Type-II Symmetry-Protected Topological Dirac Semimetals

Tay Rong Chang, Su Yang Xu, Daniel S. Sanchez, Wei Feng Tsai, Shin Ming Huang, Guoqing Chang, Chuang Han Hsu, Guang Bian, Ilya Belopolski, Zhi Ming Yu, Shengyuan A. Yang, Titus Neupert, Horng Tay Jeng, Hsin Lin, M. Zahid Hasan

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144 Scopus citations


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, MA3 (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.

Original languageEnglish (US)
Article number026404
JournalPhysical review letters
Issue number2
StatePublished - Jul 14 2017

All Science Journal Classification (ASJC) codes

  • General Physics and Astronomy


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