Current-induced atomic dynamics, instabilities, and Raman signals: Quasiclassical Langevin equation approach

Jing Tao Lu, Mads Brandbyge, Per Hedegard, Tchavdar N. Todorov, Daniel Dundas

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    Abstract

    We derive and employ a semiclassical Langevin equation obtained from path integrals to describe the ionic dynamics of a molecular junction in the presence of electrical current. The electronic environment serves as an effective nonequilibrium bath. The bath results in random forces describing Joule heating, current-induced forces including the nonconservative wind force, dissipative frictional forces, and an effective Lorentz-type force due to the Berry phase of the nonequilibrium electrons. Using a generic two-level molecular model, we highlight the importance of both current-induced forces and Joule heating for the stability of the system. We compare the impact of the different forces, and the wide-band approximation for the electronic structure on our result. We examine the current-induced instabilities (excitation of runaway "waterwheel" modes) and investigate the signature of these in the Raman signals.
    Original languageEnglish
    JournalPhysical Review B Condensed Matter
    Volume85
    Issue number24
    Pages (from-to)Paper 245444
    Number of pages16
    ISSN0163-1829
    DOIs
    Publication statusPublished - 2012

    Bibliographical note

    ©2012 American Physical Society

    Keywords

    • Physics
    • Electron-Tunneling Spectroscopy
    • Molecular-Transport Junctions
    • Current-Induced Forces
    • Gold Atoms
    • Conductance
    • Contacts
    • Microscopy
    • Scattering
    • Energy
    • Motion

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