Fig. 4: Experimental observation of Berry curvatures.
From: Observation of Berry curvature in non-Hermitian system from far-field radiation
A The measured radiation Berry curvatures \({B}_{n;t}^{r}\) for the PhC sample with δr ≈ 0 (top panels) and the numerically calculated bulk Berry curvatures Bn with δr  =  2 nm (bottom panels) for a comparison. For a realistic sample with δr  =  0, the fabrication errors would slightly lift the DP at \({{{{\mathcal{K}}}}}_{1}\) point to create a small bandgap. We estimate that the bandgap is equivalent to the case of δr  = 2 nm. In this case, the Berry curvatures congregate around the \({{{{\mathcal{K}}}}}_{1}\) point since the bandgap is very small, showing opposite signs for TEA and TEB modes. B The measured radiation Berry curvatures \({B}_{B;t}^{r}\) (top panels) and the numerically calculated bulk Berry curvatures BB (bottom panels) for TEB mode when δr  = 4 nm (left), 7 nm (middle), and 10 nm (right). Along with the increasing δr, the bandgap gradually opens, and the Berry curvature gradually diffuses to a larger region in momentum space. Insets in top panels: SEM images of the unit cell of each PhC sample; insets in bottom panels: band structures of the two-level system accordingly.
