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Optimal power and efficiency of single quantum dot heat engines : Theory and experiment

Josefsson, Martin LU ; Svilans, Artis LU ; Linke, Heiner LU and Leijnse, Martin LU (2019) In Physical Review B 99(23).
Abstract

Quantum dots (QDs) can serve as near perfect energy filters and are therefore of significant interest for the study of thermoelectric energy conversion close to thermodynamic efficiency limits. Indeed, recent experiments in [Nat. Nano. 13, 920 (2018)1748-338710.1038/s41565-018-0200-5] realized a QD heat engine with performance near these limits and in excellent agreement with theoretical predictions. However, these experiments also highlighted a need for more theory to help guide and understand the practical optimization of QD heat engines, in particular regarding the role of tunnel couplings on the performance at maximum power and efficiency for QDs that couple seemingly weakly to electronic reservoirs. Furthermore, these experiments... (More)

Quantum dots (QDs) can serve as near perfect energy filters and are therefore of significant interest for the study of thermoelectric energy conversion close to thermodynamic efficiency limits. Indeed, recent experiments in [Nat. Nano. 13, 920 (2018)1748-338710.1038/s41565-018-0200-5] realized a QD heat engine with performance near these limits and in excellent agreement with theoretical predictions. However, these experiments also highlighted a need for more theory to help guide and understand the practical optimization of QD heat engines, in particular regarding the role of tunnel couplings on the performance at maximum power and efficiency for QDs that couple seemingly weakly to electronic reservoirs. Furthermore, these experiments also highlighted the critical role of the external load when optimizing the performance of a QD heat engine in practice. To provide further insight into the operation of these engines we use the Anderson impurity model together with a Master equation approach to perform power and efficiency calculations up to co-tunneling order. This is combined with additional thermoelectric experiments on a QD embedded in a nanowire where the power is measured using two methods. We use the measurements to present an experimental procedure for efficiently finding the external load RP which should be connected to the engine to optimize power output. Our theoretical estimates of RP show good agreement with the experimental results, and we show that second order tunneling processes and nonlinear effects have little impact close to maximum power, allowing us to derive a simple analytic expression for RP. In contrast, we find that the electron contribution to the thermoelectric efficiency is significantly reduced by second order tunneling processes, even for rather weak tunnel couplings.

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author
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organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Physical Review B
volume
99
issue
23
article number
235432
publisher
American Physical Society
external identifiers
  • scopus:85068595826
ISSN
2469-9950
DOI
10.1103/PhysRevB.99.235432
language
English
LU publication?
yes
id
fccbeafe-4b8f-494d-b7db-afb33e07eecd
date added to LUP
2019-07-17 08:42:16
date last changed
2020-12-29 01:22:49
@article{fccbeafe-4b8f-494d-b7db-afb33e07eecd,
  abstract     = {<p>Quantum dots (QDs) can serve as near perfect energy filters and are therefore of significant interest for the study of thermoelectric energy conversion close to thermodynamic efficiency limits. Indeed, recent experiments in [Nat. Nano. 13, 920 (2018)1748-338710.1038/s41565-018-0200-5] realized a QD heat engine with performance near these limits and in excellent agreement with theoretical predictions. However, these experiments also highlighted a need for more theory to help guide and understand the practical optimization of QD heat engines, in particular regarding the role of tunnel couplings on the performance at maximum power and efficiency for QDs that couple seemingly weakly to electronic reservoirs. Furthermore, these experiments also highlighted the critical role of the external load when optimizing the performance of a QD heat engine in practice. To provide further insight into the operation of these engines we use the Anderson impurity model together with a Master equation approach to perform power and efficiency calculations up to co-tunneling order. This is combined with additional thermoelectric experiments on a QD embedded in a nanowire where the power is measured using two methods. We use the measurements to present an experimental procedure for efficiently finding the external load RP which should be connected to the engine to optimize power output. Our theoretical estimates of RP show good agreement with the experimental results, and we show that second order tunneling processes and nonlinear effects have little impact close to maximum power, allowing us to derive a simple analytic expression for RP. In contrast, we find that the electron contribution to the thermoelectric efficiency is significantly reduced by second order tunneling processes, even for rather weak tunnel couplings.</p>},
  author       = {Josefsson, Martin and Svilans, Artis and Linke, Heiner and Leijnse, Martin},
  issn         = {2469-9950},
  language     = {eng},
  month        = {06},
  number       = {23},
  publisher    = {American Physical Society},
  series       = {Physical Review B},
  title        = {Optimal power and efficiency of single quantum dot heat engines : Theory and experiment},
  url          = {http://dx.doi.org/10.1103/PhysRevB.99.235432},
  doi          = {10.1103/PhysRevB.99.235432},
  volume       = {99},
  year         = {2019},
}