“ Imaging Quantum Spin Hall Edges in Monolayer WTe2" By Yongtao Cui (University of California, Riverside)

Wednesday, October 24, 2018 - 4:00pm to 5:00pm
Condensed Matter Physics Seminar

Abstract: A two-dimensional topological insulator exhibits the quantum spin Hall (QSH) effect, in which topologically protected conducting channels exist at the sample edges. Experimental signatures of the QSH effect have recently been reported for the first time in an atomically thin material, monolayer WTe2. In this talk, I will present our recent experiment on direct imaging of the local conductivity of monolayer WTe2 devices with microwave impedance microscopy, a scanning probe technique that senses materials’ local electrical properties. Our results establish beyond doubt that conduction is indeed strongly localized to the physical edges at temperatures up to 77 K and above. Their electrical behaviors are consistent with expectations for topological edge states. Interestingly, we observe additional conducting features within most samples which can be explained by edge states following boundaries between topologically trivial and non-trivial regions. I will discuss the implications of these observations for interpreting and improving the properties of WTe2 devices. At the same time, they reveal the robustness of the QSH channels and the potential to engineer topological states in the monolayer material platform.

PAB 4-330