Electrical conductivity in graphene with point defects

The electrical conductivity of graphene containing point defects is studied within the binary alloy model in its dependence on the Fermi-level position at the zero temperature. It is found that the minimal conductivity value does not have a universal character and corresponds to the impurity resonance energy rather than to the Dirac point position in the spectrum. The substantial asymmetry of the resulting dependence of the conductivity on the gate-voltage magnitude is attributed as well to the very shift of the conductivity minimum to the resonance state energy.