Figure 5. Electric tunability of the graphene meta-surface CPA: Spectra of the difference 
of the scattering coefficients (r and t) for the graphene meta-surface with Fermi energy EF ranging from 0.25 eV to 0.85 eV.
The solid line indicates quasi-CPA points where 
, while the spheres represent the extracted surface conductivities with values 
.