Some aspects of electron-phonon interactions and transport properties in molecular junctions

Orateur : Remi AVRILLER (LOMA)

Molecular electronics represents the ultimate limit of the “up-bottom” miniaturization process initiated by the semiconductor industry. Along this path, the laws of quantum mechanics have been found to impose fundamental limitations, especially in the ultimate case of molecular and atomic sized electronic junctions. Despite several decades of investigations, a global understanding of current-voltage characteristics I(V), mechanical stability and heat losses of such molecular junctions is still lacking. A key mechanism for understanding all this phenomena lies in the coupling between electronic degrees of freedom (giving rise to an electronic current) and local vibrational modes of the junction (phonons giving rise to dissipation). This seminar aims at reviewing recent advances in this field of research. In particular, we will show that, due to inelastic scattering with phonons, some information about electronic and vibrational properties of the junction, electronic correlations and effective lattice temperature is encoded into the electrical current noise curves (“shot-noise”), that is not present in standard I(V) characteristics. This opens up new technological perspectives and complementary spectroscopic tools at the nanoscale. We will present the first experimental evidence of this phenomenon [1] as well as its theoretical analysis, based on a recently developed ab initio methodology [2]. Finally, we will provide a general picture and connect those results to recent theoretical advances [3] and opened problems dealing with the investigation of the full counting statistics of charge transfer in presence of electron-phonon interactions.

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