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Garate I, Affleck I. Kondo temperature in multilevel quantum dots. PHYSICAL REVIEW LETTERS 2011; 106:156803. [PMID: 21568594 DOI: 10.1103/physrevlett.106.156803] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2010] [Indexed: 05/30/2023]
Abstract
We develop a general method to evaluate the Kondo temperature in a multilevel quantum dot that is weakly coupled to conducting leads. Our theory reveals that the Kondo temperature is strongly enhanced when the intradot energy-level spacing is comparable or smaller than the charging energy. We propose an experiment to test our result, which consists of measuring the size dependence of the Kondo temperature.
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Affiliation(s)
- Ion Garate
- Department of Physics and Astronomy, The University of British Columbia, Vancouver, BC V6T 1Z1, Canada
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Lansbergen GP, Tettamanzi GC, Verduijn J, Collaert N, Biesemans S, Blaauboer M, Rogge S. Tunable Kondo effect in a single donor atom. NANO LETTERS 2010; 10:455-460. [PMID: 20041698 DOI: 10.1021/nl9031132] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The Kondo effect has been observed in a single gate-tunable atom. The measurement device consists of a single As dopant incorporated in a silicon nanostructure. The atomic orbitals of the dopant are tunable by the gate electric field. When they are tuned such that the ground state of the atomic system becomes a (nearly) degenerate superposition of two of the silicon valleys, an exotic and hitherto unobserved valley Kondo effect appears. Together with the "regular" spin Kondo, the tunable valley Kondo effect allows for reversible electrical control over the symmetry of the Kondo ground state from an SU(2) to an SU(4) configuration.
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Affiliation(s)
- G P Lansbergen
- Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands.
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Vidan A, Stopa M, Westervelt RM, Hanson M, Gossard AC. Multipeak Kondo effect in one- and two-electron quantum dots. PHYSICAL REVIEW LETTERS 2006; 96:156802. [PMID: 16712183 DOI: 10.1103/physrevlett.96.156802] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2005] [Indexed: 05/09/2023]
Abstract
We have fabricated a few-electron quantum dot that can be tuned down to zero electrons while maintaining strong coupling to the leads. Using a nearby quantum point contact as a charge sensor, we can determine the absolute number of electrons in the quantum dot. We find several sharp peaks in the differential conductance, occurring at both zero and finite source-drain bias, for the one- and two-electron quantum dot. We attribute the peaks at finite bias to a Kondo effect through excited states of the quantum dot and investigate the magnetic field dependence of these Kondo resonances.
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Affiliation(s)
- A Vidan
- Division of Engineering and Applied Sciences and Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
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Jarillo-Herrero P, Kong J, van der Zant HSJ, Dekker C, Kouwenhoven LP, De Franceschi S. Orbital Kondo effect in carbon nanotubes. Nature 2005; 434:484-8. [PMID: 15791250 DOI: 10.1038/nature03422] [Citation(s) in RCA: 326] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2004] [Accepted: 01/25/2005] [Indexed: 11/09/2022]
Abstract
Progress in the fabrication of nanometre-scale electronic devices is opening new opportunities to uncover deeper aspects of the Kondo effect--a characteristic phenomenon in the physics of strongly correlated electrons. Artificial single-impurity Kondo systems have been realized in various nanostructures, including semiconductor quantum dots, carbon nanotubes and individual molecules. The Kondo effect is usually regarded as a spin-related phenomenon, namely the coherent exchange of the spin between a localized state and a Fermi sea of delocalized electrons. In principle, however, the role of the spin could be replaced by other degrees of freedom, such as an orbital quantum number. Here we show that the unique electronic structure of carbon nanotubes enables the observation of a purely orbital Kondo effect. We use a magnetic field to tune spin-polarized states into orbital degeneracy and conclude that the orbital quantum number is conserved during tunnelling. When orbital and spin degeneracies are present simultaneously, we observe a strongly enhanced Kondo effect, with a multiple splitting of the Kondo resonance at finite field and predicted to obey a so-called SU4 symmetry.
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Affiliation(s)
- Pablo Jarillo-Herrero
- Kavli Institute of Nanoscience, Delft University of Technology, PO Box 5046, 2600 GA Delft, The Netherlands.
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Sim HS, Kataoka M, Yi H, Hwang NY, Choi MS, Yang SRE. Coulomb blockade and kondo effect in a quantum Hall antidot. PHYSICAL REVIEW LETTERS 2003; 91:266801. [PMID: 14754077 DOI: 10.1103/physrevlett.91.266801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2003] [Indexed: 05/24/2023]
Abstract
We propose a general capacitive model for an antidot, which has two localized edge states with different spins in the quantum Hall regime. The capacitive coupling of localized excess charges, which are generated around the antidot due to magnetic flux quantization, and their effective spin fluctuation can result in Coulomb blockade, h/(2e) Aharonov-Bohm oscillations, and the Kondo effect. The resultant conductance is in qualitative agreement with recent experimental data.
