Physical Review X
“Speed-Ups to Isothermality: Enhanced Quantum Thermal Machines through Control of the System-Bath Coupling”
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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 Wdiss decays with the total time τtot of the protocol as Wdiss∝τ−2α−1tot, where each value α>0 can be obtained by a suitable modification of the interaction, whereas α=0 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 α=0 and the Carnot efficiency for α→∞. Analogous enhancements are obtained for the coefficient of performance of refrigerators. We confirm our analytical results with two numerical examples where α=1/2, 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.
Access to the paper: https://journals.aps.org/prx/abstract/10.1103/PhysRevX.10.031015