Tuning impurity states in bilayer graphene

We study the impurity states in bilayer graphene in the unitary limit using Green's function method. Unlike in single layer graphene, the presence of impurities at two nonequivalent sites in bilayer graphene produces different impurity states, which is understood as the change in the band structure due to interlayer hopping of electrons. The impurity states can also be tuned by changing the band structure of bilayer grahene through external electric-field bias.