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arXiv · 0911.2103

Orbitally controlled Kondo effect of Co ad-atoms on graphene

T. O. Wehling·A. V. Balatsky·M. I. Katsnelson·A. I. Lichtenstein·A. Rosch
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Abstract

Based on ab-initio calculations we identify possible scenarios for the Kondo effect due to Co ad-atoms on graphene. General symmetry arguments show that for magnetic atoms in high-symmetry positions, the Kondo effect in graphene is controlled not only by the spin but also by the orbital degree of freedom. 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 $\sim 15$\,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 \sim 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.

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T. O. Wehling, A. V. Balatsky, M. I. Katsnelson, A. I. Lichtenstein, A. Rosch. 2010-03-19. Orbitally controlled Kondo effect of Co ad-atoms on graphene. https://doi.org/10.1103/physrevb.81.115427

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