Electronic correlation and atom-atom interference effects in the interaction of atoms with graphene

M. A. ROMERO; A. IGLESIAS GARCÍA; E. C. GOLDBERG

Beijing, China

Congreso; 18 International Vacuum conference (IVC-18); 2010

A theoretical study of the problem of adsorbates on graphene is performed. The atom-surface system is described by considering the expansion of the graphene eigenstates in the C atomic orbitals within the Anderson model framework. In this way the whole features of the electronic band structure joined to the chemical properties of the interacting atoms determine the resonant charge exchange between adsorbate and graphene. Different situations related with the intra-atomic Coulomb repulsion term (U) are analyzed: zero, infinite and finite U values. Green function techniques and the equation of motion method are used to determine physical magnitudes of interest like the projected spectral density, the valence occupation, the level width of the resonance. The effect of the interferences between the C atoms which are able of interacting with the adsorbate is examined for several adsorbates (alkali and hydrogen atoms) and different adsorption geometries (on top, on bridge, on valley). The calculated single occupation probabilities at large distances allow for an explanation of the neutral fraction behavior obtained in the Li+ scattering by HOPG at low normal to the surface velocity values, only in the case we take into account the substrate atoms interferences, that is to consider the complete density matrix of the solid. In this case the C atoms which can be seen by the Li projectile are all on the surface plane, being in this sense the HOPG surface equivalent to graphene.