1
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Kamlapure A, Cornils L, Žitko R, Valentyuk M, Mozara R, Pradhan S, Fransson J, Lichtenstein AI, Wiebe J, Wiesendanger R. Correlation of Yu-Shiba-Rusinov States and Kondo Resonances in Artificial Spin Arrays on an s-Wave Superconductor. NANO LETTERS 2021; 21:6748-6755. [PMID: 34351781 PMCID: PMC8392378 DOI: 10.1021/acs.nanolett.1c00387] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/28/2021] [Revised: 07/16/2021] [Indexed: 06/13/2023]
Abstract
Mutually interacting magnetic atoms coupled to a superconductor have gained enormous interest due to their potential for the realization of topological superconductivity. Individual magnetic impurities produce states within the superconducting energy gap known as Yu-Shiba-Rusinov (YSR) states. Here, using the tip of a scanning tunneling microscope, we artificially craft spin arrays consisting of an Fe adatom interacting with an assembly of interstitial Fe atoms (IFA) on a superconducting oxygen-reconstructed Ta(100) surface and show that the magnetic interaction between the adatom and the IFA assembly can be tuned by adjusting the number of IFAs in the assembly. The YSR state experiences a characteristic crossover in its energetic position and particle-hole spectral weight asymmetry when the Kondo resonance shows spectral depletion around the Fermi energy. By the help of slave-boson mean-field theory (SBMFT) and numerical renormalization group (NRG) calculations we associate the crossover with the transition from decoupled Kondo singlets to an antiferromagnetic ground state of the Fe adatom spin and the IFA assembly effective spin.
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Affiliation(s)
- Anand Kamlapure
- Department
of Physics, University of Hamburg, Jungiusstrasse 11, D-20355 Hamburg, Germany
| | - Lasse Cornils
- Department
of Physics, University of Hamburg, Jungiusstrasse 11, D-20355 Hamburg, Germany
| | - Rok Žitko
- Jožef
Stefan Institute, Jamova 39, SI-1000 Ljubljana, Slovenia
- Faculty
of Mathematics and Physics, University of
Ljubljana, Jadranska
19, SI-1000 Ljubljana, Slovenia
| | - Maria Valentyuk
- Department
of Physics, University of Hamburg, Jungiusstrasse 11, D-20355 Hamburg, Germany
- Department
of Theoretical Physics and Applied Mathematics, Ural Federal University, 19 Mira Street, Yekaterinburg 620002, Russia
| | - Roberto Mozara
- Department
of Physics, University of Hamburg, Jungiusstrasse 11, D-20355 Hamburg, Germany
| | - Saurabh Pradhan
- Department
of Physics and Astronomy, Uppsala University, P.O. Box 516, Uppsala SE-751 21, Sweden
| | - Jonas Fransson
- Department
of Physics and Astronomy, Uppsala University, P.O. Box 516, Uppsala SE-751 21, Sweden
| | - Alexander I. Lichtenstein
- Department
of Physics, University of Hamburg, Jungiusstrasse 11, D-20355 Hamburg, Germany
- Department
of Theoretical Physics and Applied Mathematics, Ural Federal University, 19 Mira Street, Yekaterinburg 620002, Russia
| | - Jens Wiebe
- Department
of Physics, University of Hamburg, Jungiusstrasse 11, D-20355 Hamburg, Germany
| | - Roland Wiesendanger
- Department
of Physics, University of Hamburg, Jungiusstrasse 11, D-20355 Hamburg, Germany
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2
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Chan KW, Sahasrabudhe H, Huang W, Wang Y, Yang HC, Veldhorst M, Hwang JCC, Mohiyaddin FA, Hudson FE, Itoh KM, Saraiva A, Morello A, Laucht A, Rahman R, Dzurak AS. Exchange Coupling in a Linear Chain of Three Quantum-Dot Spin Qubits in Silicon. NANO LETTERS 2021; 21:1517-1522. [PMID: 33481612 DOI: 10.1021/acs.nanolett.0c04771] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Quantum gates between spin qubits can be implemented leveraging the natural Heisenberg exchange interaction between two electrons in contact with each other. This interaction is controllable by electrically tailoring the overlap between electronic wave functions in quantum dot systems, as long as they occupy neighboring dots. An alternative route is the exploration of superexchange-the coupling between remote spins mediated by a third idle electron that bridges the distance between quantum dots. We experimentally demonstrate direct exchange coupling and provide evidence for second neighbor mediated superexchange in a linear array of three single-electron spin qubits in silicon, inferred from the electron spin resonance frequency spectra. We confirm theoretically, through atomistic modeling, that the device geometry only allows for sizable direct exchange coupling for neighboring dots, while next-nearest neighbor coupling cannot stem from the vanishingly small tail of the electronic wave function of the remote dots, and is only possible if mediated.
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Affiliation(s)
- Kok Wai Chan
- School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Harshad Sahasrabudhe
- Department of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907, United States
| | - Wister Huang
- School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Yu Wang
- Department of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907, United States
| | - Henry C Yang
- School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Menno Veldhorst
- School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Jason C C Hwang
- School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Fahd A Mohiyaddin
- School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Fay E Hudson
- School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Kohei M Itoh
- School of Fundamental Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama, Kanagawa 223-8522, Japan
| | - Andre Saraiva
- School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Andrea Morello
- School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Arne Laucht
- School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Rajib Rahman
- Department of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907, United States
- School of Physics, The University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Andrew S Dzurak
- School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney, New South Wales 2052, Australia
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3
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Fu ZQ, Pan Y, Zhou JJ, Bai KK, Ma DL, Zhang Y, Qiao JB, Jiang H, Liu H, He L. Relativistic Artificial Molecules Realized by Two Coupled Graphene Quantum Dots. NANO LETTERS 2020; 20:6738-6743. [PMID: 32787177 DOI: 10.1021/acs.nanolett.0c02623] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Coupled quantum dots (QDs), usually referred to as artificial molecules, are important not only in exploring fundamental physics of coupled quantum objects but also in realizing advanced QD devices. However, previous studies have been limited to artificial molecules with nonrelativistic Fermions. Here, we show that relativistic artificial molecules can be realized when two circular graphene QDs are coupled to each other. Using scanning tunneling microscopy (STM) and spectroscopy (STS), we observe the formation of bonding and antibonding states of the relativistic artificial molecule and directly visualize these states of the two coupled graphene QDs. The formation of the relativistic molecular states strongly alters distributions of massless Dirac Fermions confined in the graphene QDs. Moreover, our experiment demonstrates that the degeneracy of different angular-momentum states in the relativistic artificial molecule can be further lifted by external magnetic fields. Then, both the bonding and antibonding states are split into two peaks.
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Affiliation(s)
- Zhong-Qiu Fu
- Center for Advanced Quantum Studies, Department of Physics, Beijing Normal University, Beijing 100875, People's Republic of China
| | - Yueting Pan
- Center for Advanced Quantum Studies, Department of Physics, Beijing Normal University, Beijing 100875, People's Republic of China
| | - Jiao-Jiao Zhou
- College of Physics, Optoelectronics and Energy and Institute for Advanced Study, Soochow University, Suzhou 215006, People's Republic of China
| | - Ke-Ke Bai
- Center for Advanced Quantum Studies, Department of Physics, Beijing Normal University, Beijing 100875, People's Republic of China
- Institute of Physics, Hebei Normal University, Shijiazhuang 050024, People's Republic of China
| | - Dong-Lin Ma
- Center for Advanced Quantum Studies, Department of Physics, Beijing Normal University, Beijing 100875, People's Republic of China
- Department of Physics, Capital Normal University, Beijing 100048, People's Republic of China
| | - Yu Zhang
- Center for Advanced Quantum Studies, Department of Physics, Beijing Normal University, Beijing 100875, People's Republic of China
| | - Jia-Bin Qiao
- Center for Advanced Quantum Studies, Department of Physics, Beijing Normal University, Beijing 100875, People's Republic of China
| | - Hua Jiang
- College of Physics, Optoelectronics and Energy and Institute for Advanced Study, Soochow University, Suzhou 215006, People's Republic of China
| | - Haiwen Liu
- Center for Advanced Quantum Studies, Department of Physics, Beijing Normal University, Beijing 100875, People's Republic of China
| | - Lin He
- Center for Advanced Quantum Studies, Department of Physics, Beijing Normal University, Beijing 100875, People's Republic of China
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4
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Edri H, Raz B, Matzliah N, Davidson N, Ozeri R. Observation of Spin-Spin Fermion-Mediated Interactions between Ultracold Bosons. PHYSICAL REVIEW LETTERS 2020; 124:163401. [PMID: 32383926 DOI: 10.1103/physrevlett.124.163401] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2019] [Accepted: 04/03/2020] [Indexed: 06/11/2023]
Abstract
Interactions in an ultracold boson-fermion mixture are often manifested by elastic collisions. In a mixture of a condensed Bose gas (BEC) and spin polarized degenerate Fermi gas (DFG), fermions can mediate spin-spin interactions between bosons, leading to an effective long-range magnetic interaction analogous to Ruderman-Kittel-Kasuya-Yosida [Phys. Rev. 96, 99 (1954); Prog. Theor. Phys. 16, 45 (1956); Phys. Rev. 106, 893 (1957)] interaction in solids. We used Ramsey spectroscopy of the hyperfine clock transition in a ^{87}Rb BEC to measure the interaction mediated by a ^{40}K DFG. By controlling the boson density we isolated the effect of mediated interactions from mean-field frequency shifts due to direct collision with fermions. We measured an increase of boson spin-spin interaction by a factor of η=1.45±0.05^{stat}±0.13^{syst} in the presence of the DFG, providing clear evidence of spin-spin fermion mediated interaction. Decoherence in our system was dominated by inhomogeneous boson density shift, which increased significantly in the presence of the DFG, again indicating mediated interactions. We also measured a frequency shift due to boson-fermion interactions in accordance with a scattering length difference of a_{bf_{2}}-a_{bf_{1}}=-5.36±0.44^{stat}±1.43^{syst}a_{0} between the clock-transition states, a first measurement beyond the low-energy elastic approximation [R. Côté, A. Dalgarno, H. Wang, and W. C. Stwalley, Phys. Rev. A 57, R4118 (1998); A. Dalgarno and M. Rudge, Proc. R. Soc. A 286, 519 (1965)] in this mixture. This interaction can be tuned with a future use of a boson-fermion Feshbach resonance. Fermion-mediated interactions can potentially give rise to interesting new magnetic phases and extend the Bose-Hubbard model when the atoms are placed in an optical lattice.
