Magnetic and electronic properties of graphene/MOFene superlattices

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In the first funding period we established the manufacturing of heterostructures (HS) made from vertical stacks of graphene and a crystalline two-dimensional polymer. We thoroughly characterized and understood its structure and electronic structure on ground of theory and experiment. We investigated in silico the corrugation of the HS presence and absence of typical substrates and the impact of the corrugation on the band structure. r In a 2DPI/graphene HS we were able to show strong intralayer charge transfer, enhancement of spectral features as well as first indications of a bandgap opening in graphene due to the interlayer interaction. Having established the general strategy to access the nanoscale electronic properties of such HS both theoretically and experimentally, we will focus on the more subtle magnetic interactions between 2D metal-organic frameworks, so-called MOFenes, and various graphene systems (graphene and gated Bernal-stacked bilayer graphene, gBLG) during the second funding period. These frameworks contain metal centers as nodal elements connected by organic ligands, and the metal centers carry charge and/or spin centers. MOFenes with a characteristic lattice thus will impose a charge/magnetic superlattice of the same structure on any interfaced 2D material, such as graphene or gBLG. In such HSs we will be able to investigate effects of lattice topology and different metal centers on the resulting magnetism of the HS. We will explore magnetic and electronic intralayer coupling in the MOFenes of honeycomb, kagome and rhombic lattice topology both experimentally and theoretically. This allows to tune the intra versus interlayer magnetic coupling and thus the resulting macroscopic magnetic properties. Most intriguingly, we will be able to investigate the impact of magnetism and intralayer spin-orbit coupling of the MOFene on the intricate correlated states we recently identified in gBLG near its tunable van-Hove singularity. A central goal of these investigations is the understanding of superlattice effects of different topology. While for all lattices ferromagnetic and antiferromagnetic ordering of the magnetic centers is possible, in the kagome lattice spin frustration should either should give ferromagnetic ordering or a spin liquid. As interactions can be tuned by the choice of magnetic centers and ligands, such intriguing 2D spin-liquid systems will become feasible. This proposal employs a rich range of experimental and theoretical methods, including advanced material transfer techniques, quantum transport, scanning near-field microscopy, nanoscale scanning spectroscopy, orthogonal tight-binding hamiltonians, density-functional theory (DFT), DFT based tight-binding, and quasiparticle methods.