1
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Mishra S, Vilas-Varela M, Lieske LA, Ortiz R, Fatayer S, Rončević I, Albrecht F, Frederiksen T, Peña D, Gross L. Bistability between π-diradical open-shell and closed-shell states in indeno[1,2-a]fluorene. Nat Chem 2024; 16:755-761. [PMID: 38332330 PMCID: PMC11087267 DOI: 10.1038/s41557-023-01431-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2023] [Accepted: 12/19/2023] [Indexed: 02/10/2024]
Abstract
Indenofluorenes are non-benzenoid conjugated hydrocarbons that have received great interest owing to their unusual electronic structure and potential applications in nonlinear optics and photovoltaics. Here we report the generation of unsubstituted indeno[1,2-a]fluorene on various surfaces by the cleavage of two C-H bonds in 7,12-dihydroindeno[1,2-a]fluorene through voltage pulses applied by the tip of a combined scanning tunnelling microscope and atomic force microscope. On bilayer NaCl on Au(111), indeno[1,2-a]fluorene is in the neutral charge state, but it exhibits charge bistability between neutral and anionic states on the lower-workfunction surfaces of bilayer NaCl on Ag(111) and Cu(111). In the neutral state, indeno[1,2-a]fluorene exhibits one of two ground states: an open-shell π-diradical state, predicted to be a triplet by density functional and multireference many-body perturbation theory calculations, or a closed-shell state with a para-quinodimethane moiety in the as-indacene core. We observe switching between open- and closed-shell states of a single molecule by changing its adsorption site on NaCl.
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Affiliation(s)
| | - Manuel Vilas-Varela
- Center for Research in Biological Chemistry and Molecular Materials (CiQUS) and Department of Organic Chemistry, University of Santiago de Compostela, Santiago de Compostela, Spain
| | | | - Ricardo Ortiz
- Donostia International Physics Center (DIPC), Donostia-San Sebastián, Spain
| | - Shadi Fatayer
- Applied Physics Program, Physical Science and Engineering Division (PSE), King Abdullah University of Science and Technology (KAUST), Thuwal, Kingdom of Saudi Arabia
| | - Igor Rončević
- Department of Chemistry, University of Oxford, Oxford, UK
| | | | - Thomas Frederiksen
- Donostia International Physics Center (DIPC), Donostia-San Sebastián, Spain
- Ikerbasque, Basque Foundation for Science, Bilbao, Spain
| | - Diego Peña
- Center for Research in Biological Chemistry and Molecular Materials (CiQUS) and Department of Organic Chemistry, University of Santiago de Compostela, Santiago de Compostela, Spain.
| | - Leo Gross
- IBM Research Europe - Zurich, Rüschlikon, Switzerland.
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2
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Hieulle J, Garcia Fernandez C, Friedrich N, Vegliante A, Sanz S, Sánchez-Portal D, Haley MM, Casado J, Frederiksen T, Pascual JI. From Solution to Surface: Persistence of the Diradical Character of a Diindenoanthracene Derivative on a Metallic Substrate. J Phys Chem Lett 2023; 14:11506-11512. [PMID: 38088859 DOI: 10.1021/acs.jpclett.3c02401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2023]
Abstract
Organic diradicals are envisioned as elementary building blocks for designing a new generation of spintronic devices and have been used in constructing prototypical field effect transistors and nonlinear optical devices. Open-shell systems, however, are also reactive, thus requiring design strategies to "protect" their radical character from the environment, especially when they are embedded in solid-state devices. Here, we report the persistence on a metallic surface of the diradical character of a diindeno[b,i]anthracene (DIAn) core protected by bulky end-groups. Our scanning tunneling spectroscopy measurements on single-molecules detected singlet-triplet excitations that were absent for DIAn species packed in assembled structures. Density functional theory simulations unravel that the molecular geometry on the metal substrate can crucially modify the value of the singlet-triplet gap via the delocalization of the radical sites. The persistence of the diradical character over metallic substrates is a promising finding for integrating radical-based materials into functional devices.
