Ideal Weyl points and helicoid surface states in artificial photonic crystal structures (article)

Abstract

Weyl points are the crossing points of linearly dispersing energy bands in the Brillouin zone of three-dimensional crystals. Weyl points provide the opportunity to explore a variety of intriguing phenomena such as topologically protected surface states and chiral anomalies. However the lack of an ideal Weyl system poses a serious limitation to the further development of Weyl physics and potential applications. Here, by experimentally characterizing a microwave photonic crystal comprised of a three dimensional array of saddle-shaped metallic coils, we observe ideal Weyl points which are related to each other through symmetry operations. Topological surface states exhibiting helicoidal structure in the energy-momentum space have also been demonstrated, which serve as a direct manifestation of the chiral nature of the Weyl points.