1
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Spin-thermoelectric effects in a quantum dot hybrid system with magnetic insulator. Sci Rep 2022; 12:5348. [PMID: 35354843 PMCID: PMC8969188 DOI: 10.1038/s41598-022-09105-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2021] [Accepted: 03/10/2022] [Indexed: 11/08/2022] Open
Abstract
AbstractWe investigate spin thermoelectric properties of a hybrid system consisting of a single-level quantum dot attached to magnetic insulator and metal electrodes. Magnetic insulator is assumed to be of ferromagnetic type and is a source of magnons, whereas metallic lead is reservoir of electrons. The temperature gradient set between the magnetic insulator and metallic electrodes induces the spin current flowing through the system. The generated spin current of magnonic (electric) type is converted to electric (magnonic) spin current by means of quantum dot. Expanding spin and heat currents flowing through the system, up to linear order, we introduce basic spin thermoelectric coefficients including spin conductance, spin Seebeck and spin Peltier coefficients and heat conductance. We analyse the spin thermoelectric properties of the system in two cases: in the large ondot Coulomb repulsion limit and when these interactions are finite.
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2
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Manaparambil A, Weymann I. Spin Seebeck effect of correlated magnetic molecules. Sci Rep 2021; 11:9192. [PMID: 33911112 PMCID: PMC8080696 DOI: 10.1038/s41598-021-88373-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2021] [Accepted: 04/09/2021] [Indexed: 11/15/2022] Open
Abstract
In this paper we investigate the spin-resolved thermoelectric properties of strongly correlated molecular junctions in the linear response regime. The magnetic molecule is modeled by a single orbital level to which the molecular core spin is attached by an exchange interaction. Using the numerical renormalization group method we analyze the behavior of the (spin) Seebeck effect, heat conductance and figure of merit for different model parameters of the molecule. We show that the thermopower strongly depends on the strength and type of the exchange interaction as well as the molecule's magnetic anisotropy. When the molecule is coupled to ferromagnetic leads, the thermoelectric properties reveal an interplay between the spin-resolved tunneling processes and intrinsic magnetic properties of the molecule. Moreover, in the case of finite spin accumulation in the leads, the system exhibits the spin Seebeck effect. We demonstrate that a considerable spin Seebeck effect can develop when the molecule exhibits an easy-plane magnetic anisotropy, while the sign of the spin thermopower depends on the type and magnitude of the molecule's exchange interaction.
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Affiliation(s)
- Anand Manaparambil
- Institute of Spintronics and Quantum Information, Faculty of Physics, Adam Mickiewicz University in Poznań, ul. Uniwersytetu Poznańskiego 2, 61-614, Poznań, Poland.
| | - Ireneusz Weymann
- Institute of Spintronics and Quantum Information, Faculty of Physics, Adam Mickiewicz University in Poznań, ul. Uniwersytetu Poznańskiego 2, 61-614, Poznań, Poland
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3
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Tan ZB, Laitinen A, Kirsanov NS, Galda A, Vinokur VM, Haque M, Savin A, Golubev DS, Lesovik GB, Hakonen PJ. Thermoelectric current in a graphene Cooper pair splitter. Nat Commun 2021; 12:138. [PMID: 33420055 PMCID: PMC7794233 DOI: 10.1038/s41467-020-20476-7] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2020] [Accepted: 11/29/2020] [Indexed: 11/17/2022] Open
Abstract
Generation of electric voltage in a conductor by applying a temperature gradient is a fundamental phenomenon called the Seebeck effect. This effect and its inverse is widely exploited in diverse applications ranging from thermoelectric power generators to temperature sensing. Recently, a possibility of thermoelectricity arising from the interplay of the non-local Cooper pair splitting and the elastic co-tunneling in the hybrid normal metal-superconductor-normal metal structures was predicted. Here, we report the observation of the non-local Seebeck effect in a graphene-based Cooper pair splitting device comprising two quantum dots connected to an aluminum superconductor and present a theoretical description of this phenomenon. The observed non-local Seebeck effect offers an efficient tool for producing entangled electrons. Thermoelectricity due to the interplay of the nonlocal Cooper pair splitting and the elastic co-tunneling in normal metal-superconductor-normal metal structure is predicted. Here, the authors observe the non-local Seebeck effect in a graphene-based Cooper pair splitting device.
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Affiliation(s)
- Z B Tan
- Low Temperature Laboratory, Department of Applied Physics, Aalto University, Espoo, Finland.,Shenzhen Institute for Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen, 518055, China
| | - A Laitinen
- Low Temperature Laboratory, Department of Applied Physics, Aalto University, Espoo, Finland
| | - N S Kirsanov
- Low Temperature Laboratory, Department of Applied Physics, Aalto University, Espoo, Finland.,Terra Quantum AG, St. Gallerstrasse 16A, 9400, Rorschach, Switzerland.,Moscow Institute of Physics and Technology, Institutskii Per. 9, Dolgoprudny, Moscow Distr., 141700, Russian Federation.,Consortium for Advanced Science and Engineering (CASE), University of Chicago, 5801 S Ellis Avenue, Chicago, IL, 60637, USA
| | - A Galda
- James Franck Institute, University of Chicago, Chicago, IL, 60637, USA.,Materials Science Division, Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, IL, 60439, USA
| | - V M Vinokur
- Consortium for Advanced Science and Engineering (CASE), University of Chicago, 5801 S Ellis Avenue, Chicago, IL, 60637, USA.,Materials Science Division, Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, IL, 60439, USA
| | - M Haque
- Low Temperature Laboratory, Department of Applied Physics, Aalto University, Espoo, Finland
| | - A Savin
- Low Temperature Laboratory, Department of Applied Physics, Aalto University, Espoo, Finland
| | - D S Golubev
- QTF Centre of Excellence, Department of Applied Physics, Aalto University, FI-00076, Aalto, Finland
| | - G B Lesovik
- Terra Quantum AG, St. Gallerstrasse 16A, 9400, Rorschach, Switzerland.,Moscow Institute of Physics and Technology, Institutskii Per. 9, Dolgoprudny, Moscow Distr., 141700, Russian Federation
| | - P J Hakonen
- Low Temperature Laboratory, Department of Applied Physics, Aalto University, Espoo, Finland. .,QTF Centre of Excellence, Department of Applied Physics, Aalto University, FI-00076, Aalto, Finland.
