1
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Rodríguez-Sota A, Saxena V, Spethmann J, Wiesendanger R, Lo Conte R, Kubetzka A, von Bergmann K. Phase Coexistence of Mn Trimer Clusters and Antiferromagnetic Mn Islands on Ir(111). ACS NANO 2024; 18:3699-3706. [PMID: 38227829 PMCID: PMC10832046 DOI: 10.1021/acsnano.3c11459] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2023] [Revised: 01/11/2024] [Accepted: 01/11/2024] [Indexed: 01/18/2024]
Abstract
Clusters supported by solid substrates are prime candidates for heterogeneous catalysis and can be prepared in various ways. While mass-selected soft-landing methods are often used for the generation of monodisperse particles, self-assembly typically leads to a range of different cluster sizes. Here we show by scanning tunneling microscopy measurements that in the initial stages of growth, Mn forms trimers on a close-packed hexagonal Ir surface, providing a route for self-organized monodisperse cluster formation on an isotropic metallic surface. For an increasing amount of Mn, first a phase with reconstructed monolayer islands is formed, until at full coverage a pseudomorphic Mn phase evolves, which is the most densely packed one of the three different observed Mn phases on Ir(111). The magnetic state of both the reconstructed islands and the pseudomorphic film is found to be the prototypical antiferromagnetic Néel state with a 120° spin rotation between all nearest neighbors in the hexagonal layer.
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Affiliation(s)
- Arturo Rodríguez-Sota
- Institute for Nanostructure and Solid
State Physics, University of Hamburg, Hamburg 20355, Germany
| | - Vishesh Saxena
- Institute for Nanostructure and Solid
State Physics, University of Hamburg, Hamburg 20355, Germany
| | - Jonas Spethmann
- Institute for Nanostructure and Solid
State Physics, University of Hamburg, Hamburg 20355, Germany
| | - Roland Wiesendanger
- Institute for Nanostructure and Solid
State Physics, University of Hamburg, Hamburg 20355, Germany
| | | | - André Kubetzka
- Institute for Nanostructure and Solid
State Physics, University of Hamburg, Hamburg 20355, Germany
| | - Kirsten von Bergmann
- Institute for Nanostructure and Solid
State Physics, University of Hamburg, Hamburg 20355, Germany
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2
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Noei N, Mozara R, Montero AM, Brinker S, Ide N, Guimarães FSM, Lichtenstein AI, Berndt R, Lounis S, Weismann A. Manipulating the Spin Orientation of Co Atoms Using Monatomic Cu Chains. NANO LETTERS 2023; 23:8988-8994. [PMID: 37782684 DOI: 10.1021/acs.nanolett.3c02532] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/04/2023]
Abstract
Harnessing the spin of single atoms is at the heart of quantum information nanotechnology based on magnetic concepts. By attaching single Co atoms to monatomic Cu chains, we demonstrate the ability to control the spin orientation by the atomic environment. Due to spin-orbit coupling (SOC), the spin is tilted by ≈58° from the surface normal toward the chain as evidenced by inelastic tunneling spectroscopy. These findings are reproduced by density functional theory calculations and have implications for Co atoms on pristine Cu(111), which are believed to be Kondo systems. Our quantum Monte Carlo calculations suggest that SOC suppresses the Kondo effect of Co atoms at chains and on the flat surface. Our work impacts the fundamental understanding of low-energy excitations in nanostructures on surfaces and demonstrates the ability to manipulate atomic-scale magnetic moments, which can have tremendous implications for quantum devices.
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Affiliation(s)
- Neda Noei
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany
| | - Roberto Mozara
- Institut für Theoretische Physik, Universität Hamburg, 20355 Hamburg, Germany
| | - Ana M Montero
- Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich & JARA, 52425 Jülich, Germany
| | - Sascha Brinker
- Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich & JARA, 52425 Jülich, Germany
| | - Niklas Ide
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany
| | - Filipe S M Guimarães
- Jülich Supercomputing Centre, Forschungszentrum Jülich and JARA, 52425 Jülich, Germany
| | | | - Richard Berndt
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany
| | - Samir Lounis
- Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich & JARA, 52425 Jülich, Germany
- Faculty of Physics, University of Duisburg-Essen and CENIDE, 47053 Duisburg, Germany
| | - Alexander Weismann
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany
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3
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Fernández J, Roura-Bas P, Aligia AA. Theory of Differential Conductance of Co on Cu(111) Including Co s and d Orbitals, and Surface and Bulk Cu States. PHYSICAL REVIEW LETTERS 2021; 126:046801. [PMID: 33576682 DOI: 10.1103/physrevlett.126.046801] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Accepted: 01/07/2021] [Indexed: 06/12/2023]
Abstract
We revisit the theory of the Kondo effect observed by a scanning-tunneling microscope (STM) for transition-metal atoms (TMAs) on noble-metal surfaces, including d and s orbitals of the TMA, surface and bulk conduction states of the metal, and their hopping to the tip of the STM. Fitting the experimentally observed STM differential conductance for Co on Cu(111) including both the Kondo feature near the Fermi energy and the resonance below the surface band, we conclude that the STM senses mainly the Co s orbital and that the Kondo antiresonance is due to interference between states with electrons in the s orbital and a localized d orbital mediated by the conduction states.
