.1038/s41467-018-06635-x fatcat:2oumpba7znhy3a75dbemh2driy