报告题目：Growth and Characterization of single-layer 1T’-WTe2

报告人:  李绍春    南京大学

报告时间：12月11日 下午 15:00-16:00

报告地点：物理科技楼101

报告邀请人： 江华

报告摘要： The discovery of topological insulators (TIs) has drawn intense attention due to the intriguing properties of this new type of quantum matter. Single-layer 1T’-WTe2 has been recently predicted as the candidate of quantum spin Hall material. Even though experimental progress has been made, the band structure of 1T’-WTe₂ is still not well determined. In this presentation, we systematically discuss the growth and characterization of 1T’-WTe₂ film. By using the epitaxial graphene /SiC(0001) as the substrate, we found 1T’-WTe₂ initially prefers the single-layer growth mode, followed by the nucleation of the second layer on top of the first layer. Scanning tunneling microscopy was applied to investigate the electronic structure of single-layer 1T’-WTe₂ as well as its topological edge states. In contrast to the ARPES results, we find the 1T’-WTe₂ holds a semimetal-like band structure and the existence of Coulomb gap at the Fermi energy. The Coulomb gap efficiently suppresses the bulk state with the edge state unchanged, thus facilitating the observation of quantum spin Hall effect in this system.

Z. Jia, et al., “Direct visualization of a two-dimensional topological insulator in the single-layer 1T’-WTe₂” Phys. Rev. B96, 041108(R) (2017).

Y. Song et al., “Observation of Coulomb gap in the quantum spin Hall candidate single-layer 1T’-WTe2”Nature Commun9:4071(2018)

报告人简介：李绍春，南京大学物理系教授。1999年北京大学物理系获得学士学位，2004年中科院物理所获得博士学位。先后在美国宾州州立大学、德克萨斯大学奥斯汀分校、杜兰大学和哈佛大学做博士后和研究助理教授。2012年入职南京大学物理学院。主要利用扫描隧道显微镜（STM）和分子束外延（MBE）技术研究原子尺度下的表面物理和化学。近年来的研究兴趣主要是拓扑材料和低维材料，包括实验验证拓扑绝缘体以及对其性质的表征、调控，寻找基于拓扑绝缘体的异质结构中的奇异物理性质。

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