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Affiliation(s)
- J Fernández
- Centro Atómico Bariloche, Comisión Nacional de Energía Atómica, 8400 Bariloche, Argentina, Instituto Balseiro, Comisión Nacional de Energía Atómica, 8400 Bariloche, Argentina and Consejo Nacional de Investigaciones Científicas y Técnicas, 1025 CABA, Argentina
| | - P Roura-Bas
- Centro Atómico Bariloche, Comisión Nacional de Energía Atómica, 8400 Bariloche, Argentina, Instituto Balseiro, Comisión Nacional de Energía Atómica, 8400 Bariloche, Argentina and Consejo Nacional de Investigaciones Científicas y Técnicas, 1025 CABA, Argentina
| | - A A Aligia
- Centro Atómico Bariloche, Comisión Nacional de Energía Atómica, 8400 Bariloche, Argentina, Instituto Balseiro, Comisión Nacional de Energía Atómica, 8400 Bariloche, Argentina and Consejo Nacional de Investigaciones Científicas y Técnicas, 1025 CABA, Argentina
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4
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Hernández-Vázquez EE, López-Moreno S, Munoz F, Ricardo-Chavez JL, Morán-López JL. First-principles study of Mn 3 adsorbed on Au(111) and Cu(111) surfaces. RSC Adv 2021; 11:31073-31083. [PMID: 35498913 PMCID: PMC9041345 DOI: 10.1039/d1ra05714f] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2021] [Accepted: 09/09/2021] [Indexed: 11/29/2022] Open
Abstract
A theoretical study of the Mn trimer adsorbed on the noble metal surfaces Au(111) and Cu(111) is reported. The calculations were performed using first-principles methods within the density functional theory and the generalized gradient approximation in the collinear and non-collinear magnetic phases. The system was modeled by considering a surface unit cell of 25 atoms to improve the trimer's isolation on the surface. We evaluated the trimer as a linear chain and forming triangular structures. The triangular trimer can be adsorbed in two possible configurations, above an empty surface triangle site (Δ) or on a triangle with a surface atom at the center in a hexagonal structure (H). The difference is the coordination of the Mn with surface atoms. We studied the antiferromagnetic (AF), ferromagnetic (FM), and non-collinear (NC) magnetic cases. As a result, the lowest energy configuration on both metals is the AFΔ configuration, which has an isosceles triangle shape. In comparison, the NC and the FM configurations adopt an equilateral geometry. The same trend was observed for the H configurations, but they are less bonded. The results are supported by calculating the spin-polarized electronic structure and the electronic charge transfer. Finally, we computed the energy barriers that inhibit the transformation of the linear chain to a delta Mn trimer on both substrates. Adsorption energy difference of Mn trimer on Au(111) and Cu(111) surfaces as a function of the magnetic state configuration. Where, the lowest energy state is the AFΔ one.![]()
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Affiliation(s)
- E. E. Hernández-Vázquez
- Centro Nacional de Supercómputo, IPICYT, Camino a la Presa San José 2055, Col. Lomas 4a sección, San Luis Potosí, S.L.P. 78216, Mexico
| | - S. López-Moreno
- Centro Nacional de Supercómputo, IPICYT, Camino a la Presa San José 2055, Col. Lomas 4a sección, San Luis Potosí, S.L.P. 78216, Mexico
- CONACYT – División de Materiales Avanzados, IPICYT, Camino a la Presa San José 2055, Col. Lomas 4a sección, San Luis Potosí, S.L.P. 78216, Mexico
| | - F. Munoz
- Departamento de Física, Facultad de Ciencias, Universidad de Chile, Santiago, Chile
- Centro para el Desarrollo de la Nanociencia y la Nanotecnología (CEDENNA), Santiago, Chile
| | - J. L. Ricardo-Chavez
- Laboratorio Nacional de Supercómputo, Benemérita Universidad Autónoma de Puebla, Calle 4 Sur No. 104, Col. Centro, C.P. 72000, Puebla, PUE, Mexico
| | - J. L. Morán-López
- Centro Nacional de Supercómputo, IPICYT, Camino a la Presa San José 2055, Col. Lomas 4a sección, San Luis Potosí, S.L.P. 78216, Mexico
- División de Materiales Avanzados, IPICYT, Camino a la Presa San José 2055, Col. Lomas 4a sección, San Luis Potosí, S.L.P. 78216, Mexico
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5
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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: 11] [Impact Index Per Article: 2.2] [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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6
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Hermenau J, Ibañez-Azpiroz J, Hübner C, Sonntag A, Baxevanis B, Ton KT, Steinbrecher M, Khajetoorians AA, Dos Santos Dias M, Blügel S, Wiesendanger R, Lounis S, Wiebe J. A gateway towards non-collinear spin processing using three-atom magnets with strong substrate coupling. Nat Commun 2017; 8:642. [PMID: 28935897 PMCID: PMC5608713 DOI: 10.1038/s41467-017-00506-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2017] [Accepted: 07/05/2017] [Indexed: 11/09/2022] Open
Abstract
A cluster of a few magnetic atoms on the surface of a nonmagnetic substrate is one suitable realization of a bit for spin-based information technology. The prevalent approach to achieve magnetic stability is decoupling the cluster spin from substrate conduction electrons in order to suppress destabilizing spin-flips. However, this route entails less flexibility in tailoring the coupling between the bits needed for spin-processing. Here, we use a spin-resolved scanning tunneling microscope to write, read, and store spin information for hours in clusters of three atoms strongly coupled to a substrate featuring a cloud of non-collinearly polarized host atoms, a so-called non-collinear giant moment cluster. The giant moment cluster can be driven into a Kondo screened state by simply moving one of its atoms to a different site. Using the exceptional atomic tunability of the non-collinear substrate mediated Dzyaloshinskii–Moriya interaction, we propose a logical scheme for a four-state memory. Information technology based on few atom magnets requires both long spin-energy relaxation times and flexible inter-bit coupling. Here, the authors show routes to manipulate information in three-atom clusters strongly coupled to substrate electrons by exploiting Dzyaloshinskii–Moriya interactions.
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Affiliation(s)
- J Hermenau
- Department of Physics, Hamburg University, 20355, Hamburg, Germany
| | - J Ibañez-Azpiroz
- Peter Grünberg Institute and Institute for Advanced Simulation, Forschungszentrum Jülich & JARA, Jülich, 52425, Germany
| | - Chr Hübner
- Department of Physics, Hamburg University, 20355, Hamburg, Germany
| | - A Sonntag
- Department of Physics, Hamburg University, 20355, Hamburg, Germany
| | - B Baxevanis
- Leiden Institute of Physics, Leiden University, 2333, CA, Leiden, The Netherlands
| | - K T Ton
- Department of Physics, Hamburg University, 20355, Hamburg, Germany
| | - M Steinbrecher
- Department of Physics, Hamburg University, 20355, Hamburg, Germany
| | - A A Khajetoorians
- Department of Physics, Hamburg University, 20355, Hamburg, Germany.,Institute for Molecules and Materials (IMM), Radboud University, 6525, AJ, Nijmegen, The Netherlands
| | - M Dos Santos Dias
- Peter Grünberg Institute and Institute for Advanced Simulation, Forschungszentrum Jülich & JARA, Jülich, 52425, Germany
| | - S Blügel
- Peter Grünberg Institute and Institute for Advanced Simulation, Forschungszentrum Jülich & JARA, Jülich, 52425, Germany
| | - R Wiesendanger
- Department of Physics, Hamburg University, 20355, Hamburg, Germany
| | - S Lounis
- Peter Grünberg Institute and Institute for Advanced Simulation, Forschungszentrum Jülich & JARA, Jülich, 52425, Germany
| | - J Wiebe
- Department of Physics, Hamburg University, 20355, Hamburg, Germany.
