Investigation of Edge States in Artificial Graphene Nano-Flakes

Graphene nano-flakes (GNFs) are predicted to host spin-polarized metallic edge states, which are envisioned for exploration of spintronics at the nanometer scale. To date, experimental realization of GNFs is only in its infancy because of the limitation of precise cutting or synthesizing methods at the nanometer scale. Here, we use low temperature scanning tunneling microscope (STM) to manipulate coronene molecules on a Cu(111) surface to build artificial triangular and hexagonal GNFs with either zigzag or armchair type of edges. We observe that the metallic edge states only exist in the GNFs with zigzag edge and localize at the most outside one type of the sublattice. The experimental results agree well with the tight-binding calculations. To our knowledge, our work renders the first systematic experimental confirmation of the predicated electronic properties of the GNFs.