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Affiliation(s)
| | | | | | | | - Sofia Sanz
- Donostia International Physics Center (DIPC), 20018 Donostia-San Sebastián, Spain
| | - Daniel Sánchez-Portal
- Donostia International Physics Center (DIPC), 20018 Donostia-San Sebastián, Spain
- Centro de Física de Materiales MPC (CSIC/UPV-EHU), 20018 Donostia-San Sebastián, Spain
| | - Michael M Haley
- Department of Chemistry & Biochemistry and the Materials Science Institute, University of Oregon, Eugene, Oregon 97403-1253, United States
| | - Juan Casado
- Department of Physical Chemistry, University of Malaga, Campus de Teatinos s/n, 229071 Malaga, Spain
| | - Thomas Frederiksen
- Donostia International Physics Center (DIPC), 20018 Donostia-San Sebastián, Spain
- Ikerbasque, Basque Foundation for Science, 48013 Bilbao, Spain
| | - José Ignacio Pascual
- CIC nanoGUNE-BRTA, 20018 Donostia-San Sebastián, Spain
- Ikerbasque, Basque Foundation for Science, 48013 Bilbao, Spain
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3
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Brede J, Merino-Díez N, Berdonces-Layunta A, Sanz S, Domínguez-Celorrio A, Lobo-Checa J, Vilas-Varela M, Peña D, Frederiksen T, Pascual JI, de Oteyza DG, Serrate D. Detecting the spin-polarization of edge states in graphene nanoribbons. Nat Commun 2023; 14:6677. [PMID: 37865684 PMCID: PMC10590394 DOI: 10.1038/s41467-023-42436-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2022] [Accepted: 10/11/2023] [Indexed: 10/23/2023] Open
Abstract
Low dimensional carbon-based materials can show intrinsic magnetism associated to p-electrons in open-shell π-conjugated systems. Chemical design provides atomically precise control of the π-electron cloud, which makes them promising for nanoscale magnetic devices. However, direct verification of their spatially resolved spin-moment remains elusive. Here, we report the spin-polarization of chiral graphene nanoribbons (one-dimensional strips of graphene with alternating zig-zag and arm-chair boundaries), obtained by means of spin-polarized scanning tunnelling microscopy. We extract the energy-dependent spin-moment distribution of spatially extended edge states with π-orbital character, thus beyond localized magnetic moments at radical or defective carbon sites. Guided by mean-field Hubbard calculations, we demonstrate that electron correlations are responsible for the spin-splitting of the electronic structure. Our versatile platform utilizes a ferromagnetic substrate that stabilizes the organic magnetic moments against thermal and quantum fluctuations, while being fully compatible with on-surface synthesis of the rapidly growing class of nanographenes.
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Grants
- E13-20R Gobierno de Aragón
- E12-20R Gobierno de Aragón
- ED431G2019/03 Xunta de Galicia
- 863098 EC | EU Framework Programme for Research and Innovation H2020 | H2020 Priority Excellent Science | H2020 Future and Emerging Technologies (H2020 Excellent Science - Future and Emerging Technologies)
- PRE-2021-2-0190 Eusko Jaurlaritza (Basque Government)
- PIBA-2020-1-0014 Eusko Jaurlaritza (Basque Government)
- 863098 EC | EU Framework Programme for Research and Innovation H2020 | H2020 Priority Excellent Science | H2020 Future and Emerging Technologies (H2020 Excellent Science - Future and Emerging Technologies)
- Ministerio de Ciencia, Innovación y Universidades | Agencia Estatal de Investigación, Grant no PID2019-107338RB-C64 Eureopean Comission | European Regional Developement Funds | Interreg, Grant no EFA194/16 TNSI
- Ministerio de Ciencia, Innovación y Universidades | Agencia Estatal de Investigación, Grant no PID2019-107338RB-C64
- Ministerio de Ciencia, Innovación y Universidades | Agencia Estatal de Investigación, Grant no PID2019-107338RB-C62
- Ministerio de Ciencia, Innovación y Universidades | Agencia Estatal de Investigación, Grant no PID2020–115406GB-I00
- Ministerio de Ciencia, Innovación y Universidades | Agencia Estatal de Investigación, Grant no PID2019-107338RB-C61 Maria de Maeztu Excellence Program, Grant no CEX2020-001038-M Diputación Foral de Guipuzkoa | Guipuzkoa Next, grant no 2021-CIEN-000069-01
