School of Physics and Information Technology, Shaanxi Normal University, Xi'an 710119, China.
School of Physics, Huazhong University of Science and Technology, Wuhan 430074, China.
Phys Rev Lett. 2023 Jan 20;130(3):036203. doi: 10.1103/PhysRevLett.130.036203.
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. 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.
平面带（FB）是一种强相互作用的量子体系，最近引起了越来越多的关注。然而，实验上生长和合成 FB 材料一直具有挑战性，并且对于理想形式的单层材料（即 FB 是由二维晶格模型中预测的破坏性量子干涉引起的），FB 仍然难以捉摸。在这里，我们报告了二维氢键（H-bond）有机框架（HOF）的自组装单层 1,3,5-三（4-羟基苯基）苯（THPB）在 Au（111）衬底上的表面生长，并观察到了 FB。高分辨率扫描隧道显微镜或光谱学显示了介观、高度有序和均匀的 THPB HOF 畴，而角分辨光电子能谱则突出了整个布里渊区的 FB。密度泛函理论计算和分析表明，观察到的拓扑 FB 来自于没有原子呼吸键的隐藏电子呼吸 kagome 晶格。我们的发现表明，HOF 的自组装为合成二维有机拓扑材料提供了一种可行的方法，为探索拓扑 FB 的多体量子态铺平了道路。
