Abstract
Using a combination of scanning tunneling spectroscopy and atomic lateral manipulation, we obtained a systematic variation of the Kondo temperature ($T_\mathrm K$) 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 ($\rho_s$). By sampling the $T_\mathrm K$ of a Co atom on positions where $\rho_s$ 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.
Highlights
En este trabajo se presenta un estudio detallado del efecto Kondo que ocurre en moléculas y átomos colocados sobre superficies metálicas
The results show a simple power law for the magnitude temperatura de Kondo” (TK) as a function of Dis is found, which depends on weight of the hybridizations between the magnetic impurity and the surface and bulk states, as well as on the one-site energy and Coulomb repulsion
Antes de discutir el modelo que tiene en cuenta la punta del scanning tunneling microscope (STM), resulta pertinente analizar las ecuaciones resultantes teniendo en cuenta la presencia de estados superficiales y volumétricos en el metal, puesto que en esta tesis se hace especial hincapié en el impacto de los primeros en la resonancia Kondo
Summary
En este trabajo se presenta un estudio detallado del efecto Kondo que ocurre en moléculas y átomos colocados sobre superficies metálicas. El experimento muestra que la densidad espectral de los estados superficiales medida por la conductancia diferencial G(V ) = dI/dV con un microscopio de efecto túnel (STM) puede sufrir modificaciones si se introducen arreglos simples de átomos de cobalto colocados sobre la superficie. Los resultados que se extraen de este modelo evidencian la importancia de los estados superficiales en la temperatura de Kondo, que normalmente son menospreciados en la literatura, y constatan a su vez la relevancia del comienzo de la banda de conducción superficial en estos sistemas. Palabras clave: MODELO DE LA IMPUREZA DE ANDERSON, APROXIMACIÓN “NON-CROSSING”, BOSONES ESCLAVOS EN CAMPO MEDIO, “POOR MAN’S SCALING”, MICROSCOPIO DE EFECTO TÚNEL, DENSIDAD LOCAL DE ESTADOS, COBALTO, SUPERFICIE DE PLATA, FTALOCIANINA DE HIERRO, SUPERFICIE DE ORO
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