title: TOPOLOGICAL MATTER. Experimental observation of Weyl points.
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.
authors.affiliation: Department of Physics, Massachusetts Institute of Technology (MIT), Cambridge, MA 02139, USA. linglu@mit.edu.
authors.forename: Ling
authors.initials: L
authors.lastname: Lu
authors.affiliation: Laboratory of Applied Research on Electromagnetics (ARE), Zhejiang University, Hangzhou, Zhejiang 310027, China.
authors.forename: Zhiyu
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Laboratory of Applied Research on Electromagnetics (ARE), Zhejiang University, Hangzhou, Zhejiang 310027, China.
authors.forename: Dexin
authors.initials: D
authors.lastname: Ye
authors.affiliation: Laboratory of Applied Research on Electromagnetics (ARE), Zhejiang University, Hangzhou, Zhejiang 310027, China.
authors.forename: Lixin
authors.initials: L
authors.lastname: Ran
authors.affiliation: Department of Physics, Massachusetts Institute of Technology (MIT), Cambridge, MA 02139, USA.
authors.forename: Liang
authors.initials: L
authors.lastname: Fu
authors.affiliation: Department of Physics, Massachusetts Institute of Technology (MIT), Cambridge, MA 02139, USA.
authors.forename: John D
authors.initials: JD
authors.lastname: Joannopoulos
authors.affiliation: Department of Physics, Massachusetts Institute of Technology (MIT), Cambridge, MA 02139, USA.
authors.forename: Marin
authors.initials: M
authors.lastname: Soljačić