Nonequilibrium electron-vibration coupling and conductance fluctuations in a C60 junction

Søren Ulstrup, Thomas Frederiksen, Mads Brandbyge

    Research output: Contribution to journalJournal articleResearchpeer-review

    Abstract

    We investigate chemical bond formation and conductance in a molecular C60 junction under finite bias voltage using first-principles calculations based on density functional theory and nonequilibrium Green's functions (DFT-NEGF). At the point of contact formation we identify a remarkably strong coupling between the C60 motion and the molecular electronic structure. This is only seen for positive sample bias, although the conductance itself is not strongly polarity dependent. The nonequilibrium effect is traced back to a sudden shift in the position of the voltage drop with a small C60 displacement. Combined with a vibrational heating mechanism we construct a model from our results that explain the polarity-dependent two-level conductance fluctuations observed in recent scanning tunneling microscopy (STM) experiments [N. Ne´el et al., Nano Lett. 11, 3593 (2011)]. These findings highlight the significance of nonequilibrium effects in chemical bond formation/breaking and in electron-vibration coupling in molecular electronics.
    Original languageEnglish
    JournalPhysical Review B Condensed Matter
    Volume86
    Issue number24
    Pages (from-to)245417
    ISSN0163-1829
    Publication statusPublished - 2012

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