Multimode vibrational effects in single molecule conductance: A nonequilibrium Green's function approach

TL;DR

This paper explores how multiple vibrational modes influence electron transport in single molecule junctions using an advanced nonequilibrium Green's function approach, revealing significant effects on conductance and mode coupling.

Contribution

It extends a Green's function method to include multiple vibrational modes, providing new insights into vibrational effects on molecular conductance.

Findings

Multiple vibrational modes significantly affect conductance.

Electronically induced vibrational mode coupling observed.

Current-induced vibrational excitations characterized.

Abstract

The role of multimode vibrational dynamics in electron transport through single molecule junctions is investigated. The study is based on a generic model, which describes charge transport through a single molecule that is attached to metal leads. To address vibrationally-coupled electron transport, we employ a nonequilibrium Green's function approach that extends a method recently proposed by Galperin et al. [Phys. Rev. B 73, 045314 (2006)] to multiple vibrational modes. The methodology is applied to two systems: a generic model with two vibrational degrees of freedom and benzenedibutanethiolate covalently bound to gold electrodes. The results show that the coupling to multiple vibrational modes can have a significant effect on the conductance of a molecular junction. In particular, we demonstrate the effect of electronically induced coupling between different vibrational modes and study nonequilibrium vibrational effects by calculating the current-induced excitation of vibrational modes.