Fig. 3. CPGE spectrum.

CPGE amplitude βτ in units of $\frac{\mathrm{\pi }{e}^3}{3h^2}\times$ fs as a function of photon energy, showing abrupt quenching above 0.65 eV. The inset contains a schematic showing the surface 𝒮_ω in k-space defined by the available optical transitions at photon energy ℏω. For ℏω < E_C, 𝒮_ω encloses a single node and has integrated Berry flux C = ±4. Above E_C, it encloses two topological nodes of opposite chirality and C = 0. The blue shaded region in the main plot indicates the region where 𝒮_ω encloses only a single node.