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Affiliation(s)
- Hagai Edri
- Department of Physics of Complex Systems, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Boaz Raz
- Department of Physics of Complex Systems, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Noam Matzliah
- Department of Physics of Complex Systems, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Nir Davidson
- Department of Physics of Complex Systems, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Roee Ozeri
- Department of Physics of Complex Systems, Weizmann Institute of Science, Rehovot 76100, Israel
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5
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Dai Y, Wang XF, Vasilopoulos P, Liu YS. Tunable spin-polarized transport through a side-gated double quantum dot molecular junction in the Coulomb blockade regime. APPLIED NANOSCIENCE 2019. [DOI: 10.1007/s13204-019-00981-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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6
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Datta S, Weymann I, Płomińska A, Flahaut E, Marty L, Wernsdorfer W. Detection of Spin Reversal via Kondo Correlation in Hybrid Carbon Nanotube Quantum Dots. ACS NANO 2019; 13:10029-10035. [PMID: 31449383 DOI: 10.1021/acsnano.9b02091] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
We experimentally investigate the electronic transport through a double-wall carbon nanotube filled with Fe nanoparticles. At very low temperatures, the Kondo effect is observed between the confined electrons in the nanotube quantum dot and the delocalized electrons in the leads connecting the nanotube. We demonstrate that the presence of magnetic nanoparticles in the inner core of the nanotube results in a hysteretic behavior of the differential resistance of the system when the magnetic field is varied. This behavior is observed in the Kondo diamonds of the stability diagram, and the magnitude of hysteresis varies with the strength of the Kondo correlations in different diamonds. Our findings are corroborated with accurate numerical renormalization group calculations performed for an effective low-energy model involving fluctuations of the spin on the orbital level of the nanotube due to spin flips of the nanoparticles.
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Affiliation(s)
- Subhadeep Datta
- School of Physical Sciences , Indian Association for the Cultivation of Science , 2A & B Raja S. C. Mullick Road , Jadavpur, Kolkata 700032 , India
- Institut Néel , CNRS & Université Joseph Fourier, BP 166, F-38042 Grenoble Cedex 9 , France
| | - Ireneusz Weymann
- Faculty of Physics , Adam Mickiewicz University , ul. Uniwersytetu Poznańskiego 2 , 61-614 Poznań , Poland
| | - Anna Płomińska
- Faculty of Physics , Adam Mickiewicz University , ul. Uniwersytetu Poznańskiego 2 , 61-614 Poznań , Poland
| | - Emmanuel Flahaut
- CIRIMAT , Université de Toulouse , CNRS, INPT, UPS, UMR CNRS-UPS-INP No 5085, Université Toulouse 3 Paul Sabatier, Bât. CIRIMAT, 118, Route de Narbonne , 31062 Toulouse Cedex 9 , France
| | - Läetitia Marty
- Institut Néel , CNRS & Université Joseph Fourier, BP 166, F-38042 Grenoble Cedex 9 , France
| | - Wolfgang Wernsdorfer
- Institut Néel , CNRS & Université Joseph Fourier, BP 166, F-38042 Grenoble Cedex 9 , France
- Physikalisches Institut and Institute of Nanotechnology , Karlsruhe Institute of Technology , Wolfgang-Gaede-Strasse 1 , 76131 Karlsruhe , Germany
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7
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Moro-Lagares M, Korytár R, Piantek M, Robles R, Lorente N, Pascual JI, Ibarra MR, Serrate D. Real space manifestations of coherent screening in atomic scale Kondo lattices. Nat Commun 2019; 10:2211. [PMID: 31101815 PMCID: PMC6525169 DOI: 10.1038/s41467-019-10103-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Accepted: 04/18/2019] [Indexed: 11/10/2022] Open
Abstract
The interaction among magnetic moments screened by conduction electrons drives quantum phase transitions between magnetically ordered and heavy-fermion ground states. Here, starting from isolated magnetic impurities in the Kondo regime, we investigate the formation of the finite size analogue of a heavy Fermi liquid. We build regularly-spaced chains of Co adatoms on a metallic surface by atomic manipulation. Scanning tunneling spectroscopy is used to obtain maps of the Kondo resonance intensity with sub-atomic resolution. For sufficiently small interatomic separation, the spatial distribution of Kondo screening does not coincide with the position of the adatoms. It also develops enhancements at both edges of the chains. Since we can rule out any other interaction between Kondo impurities, this is explained in terms of the indirect hybridization of the Kondo orbitals mediated by a coherent electron gas, the mechanism that causes the emergence of heavy quasiparticles in the thermodynamic limit.
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Affiliation(s)
- María Moro-Lagares
- Laboratorio de Microscopias Avanzadas, Instituto de Nanociencia de Aragón, University of Zaragoza, E-50018, Zaragoza, Spain.,Institute of Physics, Academy of Sciences, Prague, 16200, Czech Republic.,Regional Centre of Advanced Technologies and Materials, Faculty of Science, Department of Physical Chemistry, Palacky University, Olomouc, 78371, Czech Republic
| | - Richard Korytár
- Department of Condensed Matter Physics, Faculty of Mathematics and Physics, Charles University, 121 16, Prague 2, Czech Republic
| | - Marten Piantek
- Laboratorio de Microscopias Avanzadas, Instituto de Nanociencia de Aragón, University of Zaragoza, E-50018, Zaragoza, Spain.,Dpto.Física Materia Condensada, University of Zaragoza, E-50009, Zaragoza, Spain
| | - Roberto Robles
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, Bellaterra, 08193, Barcelona, Spain
| | - Nicolás Lorente
- Centro de Física de Materiales CFM/MPC (CSIC-UPV/EHU), 20018, Donostia-San Sebastián, Spain.,Donostia International Physics Center (DIPC), 20018, Donostia-San Sebastian, Spain
| | - Jose I Pascual
- Laboratorio de Microscopias Avanzadas, Instituto de Nanociencia de Aragón, University of Zaragoza, E-50018, Zaragoza, Spain.,CIC NanoGUNE, E-20018, Donostia-San Sebastián, Spain.,IKERBASQUE, Basque Foundation for Science, E-48011, Bilbao, Spain
| | - M Ricardo Ibarra
- Laboratorio de Microscopias Avanzadas, Instituto de Nanociencia de Aragón, University of Zaragoza, E-50018, Zaragoza, Spain.,Dpto.Física Materia Condensada, University of Zaragoza, E-50009, Zaragoza, Spain
| | - David Serrate
- Laboratorio de Microscopias Avanzadas, Instituto de Nanociencia de Aragón, University of Zaragoza, E-50018, Zaragoza, Spain. .,Dpto.Física Materia Condensada, University of Zaragoza, E-50009, Zaragoza, Spain. .,Instituto de Ciencia de Materiales de Aragón, CSIC - Universidad de Zaragoza, 50009, Zaragoza, Spain.
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8
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Malinowski FK, Martins F, Smith TB, Bartlett SD, Doherty AC, Nissen PD, Fallahi S, Gardner GC, Manfra MJ, Marcus CM, Kuemmeth F. Fast spin exchange across a multielectron mediator. Nat Commun 2019; 10:1196. [PMID: 30867427 PMCID: PMC6416330 DOI: 10.1038/s41467-019-09194-x] [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: 10/28/2018] [Accepted: 02/25/2019] [Indexed: 11/24/2022] Open
Abstract
Scalable quantum processors require tunable two-qubit gates that are fast, coherent and long-range. The Heisenberg exchange interaction offers fast and coherent couplings for spin qubits, but is intrinsically short-ranged. Here, we demonstrate that its range can be increased by employing a multielectron quantum dot as a mediator, while preserving speed and coherence of the resulting spin-spin coupling. We do this by placing a large quantum dot with 50–100 electrons between a pair of two-electron double quantum dots that can be operated and measured simultaneously. Two-spin correlations identify coherent spin-exchange processes across the multielectron quantum dot. We further show that different physical regimes of the mediated exchange interaction allow a reduced susceptibility to charge noise at sweet spots, as well as positive and negative coupling strengths up to several gigahertz. These properties make multielectron dots attractive as scalable, voltage-controlled coherent coupling elements. Controllable two-qubit interactions are necessary to build a functional quantum computer. Here the authors demonstrate fast, coherent swapping of two spin states mediated by a long, multi-electron quantum dot that could act as a tunable coupler mediating interactions between multiple qubits.
