Coulomb blockade in molecular quantum dots

TL;DR

This paper models sequential tunneling in molecular quantum dots within the Coulomb blockade regime, analyzing how electronic structure and Coulomb effects influence nonlinear transport properties such as conductance and current-voltage characteristics.

Contribution

It introduces a rate-equation approach to describe transport in molecular quantum dots, highlighting the effects of Coulomb blockade on nonlinear conductance and current behavior.

Findings

Current suppression at higher voltages

Charging-induced rectification effect

Temperature and broadening effects on current steps

Abstract

The rate-equation approach is used to describe sequential tunneling through a molecular junction in the Coulomb blockade regime. Such device is composed of molecular quantum dot (with discrete energy levels) coupled with two metallic electrodes via potential barriers. Based on this model, we calculate nonlinear transport characteristics (conductance-voltage and current-voltage dependences) and compare them with the results obtained within a self-consistent field approach. It is shown that the shape of transport characteristics is determined by the combined effect of the electronic structure of molecular quantum dots and by the Coulomb blockade. In particular, the following phenomena are discussed in detail: the suppression of the current at higher voltages, the charging-induced rectification effect, the charging-generated changes of conductance gap, and the temperature-induced as well as broadening-generated smoothing of current steps.