The image charge effect and vibron-assisted processes in Coulomb blockade transport: a first principles approach

Abstract
We present a combination of density functional theory and of both non-equilibrium Green's function formalism and a Master equation approach to accurately describe quantum transport in molecular junctions in the Coulomb blockade regime. We apply this effective first-principles approach to reproduce the experimental results of Perrin et al., [Nat. Nanotechnol., 2013, 8, 282] for the transport properties of a Au–(Zn)porphyrin–Au molecular junction. We demonstrate that energy level renormalization due to the image charge effect is crucial to the prediction of the current onset in the current–voltage, I–V, curves as a function of electrode separation. Furthermore, we show that for voltages beyond that setting the current onset, the slope of the I–V characteristics is determined by the interaction of the charge carriers with molecular vibrations. This corresponds to current-induced local heating, which may also lead to an effective reduced electronic coupling. Overall our scheme provides a fully ab initio description of quantum transport in the Coulomb blockade regime in the presence of electron–vibron coupling.

Citation
Souza, A. M., Rungger, I., Schwingenschlögl, U., & Sanvito, S. (2015). The image charge effect and vibron-assisted processes in Coulomb blockade transport: a first principles approach. Nanoscale, 7(45), 19231–19240. doi:10.1039/c5nr04245c

Acknowledgements
The authors are thankful to the King Abdullah University of Science and Technology (Kingdom of Saudi Arabia) for the financial support through the ACRAB project, to the Trinity College High-Performance Computer Center (TCHPC) and the Ireland’s High-Performance computing centre (ICHEC) for computational resources. Additional support was provided by the European Research Council (Quest and HINTS projects).

Publisher
Royal Society of Chemistry (RSC)

Journal
NANOSCALE

DOI
10.1039/c5nr04245c

Additional Links
http://xlink.rsc.org/?DOI=C5NR04245C

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