Evolution of Molecular Binding in Mechanically controlled Break-Junctions


Evolution of Molecular Binding in Mechanically controlled Break-Junctions

Lokamani, M.; Günther, F.; Kelling, J.; Gemming, S.

Mechanically controllable break junctions (MCBJs) are devices, in which the electrical properties of single molecules can be investigated with extreme precision using atomically structured metallic electrodes. The current-voltage (IV) characteristics in such junctions are considerably affected by the binding positions of the anchoring groups on the tip-facets and the configuration of the molecule. Hence, characterizing the electronic transport properties during a single tip-tip opening provides interesting insights in to the tip-molecule interaction.
In this contribution/talk, we present a novel, high-throughput approach to reproduce the time evolution of the electronic transport characteristics. For this, we performed transport calculations using the self-consistent charge scheme of the density-functional-based tight binding (SCC-DFTB)[1] approach and the Green’s function formalism. In particular, we evaluated the energy level E0 and the coupling Γ of the dominating transport channel using the single level model[2]. In contrast to standard approaches, we consider not just one molecule orientation but many thermodynamically relevant configurations. The obtained parameters were averaged using statistical weights obtained from Metropolis simulation considering up to 80.000 different configurations for selected tip-tip distances. The dependence of the averaged quantities with respect to the tip-tip separation reveals characteristic features also observed in experiments for similar molecular systems.
Our approach allows us to relate these features to binding-site and molecule-curvature effects and therefore provides a better interpretation of the experimental results.

1. M. Elstner, D. Porezag, G. Jungnickel, J. Elsner, M. Haugk, T. Frauenheim, S. Suhai, and G. Seifert, Self-consistent-charge density-functional tight-binding method for simulations of complex materials properties, Phys. Rev. B 58, 7260 (1998)
2. Cuevas, J. C.; Scheer, E. In Molecular Electronics: An Introduction to Theory and Experiment; Reed, M., Ed.; World Scientific Series in Nanoscience and Nanotechnology, Vol. 1; World Scientific: Singapore,Hackensack, NJ, 201

Keywords: mechanically controlled break junctions; high-throughput simulations

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    Seminar Theorie, Modellierung, Simulation https://www.tu-chemnitz.de/physik/TQPS/TheorieSeminar.html, 15.09.2021, Chemnitz, Germany

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Publ.-Id: 34079