- Ministerio de Ciencia, Innovación y Universidades | Agencia Estatal de Investigación, Grant no PID2019-107338RB-C63
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Affiliation(s)
- Jens Brede
- Donostia International Physics Center, San Sebastián, E-20018, Spain
- Centro de Física de Materiales (MPC), CSIC-UPV/EHU, San Sebastián, E-20018, Spain
| | - Nestor Merino-Díez
- Donostia International Physics Center, San Sebastián, E-20018, Spain
- Centro de Física de Materiales (MPC), CSIC-UPV/EHU, San Sebastián, E-20018, Spain
| | - Alejandro Berdonces-Layunta
- Donostia International Physics Center, San Sebastián, E-20018, Spain
- Centro de Física de Materiales (MPC), CSIC-UPV/EHU, San Sebastián, E-20018, Spain
| | - Sofía Sanz
- Donostia International Physics Center, San Sebastián, E-20018, Spain
| | - Amelia Domínguez-Celorrio
- Instituto de Nanociencia y Materiales de Aragón (INMA), CSIC-Universidad de Zaragoza, Zaragoza, E-50009, Spain
| | - Jorge Lobo-Checa
- Instituto de Nanociencia y Materiales de Aragón (INMA), CSIC-Universidad de Zaragoza, Zaragoza, E-50009, Spain
- Departamento de Física de la Materia Condensada, Universidad de Zaragoza, Zaragoza, E-50009, Spain
- Laboratorio de Microscopias Avanzadas (LMA), Universidad de Zaragoza, Zaragoza, E-50009, Spain
| | - Manuel Vilas-Varela
- Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares (CiQUS) and Departamento de Química Orgánica, Universidade de Santiago de Compostela, Santiago de Compostela, E-15782, Spain
| | - Diego Peña
- Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares (CiQUS) and Departamento de Química Orgánica, Universidade de Santiago de Compostela, Santiago de Compostela, E-15782, Spain
| | - Thomas Frederiksen
- Donostia International Physics Center, San Sebastián, E-20018, Spain
- Ikerbasque, Basque Foundation for Science, Bilbao, E-48013, Spain
| | - José I Pascual
- Ikerbasque, Basque Foundation for Science, Bilbao, E-48013, Spain.
- CIC nanoGUNE BRTA, San Sebastián, E-20018, Spain.
| | - Dimas G de Oteyza
- Donostia International Physics Center, San Sebastián, E-20018, Spain.
- Centro de Física de Materiales (MPC), CSIC-UPV/EHU, San Sebastián, E-20018, Spain.
- Nanomaterials and Nanotechnology Research Center (CINN), CSIC-UNIOVI-PA, El Entrego, E-33940, Spain.
| | - David Serrate
- Instituto de Nanociencia y Materiales de Aragón (INMA), CSIC-Universidad de Zaragoza, Zaragoza, E-50009, Spain.
- Departamento de Física de la Materia Condensada, Universidad de Zaragoza, Zaragoza, E-50009, Spain.
- Laboratorio de Microscopias Avanzadas (LMA), Universidad de Zaragoza, Zaragoza, E-50009, Spain.
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4
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Okabayashi N, Frederiksen T, Liebig A, Giessibl FJ. Dynamic Friction Unraveled by Observing an Unexpected Intermediate State in Controlled Molecular Manipulation. Phys Rev Lett 2023; 131:148001. [PMID: 37862665 DOI: 10.1103/physrevlett.131.148001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/07/2023] [Revised: 04/26/2023] [Accepted: 08/30/2023] [Indexed: 10/22/2023]
Abstract
The pervasive phenomenon of friction has been studied at the nanoscale via a controlled manipulation of single atoms and molecules with a metallic tip, which enabled a precise determination of the static friction force necessary to initiate motion. However, little is known about the atomic dynamics during manipulation. Here, we reveal the complete manipulation process of a CO molecule on a Cu(110) surface at low temperatures using a combination of noncontact atomic force microscopy and density functional theory simulations. We found that an intermediate state, inaccessible for the far-tip position, is enabled in the reaction pathway for the close-tip position, which is crucial to understanding the manipulation process, including dynamic friction. Our results show how friction forces can be controlled and optimized, facilitating new fundamental insights for tribology.