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Affiliation(s)
- Filip K Malinowski
- Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute, University of Copenhagen, 2100, Copenhagen, Denmark
| | - Frederico Martins
- Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute, University of Copenhagen, 2100, Copenhagen, Denmark
| | - Thomas B Smith
- Centre for Engineered Quantum Systems, School of Physics, The University of Sydney, Sydney, NSW, 2006, Australia
| | - Stephen D Bartlett
- Centre for Engineered Quantum Systems, School of Physics, The University of Sydney, Sydney, NSW, 2006, Australia
| | - Andrew C Doherty
- Centre for Engineered Quantum Systems, School of Physics, The University of Sydney, Sydney, NSW, 2006, Australia
| | - Peter D Nissen
- Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute, University of Copenhagen, 2100, Copenhagen, Denmark
| | - Saeed Fallahi
- Department of Physics and Astronomy, Station Q Purdue, and Birck Nanotechnology Center, Purdue University, West Lafayette, IN, 47907, USA
| | - Geoffrey C Gardner
- Department of Physics and Astronomy, Station Q Purdue, and Birck Nanotechnology Center, Purdue University, West Lafayette, IN, 47907, USA
| | - Michael J Manfra
- Department of Physics and Astronomy, Station Q Purdue, and Birck Nanotechnology Center, Purdue University, West Lafayette, IN, 47907, USA.,School of Electrical and Computer Engineering, and School of Materials Engineering, Purdue University, West Lafayette, IN, 47907, USA
| | - Charles M Marcus
- Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute, University of Copenhagen, 2100, Copenhagen, Denmark
| | - Ferdinand Kuemmeth
- Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute, University of Copenhagen, 2100, Copenhagen, Denmark.
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9
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Sierra MA, López R, Lim JS. Thermally Driven Out-of-Equilibrium Two-Impurity Kondo System. PHYSICAL REVIEW LETTERS 2018; 121:096801. [PMID: 30230870 DOI: 10.1103/physrevlett.121.096801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2018] [Indexed: 06/08/2023]
Abstract
The archetypal two-impurity Kondo problem in a serially coupled double quantum dot is investigated in the presence of a thermal bias θ. The slave-boson formulation is employed to obtain the nonlinear thermal and thermoelectrical responses. When the Kondo correlations prevail over the antiferromagnetic coupling J between dot spins, we demonstrate that the setup shows negative differential thermal conductance regions behaving as a thermal diode. In addition, we report a sign reversal of the thermoelectric current I(θ) controlled by t/Γ (t and Γ denote the interdot tunnel and reservoir-dot tunnel couplings, respectively) and θ. All these features are attributed to the fact that at large θ both Q(θ) (heat current) and I(θ) are suppressed regardless of the value of t/Γ because the double dot decouples at high thermal biases. Finally, for a finite J, we investigate how the Kondo-to-antiferromagnetic crossover is altered by θ.
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Affiliation(s)
- Miguel A Sierra
- Institut de Física Interdisciplinària i de Sistemes Complexos IFISC (CSIC-UIB), E-07122 Palma de Mallorca, Spain
| | - Rosa López
- Institut de Física Interdisciplinària i de Sistemes Complexos IFISC (CSIC-UIB), E-07122 Palma de Mallorca, Spain
| | - Jong Soo Lim
- School of Physics, Korea Institute for Advanced Study, Seoul 130-722, Korea
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10
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Nicolí G, Ferguson MS, Rössler C, Wolfertz A, Blatter G, Ihn T, Ensslin K, Reichl C, Wegscheider W, Zilberberg O. Cavity-Mediated Coherent Coupling between Distant Quantum Dots. PHYSICAL REVIEW LETTERS 2018; 120:236801. [PMID: 29932683 DOI: 10.1103/physrevlett.120.236801] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2017] [Indexed: 06/08/2023]
Abstract
Scalable architectures for quantum information technologies require one to selectively couple long-distance qubits while suppressing environmental noise and cross talk. In semiconductor materials, the coherent coupling of a single spin on a quantum dot to a cavity hosting fermionic modes offers a new solution to this technological challenge. Here, we demonstrate coherent coupling between two spatially separated quantum dots using an electronic cavity design that takes advantage of whispering-gallery modes in a two-dimensional electron gas. The cavity-mediated, long-distance coupling effectively minimizes undesirable direct cross talk between the dots and defines a scalable architecture for all-electronic semiconductor-based quantum information processing.
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Affiliation(s)
- Giorgio Nicolí
- Solid State Physics Laboratory, ETH Zürich, 8093 Zürich, Switzerland
| | | | - Clemens Rössler
- Infineon Technologies Austria, Siemensstraße 2, 9500 Villach, Austria
| | | | - Gianni Blatter
- Institute for Theoretical Physics, ETH Zürich, 8093 Zürich, Switzerland
| | - Thomas Ihn
- Solid State Physics Laboratory, ETH Zürich, 8093 Zürich, Switzerland
| | - Klaus Ensslin
- Solid State Physics Laboratory, ETH Zürich, 8093 Zürich, Switzerland
| | - Christian Reichl
- Solid State Physics Laboratory, ETH Zürich, 8093 Zürich, Switzerland
| | | | - Oded Zilberberg
- Institute for Theoretical Physics, ETH Zürich, 8093 Zürich, Switzerland
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11
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Hmar JJL. Flexible resistive switching bistable memory devices using ZnO nanoparticles embedded in polyvinyl alcohol (PVA) matrix and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS). RSC Adv 2018; 8:20423-20433. [PMID: 35541659 PMCID: PMC9080816 DOI: 10.1039/c8ra04582h] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Accepted: 05/29/2018] [Indexed: 01/06/2023] Open
Abstract
The resistive switching memory effects in metal-insulator-metal devices with aluminium (Al) as top electrode (TE) and bottom electrode (BE). A solution processed active layer consisting of zinc oxide (ZnO) nanoparticles embedded in an insulating polyvinyl alcohol (PVA) matrix and polymer poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) has been studied by using flexible polyethylene terephthalate (PET) substrates. The current–voltage (I–V) measurements of hybrid Al/ZnO–PVA/PEDOT:PSS/Al/flexible PET substrate device exhibited a non-volatile bistable resistive switching behaviour, which is attributed to the trapping, storage and transport of charges in the electronic states of the ZnO nanoparticles. The performance of hybrid device is significantly enhanced over control Al/PEDOT:PSS/Al and Al/ZnO–PVA/Al devices due the presence of PEDOT:PSS polymer. This PEDOT:PSS improves the performance of oxygen ions (holes) migration toward BE and protect back oxygen vacancies (electrons) migrate toward BE from ZnO–PVA composites which may reduces the leakage current, as a result, increased the ‘ON state/OFF state’ current ratio of 7.9 × 103 times. The fabricated hybrid device showed high ON/OFF switching current ratio larger than five orders of magnitude with low operating voltages. It is observed that, the existence of two conducting states, namely, low conductivity state (OFF state) and high conductivity state (ON state), exhibiting bistable behaviour. The state of the device was maintained even after removal of the applied bias, indicating the non-volatile memory. The observed current–time response showed good memory retention behaviour of the fabricated devices. The excellent stability and retention performances of hybrid device verify the reliability of this device and demonstrate their potential for application in non-volatile bistable memory device. The carrier transport mechanism of the bistable behaviour for the fabricated non-volatile organic bistable devices structures is described on the basis of the I–V experimental results by analyzing the effect of space charge and electronic structure. Interestingly, the device performance was not degraded and remains identical even after bending the device from 60–120° angles, which indicates high potential for flexible non-volatile bistable memory device applications. This demonstration provides a class of memory devices with the potential for future flexible electronics applications. The results clearly show that there was no detectable change in resistive switching characteristics of non-volatile bistable memory device even after bending the device at different angles, making it compatible with flexible electronics.![]()
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Affiliation(s)
- Jehova Jire L. Hmar
- Department of Physics and Astronomical Sciences
- Central University of Jammu
- India
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12
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Hou W, Wang Y, Wei J, Yan Y. Ferromagnetic Phase in Nonequilibrium Quantum Dots. Sci Rep 2017; 7:18072. [PMID: 29273713 PMCID: PMC5741769 DOI: 10.1038/s41598-017-18440-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2017] [Accepted: 12/12/2017] [Indexed: 12/03/2022] Open
Abstract
By nonperturbatively solving the nonequilibrium Anderson two-impurity model with the hierarchical equations of motion approach, we report a robust ferromagnetic (FM) phase in series-coupled double quantum dots, which can suppress the antiferromagnetic (AFM) phase and dominate the phase diagram at finite bias and detuning energy in the strongly correlated limit. The FM exchange interaction origins from the passive parallel spin arrangement caused by the Pauli exclusion principle during the electrons transport. At very low temperature, the Kondo screening of the magnetic moment in the FM phase induces some nonequilibrium Kondo effects in magnetic susceptibility, spectral functions and current. In the weakly correlated limit, the AFM phase is found still stable, therefore, a magnetic-field-free internal control of spin states can be expected through the continuous FM–AFM phase transition.