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4
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Dutta B, Majidi D, Talarico NW, Lo Gullo N, Courtois H, Winkelmann CB. Single-Quantum-Dot Heat Valve. PHYSICAL REVIEW LETTERS 2020; 125:237701. [PMID: 33337212 DOI: 10.1103/physrevlett.125.237701] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2020] [Revised: 10/11/2020] [Accepted: 10/21/2020] [Indexed: 06/12/2023]
Abstract
We demonstrate gate control of electronic heat flow in a thermally biased single-quantum-dot junction. Electron temperature maps taken in the immediate vicinity of the junction, as a function of the gate and bias voltages applied to the device, reveal clearly defined Coulomb diamond patterns that indicate a maximum heat transfer at the charge degeneracy point. The nontrivial bias and gate dependence of this heat valve results from the quantum nature of the dot at the heart of device and its strong coupling to leads.
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Affiliation(s)
- B Dutta
- Univ. Grenoble Alpes, CNRS, Grenoble INP, Institut Néel, 25 Avenue des Martyrs, 38042 Grenoble, France
| | - D Majidi
- Univ. Grenoble Alpes, CNRS, Grenoble INP, Institut Néel, 25 Avenue des Martyrs, 38042 Grenoble, France
| | - N W Talarico
- QTF Centre of Excellence, Turku Centre for Quantum Physics, Department of Physics and Astronomy, University of Turku, 20014 Turku, Finland
| | - N Lo Gullo
- QTF Centre of Excellence, Turku Centre for Quantum Physics, Department of Physics and Astronomy, University of Turku, 20014 Turku, Finland
| | - H Courtois
- Univ. Grenoble Alpes, CNRS, Grenoble INP, Institut Néel, 25 Avenue des Martyrs, 38042 Grenoble, France
| | - C B Winkelmann
- Univ. Grenoble Alpes, CNRS, Grenoble INP, Institut Néel, 25 Avenue des Martyrs, 38042 Grenoble, France
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5
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Maillet O, Subero D, Peltonen JT, Golubev DS, Pekola JP. Electric field control of radiative heat transfer in a superconducting circuit. Nat Commun 2020; 11:4326. [PMID: 32859939 PMCID: PMC7455700 DOI: 10.1038/s41467-020-18163-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2020] [Accepted: 08/10/2020] [Indexed: 11/18/2022] Open
Abstract
Heat is detrimental for the operation of quantum systems, yet it fundamentally behaves according to quantum mechanics, being phase coherent and universally quantum-limited regardless of its carriers. Due to their robustness, superconducting circuits integrating dissipative elements are ideal candidates to emulate many-body phenomena in quantum heat transport, hitherto scarcely explored experimentally. However, their ability to tackle the underlying full physical richness is severely hindered by the exclusive use of a magnetic flux as a control parameter and requires complementary approaches. Here, we introduce a dual, magnetic field-free circuit where charge quantization in a superconducting island enables thorough electric field control. We thus tune the thermal conductance, close to its quantum limit, of a single photonic channel between two mesoscopic reservoirs. We observe heat flow oscillations originating from the competition between Cooper-pair tunnelling and Coulomb repulsion in the island, well captured by a simple model. Our results highlight the consequences of charge-phase conjugation on heat transport, with promising applications in thermal management of quantum devices and design of microbolometers.
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Affiliation(s)
- Olivier Maillet
- QTF Centre of Excellence, Department of Applied Physics, Aalto University School of Science, P.O. Box 13500, 00076, Aalto, Finland.
| | - Diego Subero
- QTF Centre of Excellence, Department of Applied Physics, Aalto University School of Science, P.O. Box 13500, 00076, Aalto, Finland
| | - Joonas T Peltonen
- QTF Centre of Excellence, Department of Applied Physics, Aalto University School of Science, P.O. Box 13500, 00076, Aalto, Finland
| | - Dmitry S Golubev
- QTF Centre of Excellence, Department of Applied Physics, Aalto University School of Science, P.O. Box 13500, 00076, Aalto, Finland
| | - Jukka P Pekola
- QTF Centre of Excellence, Department of Applied Physics, Aalto University School of Science, P.O. Box 13500, 00076, Aalto, Finland
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6
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Nguyen TKT, Kiselev MN. Thermoelectric Transport in a Three-Channel Charge Kondo Circuit. PHYSICAL REVIEW LETTERS 2020; 125:026801. [PMID: 32701341 DOI: 10.1103/physrevlett.125.026801] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2019] [Accepted: 06/16/2020] [Indexed: 06/11/2023]
Abstract
We theoretically investigate the thermoelectric transport through a circuit implementation of the three-channel charge Kondo model quantum simulator [Z. Iftikhar et al., Science 360, 1315 (2018)SCIEAS0036-807510.1126/science.aan5592]. The universal temperature scaling law of the Seebeck coefficient is computed perturbatively approaching the non-Fermi liquid strong coupling fixed point using the Abelian bosonization technique. The predicted T^{1/3}logT scaling behavior of the thermoelectric power sheds light on the properties of Z_{3} emerging parafermions and gives access to exploring prefractionalized zero modes in the quantum transport experiments. We discuss a generalization of approach for investigating a multichannel Kondo problem with emergent Z_{N}→Z_{M} crossovers between "weak" non-Fermi liquid regimes corresponding to different low-temperature fixed points.
