Quantifying the leading role of the surface state in the Kondo effect of Co/Ag(111)

Abstract

Using a combination of scanning tunneling spectroscopy and atomic lateral manipulation, we obtained a systematic variation of the Kondo temperature (TK) of Co atoms on Ag(111) as a function of the surface state contribution to the total density of states at the atom adsorption site (ρs). By sampling the TK of a Co atom on positions where ρs was spatially resolved beforehand, we obtain a nearly linear relationship between both magnitudes. We interpret the data on the basis of an Anderson model including orbital and spin degrees of freedom (SU(4)) in good agreement with the experimental findings. The fact that the onset of the surface band is near the Fermi level is crucial to lead to the observed linear behavior. In the light of this model, the quantitative analysis of the experimental data evidences that at least a quarter of the coupling of Co impurities with extended states takes place through the hybridization to surface states. This result is of fundamental relevance in the understanding of Kondo screening of magnetic impurities on noble metal surfaces, where bulk and surface electronic states coexist.

Relation between width of zero-bias anomaly and Kondo temperature in transport measurements through correlated quantum dots: Effect of asymmetric coupling to the leads

“…This is important, since T NE is widely used as an estimation of T K in different classes of experiments. 59,[63][64][65][66][67][68][69] For example, in Ref. 64 a "Kondo temperature" T NE = 92 K for a Co impurity on Ag(111) is reported, while in Ref.…”

Kondo physics of magnetic adatoms on metallic surfaces when the onset of the surface conduction density of states crosses the Fermi level

“…In particular we choose the ratio ∆ s /∆ b = 1/4 which has found to be the lower limit for the surface contribution to the total hybridization in Co impurities deposited on Ag(111) surface. 16 What we observed from the plot is that while the negative portion of the Kondo resonance approaches to one when scaled by π∆ b , the positive one reaches the same value but when it is scaled by π(∆ b + ∆ s ). Note that for the selected parameters the Kondo resonance is slightly asymmetric with more weight in the negative region, so it is closer to one for negative energies than for the positive ones.…”

“…In addition to the Limot's experiment, the Moro-Lagares and co-workers one in Ref. 16, also study the Kondo phenomena that appears after deposition of a Co atom on a clean Ag(111) surface. In that work, the main result is a quantification of the role of the surface state in the Kondo effect and provides a lower bound for the ratio of hybridizations r sb = ∆ s /∆ b = 1/4.…”

“…Several experiments were made to study atomic impurities (such as Co or Mn) over such surfaces. 3,5,[12][13][14][15][16][17][18] Moreover, complex magnetic molecules were also deposited on Ag, Cu and Au surfaces like FePc 19,20 among others. With help of low-temperature STM measurements, in these systems the Kondo effect have been studied.…”

Fully compensated Kondo effect for a two-channel spin S=1 impurity

“…A difference between the bulk systems and the low dimensional QD ones is that while in the former the fully screened scenario n = 2S is frequent 38 , it seems rare in the latter. However, as stated above, there are several studies on nanoscopic systems with S > 1/2 and also with degenerate orbitals 25,37,[39][40][41] so that this scenario is expected to appear in the future. In particular, recently a realization of the fully compensated high spin Kondo phenomena in a low-dimensional system has been proposed 42 .…”