New type of Weyl semimetal with quadratic double Weyl fermions

Shin Ming Huang, Su Yang Xuc, Ilya Belopolski, Chi Cheng Lee, Guoqing Chang, Tay Rong Chang, Bao Kai Wang, Nasser Alidoust, Guang Bian, Madhab Neupane, Daniel Sanchez, Hao Zheng, Horng Tay Jeng, Arun Bansil, Titus Neupert, Hsin Lin, M. Zahid Hasan

Research output: Contribution to journalArticlepeer-review

286 Scopus citations


Weyl semimetals have attracted worldwide attention due to their wide range of exotic properties predicted in theories. The experimental realization had remained elusive for a long time despitemuch effort. Very recently, the first Weyl semimetal has been discovered in an inversion-breaking, stoichiometric solid TaAs. So far, the TaAs class remains the only Weyl semimetal available in real materials. To facilitate the transition of Weyl semimetals from the realm of purely theoretical interest to the realm of experimental studies and device applications, it is of crucial importance to identify other robust candidates that are experimentally feasible to be realized. In this paper, we propose such a Weyl semimetal candidate in an inversionbreaking, stoichiometric compound strontium silicide, SrSi2, with many new and novel properties that are distinct from TaAs. We show that SrSi2 is a Weyl semimetal even without spin-orbit coupling and that, after the inclusion of spin-orbit coupling, two Weyl fermions stick together forming an exotic double Weyl fermion with quadratic dispersions and a higher chiral charge of ±2. Moreover, we find that the Weyl nodes with opposite charges are located at different energies due to the absence of mirror symmetry in SrSi2, paving the way for the realization of the chiral magnetic effect. Our systematic results not only identify a much-needed robust Weyl semimetal candidate but also open the door to new topological Weyl physics that is not possible in TaAs.

Original languageEnglish (US)
Pages (from-to)1180-1185
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number5
StatePublished - Feb 2 2016

All Science Journal Classification (ASJC) codes

  • General


  • Chiral magnetic effect
  • Fermi arc
  • Topological insulator
  • Weyl fermion


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