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7
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Egidi F, Sun S, Goings JJ, Scalmani G, Frisch MJ, Li X. Two-Component Noncollinear Time-Dependent Spin Density Functional Theory for Excited State Calculations. J Chem Theory Comput 2017; 13:2591-2603. [DOI: 10.1021/acs.jctc.7b00104] [Citation(s) in RCA: 55] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Franco Egidi
- Department
of Chemistry, University of Washington, Seattle, Washington 98195, United States
| | - Shichao Sun
- Department
of Chemistry, University of Washington, Seattle, Washington 98195, United States
| | - Joshua J. Goings
- Department
of Chemistry, University of Washington, Seattle, Washington 98195, United States
| | - Giovanni Scalmani
- Gaussian Inc., 340 Quinnipiac
Street, Building 40, Wallingford, Connecticut 06492, United States
| | - Michael J. Frisch
- Gaussian Inc., 340 Quinnipiac
Street, Building 40, Wallingford, Connecticut 06492, United States
| | - Xiaosong Li
- Department
of Chemistry, University of Washington, Seattle, Washington 98195, United States
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8
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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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9
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Meierott S, Hotz T, Néel N, Kröger J. Asymmetry parameter of peaked Fano line shapes. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2016; 87:103901. [PMID: 27802729 DOI: 10.1063/1.4963678] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The spectroscopic line shape of electronic and vibrational excitations is ubiquitously described by a Fano profile. In the case of nearly symmetric and peaked Fano line shapes, the fit of the conventional Fano function to experimental data leads to difficulties in unambiguously extracting the asymmetry parameter, which may vary over orders of magnitude without degrading the quality of the fit. Moreover, the extracted asymmetry parameter depends on initially guessed values. Using the spectroscopic signature of the single-Co Kondo effect on Au(110) the ambiguity of the extracted asymmetry parameter is traced to the highly symmetric resonance profile combined with the inevitable scattering of experimental data. An improved parameterization of the conventional Fano function is suggested that enables the nonlinear optimization in a reduced parameter space. In addition, the presence of a global minimum in the sum of squared residuals and thus the independence of start parameters may conveniently be identified in a two-dimensional plot. An angular representation of the asymmetry parameter is suggested in order to reliably determine uncertainty margins via linear error propagation.
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Affiliation(s)
- S Meierott
- Institut für Physik, Technische Universität Ilmenau, D-98693 Ilmenau, Germany
| | - T Hotz
- Institut für Mathematik, Technische Universität Ilmenau, D-98693 Ilmenau, Germany
| | - N Néel
- Institut für Physik, Technische Universität Ilmenau, D-98693 Ilmenau, Germany
| | - J Kröger
- Institut für Physik, Technische Universität Ilmenau, D-98693 Ilmenau, Germany
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10
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Iancu V, Schouteden K, Li Z, Van Haesendonck C. Electron–phonon coupling in engineered magnetic molecules. Chem Commun (Camb) 2016; 52:11359-11362. [DOI: 10.1039/c6cc03847f] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We probe electron–phonon coupling in CoTPyP and CrTPyP synthesized magnetic molecules. Low temperatures STS reveals pronounced Kondo resonances at zero bias in both molecules and additional Kondo resonance replicas observed at higher voltages in vibrating CoTPyP molecules.
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Affiliation(s)
- Violeta Iancu
- Laboratory of Solid-State Physics and Magnetism
- KU Leuven
- BE-3001 Leuven
- Belgium
- Extreme Light Infrastructure – Nuclear Physics/Horia Hulubei National Institute for R&D in Physics and Nuclear Engineering
| | - Koen Schouteden
- Laboratory of Solid-State Physics and Magnetism
- KU Leuven
- BE-3001 Leuven
- Belgium
| | - Zhe Li
- Laboratory of Solid-State Physics and Magnetism
- KU Leuven
- BE-3001 Leuven
- Belgium
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11
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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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12
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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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13
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Koch M, Kautsch A, Lackner F, Ernst WE. One- and two-color resonant photoionization spectroscopy of chromium-doped helium nanodroplets. J Phys Chem A 2014; 118:8373-9. [PMID: 24708058 PMCID: PMC4166682 DOI: 10.1021/jp501285r] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
![]()
We investigate the photoinduced relaxation
dynamics of Cr atoms
embedded into superfluid helium nanodroplets. One- and two-color resonant
two-photon ionization (1CR2PI and 2CR2PI, respectively) are applied
to study the two strong ground state transitions z7P2,3,4° ←
a7S3 and y7P2,3,4° ← a7S3. Upon photoexcitation, Cr* atoms are ejected from the
droplet in various excited states, as well as paired with helium atoms
as Cr*–Hen exciplexes. For the
y7P2,3,4° intermediate state, comparison of the two methods reveals
that energetically lower states than previously identified are also
populated. With 1CR2PI we find that the population of ejected z5P3° states is reduced for increasing droplet size, indicating that population
is transferred preferentially to lower states during longer interaction
with the droplet. In the 2CR2PI spectra we find evidence for generation
of bare Cr atoms in their septet ground state (a7S3) and metastable quintet state (a5S2), which we attribute to a photoinduced fast excitation–relaxation
cycle mediated by the droplet. A fraction of Cr atoms in these ground
and metastable states is attached to helium atoms, as indicated by
blue wings next to bare atom spectral lines. These relaxation channels
provide new insight into the interaction of excited transition metal
atoms with helium nanodroplets.
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Affiliation(s)
- Markus Koch
- Institute of Experimental Physics, Graz University of Technology , Petersgasse 16, A-8010 Graz, Austria
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14
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Olsen J. A direct method to transform between expansions in the configuration state function and Slater determinant bases. J Chem Phys 2014; 141:034112. [DOI: 10.1063/1.4884786] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Jeppe Olsen
- Department of Chemistry, Aarhus University, Langelandsgade 140, DK-8000 Aarhus C, Denmark
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15
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Baruselli PP, Requist R, Fabrizio M, Tosatti E. Ferromagnetic Kondo effect in a triple quantum dot system. PHYSICAL REVIEW LETTERS 2013; 111:047201. [PMID: 23931401 DOI: 10.1103/physrevlett.111.047201] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2013] [Revised: 04/09/2013] [Indexed: 06/02/2023]
Abstract
A simple device of three laterally coupled quantum dots, the central one contacted by metal leads, provides a realization of the ferromagnetic Kondo model, which is characterized by interesting properties like a nonanalytic inverted zero-bias anomaly and an extreme sensitivity to a magnetic field. Tuning the gate voltages of the lateral dots allows us to study the transition from a ferromagnetic to antiferromagnetic Kondo effect, a simple case of a Berezinskii-Kosterlitz-Thouless transition. We model the device by three coupled Anderson impurities that we study by numerical renormalization group. We calculate the single-particle spectral function of the central dot, which at zero frequency is proportional to the zero-bias conductance, across the transition, both in the absence and in the presence of a magnetic field.
