Electronic transport in biphenyl single-molecule junctions with carbon nanotubes electrodes: The role of molecular conformation and chirality

摘要

We investigate, by means of ab initio calculations, electronic transport in molecular junctions composed of a biphenyl molecule attached to metallic carbon nanotubes. We find that the conductance is proportional to cos~2 θ, with θ the angle between phenyl rings, when the Fermi level of the contacts lies within the frontier molecular orbitals energy gap. This result, which agrees with experiments in biphenyl junctions with nonor-ganic contacts, suggests that the cos~2 θ law has a more general applicability, irrespective of the nature of the electrodes. We calculate the geometrical degree of chirality of the junction, which only depends on the atomic positions, and demonstrate that it is not only proportional to cos~2 θ but also is strongly correlated with the current through the system. These results indicate that molecular conformation plays the preponderant role in determining transport properties of biphenyl-carbon nanotubes molecular junctions.