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

• Published in: Nature communications Vol. 9; no. 1; pp. 1 - 6
• Main Authors: Song, Ye-Heng, Jia, Zhen-Yu, Zhang, Dongqin, Zhu, Xin-Yang, Shi, Zhi-Qiang, Wang, Huaiqiang, Zhu, Li, Yuan, Qian-Qian, Zhang, Haijun, Xing, Ding-Yu, Li, Shao-Chun
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 04.10.2018; Nature Publishing Group; Nature Portfolio
• Subjects: 147/138; 639/301/119/544; 639/766/119/2792/4128; 639/766/119/995; Conductance; Conduction; Energy; Humanities and Social Sciences; Molecular beam epitaxy; multidisciplinary; Resistance; Science; Science (multidisciplinary); Spectroscopy; Spectrum analysis; Spin-orbit interactions; Topography; Topological insulators
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-018-06635-x

The two-dimensional topological insulators host a full gap in the bulk band, induced by spin–orbit coupling (SOC) effect, together with the topologically protected gapless edge states. However, it is usually challenging to suppress the bulk conductance and thus to realize the quantum spin Hall (QSH) effect. In this study, we find a mechanism to effectively suppress the bulk conductance. By using the quasiparticle interference technique with scanning tunneling spectroscopy, we demonstrate that the QSH candidate single-layer 1 T ’-WTe 2 has a semimetal bulk band structure with no full SOC-induced gap. Surprisingly, in this two-dimensional system, we find the electron–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 supports the observation of the quantized conduction of topological edge states. The conductance from bulk bands in a topological insulator usually blurs effects arising from edge states. Here, Song et al. report a Coulomb gap opened by electron–electron interactions, which effectively suppress the bulk conductance and promote observation of topological edge states in the single-layer 1 T ’-WTe 2 .