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Affiliation(s)
- WenJie Hou
- Department of Physics, Renmin University of China, Beijing, 100872, China
| | - YuanDong Wang
- Department of Physics, Renmin University of China, Beijing, 100872, China
| | - JianHua Wei
- Department of Physics, Renmin University of China, Beijing, 100872, China.
| | - YiJing Yan
- Hefei National Laboratory for Physical Sciences at the Microscale and iChEM (Collaborative Innovation Center of Chemistry for Energy Materials), University of Science and Technology of China, Hefei, Anhui, 230026, China
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13
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Otsuka T, Nakajima T, Delbecq MR, Amaha S, Yoneda J, Takeda K, Allison G, Stano P, Noiri A, Ito T, Loss D, Ludwig A, Wieck AD, Tarucha S. Higher-order spin and charge dynamics in a quantum dot-lead hybrid system. Sci Rep 2017; 7:12201. [PMID: 28939803 PMCID: PMC5610234 DOI: 10.1038/s41598-017-12217-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2017] [Accepted: 09/05/2017] [Indexed: 11/09/2022] Open
Abstract
Understanding the dynamics of open quantum systems is important and challenging in basic physics and applications for quantum devices and quantum computing. Semiconductor quantum dots offer a good platform to explore the physics of open quantum systems because we can tune parameters including the coupling to the environment or leads. Here, we apply the fast single-shot measurement techniques from spin qubit experiments to explore the spin and charge dynamics due to tunnel coupling to a lead in a quantum dot-lead hybrid system. We experimentally observe both spin and charge time evolution via first- and second-order tunneling processes, and reveal the dynamics of the spin-flip through the intermediate state. These results enable and stimulate the exploration of spin dynamics in dot-lead hybrid systems, and may offer useful resources for spin manipulation and simulation of open quantum systems.
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Affiliation(s)
- Tomohiro Otsuka
- Center for Emergent Matter Science, RIKEN, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan. .,Department of Applied Physics, University of Tokyo, Bunkyo, Tokyo, 113-8656, Japan. .,JST, PRESTO, 4-1-8 Honcho, Kawaguchi, Saitama, 332-0012, Japan.
| | - Takashi Nakajima
- Center for Emergent Matter Science, RIKEN, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan.,Department of Applied Physics, University of Tokyo, Bunkyo, Tokyo, 113-8656, Japan
| | - Matthieu R Delbecq
- Center for Emergent Matter Science, RIKEN, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan
| | - Shinichi Amaha
- Center for Emergent Matter Science, RIKEN, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan
| | - Jun Yoneda
- Center for Emergent Matter Science, RIKEN, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan.,Department of Applied Physics, University of Tokyo, Bunkyo, Tokyo, 113-8656, Japan
| | - Kenta Takeda
- Center for Emergent Matter Science, RIKEN, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan
| | - Giles Allison
- Center for Emergent Matter Science, RIKEN, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan
| | - Peter Stano
- Center for Emergent Matter Science, RIKEN, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan.,Institute of Physics, Slovak Academy of Sciences, 845 11, Bratislava, Slovakia
| | - Akito Noiri
- Center for Emergent Matter Science, RIKEN, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan.,Department of Applied Physics, University of Tokyo, Bunkyo, Tokyo, 113-8656, Japan
| | - Takumi Ito
- Center for Emergent Matter Science, RIKEN, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan.,Department of Applied Physics, University of Tokyo, Bunkyo, Tokyo, 113-8656, Japan
| | - Daniel Loss
- Center for Emergent Matter Science, RIKEN, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan.,Department of Physics, University of Basel, Klingelbergstrasse 82, 4056, Basel, Switzerland
| | - Arne Ludwig
- Angewandte Festkörperphysik, Ruhr-Universität Bochum, D-44780, Bochum, Germany
| | - Andreas D Wieck
- Angewandte Festkörperphysik, Ruhr-Universität Bochum, D-44780, Bochum, Germany
| | - Seigo Tarucha
- Center for Emergent Matter Science, RIKEN, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan. .,Department of Applied Physics, University of Tokyo, Bunkyo, Tokyo, 113-8656, Japan. .,Quantum-Phase Electronics Center, University of Tokyo, Bunkyo, Tokyo, 113-8656, Japan. .,Institute for Nano Quantum Information Electronics, University of Tokyo, 4-6-1 Komaba, Meguro, Tokyo, 153-8505, Japan.
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14
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Hou W, Wang Y, Wei J, Yan Y. Manipulation of Pauli spin blockade in double quantum dot systems. J Chem Phys 2017; 146:224304. [PMID: 29166066 DOI: 10.1063/1.4985146] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Pauli spin blockade (PSB) is a significant physical effect in double quantum dot (DQD) systems. In this paper, we start from the fundamental quantum model of the DQD with the electron-electron interaction being considered and then systematically study the PSB effect in DQD by using a recently developed nonperturbative method, the hierarchical equations of motion approach. By checking the current-voltage and nonequilibrium spectral function features, the physical picture of the PSB is explicitly elucidated. Then, various kinds of manipulation of PSBs are discussed, including gate voltage, exchange interaction, and electron spin resonance. Three main characteristics beyond low-order perturbation theory are demonstrated in detail as follows: (1) the finite leakage current in the strongly correlated limit; (2) the enhancement and lifting of PSB by exchange interaction; and (3) the ON-and-OFF switch of PSB by real-time modulation.
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Affiliation(s)
- WenJie Hou
- Department of Physics, Renmin University of China, Beijing 100872, China
| | - YuanDong Wang
- Department of Physics, Renmin University of China, Beijing 100872, China
| | - JianHua Wei
- Department of Physics, Renmin University of China, Beijing 100872, China
| | - YiJing Yan
- Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026, China
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15
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Kondo blockade due to quantum interference in single-molecule junctions. Nat Commun 2017; 8:15210. [PMID: 28492236 PMCID: PMC5437279 DOI: 10.1038/ncomms15210] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Accepted: 03/06/2017] [Indexed: 11/08/2022] Open
Abstract
Molecular electronics offers unique scientific and technological possibilities, resulting from both the nanometre scale of the devices and their reproducible chemical complexity. Two fundamental yet different effects, with no classical analogue, have been demonstrated experimentally in single-molecule junctions: quantum interference due to competing electron transport pathways, and the Kondo effect due to entanglement from strong electronic interactions. Here we unify these phenomena, showing that transport through a spin-degenerate molecule can be either enhanced or blocked by Kondo correlations, depending on molecular structure, contacting geometry and applied gate voltages. An exact framework is developed, in terms of which the quantum interference properties of interacting molecular junctions can be systematically studied and understood. We prove that an exact Kondo-mediated conductance node results from destructive interference in exchange-cotunneling. Nonstandard temperature dependences and gate-tunable conductance peaks/nodes are demonstrated for prototypical molecular junctions, illustrating the intricate interplay of quantum effects beyond the single-orbital paradigm.
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16
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Gaudenzi R, Misiorny M, Burzurí E, Wegewijs MR, van der Zant HSJ. Transport mirages in single-molecule devices. J Chem Phys 2017. [DOI: 10.1063/1.4975767] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Affiliation(s)
- R. Gaudenzi
- Kavli Institute of Nanoscience, Delft University of Technology, 2600 GA Delft, The Netherlands
| | - M. Misiorny
- Department of Microtechnology and Nanoscience MC2, Chalmers University of Technology, 412 96 Göteborg, Sweden
- Faculty of Physics, Adam Mickiewicz University, 61-614 Poznań, Poland
| | - E. Burzurí
- Kavli Institute of Nanoscience, Delft University of Technology, 2600 GA Delft, The Netherlands
| | - M. R. Wegewijs
- Peter Grünberg Institut, Forschungszentrum Jülich, 52425 Jülich, Germany
- JARA-FIT, 52056 Aachen, Germany
- Institute for Theory of Statistical Physics, RWTH Aachen, 52056 Aachen, Germany
| | - H. S. J. van der Zant
- Kavli Institute of Nanoscience, Delft University of Technology, 2600 GA Delft, The Netherlands
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17
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Pan L, Wang Y, Li Z, Wei J, Yan Y. Kondo effect in double quantum dots with ferromagnetic RKKY interaction. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:025601. [PMID: 27841994 DOI: 10.1088/0953-8984/29/2/025601] [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
We study Kondo effect in parallel-coupled double quantum dots with ferromagnetic Ruderman-Kittel-Kasuya-Yoshida (RKKY) interaction, by using the exact and nonperturbative hierarchical equations of motion approach. We construct the phase diagram in the parameter plane of the inter-dot coupling t and the ferromagnetic exchange interaction J (J - 4t 2/U plane). Three different ground states, the Kondo singlet, spin singlet and S = 1 Kondo, are determined in the diagram. We find the ferromagnetic coupling will raise the Kondo peak in the area of finite hopping t which is called 'J-enhanced Kondo effect'. Another enhancement of the Kondo effect by t ('t-enhanced Kondo effect') at J = 0 is also presented. By checking the electron-electron interaction self-energy and magnetic susceptibility, we verify the ground state at large J is an under-screening Kondo state composed of a Fermi liquid with a residual spin 1/2, which is consistent with the 'singular Fermi liquid state' in the literature.