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Affiliation(s)
- Norio Okabayashi
- Graduate School of Natural Science and Technology, Kanazawa University, Ishikawa 920-1192, Japan
| | - Thomas Frederiksen
- Donostia International Physics Center (DIPC), San Sebastián 20018, Spain
- IKERBASQUE, Basque Foundation for Science, Bilbao 48013, Spain
| | - Alexander Liebig
- Institute of Experimental and Applied Physics, University of Regensburg, Regensburg D-93053, Germany
| | - Franz J Giessibl
- Institute of Experimental and Applied Physics, University of Regensburg, Regensburg D-93053, Germany
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5
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Du Q, Su X, Liu Y, Jiang Y, Li C, Yan K, Ortiz R, Frederiksen T, Wang S, Yu P. Orbital-symmetry effects on magnetic exchange in open-shell nanographenes. Nat Commun 2023; 14:4802. [PMID: 37558678 PMCID: PMC10412602 DOI: 10.1038/s41467-023-40542-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Accepted: 08/01/2023] [Indexed: 08/11/2023] Open
Abstract
Open-shell nanographenes appear as promising candidates for future applications in spintronics and quantum technologies. A critical aspect to realize this potential is to design and control the magnetic exchange. Here, we reveal the effects of frontier orbital symmetries on the magnetic coupling in diradical nanographenes through scanning probe microscope measurements and different levels of theoretical calculations. In these open-shell nanographenes, the exchange energy exhibits a remarkable variation between 20 and 160 meV. Theoretical calculations reveal that frontier orbital symmetries play a key role in affecting the magnetic coupling on such a large scale. Moreover, a triradical nanographene is demonstrated for investigating the magnetic interaction among three unpaired electrons with unequal magnetic exchange, in agreement with Heisenberg spin model calculations. Our results provide insights into both theoretical design and experimental realization of nanographene materials with different exchange interactions through tuning the orbital symmetry, potentially useful for realizing magnetically operable graphene-based nanomaterials.
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Affiliation(s)
- Qingyang Du
- School of Physical Science and Technology, ShanghaiTech University, 201210, Shanghai, China
| | - Xuelei Su
- School of Physical Science and Technology, ShanghaiTech University, 201210, Shanghai, China
| | - Yufeng Liu
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Yashi Jiang
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Can Li
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - KaKing Yan
- School of Physical Science and Technology, ShanghaiTech University, 201210, Shanghai, China
| | - Ricardo Ortiz
- Donostia International Physics Center (DIPC) - UPV/EHU, 20018, San Sebastián, Spain.
| | - Thomas Frederiksen
- Donostia International Physics Center (DIPC) - UPV/EHU, 20018, San Sebastián, Spain.
- IKERBASQUE, Basque Foundation for Science, 48013, Bilbao, Spain.
| | - Shiyong Wang
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, 200240, China.
- Tsung-Dao Lee Institute, Shanghai Jiao Tong University, Shanghai, 200240, China.
| | - Ping Yu
- School of Physical Science and Technology, ShanghaiTech University, 201210, Shanghai, China.
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6
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Sanz Wuhl S, Papior NR, Giedke G, Sánchez-Portal D, Brandbyge M, Frederiksen T. Mach-Zehnder-like interferometry with graphene nanoribbon networks. J Phys Condens Matter 2023. [PMID: 37220757 DOI: 10.1088/1361-648x/acd832] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
We study theoretically electron interference in a Mach-Zehnder-like geometry formed by four zigzag graphene nanoribbons (ZGNRs) arranged in parallel pairs, one on top of the other, such that they form intersection angles of 60º. Depending on the interribbon separation, each intersection can be tuned to act either as an electron beam splitter or as a mirror, enabling tuneable circuitry with interfering pathways. Based on the mean-field Hubbard model and Green's function techniques, we evaluate the electron transport properties of such 8-terminal devices and identify pairs of terminals that are subject to self-interference. We further show that the scattering matrix formalism in the approximation of independent scattering at the four individual junctions provides accurate results as compared with the Green's function description, allowing for a simple interpretation of the interference process between two dominant pathways. This enables us to characterize the device sensitivity to phase shifts from an external magnetic flux according to the Aharonov-Bohm effect as well as from small geometric variations in the two path lengths. The proposed devices could find applications as magnetic field sensors and as detectors of phase shifts induced by local scatterers on the different segments, such as adsorbates, impurities or defects. The setup could also be used to create and study quantum entanglement.
