Nonadiabatic vibronic effects in single-molecule junctions: A theoretical study using the hierarchical equations of motion approach

TL;DR

This paper investigates how nonadiabatic electronic-vibrational interactions affect charge transport in molecular junctions, revealing significant impacts and phenomena like negative differential conductance using a numerically exact hierarchical equations of motion approach.

Contribution

It provides a detailed theoretical analysis of nonadiabatic vibronic effects in molecular electronics, employing the hierarchical equations of motion method for the first time in this context.

Findings

Nonadiabatic coupling significantly alters transport characteristics.

Negative differential conductance observed due to nonadiabatic effects.

Mechanisms of transport modification are elucidated.

Abstract

The interaction between electronic and vibrational degrees of freedom is an important mechanism in nonequilibrium charge transport through molecular nanojunctions. While adiabatic polaron-type coupling has been studied in great detail, new transport phenomena arise for nonadiabatic coupling scenarios corresponding to a breakdown of the Born-Oppenheimer approximation. Employing the numerically exact hierarchical equations of motion approach, we analyze the effect of nonadiabatic electronic-vibrational coupling on electron transport in molecular junctions considering a series of models with increasing complexity. The results reveal a significant influence of nonadiabatic coupling on the transport characteristics and a variety of interesting effects, including negative differential conductance. The underlying mechanisms are analyzed in detail.