Density-functional study of tilt-angle and temperature-dependent conductance in biphenyl dithiol single-molecule junctions

F. Pauly, J. K. Viljas, J. C. Cuevas, and Gerd Schön
Phys. Rev. B 77, 155312 – Published 9 April 2008

Abstract

In the framework of a density-functional-based method, we study electron transport through several biphenyl-derived dithiol molecules connected to gold electrodes. The molecules differ in the degree of conjugation of the π-electron system, which is controlled by the choice of the side groups. The low-temperature conductance depends on the tilt angle φ between the two phenyl ring units and follows closely a cos2φ law consistent with an effective π-orbital coupling model. Tilting the phenyl rings from a planar conformation to one with perpendicular rings decreases the conductance by roughly 2 orders of magnitude. These findings are in agreement with experiments. We further study the temperature dependence of both the conductance and its fluctuations and find qualitative differences between the investigated molecules. The temperature dependence arises from thermal smearing in the leads and also from a thermal average over different contact configurations. Our results suggest that the variations of the conductance due to the latter effect can be reduced by an appropriate design of the molecule.

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  • Received 22 May 2007

DOI:https://doi.org/10.1103/PhysRevB.77.155312

©2008 American Physical Society

Authors & Affiliations

F. Pauly1,2,*, J. K. Viljas1,2, J. C. Cuevas1,2,3, and Gerd Schön1,2

  • 1Institut für Theoretische Festkörperphysik and DFG-Center for Functional Nanostructures, Universität Karlsruhe, 76128 Karlsruhe, Germany
  • 2Institut für Nanotechnologie, Forschungszentrum Karlsruhe, 76021 Karlsruhe, Germany
  • 3Departamento de Física Teórica de la Materia Condensada, Universidad Autónoma de Madrid, 28049 Madrid, Spain

  • *fabian.pauly@kit.edu

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Vol. 77, Iss. 15 — 15 April 2008

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