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Affiliation(s)
- T K T Nguyen
- Institute of Physics, Vietnam Academy of Science and Technology, 10 Dao Tan, Hanoi, Vietnam
| | - M N Kiselev
- The Abdus Salam International Centre for Theoretical Physics, Strada Costiera 11, I-34151, Trieste, Italy
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7
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How to measure the entropy of a mesoscopic system via thermoelectric transport. Nat Commun 2019; 10:5801. [PMID: 31862879 PMCID: PMC6925120 DOI: 10.1038/s41467-019-13630-3] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2019] [Accepted: 11/12/2019] [Indexed: 11/08/2022] Open
Abstract
Entropy is a fundamental thermodynamic quantity indicative of the accessible degrees of freedom in a system. While it has been suggested that the entropy of a mesoscopic system can yield nontrivial information on emergence of exotic states, its measurement in such small electron-number system is a daunting task. Here we propose a method to extract the entropy of a Coulomb-blockaded mesoscopic system from transport measurements. We prove analytically and demonstrate numerically the applicability of the method to such a mesoscopic system of arbitrary spectrum and degeneracies. We then apply our procedure to measurements of thermoelectric response of a single quantum dot, and demonstrate how it can be used to deduce the entropy change across Coulomb-blockade valleys, resolving, along the way, a long-standing puzzle of the experimentally observed finite thermoelectric response at the apparent particle-hole symmetric point.
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8
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Jaliel G, Puddy RK, Sánchez R, Jordan AN, Sothmann B, Farrer I, Griffiths JP, Ritchie DA, Smith CG. Experimental Realization of a Quantum Dot Energy Harvester. PHYSICAL REVIEW LETTERS 2019; 123:117701. [PMID: 31573223 DOI: 10.1103/physrevlett.123.117701] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2019] [Revised: 04/26/2019] [Indexed: 06/10/2023]
Abstract
We demonstrate experimentally an autonomous nanoscale energy harvester that utilizes the physics of resonant tunneling quantum dots. Gate-defined quantum dots on GaAs/AlGaAs high-electron-mobility transistors are placed on either side of a hot-electron reservoir. The discrete energy levels of the quantum dots are tuned to be aligned with low energy electrons on one side and high energy electrons on the other side of the hot reservoir. The quantum dots thus act as energy filters and allow for the conversion of heat from the cavity into electrical power. Our energy harvester, measured at an estimated base temperature of 75 mK in a He^{3}/He^{4} dilution refrigerator, can generate a thermal power of 0.13 fW for a temperature difference across each dot of about 67 mK.
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Affiliation(s)
- G Jaliel
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom
| | - R K Puddy
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom
| | - R Sánchez
- Departamento de Física Teórica de la Materia Condensada and Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, E-28049 Madrid, Spain
| | - A N Jordan
- Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627, USA
| | - B Sothmann
- Theoretische Physik, Universität Duisburg-Essen and CENIDE, D-47048 Duisburg, Germany
| | - I Farrer
- Department of Electronic and Electrical Engineering, University of Sheffield, Mappin Street, Sheffield S1 3JD, United Kingdom
| | - J P Griffiths
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom
| | - D A Ritchie
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom
| | - C G Smith
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom
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9
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Thermoelectric Inversion in a Resonant Quantum Dot-Cavity System in the Steady-State Regime. NANOMATERIALS 2019; 9:nano9050741. [PMID: 31091757 PMCID: PMC6566154 DOI: 10.3390/nano9050741] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/08/2019] [Revised: 05/05/2019] [Accepted: 05/07/2019] [Indexed: 11/21/2022]
Abstract
We theoretically investigate thermoelectric effects in a quantum dot system under the influence of a linearly polarized photon field confined to a 3D cavity. A temperature gradient is applied to the system via two electron reservoirs that are connected to each end of the quantum dot system. The thermoelectric current in the steady state is explored using a quantum master equation. In the presence of the quantized photons, extra channels, the photon replica states, are formed generating a photon-induced thermoelectric current. We observe that the photon replica states contribute to the transport irrespective of the direction of the thermal gradient. In the off-resonance regime, when the energy difference between the lowest states of the quantum dot system is smaller than the photon energy, the thermoelectric current is almost blocked and a plateau is seen in the thermoelectric current for strong electron–photon coupling strength. In the resonant regime, an inversion of thermoelectric current emerges due to the Rabi-splitting. Therefore, the photon field can change both the magnitude and the sign of the thermoelectric current induced by the temperature gradient in the absence of a voltage bias between the leads.
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10
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Dutta B, Majidi D, García Corral A, Erdman PA, Florens S, Costi TA, Courtois H, Winkelmann CB. Direct Probe of the Seebeck Coefficient in a Kondo-Correlated Single-Quantum-Dot Transistor. NANO LETTERS 2019; 19:506-511. [PMID: 30566839 DOI: 10.1021/acs.nanolett.8b04398] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
We report on the first measurement of the Seebeck coefficient in a tunnel-contacted and gate-tunable individual single-quantum dot junction in the Kondo regime, fabricated using the electromigration technique. This fundamental thermoelectric parameter is obtained by directly monitoring the magnitude of the voltage induced in response to a temperature difference across the junction, while keeping a zero net tunneling current through the device. In contrast to bulk materials and single molecules probed in a scanning tunneling microscopy (STM) configuration, investigating the thermopower in nanoscale electronic transistors benefits from the electric tunability to showcase prominent quantum effects. Here, striking sign changes of the Seebeck coefficient are induced by varying the temperature, depending on the spin configuration in the quantum dot. The comparison with numerical renormalization group (NRG) calculations demonstrates that the tunneling density of states is generically asymmetric around the Fermi level in the leads, both in the cotunneling and Kondo regimes.
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Affiliation(s)
- Bivas Dutta
- Université Grenoble Alpes, CNRS, Grenoble INP*, Institut Néel , 38000 Grenoble , France
| | - Danial Majidi
- Université Grenoble Alpes, CNRS, Grenoble INP*, Institut Néel , 38000 Grenoble , France
| | - Alvaro García Corral
- Université Grenoble Alpes, CNRS, Grenoble INP*, Institut Néel , 38000 Grenoble , France
| | - Paolo A Erdman
- NEST, Scuola Normale Superiore and Istituto Nanoscienze-CNR , 56127 Pisa , Italy
| | - Serge Florens
- Université Grenoble Alpes, CNRS, Grenoble INP*, Institut Néel , 38000 Grenoble , France
| | - Theo A Costi
- Peter Grünberg Institut , Forschungszentrum Jülich , 52425 Jülich , Germany
| | - Hervé Courtois
- Université Grenoble Alpes, CNRS, Grenoble INP*, Institut Néel , 38000 Grenoble , France
| | - Clemens B Winkelmann
- Université Grenoble Alpes, CNRS, Grenoble INP*, Institut Néel , 38000 Grenoble , France
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11
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Svilans A, Josefsson M, Burke AM, Fahlvik S, Thelander C, Linke H, Leijnse M. Thermoelectric Characterization of the Kondo Resonance in Nanowire Quantum Dots. PHYSICAL REVIEW LETTERS 2018; 121:206801. [PMID: 30500238 DOI: 10.1103/physrevlett.121.206801] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2018] [Indexed: 06/09/2023]
Abstract
We experimentally verify hitherto untested theoretical predictions about the thermoelectric properties of Kondo correlated quantum dots (QDs). The specific conditions required for this study are obtained by using QDs epitaxially grown in nanowires, combined with a recently developed method for controlling and measuring temperature differences at the nanoscale. This makes it possible to obtain data of very high quality both below and above the Kondo temperature, and allows a quantitative comparison with theoretical predictions. Specifically, we verify that Kondo correlations can induce a polarity change of the thermoelectric current, which can be reversed either by increasing the temperature or by applying a magnetic field.
