Berlin 2012 – scientific programme
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O: Fachverband Oberflächenphysik
O 53: Graphene IV
O 53.5: Talk
Wednesday, March 28, 2012, 17:45–18:00, MA 041
Graphene sublattice symmetry and isospin determined by ARPES using circularly polarized light — Isabella Gierz1, Matti Lindroos2, Hartmut Höchst3, •Christian R. Ast1, and Klaus Kern1 — 1MPI für Festkörperforschung, Stuttgart — 2Tampere University of Technology, Tampere, Finland — 3Synchrotron Radiation Center, Stoughton, WI, USA
The origin of the Dirac-like electronic structure of graphene can be traced back to the symmetry properties of the honeycomb lattice characterized by the equivalence of the two carbon atoms within the unit cell (the sublattice symmetry) as well as their relative phase (the isospin). We determine these parameters using angle-resolved photoemission spectroscopy (ARPES) in combination with circularly polarized synchrotron radiation. We developed a simple theoretical model which shows that the photocurrent can be written as the product of a well known sublattice interference term containing the relevant information about the initial state and a — previously neglected — matrix element accounting for the influence of the geometry of the experimental setup as well as final state effects. We will show that for a photon energy of hν=52 eV matrix element effects actually can be neglected which allows us to determine the sublattice symmetry parameter as well as the isospin with high accuracy.