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Power, Efficiency and Fluctuations in a Quantum Point Contact as Steady-State Thermoelectric Heat Engine
Sara Kheradsoud1, Nastaran Dashti2, Maciej Misiorny2
1Physics Department and NanoLund, Lund University, S-221 00 Lund, Sweden.
Entropy (Basel, Switzerland)
|December 3, 2020
Summary
This study explores the trade-offs in quantum heat engines, specifically quantum point contacts (QPCs). Researchers found that QPCs can achieve high power and efficiency with low fluctuations, demonstrating the utility of thermodynamic uncertainty relations (TURs).
Area of Science:
- Quantum Thermodynamics
- Mesoscopic Physics
- Energy Conversion
Background:
- The operation of heat engines involves a trade-off between power output, efficiency, and operational fluctuations.
- Thermodynamic Uncertainty Relations (TURs) provide theoretical bounds on these trade-offs, attracting recent research interest.
Purpose of the Study:
- To theoretically investigate the performance of a quantum point contact (QPC) as a steady-state thermoelectric heat engine.
- To analyze the trade-off between power, efficiency, and fluctuations using TURs for a QPC with an energy-dependent transmission function.
- To explore both linear and non-linear operating regimes and arbitrary smoothness of the QPC transmission probability.
Main Methods:
- Theoretical analysis of a quantum point contact (QPC) model.
- Review and extension of previous work on power production and efficiency in QPC heat engines.
- Analysis of power fluctuations and the bounds imposed by TURs on power, efficiency, and fluctuations.
- Consideration of varying degrees of smoothness in the QPC transmission probability.
Main Results:
- For a wide range of parameters, the QPC heat engine achieves near-maximum theoretical power output.
- The engine operates at efficiencies exceeding half of the Carnot efficiency while maintaining relatively small fluctuations.
- A stronger TUR, formulated using the thermoelectric figure of merit, is derived for non-zero power production in the linear regime.
- This derived bound remains valid in a broad parameter regime beyond linear response.
Conclusions:
- Quantum point contacts can effectively function as heat engines, balancing power, efficiency, and fluctuations.
- The findings validate and extend the application of thermodynamic uncertainty relations in quantum systems.
- The study provides a concrete example of optimizing heat engine performance within fundamental thermodynamic constraints.
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