Observation of photonic Fermi arcs in topological metamaterials

TL;DR

This paper reports the first direct experimental observation of photonic Fermi arcs in topological metamaterials, demonstrating topological surface states and backscattering immunity in a 3D classical system.

Contribution

It provides the first experimental evidence of photonic Fermi arcs in chiral hyperbolic metamaterials, advancing topological photonics in classical systems.

Findings

Observation of photonic Fermi arcs connecting topologically distinct states

Demonstration of backscattering-immune surface wave propagation

Verification of topological nature through bulk-surface correspondence

Abstract

The discovery of topological phases introduces new perspectives and platforms for various interesting physics originally investigated in quantum context and then, on an equal footing, in classic wave systems, such as photonics, acoustics and mechanics. As a characteristic feature, nontrivial Fermi arcs, connecting between topologically distinct Fermi surfaces, play vital roles in the clarification of Dirac and Weyl semimetals and have been observed in quantum materials very recently. However, in classical systems, no direct experimental observation of Fermi arcs in the momentum space has been reported so far. Here, using near-field scanning measurements, we show the observation of a photonic Fermi arcs connecting topologically distinct bulk states in chiral hyperbolic metamaterials. To verify the topological nature of this system, we further observe backscattering-immune propagation of nontrivial surface wave across a three-dimension physical step. Our results demonstrate metamaterial approach towards topological photonics and offer a deeper understanding of topological phases in three-dimension classical systems.