Abstract
Isothermal transformations are minimally dissipative but slow processes, as the system needs to remain close to thermal equilibrium along the protocol. Here, we show that smoothly modifying the system-bath interaction can significantly speed up such transformations. In particular, we construct protocols where the overall dissipation decays with the total time of the protocol as , where each value can be obtained by a suitable modification of the interaction, whereas corresponds to a standard isothermal process where the system-bath interaction remains constant. Considering heat engines based on such speed-ups, we show that the corresponding efficiency at maximum power interpolates between the Curzon-Ahlborn efficiency for and the Carnot efficiency for . Analogous enhancements are obtained for the coefficient of performance of refrigerators. We confirm our analytical results with two numerical examples where , namely the time-dependent Caldeira-Leggett and resonant-level models, with strong system-environment correlations taken fully into account. We highlight the possibility of implementing our proposed speed-ups with ultracold atomic impurities and mesoscopic electronic devices.
8 More- Received 27 January 2020
- Revised 22 April 2020
- Accepted 14 May 2020
DOI:https://doi.org/10.1103/PhysRevX.10.031015
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Open access publication funded by the Max Planck Society.
Published by the American Physical Society
Physics Subject Headings (PhySH)
Popular Summary
Isothermal processes, in which a system changes while the temperature stays constant, play a central role in classical thermodynamics, and they are still subject to intense research efforts in the context of quantum thermodynamics. Recent developments have focused on optimizing such processes with the goal of designing more efficient and powerful thermal machines. Here, we demonstrate how full control over the coupling strength between a system and its heat bath allows for the design of transformations that are faster and more efficient.
In particular, we develop protocols that gently modify the system-bath interaction in order to keep the overall dissipation constant while decreasing the total time of the thermodynamic protocol. This enables us to construct faster finite-time Carnot engines, whose efficiency at maximum power is shown to be higher than the standard Curzon-Ahlborn efficiency—a theoretical upper limit on the efficiency of an irreversible heat engine.
These results open the door to a broader class of thermodynamic protocols with theoretical interest and also potentially to practical implementation in modern experiments.