Würzburg ToCoTronics Colloquium

Spectroscopic low-energy excitations as Kondo resonances, Yu-Shiba Rusinov (YSR) states and inelastic spin excitations are sensitive fingerprints of magnetism in atomic scale structures. We studied a variety of different molecules, all of them being diamagnetic in gas-phase, using low temperature scanning tunneling spectroscopy (STS). In suitable molecular environments the lowest unoccupied molecular orbital is found to become partially occupied leading to magnetic signatures in the tunneling spectra that can be fine-tuned using supramolecular manipulation and molecular switching. In addition to the spin moment, orbital contributions related to molecular ring-currents lead to a surprisingly large splitting of the Kondo resonance in a magnetic field. When YSR states are present, their amplitude exceeds the normal-state conductance up to a factor of 50, resulting in a large number of sharp inelastic peaks from molecular vibrations that become discernible in STS. Magnetic and vibrational signatures are spatially mapped and small shifts of their energy below 100 µeV are resolved when manipulating neighboring molecules.