Molecular Heat Engines: Quantum Coherence Effects

Feng Chen,Yi Gao,Michael Galperin

doi:10.3390/e19090472

Abstract

Recent developments in nanoscale experimental techniques made it possible to utilize single molecule junctions as devices for electronics and energy transfer with quantum coherence playing an important role in their thermoelectric characteristics. Theoretical studies on the efficiency of nanoscale devices usually employ rate (Pauli) equations, which do not account for quantum coherence. Therefore, the question whether quantum coherence could improve the efficiency of a molecular device cannot be fully addressed within such considerations. Here, we employ a nonequilibrium Green function approach to study the effects of quantum coherence and dephasing on the thermoelectric performance of molecular heat engines. Within a generic bichromophoric donor-bridge-acceptor junction model, we show that quantum coherence may increase efficiency compared to quasi-classical (rate equation) predictions and that pure dephasing and dissipation destroy this effect.

Highlights

Single molecules are used as building blocks of molecular devices for electronics, biosensors, nanoscale motors, controllable chemical reactivity and energy transfer [1,2,3]
The small size of these nanodevices gives rise to new physical phenomena that are not present at the macroscopic level, and which promise to improve the performance of energy conversion
We study thermoelectric properties of a bi-chromophoric DBA junction model driven by solar radiation of the donor complex

Summary

Introduction

Single molecules are used as building blocks of molecular devices for electronics, biosensors, nanoscale motors, controllable chemical reactivity and energy transfer [1,2,3]. Bridge-induced coupling between the LUMOs (levels 2 and 3 in Figure 1) is the cause of intra-molecular quantum coherence. D†m (dm ) and ĉ†k (ĉk ) create (annihilate) the electron at the molecular level m or contact state k, respectively.

Results

Conclusion