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Power, Efficiency and Fluctuations in a Quantum Point Contact as Steady-State Thermoelectric Heat Engine. ENTROPY 2019; 21:e21080777. [PMID: 33267490 PMCID: PMC7515306 DOI: 10.3390/e21080777] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/11/2019] [Revised: 07/03/2019] [Accepted: 07/29/2019] [Indexed: 11/17/2022]
Abstract
The trade-off between large power output, high efficiency and small fluctuations in the operation of heat engines has recently received interest in the context of thermodynamic uncertainty relations (TURs). Here we provide a concrete illustration of this trade-off by theoretically investigating the operation of a quantum point contact (QPC) with an energy-dependent transmission function as a steady-state thermoelectric heat engine. As a starting point, we review and extend previous analysis of the power production and efficiency. Thereafter the power fluctuations and the bound jointly imposed on the power, efficiency, and fluctuations by the TURs are analyzed as additional performance quantifiers. We allow for arbitrary smoothness of the transmission probability of the QPC, which exhibits a close to step-like dependence in energy, and consider both the linear and the non-linear regime of operation. It is found that for a broad range of parameters, the power production reaches nearly its theoretical maximum value, with efficiencies more than half of the Carnot efficiency and at the same time with rather small fluctuations. Moreover, we show that by demanding a non-zero power production, in the linear regime a stronger TUR can be formulated in terms of the thermoelectric figure of merit. Interestingly, this bound holds also in a wide parameter regime beyond linear response for our QPC device.
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Zhou Y, Zheng X. Generating pure spin current with spin-dependent Seebeck effect in ferromagnetic zigzag graphene nanoribbons. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:315301. [PMID: 31022711 DOI: 10.1088/1361-648x/ab1cae] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Pure spin current is of great importance in spintronics and may be achieved by spin dependent Seebeck effect (SDSE) in magnetic systems. Zigzag-edged graphene nanoribbons (ZGNRs) are very well-known 2D magnetic nanostructures. However, perfect and pristine ZGNRs either in the anti-ferromagnetic ground state or in the ferromagnetic (FM) state are not capable of producing pure spin current by SDSE at low temperature. In this work, by density functional theory calculations, we propose a scheme for generating pure spin current using SDSE in FM-ZGNRs by introducing antidots. Specifically, by creating a hexagonal antidot with either armchair edges or zigzag edges in the scattering region, we can get finite Seebeck thermopower for both spin channels with opposite signs, leading to the opposite flow directions of the two spin channels. The mechanism is well explained by the cooperation of the varying localization features of states around the Fermi level and the antidot induced scattering potential. By slightly tuning the chemical potential, pure spin current can be achieved. The size and edge shape effects have also been systematically studied. The findings indicate a novel scheme for thermally generating pure spin current in zigzag graphene nanoribbons and may find important application in graphene based spintronics.
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Affiliation(s)
- Yanhong Zhou
- College of Science, East China Jiao Tong University, Nanchang, Jiangxi 330013, People's Republic of China
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Tang S. Extracting the Energy Sensitivity of Charge Carrier Transport and Scattering. Sci Rep 2018; 8:10597. [PMID: 30006531 PMCID: PMC6045660 DOI: 10.1038/s41598-018-28288-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2017] [Accepted: 06/15/2018] [Indexed: 11/09/2022] Open
Abstract
It is a challenge to extract the energy sensitivity of charge carriers' transport and scattering from experimental data, although a theoretical estimation in which the existing scattering mechanism(s) are preliminarily assumed can be easily done. To tackle this problem, we have developed a method to experimentally determine the energy sensitivities, which can then serve as an important statistical measurement to further understand the collective behaviors of multi-carrier transport systems. This method is validated using a graphene system at different temperatures. Further, we demonstrate the application of this method to other two-dimensional (2D) materials as a guide for future experimental work on the optimization of materials performance for electronic components, Peltier coolers, thermoelectricity generators, thermocouples, thermopiles, electrical converters and other conductivity and/or Seebeck-effect-related sensors.
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Affiliation(s)
- Shuang Tang
- College of Engineering, State University of New York, Polytechnic Institute, Albany, New York, 12203, USA.
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Aly AH, El-Gawaad NSA. Thermal Conductance and Seebeck Effect in Mesoscopic Systems. INTERNATIONAL JOURNAL OF THERMOPHYSICS 2015; 36:2845-2853. [DOI: 10.1007/s10765-015-1974-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/02/2023]
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Zou X, Chen X, Huang H, Xu Y, Duan W. Enhanced thermoelectric figure of merit in thin GaAs nanowires. NANOSCALE 2015; 7:8776-8781. [PMID: 25905892 DOI: 10.1039/c5nr01892g] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Combining density functional theory and the nonequilibrium Green's function method, we investigate the thermoelectric properties of thin GaAs nanowires (NWs). After identifying the most stable structures for GaAs NWs, either in wurtzite (wz) or zinc blende (zb) stacking, we present a systematic analysis on the thermoelectric properties of these NWs and their dependence on stacking type (wz or zb), size of NWs, and temperature. Although bulk GaAs is a well-known poor thermoelectric material, the thermoelectric figure of merit, ZT, is significantly enhanced in thin GaAs NWs. Typically, the room temperature ZT of a 1.1 nm-diameter GaAs NW reaches as high as 1.34, exhibiting more than 100-fold improvement over the bulk counterpart, which is attributed to both the reduced thermal conduction and enhanced power factor in thin NWs. Adopting their unique electronic characteristics, further enhancement is possible through surface engineering, for example, the introduction of surface roughness or dopants.
