Electron–Vibration Interaction in Multichannel Single-Molecule Junctions

Abstract

The effect of electron-vibration interaction in atomic-scale junctions with a single conduction channel was widely investigated both theoretically and experimentally. However, the more general case of junctions with several conduction channels has received very little attention. Here we study electron-vibration interaction in multichannel molecular junctions, formed by introduction of either benzene or carbon dioxide between platinum electrodes. By combining shot noise and differential conductance measurements, we analyze the effect of vibration activation on conductance in view of the distribution of conduction channels. Based on the shift of vibration energy while the junction is stretched, we identify vibration modes with transverse and longitudinal symmetry. The detection of different vibration modes is ascribed to efficient vibration coupling to different conduction channels according to symmetry considerations. While most of our observations can be explained in view of the theoretical models for a single conduction channel, the appearance of conductance enhancement, induced by electron-vibration interaction, at high conductance values indicates either unexpected high electron-vibration coupling or interchannel scattering.

Origin of the Anomalous Electronic Shot Noise in Atomic-Scale Junctions

“…Noise in electronic signals is typically undesired, yet it can be a source of information on the conducting system by exposing effects concealed in the time-averaged electric current. [1][2][3] Shot noise measurements at the mesoscale and nanoscale 4,5 reveal the fractional charge of quasiparticles in many-body systems, 6 contributions of different conduction channels to the electronic transport, 7-13 the crossover from ballistic to diffusive transport, 14 the valence orbital structure at the contact, 15,16 activation of vibrations in molecular conducting junctions, 10,[17][18][19] and the onset of spin-polarized transport. 20,21 Focusing on the white noise (flat power spectrum) component, we recall on the different noise sources: 1,2 The thermal motion of charge carriers in electronic conductors is responsible for the Johnson-Nyquist noise, 22,23 which is proportional to the temperature and the linear response electrical conductance.…”

Full counting statistics of vibrationally assisted electronic conduction: Transport and fluctuations of thermoelectric efficiency

“…Coupled electron-vibration processes were probed in singlemolecule junctions applying inelastic electron tunneling spectroscopy [4][5][6] and Raman spectroscopy tools [7][8][9] , displaying frequency shifts and mode heating in response to electron conduction. Noise characteristics of the charge current can further expose the nature of the vibrational modes contributing to electron dynamics 5,10,11 . Theoretical and computational methodologies dedicated to the effects of electron-phonon interactions on transport in nano-conductors were reviewed in Refs.…”

Alternative types of molecule-decorated atomic chains in Au–CO–Au single-molecule junctions

“…However, to determine the details of the formation of molecular junctions further analysis is required [ 1 – 28 ]. Important information can be obtained by further techniques such as noise [ 3 – 4 ], thermopower [ 5 – 6 ] or inelastic spectroscopy [ 11 – 14 ] measurements. However, it has been recently realized that just by the advanced statistical analysis of the measured conductance traces essential information can be obtained.…”