The Experts below are selected from a list of 1095 Experts worldwide ranked by ideXlab platform
Francesco Giazotto - One of the best experts on this subject based on the ideXlab platform.
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Efficient and tunable Aharonov-Bohm quantum heat engine
Physical Review B, 2019Co-Authors: Géraldine Haack, Francesco GiazottoAbstract:We propose a quantum heat engine based on an Aharonov-Bohm interferometer in a two-terminal geometry, and investigate its thermoelectric performances in the linear response regime. Sizeable thermopower (up to $\sim 0.3\,\text{mV}$/K) as well as $ZT$ values largely exceeding unity can be achieved for suitable system parameters and temperature bias across the interferometer leading to thermal efficiency at maximum power approaching $30\%$ of the Carnot Limit. This is close to the optimal efficiency at maximum power achievable for a two-terminal heat engine. Changing either the magnetic flux or a bias voltage through a capacitively-coupled electrode allow to finely tune the quantum heat engine performance. Despite the simplicity of the setup, the high performances of the engine are stable over a wide range of temperatures and length imbalances, promising towards experimental realization.
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Proposal for a phase-coherent thermoelectric transistor
Applied Physics Letters, 2014Co-Authors: Francesco Giazotto, Jason W. A. Robinson, Jagadeesh S. Moodera, F. S. BergeretAbstract:Identifying materials and devices which offer efficient thermoelectric effects at low temperature is a major obstacle for the development of thermal management strategies for low-temperature electronic systems. Superconductors cannot offer a solution since their near perfect electron-hole symmetry leads to a negligible thermoelectric response; however, here we demonstrate theoretically a superconducting thermoelectric transistor which offers unparalleled figures of merit of up to ∼45 and Seebeck coefficients as large as a few mV/K at sub-Kelvin temperatures. The device is also phase-tunable meaning its thermoelectric response for power generation can be precisely controlled with a small magnetic field. Our concept is based on a superconductor-normal metal-superconductor interferometer in which the normal metal weak-link is tunnel coupled to a ferromagnetic insulator and a Zeeman split superconductor. Upon application of an external magnetic flux, the interferometer enables phase-coherent manipulation of thermoelectric properties whilst offering efficiencies which approach the Carnot Limit.
Wei Li - One of the best experts on this subject based on the ideXlab platform.
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photonic refrigeration from time modulated thermal emission
Physical Review Letters, 2020Co-Authors: Siddharth Buddhiraju, Wei LiAbstract:We develop theoretical and computational formalisms to describe thermal radiation from temporally modulated systems. We show that such a modulation results in a photon-based active cooling mechanism. This mechanism has a high thermodynamic performance that can approach the Carnot Limit. Our work points to exciting new avenues in active, time-modulated control of thermal emission for cooling and energy harvesting applications.
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photonic refrigeration from time modulated thermal emission
arXiv: Optics, 2019Co-Authors: Siddharth Buddhiraju, Wei LiAbstract:Active photonic cooling is of significant importance to realize robust, compact, vibration-free, all-solid-state refrigeration. Currently proposed photonic cooling approaches are based on luminescence and impose stringent requirements on luminescence efficiency. We propose a new photonic cooling mechanism arising from temporal modulation of thermal emission. We show that this mechanism has a high thermodynamic performance that can approach the Carnot Limit and yet does not rely on luminescence. Further, our work opens exciting new avenues in active, time-modulated control of thermal emission for cooling and energy harvesting applications.
Emre Togan - One of the best experts on this subject based on the ideXlab platform.
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Squeezed Thermal Reservoirs as a Resource for a Nanomechanical Engine beyond the Carnot Limit
Physical Review X, 2017Co-Authors: Jan Klaers, Stefan Faelt, Atac Imamoglu, Emre ToganAbstract:A tiny engine can surpass the Carnot Limit of efficiency when researchers engineer the thermal properties of the environment.
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squeezed thermal reservoirs as a resource for a nano mechanical engine beyond the Carnot Limit
arXiv: Mesoscale and Nanoscale Physics, 2017Co-Authors: Jan Klaers, Stefan Faelt, Atac Imamoglu, Emre ToganAbstract: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 is 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, non-equilibrium 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 nano-beam 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 non-equilibrium thermodynamics at small scales and provide a new perspective on the design of efficient, highly miniaturized engines.
Siddharth Buddhiraju - One of the best experts on this subject based on the ideXlab platform.
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Active Photonic Cooling using Time-Modulated Thermal Emission
2020Co-Authors: Siddharth Buddhiraju, Shanhui FanAbstract:We present a coupled-mode theory and a computational formalism to describe thermal radiation from time-modulated systems. We show that such modulation results in an active cooling mechanism with high thermodynamic performance approaching the Carnot Limit.
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photonic refrigeration from time modulated thermal emission
Physical Review Letters, 2020Co-Authors: Siddharth Buddhiraju, Wei LiAbstract:We develop theoretical and computational formalisms to describe thermal radiation from temporally modulated systems. We show that such a modulation results in a photon-based active cooling mechanism. This mechanism has a high thermodynamic performance that can approach the Carnot Limit. Our work points to exciting new avenues in active, time-modulated control of thermal emission for cooling and energy harvesting applications.
