arXiv subjects

A. M. Fischer

Publications and source records attributed to A. M. Fischer.

3 recordsLinked to original sources

arXiv2011

Magnetoplasmons bound to short-range impurities in graphene: Symmetries and optics

We consider a graphene sheet in the presence of a strong perpendicular magnetic field with a single short-range delta-impurity situated at one of the carbon sites. We study the neutral inter-Landau level collective excitations, magnetoplasmons, which become localized on the impurity. Some of these excitations involve a pseudospin flip (intervalley transitions), since the impurity can scatter electrons between the two valleys. We propose a classification of states of the excitations in graphene and introduce the appropriate quantum numbers. The energies and optical strengths of collective excitations are calculated for a range of integer filling factors and impurity strengths. We establish a set of symmetries matching the energies and absorption strengths of collective excitations for different sublattice locations of the impurity, filling factors, circular light polarizations and signs of the impurity potential.

cond-mat.str-el↗

arXiv2009

Localised Magneto-Optical Collective Excitations of Impure Graphene

We study optically-induced collective excitations of graphene in the presence of a strong perpendicular magnetic field and a single impurity. We determine the energies and absorption strengths of these excitations, which become localised on the impurity. Two different types of impurity are considered i. the long-range Coulomb impurity, ii. a delta-function impurity located at either an A or B graphene sublattice site. Both impurity types result in some bound states appearing both above and below the magnetoplasmon continuum, although the effect of the short-range impurity is less pronounced. The dependence of the energies and oscillator strengths of the bound states on the filling factor is investigated.

cond-mat.mes-hall↗

arXiv2009

Localized Collective Excitations in Doped Graphene in Strong Magnetic Fields

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+ or acceptor A- 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 show that the single particle electron-hole symmetry of graphene leads to a duality between the spectra of collective modes for the D+ and A-. The duality shows up as a set of the D+ and A- magneto-absorption peaks having same energies, but active in different circular polarizations.

cond-mat.mes-hall↗