Vacancy-induced splitting of the Dirac nodal point in graphene.

We investigate the vacancy effects on quasiparticle band structure of graphene near the Dirac point. It is found that each Dirac nodal point splits into two new nodal points due to the coherent multiple scattering among vacancies. The energy split between the two nodal points is proportional to the square root of vacancy concentration. In addition, an extra dispersionless band is developed at zero energy. Our theory offers an excellent explanation to the recent experiments. [ABSTRACT FROM AUTHOR]