Electrode effects on the observability of destructive quantum interference in single-molecule junctions

Abstract

Destructive quantum interference (QI) has been a source of interest as a new paradigm for molecular electronics as the electronic conductance is widely dependent on the occurrence or absence of...

Enhancing the sensitivity and selectivity of pyrene-based sensors for detection of small gaseous molecules via destructive quantum interference

“…5, that the bias-driven electronic current is generally higher for junctions with a para-substituted pyrene. This is a consequence of the QI properties of the pyrene core, 51,52 which exhibits constructive (CQI) or destructive QI (DQI) in the para-and meta-configuration, respectively. While one could expect CQI to be beneficial for sensing applications because of the higher electric signal, it is worth noting that junctions exhibiting DQI are found to be more responsive to changes in the chemical environment (see Fig.…”

“…6(b) for para-substituted pyrene, where energies are given with respect to the Fermi level E F = 0. There are three key features in the electronic transmission, that we shall discuss in detail: i) all transmission functions in the meta configuration exhibit an antiresonance within the HOMO-LUMO gap as hallmark of DQI, which is absent in the para configuration, 52 ii) the transmission functions of the junctions with H 2 O or NH 3 adsorbates are very similar before (grey dashed lines) and after (color solid line) the adsorption, although the position of the frontier MOs and the antiresonances with respect to the Fermi level are different; iii) the presence of NO 2 instead results in a sizable shift of the Fermi level (∼ 430 meV) and gives rise to an asymmetric resonance at the Fermi level.…”

“…In the junctions exhibiting DQI, the electronic transmission function is strongly suppressed in an energy window around an antiresonance. It is known that the energy DQI of the antiresonance depends on a cancellation in the electronic Green's function involving all MOs, 40,45,46,52 and therefore, the relative position of the antiresonance with respect to frontier MO resonances and the Fermi level is not necessarily the same in junctions with and without the adsorbate, since the latter can couple differently with each MO. In particular, in Fig.…”

“…50 In this study, we focus on a pyrene molecule, which, as a polycyclic aromatic hydrocarbon, can be considered a minimal graphene-like structure. 44,51,52 The disubstituted pyrene core bridges Au electrodes in a singlemolecule junction setup. For the purpose of gas sensing, we investigate the adsorption of NO 2 , H 2 O, and NH 3 on the pyrene core.…”