Surface electronic structure of Cr(001): Experiment and theory

Low-temperature scanning tunneling microscopy and spectroscopy investigations of the atomically clean Cr(001) surface together with density functional and many-body calculations have been used to study the surface electronic structure. The Friedel oscillations near impurity atoms have been observed and explained within the Fermi surface analysis. A very narrow resonance at 26 meV above the Fermi level has been observed and the orbital character of corresponding state has been visualized. The experimental data together with many-body calculations give further evidence that the observed resonance is an orbital Kondo resonance formed by two degenerated d(xz),d(yz) surface states. This gives evidence of strong correlation effects on transition metal surfaces.