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Regensburg 2010 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 22: Graphene 2 (Joint Session with TT)

HL 22.10: Talk

Tuesday, March 23, 2010, 12:00–12:15, H21

The x-ray edge problem in grapheneGeorg Röder1, Grigory Tkachov2, and •Martina Hentschel11MPI für Physik komplexer Systeme, Dresden — 2Julius-Maximilians-Universität Würzburg

The excitation of a core electron to the conduction band by an x ray leads to the sudden creation of a localized, attractive potential and triggers the many-body responses that contribute to the x-ray edge problem, namely Anderson orthogonality catastrophe and Mahan's exciton (Mahan-Nozieres-DeDominicis response). We study them in mesoscopic systems, in particular for graphene, where the discrete level structure, boundary effects, and the filling-dependent variations in the density of states cause characteristic deviations from the well-understood bulk (metallic) behavior. The vanishing of the density of states at the Dirac points suppresses the orthogonality catastrophe. In the photoabsorption cross section, and for fillings smaller than half-filling, an additional Fermi-edge singularity develops at the Dirac point, similar to the behavior that, in metals, is known as the opening of a second band. We furthermore discuss the role of edge states that occur on zig-zag edges and their influence on the photoabsorption cross section.

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