Review of photonics based on Weyl semimetals

Weyl semimetals are topological materials whose low-energy excitations obey the Weyl equation. In a Weyl semimetal, the conduction and valence bands touch at discrete points in momentum space called Weyl nodes. Weyl nodes are monopoles of the Berry curvature and are robust under generic perturbations. The quasiparticles near the Weyl nodes are analogous to Weyl fermions in high-energy physics; they exhibit linear dispersion and well-defined chirality.