Discovery of a Weyl fermion semimetal and topological Fermi arcs

A Weyl semimetal is a new state of matter that hosts Weyl fermions as emergent quasiparticles and admits a topological classification that protects Fermi arc surface states on the boundary of a bulk sample. This unusual electronic structure has deep analogies with particle physics and leads to unique topological properties. We report the experimental discovery of a Weyl semimetal, tantalum arsenide (TaAs). Using photoemission spectroscopy, we directly observe Fermi arcs on the surface, as well as the Weyl fermion cones and Weyl nodes in the bulk of TaAs single crystals. We find that Fermi arcs terminate on the Weyl fermion nodes, consistent with their topological character. Our work opens the field for the…

• UD
  U.S. Department of Energy

  Award: DE-FG-02-05ER46200
• NR
  Neurosciences Research Foundation

  Award: NRF-NRFF2013-03
• NR
  National Research Foundation
• NR
  National Research Foundation Singapore
• MO
  Ministry of Science and Technology, Taiwan

  Award: 102-2119-M-002-004
• NK
  National Key Research and Development Program of China

  Awards: 2014CB239302, 2013CB921901