Single- or multi-flavor Kondo effect in graphene

Based on the tight-binding formalism, we investigate the Anderson and the Kondo model for an adatom magnetic impurity above graphene. Different impurity positions are analyzed. Employing a partial-wave representation we study the nature of the coupling between the impurity and the conducting electrons. The components from the two Dirac points are mixed while interacting with the impurity. Two configurations are considered explicitly: the adatom is above one atom (ADA), the other case is the adatom above the center the honeycomb (ADC). For ADA the impurity is coupled with one flavor for both A and B sublattice and both Dirac points. For ADC the impurity couples with multi-flavor states for a spinor state of the impurity. We show, explicitly for a 3d magnetic atom, d(z2), (d(xz), d(yz)), and (d(x2) (y2), d(xy)) couple respectively with the Gamma(1), Gamma(5)(E-1), and Gamma(6)(E-2) representations (reps) of C-6v group in ADC case. The bases for these reps of graphene are also derived explicitly. For ADA we calculate the Kondo temperature. Copyright (c) EPLA, 2010