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Affiliation(s)
- Artis Svilans
- Division of Solid State Physics and NanoLund, Lund University, Box 118, S-221 00 Lund, Sweden
| | - Martin Josefsson
- Division of Solid State Physics and NanoLund, Lund University, Box 118, S-221 00 Lund, Sweden
| | - Adam M Burke
- Division of Solid State Physics and NanoLund, Lund University, Box 118, S-221 00 Lund, Sweden
| | - Sofia Fahlvik
- Division of Solid State Physics and NanoLund, Lund University, Box 118, S-221 00 Lund, Sweden
| | - Claes Thelander
- Division of Solid State Physics and NanoLund, Lund University, Box 118, S-221 00 Lund, Sweden
| | - Heiner Linke
- Division of Solid State Physics and NanoLund, Lund University, Box 118, S-221 00 Lund, Sweden
| | - Martin Leijnse
- Division of Solid State Physics and NanoLund, Lund University, Box 118, S-221 00 Lund, Sweden
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12
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Dutta B, Peltonen JT, Antonenko DS, Meschke M, Skvortsov MA, Kubala B, König J, Winkelmann CB, Courtois H, Pekola JP. Thermal Conductance of a Single-Electron Transistor. PHYSICAL REVIEW LETTERS 2017; 119:077701. [PMID: 28949696 DOI: 10.1103/physrevlett.119.077701] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Indexed: 06/07/2023]
Abstract
We report on combined measurements of heat and charge transport through a single-electron transistor. The device acts as a heat switch actuated by the voltage applied on the gate. The Wiedemann-Franz law for the ratio of heat and charge conductances is found to be systematically violated away from the charge degeneracy points. The observed deviation agrees well with the theoretical expectation. With a large temperature drop between the source and drain, the heat current away from degeneracy deviates from the standard quadratic dependence in the two temperatures.
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Affiliation(s)
- B Dutta
- Université Grenoble Alpes, CNRS, Institut Néel, 25 Avenue des Martyrs, 38042 Grenoble, France
| | - J T Peltonen
- Low Temperature Laboratory, Department of Applied Physics, Aalto University School of Science, P.O. Box 13500, 00076 Aalto, Finland
| | - D S Antonenko
- Skolkovo Institute of Science and Technology, Skolkovo, 143026 Moscow, Russia
- L. D. Landau Institute for Theoretical Physics, 142432 Chernogolovka, Russia
- Moscow Institute of Physics and Technology, Moscow, 141700, Russia
| | - M Meschke
- Low Temperature Laboratory, Department of Applied Physics, Aalto University School of Science, P.O. Box 13500, 00076 Aalto, Finland
| | - M A Skvortsov
- Skolkovo Institute of Science and Technology, Skolkovo, 143026 Moscow, Russia
- L. D. Landau Institute for Theoretical Physics, 142432 Chernogolovka, Russia
- Moscow Institute of Physics and Technology, Moscow, 141700, Russia
| | - B Kubala
- Institute for Complex Quantum Systems and IQST, University of Ulm, 89069 Ulm, Germany
| | - J König
- Theoretische Physik and CENIDE, Universität Duisburg-Essen, 47048 Duisburg, Germany
| | - C B Winkelmann
- Université Grenoble Alpes, CNRS, Institut Néel, 25 Avenue des Martyrs, 38042 Grenoble, France
| | - H Courtois
- Université Grenoble Alpes, CNRS, Institut Néel, 25 Avenue des Martyrs, 38042 Grenoble, France
| | - J P Pekola
- Low Temperature Laboratory, Department of Applied Physics, Aalto University School of Science, P.O. Box 13500, 00076 Aalto, Finland
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13
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Samuelsson P, Kheradsoud S, Sothmann B. Optimal Quantum Interference Thermoelectric Heat Engine with Edge States. PHYSICAL REVIEW LETTERS 2017; 118:256801. [PMID: 28696742 DOI: 10.1103/physrevlett.118.256801] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2016] [Indexed: 06/07/2023]
Abstract
We show theoretically that a thermoelectric heat engine, operating exclusively due to quantum-mechanical interference, can reach optimal linear-response performance. A chiral edge state implementation of a close-to-optimal heat engine is proposed in an electronic Mach-Zehnder interferometer with a mesoscopic capacitor coupled to one arm. We demonstrate that the maximum power and corresponding efficiency can reach 90% and 83%, respectively, of the theoretical maximum. The proposed heat engine can be realized with existing experimental techniques and has a performance robust against moderate dephasing.