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16
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Mitchell AK, Jarrold TF, Galpin MR, Logan DE. Local Moment Formation and Kondo Screening in Impurity Trimers. J Phys Chem B 2013; 117:12777-86. [DOI: 10.1021/jp401936s] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Andrew K. Mitchell
- Department of Chemistry, Physical
and Theoretical Chemistry, Oxford University, South Parks Road, Oxford OX1 3QZ,
United Kingdom
| | - Thomas F. Jarrold
- Department of Chemistry, Physical
and Theoretical Chemistry, Oxford University, South Parks Road, Oxford OX1 3QZ,
United Kingdom
| | - Martin R. Galpin
- Department of Chemistry, Physical
and Theoretical Chemistry, Oxford University, South Parks Road, Oxford OX1 3QZ,
United Kingdom
| | - David E. Logan
- Department of Chemistry, Physical
and Theoretical Chemistry, Oxford University, South Parks Road, Oxford OX1 3QZ,
United Kingdom
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17
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Lukashev PV, Kim JH, Yang S, Kim JS, Chen X, Rojas G, Honolka J, Skomski R, Enders A, Sabirianov RF. Magnetic phases of cobalt atomic clusters on tungsten. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2013; 25:036003. [PMID: 23221372 DOI: 10.1088/0953-8984/25/3/036003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
First-principle calculations are employed to show that the magnetic structure of small atomic clusters of Co, formed on a crystalline W(110) surface and containing 3-12 atoms, strongly deviates from the usual stable ferromagnetism of Co in other systems. The clusters are ferri-, ferro- or non-magnetic, depending on cluster size and geometry. We determine the atomic Co moments and their relative alignment, and show that antiferromagnetic spin alignment in the Co clusters is caused by hybridization with the tungsten substrate and band filling. This is in contrast with the typical strong ferromagnetism of bulk Co alloys, and ferromagnetic coupling in Fe/W(110) clusters.
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Affiliation(s)
- Pavel V Lukashev
- Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE 68588, USA.
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18
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Yang J, Nacci C, Martínez-Blanco J, Kanisawa K, Fölsch S. Vertical manipulation of native adatoms on the InAs(111)A surface. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2012; 24:354008. [PMID: 22899165 DOI: 10.1088/0953-8984/24/35/354008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We achieved the repositioning of native In adatoms on the polar III-V semiconductor surface InAs(111)A-(2 × 2) with atomic precision in a scanning tunnelling microscope (STM) operated at 5 K. The repositioning is performed by vertical manipulation, i.e., a reversible transfer of an individual adatom between the surface and the STM tip. Surface-to-tip transfer is achieved by a stepwise vibrational excitation of the adsorbate-surface bond via inelastic electron tunnelling assisted by the tip-induced electric field. In contrast, tip-to-surface back-transfer occurs upon tip-surface point contact formation governed by short-range adhesive forces between the surface and the In atom located at the tip apex. In addition, we found that carrier transport through the point contact is not of ballistic nature but is due to electron tunnelling. The vertical manipulation scheme used here enables us to assemble nanostructures of diverse sizes and shapes with the In adatoms residing on vacancy sites of the (2 × 2)-reconstructed surface (nearest-neighbour vacancy spacing: 8.57 Å).
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Affiliation(s)
- J Yang
- Paul-Drude-Institut für Festkörperelektronik, Berlin, Germany
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19
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Katoh K, Isshiki H, Komeda T, Yamashita M. Molecular spintronics based on single-molecule magnets composed of multiple-decker phthalocyaninato terbium(III) complex. Chem Asian J 2012; 7:1154-69. [PMID: 22514153 DOI: 10.1002/asia.201100992] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2011] [Indexed: 11/10/2022]
Abstract
Unlike electronics, which is based on the freedom of the charge of an electron whose memory is volatile, spintronics is based on the freedom of the charge, spin, and orbital of an electron whose memory is non-volatile. Although in most GMR, TMR, and CMR systems, bulk or classical magnets that are composed of transition metals are used, this Focus Review considers the growing use of single-molecule magnets (SMMs) that are composed of multinuclear metal complexes and nanosized magnets, which exhibit slow magnetic-relaxation processes and quantum tunneling. Molecular spintronics, which combines spintronics and molecular electronics, is an emerging field of research. Using molecules is advantageous because their electronic and magnetic properties can be manipulated under specific conditions. Herein, recent developments in [LnPc]-based multiple-decker SMMs on surfaces for molecular spintronic devices are presented. First, we discuss the strategies for preparing single-molecular-memory devices by using SMMs. Next, we focus on the switching of the Kondo signal of [LnPc]-based multiple-decker SMMs that are adsorbed onto surfaces, their characterization by using STM and STS, and the relationship between the molecular structure, the electronic structure, and the Kondo resonance of [TbPc(2)]. Finally, the field-effect-transistor (FET) properties of surface-adsorbed [LnPc(2)] and [Ln(2)Pc(3)] cast films are reported, which is the first step towards controlling SMMs through their spins for applications in single-molecular memory and spintronics devices.
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Affiliation(s)
- Keiichi Katoh
- Department of Chemistry, Graduate School of Science, Tohoku University, Aramaki-Aza-Aoba, Aoba-Ku, Sendai 980-8578, Japan
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20
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Katoh K, Isshiki H, Komeda T, Yamashita M. Multiple-decker phthalocyaninato Tb(III) single-molecule magnets and Y(III) complexes for next generation devices. Coord Chem Rev 2011. [DOI: 10.1016/j.ccr.2011.02.024] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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21
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Karagiannis EE, Kefalidis CE, Petrakopoulou I, Tsipis CA. Density functional study of structural, electronic, and optical properties of small bimetallic ruthenium-copper clusters. J Comput Chem 2011; 32:1241-61. [PMID: 21425282 DOI: 10.1002/jcc.21705] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2010] [Revised: 09/16/2010] [Accepted: 10/06/2010] [Indexed: 12/12/2022]
Abstract
The structural, electronic, bonding, magnetic, and optical properties of bimetallic [Cu(n)Ru(m)](+/0/-) (n + m ≤ 3; n, m = 0-3) clusters were computed in the framework of the density functional theory (DFT) and time-dependent DFT (TD-DFT) using the full-range PBE0 nonlocal hybrid GGA functional combined with the Def2-QZVPP basis sets. Several low-lying states have been investigated and the stability of the ground state spinomers was estimated with respect to all possible fragmentation schemes. Molecular orbital and population analysis schemes along with computed electronic parameters illustrated the details of the bonding mechanisms in the [Cu(n Ru(m)](+/0/-) clusters. The TD-DFT computed UV-visible absorption spectra of the bimetallic clusters have been fully analyzed and assignments of all principal electronic transitions were made and interpreted in terms of contribution from specific molecular orbital excitations.
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22
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Enders A, Skomski R, Honolka J. Magnetic surface nanostructures. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2010; 22:433001. [PMID: 21403321 DOI: 10.1088/0953-8984/22/43/433001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Recent trends in the emerging field of surface-supported magnetic nanostructures are reviewed. Current strategies for nanostructure synthesis are summarized, followed by a predominantly theoretical description of magnetic phenomena in surface magnetic structures and a review of experimental research in this field. Emphasis is on Fe- or Co-based nanostructures in various low-dimensional geometries, which are studied as model systems to explore the effects of dimensionality, atomic coordination, chemical bonds, alloying and, most importantly, interactions with the supporting substrate on the magnetism. This review also includes a discussion of closely related systems, such as 3d element impurities integrated into organic networks, surface-supported Fe-based molecular magnets, Kondo systems or 4d element nanostructures that exhibit emergent magnetism, thereby bridging the traditional areas of surface science, molecular physics and nanomagnetism.
