Metal-free Stoner and Mott-Hubbard magnetism in 2D polymers with honeycomb lattice

We computationally demonstrate Stoner-ferromagnetic half-metals and antiferromagnetic Mott-Hubbard insulators in metal-free 2D polymers. Coupling radicaloid (hetero)triangulene monomers via strong covalent bonds preserving the in-plane conjugation of the electronic π system yields 2D crystals with long-range magnetic order and magnetic couplings above the Landauer limit. Dual-site honeycomb lattices produce both flat bands and Dirac cones. Depending on the monomers, electron correlations lead to either a bandgap at the Dirac points for antiferromagnetic Mott insulators, or Stoner ferromagnetism with both spin-polarized Dirac cones and flat bands at the Fermi level. These results pioneer a new type of Stoner and Mott-Hubbard magnetism emerging in the electronic pi system of crystalline conjugated 2D polymers.