Dresden 2011 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe
O: Fachverband Oberflächenphysik
O 51: Graphene III
O 51.6: Vortrag
Mittwoch, 16. März 2011, 16:15–16:30, WIL B321
Plasmon electron − hole resonance in epitaxial graphene — •Thomas Langer1,2, Jens Baringhaus1, Christoph Tegenkamp1, Herbert Pfnür1, and Hans Werner Schumacher2 — 1Institut für Festkörperphysik, Leibniz Universität Hannover, D-30167 Hannover — 2Physikalisch -Technische Bundesanstalt, D-38116 Braunschweig
The sheet plasmon in epitaxially grown graphene on SiC(0001) has been studied by means of angle resolved high resolution electron energy loss spectroscopy. Most interestingly, the dispersion reveals a dip, which can be assigned to quasiparticle dynamics. The effect is characteristic for pristine graphene and depends on the chemical potential but not on temperature and roughness. By assuming an resonant coupling between the 2d plasmon and an inter-band electron-hole pair excitation (so-called plexciton) the dip in the dispersion can be quantitatively explained using the Drude model of the dielectric function and the nearly free 2d electron gas model of Stern. The relation between this dip and the chemical potential becomes apparent by adsorption experiments performed with F4-TCNQ molecules, which reduces the carrier density and lowers the Fermi level. As expected the dip in the dispersion as well as the signature of the enhanced damping in the FWHM shifts to the lower kF-values. Remarkably, the average slope of the dispersion remains unchanged, although the electron density at EF is reduce. Obviously, the coupling of the plasmon mode with the loss channels leads to an effective integration over the electron density around EF with a width proportional to the measured FWHM of the plasmon mode.