Three-Dimensional Massive Dirac Fermions in the Topological Semimetal NbAs2

ORAL

Abstract

Topological nodal-line semimetals (NLSM) are newly discovered quantum materials where the Dirac conical structure extends over lines in the Brillouin zone. Compared to Dirac/Weyl semimetal, NLSMs are difficult to identify in part due to insufficient bulk sensitivity of available probes. Using magneto-optical spectroscopy, we have demonstrated the first example of electrodynamics associated with NLSM in NbAs2, where the spin-orbit interaction triggers energy gaps along the nodal lines. We find sharp steps in the interband optical conductivity, which also features the linear scaling σ1(ω)∼ω over an extended frequency range. Combined with the series of Landau-level transitions across the gap, we demonstrate the massive Dirac nature of the gap. Optical data offer a natural explanation for the giant magnetoresistance and negative longitudinal magnetoresistance in NbAs2. Intriguing weak in-gap states also appear in magneto-optical spectra and may be related to the theoretically predicted surface states. Our findings pave the way for future explorations of the gapped NLSM phase in NbAs2.

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Presenters

  • Yinming Shao

    Department of Physics, Columbia University

Authors

  • Yinming Shao

    Department of Physics, Columbia University

  • Ying Wang

    Department of Physics and Astronomy, Purdue University, National High Magnetic Field Laboratory

  • Zhiyuan Sun

    Physics, Univ of California - San Diego, Department of Physics, University of California San Diego, Univ of California - San Diego

  • Chenchao Xu

    Department of Physics, Zhejiang University

  • R. Sankar

    National Taiwan University, Center for Condensed Matter Sciences, National Taiwan University

  • Alexander Breindel

    Univ of California - San Diego, Department of Physics, University of California San Diego

  • M Brian Maple

    Department of Physics, University of California, San Diego, University of California, San Diego, Physics, University of California, San Diego, Univ of California - San Diego, Department of Physics and Center for Advanced Nanoscience, University of California, San Diego, Department of Physics, Center for Advanced Nanoscience,Materials Science and Engineering Program , Univ of California - San Diego, Department of Physics, University of California San Diego, Physics, Univ of California - San Diego, University of California-San Diego, UC San Diego, Physics, UC San Diego

  • Chao Cao

    Department of Physics, Hangzhou Normal University

  • Michael Fogler

    Physics, Univ of California - San Diego, Department of Physics, University of California San Diego, Univ of California - San Diego, UC San Diego, Physics, University of California, San Diego

  • Zhiqiang Li

    College of Physical Science and Technology, Sichuan University

  • Fangcheng Chou

    National Taiwan University, Center for Condensed Matter Sciences, National Taiwan University

  • Dimitri Basov

    Physics, Columbia University, Department of Physics, Columbia University, Columbia Univ, Columbia University