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Affiliation(s)
- Lei Pan
- Department of Physics, Renmin University of China, Beijing 100872, People's Republic of China. Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
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18
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Feng W, Liu Q, Lai X, Zhao A. The Kondo tip decorated by the Co atom. NANOTECHNOLOGY 2016; 27:455203. [PMID: 27713180 DOI: 10.1088/0957-4484/27/45/455203] [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
The Kondo effect of single Co adatoms on Ru(0001) is detected with two different kinds of co-decorated tip (Kondo tip) by using low temperature scanning tunneling microscopy and scanning tunneling spectroscopy. We call the relatively separated two magnetic impurities in the tunneling region 'two Kondo system' to distinguish it from the 'two-impurity Kondo system'. We find that the artificially constructed Kondo tips can be generally categorized into two types of Kondo resonances, which have distinct Fano line shapes with quantum interference factor |q| ≫ 1 and |q| ∼ 1, respectively. The tunneling spectra of six constructed two Kondo systems can be well fitted by summing the two Fano resonances of the two subsystems and a linear background. More interestingly, by extracting the amplitudes of the two Fano resonances in the spectra, we find that the electron transmission of such a two Kondo system in the tunneling region is dominated by the quantum interference of the Kondo tip, which is directly related to the geometric configuration of the adsorbed Kondo atom on the tip.
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Affiliation(s)
- Wei Feng
- Science and Technology on Surface Physics and Chemistry Laboratory, Jiangyou, Sichuan 621908, People's Republic of China. Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China
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19
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Kar S, Bhattacharyya S. Classical oscillators in the control of quantum tunneling: Numerical experiments. Chem Phys 2016. [DOI: 10.1016/j.chemphys.2016.03.024] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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20
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Tsai CL, Lee TM, Liou GS. Novel solution-processable functional polyimide/ZrO2 hybrids with tunable digital memory behaviors. Polym Chem 2016. [DOI: 10.1039/c6py00841k] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The resulting PI hybrid films exhibited electrically programmable digital memory properties from DRAM, SRAM to WORM with a high ON/OFF current ratio by controlling the content of ZrO2 from 0 to 30 wt%.
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Affiliation(s)
- Chia-Liang Tsai
- Functional Polymeric Materials Laboratory
- Institute of Polymer Science and Engineering
- National Taiwan University
- Taipei 10617
| | - Tzong-Ming Lee
- Material and Chemical Research Laboratories
- Industrial Technology Research Institute
- Hsinchu 31040
| | - Guey-Sheng Liou
- Functional Polymeric Materials Laboratory
- Institute of Polymer Science and Engineering
- National Taiwan University
- Taipei 10617
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21
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Exploring the phase diagram of the two-impurity Kondo problem. Nat Commun 2015; 6:10046. [PMID: 26616044 PMCID: PMC4674668 DOI: 10.1038/ncomms10046] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2015] [Accepted: 10/29/2015] [Indexed: 12/04/2022] Open
Abstract
A system of two exchange-coupled Kondo impurities in a magnetic field gives rise to a rich phase space hosting a multitude of correlated phenomena. Magnetic atoms on surfaces probed through scanning tunnelling microscopy provide an excellent platform to investigate coupled impurities, but typical high Kondo temperatures prevent field-dependent studies from being performed, rendering large parts of the phase space inaccessible. We present a study of pairs of Co atoms on insulating Cu2N/Cu(100), which each have a Kondo temperature of only 2.6 K. The pairs are designed to have interaction strengths similar to the Kondo temperature. By applying a sufficiently strong magnetic field, we are able to access a new phase in which the two coupled impurities are simultaneously screened. Comparison of differential conductance spectra taken on the atoms to simulated curves, calculated using a third-order transport model, allows us to independently determine the degree of Kondo screening in each phase. Magnetic atoms on a surface possess diverse correlated phases under an applied magnetic field due to a balance of exchange interaction and carrier-mediated coupling. Here, the authors use scanning tunnel microscopy to explore the phase diagram of coupled Co atom pairs on the surface of Cu2N/Cu(100).
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22
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Rössler C, Oehri D, Zilberberg O, Blatter G, Karalic M, Pijnenburg J, Hofmann A, Ihn T, Ensslin K, Reichl C, Wegscheider W. Transport Spectroscopy of a Spin-Coherent Dot-Cavity System. PHYSICAL REVIEW LETTERS 2015; 115:166603. [PMID: 26550890 DOI: 10.1103/physrevlett.115.166603] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/2015] [Indexed: 06/05/2023]
Abstract
Quantum engineering requires controllable artificial systems with quantum coherence exceeding the device size and operation time. This can be achieved with geometrically confined low-dimensional electronic structures embedded within ultraclean materials, with prominent examples being artificial atoms (quantum dots) and quantum corrals (electronic cavities). Combining the two structures, we implement a mesoscopic coupled dot-cavity system in a high-mobility two-dimensional electron gas, and obtain an extended spin-singlet state in the regime of strong dot-cavity coupling. Engineering such extended quantum states presents a viable route for nonlocal spin coupling that is applicable for quantum information processing.
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Affiliation(s)
- C Rössler
- Solid State Physics Laboratory, ETH Zurich, 8093 Zurich, Switzerland
| | - D Oehri
- Solid State Physics Laboratory, ETH Zurich, 8093 Zurich, Switzerland
| | - O Zilberberg
- Solid State Physics Laboratory, ETH Zurich, 8093 Zurich, Switzerland
| | - G Blatter
- Solid State Physics Laboratory, ETH Zurich, 8093 Zurich, Switzerland
| | - M Karalic
- Solid State Physics Laboratory, ETH Zurich, 8093 Zurich, Switzerland
| | - J Pijnenburg
- Solid State Physics Laboratory, ETH Zurich, 8093 Zurich, Switzerland
| | - A Hofmann
- Solid State Physics Laboratory, ETH Zurich, 8093 Zurich, Switzerland
| | - T Ihn
- Solid State Physics Laboratory, ETH Zurich, 8093 Zurich, Switzerland
| | - K Ensslin
- Solid State Physics Laboratory, ETH Zurich, 8093 Zurich, Switzerland
| | - C Reichl
- Solid State Physics Laboratory, ETH Zurich, 8093 Zurich, Switzerland
| | - W Wegscheider
- Solid State Physics Laboratory, ETH Zurich, 8093 Zurich, Switzerland
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23
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Mechanical Flip-Chip for Ultra-High Electron Mobility Devices. Sci Rep 2015; 5:13494. [PMID: 26391400 PMCID: PMC4585730 DOI: 10.1038/srep13494] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2015] [Accepted: 07/28/2015] [Indexed: 11/08/2022] Open
Abstract
Electrostatic gates are of paramount importance for the physics of devices based on high-mobility two-dimensional electron gas (2DEG) since they allow depletion of electrons in selected areas. This field-effect gating enables the fabrication of a wide range of devices such as, for example, quantum point contacts (QPC), electron interferometers and quantum dots. To fabricate these gates, processing is usually performed on the 2DEG material, which is in many cases detrimental to its electron mobility. Here we propose an alternative process which does not require any processing of the 2DEG material other than for the ohmic contacts. This approach relies on processing a separate wafer that is then mechanically mounted on the 2DEG material in a flip-chip fashion. This technique proved successful to fabricate quantum point contacts on both GaAs/AlGaAs materials with both moderate and ultra-high electron mobility.
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24
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Prüser H, Dargel PE, Bouhassoune M, Ulbrich RG, Pruschke T, Lounis S, Wenderoth M. Interplay between the Kondo effect and the Ruderman-Kittel-Kasuya-Yosida interaction. Nat Commun 2014; 5:5417. [PMID: 25384417 DOI: 10.1038/ncomms6417] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2014] [Accepted: 09/30/2014] [Indexed: 11/09/2022] Open
Abstract
The interplay between the Ruderman-Kittel-Kasuya-Yosida interaction and the Kondo effect is expected to provide the driving force for the emergence of many phenomena in strongly correlated electron materials. Two magnetic impurities in a metal are the smallest possible system containing all these ingredients and define a bottom-up approach towards a long-term understanding of concentrated/dense systems. Here we report on the experimental and theoretical investigation of iron dimers buried below a Cu(100) surface by means of low-temperature scanning tunnelling spectroscopy combined with density functional theory and numerical renormalization group calculations. The Kondo effect, in particular the width of the Abrikosov-Suhl resonance, is strongly altered or even suppressed due to magnetic coupling between the impurities. It oscillates as a function of dimer separation revealing that it is related to indirect exchange interactions mediated by the conduction electrons.
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Affiliation(s)
- Henning Prüser
- 4. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Piet E Dargel
- Institut für Theoretische Physik, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Mohammed Bouhassoune
- Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, 52425 Jülich, Germany
| | - Rainer G Ulbrich
- 4. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Thomas Pruschke
- Institut für Theoretische Physik, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Samir Lounis
- Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, 52425 Jülich, Germany
| | - Martin Wenderoth
- 4. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
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25
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Finck ADK, Van Harlingen DJ, Mohseni PK, Jung K, Li X. Anomalous modulation of a zero-bias peak in a hybrid nanowire-superconductor device. PHYSICAL REVIEW LETTERS 2013; 110:126406. [PMID: 25166828 DOI: 10.1103/physrevlett.110.126406] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2012] [Indexed: 05/22/2023]
Abstract
We report on transport measurements of an InAs nanowire coupled to niobium nitride leads at high magnetic fields. We observe a zero-bias anomaly (ZBA) in the differential conductance of the nanowire for certain ranges of magnetic field and chemical potential. The ZBA can oscillate in width with either the magnetic field or chemical potential; it can even split and re-form. We discuss how our results relate to recent predictions of hybridizing Majorana fermions in semiconducting nanowires, while considering more mundane explanations.
