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27 October 2003 Influence of the electron-phonon interactions on the transport properties at the molecular scale
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Abstract
In the present work we investigate the influence of molecular vibrations on the tunneling of electrons through a molecule sandwiched between two metal contacts. The study is confined to the elastic scattering only, but beyond the harmonic approximation. The problem is tackled both from a classical and a quantum-mechanical point of view. The classical approach consists in the computation of the time-dependent current uctuations calculated at each step of a molecular dynamics (MD) simulation. On the other hand, the vibrational modes are treated quantum-mechanically and the tunneling current is computed as an ensemble average over the distribution of the atomic configurations obtained by a suitable approximation of the density matrix for the normal mode oscillators. We show that the lattice fluctuations modify the electron transmission. At low temperatures the quantum-mechanical treatment is necessary in order to correctly include the zero-point fluctuations. However, for temperatures higher than few hundreds Kelvin the simple harmonic approximation which leads to the phonon modes breaks because the oscillation amplitudes of the lowest energy modes become large.
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Alessandro Pecchia, Marieta Gheorghe, Aldo Di Carlo, Thomas A. Niehaus, Reinard Scholz, Thomas Frauenheim, and Paolo Lugli "Influence of the electron-phonon interactions on the transport properties at the molecular scale", Proc. SPIE 5219, Nanotubes and Nanowires, (27 October 2003); https://doi.org/10.1117/12.507127
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