Topologically Protected Helical States in Minimally Twisted Bilayer Graphene

Shengqiang Huang, Kyounghwan Kim, Dmitry K. Efimkin, Timothy Lovorn, Takashi Taniguchi, Kenji Watanabe, Allan H. MacDonald, Emanuel Tutuc, and Brian J. LeRoy
Phys. Rev. Lett. 121, 037702 – Published 17 July 2018
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Abstract

In minimally twisted bilayer graphene, a moiré pattern consisting of AB and BA stacking regions separated by domain walls forms. These domain walls are predicted to support counterpropogating topologically protected helical (TPH) edge states when the AB and BA regions are gapped. We fabricate designer moiré crystals with wavelengths longer than 50 nm and demonstrate the emergence of TPH states on the domain wall network by scanning tunneling spectroscopy measurements. We observe a double-line profile of the TPH states on the domain walls, only occurring when the AB and BA regions are gapped. Our results demonstrate a practical and flexible method for TPH state network construction.

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  • Received 26 January 2018

DOI:https://doi.org/10.1103/PhysRevLett.121.037702

© 2018 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Shengqiang Huang1, Kyounghwan Kim2, Dmitry K. Efimkin3, Timothy Lovorn3, Takashi Taniguchi4, Kenji Watanabe4, Allan H. MacDonald3, Emanuel Tutuc2, and Brian J. LeRoy1,*

  • 1Physics Department, University of Arizona, Tucson, Arizona 85721, USA
  • 2Microelectronics Research Center, Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, Texas 78758, USA
  • 3Department of Physics, The University of Texas at Austin, Austin, Texas 78712, USA
  • 4National Institute for Materials Science, 1-1 Namiki Tsukuba Ibaraki 305-0044, Japan

  • *leroy@physics.arizona.edu

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Issue

Vol. 121, Iss. 3 — 20 July 2018

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