Figure 1

(a) Conductance $G$ versus tip displacement $\Delta z$. Top inset: Transition (II) from tunneling (I) to contact (III) regime. Bottom inset: Pseudo-three-dimensional representation of an STM image of a single Co atom. Conductance measurements were performed with the tip placed above the maximum height. (b) Spectra of $dI/dV$ acquired at conductances indicated in (a). Lowest curve: Spectrum of Cu(100) at $5\mu \mathrm{A}$. Curves 1, 2, 3: Spectra of single Co atom in the tunneling regime at 1, 10, and 100 nA. Curves 4, 5: Spectra of single Co atom in the contact regime at 5.5 and $6\mu \mathrm{A}$. Solid lines show calculated Fano profiles with $q=1.2$, $T_K=78\mathrm{K}$ (spectrum 3) and $q=2.1$, $T_K=137\mathrm{K}$ (spectrum 4).Reuse & Permissions

Figure 2

Kondo temperature $T_K$ versus tip displacement. Experimental data are depicted by circles; theoretical data are presented by triangles. The dashed line separates tunneling and contact regimes. Inset: Geometry of surface-adatom-tip setup for calculations.Reuse & Permissions

Figure 3

Density of $d$ states (DOS) versus tip displacement. Spin-up ($\uparrow$) and spin-down ($\downarrow$) DOS is plotted as positive and negative values, respectively. The $d\uparrow$ band is shifted toward the Fermi energy with decreasing displacement. Inset: Center of the $d$ band calculated statistically over occupied spin-up states.Reuse & Permissions