Universal features in the efficiency at maximal work of hot quantum Otto engines

Uzdin, Raam; Kosloff, Ronnie

doi:10.1209/0295-5075/108/40001

Cited by 62 publications

(55 citation statements)

References 20 publications

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“…The lower and upper bound coincide in the linear response regime where η − = η + = η CA = η S S = η C /2 17 . We note that features of the efficiency at maximum power similar to those above discussed for low-dissipation engines are also found in a quantum model where the working substance is a single multilevel particle which undergoes an Otto cycle [469].…”

Section: Low-dissipation Enginessupporting

confidence: 71%

Fundamental aspects of steady-state conversion of heat to work at the nanoscale

et al. 2017

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In recent years, the study of heat to work conversion has been re-invigorated by nanotechnology. Steady-state devices do this conversion without any macroscopic moving parts, through steady-state flows of microscopic particles such as electrons, photons, phonons, etc. This review aims to introduce some of the theories used to describe these steady-state flows in a variety of mesoscopic or nanoscale systems. These theories are introduced in the context of idealized machines which convert heat into electrical power (heat-engines) or convert electrical power into a heat flow (refrigerators). In this sense, the machines could be categorized as thermoelectrics, although this should be understood to include photovoltaics when the heat source is the sun. As quantum mechanics is important for most such machines, they fall into the field of quantum thermodynamics. In many cases, the machines we consider have few degrees of freedom, however the reservoirs of heat and work that they interact with are assumed to be macroscopic. This review discusses different theories which can take into account different aspects of mesoscopic and nanoscale physics, such as coherent quantum transport, magnetic-field induced effects (including topological ones such as the quantum Hall effect), and single electron charging effects. It discusses the efficiency of thermoelectric conversion, and the thermoelectric figure of merit. More specifically, the theories presented are (i) linear response theory with or without magnetic fields, (ii) Landauer scattering theory in the linear response regime and far from equilibrium, (iii) Green-Kubo formula for strongly interacting systems within the linear response regime, (iv) rate equation analysis for small quantum machines with or without interaction effects, (v) stochastic thermodynamic for fluctuating small systems. In all cases, we place particular emphasis on the fundamental questions about the bounds on ideal machines. Can magnetic-fields change the bounds on power or efficiency? What is the relationship between quantum theories of transport and the laws of thermodynamics? Does quantum mechanics place fundamental bounds on heat to work conversion which are absent in the thermodynamics of classical systems?

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Section: Low-dissipation Enginessupporting

confidence: 71%

Fundamental aspects of steady-state conversion of heat to work at the nanoscale

et al. 2017

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“…We note that the aforementioned formula for the efficiency at maximum power is sensitive to the constraints on the system, and changing the constraints changes this formula. For instance, see [164,165] for results generalising the Curzon-Ahlborn efficiency to stochastic thermodynamics and to quantum systems with other constraints. The rest of this section is a brief description of how engines are designed in the quantum regime.…”

Section: Quantum Thermal Machinesmentioning

confidence: 99%

Quantum thermodynamics

Vinjanampathy¹,

Anders²

2016

Contemporary Physics

904

806

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Quantum thermodynamics is an emerging research field aiming to extend standard thermodynamics and non-equilibrium statistical physics to ensembles of sizes well below the thermodynamic limit, in non-equilibrium situations, and with the full inclusion of quantum effects. Fueled by experimental advances and the potential of future nanoscale applications this research effort is pursued by scientists with different backgrounds, including statistical physics, many-body theory, mesoscopic physics and quantum information theory, who bring various tools and methods to the field. A multitude of theoretical questions are being addressed ranging from issues of thermalisation of quantum systems and various definitions of "work", to the efficiency and power of quantum engines. This overview provides a perspective on a selection of these current trends accessible to postgraduate students and researchers alike.

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“…Here we take the high-temperature limit (x α → 0) where, e.g., symmetric quantum heat engines are known to operate at the Yvon-Novikov-Curzon-Ahlborn efficiency [26,27] and different models of absorption refrigerators achieve their maximal performance [28,29]. We thus approximate I (x h ,x c ) around x α = 0, retaining only the first nonzero term in its Taylor expansion…”

Section: Optimal Cop For High Temperaturesmentioning

confidence: 99%

Optimal performance of endoreversible quantum refrigerators

et al. 2014

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The derivation of general performance benchmarks is important in the design of highly optimized heat engines and refrigerators. To obtain them, one may model phenomenologically the leading sources of irreversibility ending up with results that are model independent, but limited in scope. Alternatively, one can take a simple physical system realizing a thermodynamic cycle and assess its optimal operation from a complete microscopic description. We follow this approach in order to derive the coefficient of performance at maximum cooling rate for any endoreversible quantum refrigerator. At striking variance with the universality of the optimal efficiency of heat engines, we find that the cooling performance at maximum power is crucially determined by the details of the specific system-bath interaction mechanism. A closed analytical benchmark is found for endoreversible refrigerators weakly coupled to unstructured bosonic heat baths: an ubiquitous case study in quantum thermodynamics.

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Universal features in the efficiency at maximal work of hot quantum Otto engines

Cited by 62 publications

References 20 publications

Fundamental aspects of steady-state conversion of heat to work at the nanoscale

Fundamental aspects of steady-state conversion of heat to work at the nanoscale

Quantum thermodynamics

Optimal performance of endoreversible quantum refrigerators

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