Probing the Kondo screening cloud via tunneling-current conductance fluctuations

We show that conductance fluctuations or noise in the conductance of a tunneling current into an interacting electron system is dominated by density-density and (or) spin-spin correlations. This allows one to probe two-particle properties (susceptibilities) and collective excitations by standard experimental tunneling methods. We demonstrate this theoretically, using a many-body calculation for the single-adatom Kondo problem. An example of the two-particle correlations around a single magnetic adatom in the Kondo regime, as would be viewed by a scanning tunneling microscope, is given. The spatial dependence of the local spin and charge correlations of the substrate exhibits a clear signature of the Kondo screening cloud.