Self‐Organized Kagomé‐Lattice in a Conductive Metal‐Organic Monolayer

Abstract

AbstractThe on‐surface synthesis of metal‐organic covalent coordination networks with a dense Kagomé lattice of metallic centers is reported. Tetrahydroxyquinone and metal atoms (M = Cu or Mn) are codeposited on Ag(111) substrate to build well‐ordered 2D lattices M3C6O6. The surface is studied by scanning tunneling microscopy, low‐energy electron diffraction, and X‐ray photoelectron spectroscopy (XPS). Density functional theory (DFT) reveals a Cu+ charge state and no local magnetic moments for the Cu‐organic network. For the Mn‐organic network, the charge state Mn2+ and a local spin S = 5/2 are found. Charge transfer stabilizes the Cu+ and Mn2+ charge states. DFT calculations show a Dirac point, i.e., a band crossing with linear electron dispersion at the K‐point of the Brillouin zone. This Dirac point is at the Fermi level without charge transfer but drops by 100 meV if electron doping of Cu3C6O6 on Ag(111) surface is acknowledged. The magnetic couplings of an isolated Mn3C6O6 monolayer to be short range and antiferromagnetic leading to high frustration at the Kagomé lattice and a tendency toward a spin‐liquid ground state are predicted. In the case of hole transfer from the substrate, ferromagnetic ordering is introduced, making Mn3C6O6 an interesting candidate for the quantum anomalous Hall effect.