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Affiliation(s)
- H-S Sim
- School of Physics, Korea Institute for Advanced Study, 207-43 Cheongryangri-dong, Dongdaemun-gu, Seoul 130-722, Korea
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van der Wiel WG, De Franceschi S, Elzerman JM, Tarucha S, Kouwenhoven LP, Motohisa J, Nakajima F, Fukui T. Two-stage Kondo effect in a quantum dot at a high magnetic field. PHYSICAL REVIEW LETTERS 2002; 88:126803. [PMID: 11909490 DOI: 10.1103/physrevlett.88.126803] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2001] [Indexed: 05/23/2023]
Abstract
We report a strong Kondo effect (Kondo temperature approximately 4 K) at high magnetic field in a selective area growth semiconductor quantum dot. The Kondo effect is ascribed to a singlet-triplet transition in the ground state of the dot. At the transition, the low-temperature conductance approaches the unitary limit. Away from the transition, for low bias voltages and temperatures, the conductance is sharply reduced. The observed behavior is compared to predictions for a two-stage Kondo effect in quantum dots coupled to single-channel leads.
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Affiliation(s)
- W G van der Wiel
- Department of Applied Physics, DIMES, and ERATO Mesoscopic Correlation Project, Delft University of Technology, P.O. Box 5046, 2600 GA Delft, The Netherlands
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Eto M, Nazarov YV. Enhancement of kondo effect in quantum dots with an even number of electrons. PHYSICAL REVIEW LETTERS 2000; 85:1306-1309. [PMID: 10991538 DOI: 10.1103/physrevlett.85.1306] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2000] [Indexed: 05/23/2023]
Abstract
We investigate the Kondo effect in a quantum dot with almost degenerate spin-singlet and triplet states for an even number of electrons. We show that the Kondo temperature as a function of the energy difference between the states Delta reaches its maximum around Delta = 0 and decreases with increasing Delta. The Kondo effect is thus enhanced by competition between singlet and triplet states. Our results explain recent experimental findings. We evaluate the linear conductance in the perturbative regime.
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Affiliation(s)
- M Eto
- Department of Applied Physics/DIMES, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands and Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan
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Abstract
The Kondo effect--a many-body phenomenon in condensed-matter physics involving the interaction between a localized spin and free electrons--was discovered in metals containing small amounts of magnetic impurities, although it is now recognized to be of fundamental importance in a wide class of correlated electron systems. In fabricated structures, the control of single, localized spins is of technological relevance for nanoscale electronics. Experiments have already demonstrated artificial realizations of isolated magnetic impurities at metallic surfaces, nanoscale magnets, controlled transitions between two-electron singlet and triplet states, and a tunable Kondo effect in semiconductor quantum dots. Here we report an unexpected Kondo effect in a few-electron quantum dot containing singlet and triplet spin states, whose energy difference can be tuned with a magnetic field. We observe the effect for an even number of electrons, when the singlet and triplet states are degenerate. The characteristic energy scale is much larger than in the ordinary spin-1/2 case.
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Abstract
A tunable Kondo effect has been realized in small quantum dots. A dot can be switched from a Kondo system to a non-Kondo system as the number of electrons on the dot is changed from odd to even. The Kondo temperature can be tuned by means of a gate voltage as a single-particle energy state nears the Fermi energy. Measurements of the temperature and magnetic field dependence of a Coulomb-blockaded dot show good agreement with predictions of both equilibrium and nonequilibrium Kondo effects.
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Affiliation(s)
- SM Cronenwett
- S. M. Cronenwett, Department of Applied Physics and DIMES, Delft University of Technology, Post Office Box 5046, 2600 GA Delft, Netherlands, and Department of Physics, Stanford University, Stanford, CA, 94305-4060, USA. T. H. Oosterkam
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Affiliation(s)
- Takeshi Inoshita
- The author is with the Quantum Transition Project, Japan Science and Technology Corporation, 4-7-6-4F Komaba, Meguro-ku, Tokyo 153, Japan
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Chen H, Ishihara M, Li ZQ, Kawazoe Y. Magnetoconductance fluctuations in a strongly correlated disordered ring system at low temperatures. PHYSICAL REVIEW. B, CONDENSED MATTER 1996; 54:17012-17017. [PMID: 9985833 DOI: 10.1103/physrevb.54.17012] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Oguri A. Fermi-liquid analysis on a Wolff model for resonant tunneling through a single quantum level. PHYSICAL REVIEW. B, CONDENSED MATTER 1995; 52:16727-16734. [PMID: 9981076 DOI: 10.1103/physrevb.52.16727] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Oguri A, Ishii H, Saso T. Kondo resonance in tunneling phenomena through a single quantum level. PHYSICAL REVIEW. B, CONDENSED MATTER 1995; 51:4715-4718. [PMID: 9979334 DOI: 10.1103/physrevb.51.4715] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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