A functional renormalization group application to the scanning tunneling microscopy experiment

We present a study of a system composed of a scanning tunneling microscope (STM) tip coupled to an absorbed impurity on a host surface using the functional renormalization group (FRG). We include the effect of the STM tip as a correction to the self-energy in addition to the usual contribution of the host surface in the wide band limit. We calculate the differential conductance curves at two different lateral distances from the quantum impurity and find good qualitative agreement with STM experiments where the differential conductance curves evolve from an antiresonance to a Lorentzian shape.