PhD Thesis Defense: Proximity-Induced Superconductivity on Noble Metals as a Platform for Molecular Magnetism

This thesis investigates proximity-induced superconductivity in noble-metal films and its interaction with molecular and carbon-based spin systems. These hybrid platforms enable the study of interactions between localized magnetic moments and superconducting condensates, with relevance to spintronics, quantum devices, and topological superconductivity. Using low-temperature scanning tunneling microscopy and spectroscopy (STM/STS) combined with X-ray photoelectron spectroscopy (XPS), ultrathin Au films grown on elemental superconductors are characterized. The proximitized Au layers exhibit a well-defined superconducting gap while preserving molecular magnetism and strongly enhancing molecular spin lifetimes, exceeding 80 ns for FeTPP-Cl excitations. Yu–Shiba–Rusinov states are observed, revealing exchange coupling between molecular spins and the superconducting state.

 

In parallel, epitaxial Ag(111)-like films grown on Nb display a robust proximity-induced gap comparable to that of the bulk superconductor and support on-surface synthesis of carbon-based nanostructures. On this platform, magnetism in triangulene systems is shown to arise from defect-induced states rather than the ideal molecular backbone. To overcome limitations related to charge transfer and magnetic quenching, a Au(111)/Ag/Nb heterostructure is developed. This architecture suppresses intermixing while maintaining a strong proximity effect, with Au films retaining up to 50% of the Nb gap at large thicknesses and enabling high-quality on-surface synthesis.

 

Triangulene spin chains assembled on this platform realize Haldane spin-1 chains with atomic precision. Odd-length chains host Yu–Shiba–Rusinov edge states, while even-length chains exhibit singlet–triplet edge excitations. Overall, this work establishes proximitized noble-metal films as versatile platforms for engineering superconducting–magnetic quantum materials and integrating carbon-based magnetism with superconductivity.