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ThPb is Tetraauricupride structured and crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. Th is bonded in a distorted body-centered cubic geometry to eight equivalent Pb atoms. All Th–Pb bond lengths are 3.44 Å. Pb is bonded in a body-centered cubic geometry to eight equivalent Th atoms.
ThPb crystallizes in the tetragonal I4_1/amd space group. The structure is three-dimensional. Th is bonded in a 4-coordinate geometry to eight equivalent Pb atoms. There are four shorter (3.33 Å) and four longer (3.65 Å) Th–Pb bond lengths. Pb is bonded in a 4-coordinate geometry to eight equivalent Th atoms.
Flat bands (FBs), presenting a strongly interacting quantum system, have drawn increasing interest recently. However, experimental growth and synthesis of FB materials have been challenging and have remained elusive for the ideal form of monolayer materials where the FB arises from destructive quantum interference as predicted in 2D lattice models. Here, we report surface growth of a self-assembled monolayer of 2D hydrogen-bond (H-bond) organic frameworks (HOFs) of 1,3,5-tris(4-hydroxyphenyl)benzene (THPB) on Au(111) substrate and the observation of FB. High-resolution scanning tunneling microscopy or spectroscopy shows mesoscale, highly ordered, and uniform THPB HOF domains, while angle-resolved photoemission spectroscopy highlights a FB over the whole Brillouin zone. Density-functional-theory calculations and analyses reveal that the observed topological FB arises from a hidden electronic breathing-kagome lattice without atomically breathing bonds. In conclusion, our findings demonstrate that self-assembly of HOFs provides a viable approach for synthesis of 2D organic topological materials, paving the way to explore many-body quantum states of topological FBs.