Electron-vibration effects on the thermoelectric efficiency of molecular junctions

Abstract

The thermoelectric properties of a molecular junction model, appropriate for large molecules such as fullerenes, are studied within a non-equilibrium adiabatic approach in the linear regime at room temperature. A self-consistent calculation is implemented for electron and phonon thermal conductance showing that both increase with the inclusion of the electron-vibration coupling. Moreover, we show that the deviations from the Wiedemann-Franz law are progressively reduced upon increasing the interaction between electronic and vibrational degrees of freedom. Consequently, the junction thermoelectric efficiency is substantially reduced by the electron-vibration coupling. Even so, for realistic parameters values, the thermoelectric figure of merit can still have peaks of the order of unity. Finally, in the off-resonant electronic regime, our results are compared with those of an approach which is exact for low molecular electron densities. We give evidence that in this case additional quantum effects, not included in the first part of this work, do not affect significantly the junction thermoelectric properties in any temperature regime.

arXiv comment15 pages, 11 figures, 2 Appendices

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• Influence of phonon-assisted tunneling on the linear thermoelectric transport through molecular quantum dots
• Extractable work in quantum electromechanics
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• Ground state features and spectral properties of large polaron liquids from low to high charge densities
• On the role of local many-body interactions on the thermoelectric properties of fullerene junctions
• Thermoelectric effects in tunneling of spin-polarized electrons in a molecular transistor