Toward Gate-Tunable Topological Superconductivity in a Supramolecular Electron Spin Lattice

Low-dimensional magnet/superconductor hybrid systems have been proposed as a platform for achieving topological superconductivity. Here we showcase the supramolecular assembly of organic radicals directly on superconducting Pb(111), whose charge state can be controlled from anionic to neutral by the electric field of the scanning tunneling microscope. The anionic molecules obtained by an electron given by the substrate carry a spin-1/2 state and form a two-dimensional spin lattice, as confirmed by the observation of Yu-Shiba-Rusinov subgap states in tunneling spectra. At the boundary of the molecular domains, low-energy subgap states appear localized with high intensity at edges compared to the interior of the island. Tight-binding simulations suggest that their localization and spectral signatures are consistent with the emergence of topologically protected modes. Our results pave the way for the design of organic/superconductor hybrid systems with the potential to realize topological superconductivity.