Direct observation of topological surface-state arcs in photonic metamaterials (article)

This is the final version of the article. Available from Springer Nature via the DOI in this record.The dataset associated with this article is in ORE at http://hdl.handle.net/10871/28162The discovery of topological phases has introduced new perspectives and platforms for various interesting physics originally investigated in quantum contexts and then, on an equal footing, in classic wave systems. As a characteristic feature, nontrivial Fermi arcs, connecting between topologically distinct Fermi surfaces, play vital roles in the classification 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 momentum space has been reported so far. Here, using near-field scanning measurements, we show the observation of photonic topological surface-state arcs connecting topologically distinct bulk states in a chiral hyperbolic metamaterial. To verify the topological nature of this system, we further observe backscattering-immune propagation of a nontrivial surface wave across a three-dimension physical step. Our results demonstrate a metamaterial approach towards topological photonics and offer a deeper understanding of topological phases in three-dimensional classical systems.This work was financially supported by ERC Consolidator Grant (Topological), the Royal Society and the Wolfson Foundation. B.Y. acknowledges China Scholarship Council (201306110041). S.Z. and B.B. acknowledge support from the Royal Society. Y.X. and D.F. acknowledge support from the National Natural Science Foundation of China (Grant Nos. 61490713 and 61505111). Q.G. acknowledges support from the National Natural Science Foundation of China (Grant No. 11604216). L.E.B., B.T. and A.P.H. acknowledge financial support from the Engineering and Physical Sciences Research Council (EPSRC) of the United Kingdom, via the EPSRC Centre for Doctoral Training in Metamaterials (Grant No. EP/L015331/1)