Molecular junctions in the Coulomb blockade regime: rectification and nesting

TL;DR

This paper models quantum transport in weakly coupled molecular junctions within the Coulomb blockade regime, revealing rectification and nesting effects through a novel theoretical approach combining nonequilibrium Green functions and master equations.

Contribution

It introduces a new theoretical framework that combines nonequilibrium Green functions with master equations to analyze Coulomb blockade effects in molecular junctions.

Findings

Observation of rectification in I-V characteristics

Identification of nesting in stability diagrams

Development of a modular theoretical approach

Abstract

Quantum transport through single molecules is very sensitive to the strength of the molecule-electrode contact. Here, we investigate the behavior of a model molecular junction weakly coupled to external electrodes in the case where charging effects do play an important role (Coulomb blockade regime). As a minimal model we consider a molecular junction with two spatially separated donor and acceptor sites. Depending on their mutual coupling to the electrodes, the resulting transport observables show well defined features such as rectification effects in the I-V characteristics and nesting of the stability diagrams. To be able to accomplish these results, we have developed a theory which allows to explore the charging regime via the nonequilibrium Green function formalism parallel to the widely used master equation technique. Our results, beyond their experimental relevance, offer a transparent framework for the systematic and modular inclusion of a richer physical phenomenology.