Evolution of Single-Level-Model parameters in the Mechanically controllable Break Junctions


Evolution of Single-Level-Model parameters in the Mechanically controllable Break Junctions

Kilibarda, F.; Günther, F.; Kelling, J.; Strobel, A.; Zahn, P.; Juckeland, G.; Kurt, G.; Elke, S.; Gemming, S.; Erbe, A.

The electrical properties of single molecules can be investigated using atomically sharp metallic electrodes in mechanically controllable break junctions (MCBJs). The current-voltage (IV) characteristics of single molecules in such junctions are affected by the binding positions of the end groups on the tip-facets and tip-tip separation. In this poster, we present MCBJ experiments on N,N’-Bis(5-ethynylbenzenethiol-salicylidene)ethylenediamine (Salen). We discuss the evolution of the single level model (SLM) parameters namely, a) the energetic level (epsilon) of the dominant conducting channel and b) the coupling (Gamma) of the dominant conducting channel to the metallic electrodes. The SLM-parameters were evaluated for IV-curves recorded during opening measurements and fitted to the single level model. We explain the recurring peak-like features/protusions in the experimentally measured evolution of Gamma with increasing tip-tip separation, which we relate not only to the deformation of the molecule but also to the sliding of the anchor group above the electrode surface. We propose a novel, high-throughput approach to model the evolution of the SLM-parameters and perform transport calculations using the self-consistent charge scheme of the density-functional-based tight binding (SCC-DFTB) approach and the Green’s function formalism. Thereby, we consider many thermodynamically relevant configurations and assess the evolution of SLM-parameters using the SLM-curve fitting of the zero-bias transmission. The SLM-parameters are averaged using statistical weights obtained from a Metropolis simulation considering up to 200 000 configurations for selected tip-tip separations. The behavior of the averaged quantities with respect to the tip-tip separation reflects the experimentally observed evolution of the SLM-parameters astonishingly well.

Keywords: high-throughput approach; Mechanically controllable break junctions; single level model; Metropolis simulation; Evolution of Single-Level-Model parameters

  • Open Access Logo Poster (Online presentation)
    YOUNG RESEARCHER’S WORKSHOP ON MACHINE LEARNING FOR MATERIALS, 09.-13.05.2022, Trieste, Italy

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Permalink: https://www.hzdr.de/publications/Publ-34896
Publ.-Id: 34896