Superconductivity in graphene on surfaces

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The repertoire of unique graphene properties is lacking superconductivity. Theoretical suggestions for achieving the superconducting state in graphene, e.g., alkali metal intercalation or injection of Cooper pairs by the proximity effect, have been published. Experimental evidence for the predicted scenarios, however, is scarce or even absent. The main target of the proposed research project is thus filling the gap of experimental verification. To this end simple model systems will be analyzed in a surface science approach. Superconductivity shall be induced in graphene on metal surfaces by two procedures. First, Li will be adsorbed on single-layer and bilayer graphene on Ir(111). Second, the proximity effect will be used to inject Cooper pairs from Nb(110) into a single adsorbed graphene sheet. The response of the superconducting state to the presence of nonmagnetic (Ag) and magnetic (Fe, Mn) impurities will be unravelled by the presence or absence of resonances inside the energy gap of superconducting graphene. Low-temperature scanning tunnelling microscopy and spectroscopy together with angle-resolved inelastic electron scattering will be used to obtain a comprehensive picture of graphene superconductivity.