Electron spin lattices on superconductors offer a promising platform for quantum technologies. They can serve as qubits in quantum computing or provide a basis for exploring exotic quantum phases, such as spin liquids and topological superconductivity. However, constructing and scaling up these artificial lattices while maintaining precise gate tunability remains a significant experimental challenge.

In our work, we demonstrate the supramolecular assembly of 4,5,9,10-tetrabromo-1,3,6,8tetraazapyrene (TBTAP) molecules on a superconducting Pb(111) surface, forming a compact electron (spin) superlattice consisting of coexisting neutral TBTAP and singly charged TBTAP species. Using tunneling and force spectroscopy, we identify the signature of a discharging event in the charged TBTAP molecules.

This event is triggered by capacitive coupling between the molecular charge state and the local electric field from the STM/AFM tip, enabling a controlled transition from the anionic to the neutral state as a function of the applied tip voltage. Our results demonstrate a new pathway for the bottom-up construction of gatetunable, high-density spin networks, offering a powerful platform for investigating electron correlation effects and emergent quantum phenomena at the molecular scale.

Carl Drechsel, Silvio Decurtins, Ulrich Aschauer,  Shi-Xia Liu, Jung-Ching Liu, Xinyi Liu, Robert Häner, Ernst Meyer, Rémy Pawlak. Discharge and electron correlation of radical molecules in a supramolecular assembly on superconducting Pb(111)  DOI: 10.1039/d5nh00462d