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Affiliation(s)
- A Enders
- Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE 68588, USA.
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23
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Garbounis DN, Tsipis AC, Tsipis CA. Structural, electronic, bonding, magnetic, and optical properties of bimetallic [Ru(n)Au(m)](0/+) (n + m ≤ 3) clusters. J Comput Chem 2010; 31:2836-52. [PMID: 20928847 DOI: 10.1002/jcc.21575] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The structural, electronic, bonding, magnetic, and optical properties of bimetallic [Ru(n)Au(m)](0/+) (n + m ≤ 3; n, m = 0-3) clusters were computed in the framework of the density functional theory (DFT) and time-dependent DFT (TD-DFT) using the full-range PBE0 non local hybrid GGA functional combined with the Def2-QZVPP basis sets. Several low-lying states have been investigated and the stability of the ground state spinomers was estimated with respect to all possible fragmentation schemes. Molecular orbital and population analysis schemes along with computed electronic parameters illustrated the details of the bonding mechanisms in the [Ru(n)Au(m)](0/+) clusters. The TD-DFT computed UV-visible absorption spectra of the bimetallic clusters have been fully analyzed and compared to those of pure gold and ruthenium clusters. Assignments of all principal electronic transitions are given and interpreted in terms of contribution from specific molecular orbital excitations.
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Affiliation(s)
- Dimitrios N Garbounis
- Faculty of Chemistry, Laboratory of Applied Quantum Chemistry, Aristotle University of Thessaloniki, Thessaloniki 541 24, Greece
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24
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Roura Bas P, Aligia AA. Nonequilibrium dynamics of a singlet-triplet Anderson impurity near the quantum phase transition. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2010; 22:025602. [PMID: 21386260 DOI: 10.1088/0953-8984/22/2/025602] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We study the singlet-triplet Anderson model (STAM) in which a configuration with a doublet is hybridized with another containing a singlet and a triplet, as a minimal model to describe two-level quantum dots coupled to two metallic leads in effectively a one-channel fashion. The model has a quantum phase transition which separates regions of a doublet and a singlet ground state. The limits of integer valence of the STAM (which include a model similar to the underscreened spin-1 Kondo model) are derived and used to predict the behavior of the conductance through the system on both sides of the transition, where it jumps abruptly. At a special quantum critical line, the STAM can be mapped to an infinite- U ordinary Anderson model (OAM) plus a free spin 1/2. We use this mapping to obtain the spectral densities of the STAM as a function of those of the OAM at the transition. Using the non-crossing approximation (NCA), we calculate the spectral densities and conductance through the system as a function of temperature and bias voltage, and determine the changes that take place at the quantum phase transition. The separation of the spectral density into a singlet and a triplet part allows us to shed light on the underlying physics and to explain a shoulder observed recently in the zero bias conductance as a function of temperature in transport measurements through a single fullerene molecule (Roch et al 2008 Nature 453 633). The structure with three peaks observed in nonequilibrium transport in these experiments is also explained.
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Affiliation(s)
- P Roura Bas
- Centro Atómico Constituyentes, Comisión Nacional de Energía Atómica, 1650 San Martín, Buenos Aires, Argentina.
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25
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Katoh K, Komeda T, Yamashita M. Surface morphologies, electronic structures, and Kondo effect of lanthanide(iii)-phthalocyanine molecules on Au(111) by using STM, STS and FET properties for next generation devices. Dalton Trans 2010; 39:4708-23. [DOI: 10.1039/b926121d] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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26
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Katoh K, Yoshida Y, Yamashita M, Miyasaka H, Breedlove BK, Kajiwara T, Takaishi S, Ishikawa N, Isshiki H, Zhang YF, Komeda T, Yamagishi M, Takeya J. Direct observation of lanthanide(III)-phthalocyanine molecules on Au(111) by using scanning tunneling microscopy and scanning tunneling spectroscopy and thin-film field-effect transistor properties of Tb(III)- and Dy(III)-phthalocyanine molecules. J Am Chem Soc 2009; 131:9967-76. [PMID: 19569681 DOI: 10.1021/ja902349t] [Citation(s) in RCA: 197] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The crystal structures of double-decker single molecule magnets (SMM) LnPc(2) (Ln = Tb(III) and Dy(III); Pc = phthalocyanine) and non-SMM YPc(2) were determined by using X-ray diffraction analysis. The compounds are isomorphous to each other. The compounds have metal centers (M = Tb(3+), Dy(3+), and Y(3+)) sandwiched by two Pc ligands via eight isoindole-nitrogen atoms in a square-antiprism fashion. The twist angle between the two Pc ligands is 41.4 degrees. Scanning tunneling microscopy was used to investigate the compounds adsorbed on a Au(111) surface, deposited by using the thermal evaporation in ultrahigh vacuum. Both MPc(2) with eight lobes and MPc with four lobes, which has lost one Pc ligand, were observed. In the scanning tunneling spectroscopy images of TbPc molecules at 4.8 K, a Kondo peak with a Kondo temperature (T(K)) of approximately 250 K was observed near the Fermi level (V = 0 V). On the other hand, DyPc, YPc, and MPc(2) exhibited no Kondo peak. To understand the observed Kondo effect, the energy splitting of sublevels in a crystal field should be taken into consideration. As the next step in our studies on the SMM/Kondo effect in Tb-Pc derivatives, we investigated the electronic transport properties of Ln-Pc molecules as the active layer in top- and bottom-contact thin-film organic field effect transistor devices. Tb-Pc molecule devices exhibit p-type semiconducting properties with a hole mobility (mu(H)) of approximately 10(-4) cm(2) V(-1) s(-1). Interestingly, the Dy-Pc based devices exhibited ambipolar semiconducting properties with an electron mobility (mu(e)) of approximately 10(-5) and a mu(H) of approximately 10(-4) cm(2) V(-1) s(-1). This behavior has important implications for the electronic structure of the molecules.
