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Imaging 2D topological systems with microwave impedance microscopy
Add to Calendar 2020-11-02T20:30:00 2020-11-02T21:30:00 UTC Imaging 2D topological systems with microwave impedance microscopy Zoom link:
Start DateMon, Nov 02, 2020
3:30 PM
End DateMon, Nov 02, 2020
4:30 PM
Presented By
Yongtao Cui, UC Riverside
Event Series: CAMP Seminar

Two-dimensional topological systems exhibit non-trivial topological characters in their electronic band structures. When the Fermi level is tuned into the topological gap, conductive edge states appear at the boundaries, leading to a series of signature transport phenomena, including the quantum Hall, quantum spin Hall, and quantum anomalous Hall effects. Recently, several atomic layered materials emerge as promising platforms to study topological physics in 2D. In our study, we employ scanning microwave impedance microscopy to image local conductivity at both edges and bulk states of the 2D topological materials. In monolayer WTe2, a quantum spin Hall insulator, we directly resolve the edge conduction at temperatures of 77 K and above. In addition, we observe conducting features in the interior of the sample which can be explained by edge states following boundaries between topologically trivial and nontrivial regions. In thin flakes of MnBi2Te4, a 2D Chern insulator which exhibits field-driven quantum anomalous Hall effect, we image the formation of the Chern insulator gap and the chiral edge states as the sample is driven from an antiferromagnetic to ferromagnetic phase by a magnetic field. In particular, a band crossing feature is resolved to correlate with the magnetic state, indicating the role of the magnetic order in the formation of the topological gap. Results from local imaging experiments offer new insights into the topological properties in these novel 2D material systems.