Quantum size effects in Pb layers with absorbed Kondo adatoms: Determination of the exchange coupling constant

We consider the magnetic interaction of manganese phtalocyanine (MnPc) absorbed on Pb layers that were grown on a Si substrate. We perform an ab initio calculation of the density of states and Kondo temperature as a function of the number of Pb monolayers. Comparison to experimental data [Y.-S. Fu et al., Phys. Rev. Lett. 99, 256601 (2007)] then allows us to determine the exchange coupling constant $J$ between the spins of the adsorbed molecules and those of the Pb host. This approach gives rise to a general and reliable method for obtaining $J$ by combining experimental and numerical results.

Figure 1

(Color online) Top: total DOS at ${\epsilon }_F$ for a Pb(111) film on Si(111), depicted as a function of the number of Pb MLs. The values are normalized by the numbers of Pb atoms in the supercells. Bottom: zoom in for the 11–18 ML range.

Figure 2

(Color online) Kondo temperature as a function of the thickness of the Pb(111) film, given by the number of Pb MLs.