Localized collective excitations in doped graphene in strong magnetic fields

Abstract

We consider collective excitations in graphene with filled Landau levels (LL's) in the presence of an external potential due to a single charged donor D{sup +} or acceptor A{sup -} impurity. We show that localized collective modes split off the magnetoplasmon continuum and, in addition, quasibound states are formed within the continuum. A study of the evolution of the strengths and energies of magneto-optical transitions is performed for integer filling factors {nu}=1,2,3,4 of the lowest LL. We predict impurity absorption peaks above as well as below the cyclotron resonance. We find that the single-particle electron-hole symmetry of graphene leads to a duality between the spectra of collective modes for the D{sup +} and A{sup -}. The duality shows up as a set of the D{sup +} and A{sup -} magnetoabsorption peaks having the same energies but active in different circular polarizations.