Abstract
The 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.
Highlights
The discovery of topological phases has introduced new perspectives and platforms for various interesting physics originally investigated in quantum contexts and on an equal footing, in classic wave systems
The topological nature of the metamaterial can be described by a homogeneous effective model and its Weyl points arise from the degeneracies between intrinsic electromagnetic modes: the longitudinal plasmonic mode and the spin-polarized transverse mode[27, 28]
It is distinct from typical photonic realization of Weyl degeneracies in photonic crystals[22, 24, 26], where spatial degrees of freedom span the state sub-space
Summary
The discovery of topological phases has introduced new perspectives and platforms for various interesting physics originally investigated in quantum contexts and on an equal footing, in classic wave systems. On the interface of a bulk sample, gapless surface states exist, protected by chiral topological charges associated with the Weyl points.
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