Theory of the Fano resonance in the STM tunneling density of states due toa single Kondo impurity

The conduction electron density of states nearby single magnetic impurities , as measured recently by scanning tunneling microscopy (STM), is calculate d, taking into account tunneling into conduction electron states only. The Kondo effect induces a narrow Fano resonance in the conduction electron den sity of states. The line shape varies with the distance between STM tip and impurity, in qualitative agreement with experiments, but is very sensitive to derails of the band structure. For a Co impurity the experimentally obs erved width and shift of the Kondo resonance are in accordance with those o btained from a combination of band structure and strongly correlated calcul ations.