Interplay between electron-electron and electron-vibration interactions on the thermoelectric properties of molecular junctions

TL;DR

This paper investigates how electron-electron and electron-vibration interactions influence the thermoelectric properties of molecular junctions near room temperature, revealing their combined effects on thermal conductance and thermoelectric efficiency.

Contribution

It introduces a generalized nonequilibrium adiabatic approach that includes large Coulomb repulsion for studying thermoelectric properties in complex molecules.

Findings

Electron-vibration interactions increase thermal conductance.

Strong electron-electron interactions affect phonon thermal conductance.

Thermoelectric figure of merit peaks around unity for realistic parameters.

Abstract

The linear thermoelectric properties of molecular junctions are theoretically studied close to room temperature within a model including electron-electron and electron-vibration interactions on the molecule. A nonequilibrium adiabatic approach is generalized to include large Coulomb repulsion through a self-consistent procedure and applied to the investigation of large molecules, such as fullerenes, within the Coulomb blockade regime. The focus is on the phonon thermal conductance which is quite sensitive to the effects of strong electron-electron interactions within the intermediate electron-vibration coupling regime. The electron-vibration interaction enhances the phonon and electron thermal conductance, and it reduces the charge conductance and the thermopower inducing a decrease of the thermoelectric figure of merit. For realistic values of junction parameters, the peak values of the thermoelectric figure of merit are still of the order of unity since the phonon thermal conductance can be even smaller than the electron counterpart.