Exploring the lead dependence of single-molecule conductance from first principles: The case of H$_{2}$ molecular junctions

ORAL

Abstract

Although the transport properties of several single-molecule junctions have now been reported, only a few studies have systematically examined the sensitivity of the junction conductance to the choice of metallic contacts. Recent break-junction experiments have revealed significantly lower conductance for H$_{2}$ molecular junctions when Pt leads were replaced with Pd,$^{1,2}$ suggesting a dramatic difference in electronic coupling between the molecule and lead. In this work, we examine this coupling directly by computing the conductance of H$_{2}$ with several different metallic contacts using an \textit{ab-initio} scattering state approach$^{3 }$ based on density functional theory.$^{ }$We find that by substituting Pt with Pd leads, the low-bias electron transport crosses over from a ballistic to an off-resonance tunneling regime, leading to a conductance smaller than unity in agreement with experiments. The extent to which substituting different leads may be used to tune the transport properties of this and other simple single-molecule junctions will be discussed. This work was supported by the NSF Grant No. DMR04-39768 and U.S. DOE Contract No. DE-AC03-76SF00098. [1] R. H. M. Smit \textit{et al.}, Nature (London) \textbf{419}, 906 (2002). [2] Sz. Csonka \textit{et al.}, Phys. Rev. Lett. \textbf{93}, 016802 (2004). [3] H.J. Choi, M.L. Cohen and Steven G. Louie, to be published.

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Authors

  • Amy Khoo

    Department of Physics UC Berkeley, Dept of Physics, UC Berkeley

  • Jeffrey Neaton

    The Molecular Foundry, Materials Sciences Division, Lawrence Berkeley National Laboratory, The Molecular Foundry, LBNL, The Molecular Foundry, Material Science Devision, Lawrence Berkeley National Laboratory, Berkeley CA 94720

  • Steven Louie

    Department of Physics, University of California, Berkeley \& The Molecular Foundry, Materials Sciences Division,Lawrence Berkeley National Laboratory, University of California at Berkeley and Lawrence Berkeley National Laboratory, UC Berkeley and Lawrence Berkeley National Laboratory, Department of Physics, University of California at Berkeley and Materials Sciences Division, LBNL, Dept of Physics, UC Berkeley, The Molecular Foundry, LBNL, University of California at Berkeley, Department of Physics, University of California at Berkeley and Materials Sciences Divisions, LBNL