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Affiliation(s)
- Xiaolong Zou
- Department of Materials Science and nanoEngineering, Rice University, Houston, Texas 77005, USA.
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Meair J, Jacquod P. Scattering theory of nonlinear thermoelectricity in quantum coherent conductors. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2013; 25:082201. [PMID: 23343784 DOI: 10.1088/0953-8984/25/8/082201] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We construct a scattering theory of weakly nonlinear thermoelectric transport through sub-micron scale conductors. The theory incorporates the leading nonlinear contributions in temperature and voltage biases to the charge and heat currents. Because of the finite capacitances of sub-micron scale conducting circuits, fundamental conservation laws such as gauge invariance and current conservation require special care to be preserved. We do this by extending the approach of Christen and Büttiker (1996 Europhys. Lett. 35 523) to coupled charge and heat transport. In this way we write relations connecting nonlinear transport coefficients in a manner similar to Mott's relation between the linear thermopower and the linear conductance. We derive sum rules that nonlinear transport coefficients must satisfy to preserve gauge invariance and current conservation. We illustrate our theory by calculating the efficiency of heat engines and the coefficient of performance of thermoelectric refrigerators based on quantum point contacts and resonant tunneling barriers. We identify, in particular, rectification effects that increase device performance.
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Affiliation(s)
- Jonathan Meair
- Physics Department, University of Arizona, Tucson, AZ 85721, USA
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Zheng X, Zheng W, Wei Y, Zeng Z, Wang J. Thermoelectric transport properties in atomic scale conductors. J Chem Phys 2004; 121:8537-41. [PMID: 15511178 DOI: 10.1063/1.1803544] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The thermoelectric transport properties in atomic scale conductors consisting of a Si atom connected by two electrodes are investigated. It is found that both the electrical current and the heat current have two contributions, one from the voltage and the other from the temperature gradient. The quantities such as the Seebeck thermopower and the thermal conductance that characterize the thermoelectric transport properties of the tunnel atomic junction are studied quantitatively with a first-principles technique within the framework of Landauer-Buttiker formalism in the linear response regime. A finite thermopower only exists in a very narrow range where the energy derivative of the transmission function is nonzero. The thermopower anomaly is observed in the tunneling regime in this device but this does not violate the thermodynamic law with respect to the heat current.
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Affiliation(s)
- Xiaohong Zheng
- Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031, People's Republic of China
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Lin MF, Chuu DS, Shung KW. Thermal conductance and the Peltier coefficient of carbon nanotubes. PHYSICAL REVIEW. B, CONDENSED MATTER 1996; 53:11186-11192. [PMID: 9982693 DOI: 10.1103/physrevb.53.11186] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Rokni M, Levinson Y. Joule heat in point contacts. PHYSICAL REVIEW. B, CONDENSED MATTER 1995; 52:1882-1889. [PMID: 9981256 DOI: 10.1103/physrevb.52.1882] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Guttman GD, Ben-Jacob E, Bergman DJ. Thermopower of mesoscopic and disordered systems. PHYSICAL REVIEW. B, CONDENSED MATTER 1995; 51:17758-17766. [PMID: 9978809 DOI: 10.1103/physrevb.51.17758] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Taboryski R, Kristensen A, Sorensen CB, Lindelof PE. Conductance-quantization broadening mechanisms in quantum point contacts. PHYSICAL REVIEW. B, CONDENSED MATTER 1995; 51:2282-2286. [PMID: 9978979 DOI: 10.1103/physrevb.51.2282] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Chu CS, Chou MH. Effects of an impurity on the conductance and thermopower of a saddle-point-potential quantum point contact. PHYSICAL REVIEW. B, CONDENSED MATTER 1994; 50:14212-14222. [PMID: 9975642 DOI: 10.1103/physrevb.50.14212] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Kozub VI, Rudin AM. Phonon-drag thermopower of quantum point contacts. PHYSICAL REVIEW. B, CONDENSED MATTER 1994; 50:2681-2684. [PMID: 9976497 DOI: 10.1103/physrevb.50.2681] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Chen Z, Sorbello RS. Local heating in mesoscopic systems. PHYSICAL REVIEW. B, CONDENSED MATTER 1993; 47:13527-13534. [PMID: 10005663 DOI: 10.1103/physrevb.47.13527] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Beenakker CW, Staring AA. Theory of the thermopower of a quantum dot. PHYSICAL REVIEW. B, CONDENSED MATTER 1992; 46:9667-9676. [PMID: 10002777 DOI: 10.1103/physrevb.46.9667] [Citation(s) in RCA: 57] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Okuyama Y, Tokuda N. Thermoelectric power of a narrow constriction in the adiabatic approximation. PHYSICAL REVIEW. B, CONDENSED MATTER 1992; 46:2610-2612. [PMID: 10003941 DOI: 10.1103/physrevb.46.2610] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Molenkamp LW, Gravier T, Buijk OJ, Mabesoone MA, Foxon CT. Peltier coefficient and thermal conductance of a quantum point contact. PHYSICAL REVIEW LETTERS 1992; 68:3765-3768. [PMID: 10045791 DOI: 10.1103/physrevlett.68.3765] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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Palacios JJ, Tejedor C. Magnetic-field effects on the transport coefficients of a quantum point contact. PHYSICAL REVIEW. B, CONDENSED MATTER 1992; 45:13725-13728. [PMID: 10001470 DOI: 10.1103/physrevb.45.13725] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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