Nanoscale Heat Engine Beyond the Carnot Limit

Roßnagel, Johannes; Abah, Obinna; Schmidt-Kaler, F.; Singer, Kilian; Lutz, Eric

doi:10.1103/physrevlett.112.030602

Cited by 626 publications

(650 citation statements)

References 60 publications

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“…Such a study helps us to understand the special behavior of thermodynamic quantities like work, heat, and efficiency in the quantum regime due to the presence non-classical features such as entanglement, quantum superposition, squeezing, etc. [19][20][21]. The quantum heat devices can show interesting atypical behaviors such as exceeding Carnot limit [19,21] when they act as heat engines.…”

Section: Introductionmentioning

confidence: 99%

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Implications of Coupling in Quantum Thermodynamic Machines

Thomas

Banik

Ghosh

2017

Entropy

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Abstract:We study coupled quantum systems as the working media of thermodynamic machines. Under a suitable phase-space transformation, the coupled systems can be expressed as a composition of independent subsystems. We find that for the coupled systems, the figures of merit, that is the efficiency for engine and the coefficient of performance for refrigerator, are bounded (both from above and from below) by the corresponding figures of merit of the independent subsystems. We also show that the optimum work extractable from a coupled system is upper bounded by the optimum work obtained from the uncoupled system, thereby showing that the quantum correlations do not help in optimal work extraction. Further, we study two explicit examples; coupled spin-1/2 systems and coupled quantum oscillators with analogous interactions. Interestingly, for particular kind of interactions, the efficiency of the coupled oscillators outperforms that of the coupled spin-1/2 systems when they work as heat engines. However, for the same interaction, the coefficient of performance behaves in a reverse manner, while the systems work as the refrigerator. Thus, the same coupling can cause opposite effects in the figures of merit of heat engine and refrigerator.

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Section: Introductionmentioning

confidence: 99%

“…[19][20][21]. The quantum heat devices can show interesting atypical behaviors such as exceeding Carnot limit [19,21] when they act as heat engines. However, these apparent behaviors are found to be compatible with the second law of thermodynamics when all the preparation costs are considered [22].…”

Section: Introductionmentioning

confidence: 99%

Implications of Coupling in Quantum Thermodynamic Machines

Thomas

Banik

Ghosh

2017

Entropy

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“…In a first line of experiments, we construct an Otto cycle between a hot squeezed thermal reservoir with effective temperature T h ¼ 10 000 K and squeezing factor r ¼ 0.4 and a cold purely thermal bath at T c ¼ 9500 K under maximum power condition [19]. The four strokes include an adiabatic compression, isochoric heat addition, adiabatic expansion, and isochoric heat rejection.…”

Section: Otto Cycle With Squeezed Thermal Reservoirsmentioning

confidence: 99%

“…In the future, the exploitation of novel sources of work could have a large impact on the design of efficient and powerful engines at the microscale and nanoscale. By employing nonequilibrium reservoirs, it is expected that the efficiency of work generation can surpass standard thermodynamic bounds, as has been theoretically suggested for quantum coherent [12], quantum correlated [13,14], quantum-measurement-induced [15][16][17], and squeezed thermal reservoirs [18][19][20][21][22][23]. The realization of such engines not only extends our knowledge of finite-size, nonequilibrium, and quantum effects in thermodynamics, but could also lead to important applications in nanotechnology and in the life sciences [24].…”

Section: Introductionmentioning

confidence: 98%

“…This results in a state with reduced thermal fluctuations in one quadrature (e.g., momentum) and enhanced thermal fluctuations in the other quadrature (e.g., position) compared to the expected level of fluctuations at the given temperature. In the context of heat engines, a theoretical work by Roßnagel et al [19] suggests that squeezed thermal states may be used as an additional resource to overcome the standard Carnot limit [31]. Because of the nonequilibrium nature of squeezed thermal reservoirs, this result does not violate the second law of thermodynamics.…”

Section: Introductionmentioning

confidence: 99%

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Squeezed Environment Boosts Engine Performance

Millen

2017

Physics

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The efficient conversion of thermal energy to mechanical work by a heat engine is an ongoing technological challenge. Since the pioneering work of Carnot, it has been known that the efficiency of heat engines is bounded by a fundamental upper limit-the Carnot limit. Theoretical studies suggest that heat engines may be operated beyond the Carnot limit by exploiting stationary, nonequilibrium reservoirs that are characterized by a temperature as well as further parameters. In a proof-of-principle experiment, we demonstrate that the efficiency of a nanobeam heat engine coupled to squeezed thermal noise is not bounded by the standard Carnot limit. Remarkably, we also show that it is possible to design a cyclic process that allows for extraction of mechanical work from a single squeezed thermal reservoir. Our results demonstrate a qualitatively new regime of nonequilibrium thermodynamics at small scales and provide a new perspective on the design of efficient, highly miniaturized engines.

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High Performance of Carbon Nanotube Refrigerators

Cantuário

Fonseca

2019

Annalen der Physik

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Vapor‐compression dominates the market for refrigeration devices due to low cost and relatively high efficiency. However, the most efficient vapor refrigerants are either ozone depleting or global warming substances. Solid‐state cooling is a young field of research with promising results toward the development of new, efficient, and environment friendly technology for a new generation of refrigeration devices. One of these methods is based on the so‐called elastocaloric effect (ECE), which consists of a temperature variation of a system in response to the application of adiabatic stresses. Although most of the literature describes the study of ECE solid‐state cooling based on materials undergoing phase‐transitions, a study recently predicted that carbon nanotubes (CNTs) present ECE as large as 30 K for 3% of strain. This motivates research toward the development of nanorefrigerators. As nobody knows the efficiency of such an ECE‐based CNT nanorefrigerator, here, significantly high coefficient of performance values of 4.1 and 6.5, and extracted heat per weight as large as 40 J g−1 are reported for a zigzag CNT nanorefrigerator operating in an Otto‐like thermodynamic cycle. This efficiency is shown to overcome that of some other ECE materials.

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Nanoscale Heat Engine Beyond the Carnot Limit

Cited by 626 publications

References 60 publications

Implications of Coupling in Quantum Thermodynamic Machines

Implications of Coupling in Quantum Thermodynamic Machines

Squeezed Environment Boosts Engine Performance

High Performance of Carbon Nanotube Refrigerators

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