Symmetry Dictated Grain Boundary State in a Two-Dimensional Topological Insulator

Hyo Won Kim, Seoung Hun Kang, Hyun Jung Kim, Kisung Chae, Suyeon Cho, Wonhee Ko, Sangjun Jeon, Se Hwang Kang, Heejun Yang, Sung Wng Kim, Seongjun Park, Sungwoo Hwang, Young Kyun Kwon, Young Woo Son

Research output: Contribution to journalArticlepeer-review

14 Scopus citations


Grain boundaries (GBs) are ubiquitous in solids and have been of central importance in understanding the nature of polycrystals. In addition to their classical roles, topological insulators (TIs) offer a chance to realize GBs hosting distinct topological states that can be controlled by their crystal symmetries. However, such roles of crystalline symmetry in two-dimensional (2D) TIs have not been definitively measured yet. Here, we present the first direct evidence of a symmetry-enforced metallic state along a GB in 1T′-MoTe2, a prototypical 2D TI. Using scanning tunneling microscopy, we show a metallic state along a GB with nonsymmorphic lattice symmetry and its absence along another boundary with symmorphic symmetry. Our atomistic simulations demonstrate in-gap Weyl semimetallic states for the former, whereas they demonstrate gapped states for the latter, explaining our observation well. The observed metallic state, tightly linked to its crystal symmetry, can be used to create a stable conducting nanowire inside TIs.

Original languageEnglish
Pages (from-to)5837-5843
Number of pages7
JournalNano Letters
Issue number8
StatePublished - 12 Aug 2020

Bibliographical note

Publisher Copyright:
© 2020 American Chemical Society.


  • Grain boundary
  • Weyl semimetallic states
  • density functional theory calculations
  • nonsymmorphic symmetry
  • scanning tunneling microscopy
  • topological insulator


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