Flat bands and Dirac cones in magnetic 2D metal-organic frameworks*

Metal-organic frameworks (MOFs) are interesting crystals for exploring new physics due to their tunable structure and chemical composition. 2D magnetic MOFs are of particular interest, and a composite kagome-honeycomb lattice was recently realized in a reported ferrimagnetic iron-semiquinone MOF [1]. Via molecular orbital and tight-binding analysis, and with density functional theory-based calculations, we study the iron-semiquinone MOF and show that its band structure contains multiple flatbands as well as multiple Dirac cones. We find that the MOF is semimetallic, with the Fermi level at a Dirac point; and the calculated magnetization is consistent with the reported experimental value. We also explore the effects of spin-orbit coupling and comment on the magnetism of related 2D MOFs; we also discuss how our tight-binding model might be generalized to other 2D MOFs of interest.

[1]I.-R. Jeon, B. Negru, R. P. Van Duyne, and T. D. Harris, J. Am. Chem. Soc. 137, 15699 (2015).