Modeling transport through single-molecule junctions

TL;DR

This paper uses NEGF combined with EHT and charging models to analyze electrical conduction in single-molecule junctions, highlighting charging effects on transport properties and conductance behavior.

Contribution

It introduces a model that accurately predicts current and transport characteristics in single-molecule junctions considering charging effects.

Findings

Charging reduces conductance gap

Charging induces rectification effects

Negative second derivative of current with respect to voltage observed

Abstract

Non-equilibrium Green's functions (NEGF) formalism combined with extended Huckel (EHT) and charging model are used to study electrical conduction through single-molecule junctions. Analyzed molecular complex is composed of asymmetric 1,4-Bis((2'-para-mercaptophenyl)-ethinyl)-2-acetyl-amino-5-nitro-benzene molecule symmetrically coupled to two gold electrodes [Reichert et al., Phys. Rev. Lett. Vol.88 (2002), pp. 176804]. Owing to this model, the accurate values of the current flowing through such junction can be obtained by utilizing basic fundamentals and coherently deriving model parameters. Furthermore, the influence of the charging effect on the transport characteristics is emphasized. In particular, charging-induced reduction of conductance gap, charging-induced rectification effect and charging-generated negative value of the second derivative of the current with respect to voltage are observed and examined for molecular complex.