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Affiliation(s)
- Peter Samuelsson
- Physics Department and NanoLund, Lund University, Box 118, SE-22100 Lund, Sweden
| | - Sara Kheradsoud
- Physics Department and NanoLund, Lund University, Box 118, SE-22100 Lund, Sweden
| | - Björn Sothmann
- Theoretische Physik, Universität Duisburg-Essen and CENIDE, D-47048 Duisburg, Germany
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14
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Weymann I. Spin Seebeck effect in quantum dot side-coupled to topological superconductor. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:095301. [PMID: 28001133 DOI: 10.1088/1361-648x/aa5526] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The spin-resolved thermoelectric transport properties of a quantum dot coupled to ferromagnetic leads and side-coupled to a topological superconductor wire hosting Majorana zero-energy modes are studied theoretically. The calculations are performed in the linear response regime by using the numerical renormalization group method. It is shown that transport characteristics are determined by the interplay of Kondo correlations, exchange field due to the presence of ferromagnets and the strength of coupling to Majorana wire. These different energy scales are revealed in the behavior of the Seebeck and spin Seebeck coefficients, which exhibit an enhancement for temperatures of the order of the coupling strength to topological wire. Moreover, it is demonstrated that additional sign changes of the thermopower can occur due to the presence of Majorana zero-energy modes. These findings may provide additional fingerprints of the presence of Majorana fermions.
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Affiliation(s)
- Ireneusz Weymann
- Faculty of Physics, Adam Mickiewicz University, Umultowska 85, 61-614 Poznań, Poland
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15
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Wójcik KP, Weymann I. Strong spin Seebeck effect in Kondo T-shaped double quantum dots. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:055303. [PMID: 27941235 DOI: 10.1088/1361-648x/29/5/055303] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We investigate, taking a theoretical approach, the thermoelectric and spin thermoelectric properties of a T-shaped double quantum dot strongly coupled to two ferromagnetic leads, focusing on the transport regime in which the system exhibits the two-stage Kondo effect. We study the dependence of the (spin) Seebeck coefficient, the corresponding power factor and the figure of merit on temperature, leads' spin polarization and dot level position. We show that the thermal conductance fulfills a modified Wiedemann-Franz law, also in the regime of suppression of subsequent stages of the Kondo effect by the exchange field resulting from the presence of ferromagnets. Moreover, we demonstrate that the spin thermopower is enhanced at temperatures corresponding to the second stage of Kondo screening. Very interestingly, the spin-thermoelectric response of the system is found to be highly sensitive to the spin polarization of the leads. In some cases spin polarization of the order of 1% is sufficient for a strong spin Seebeck effect to occur. This is explained as a consequence of the interplay between the two-stage Kondo effect and the exchange field induced in the double quantum dot. Due to the possibility of tuning the exchange field by the choice of gate voltage, the spin thermopower may also be tuned to be maximal for desired spin polarization of the leads. All calculations are performed with the aid of the numerical renormalization group technique.
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Affiliation(s)
- K P Wójcik
- Faculty of Physics, Adam Mickiewicz University, Umultowska 85, 61-614 Poznań, Poland
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16
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Ganesan P, Lakshmipathi S. Influence of dopants Cu, Ga, In, Hg on the electronic structure of CdnSn (n = 6, 15) clusters – a DFT study. RSC Adv 2016. [DOI: 10.1039/c6ra15049g] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The influence of dopants on the electronic structure and the optical properties of doped Cdn−yXySn (n = 6, 15; y = 1, 2, 4) clusters, studied using DFT and TDDFT methods.
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17
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Sothmann B, Sánchez R, Jordan AN. Thermoelectric energy harvesting with quantum dots. NANOTECHNOLOGY 2015; 26:032001. [PMID: 25549281 DOI: 10.1088/0957-4484/26/3/032001] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We review recent theoretical work on thermoelectric energy harvesting in multi-terminal quantum-dot setups. We first discuss several examples of nanoscale heat engines based on Coulomb-coupled conductors. In particular, we focus on quantum dots in the Coulomb-blockade regime, chaotic cavities and resonant tunneling through quantum dots and wells. We then turn toward quantum-dot heat engines that are driven by bosonic degrees of freedom such as phonons, magnons and microwave photons. These systems provide interesting connections to spin caloritronics and circuit quantum electrodynamics.
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Affiliation(s)
- Björn Sothmann
- Département de Physique Théorique, Université de Genève, CH-1211 Genève 4, Switzerland
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18
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Crépieux A, Michelini F. Mixed, charge and heat noises in thermoelectric nanosystems. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:015302. [PMID: 25493577 DOI: 10.1088/0953-8984/27/1/015302] [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
Mixed, charge and heat current fluctuations as well as thermoelectric differential conductances are considered for non-interacting nanosystems connected to reservoirs. Using the Landauer-Büttiker formalism, we derive general expressions for these quantities and consider their possible relationships in the entire ranges of temperature, voltage and coupling to the environment or reservoirs. We introduce a dimensionless quantity given by the ratio between the product of mixed noises and the product of charge and heat noises, distinguishing between the auto-ratio defined in the same reservoir and the cross-ratio between distinct reservoirs. From the linear response regime to the high-voltage regime, we further specify the analytical expressions of differential conductances, noises and ratios of noises, and examine their behavior in two concrete nanosystems: a quantum point contact in an ohmic environment and a single energy level quantum dot connected to reservoirs. In the linear response regime, we find that these ratios are equal to each other and are simply related to the figure of merit. They can be expressed in terms of differential conductances with the help of the fluctuation-dissipation theorem. In the non-linear regime, these ratios radically distinguish between themselves as the auto-ratio remains bounded by one, while the cross-ratio exhibits rich and complex behaviors. In the quantum dot nanosystem, we moreover demonstrate that the thermoelectric efficiency can be expressed as a ratio of noises in the non-linear Schottky regime. In the intermediate voltage regime, the cross-ratio changes sign and diverges, which evidences a change of sign in the heat cross-noise.
