Discovery of ideal Weyl points with helicoid surface states

TL;DR

This paper reports the experimental realization of an ideal Weyl system in a photonic metamaterial, where Weyl points are perfectly aligned in energy, enabling detailed study of associated helicoid surface states and advancing topological photonics.

Contribution

The authors construct and experimentally demonstrate an ideal Weyl photonic metamaterial with symmetrically pinned Weyl points, providing a platform for exploring Weyl physics and topological devices.

Findings

Observation of an ideal Weyl system with energy-pinned Weyl points

Mapping of complete helicoid surface state evolution

Potential for advanced topological photonic applications

Abstract

Weyl points, serving as monopoles in the momentum space and laying the foundation of topological gapless phases, have recently been experimentally demonstrated in various physical systems. However, none of the observed Weyl degeneracies are ideal: they either offset in energy or coexist with trivial dispersions at other momenta. The lack of an ideal Weyl system sets a serious limit to the further development of Weyl physics and potential applications. Here, by constructing a photonic metamaterial, we experimentally observe an ideal Weyl system, whose nodal frequencies are pinned by symmetries to exactly the same value. Benefitting from the ideal Weyl nodes, we are able to map out the complete evolution of the helicoid surface states spinning around the projections of each Weyl nodes. Our discovery provides an ideal photonic platform for Weyl systems and novel topological devices.