Manipulating Topological Domain Boundaries in the Single-layer Quantum Spin Hall Insulator 1T'–WSe_2

Creators: Pedramrazi, Zahra; Herbig, Charlotte; Pulkin, Artem; Tang, Shujie; Phillips, Madeleine; Wong, Dillon; Ryu, Hyejin; Pizzochero, Michele; Chen, Yi; Wang, Feng; Mele, Eugene J.; Shen, Zhi-Xun; Mo, Sung-Kwan; Yazyev, Oleg V.; Crommie, Michael F.

Abstract

We report the creation and manipulation of structural phase boundaries in the single-layer quantum spin Hall insulator 1T′–WSe_2 by means of scanning tunneling microscope tip pulses. We observe the formation of one-dimensional interfaces between topologically nontrivial 1T′ domains having different rotational orientations, as well as induced interfaces between topologically nontrivial 1T′ and topologically trivial 1H phases. Scanning tunneling spectroscopy measurements show that 1T′/1T′ interface states are localized at domain boundaries, consistent with theoretically predicted unprotected interface modes that form dispersive bands in and around the energy gap of this quantum spin Hall insulator. We observe a qualitative difference in the experimental spectral line shape between topologically "unprotected" states at 1T′/1T′ domain boundaries and protected states at 1T′/1H and 1T′/vacuum boundaries in single-layer WSe_2.

Additional Information

© 2019 American Chemical Society. Received: May 27, 2019; Revised: July 6, 2019; Published: July 22, 2019. This research was supported as part of the Center for Novel Pathways to Quantum Coherence in Materials, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences (STM spectroscopy and dI/dV mapping). Support was also provided by the National Science Foundation under award EFMA-1542741 (surface preparation and topographic characterization). The work performed at the ALS (film characterization) was supported by the Office of Basic Energy Sciences, US DOE under Contract No. DE-AC02-05CH11231. C. H. acknowledges the support of Alexander von Humboldt Foundation for a Feodor Lynen research fellowship. The work performed at the Stanford Institute for Materials and Energy Sciences and Stanford University (MBE growth) was supported by the Division of Materials Science, Office of Basic Energy Sciences, US DOE under contract No. DE-AC02-76SF00515. Theoretical modeling of the two-channel conductance by M.P. and E.J.M. was supported by the DOE Office of Basic Energy Sciences under grant DE-FG02-ER45118. M.P. acknowledges support from an NRC Research Associateship award at the U.S. Naval Research Laboratory. S. T. acknowledges the support from the CPSF-CAS Joint Foundation for Excellent Postdoctoral Fellows. H. R. acknowledges fellowship support from NRF, Korea through Max Planck Korea/POSTECH Research Initiative No. 2016K1A4A4A01922028. A.P., M.P., and O.V.Y. acknowledge support by the ERC Starting grant "TopoMat" (Grant No. 306504) (ab initio theoretical formalism development), as well as Swiss National Science Foundation grants No. 162612 (2D bulk electronic structure) and No. 172543 (1D interface electronic structure). First-principles calculations were performed at the Swiss National Supercomputing Centre (CSCS) under project s832 and the facilities of Scientific IT and Application Support Center of EPFL. We thank Quansheng Wu for assistance with calculations, and we want to thank Canxun Zhang with helpful discussion. The authors declare no competing financial interest.

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