Topologically Protected Photonic Edge States in the Visible in Plasmo‐Gyroelectric Metamaterials

Abstract Gyroelectric materials can be used to realize nontrivial photonic topological states. The usual strategy to maximize this effect is to increase the strength of the typically very small, off‐diagonal dielectric permittivity tensor components. This is a very difficult task, in particular at high frequencies. Here, an alternative method is proposed: reducing the strength of the diagonal permittivity tensor components. It is shown that this can be achieved by employing a layered plasmo‐gyroelectric metamaterial as the background medium of a 2D photonic crystal. It is demonstrated that by applying magnetic field, which breaks time reversal invariance, a topologically nontrivial photonic gap opens in the band structure of square and hexagonal photonic crystals. This is confirmed by detecting the presence of a topologically protected edge state at the boundary of this structure. This state is a photonic analog of the edge state in the conventional integer quantum Hall effect, also characterized by suppressed backscattering.