Electron spin secluded inside a bottom-up assembled standing metal-molecule nanostructure

Artificial nanostructures, fabricated by placing atoms or molecules as building blocks in well-defined positions, are a powerful platform in which quantum effects can be studied and exploited. In particular, they offer the opportunity to reduce the electronic interaction between large aromatic molecules and the underlying metallic substrate, if the manipulation capabilities of scanning tunneling microscopy to lift the molecule into an upright geometry on a pedestal of two metal atoms are used. Here, we report a strategy to study this interaction by investigating the Kondo effect. Measurements at millikelvin temperatures and in magnetic fields reveal that this bottom-up assembled standing metal-molecule nanostructure has an S = 1/2 spin which is screened by substrate electrons, resulting in a Kondo temperature of only 291 +/- 13 mK. We extract its Lande g factor and its exchange coupling J rho to the substrate, using a third-order perturbation theory in the weak-coupling and high-field regimes. We also show that the interaction between the scanning tunneling microscope tip and the molecule can tune the exchange coupling.