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Affiliation(s)
- Adeline Crépieux
- Aix Marseille Université, Université de Toulon, CNRS, CPT UMR 7332, 13288 Marseille, France
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19
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Zimbovskaya NA. The effect of Coulomb interactions on thermoelectric properties of quantum dots. J Chem Phys 2014; 140:104706. [PMID: 24628195 DOI: 10.1063/1.4867697] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Affiliation(s)
- Natalya A Zimbovskaya
- Department of Physics and Electronics, University of Puerto Rico-Humacao, CUH Station, Humacao, Puerto Rico 00791, USA and Institute for Functional Nanomaterials, University of Puerto Rico, San Juan, Puerto Ruco 00931, USA
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20
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Bergenfeldt C, Samuelsson P, Sothmann B, Flindt C, Büttiker M. Hybrid microwave-cavity heat engine. PHYSICAL REVIEW LETTERS 2014; 112:076803. [PMID: 24579624 DOI: 10.1103/physrevlett.112.076803] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2013] [Indexed: 06/03/2023]
Abstract
We propose and analyze the use of hybrid microwave cavities as quantum heat engines. A possible realization consists of two macroscopically separated quantum-dot conductors coupled capacitively to the fundamental mode of a microwave cavity. We demonstrate that an electrical current can be induced in one conductor through cavity-mediated processes by heating up the other conductor. The heat engine can reach Carnot efficiency with optimal conversion of heat to work. When the system delivers the maximum power, the efficiency can be a large fraction of the Carnot efficiency. The heat engine functions even with moderate electronic relaxation and dephasing in the quantum dots. We provide detailed estimates for the electrical current and output power using realistic parameters.
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Affiliation(s)
| | - Peter Samuelsson
- Physics Department, Lund University, Box 118, SE-22100 Lund, Sweden
| | - Björn Sothmann
- Département de Physique Théorique, Université de Genève, CH-1211 Genève 4, Switzerland
| | - Christian Flindt
- Département de Physique Théorique, Université de Genève, CH-1211 Genève 4, Switzerland
| | - Markus Büttiker
- Département de Physique Théorique, Université de Genève, CH-1211 Genève 4, Switzerland
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21
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Karwacki L, Trocha P, Barnaś J. Spin-dependent thermoelectric properties of a Kondo-correlated quantum dot with Rashba spin-orbit coupling. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2013; 25:505305. [PMID: 24275387 DOI: 10.1088/0953-8984/25/50/505305] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Thermoelectric transport phenomena in a single-level quantum dot coupled to ferromagnetic leads are considered theoretically in the Kondo regime. The dot is described by the Anderson model with Rashba type spin-orbit interactions. The finite-U mean field slave boson technique is used to describe transport characteristics, such as the heat conductance, thermopower and thermoelectric efficiency (figure of merit). The role of quantum interference effects in the thermoelectric parameters is also analyzed.
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Affiliation(s)
- L Karwacki
- Faculty of Physics, Adam Mickiewicz University, 61-614 Poznań, Poland
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22
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Guo N, Zhou Z, Huang Y, Yang X, Jiang R, Ma Z, Sun CQ. Size, shape, and temperature dependence of the phonon relaxation dynamics of CdSe nanocrystals. Chem Phys Lett 2013. [DOI: 10.1016/j.cplett.2013.09.024] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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23
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Chi F, Dubi Y. Microwave-mediated heat transport in a quantum dot attached to leads. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2012; 24:145301. [PMID: 22410747 DOI: 10.1088/0953-8984/24/14/145301] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The thermoelectric effect in a quantum dot (QD) attached to two leads in the presence of microwave fields is studied by using the Keldysh nonequilibrium Green function technique. When the microwave is applied only on the QD and in the linear response regime, the main peaks in the thermoelectric figure of merit and the thermopower are found to decrease, with the emergence of a set of photon-induced peaks. Under this condition the microwave field cannot generate heat current or electrical bias voltage. Surprisingly, when the microwave field is applied only to one (bright) lead and not to the other (dark) lead or the QD, heat flows mostly from the dark to the bright lead, almost irrespective of the direction of the thermal gradient. We attribute this effect to microwave-induced opening of additional transport channels below the Fermi energy. The microwave field can change both the magnitude and the sign of the electrical bias voltage induced by the temperature gradient.
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Affiliation(s)
- Feng Chi
- College of Engineering, Bohai University, Jinzhou 121013, People's Republic of China.
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24
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Lin W, Hehn M, Chaput L, Negulescu B, Andrieu S, Montaigne F, Mangin S. Giant spin-dependent thermoelectric effect in magnetic tunnel junctions. Nat Commun 2012; 3:744. [DOI: 10.1038/ncomms1748] [Citation(s) in RCA: 104] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2011] [Accepted: 02/13/2012] [Indexed: 11/09/2022] Open
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25
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Zheng J, Chi F, Lu XD, Zhang KC. Thermoelectric effect in an Aharonov-Bohm ring with an embedded quantum dot. NANOSCALE RESEARCH LETTERS 2012; 7:157. [PMID: 22369454 PMCID: PMC3350442 DOI: 10.1186/1556-276x-7-157] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/09/2011] [Accepted: 02/28/2012] [Indexed: 05/31/2023]
Abstract
Thermoelectric effect is studied in an Aharonov-Bohm interferometer with an embedded quantum dot (QD) in the Coulomb blockade regime. The electrical conductance, electron thermal conductance, thermopower, and thermoelectric figure-of-merit are calculated by using the Keldysh Green's function method. It is found that the figure-of-merit ZT of the QD ring may be quite high due to the Fano effect originated from the quantum interference effect. Moreover, the thermoelectric efficiency is sensitive to the magnitude of the dot-lead and inter-lead coupling strengthes. The effect of intradot Coulomb repulsion on ZT is significant in the weak-coupling regime, and then large ZT values can be obtained at rather high temperature.
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Affiliation(s)
- Jun Zheng
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China
| | - Feng Chi
- College of Engineering, Bohai University, Jinzhou 121013, China
| | - Xiao-Dong Lu
- College of Engineering, Bohai University, Jinzhou 121013, China
| | - Kai-Cheng Zhang
- Department of Physics, Bohai University, Jinzhou 121000, China
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26
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Liu YS, Hong XK, Feng JF, Yang XF. Fano-Rashba effect in thermoelectricity of a double quantum dot molecular junction. NANOSCALE RESEARCH LETTERS 2011; 6:618. [PMID: 22151740 PMCID: PMC3258288 DOI: 10.1186/1556-276x-6-618] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/25/2011] [Accepted: 12/07/2011] [Indexed: 05/31/2023]
Abstract
We examine the relation between the phase-coherent processes and spin-dependent thermoelectric effects in an Aharonov-Bohm (AB) interferometer with a Rashba quantum dot (QD) in each of its arm by using the Green's function formalism and equation of motion (EOM) technique. Due to the interplay between quantum destructive interference and Rashba spin-orbit interaction (RSOI) in each QD, an asymmetrical transmission node splits into two spin-dependent asymmetrical transmission nodes in the transmission spectrum and, as a consequence, results in the enhancement of the spin-dependent thermoelectric effects near the spin-dependent asymmetrical transmission nodes. We also examine the evolution of spin-dependent thermoelectric effects from a symmetrical parallel geometry to a configuration in series. It is found that the spin-dependent thermoelectric effects can be enhanced by controlling the dot-electrode coupling strength. The simple analytical expressions are also derived to support our numerical results.PACS numbers: 73.63.Kv; 71.70.Ej; 72.20.Pa.
