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HL: Fachverband Halbleiterphysik

HL 7: Graphene 1 (Joint Session with TT)

HL 7.1: Vortrag

Montag, 22. März 2010, 10:15–10:30, H18

Orbitally controlled Kondo effect of Co ad-atoms on graphene — •Tim Wehling¹, Alexander Balatsky², Mikhail Katsnelson³, Alexander Lichtenstein¹, and Achim Rosch⁴ — ¹I. Institut für Theoretische Physik, Universität Hamburg, Jungiusstrasse 9, 20355 Hamburg, Germany — ²Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA — ³Institute for Molecules and Materials, Radboud University of Nijmegen, Heijendaalseweg 135, 6525 AJ Nijmegen, The Netherlands — ⁴Institute for Theoretical Physics, University of Cologne, 50937 Cologne, Germany

Based on ab-initio calculations we identify possible scenarios for the Kondo effect due to Co ad-atoms on graphene. For a Co atom absorbed on top of a carbon atom, the Kondo effect is quenched by spin-orbit coupling below an energy scale of ∼ 15 K. For Co with spin S=1/2 located in the center of a hexagon, an SU(4) Kondo model describes the entanglement of orbital moment and spin at higher energies, while below ∼ 60 meV spin-orbit coupling leads to a more conventional SU(2) Kondo effect. The interplay of the orbital Co physics and the peculiar band-structure of graphene is directly accessible in Fourier transform tunneling spectroscopy or in the gate-voltage dependence of the Kondo temperature displaying a very strong, characteristic particle-hole asymmetry.