Spatial and temperature dependence of the spectroscopic profile of a magnetic atom adsorbed on a metal surface-Co/Cu(111)

As a representative Kondo system, consisting of a magnetic atom adsorbed on a metal surface, we consider a Co adatom on a Cu(111) surface. We introduce general expressions for the tunneling current and the differential conductance dI/dV, and discuss the corresponding spatial and temperature dependencies of the dI/dV line shapes that can be observed when the system is probed with a scanning tunneling microscope (STM). Starting with the STM tip sufficiently far from the Co adatom, the corresponding dI/dV line shape initially has an asymmetric structure about the Fermi level, which gradually becomes symmetric with decreasing STM tip–Co adatom distance, due to the competition between first-order (direct electron tunneling from the STM tip to the metal surface) and second-order (via the magnetic adsorbate) tunneling processes. The corresponding line shape also shows a strong temperature dependence, increasing in width with increasing temperature. As an aid to studying and observing these temperature dependenci...