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Affiliation(s)
- Keiichi Katoh
- Department of Chemistry, Graduate School of Science, Tohoku University, Aramaki-Aza-Aoba, Aoba-Ku, Sendai 980-8578, Japan
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27
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Wegner D, Yamachika R, Zhang X, Wang Y, Baruah T, Pederson MR, Bartlett BM, Long JR, Crommie MF. Tuning molecule-mediated spin coupling in bottom-up-fabricated vanadium-tetracyanoethylene nanostructures. PHYSICAL REVIEW LETTERS 2009; 103:087205. [PMID: 19792757 DOI: 10.1103/physrevlett.103.087205] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2009] [Revised: 06/30/2009] [Indexed: 05/28/2023]
Abstract
We have fabricated hybrid magnetic complexes from V atoms and tetracyanoethylene ligands via atomic manipulation with a cryogenic scanning tunneling microscope. Using tunneling spectroscopy we observe spin-polarized molecular orbitals as well as Kondo behavior. For complexes having two V atoms, the Kondo behavior can be quenched for different molecular arrangements, even as the spin-polarized orbitals remain unchanged. This is explained by variable spin-spin (i.e., V-V) ferromagnetic coupling through a single tetracyanoethylene (TCNE) molecule, as supported by density functional calculations.
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Affiliation(s)
- Daniel Wegner
- Department of Physics, University of California, Berkeley, Berkeley, California 94720-7300, USA
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28
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Hafermann H, Brener S, Rubtsov AN, Katsnelson MI, Lichtenstein AI. Understanding the electronic structure and magnetism of correlated nanosystems. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2009; 21:064248. [PMID: 21715950 DOI: 10.1088/0953-8984/21/6/064248] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
In this paper we review recent developments towards a realistic description of the electronic structure and magnetism of correlated nanosystems. A new class of so-called continuous-time solvers for the quantum impurity problem is discussed, which provides a numerically exact solution without systematic errors due to imaginary time discretization. These solvers are able to handle general interactions, like the full Coulomb vertex. We further show how four-point or higher-order correlation functions of the impurity problem can be computed. This allows the calculation of dynamical susceptibilities which provide information about spin excitations. Moreover, we discuss a principally new many-body scheme recently proposed for the description of non-local correlations in strongly correlated systems. This approach provides a basis for a many-body description of extended correlated nanostructures on a substrate.
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Affiliation(s)
- H Hafermann
- I. Institute of Theoretical Physics, University of Hamburg, D-20355 Hamburg, Germany
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29
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Ternes M, Heinrich AJ, Schneider WD. Spectroscopic manifestations of the Kondo effect on single adatoms. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2009; 21:053001. [PMID: 21817287 DOI: 10.1088/0953-8984/21/5/053001] [Citation(s) in RCA: 95] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The present topical review focuses on recent advances concerning an intriguing phenomenon in condensed matter physics, the scattering of conduction electrons at the localized spin of a magnetic impurity: the Kondo effect. Spectroscopic signatures of this effect have been observed in the past by high-resolution photoemission which, however, has the drawback of averaging over a typical surface area of 1 mm(2). By combining the atomic-scale spatial resolution of the scanning tunneling microscope (STM) with an energy resolution of a few tens of µeV achievable nowadays in scanning tunneling spectroscopy (STS), and by exposing the magnetic adatom to external magnetic fields, our understanding of the interaction of a single magnetic impurity with the conduction electrons of the nonmagnetic host has been considerably deepened. New insight has emerged by taking advantage of quantum size effects in the metallic support and by decoupling the magnetic adatom from the supporting host metal, for instance by embedding it inside a molecule or by separating it by an ultrathin insulating film from the metal surface. In this way, Kondo resonances and Kondo temperatures can be tailored and manipulated by changing the local density of states of the environment. In the weak coupling limit between a Kondo impurity and a superconductor only a convolution of tip and sample DOS is observed while for strongly coupled systems midgap states appear, indicating superconducting pair breaking. Magnetic impurities with co-adsorbed hydrogen on metallic surfaces show pseudo-Kondo resonances owing to very low-energy vibrational excitations detected by inelastic tunneling spectroscopy. One of the most recent achievements in the field has been the clarification of the role of magnetic anisotropy in the Kondo effect for localized spin systems with a spin larger than S = 1/2.
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Affiliation(s)
- Markus Ternes
- IBM Almaden Research Center, 650 Harry Road, San Jose, CA, USA. Institut de Physique des Nanostructures, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
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30
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Mahan GD. Spin shift register from a one-dimensional atomic chain. PHYSICAL REVIEW LETTERS 2009; 102:016801. [PMID: 19257224 DOI: 10.1103/physrevlett.102.016801] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2008] [Indexed: 05/27/2023]
Abstract
A spin shift register is described. It is composed of a one-dimensional chain of N identical atoms which each have an electronic spin state with S=1/2. When an additional electron is conducted down the chain, it shifts the spin information by one atom. The spin shift register (SSR) can be used as a computer memory device.
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Affiliation(s)
- G D Mahan
- Department of Physics, 104 Davey Laboratory, Pennsylvania State University, University Park, Pennsylvania 16802, USA
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31
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Néel N, Kröger J, Berndt R, Wehling TO, Lichtenstein AI, Katsnelson MI. Controlling the Kondo effect in CoCu(n) clusters atom by atom. PHYSICAL REVIEW LETTERS 2008; 101:266803. [PMID: 19437660 DOI: 10.1103/physrevlett.101.266803] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Clusters containing a single magnetic impurity were investigated by scanning tunneling microscopy, spectroscopy, and ab initio electronic structure calculations. The Kondo temperature of a Co atom embedded in Cu clusters on Cu(111) exhibits a nonmonotonic variation with the cluster size. Calculations model the experimental observations and demonstrate the importance of the local and anisotropic electronic structure for correlation effects in small clusters.
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Affiliation(s)
- N Néel
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, D-24098 Kiel, Germany
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32
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Ji SH, Zhang T, Fu YS, Chen X, Ma XC, Li J, Duan WH, Jia JF, Xue QK. High-resolution scanning tunneling spectroscopy of magnetic impurity induced bound states in the superconducting gap of Pb thin films. PHYSICAL REVIEW LETTERS 2008; 100:226801. [PMID: 18643441 DOI: 10.1103/physrevlett.100.226801] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2007] [Indexed: 05/26/2023]
Abstract
Tunneling spectra for individual atoms and dimers of Mn and Cr adsorbed on superconducting Pb thin films were measured by a low temperature scanning tunneling microscope. Multiple-resonance structures within the superconducting gap on the adsorbates were resolved and interpreted as the magnetic impurity-induced bound states associated with different scattering channels. The experiment demonstrates a spectroscopic approach to characterizing the spin states of magnetic structures and exploring the competition between superconductivity and magnetism at the nanometer scale.
