Abstract

Rotational-symmetry-protected topological crystalline insulators (TCIs) are expected to host unique boundary modes, in that the surface normal to the rotational axis can feature surface states with ‘unpinned’ Dirac points, which are not constrained to lie on high symmetry points or lines, but can lie at any general k point in the Brillouin zone. Also, as a higher order bulk boundary correspondence is involved here, a three-dimensional (3D) TCI can support one-dimensional (1D) helical edge states. Using first-principles band structure calculations, we identify the van der Waals material -Bi4Br4 as a purely rotation symmetry protected TCI. We show that the surface of Bi4Br4 exhibits a pair of unpinned topological Dirac fermions which are related to the presence of a two-fold rotation axis. These unpinned Dirac fermions possess an exotic spin texture which will be highly favorable for spin transport, and a band structure that consists of van Hove singularities due to a Lifshitz transition. We also identify 1D topological hinge states along the edges of an -Bi4Br4 rod. We comment on how the predicted topological features in -Bi4Br4 could be accessed experimentally.

Highlights

  • 22 May 2019Chuang-Han Hsu1,2 , Xiaoting Zhou, Qiong Ma4, Nuh Gedik, Arun Bansil5,Vitor M Pereira, Hsin Lin , Liang Fu4, Su-Yang Xu4 and Tay-Rong Chang

  • Topological crystalline insulators (TCIs) are insulators in which the nontrivial band topology is protected by crystalline symmetries [1,2,3,4]

  • Such a 3D topological crystalline insulators (TCIs) can support 1D topological edge states due to the higher order bulk-boundary correspondence involved in this case [21,22,23,24,25,26,27].,in a rod with N-fold rotational symmetry that is finite sized along the two directions perpendicular to the rotational axis, the hinges of the rod host N helical 1D edge states

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Summary

22 May 2019

Chuang-Han Hsu1,2 , Xiaoting Zhou, Qiong Ma4, Nuh Gedik, Arun Bansil5,Vitor M Pereira, Hsin Lin , Liang Fu4, Su-Yang Xu4 and Tay-Rong Chang. Supplementary material for this article is available online title of the work, journal citation and DOI

Introduction
Method
Crystal structure and band topology
Surface states
Conclusion
Full Text
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