Engineering topological states in arrays of magnetic molecules through interaction with a 2 D superconductor

Recent investigation of ultrathin metal films with atomically well-defined thickness and high crystallinity has shown the existence of 2D superconductivity down to a single atomic layer as shown in Pb/Si(111) monolayers [1]. Pb/Si(111) has different surface structures depending on conditions of preparation such as the Pb coverage and the annealing temperature. Since this system consists of heavy atoms, there also exists a strong Rashba spin-orbit coupling (Rashba SOC) modifying the electronic properties. Pb/Si(111) grows by Stranski-Krastanov mode. Firstly, a wetting layer made up of a single atomic layer with a striped incommensurate reconstruction (SIC) is formed, then, Pb islands with specific thicknesses (3, 5, 7, ... monolayers) start to grow up on top of it. This bilayer growth arises from the presence of stabilising quantum size effects [4]. In order to maintain a relatively strong Rashba SOC we focused on the first stable thicknesses, i.e. 3 and 5 monolayers. On the top of the islands we observed different Moiré patterns, each with a specific corrugation and periodicity (Fig.1). Moiré patterns are dominated by substrate-mediated structural effects, e.g. lattice mismatch and misorientation between Si substrate and Pb overlayer, and/or atomic relaxation at the Pb/Si interface [5]. The coexistence of islands with different thicknesses and Moiré patterns highlights the role played by the different thicknesses and structures in self-assembly of MnPc molecules. Depending on the thickness and/or the Moiré on which molecules adsorb different molecular assemblies can be observed.