Molecular Interactions at Organic-Inorganic Interfaces: Formation of Kagome Lattices

The experimental realization of kagome lattices, where predicted topological states coexist with high electron mobility and flat-band quantum states, has been limited to date. In this work, we study the formation of a kagome-like structure through the electrostatic self-assembly of 4,7-dibromobenzo[c]-1,2,5-thiadiazole (2Br-BTD) molecules on an Au(111) surface. Utilizing local spectroscopic measurements and theoretical simulations, we reveal that although inter-molecular and molecular-surface interactions are relatively weak, electron interference plays a crucial role in reshaping the band structure of Au(111), enabling the emergence of topological states. These states are characterized by electron localization within the hexagonal and triangular sublattices of the kagome configuration, confined within the molecular HOMO-LUMO gap at energies 150, 500, and 850 meV. These states originate from the Au substrate, but the interaction between the 2Br-BTD molecules and the Au surface leads to the formation of these localized electronic regions. We also find the robustness of these states against temperature variations and structural disorder, underscoring their topological protection and holding fundamental implications for their potential applications.