(a) The calculated slope κ^ee as a function of relative dielectric constant ɛ_r for gapless Dirac fermions. vħ is chosen to be 2.5 eV·Å, comparable with that in the experiment.^[66] (b) The slope κ of the conductivity–ln T curve as a function of magnetic field B for different antidot distance d. The measured κ (scatters) are fitted by the theory^[19] (solid curves). (c) The dielectric constant as a function of d, obtained by fitting the transport theory (ɛ_r) and calculated from the Bruggeman effective medium theory , respectively.^[67] The intrinsic dielectric constant ɛ_b = 22.0 of the no-antidot sample is extracted by fitting the transport theory. Adapted from Ref. [59].