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Universality and the thermoelectric transport properties of a double quantum dot system: Seeking for conditions that improve the thermoelectric efficiency
by Ronald Santiago Cortes-Santamaria , J. A. Landazabal-Rodríguez, Jereson Silva-Valencia , Edwin Ramos , M. S. Figueira and Roberto Franco Peñaloza.
Submission summary
| Authors (as registered SciPost users): | Roberto Franco Peñaloza |
| Submission information | |
|---|---|
| Preprint Link: | scipost_202312_00043v1 (pdf) |
| Date submitted: | 2023-12-24 03:32 |
| Submitted by: | Franco Peñaloza, Roberto |
| Submitted to: | SciPost Physics Core |
| Ontological classification | |
|---|---|
| Academic field: | Physics |
| Specialties: |
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| Approaches: | Theoretical, Computational |
Abstract
Employing universal relations for the Onsager coefficients in the linear regime at the symmetric point of the single impurity Anderson model, we calculate the conditions under which the quantum scattering phase shift should satisfy to produce the asymptotic Carnot’s limit for the thermoelectric efficiency. We show that a single quantum dot connected by metallic leads at the Kondo regime cannot achieve the best thermoelectric efficiency. We study a serial double quantum dot system, with the quantum dots immersed in ballistic conduction channels. Each QD exhibits a strong but finite local electronic correlation U. We show that maintaining one dot in the electron-hole symmetric point and allowing charge fluctuations in the other QD makes it possible to drive the system to the maximum thermoelectric efficiency. We also show that the bound states in the continuum (BICs) and quasi-BICs associated with the quantum scattering interference process drive the DQD to the maximum thermoelectric efficiency. We identify two types of quasi-BICs that occur at low and high temperatures: The first is associated with single Fano resonances, and the last is with several Fano processes. We also discussed possible temperature values and conditions that could be linked with the experimental realization of the results.
Current status:
Reports on this Submission
Strengths
The work addresses the importance of designing new nanostructured systems presenting high thermoelectrical efficiencies. The treatment for calculation of such efficiencies is somehow novel as long as it relates the figure of merit to the scattering phase shifts. The authors identify the main mechanisms to have a large efficiency and show that the proposed system, a double quantum dot, is able to reach extraordinary ZT values even in the high temperature regime.
Weaknesses
The employed numerical technique to solve the Hamiltonian is discussed in the manuscript however it is not compared with other techniques.
The thermoelectrical analysis is done solely for the linear regime although a calculation for the efficiency at maximum power is presented in the Apendix.
Only situations where one of the quantum dots is in the symmetry situation is presented and for me it is not clear why the authors discard a more general scenario.
Report
The authors present an interesting work that nicely addresses the importance of having nanosystems working as highly efficient thermoelectrical devices. For such purposes, the authors indicate that quantum dots could perform such a job. Indeed, QDs are known to be good thermoelectrical systems due to their strong dependence on energy for transmission. With this aim the authors analyze two situations, the first corresponds to a single QD in which the thermoelectrical efficiency cannot achieve the maximal value. The way to show this result is through the scattering amplitude. Since this system is not a good candidate the authors introduce another QD connected by tunneling to the other QD via a continuous channel. It is natural to have interference phenomena. Under certain conditions the transmission displays peaks due to the formation of localized states and due to this phenomenon the thermoelectrical power enhances a lot. However, here I have some questions
1. The Kondo effect is needed since it introduces an energy scale denoted by the Kondo temperature that makes these localized states to have a very narrow width and this is responsible for having the large ZT. If this is right, the authors should clarify better why Kondo resonances are needed in the interference phenomenon to lead to such high ZT values.
2. It is not clear to me why the authors neglect the RKKY interaction that can appear in this system
3. The continuum states connecting the two dots could lead, for some system parameters the emergence of a non-Fermi liquid behavior. Can the authors comment on this?
4. It is needed to have one of the quantum dots in the symmetric case? What it can happen if the two dots are gated?
5. Could the authors discuss the main differences in relation of the thermoelectrical properties this work has in comparison with other works dealing with double dots. For instance in DQDs in parallel Fano factor can also be present.
Requested changes
All are mentioned in my report, they are about further explanations of the work
Author: Roberto Franco Peñaloza on 2024-04-30 [id 4457]
(in reply to Report 1 on 2024-03-23)I wish you a nice day.
I am answering point by point the referee´s questions in the attached file: Answer_referee_Scipost_290424.pdf
Our new version of the paper is ready for evaluation, this is going to be at the arxiv soon.
Thanks a lot, best regards.
Roberto Franco Peñaloza
Attachment:
Answer_referee_Scipost_290424.pdf