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Work extremum principle: structure and function of quantum heat engines
Armen E Allahverdyan1, Ramandeep S Johal, Guenter Mahler
1Yerevan Physics Institute, Alikhanian Brothers Street 2, Yerevan 375036, Armenia.
Summary
This study explores quantum heat engines, finding that maximizing work extraction at finite power yields efficiencies between Curzon-Ahlborn and Carnot limits. Zero power extraction allows even small engines to reach Carnot efficiency.
Area of Science:
- Quantum thermodynamics
- Statistical mechanics
- Condensed matter physics
Background:
- Quantum heat engines offer a framework for understanding energy conversion at the quantum level.
- Investigating engine performance beyond the near-equilibrium regime is crucial for practical applications.
Purpose of the Study:
- To analyze the performance of quantum heat engines operating under various constraints.
- To determine the efficiency and power output of quantum heat engines beyond equilibrium.
Main Methods:
- Considering a class of quantum heat engines with two subsystems interacting with a work-source and two thermal baths.
- Maximizing extracted work under constraints of finite power and zero power.
- Analyzing engine dynamics, temperature, and efficiency bounds.
Main Results:
- Engine dynamics at finite power are described by well-defined temperatures and satisfy the local second law.
- Efficiency is bounded by the Curzon-Ahlborn and Carnot values.
- Maximum power efficiency exceeds the Curzon-Ahlborn value.
- Zero power maximization allows small engines to achieve Carnot efficiency.
Conclusions:
- Quantum heat engines can operate efficiently beyond equilibrium conditions.
- Finite power operation leads to a trade-off between efficiency and power.
- Carnot efficiency is attainable for quantum heat engines under specific conditions (zero power).
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