Nonlinear conductance in molecular devices: molecular length dependence

TL;DR

This study uses ab initio methods to analyze how molecular length affects electronic conductance in gold-molecule-gold junctions, revealing a decrease in conductivity with longer molecules and highlighting the role of orbital delocalization and electrode distance.

Contribution

It provides a detailed theoretical analysis of length-dependent conductance in molecular devices using NEGF and DFT, offering insights into transport mechanisms.

Findings

Conductance decreases as molecular length increases.

Transport properties are influenced by orbital delocalization and electrode separation.

Transmission eigenchannel analysis explains the length dependence of conductance.

Abstract

We theoretically study the electronic transport in the monolayer of dithiolated phenylene vinylene oligomeres coupled to the (111) surfaces of gold electrodes. We use non-equilibrium Green functions (NEGF) and density functional theory(DFT) implemented in the TranSIESTA package to obtain a full ab initio self-consistent description ofthe transport current through the molecular nanostructure with different electrochemical bias potentials. The calculated current-voltage characteristics (IVC) of the systems for the same contact geometry have shown a systematic decrease of the conductivity with the increased length of the molecules. We analyze the results in terms of transmission eigenchannels and find that besides the delocalization of molecular orbitals the distance between gold electrodes also determines the transport properties.