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Type-II Symmetry-Protected Topological Dirac Semimetals

TitleType-II Symmetry-Protected Topological Dirac Semimetals
Publication TypeJournal Article
Year of Publication2017
AuthorsChang, Tay-Rong, Xu Su-Yang, Sanchez Daniel S., Tsai Wei-Feng, Huang Shin-Ming, Chang Guoqing, Hsu Chuang-Han, Bian Guang, Belopolski Ilya, Yu Zhi-Ming, Yang Shengyuan A., Neupert Titus, Jeng Horng-Tay, Lin Hsin, and Hasan Zahid M.
JournalPhys. Rev. Lett.
Date Published07/2017
Keywordsarcs, augmented-wave method, crystals, discovery, energy-bands, metal, signatures, state, wannier functions, weyl fermion semimetal

The recent proposal of the type-II Weyl semimetal state has attracted significant interest. In this Letter, we propose the concept of the three-dimensional type-II Dirac fermion and theoretically identify this new symmetry-protected topological state in the large family of transition-metal icosagenides, MA(3) (M = V, Nb, Ta; A = Al, Ga, In). We show that the VAl3 family features a pair of strongly Lorentz-violating type-II Dirac nodes and that each Dirac node can be split into four type-II Weyl nodes with chiral charge +/- 1 via symmetry breaking. Furthermore, we predict that the Landau level spectrum arising from the type-II Dirac fermions in VAl3 is distinct from that of known Dirac or Weyl semimetals. We also demonstrate a topological phase transition from a type-II Dirac semimetal to a quadratic Weyl semimetal or a topological crystalline insulator via crystalline distortions.


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