Effect of nonadiabatic electronic-vibrational interactions on the transport properties of single-molecule junctions

TL;DR

This paper investigates how nonadiabatic electronic-vibrational interactions affect electron transport in single-molecule junctions, revealing significant impacts depending on electronic level configurations using a perturbative Green's function approach.

Contribution

It introduces a detailed analysis of nonadiabatic electronic-vibrational coupling effects on transport, distinguishing between different electronic level regimes in molecular junctions.

Findings

Nonadiabatic interactions significantly influence transport properties.

Differences between nonadiabatic and adiabatic couplings are elucidated.

Transport behavior varies with electronic level separation.

Abstract

The interaction between electronic and vibrational degrees of freedom in single-molecule junctions may result from the dependence of the electronic energies or the electronic states of the molecular bridge on the nuclear displacement. The latter mechanism leads to a direct coupling between different electronic states and is referred to as nonadiabatic electronic-vibrational coupling. Employing a perturbative nonequilibrium Green's function approach, we study the influence of nonadiabatic electronic-vibrational coupling in model molecular junctions. Thereby we distinguish between systems with well separated and quasi-degenerate electronic levels. The results show that the nonadiabatic electronic-vibrational interaction can have a significant influence on the transport properties. The underlying mechanisms, in particular the difference between nonadiabatic and adiabatic electronic-vibrational coupling, are analyzed in some detail.