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photonic refrigeration from time modulated thermal emission
arXiv: Optics, 2019Co-Authors: Siddharth Buddhiraju, Wei LiAbstract:Active photonic cooling is of significant importance to realize robust, compact, vibration-free, all-solid-state refrigeration. Currently proposed photonic cooling approaches are based on luminescence and impose stringent requirements on luminescence efficiency. We propose a new photonic cooling mechanism arising from temporal modulation of thermal emission. We show that this mechanism has a high thermodynamic performance that can approach the Carnot Limit and yet does not rely on luminescence. Further, our work opens exciting new avenues in active, time-modulated control of thermal emission for cooling and energy harvesting applications.
Heiner Linke - One of the best experts on this subject based on the ideXlab platform.
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Reversible electron-hole separation in a hot carrier solar cell
New Journal of Physics, 2015Co-Authors: Steven Limpert, Stephen Bremner, Heiner LinkeAbstract:Hot-carrier solar cells are envisioned to utilize energy filtering to extract power from photogenerated electron-hole pairs before they thermalize with the lattice, and thus potentially offer higher power conversion efficiency compared to conventional, single absorber solar cells. The efficiency of hot-carrier solar cells can be expected to strongly depend on the details of the energy filtering process, a relationship which to date has not been satisfactorily explored. Here, we establish the conditions under which electron-hole separation in hot-carrier solar cells can occur reversibly, that is, at maximum energy conversion efficiency. We thus focus our analysis on the internal operation of the hot-carrier solar cell itself, and in this work do not consider the photon-mediated coupling to the Sun. After deriving an expression for the voltage of a hot-carrier solar cell valid under conditions of both reversible and irreversible electrical operation, we identify separate contributions to the voltage from the thermoelectric effect and the photovoltaic effect. We find that, under specific conditions, the energy conversion efficiency of a hot-carrier solar cell can exceed the Carnot Limit set by the intradevice temperature gradient alone, due to the additional contribution of the quasi-Fermi level splitting in the absorber. We also establish that the open-circuit voltage of a hot-carrier solar cell is not Limited by the band gap of the absorber, due to the additional thermoelectric contribution to the voltage. Additionally, we find that a hot-carrier solar cell can be operated in reverse as a thermally driven solid-state light emitter. Our results help explore the fundamental Limitations of hot-carrier solar cells, and provide a first step towards providing experimentalists with a guide to the optimal configuration of devices. (Less)
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High‐Performance Thermoelectrics Based on Heterostructure Nanowires
AIP Conference Proceedings, 2007Co-Authors: Heiner Linke, T. E. Humphrey, M. F. O'dwyerAbstract:There is great scientific, economic and environmental interest in the development of thermoelectric materials capable of direct thermal‐to‐electric energy conversion with high efficiency. We predict that in materials with a fine‐tuned electronic density of states, electrons can be placed in energy‐specific equilibrium, and the efficiency of thermoelectric power generation can approach the fundamental Carnot Limit. To prove this concept experimentally, we propose to use heterostructured, group III/V nanowires with a built‐in double‐barrier resonance, which will allow electron energy filtering via 1D‐0D‐1D resonant tunneling. We present a concept study on the expected thermoelectric performance of realistic nanowires, and discuss the potential for applications of nanowires in future thermoelectrics.
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Concept study for a high-efficiency nanowire based thermoelectric
Nanotechnology, 2006Co-Authors: M. F. O'dwyer, T. E. Humphrey, Heiner LinkeAbstract:Materials capable of highly efficient, direct thermal-to-electric energy conversion would have substantial economic potential. Theory predicts that thermoelectric efficiencies approaching the Carnot Limit can be achieved at low temperatures in one-dimensional conductors that contain an energy filter such as a double-barrier resonant tunnelling structure. The recent advances in growth techniques suggest that such devices can now be realized in heterostructured, semiconductor nanowires. Here we propose specific structural parameters for InAs/InP nanowires that may allow the experimental observation of near-Carnot efficient thermoelectric energy conversion in a single nanowire at low temperature.
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Power generation with nanowire resonant tunneling thermoelectrics
2006 25th International Conference on Thermoelectrics, 2006Co-Authors: M. F. O'dwyer, Heiner Linke, E. Hoffmann, T. E. Humphrey, Roger A Lewis, Chao ZhangAbstract:Nanowires have been predicted to yield significantly improved thermoelectric figures of merit. Here we describe the electron energy spectrum of a resonant tunneling heterostructure nanowire in detail and show how it may be used to realize energy filtering for thermoelectric electronic efficiencies approaching the Carnot Limit. A proof-of-principle experiment is described that seeks to demonstrate such idealized electronic properties.
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Energy-specific equilibrium in nanowires for efficient thermoelectric power generation
MRS Proceedings, 2005Co-Authors: Heiner Linke, T. E. Humphrey, M. F. O'dwyerAbstract:There is great scientific, economic and environmental interest in the development of thermoelectric materials capable of direct thermal-to-electric energy conversion with high efficiency. Recent theory predicts that in materials with a fine-tuned electronic density of states, electrons can be placed in energy-specific equilibrium, and the efficiency of thermoelectric power generation can approach the fundamental Carnot Limit. Here we review the relevant theory of energy-specific equilibrium. We describe a concept for a proof-of principle demonstration of near-Carnot efficient power conversion involving a single, ballistic nanowire at low temperatures, and we discuss the potential for room-temperature applications in diffusive materials.