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Affiliation(s)
- YS Liu
- Jiangsu Laboratory of Advanced Functional materials and College of Physics and Engineering, Changshu Institute of Technology, Changshu 215500, China
| | - XK Hong
- Jiangsu Laboratory of Advanced Functional materials and College of Physics and Engineering, Changshu Institute of Technology, Changshu 215500, China
| | - JF Feng
- Jiangsu Laboratory of Advanced Functional materials and College of Physics and Engineering, Changshu Institute of Technology, Changshu 215500, China
| | - XF Yang
- Jiangsu Laboratory of Advanced Functional materials and College of Physics and Engineering, Changshu Institute of Technology, Changshu 215500, China
- Department of Theoretical Chemistry, School of Biotechnology, Royal Institute of Technology, S-106 91 Stockholm, Sweden
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27
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Fischer SA, Isborn CM, Prezhdo OV. Excited states and optical absorption of small semiconducting clusters: Dopants, defects and charging. Chem Sci 2011. [DOI: 10.1039/c0sc00626b] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
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28
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Wang RQ, Sheng L, Shen R, Wang B, Xing DY. Thermoelectric effect in single-molecule-magnet junctions. PHYSICAL REVIEW LETTERS 2010; 105:057202. [PMID: 20867951 DOI: 10.1103/physrevlett.105.057202] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2010] [Indexed: 05/29/2023]
Abstract
We study the spin-dependent thermoelectric transport through a single-molecule-magnet junction in the sequential tunneling regime. It is found that the intrinsic magnetic anisotropy of the single-molecule magnet can lead to gate-voltage-dependent oscillations of charge thermopower and a large violation of the Wiedeman-Franz law. More interestingly, the spin-Seebeck coefficient is shown to be greater than the charge-Seebeck coefficient, and a pure spin thermopower or/and a pure spin current can be obtained by tuning only the gate voltage. It needs neither an external magnetic field or irradiation of circularly polarized light on the molecule nor ferromagnetic leads to realize these interesting effects, indicating the powerful prospect of single-molecule-magnet applications in spintronic devices.
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Affiliation(s)
- Rui-Qiang Wang
- Laboratory of Quantum Information Technology, ICMP and SPTE, South China Normal University, Guangzhou 510006, China
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29
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Wierzbicki M, Swirkowicz R. Enhancement of thermoelectric efficiency in a two-level molecule. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2010; 22:185302. [PMID: 21393681 DOI: 10.1088/0953-8984/22/18/185302] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Electron and energy transport through a two-level molecule (quantum dot) with intra- and inter-level Coulomb correlations is studied using the non-equilibrium Green function formalism. Thermoelectric coefficients are determined in the regime of linear transport for a wide range of gate voltages and temperature. At low temperatures Coulomb blockade effects lead to oscillations of thermal conductance which are well correlated with oscillations in electron conductance. Due to different probabilities of particular one- and two-particle configurations, the intensities of the peaks corresponding to resonant states are different, which results in the selection of channels active in the transport. Additional selection can be obtained for molecules with level-dependent tunnelling rates to external electrodes. In such systems, channels with strongly reduced heat transfer can appear, which results in an enhancement of the thermal efficiency.
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Affiliation(s)
- M Wierzbicki
- Faculty of Physics, Warsaw University of Technology, ulica Koszykowa 75, 00-662 Warsaw, Poland
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30
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Prezhdo OV. Photoinduced dynamics in semiconductor quantum dots: insights from time-domain ab initio studies. Acc Chem Res 2009; 42:2005-16. [PMID: 19888715 DOI: 10.1021/ar900157s] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Nanoscale clusters of bulk materials, also known as quantum dots (QDs), exhibit both molecular and bulk properties. Unlike either bulk or molecular materials, QD properties can be modified continuously by changing QD shape and size. However, the chemical and physical properties of molecular and bulk materials often contradict each other, which can lead to differing viewpoints about the behavior of QDs. For example, the molecular view suggests strong electron-hole and charge-phonon interactions, as well as slow energy relaxation due to mismatch between electronic energy gaps and phonon frequencies. In contrast, the bulk view advocates that the kinetic energy of quantum confinement is greater than electron-hole interactions, that charge-phonon coupling is weak, and that the relaxation through quasi-continuous bands is rapid. By synthesizing the bulk and molecular viewpoints, this Account clarifies the controversies and provides a unified atomistic picture of the nature and dynamics of photoexcited states in semiconductor QDs. Based on the state-of-the-art ab initio approaches in both the energy and time domains, the Account presents a comprehensive discussion of the dynamical processes in QDs, ranging from the initial photon absorption to the final emission. The atomistic description of QDs complements phenomenological models, provides important details, and creates new scientific paradigms. The ab initio approaches are particularly useful for studying geometric and electronic structure of QDs because they treat bulk, surface, ligands, and defects on equal footing and incorporate electronic correlation effects. Nonadiabatic molecular dynamics simulations most closely mimic the complex coupled evolutions of charges, phonons, and spins as they occur in nature. The simulations show that the underlying atomic structure, thermal fluctuations, and surface effects lift electronic state degeneracies predicted by phenomenological models and that excitonic electron-hole interactions are strong in small QDs. Stoichiometric surfaces self-heal. However, only molecular ligands and core/shell designs can eliminate traps associated with dangling chemical bonds, missing atoms, and other defects. Ligands create charge traps and provide high-frequency phonons. The phonon-induced dephasing of electronic excitations is ultrafast, ranging from tens to hundreds of femtoseconds. The dependence of the relaxation on the excitation energy and the density of states clarify the controversies regarding the phonon bottleneck in the photoexcited electron relaxation, and the participation of low-frequency phonons explains the temperature dependence of the relaxation rate. We rationalize the ultrafast generation of multiple excitons without the phononbottleneck by strong Coulomb interactions between the charge carriers. The QD charging and defects explain the large variation in the experimental data on multiple exciton generation. The issues raised here with the electronic states and semiconductor QDs are similar to those found with the spin states and metallic QDs. Assemblies of QDs with other materials, such as organic chromophores and inorganic semiconductors, will present new sets of questions. Time-domain ab initio approaches will allow scientists to address these challenges directly in the near future.