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Affiliation(s)
- A D K Finck
- Department of Physics and Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | - D J Van Harlingen
- Department of Physics and Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | - P K Mohseni
- Department of Electrical and Computer Engineering, Micro and Nanotechnology Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | - K Jung
- Department of Electrical and Computer Engineering, Micro and Nanotechnology Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | - X Li
- Department of Electrical and Computer Engineering, Micro and Nanotechnology Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
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26
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Schwabe A, Gütersloh D, Potthoff M. Competition between Kondo screening and indirect magnetic exchange in a quantum box. PHYSICAL REVIEW LETTERS 2012; 109:257202. [PMID: 23368491 DOI: 10.1103/physrevlett.109.257202] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/14/2012] [Indexed: 06/01/2023]
Abstract
Nanoscale systems of metal atoms antiferromagnetically exchange coupled to several magnetic impurities are shown to exhibit an unconventional reentrant competition between Kondo screening and indirect magnetic exchange interaction. Depending on the atomic positions of the magnetic moments, the total ground-state spin deviates from predictions of standard Ruderman-Kittel-Kasuya-Yosida perturbation theory. The effect shows up on an energy scale larger than the level width induced by the coupling to the environment and is experimentally accessible by studying magnetic field dependencies.
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Affiliation(s)
- Andrej Schwabe
- Institut für Theoretische Physik, Universität Hamburg, Jungiusstraße 9, 20355 Hamburg, Germany
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27
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Chorley SJ, Galpin MR, Jayatilaka FW, Smith CG, Logan DE, Buitelaar MR. Tunable Kondo physics in a carbon nanotube double quantum dot. PHYSICAL REVIEW LETTERS 2012; 109:156804. [PMID: 23102352 DOI: 10.1103/physrevlett.109.156804] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2012] [Indexed: 06/01/2023]
Abstract
We investigate a tunable two-impurity Kondo system in a strongly correlated carbon nanotube double quantum dot, accessing the full range of charge regimes. In the regime where both dots contain an unpaired electron, the system approaches the two-impurity Kondo model. At zero magnetic field the interdot coupling disrupts the Kondo physics and a local singlet state arises, but we are able to tune the crossover to a Kondo screened phase by application of a magnetic field. All results show good agreement with a numerical renormalization group study of the device.
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Affiliation(s)
- S J Chorley
- Cavendish Laboratory, University of Cambridge, Cambridge, United Kingdom
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28
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Weimer H, Yao NY, Laumann CR, Lukin MD. Long-range quantum gates using dipolar crystals. PHYSICAL REVIEW LETTERS 2012; 108:100501. [PMID: 22463396 DOI: 10.1103/physrevlett.108.100501] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2011] [Indexed: 05/31/2023]
Abstract
We propose the use of dipolar spin chains to enable long-range quantum logic between distant qubits. In our approach, an effective interaction between remote qubits is achieved by adiabatically following the ground state of the dipolar chain across the paramagnet to crystal phase transition. We demonstrate that the proposed quantum gate is particularly robust against disorder and derive scaling relations, showing that high-fidelity qubit coupling is possible in the presence of realistic imperfections. Possible experimental implementations in systems ranging from ultracold Rydberg atoms to arrays of nitrogen vacancy defect centers in diamond are discussed.
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Affiliation(s)
- Hendrik Weimer
- Physics Department, Harvard University, 17 Oxford Street, Cambridge, Massachusetts 02138, USA.
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29
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Zitko R, Mravlje J, Haule K. Ground state of the parallel double quantum dot system. PHYSICAL REVIEW LETTERS 2012; 108:066602. [PMID: 22401099 DOI: 10.1103/physrevlett.108.066602] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2011] [Indexed: 05/31/2023]
Abstract
We resolve the controversy regarding the ground state of the parallel double quantum dot system near half filling. The numerical renormalization group predicts an underscreened Kondo state with residual spin-1/2 magnetic moment, ln2 residual impurity entropy, and unitary conductance, while the Bethe ansatz solution predicts a fully screened impurity, regular Fermi-liquid ground state, and zero conductance. We calculate the impurity entropy of the system as a function of the temperature using the hybridization-expansion continuous-time quantum Monte Carlo technique, which is a numerically exact stochastic method, and find excellent agreement with the numerical renormalization group results. We show that the origin of the unconventional behavior in this model is the odd-symmetry "dark state" on the dots.
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Affiliation(s)
- Rok Zitko
- Jožef Stefan Institute, Ljubljana, Slovenia
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30
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Eichler A, Weiss M, Schönenberger C. Gate-tunable split Kondo effect in a carbon nanotube quantum dot. NANOTECHNOLOGY 2011; 22:265204. [PMID: 21576773 DOI: 10.1088/0957-4484/22/26/265204] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We show a detailed investigation of the split Kondo effect in a carbon nanotube quantum dot with multiple gate electrodes. Two conductance peaks, observed at finite bias in nonlinear transport measurements, are found to approach each other for increasing magnetic field, to result in a recovered zero bias Kondo resonance at finite magnetic field. Surprisingly, in the same charge state, but under different gate configurations, the splitting does not disappear for any value of the magnetic field, but we observe an avoided crossing. We think that our observations can be understood in terms of a two-impurity Kondo effect with two spins coupled antiferromagnetically. The exchange coupling between the two spins can be influenced by a local gate, and the non-recovery of the Kondo resonance for certain gate configurations is explained by the existence of a small antisymmetric contribution to the exchange interaction between the two spins.
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Affiliation(s)
- A Eichler
- Department of Physics, University of Basel, Basel, Switzerland
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31
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Florens S, Freyn A, Roch N, Wernsdorfer W, Balestro F, Roura-Bas P, Aligia AA. Universal transport signatures in two-electron molecular quantum dots: gate-tunable Hund's rule, underscreened Kondo effect and quantum phase transitions. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2011; 23:243202. [PMID: 21625035 DOI: 10.1088/0953-8984/23/24/243202] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We review here some universal aspects of the physics of two-electron molecular transistors in the absence of strong spin-orbit effects. Several recent quantum dot experiments have shown that an electrostatic backgate could be used to control the energy dispersion of magnetic levels. We discuss how the generally asymmetric coupling of the metallic contacts to two different molecular orbitals can indeed lead to a gate-tunable Hund's rule in the presence of singlet and triplet states in the quantum dot. For gate voltages such that the singlet constitutes the (non-magnetic) ground state, one generally observes a suppression of low voltage transport, which can yet be restored in the form of enhanced cotunneling features at finite bias. More interestingly, when the gate voltage is controlled to obtain the triplet configuration, spin S = 1 Kondo anomalies appear at zero bias, with non-Fermi liquid features related to the underscreening of a spin larger than 1/2. Finally, the small bare singlet-triplet splitting in our device allows fine-tuning with the gate between these two magnetic configurations, leading to an unscreening quantum phase transition. This transition occurs between the non-magnetic singlet phase, where a two-stage Kondo effect occurs, and the triplet phase, where the partially compensated (underscreened) moment is akin to a magnetically 'ordered' state. These observations are put theoretically into a consistent global picture by using new numerical renormalization group simulations, tailored to capture sharp finite-voltage cotunneling features within the Coulomb diamonds, together with complementary out-of-equilibrium diagrammatic calculations on the two-orbital Anderson model. This work should shed further light on the complicated puzzle still raised by multi-orbital extensions of the classic Kondo problem.
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Affiliation(s)
- Serge Florens
- Institut Néel, CNRS et Université Joseph Fourier, BP 166, Grenoble, France
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32
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Zitko R, Lee M, López R, Aguado R, Choi MS. Josephson current in strongly correlated double quantum dots. PHYSICAL REVIEW LETTERS 2010; 105:116803. [PMID: 20867595 DOI: 10.1103/physrevlett.105.116803] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2010] [Indexed: 05/29/2023]
Abstract
We study the Josephson current through a serial double quantum dot and the associated 0-π transitions which result from the subtle interplay between the superconductivity, the Kondo physics, and the interdot superexchange interaction. The competition between them is examined by tuning the relative strength Δ/T(K) of the superconducting gap and the Kondo temperature, for different strengths of the superexchange coupling determined by the interdot tunneling t relative to the level broadening Γ. We find strong renormalization of t, a significant role of the superexchange coupling J, and a rich phase diagram of the 0 and π-junction regimes. In particular, when both the superconductivity and the exchange interaction compete with the Kondo physics (Δ∼J∼T(K)), there appears an island of π' phase at large values of the superconducting phase difference.
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Affiliation(s)
- Rok Zitko
- J. Stefan Institute, Jamova 39, SI-1000 Ljubljana, Slovenia
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33
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Abstract
Molecular electronic devices currently serve as a platform for studying a variety of physical phenomena only accessible at the nanometer scale. One such phenomenon is the highly correlated electronic state responsible for the Kondo effect, manifested here as a "Kondo resonance" in the conductance. Because the Kondo effect results from strong electron-electron interactions, it is not captured by the usual quantum chemistry approaches traditionally applied to understand chemical electron transfer. In this review, we will discuss the origins and phenomenology of Kondo resonances observed in single-molecule devices, focusing primarily on the spin-1/2 Kondo state arising from a single unpaired electron. We explore the rich physical system of a single-molecule device, which offers a unique spectroscopic tool for investigating the interplay of emergent Kondo behavior and such properties as molecular orbital transitions and vibrational modes. We will additionally address more exotic systems, such as higher spin states in the Kondo regime, and we will review recent experimental advances in the ability to manipulate and exert control over these nanoscale devices.