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Affiliation(s)
- Shuai-Hua Ji
- Department of Physics, Tsinghua University, Beijing 100084, China
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33
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Huang P, Carter EA. Ab initio explanation of tunneling line shapes for the kondo impurity state. NANO LETTERS 2008; 8:1265-1269. [PMID: 18358009 DOI: 10.1021/nl0804203] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
We report an ab initio study of the Kondo states formed from a Co adatom on Cu(111) and Cu(100). The model consists of a CoCun cluster ( n = 5-19) embedded in (111) and (100) Cu slabs. An embedding potential derived from density functional theory treats the interaction between the periodic crystal surroundings and the CoCun cluster, while strong electron correlations within CoCun are explicitly accounted for via configuration interaction (CI) methods. Analysis of the embedded CI wave function provides insight into the nature of the Kondo state, specifically into the influence of the crystal host on the Co d-electronic structure. We predict that different d-orbitals are preferentially singly occupied in Co on Cu(111) versus Cu(100) as a result of the different crystalline environment. We propose that these variations in the local d-electronic structure on Co, not accounted for in previous theories, are responsible for the drastically different Kondo resonance line shapes observed in scanning tunneling microscopy experiments on these two surfaces.
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Affiliation(s)
- Patrick Huang
- Department of Mechanical & Aerospace Engineering and Program in Applied & Computational Mathematics, Princeton University, Princeton, NJ 08544-5263, USA
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34
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Fu YS, Ji SH, Chen X, Ma XC, Wu R, Wang CC, Duan WH, Qiu XH, Sun B, Zhang P, Jia JF, Xue QK. Manipulating the Kondo resonance through quantum size effects. PHYSICAL REVIEW LETTERS 2007; 99:256601. [PMID: 18233541 DOI: 10.1103/physrevlett.99.256601] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2007] [Indexed: 05/25/2023]
Abstract
Manipulating the Kondo effect by quantum confinement has been achieved by placing magnetic molecules on silicon-supported nanostructures. The Kondo resonance of individual manganese phthalocyanine (MnPc) molecules adsorbed on the top of Pb islands was studied by scanning tunneling spectroscopy. Oscillating Kondo temperatures as a function of film thickness were observed and attributed to the formation of the thickness-dependent quantum-well states in the host Pb islands. The present approach provides a technologically feasible way for single spin manipulation by precise thickness control of thin films.
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Affiliation(s)
- Ying-Shuang Fu
- Department of Physics, Tsinghua University, Beijing 100084, China
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Gao L, Ji W, Hu YB, Cheng ZH, Deng ZT, Liu Q, Jiang N, Lin X, Guo W, Du SX, Hofer WA, Xie XC, Gao HJ. Site-specific kondo effect at ambient temperatures in iron-based molecules. PHYSICAL REVIEW LETTERS 2007; 99:106402. [PMID: 17930399 DOI: 10.1103/physrevlett.99.106402] [Citation(s) in RCA: 117] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2006] [Revised: 05/10/2007] [Indexed: 05/25/2023]
Abstract
Kondo resonances are a very precise measure of spin-polarized transport through magnetic impurities. However, the Kondo temperature, indicating the thermal range of stability of the magnetic properties, is very low. By contrast, we find for iron phthalocyanine a Kondo temperature in spectroscopic measurements which is well above room temperature. It is also shown that the signal of the resonance depends strongly on the adsorption site of the molecule on a gold surface. Experimental data are verified by extensive numerical simulations, which establish that the coupling between iron states and states of the substrate depends strongly on the adsorption configuration.
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Affiliation(s)
- L Gao
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, P.O. Box 603, Beijing 100080, China
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36
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Lagoute J, Nacci C, Fölsch S. Doping of monatomic Cu chains with single Co atoms. PHYSICAL REVIEW LETTERS 2007; 98:146804. [PMID: 17501302 DOI: 10.1103/physrevlett.98.146804] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2006] [Indexed: 05/15/2023]
Abstract
Close-packed Co-Cu chains of various length and composition were assembled from single Co and Cu atoms on Cu(111) by atom manipulation in a low-temperature scanning tunneling microscope. Local spectroscopy reveals significant electronic Co-Cu coupling leading to confined quantum states delocalized along the heteroatomic chain. Composite Co-Cu chains provide a model case in which the quantum state of an atomic-scale host structure can be tuned by the controlled incorporation of foreign atoms.
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Affiliation(s)
- Jérôme Lagoute
- Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5-7, D-10117 Berlin, Germany
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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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38
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Abstract
We used a scanning tunneling microscope to probe the interactions between spins in individual atomic-scale magnetic structures. Linear chains of 1 to 10 manganese atoms were assembled one atom at a time on a thin insulating layer, and the spin excitation spectra of these structures were measured with inelastic electron tunneling spectroscopy. We observed excitations of the coupled atomic spins that can change both the total spin and its orientation. Comparison with a model spin-interaction Hamiltonian yielded the collective spin configuration and the strength of the coupling between the atomic spins.
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Affiliation(s)
- Cyrus F Hirjibehedin
- IBM Research Division, Almaden Research Center, 650 Harry Road, San Jose, CA 95120, USA.
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Aligia AA. Effective Kondo model for a trimer on a metallic surface. PHYSICAL REVIEW LETTERS 2006; 96:096804. [PMID: 16606296 DOI: 10.1103/physrevlett.96.096804] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2005] [Indexed: 05/08/2023]
Abstract
I consider a Hubbard-Anderson model which describes localized orbitals in three different atoms hybridized both among themselves and with a continuum of extended states. Using a generalized Schrieffer-Wolf transformation, I derive an effective Kondo model for the interaction between the doublet ground state of the isolated trimer and the extended states. For an isoceles trimer with distances a, l, l between the atoms, the Kondo temperature is very small for l<a and has a maximum for finite l>a when a is small. The results agree with experiments for a Cr trimer on Au(111).
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Affiliation(s)
- A A Aligia
- Centro Atómico Bariloche and Instituto Balseiro, Comisión Nacional de Energía Atómica, 8400 Bariloche, Argentina
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Kuzmenko T, Kikoin K, Avishai Y. Magnetically tunable Kondo-Aharonov-Bohm effect in a triangular quantum dot. PHYSICAL REVIEW LETTERS 2006; 96:046601. [PMID: 16486865 DOI: 10.1103/physrevlett.96.046601] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2005] [Indexed: 05/06/2023]
Abstract
The role of discrete orbital symmetry in mesoscopic physics is manifested in a system consisting of three identical quantum dots forming an equilateral triangle. Under a perpendicular magnetic field, this system demonstrates a unique combination of Kondo and Aharonov-Bohm features due to an interplay between continuous [spin-rotation SU(2)] and discrete (permutation C3v) symmetries, as well as U(1) gauge invariance. The conductance as a function of magnetic flux displays sharp enhancement or complete suppression depending on contact setups.
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Affiliation(s)
- T Kuzmenko
- Department of Physics, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel
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41
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Ingersent K, Ludwig AWW, Affleck I. Kondo screening in a magnetically frustrated nanostructure: exact results on a stable non-fermi-liquid phase. PHYSICAL REVIEW LETTERS 2005; 95:257204. [PMID: 16384503 DOI: 10.1103/physrevlett.95.257204] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2005] [Indexed: 05/05/2023]
Abstract
Triangular symmetry stabilizes a novel non-Fermi-liquid phase in the three-impurity Kondo model with frustrating antiferromagnetic interactions between half-integer impurity spins. The phase arises without fine-tuning of couplings, and is stable against magnetic fields and particle-hole symmetry breaking. We find a conformal field theory describing this phase, verify it using the numerical renormalization group, and extract various exact, universal low-energy properties. Signatures predicted in electrical transport may be testable in scanning tunneling microscopy or quantum-dot experiments.