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Affiliation(s)
- Oleg V. Prezhdo
- Department of Chemistry, University of Washington, Seattle, Washington 98195-1700
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31
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Madrid AB, Hyeon-Deuk K, Habenicht BF, Prezhdo OV. Phonon-induced dephasing of excitons in semiconductor quantum dots: multiple exciton generation, fission, and luminescence. ACS NANO 2009; 3:2487-94. [PMID: 19722505 DOI: 10.1021/nn900584p] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Phonon-induced dephasing processes that govern optical line widths, multiple exciton (ME) generation (MEG), and ME fission (MEF) in semiconductor quantum dots (QDs) are investigated by ab initio molecular dynamics simulation. Using Si QDs as an example, we propose that MEF occurs by phonon-induced dephasing and, for the first time, estimate its time scale to be 100 fs. In contrast, luminescence and MEG dephasing times are all sub-10 fs. Generally, dephasing is faster for higher-energy and higher-order excitons and increased temperatures. MEF is slow because it is facilitated only by low-frequency acoustic modes. Luminescence and MEG couple to both acoustic and optical modes of the QD, as well as ligand vibrations. The detailed atomistic simulation of the dephasing processes advances understanding of exciton dynamics in QDs and other nanoscale materials.
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Affiliation(s)
- Angeline B Madrid
- Department of Chemistry, University of Washington, Seattle, Washington 98195, USA
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32
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Goswami S, Siegert C, Baenninger M, Pepper M, Farrer I, Ritchie DA, Ghosh A. Highly enhanced thermopower in two-dimensional electron systems at millikelvin temperatures. PHYSICAL REVIEW LETTERS 2009; 103:026602. [PMID: 19659228 DOI: 10.1103/physrevlett.103.026602] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2009] [Indexed: 05/28/2023]
Abstract
We report experimental observation of an unexpectedly large thermopower in mesoscopic two-dimensional (2D) electron systems in GaAs/AlGaAs heterostructures at sub-Kelvin temperatures and zero magnetic field. Unlike conventional nonmagnetic high-mobility 2D systems, the thermopower in our devices increases with decreasing temperature below 0.3 K, reaching values in excess of 100 microV/K, thus exceeding the free electron estimate by more than 2 orders of magnitude. With support from a parallel study of the local density of states, we suggest such a phenomenon to be linked to intrinsic localized states and many-body spin correlations in the system.
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Affiliation(s)
- Srijit Goswami
- Cavendish Laboratory, University of Cambridge, J.J. Thomson Avenue, Cambridge CB3 0HE, United Kingdom.
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33
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Prance JR, Smith CG, Griffiths JP, Chorley SJ, Anderson D, Jones GAC, Farrer I, Ritchie DA. Electronic refrigeration of a two-dimensional electron gas. PHYSICAL REVIEW LETTERS 2009; 102:146602. [PMID: 19392464 DOI: 10.1103/physrevlett.102.146602] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2008] [Indexed: 05/27/2023]
Abstract
Measurements are presented of a device designed to cool a 6 microm;{2} region of 2D electron gas using quantum dots. Electrostatic effects are found to be significant in the device, and a model that accounts for them is developed. At ambient electron temperatures above 120 mK the results are consistent with the model and the base temperature of the cooled region is estimated. At an ambient electron temperature of 280 mK, the 6 microm;{2} region is found to be cooled below 190 mK. Below 120 mK the results deviate from predictions, which is attributed to reduced electron-electron scattering rates.
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Affiliation(s)
- J R Prance
- Cavendish Laboratory, J. J. Thomson Avenue, Cambridge CB3 0HE, United Kingdom.
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34
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Hyeon-Deuk K, Madrid AB, Prezhdo OV. Symmetric band structures and asymmetric ultrafast electron and hole relaxations in silicon and germanium quantum dots: time-domain ab initio simulation. Dalton Trans 2009:10069-77. [DOI: 10.1039/b909267f] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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35
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Prezhdo OV. Multiple excitons and the electron–phonon bottleneck in semiconductor quantum dots: An ab initio perspective. Chem Phys Lett 2008. [DOI: 10.1016/j.cplett.2008.03.099] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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36
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Kubala B, König J, Pekola J. Violation of the Wiedemann-Franz law in a single-electron transistor. PHYSICAL REVIEW LETTERS 2008; 100:066801. [PMID: 18352503 DOI: 10.1103/physrevlett.100.066801] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/26/2007] [Indexed: 05/26/2023]
Abstract
We study the influence of Coulomb interaction on the thermoelectric transport coefficients for a metallic single-electron transistor. By performing a perturbation expansion up to second order in the tunnel-barrier conductance, we include sequential and cotunneling processes as well as quantum fluctuations that renormalize the charging energy and the tunnel conductance. We find that Coulomb interaction leads to a strong violation of the Wiedemann-Franz law: the Lorenz ratio becomes gate-voltage dependent for sequential tunneling, and is increased by a factor 9/5 in the cotunneling regime. Finally, we suggest a measurement scheme for an experimental realization.
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Affiliation(s)
- Björn Kubala
- Institut für Theoretische Physik III, Ruhr-Universität Bochum, 44780 Bochum, Germany
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37
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Kilin DS, Tsemekhman K, Prezhdo OV, Zenkevich EI, von Borczyskowski C. Ab initio study of exciton transfer dynamics from a core–shell semiconductor quantum dot to a porphyrin-sensitizer. J Photochem Photobiol A Chem 2007. [DOI: 10.1016/j.jphotochem.2007.02.017] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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