Figure 9: Measured surface transmissions when different kinds of defects are introduced near the surface.

(a,b) Photograph of the samples with defects. (c,d) Measured transmission spectra for two kinds of defects when the incident angle θ=35° (kz=0.2581π/d for 12.5 GHz). (e), (f) Results for θ=50° (kz=0.3447π/d for 12.5 GHz). Cyan boxes in c–f highlight the frequency region of kz-preserved one-way surface states where no obvious backscattering is introduced by the two kinds of defects. Note that the frequency region of robust transport for θ=50° is wider than that for θ=35°. This is consistent with the fact that the nontrivial band gap in the reduced 2D Brillouin zone is wider for a larger kz.