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New type of Weyl semimetal with quadratic double Weyl fermions

Author(s): Huang, Shin-Ming; Xu, Su-Yang; Belopolski, Ilya; Lee, Chi-Cheng; Chang, Guoqing; et al

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Abstract: 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 despite much 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 inversion-breaking, 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.
Publication Date: 2-Feb-2016
Electronic Publication Date: 19-Jan-2016
Citation: Huang, Shin-Ming, Xu, Su-Yang, Belopolski, Ilya, Lee, Chi-Cheng, Chang, Guoqing, Chang, Tay-Rong, Wang, BaoKai, Alidoust, Nasser, Bian, Guang, Neupane, Madhab, Sanchez, Daniel, Zheng, Hao, Jeng, Horng-Tay, Bansil, Arun, Neupert, Titus, Lin, Hsin, Hasan, M. Zahid. (2016). New type of Weyl semimetal with quadratic double Weyl fermions. Proceedings of the National Academy of Sciences, 113 (5), 1180 - 1185. doi:10.1073/pnas.1514581113
DOI: doi:10.1073/pnas.1514581113
ISSN: 0027-8424
EISSN: 1091-6490
Pages: 1180 - 1185
Type of Material: Journal Article
Journal/Proceeding Title: Proceedings of the National Academy of Sciences
Version: Author's manuscript

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