Quantum interference in coherent tunneling through branched molecular junctions containing ferrocene centers

• Published in: Physical review. B 2017-08, Vol.96 (8), Article 085421
• Main Authors: Zhao, Xin, Kastlunger, Georg, Stadler, Robert
• Format: Article
• Language: English
• Subjects: Anchors; Charging; Coupling (molecular); Density functional theory; Green's functions; Interference; Molecular orbitals; Resistance
• ISSN: 2469-9950; 2469-9969
• DOI: 10.1103/PhysRevB.96.085421

In our theoretical study where we combine a nonequilibrium Green's function approach with density functional theory we investigate branched compounds containing ferrocene moieties in both branches which, due to their metal centers, are designed to allow for asymmetry induced by local charging. In these compounds the ferrocene moieties are connected to pyridyl anchor groups either directly or via acetylenic spacers in a metaconnection, where we also compare our results with those obtained for the respective single-branched molecules with both meta- and paraconnections between the metal center and the anchors. We find a destructive quantum interference (DQI) feature in the transmission function slightly below the lowest unoccupied molecular orbital, which dominates the conductance even for the uncharged branched compound with spacer groups inserted. In an analysis based on mapping the structural characteristics of the range of molecules in our article onto tight-binding models, we identify the structural source of the DQI minimum as the through-space coupling between the pyridyl anchor groups. We also find that local charging in one of the branches changes the conductance only by about one order of magnitude, which we explain in terms of the spatial distributions of the relevant molecular orbitals for the branched compounds.