Observation of Quantum Interference in Molecular Charge Transport

TL;DR

This paper provides experimental evidence of quantum interference effects in molecular charge transport at room temperature and demonstrates control of this interference through chemical modifications, paving the way for molecular quantum devices.

Contribution

It reports the first direct observation of destructive quantum interference in molecular junctions at room temperature and shows how chemical modifications can tune this interference.

Findings

Evidence of destructive quantum interference at 300 K

Control of interference via chemical modifications

Potential for molecular quantum device development

Abstract

As the dimensions of a conductor approach the nano-scale, quantum effects will begin to dominate its behavior. This entails the exciting possibility of controlling the conductance of a device by direct manipulation of the electron wave function. Such control has been most clearly demonstrated in mesoscopic semiconductor structures at low temperatures. Indeed, the Aharanov-Bohm effect, conductance quantization and universal conductance fluctuations are direct manifestations of the electron wave nature. However, an extension of this concept to more practical emperatures has not been achieved so far. As molecules are nano-scale objects with typical energy level spacings (~eV) much larger than the thermal energy at 300 K (~25 meV), they are natural candidates to enable such a break-through. Fascinating phenomena including giant magnetoresistance, Kondo effects and conductance switching, have previously been demonstrated at the molecular level. Here, we report direct evidence for destructive quantum interference in charge transport through two-terminal molecular junctions at room temperature. Furthermore, we show that the degree of interference can be controlled by simple chemical modifications of the molecule. Not only does this provide the experimental demonstration of a new phenomenon in quantum charge transport, it also opens the road for a new type of molecular devices based on chemical or electrostatic control of quantum interference.