Large Conductance Variations in a Mechanosensitive Single-Molecule Junction
Davide Stefani, Kevin J. Weiland, Maxim Skripnik, Chunwei Hsu, Mickael L. Perrin, Marcel Mayor, Fabian Pauly, and Herre S. J. van der Zant;
Nano Lett., 2018, 18 (9), pp 5981–5988
Abstract
Particularly interesting are destructive quantum interference effects leading to a strong suppression of electron transmission at specific energies, which make them an ideal feature for applications in, e.g., thermo-(15) or voltage-dependent switching.(16) Their manipulation has been reported by external means including solid-state(17) or electrochemical gating,(18) humidity,(19)and the sliding of π-stacked molecules relative to each other.(14) Deliberate manipulation of the latter, however, remains elusive as it requires strict temperature conditions and is based on intermolecular interactions. In particular, the intermolecular character requires the coincidental presence of two molecules inside the junction. For this reason, approaches that intramolecularly imitate intermolecular π-stacking move into the focus of interest. Along these lines, the [2.2]paracyclophane (PC) compound is highly appealing.(20) First described by Farthing et al. in 1949, it consists of two stacked benzene rings that are mechanically stabilized by two nonconjugated linkers.(21) Integrated as central unit of an oligo-phenylene-ethynylene (OPE) rod with terminal binding groups to gold electrodes (Figure 1), we show here that using a mechanically controlled break junction (MCBJ) the π-stacking (and, therefore, the conductance) can be modulated by exerting a mechanical shear force to it. Simulations based on density functional theory (DFT) reveal a sensitive correlation between electrode displacement and molecular conductance, which is interpreted in terms of quantum interference effects between the frontier orbitals.
Authors
Davide Stefani, Kevin J. Weiland, Maxim Skripnik, Chunwei Hsu, Mickael L. Perrin, Marcel Mayor, Fabian Pauly, and Herre S. J. van der Zant