Resonant vibrations, peak broadening and noise in single molecule contacts: beyond the resonant tunnelling picture

TL;DR

This study investigates the electronic and vibrational properties of single-molecule junctions at low temperatures, revealing how fluctuations and noise influence conductance peaks beyond simple resonant tunneling models.

Contribution

It provides new insights into the nature of conductance peaks and noise phenomena in single-molecule contacts, highlighting the role of instabilities and fluctuations.

Findings

Broadening of conductance peaks due to vibronic effects

Detection of noise anomalies at charge transport onset

Evidence of field-induced instabilities in molecular junctions

Abstract

We carry out experiments on single-molecule junctions at low temperatures, using the mechanically controlled break junction technique. Analyzing the results received with more than ten different molecules the nature of the first peak in the differential conductance spectra is elucidated. We observe an electronic transition with a vibronic fine structure, which is most frequently smeared out and forms a broad peak. In the usual parameter range we find strong indications that additionally fluctuations become active even at low temperatures. We conclude that the electrical field feeds instabilities, which are triggered by the onset of current. This is underscored by noise measurements that show strong anomalies at the onset of charge transport.