Description
Dirac points, arising from intrinsic space-group symmetry in hexagonal lattices, have been extensively explored in graphene and photonic crystals. However, their characteristic scales, confined either to atomic level (~Å) or limited by the operational wavelength (~λ), pose fundamental challenges for precisely engineering their topological properties and thus freely controlling the wave-transport behaviors in such systems. Here, beyond the conventional lattice-dependent paradigm, we demonstrate a type-I photonic Dirac point in the surface modes of an electromagnetic metasurface. This realization, governed by the intrinsic properties of constitutional units rather than the global crystalline symmetry, enables us to control Dirac physics in deep-subwavelength scales. Owing to the vanishing density of states at the type-I Dirac degeneracy, by strategically integrating inhomogeneous local symmetry-breaking as an artificial gauge field, we experimentally observe supersymmetric Landau levels and chiral zero modes with deep-subwavelength precisions in the microwave regime. Such a platform offers a branch-new approach to freely control surface waves through precisely engineering the spatial distribution of the gauge field imposed, with bending, focusing and spreading of surface waves experimentally demonstrated. By harnessing the mode-tuning flexibility of metasurfaces, our work establishes a versatile platform for topology-driven optical manipulation.
