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Science. 2015 Aug 7;349(6248):622-4. doi: 10.1126/science.aaa9273. Epub 2015 Jul 16.

TOPOLOGICAL MATTER. Experimental observation of Weyl points.

Author information

1
Department of Physics, Massachusetts Institute of Technology (MIT), Cambridge, MA 02139, USA. linglu@mit.edu.
2
Laboratory of Applied Research on Electromagnetics (ARE), Zhejiang University, Hangzhou, Zhejiang 310027, China.
3
Department of Physics, Massachusetts Institute of Technology (MIT), Cambridge, MA 02139, USA.

Abstract

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 work paves the way to a variety of photonic topological phenomena in three dimensions.

PMID:
26184914
DOI:
10.1126/science.aaa9273
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