Thermoelectric transport with electron-phonon coupling and electron-electron interaction in molecular junctions

TL;DR

This study uses nonequilibrium Green's functions to analyze thermoelectric transport in molecular junctions, revealing how electron-phonon and electron-electron interactions influence thermoelectric efficiency and suggesting potential for high-performance thermoelectric devices.

Contribution

It introduces a non-perturbative method to handle interactions and demonstrates how these interactions can be tuned to optimize thermoelectric performance in molecular junctions.

Findings

ZT resonances occur near electronic conductance peaks at low temperatures

Increasing electron-phonon coupling and Coulomb repulsion enhances ZT

Optimal thermoelectric performance arises when electron-phonon and electron-electron interactions compete

Abstract

Within the framework of nonequilibrium Green's functions, we investigate the thermoelectric transport in a single molecular junction with electron-phonon and electron-electron interactions. By transforming into a displaced phonon basis, we are able to deal with these interactions non-perturbatively. Then, by invoking the weak tunneling limit, we are able to calculate the thermoelectricity. Results show that at low temperatures, resonances of the thermoelectric figure of merit ZT occur around the sides of resonances of electronic conductance but drops dramatically to zero at exactly these resonant points. We find ZT can be enhanced by increasing electron-phonon coupling and Coulomb repulsion, and an optimal enhancement is obtained when these two interactions are competing. Our results indicate a great potential for single-molecular-junctions as good thermoelectric devices over a wide range of temperatures.