Theory of scanning tunneling microscopy of adsorbed molecules on metallic surfaces for nearly localized atomic states

Abstract

We consider a Hubbard-Anderson model which describes localized orbitals in five different sites hybridized both among themselves and with a continuum of extended states. A square planar geometry with an atom at the center is used to represent TBrPP-Co molecules. When the renormalized effective hopping between sites is small compared with a Kondo energy scale determined by the site-continuum hybridization, the system can be described as a set of independent Kondo resonances, rather than molecular states. We study the crossover between both regimes and analyze the spectral density of conduction electrons as a function of position. The results are in qualitative agreement with measurements of the differential conductance in a system with TBrPP-Co molecules adsorbed on a Cu(111) surface.