Topological phases in laterally confined low-dimensional nanographenes have emerged as versatile design tools that can imbue otherwise unremarkable materials with exotic band structures ranging from topological semiconductors and quantum dots to intrinsically metallic bands. The periodic boundary conditions that define the topology of a given lattice have thus far prevented the translation of this technology to the quasi-zero-dimensional (0D) domain of small molecular structures. Here, we describe the synthesis of a polycyclic aromatic hydrocarbon (PAH) featuring two localized zero modes (ZMs) formed by the topological junction interface between a trivial and nontrivial phase within a single molecule. First-principles density functional theory calculations predict a strong hybridization between adjacent ZMs that gives rise to an exceptionally small HOMO–LUMO gap. Scanning tunneling microscopy and spectroscopy corroborate the molecular structure of 9/7/9-double quantum dots and reveal an experimental quasiparticle gap of 0.16 eV, corresponding to a carbon-based small molecule long-wavelength infrared (LWIR) absorber.

中文翻译：

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具有拓扑保护态的多环芳烃中的小HOMO-LUMO能隙的工程

横向限制的低维纳米石墨烯中的拓扑相已成为多功能设计工具，可以为原本不起眼的材料注入从拓扑半导体和量子点到本质金属带的奇异能带结构。迄今为止，定义给定晶格拓扑的周期性边界条件阻碍了该技术向小分子结构的准零维（0D）域的转化。在这里，我们描述了多环芳烃（PAH）的合成，该多环芳烃（PAH）具有由单个分子内的平凡相和非平凡相之间的拓扑连接界面形成的两个局域零模式（ZM）。第一性原理密度泛函理论计算预测相邻 ZM 之间存在强杂化，从而产生极小的 HOMO-LUMO 间隙。扫描隧道显微镜和光谱证实了 9/7/9 双量子点的分子结构，并揭示了 0.16 eV 的实验准粒子能隙，对应于碳基小分子长波红外 (LWIR) 吸收体。