Dresden 2011 – scientific programme
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O: Fachverband Oberflächenphysik
O 67: Graphene IV
O 67.4: Talk
Thursday, March 17, 2011, 12:00–12:15, WIL B321
Highly Anisotropic Dirac cones in epitaxial Graphene modulated by an island superlattice — •Markus Etzkorn1, Stefano Rusponi1, Marco Papagno2, Paolo Moras2, Sergio Vlaic1, Polina M. Sheverdyaeva2,3, Daniela Pacile4, Harald Brune1, and Carlo Carbone2 — 1Institute of Condensed Matter Physics, Ecole Polytechnique Fédérale de Lausanne, Switzerland — 2Istituto di Struttura della Materia-Consiglio Nazionale delle Ricerche, Trieste, Italy — 3Sinctrotrone Trieste, Trieste, Italy — 4Istitut. Naz. di Fisica Nucleare and Dip. di Fisica Universit‘a della Calabria, Cosenza, Italy
We present angle-resolved photoemission spectroscopy measurements of Graphene (G) on Ir(111) perturbed by self-assembled Ir clusters. While G/Ir(111) exhibits a sixfold symmetric band structure, the cluster superlattice induces a threefold symmetry with a strong renormalization of the electron group velocity close to the Dirac point giving rise to highly anisotropic Dirac cones. For the region up to 0.5 eV below EF a tight binding model of free standing G predicts an asymmetry of vΓ K− vpΓ K/vpΓ K = 5%. For G/Ir(111) we measure a value of vΓ K− vpΓ K/vpΓ K = 16 ± 2% indicating that the periodically modulated interaction between the G and the Ir-substrate already alters the band structure. This effect significantly increases for the case of the Ir superlattice on G/Ir(111) where we find vΓ K− vpΓ K/vpΓ K = 70 ± 5%. We further observe an influence of the cluster superlattice on the electronic gaps in the graphene band structure.