Temperature dependence of the spectral profile of the Yosida–Kondo resonance for a single magnetic atom adsorbed on a metal surface

The Kondo temperature TK, for a system consisting of a magnetic atom adsorbed on a non-magnetic metal surface, is usually determined experimentally from the corresponding energy width of the dI/dV(V) spectra, at the vicinity of the Fermi level EF. However, the dI/dV(V) spectra could exhibit symmetric or asymmetric, dip or peak structures around V = 0, depending on the Fano parameter q (which gives us a measure of the spatial extent of the wavefunction function for the localized orbital—how far it protrudes—out of the surface, for a particular adsorbate–metal system). Determining the corresponding Kondo temperature TK for a magnetic adsorbate on a metal surface system is non-trivial and not so straightforward. Here, we propose another means to experimentally determine TK, and to check that the resonance observed experimentally does have the temperature dependence characteristic of the Kondo effect, i.e., by measuring the peak height of the second-derivative of the dI/dV(V) spectra at the vicinity of EF—d2I/dV2(V). We also provide a brief history of the Kondo effect and the events leading up to this present study.