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通过低温超高真空扫描隧道显微镜及其谱学方法研究并展示了分子配体在调控表面吸附的单个八乙基钴卟啉(Co OEP)分子的电子态和输运性质中的重要作用.通过单分子剪裁可以脱去该分子外围的甲基,并在中心钴原子的微分电导谱中观察测到d轨道共振到近藤共振的演变.实验结果结合第一性原理的理论计算研究表明,在脱去甲基前后中心钴原子的化学环境和磁矩均未发生显著变化,这一演变可以通过一个简化模型来阐释并被归结为脱去甲基后分子配体与衬底成键改变了体系隧穿参数所导致.此外,实验结果表明Co OEP分子配体的输运性质可受到分子间距离和范德华相互作用的显著调控.在Co OEP低聚体中位于分子之间的乙基被抬高,同时在其微分电导谱谱中0—0.8 V区域内新出现一个强的共振峰.这一新的共振峰表现出等间距的多峰细节,其峰间距与卟啉环和乙基之间的C—C键伸缩模式能量符合.这一新共振峰的出现被归结为由于分子局部与衬底耦合减弱形成双结隧穿体系所导致的振子态隧穿峰.
The important role of molecular ligands on the electronic states and transport properties of single octaethyl cobaltoporphyrins (Co OEP) adsorbed on the controlled surfaces was studied and demonstrated by cryogenic ultra-high vacuum scanning tunneling microscopy and spectroscopy. Single-molecule tailoring can take off the methyl group at the periphery of the molecule and observe the evolution of d-orbital resonance to Kondo resonance in the differential conductivity spectrum of the central cobalt atom.Experimental results Combined with the theoretical calculations of the first-principles theory, Both the chemical environment and the magnetic moment of the cobalt atom at the center of the demethyl group have not changed significantly. This evolution can be explained by a simplified model and is attributed to the debonding of the methyl group after the ligand and the substrate are changed. In addition, the experimental results show that the transport properties of Co OEP molecular ligands can be significantly regulated by the intermolecular distance and van der Waals interactions.Ethyl groups located between molecules in Co OEP oligomers are elevated, At the same time, a new strong resonance peak appears in the 0-0.8 V region of its differential conductivity spectrum.The new resonance peak shows equi-spaced multi-peak details with the peak spacing between the porphyrin ring and the ethyl group C-C bond stretching energy set mode. Emergence of this new resonance peak is attributed to the molecules due to the local weakening coupled with the substrate form a double tunneling junction system resulting peak tunneling state transducers.