Resonance of the Fermi velocity in weakly doped graphene

It has been revealed that the dependence of the Fermi velocity on the number of charge carriers in doped graphene contains a sharp peak at which the Fermi velocity can increase by a factor of more than 1.5. It has been shown that this peak, which appears when the Fermi energy coincides with the energy of single-impurity resonance, exists when the concentration of impurities is lower than the corresponding critical concentration at which the spectrum of the system is rearranged.