Graphyne (GY) and graphdiyne (GDY)-based monolayers represent the next generation 2D carbon-rich materials with tunable structures and properties surpassing those of graphene. However, the detection of band formation in atomically thin GY/GDY analogues has been challenging, as both long-range order and atomic precision have to be fulfilled in the system. The present work reports direct evidence of band formation in on-surface synthesized metallated Ag-GDY sheets with mesoscopic (≈1 µm) regularity. Employing scanning tunneling and angle-resolved photoemission spectroscopies, energy-dependent transitions of real-space electronic states above the Fermi level and formation of the valence band are respectively observed. Furthermore, density functional theory (DFT) calculations corroborate the observations and reveal that doubly degenerate frontier molecular orbitals on a honeycomb lattice give rise to flat, Dirac and Kagome bands close to the Fermi level. DFT modeling also indicates an intrinsic band gap for the pristine sheet material, which is retained for a bilayer with h-BN, whereas adsorption-induced in-gap electronic states evolve at the synthesis platform with Ag-GDY decorating the (111) facet of silver. These results illustrate the tremendous potential for engineering novel band structures via molecular orbital and lattice symmetries in atomically precise 2D carbon materials.

中文翻译：

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表面限制金属化石墨炔片中结合分子轨道和晶格对称性的非常规能带结构


基于石墨炔（GY）和石墨二炔（GDY）的单分子层代表了下一代二维富碳材料，其结构和性能均优于石墨烯。然而，原子薄 GY/GDY 类似物中能带形成的检测一直具有挑战性，因为系统必须满足长程有序性和原子精度。目前的工作报告了表面合成金属化 Ag-GDY 片材中带形成的直接证据，具有介观（约 1 µm）规律性。采用扫描隧道效应和角度分辨光电发射光谱，分别观察到费米能级以上的实空间电子态的能量依赖性跃迁和价带的形成。此外，密度泛函理论 (DFT) 计算证实了观察结果，并揭示了蜂窝晶格上的双简并前沿分子轨道产生了接近费米能级的平坦能带、狄拉克能带和 Kagome 能带。 DFT 模型还表明原始片材的固有带隙，该带隙保留为具有 h-BN 的双层，而吸附诱导的带隙内电子态在合成平台上演化，Ag-GDY 装饰了 (111) 面银。这些结果说明了通过原子精确的二维碳材料中的分子轨道和晶格对称性设计新颖的能带结构的巨大潜力。