Experimental variation and theoretical analysis of the inelastic contribution to atomic spin excitation spectroscopy

We investigate the dependence of the inelastic spin excitation contribution to scanning tunneling spectroscopy recorded above Fe adsorbates on the InSb(110) surface at subkelvin temperatures, on bulk doping, and tunnel junction resistance. To explain our observations, we show how the inelastic contribution depends on the parameters describing the excitation mechanism and tunnel conditions in the framework of a well-established model. We conclude that, in this particular system of an adsorbate that is strongly relaxed into the substrate, the tip-sample distance-dependent by- tunneling has to be taken into account in order to explain the observed variations in the inelastic tunnel spectra.