Kondo effect of cobalt adatoms on nanostructured Cu-O surfaces: Scanning tunneling spectroscopy experiments and first-principles calculations

The Kondo response of single Co adatoms on a nanostructured Cu(110)-O stripe phase is studied using scanning tunneling spectroscopy (STS) and first-principles calculations. The nanostructured Cu-O substrate consists of a regular array of clean Cu(110) and oxygen-reconstructed Cu(110) 2 x 1-O stripes and allows us to measure STS of Co adatoms in different chemical environments under identical experimental conditions. The characteristic Kondo parameters are obtained from the Fano line-shape analysis of the STS data, finding a qualitatively different behavior on clean Cu(110) and Cu(110) 2 x 1-O adsorption sites, with a Fano-type peak around the Fermi energy in STS on Cu(110) and a Fano dip on Cu(2 x 1)-O, and mean Kondo temperatures of similar to 125 K and similar to 93 K, respectively. Density-functional calculations are performed to reveal the detailed geometry and the electronic structure of the Co adsorption complexes, and are used in conjunction with simple models of the Kondo effect to rationalize the present experimental observations and the trends with respect to literature data on other Cu surfaces.