Many-body theory of electronic transport in single-molecule heterojunctions

TL;DR

This paper develops a comprehensive many-body theoretical framework for electronic transport in molecular junctions, accurately capturing Coulomb interactions and quantum coherence effects, and applies it to analyze thermoelectric and conductance properties of a benzenedithiol-gold junction.

Contribution

It introduces a unified many-body approach based on nonequilibrium Green's functions that treats Coulomb interactions and quantum effects on equal footing, with exact and self-consistent evaluations.

Findings

Reproduces Coulomb blockade and coherent transport features simultaneously.

Calculates thermoelectric power and conductance spectrum of a molecular junction.

Accurately describes electronic excitations up to 10 eV.

Abstract

A many-body theory of molecular junction transport based on nonequilibrium Green's functions is developed, which treats coherent quantum effects and Coulomb interactions on an equal footing. The central quantity of the many-body theory is the Coulomb self-energy matrix $\Sigma_{\rm C}$ of the junction. $\Sigma_{\rm C}$ is evaluated exactly in the sequential tunneling limit, and the correction due to finite tunneling width is evaluated self-consistently using a conserving approximation based on diagrammatic perturbation theory on the Keldysh contour. Our approach reproduces the key features of both the Coulomb blockade and coherent transport regimes simultaneously in a single unified transport theory. As a first application of our theory, we have calculated the thermoelectric power and differential conductance spectrum of a benzenedithiol-gold junction using a semi-empirical $\pi$-electron Hamiltonian that accurately describes the full spectrum of electronic excitations of the molecule up to 8--10eV.