Thermoelectric transport through strongly correlated quantum-dot based hybrid devices: A non-equilibrium many body Green’s function approach

Abstract: We shall present our analytical study of a quantum dot (QD) based thermoelectric particle-exchange heat engine (N-QD-N) for both finite and infinite on-dot Coulomb correlation. Employing Keldysh's nonequilibrium Green's function formalism for different decoupling schemes in the equation of motion, we have analyzed the thermoelectric properties within the non-linear transport regime. As the simplest mean-field approximation is insufficient for analyzing thermoelectric properties in the Coulomb blockade regime, one needs to employ a higher-order approximation to study strongly correlated QD-based heat engines. Therefore, we initially used the Hubbard-Ⅰ approximation to study the quantum dot level position (gate voltage), thermal gradient, and on-dot Coulomb interaction dependence of the thermoelectric properties. To provide further insight into a more practical QD heat engine operation, we used an approach beyond Hubbard-Ⅰ with strong on-site Coulomb repulsion, i.e., U→∞. Within this infinite-U limit, we examine the role of the symmetric dot-reservoir tunneling and external serial load resistance in optimizing the performance of the strongly correlated quantum dot heat engine. Our infinite-U results show a good quantitative agreement with recent experimental data and real time diagrammatic theory. Thus Green's function EOM technique which is a computationally inexpensive and straightforward analytical method gives reliable results in the Coulomb blockade regime. The present analysis can be extended to examine the optimal performance of other realistic low dimensional heat engines based on multiple quantum dots and multiple reservoirs within the strong Coulomb blockade regime.

We shall also briefly highlight our recent results for a hybrid QD system in which a Bardeen-Cooper-Schrieffer (BCS) superconductor replaces the normal metallic drain reservoir. The results show that this hybrid superconductor-quantum dot system (N-QD-S) exhibits a finite thermal response, thus making it a promising candidate for low-temperature thermal applications such as quantum dot-based power generators, refrigerators, quantum heat valves, and rectifiers.

References

1. Sachin Verma and Ajay, (Manuscript under review) (2022) arXiv preprint: arXiv:2208.06686v1

2. Sachin Verma and Ajay, Journal of Physics: Condensed Matter 34, 155601 (2022), DOI: 10.1088/1361-648X/ac4ced

3. M. Josefsson, A. Svilans, A. M. Burke, E. A. Hoffmann, S. Fahlvik, C. Thelander, M. Leijnse, and H. Linke, Nature Nanotech 13, 920–924, (2018), M. Josefsson, A. Svilans, H. Linke, and M. Leijnse, Phys. Rev. B 99, 235432, (2019)

4. S. M. Tabatabaei, D. Sánchez, A.L. Yeyati, and R. Sánchez, Phys. Rev. B 106, 115419, (2022)

Computer scienceMathematicsPhysics

Audience: researchers in the topic

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QHS Lecture Series on Superconducting Phenomena and Electronics

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