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Affiliation(s)
- Gavin David Scott
- Department of Physics and Astronomy, Rice University, Houston, TX 77005, USA.
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34
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Chen J, Chan YH, Yang T, Wark SE, Son DH, Batteas JD. Spatially Selective Optical Tuning of Quantum Dot Thin Film Luminescence. J Am Chem Soc 2009; 131:18204-5. [DOI: 10.1021/ja906837s] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Jixin Chen
- Department of Chemistry, Texas A&M University, P.O. Box 30012, College Station, Texas 77842-3012
| | - Yang-Hsiang Chan
- Department of Chemistry, Texas A&M University, P.O. Box 30012, College Station, Texas 77842-3012
| | - Tinglu Yang
- Department of Chemistry, Texas A&M University, P.O. Box 30012, College Station, Texas 77842-3012
| | - Stacey E. Wark
- Department of Chemistry, Texas A&M University, P.O. Box 30012, College Station, Texas 77842-3012
| | - Dong Hee Son
- Department of Chemistry, Texas A&M University, P.O. Box 30012, College Station, Texas 77842-3012
| | - James D. Batteas
- Department of Chemistry, Texas A&M University, P.O. Box 30012, College Station, Texas 77842-3012
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35
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Ding GH, Ye F, Dong B. Quantum phase transition and underscreened Kondo effect in electron transport through parallel double quantum dots. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2009; 21:455303. [PMID: 21694008 DOI: 10.1088/0953-8984/21/45/455303] [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
We investigate electronic transport through a parallel double quantum dot (DQD) system with strong on-site Coulomb interaction and capacitive interdot coupling. By applying the numerical renormalization group (NRG) method, the ground state of the system and the transmission probability at zero temperature have been obtained. For a system of quantum dots with degenerate energy levels and small interdot tunnel coupling, the spin correlations between the DQDs is ferromagnetic and the ground state of the system is a spin-1 triplet state. The linear conductance will reach the unitary limit (2e(2)/h) due to the underscreened Kondo effect at low temperature. As the interdot tunnel coupling increases, there is a quantum phase transition from ferromagnetic to antiferromagnetic spin correlation in DQDs and the linear conductance is strongly suppressed.
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Affiliation(s)
- Guo-Hui Ding
- Department of Physics, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
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36
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Bandyopadhyay S, Cahay M. Electron spin for classical information processing: a brief survey of spin-based logic devices, gates and circuits. NANOTECHNOLOGY 2009; 20:412001. [PMID: 19755729 DOI: 10.1088/0957-4484/20/41/412001] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
In electronics, information has been traditionally stored, processed and communicated using an electron's charge. This paradigm is increasingly turning out to be energy-inefficient, because movement of charge within an information processing device invariably causes current flow and an associated dissipation. Replacing 'charge' with the 'spin' of an electron to encode information may eliminate much of this dissipation and lead to more energy-efficient 'green electronics'. This realization has spurred significant research in spintronic devices and circuits where spin either directly acts as the physical variable for hosting information or augments the role of charge. In this review article, we discuss and elucidate some of these ideas, and highlight their strengths and weaknesses. Many of them can potentially reduce energy dissipation significantly, but unfortunately are error-prone and unreliable. Moreover, there are serious obstacles to their technological implementation that may be difficult to overcome in the near term. This review addresses three constructs: (1) single devices or binary switches that can be constituents of Boolean logic gates for digital information processing, (2) complete gates that are capable of performing specific Boolean logic operations, and (3) combinational circuits or architectures (equivalent to many gates working in unison) that are capable of performing universal computation.
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Affiliation(s)
- Supriyo Bandyopadhyay
- Department of Electrical and Computer Engineering, Virginia Commonwealth University, Richmond, VA 23284, USA.
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37
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Otte AF, Ternes M, Loth S, Lutz CP, Hirjibehedin CF, Heinrich AJ. Spin excitations of a Kondo-screened atom coupled to a second magnetic atom. PHYSICAL REVIEW LETTERS 2009; 103:107203. [PMID: 19792339 DOI: 10.1103/physrevlett.103.107203] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2009] [Indexed: 05/07/2023]
Abstract
Screening the electron spin of a magnetic atom via spin coupling to conduction electrons results in a strong resonant peak in the density of states at the Fermi energy, the Kondo resonance. We show that magnetic coupling of a Kondo atom to another unscreened magnetic atom can split the Kondo resonance into two peaks. Inelastic spin excitation spectroscopy with scanning tunneling microscopy is used to probe the Kondo effect of a Co atom, supported on a thin insulating layer on a Cu substrate, that is weakly coupled to a nearby Fe atom to form an inhomogeneous dimer. The Kondo peak is split by interaction with the non-Kondo atom, but can be reconstituted with a magnetic field of suitable magnitude and direction. Quantitative modeling shows that this magnetic field results in a spin-level degeneracy in the dimer, which enables the Kondo effect to occur.
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Affiliation(s)
- A F Otte
- IBM Research Division, Almaden Research Center, San Jose, California 95120, USA
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38
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Kashcheyevs V, Karrasch C, Hecht T, Weichselbaum A, Meden V, Schiller A. Quantum criticality perspective on the charging of narrow quantum-dot levels. PHYSICAL REVIEW LETTERS 2009; 102:136805. [PMID: 19392388 DOI: 10.1103/physrevlett.102.136805] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/14/2008] [Indexed: 05/27/2023]
Abstract
Understanding the charging of exceptionally narrow levels in quantum dots in the presence of interactions remains a challenge within mesoscopic physics. We address this fundamental question in the generic model of a narrow level capacitively coupled to a broad one. Using bosonization we show that for arbitrary capacitive coupling charging can be described by an analogy to the magnetization in the anisotropic Kondo model, featuring a low-energy crossover scale that depends in a power-law fashion on the tunneling amplitude to the level. Explicit analytical expressions for the exponent are derived and confirmed by detailed numerical and functional renormalization-group calculations.
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Affiliation(s)
- V Kashcheyevs
- Faculty of Physics and Mathematics, University of Latvia, Zeļļu street 8, Riga LV-1002, Latvia
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39
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Sela E, Affleck I. Nonequilibrium transport through double quantum dots: exact results near a quantum critical point. PHYSICAL REVIEW LETTERS 2009; 102:047201. [PMID: 19257469 DOI: 10.1103/physrevlett.102.047201] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/24/2008] [Indexed: 05/27/2023]
Abstract
While violations of the Fermi liquid paradigm for metals are of great interest in various physical systems, quantum impurity models are among the few cases where exact theoretical results are available. Double quantum dots can provide an experimental realization of the 2 impurity Kondo model which exhibits a non-Fermi-liquid quantum critical point at a special value of its parameters. We present an exact universal result for the finite temperature nonlinear conductance along the crossover from this quantum critical point to the low energy Fermi liquid phase.
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Affiliation(s)
- Eran Sela
- Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia, Canada, V6T 1Z1
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40
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Son DI, Park DH, Ie SY, Choi WK, Choi JW, Li F, Kim TW. Single active-layer structured dual-function devices using hybrid polymer-quantum dots. NANOTECHNOLOGY 2008; 19:395201. [PMID: 21832586 DOI: 10.1088/0957-4484/19/39/395201] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We demonstrate hybrid polymer-quantum dot dual-function devices with a single active-layer structure consisting of CdSe/ZnS semiconductor quantum dots dispersed with poly N-vinylcarbazole (PVK) and 1,3,5-tirs-(N-phenylbenzimidazol-2-yl) benzene (TPBi) fabricated on an indium-tin-oxide (ITO)/glass substrate by using a simple spin-coating technique. The dual-function devices are composed of light-emitting diodes (LED) on the top side and nonvolatile organic bistable memory devices (OBD) on the bottom side and can show electroluminescence (EL) along with electrical bistability concurrently. Both the functionality of LEDs and OBDs can be successfully achieved by adding an electron transport layer (ETL) TPBi to the OBD to attain an LED in which the lowest unoccupied molecular orbital (LUMO) level of TPBi is positioned at the energy level between the conduction band of CdSe/ZnS and the LiF/Al electrode. Through transmission electron microscopy (TEM) study, it is revealed that CdSe/ZnS QDs distributed on the interface of the hole transport layer (HTL) and ETL significantly take part in the electroluminescence process rather than those existing at the outer surface of the ETL.
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Affiliation(s)
- Dong-Ick Son
- Korea Institute of Science and Technology, Materials Science and Technology Research Division, Cheongryang, PO Box 131, Seoul 130-650, Korea. Department of Information Display, Division of Electronics and Computer Engineering, Hanyang University, 17 Haengdang-dong, Seongdong-gu, Seoul 133-791, Korea
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41
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Roch N, Florens S, Bouchiat V, Wernsdorfer W, Balestro F. Quantum phase transition in a single-molecule quantum dot. Nature 2008; 453:633-7. [PMID: 18509439 DOI: 10.1038/nature06930] [Citation(s) in RCA: 103] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2007] [Accepted: 03/18/2008] [Indexed: 11/09/2022]
Abstract
Quantum criticality is the intriguing possibility offered by the laws of quantum mechanics when the wave function of a many-particle physical system is forced to evolve continuously between two distinct, competing ground states. This phenomenon, often related to a zero-temperature magnetic phase transition, is believed to govern many of the fascinating properties of strongly correlated systems such as heavy-fermion compounds or high-temperature superconductors. In contrast to bulk materials with very complex electronic structures, artificial nanoscale devices could offer a new and simpler means of understanding quantum phase transitions. Here we demonstrate this possibility in a single-molecule quantum dot, where a gate voltage induces a crossing of two different types of electron spin state (singlet and triplet) at zero magnetic field. The quantum dot is operated in the Kondo regime, where the electron spin on the quantum dot is partially screened by metallic electrodes. This strong electronic coupling between the quantum dot and the metallic contacts provides the strong electron correlations necessary to observe quantum critical behaviour. The quantum magnetic phase transition between two different Kondo regimes is achieved by tuning gate voltages and is fundamentally different from previously observed Kondo transitions in semiconductor and nanotube quantum dots. Our work may offer new directions in terms of control and tunability for molecular spintronics.
