Detection and Manipulation of Interaction Between Magnetic DyPc2 Molecules and Superconducting Pb(111) Surface

Abstract

Lanthanide double-decker phthalocyanine (LnPc₂) complexes are highly coveted for their prospective uses in ultrahigh-density data storage and quantum computing. Notably, the quantum spin systems comprising these complexes and superconducting substrates exhibit unique quantum magnetic interactions. Through scanning tunneling microscopy (STM) and spectroscopy (STS) experiments, the interaction between the magnetic double-decker DyPc₂ molecules and the superconducting Pb(111) substrate is investigated. Three distinct adsorption patterns of DyPc₂ on Pb(111) are experimentally observed. Combined with DFT calculations, it is found that the ligand spin of the normal DyPc₂ molecules in the self-assembled monolayer (SAM) is quenched, which is attributed to strong charge transfer from Pb(111). However, special DyPc₂ molecules embedded in the SAM maintain ligand spin due to weak charge transfer, forming a complex quantum spin system with the superconducting substrate. Similarly, DyPc₂ molecules located on the second layer exhibit the same behavior. Under zero magnetic field, the Yu–Shiba–Rusinov (YSR) resonances are observed within the superconducting energy gap of both spin quantum systems. The Kondo resonance and the superconducting pairing occur at similar energy scales, indicating their coexistence and competition. This ultimately results in a Kondo-screened state. By controlling the sample bias, the special molecule can be switched to a normal molecule.