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

TL;DR

This study uses first-principles calculations to analyze how electrode materials and anchor groups influence the detection of destructive quantum interference in single-molecule junctions, providing insights for experimental interpretation.

Contribution

It demonstrates how electrode and anchor chemistry affect quantum interference observability, offering a detailed structure-function relationship analysis beyond simple models.

Findings

Graphene electrodes introduce features that can mask or mimic QI effects.

Fermi level alignment is crucial for observing destructive QI.

Electrode topology influences low-bias transmission features.

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 destructive QI effects. In order to interpret experimentally observed transmission features, it is necessary to understand the effects of all components of the junction on electron transport. We perform non-equilibrium Green's function calculations within the framework of density functional theory to assess the structure-function relationship of transport through pyrene molecular junctions with distinct QI properties. The chemical nature of the anchor groups and the electrodes controls the Fermi level alignment, which determines the observability of destructive QI. A thorough analysis allows to disentangle the transmission features arising from the molecule and the electrodes. Interestingly, graphene electrodes introduce features in the low-bias regime, which can either mask or be misinterpreted as QI effects, while instead originating from the topological properties of the edges. Thus, this first principles analysis provides clear indications to guide the interpretation of experimental studies, which cannot be obtained from simple H\"uckel model calculations.