Figure 3: Experimental validation of subwavelength, topologically nontrivial phases.
From: Crystalline metamaterials for topological properties at subwavelength scales
We have fabricated by 3D printing followed by chemical metallization two subwavelength sized samples composed of conducting rods on a ground plane. (a) Picture of the topologically trivial sample made of shrunk hexagons. (b) Picture of the topologically nontrivial sample made of expanded hexagons. (c) Electric field amplitude spectrum in the bulk of the topologically trivial sample (spatially averaged). A complete band gap is observed (shaded frequency range). Outside of this gap, peaks correspond to efficient excitation of s, p, d and f type bulk Bloch modes, as confirmed by the electric field maps at these frequencies (e,f,g,h). (d) Same as (c) for the topologically nontrivial sample, demonstrating the topological band inversion phenomenon induced by subwavelength structural deformations, with the order of appearance of the p and d bands reversed with respect to the band gap. (i,j,k,l) Same as (e,f,g,h) for the topologically non-trivial sample.
