Quantum Carnot thermal machines re-examined: Definition of efficiency and the effects of strong coupling
arXiv:2311.15465 · doi:10.1103/PhysRevE.109.044118
Abstract
Whether the strong coupling to thermal baths can improve the performance of quantum thermal machines remains an open issue under active debate. Here, we revisit quantum thermal machines operating with the quasi-static Carnot cycle and aim to unveil the role of strong coupling in maximum efficiency. Our analysis builds upon definitions of excess work and heat derived from an exact formulation of the first law of thermodynamics for the working substance, which captures the non-Gibbsian thermal equilibrium state that emerges at strong couplings during quasi-static isothermal processes. These excess definitions differ from conventional ones by an energetic cost for maintaining the non-Gibbsian characteristics. With this distinction, we point out that one can introduce two different yet thermodynamically allowed definitions for efficiency of both the heat engine and refrigerator modes. We dub them excess and hybrid definitions which differ in the way of defining the gain for the thermal machines at strong couplings by either just analyzing the energetics of the working substance or instead evaluating the performance from an external system upon which the thermal machine acts, respectively. We analytically demonstrate that the excess definition predicts that the Carnot limit remains the upper bound for both operation modes at strong couplings, whereas the hybrid one reveals that strong coupling can suppress the maximum efficiency rendering the Carnot limit unattainable. These seemingly incompatible predictions thus indicate that it is imperative to first gauge the definition for efficiency before elucidating the exact role of strong coupling, thereby shedding light on the on-going investigation on strong-coupling quantum thermal machines.
arXiv comment9 pages, 1 figure. Comments are highly welcome!
References in corpus (49)
- Quantum Thermodynamic Cycles and quantum heat engines
- A single-atom heat engine
- Fundamental aspects of steady-state conversion of heat to work at the nanoscale
- A nano heat engine beyond the Carnot limit
- Maximal work extraction from quantum systems
- Single ion heat engine with maximum efficiency at maximum power
- Entropy production as correlation between system and reservoir
- Experimental demonstration of quantum effects in the operation of microscopic heat engines
- Experimental characterization of a spin quantum heat engine
- A quantum-dot heat engine operating close to the thermodynamic efficiency limits
- A Micrometer-sized Heat Engine Operating Between Bacterial Reservoirs
- A spin heat engine coupled to a harmonic-oscillator flywheel
- Quantum thermodynamic devices: from theoretical proposals to experimental reality
- Nonequilibrium thermodynamics in the strong coupling and non-Markovian regime based on a reaction coordinate mapping
- {\it Colloquium:} Statistical Mechanics and Thermodynamics at Strong Coupling: Quantum and Classical
- Quantum Measurement Cooling
- Quantum thermal absorption machines: refrigerators, engines and clocks
- Performance of a quantum heat engine at strong reservoir coupling
- Thermodynamics of Micro- and Nano-Systems Driven by Periodic Temperature Variations
- Efficiency of a quantum Otto heat engine operating under a reservoir at effective negative temperatures
- Thermodynamic universality of quantum Carnot engines
- First and Second Law of Quantum Thermodynamics: A Consistent Derivation Based on a Microscopic Definition of Entropy
- Strong coupling corrections in quantum thermodynamics
- Quantum Heat Current under Non-perturbative and Non-Markovian Conditions: Applications to Heat Machines
- Analog of a quantum heat engine using a single-spin qubit
- Quantum Performance of Thermal Machines over Many Cycles
- Local effective dynamics of quantum systems: A generalized approach to work and heat
- Weak and ultrastrong coupling limits of the quantum mean force Gibbs state
- Thermal machines beyond the weak coupling regime
- Spin Quantum Heat Engine Quantified by Quantum Steering
- Enhancement of quantum heat engine by encircling a Liouvillian exceptional point
- Brownian duet: A novel tale of thermodynamic efficiency
- Making statistics work: a quantum engine in the BEC-BCS crossover
- From quantum heat engines to laser cooling: Floquet theory beyond the Born-Markov approximation
- Entropy-Based Formulation of Thermodynamics in Arbitrary Quantum Evolution
- Thermodynamics in Single-Electron Circuits and Superconducting Qubits
- A photonic quantum engine driven by superradiance
- Clausius Inequality for Finite Baths Reveals Universal Efficiency Improvements
- Quantum limit to nonequilibrium heat-engine performance imposed by strong system-reservoir coupling
- Engineering dynamical couplings for quantum thermodynamic tasks
- Non-Markovian effect on quantum Otto engine: -Role of system--reservoir interaction-
- Autonomous implementation of thermodynamic cycles at the nanoscale
- Multitask quantum thermal machines and cooperative effects
- Cyclic quantum engines enhanced by strong bath coupling
- Efficiency of a cyclic quantum heat engine with finite-size baths
- Quantum Otto cycle under strong coupling
- Dynamics of a strongly coupled quantum heat engine -- computing bath observables from the hierarchy of pure states
- Optimal linear cyclic quantum heat engines cannot benefit from strong coupling
- Impossibility of bosonic autonomous entanglement engines in the weak-coupling limit