Experimental observation of Weyl points

The massless solutions to the Dirac equation are described by the so-called Weyl Hamiltonian. The Weyl equation requires a particle to have linear dispersion in all three dimensions while being doubly degenerate at a single momentum point. These Weyl points are topological monopoles of quantized Berry flux exhibiting numerous unusual properties. We performed angle-resolved microwave transmission measurements through a double-gyroid photonic crystal with inversion-breaking where Weyl points have been theoretically predicted to occur. The excited bulk states show two linear dispersion bands touching at four isolated points in the three-dimensional Brillouin zone, indicating the observation of Weyl points. This…

• NS
  National Science Foundation

  Awards: W911NF-13-D-0001, DMR-1419807, 1419807, W911NF-13
• UD
  U.S. Department of Energy
• MR
  Materials Research Science and Engineering Center, Harvard University

  Award: DMR-1419807
• SS
  Solid-State Solar Thermal Energy Conversion, Massachusetts Institute of Technology
• DO
  Division of Materials Research

  Awards: 1419807, DMR-1419807
• BE
  Basic Energy Sciences
• AR
  Army Research Office
• DO
  Division of Materials Sciences and Engineering