Kondo Effect in Distorted Titanium Phthalocyanine Molecules Adsorbed on a Cu(110) Metallic Surface

• Published in: Journal of physical chemistry. C 2024-05, Vol.128 (21), p.8767-8773
• Main Authors: Ribeiro, L. C., Lopes, Victor, Chiappe, G., Louis, E., Anda, E. V.
• Format: Article
• Language: English
• Subjects: C: Physical Properties of Materials and Interfaces
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/acs.jpcc.3c07751

In this work, we study the quantum transition taking place when titanium phthalocyanine molecules are adsorbed on a copper’s surface. Submitted to thermal annealing, depending on the way in which the molecule is adsorbed, this system can be characterized by a Kondo ground state, giving rise to a zero bias peak in the differential conductance. To clarify this new property, derived from the annealing process, we propose a model Hamiltonian that describes the essential physics involved. We show that the Kondo ground state appears as a consequence of the broken symmetry introduced by the annealing. It is not due to an increase of the molecule–substrate interactions but to the modification of the intermolecular lobe orbital matrix elements. This rearrangement rules the entrance of charge into the molecule and provides the conditions for the establishment of the Kondo state. Our results for the differential conductance, corresponding to the electronic current between a STM tip and one of the molecular lobes, agree with the experimental differential conductance measurements. It presents an Abrikosov–Suhl–Kondo resonance at the Fermi level for the configuration where the molecule is distorted. The results obtained within the model we propose, when compared with the experiments, give quantitative support to our interpretation.