Abstract
The magnetic state and the Kondo effect in Mn phthalocyanine (MnPc) molecules on Pb(111) were investigated using low-temperature scanning tunneling microscopy (STM), density-functional theory, and numerical renormalization group calculations. We found that a unique spin state induced by the strong interaction between the Mn -orbitals and ligand π-orbitals causes an underscreened Kondo effect observed both at Mn and the ligand. STM observations show that a Kondo resonance extends over the pyrrole ring in the Pc ligand rather than remaining localized at Mn. In gas-phase MnPc, we reveal that the interaction result in an collective spin state extended over the Pc ligand with a complex spin polarization inside the molecule. On Pb(111), charge transfer from the substrate reduces the total spin of MnPc from 3/2 to 1 while the intramolecular interaction is maintained. Partial screening of this collective spin state by the conduction electron in Pb(111) makes the Kondo resonance also observed at the ligand part, which is not directly hybridized with the substrate.
- Received 22 January 2015
DOI:https://doi.org/10.1103/PhysRevB.92.075144
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