Regensburg 2010 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 14: TR: Graphene 2
TT 14.10: Vortrag
Dienstag, 23. März 2010, 12:00–12:15, H21
The x-ray edge problem in graphene — Georg Röder1, Grigory Tkachov2, and •Martina Hentschel1 — 1MPI 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.