Mechanically Controlled Quantum Interference in Individual {\pi}-stacked Dimers

TL;DR

This study demonstrates that quantum interference in {\pi}-stacked molecular dimers can be mechanically toggled, enabling control over conductance with high precision, which is promising for molecular electronic device design.

Contribution

It introduces a method to mechanically control destructive quantum interference in single-molecule junctions using combined ab-initio calculations and advanced statistical analysis.

Findings

Quantum interference can be turned ON or OFF mechanically.

Conductance varies over several orders of magnitude.

Interference patterns are linked to intermolecular electronic couplings.

Abstract

Recent observations of destructive quantum interference in single-molecule junctions confirm the role played by quantum effects in the electronic conductance properties of molecular systems. We show here that the destructive interference can be turned ON or OFF within the same molecular system by mechanically controlling its conformation. Using a combination of ab-initio calculations and single-molecule conductance measurements, we demonstrate the existence of a quasi-periodic destructive quantum interference pattern along the breaking traces of {\pi}-{\pi} stacked molecular dimers. The detection of these interferences, which are due to opposite signs of the intermolecular electronic couplings, was only made possible by a combination of wavelet transform and higher-order statistical analysis of single-breaking traces. The results demonstrate that it is possible to control the molecular conductance over a few orders of magnitudes and with a sub-angstrom resolution by exploiting the subtle structure-property relationship of {\pi}-{\pi} stack dimers. These large conductance changes may be beneficial for the design of single-molecule electronic components that exploit the intrinsic quantum effects occurring at the molecular scale.