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Affiliation(s)
- Kevin Ingersent
- Department of Physics, University of Florida, Gainesville, Florida 32611, USA
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Ohresser P, Bulou H, Dhesi SS, Boeglin C, Lazarovits B, Gaudry E, Chado I, Faerber J, Scheurer F. Surface diffusion of Cr adatoms on Au(111) by quantum tunneling. PHYSICAL REVIEW LETTERS 2005; 95:195901. [PMID: 16383997 DOI: 10.1103/physrevlett.95.195901] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2005] [Indexed: 05/05/2023]
Abstract
The low-temperature surface diffusion of isolated Cr adatoms on Au(111) has been determined using nonperturbing x rays. Changes in the x-ray magnetic circular dichroism spectral line shape together with Monte Carlo calculations demonstrate that adatom nucleation proceeds via quantum tunneling diffusion rather than over-barrier hopping for temperatures <40K. The jump rates are shown to be as much as 35 orders of magnitude higher than that expected for thermal over-barrier hopping at 10 K.
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Affiliation(s)
- P Ohresser
- Laboratoire pour l'Utilisation du Rayonnement Electromagnétique, UMR 130 CNRS-Université Paris Sud, 91898 Orsay, France.
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Lazarovits B, Simon P, Zaránd G, Szunyogh L. Exotic Kondo effect from magnetic trimers. PHYSICAL REVIEW LETTERS 2005; 95:077202. [PMID: 16196818 DOI: 10.1103/physrevlett.95.077202] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2004] [Indexed: 05/04/2023]
Abstract
Motivated by the recent experiments of Jamneala et al. [Phys. Rev. Lett. 87, 256804 (2001)] by combining ab initio and renormalization group methods, we study the strongly correlated state of a Cr trimer deposited on gold. Internal orbital fluctuations of the trimer lead to a huge increase of T(K) compared to the single ion Kondo temperature explaining the experimental observation of a zero-bias anomaly for the trimers. The strongly correlated state seems to belong to a new yet hardly explored class of non-Fermi-liquid fixed points.
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Affiliation(s)
- B Lazarovits
- Center for Computational Materials Science, Vienna University of Technology, Austria
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Savkin VV, Rubtsov AN, Katsnelson MI, Lichtenstein AI. Correlated adatom trimer on a metal surface: a continuous-time quantum Monte Carlo study. PHYSICAL REVIEW LETTERS 2005; 94:026402. [PMID: 15698201 DOI: 10.1103/physrevlett.94.026402] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/05/2004] [Indexed: 05/24/2023]
Abstract
The problem of three interacting Kondo impurities is solved within a numerically exact continuous-time quantum Monte Carlo scheme. A suppression of the Kondo resonance by interatomic exchange interactions for different cluster geometries is investigated. It is shown that a drastic difference between the Heisenberg and Ising cases appears for antiferromagnetically coupled adatoms. The effects of magnetic frustrations in the adatom trimer are investigated, and possible connections with available experimental data are discussed.
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Affiliation(s)
- V V Savkin
- Institute of Molecules and Materials, University of Nijmegen, 6525 ED Nijmegen, The Netherlands.
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45
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Scanning tunneling microscopy single atom/molecule manipulation and its application to nanoscience and technology. ACTA ACUST UNITED AC 2005. [DOI: 10.1116/1.1990161] [Citation(s) in RCA: 136] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Affiliation(s)
- Matthias Bode
- Institute of Applied Physics and Microstructure Research Center, University of Hamburg, Jungiusstrasse 11, Hamburg 20355, Germany.
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Lee HJ, Ho W, Persson M. Spin splitting of s and p states in single atoms and magnetic coupling in dimers on a surface. PHYSICAL REVIEW LETTERS 2004; 92:186802. [PMID: 15169520 DOI: 10.1103/physrevlett.92.186802] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/25/2003] [Indexed: 05/24/2023]
Abstract
Electronic states of magnetic atoms (Mn, Fe, and Co) and artificially assembled dimers (Mn2, Fe2, and Co2) on a NiAl(110) surface were probed by scanning tunneling spectroscopy at 17 K. Resonance peaks characteristic of each adsorbed species were observed in the unoccupied density of states. Comparison of the measured spectra with calculations by density functional theory revealed spin splitting in the unoccupied states with s and p characters for the single magnetic adatoms and addimers. The magnitude of the resonance splitting for the adatoms increased with the calculated values of magnetic moments. The resonance structures for the addimers exhibited signatures of their internal magnetic coupling.
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Affiliation(s)
- H J Lee
- Department of Physics and Astronomy, University of California, Irvine, CA 92697-4575, USA
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Abstract
We have created insulated C60 nanowire by packing C60 molecules into the interior of insulating boron nitride nanotubes (BNNTs). For small-diameter BNNTs, the wire consists of a linear chain of C60 molecules.With increasing BNNT inner diameter, unusual C60 stacking configurations are obtained (including helical, hollow core, and incommensurate) that are unknown for bulk or thin-film forms of C60.C60 in BNNTs thus presents a model system for studying the properties of dimensionally constrained "silo" crystal structures. For the linear-chain case, we have fused the C60 molecules to form a single-walled carbon nanotube inside the insulating BNNT.
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Affiliation(s)
- W Mickelson
- Department of Physics, University of California at Berkeley, Berkeley, CA 94720, USA
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Kudasov YB, Uzdin VM. Kondo state for a compact Cr trimer on a metallic surface. PHYSICAL REVIEW LETTERS 2002; 89:276802. [PMID: 12513230 DOI: 10.1103/physrevlett.89.276802] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/12/2002] [Indexed: 05/24/2023]
Abstract
The ground state of a Cr trimer supported on the Au(111) surface is investigated by means of a variational approach to the Coqblin-Schrieffer Hamiltonian. The temperature of Kondo-resonance formation (T(K)) for equilateral trimers increases drastically as compared to T(K) for a single Cr adatom. The Kondo state of a Cr trimer proves to be very sensitive to geometry and a small shift of any atom from the symmetrical position leads to a rapid decrease in T(K). These results are in good agreement with recent observations of the Kondo response of a single antiferromagnetic chromium trimer [T. Jamneala, Phys. Rev. Lett. 87, 256804 (2001)]].
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Affiliation(s)
- Yu B Kudasov
- VNIIEF, Prospect Mira 37, Sarov, Nizhni Novgorod Region, 607180, Russia.
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