Design and Synthesis of a Single-Layer Ferromagnetic Metal- Organic Framework with Topological Nontrivial Gaps

We report on the design and synthesis of a two-dimensional metal-organic framework Fe-3(HITP)(2) which comprises of a Kagome sublattice of Fe atoms. Density-functional theory calculations reveal that this framework has a ferromagnetic ground state with several topological nontrivial gaps opened due to the spin-orbit coupling, signifying quantum anomalous Hall features. Experimentally, we synthesize this structure by means of on-surface coordination self-assembly on an Au(111) substrate. We resolve its structure at a single-molecule resolution using scanning tunneling microscopy and confirm that the on-surface structure is nearly identical to the free-standing framework. We use scanning tunneling spectroscopy to study its electronic properties. A zero-bias resonance localized at the Fe atoms indicates that a magnetic moment is present at the Kagome lattice. Our results demonstrate the viability of realizing 2D organic quantum anomalous Hall systems.