Electrons scattering and conductivity in monolayer graphene

Resonance electronic states and scattering by point defects are studied for the monolayer graphene solving the 2+1-dimensional Dirac equation. Exact S- and T-matrices are calculated for the model potential. This effective potential takes into account possible band asymmetry of the point defect potential matrix elements. Regularization of the scattering problem for a singular potential has been carried out. Asymptotic analysis allowed us to obtain the conductivity dependence on the Fermi level position in the low-energy limit. Numerical calculations were carried out in the wide range of electronic energies. The transport relaxation time behaves as 1/E in the limit of E tending to zero and oscillates around a constant value due to the resonance scattering at higher energy magnitudes.