Multichannel excitation of the Yu-Shiba-Rusinov states of a molecular spin

Carmen Rubio-Verdú, Javier Zaldívar, Rok Žitko, Jose Ignacio Pascual

Published 2020-07-23Version 1

A magnetic impurity on a superconductor induces Yu-Shiba-Rusinov (YSR) bound states, detected in tunneling spectroscopy as narrow in-gap excitations. Hund's coupling is the energy scale that determines the impurity's magnetic ground state. However, experimental evidence that links the YSR nature with such fundamental intra-atomic exchange remains elusive. We report multichannel YSR states in a many-body molecular spin. We found that a magnetic porphyrin on Pb(111) exhibits two distinct YSR orbital interaction channels with identical intramolecular distribution of their particle-hole asymmetry. Supported by numerical calculations, we show that the YSR asymmetry is caused by orbitals with opposite potential scattering, coupled into a robust, spin-hosting molecular state, which also governs its normal state properties. Our results depict a new scenario for the study of entangled spin systems on superconductors using molecular platforms.