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

TL;DR

This study computationally demonstrates that metal-free 2D polymers with honeycomb lattices can exhibit both Stoner ferromagnetism and Mott-Hubbard insulating behavior, revealing new magnetic phenomena in conjugated organic materials.

Contribution

It introduces a new class of 2D polymers that display both Stoner and Mott-Hubbard magnetism, expanding the understanding of magnetic properties in organic conjugated systems.

Findings

Presence of long-range magnetic order in 2D polymers.

Observation of flat bands and Dirac cones in the electronic structure.

Identification of conditions leading to either ferromagnetic or antiferromagnetic states.

Abstract

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 {\pi} 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.