Coherent spectrum rearrangement in graphene: an additional nodal point   and an impurity band appearance
  It is demonstrated that a new nodal point is forming and a domain with anomalous dispersion is unfolding in the spectrum of charge carriers in graphene, when the concentration of weakly bound impurities exceeds a certain critical value. 
Yuriy V. Skrypnyk and Vadim M. Loktev
cond-mat.dis-nn cond-mat.mes-hall