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Affiliation(s)
- Nicolas Roch
- Institut Néel, CNRS and Université Joseph Fourier, BP 166, 38042 Grenoble cedex 9, France
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42
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Son DI, Kim JH, Park DH, Choi WK, Li F, Ham JH, Kim TW. Nonvolatile flexible organic bistable devices fabricated utilizing CdSe/ZnS nanoparticles embedded in a conducting poly N-vinylcarbazole polymer layer. NANOTECHNOLOGY 2008; 19:055204. [PMID: 21817602 DOI: 10.1088/0957-4484/19/05/055204] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The bistable effects of CdSe/ZnS nanoparticles embedded in a conducting poly N-vinylcarbazole (PVK) polymer layer by using flexible poly-vinylidene difluoride (PVDF) and polyethylene terephthalate (PET) substrates were investigated. Transmission electron microscopy (TEM) images revealed that CdSe/ZnS nanoparticles were formed inside the PVK polymer layer. Current-voltage (I-V) measurement on the Al/[CdSe/ZnS nanoparticles+ PVK]/ITO/PVDF and Al/[CdSe/ZnS nanoparticles+ PVK ]/ITO/PET structures at 300 K showed a nonvolatile electrical bistability behavior with a flat-band voltage shift due to the existence of the CdSe/ZnS nanoparticles, indicative of trapping, storing and emission of charges in the electronic states of the CdSe nanoparticles. A bistable behavior for the fabricated organic bistable device (OBD) structures is described on the basis of the I-V results. These results indicate that OBDs fabricated by embedding inorganic CdSe/ZnS nanoparticles in a conducting polymer matrix on flexible substrates are prospects for potential applications in flexible nonvolatile flash memory devices.
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Affiliation(s)
- Dong-Ick Son
- Korea Institute of Science and Technology, Materials Science and Technology Research Division, Cheongryang, PO Box 131, Seoul 130-650, Korea. Department of Information Display, Division of Electronics and Computer Engineering, Hanyang University, 17 Haengdang-dong, Seongdong-gu, Seoul 133-791, Korea
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43
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Konik RM. Kondo physics and exact solvability of double dots systems. PHYSICAL REVIEW LETTERS 2007; 99:076602. [PMID: 17930911 DOI: 10.1103/physrevlett.99.076602] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2006] [Indexed: 05/25/2023]
Abstract
We study two double dot systems, one with dots in parallel and one with dots in series, and argue they admit an exact solution via the Bethe ansatz. In the case of parallel dots we exploit the exact solution to extract the behavior of the linear response conductance. The linear response conductance of the parallel dot system possesses multiple Kondo effects, including a Kondo effect enhanced by a nonpertubative antiferromagnetic RKKY interaction, has conductance zeros in the mixed valence regime, and obeys a nontrivial form of the Friedel sum rule.
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Affiliation(s)
- Robert M Konik
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA
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44
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Li B, Hou JG. Characterizing and Manipulating Individual Molecules by Scanning Tunneling Microscopy. CHINESE J CHEM PHYS 2007. [DOI: 10.1088/1674-0068/20/04/468-474] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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45
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Koerting V, Wölfle P, Paaske J. Transconductance of a double quantum dot system in the Kondo regime. PHYSICAL REVIEW LETTERS 2007; 99:036807. [PMID: 17678313 DOI: 10.1103/physrevlett.99.036807] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2006] [Indexed: 05/16/2023]
Abstract
We consider a lateral double-dot system in the Coulomb blockade regime with a single spin-1/2 on each dot, mutually coupled by an antiferromagnetic exchange interaction. Each of the two dots is contacted by two leads. We demonstrate that the voltage across one of the dots will have a profound influence on the current passing through the other dot. Using poor man's scaling, we find that the Kondo effect can lead to a strong enhancement of this transconductance.
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Affiliation(s)
- V Koerting
- Institut für Theorie der Kondensierten Materie, Universität Karlsruhe, D-76128 Karlsruhe, Germany.
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46
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Friesen M, Biswas A, Hu X, Lidar D. Efficient multiqubit entanglement via a spin bus. PHYSICAL REVIEW LETTERS 2007; 98:230503. [PMID: 17677890 DOI: 10.1103/physrevlett.98.230503] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2007] [Indexed: 05/16/2023]
Abstract
We propose an experimentally feasible architecture with controllable long-range couplings built up from local exchange interactions. The scheme consists of a spin bus, with strong, always-on interactions, coupled dynamically to external qubits of the Loss and DiVincenzo type. Long-range correlations are enabled by a spectral gap occurring in a finite-size chain. The bus can also form a hub for multiqubit entangling operations. We show how multiqubit gates may be used to efficiently generate W states (an important entanglement resource). The spin bus therefore provides a route for scalable solid-state quantum computation, using currently available experimental resources.
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Affiliation(s)
- Mark Friesen
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
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47
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Wahl P, Simon P, Diekhöner L, Stepanyuk VS, Bruno P, Schneider MA, Kern K. Exchange interaction between single magnetic adatoms. PHYSICAL REVIEW LETTERS 2007; 98:056601. [PMID: 17358878 DOI: 10.1103/physrevlett.98.056601] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2006] [Indexed: 05/05/2023]
Abstract
The magnetic coupling between single Co atoms adsorbed on a copper surface is determined by probing the Kondo resonance using low-temperature scanning tunneling spectroscopy. The Kondo resonance, which is due to magnetic correlation effects between the spin of a magnetic adatom and the conduction electrons of the substrate, is modified in a characteristic way by the coupling of the neighboring adatom spins. Increasing the interatomic distance of a Cobalt dimer from 2.56 to 8.1 A we follow the oscillatory transition from ferromagnetic to antiferromagnetic coupling. Adding a third atom to the antiferromagnetically coupled dimer results in the formation of a collective correlated state.
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Affiliation(s)
- P Wahl
- Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, 70569 Stuttgart, Germany
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48
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Zitko R, Bonca J. Fermi-liquid versus non-Fermi-liquid behavior in triple quantum dots. PHYSICAL REVIEW LETTERS 2007; 98:047203. [PMID: 17358806 DOI: 10.1103/physrevlett.98.047203] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2006] [Indexed: 05/14/2023]
Abstract
We study the effect of electron hopping in triple quantum dots modeled by the three-impurity Anderson model. We determine the range of hopping parameters where the system exhibits the two-channel Kondo effect and has non-Fermi-liquid properties in a wide temperature interval. As this interval is entered from above, the conductance through the side dots increases to a half of the conductance quantum, while the conductance through the system remains small. At lower temperatures the conductance through the system increases to the unitary limit as the system crosses over to the Fermi-liquid ground state. Measuring the differential conductance in a three-terminal configuration provides an experimental probe into the NFL behavior.
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Affiliation(s)
- Rok Zitko
- J. Stefan Institute, Ljubljana, Slovenia
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49
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Simonin J. Kondo quantum dots and the novel Kondo-doublet interaction. PHYSICAL REVIEW LETTERS 2006; 97:266804. [PMID: 17280450 DOI: 10.1103/physrevlett.97.266804] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2006] [Indexed: 05/13/2023]
Abstract
We analyze the interactions between two Kondo quantum dots connected to a Rashba-active quantum wire. We find that the Kondo-doublet interaction, at an interdot distance of the order of the wire Fermi length, is over an order of magnitude greater than the RKKY interaction. The effects induced on the Kondo-doublet interaction by the wire spin-orbit coupling can be used to control the quantum dots spin-spin correlation. These results imply that the widely used assumption that the RKKY is the dominant interaction between Anderson impurities must be revised.
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Affiliation(s)
- J Simonin
- Centro Atómico Bariloche and Instituto Balseiro, 8400 S.C. de Bariloche, Río Negro, Argentina
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50
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Zaránd G, Chung CH, Simon P, Vojta M. Quantum criticality in a double-quantum-dot system. PHYSICAL REVIEW LETTERS 2006; 97:166802. [PMID: 17155422 DOI: 10.1103/physrevlett.97.166802] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2006] [Indexed: 05/12/2023]
Abstract
We discuss the realization of the quantum-critical non-Fermi-liquid state, originally discovered within the two-impurity Kondo model, in double-quantum-dot systems. Contrary to common belief, the corresponding fixed point is robust against particle-hole and various other asymmetries and is unstable only to charge transfer between the two dots. We propose an experimental setup where such charge transfer processes are suppressed, allowing a controlled approach to the quantum-critical state. We also discuss transport and scaling properties in the vicinity of the critical point.
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Affiliation(s)
- Gergely Zaránd
- Institut für Theoretische Festkörperphysik, Universität Karlsruhe, D-76128 Karlsruhe, Germany
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