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Affiliation(s)
- Sofia Sanz Wuhl
- Nanoelectronics, Donostia International Physics Center, Paseo Manuel de Lardizabal 4, San Sebastian, 20018, SPAIN
| | - Nick Rübner Papior
- Nanotech, The Danish Technical University, Ørsteds Plads, building 345E, 2800, Kgs. Lyngby, Kgs. Lyngby, 2800, DENMARK
| | - Géza Giedke
- Donostia International Physics Center, Paseo Manuel de Lardizabal 4, Donostia-San Sebastian, Guipuzkoa, 20018, SPAIN
| | - Daniel Sánchez-Portal
- Centro de Fisica de Materiales, Paseo Manuel de Lardizabal 5, San Sebastian, País Vasco, 20018, SPAIN
| | - Mads Brandbyge
- Department of Physics, Technical University of Denmark, Kgs. Lyngby, Kgs. Lyngby, DK-2800, DENMARK
| | - Thomas Frederiksen
- Donostia International Physics Center, Paseo Manuel de Lardizabal, Donostia-San Sebastián, 4 E-20018 , SPAIN
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7
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de Oteyza DG, Frederiksen T. Carbon-based nanostructures as a versatile platform for tunable π-magnetism. J Phys Condens Matter 2022; 34:443001. [PMID: 35977474 DOI: 10.1088/1361-648x/ac8a7f] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Accepted: 08/17/2022] [Indexed: 06/15/2023]
Abstract
Emergence ofπ-magnetism in open-shell nanographenes has been theoretically predicted decades ago but their experimental characterization was elusive due to the strong chemical reactivity that makes their synthesis and stabilization difficult. In recent years, on-surface synthesis under vacuum conditions has provided unprecedented opportunities for atomically precise engineering of nanographenes, which in combination with scanning probe techniques have led to a substantial progress in our capabilities to realize localized electron spin states and to control electron spin interactions at the atomic scale. Here we review the essential concepts and the remarkable advances in the last few years, and outline the versatility of carbon-basedπ-magnetic materials as an interesting platform for applications in spintronics and quantum technologies.
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Affiliation(s)
- Dimas G de Oteyza
- Nanomaterials and Nanotechnology Research Center (CINN), CSIC-UNIOVI-PA, E-33940 El Entrego, Spain
- Donostia International Physics Center (DIPC)-UPV/EHU, E-20018 San Sebastián, Spain
| | - Thomas Frederiksen
- Donostia International Physics Center (DIPC)-UPV/EHU, E-20018 San Sebastián, Spain
- Ikerbasque, Basque Foundation for Science, E-48013 Bilbao, Spain
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8
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Sanz S, Papior N, Giedke G, Sánchez-Portal D, Brandbyge M, Frederiksen T. Spin-Polarizing Electron Beam Splitter from Crossed Graphene Nanoribbons. Phys Rev Lett 2022; 129:037701. [PMID: 35905343 DOI: 10.1103/physrevlett.129.037701] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2022] [Accepted: 05/27/2022] [Indexed: 06/15/2023]
Abstract
Junctions composed of two crossed graphene nanoribbons (GNRs) have been theoretically proposed as electron beam splitters where incoming electron waves in one GNR can be split coherently into propagating waves in two outgoing terminals with nearly equal amplitude and zero back-scattering. Here we scrutinize this effect for devices composed of narrow zigzag GNRs taking explicitly into account the role of Coulomb repulsion that leads to spin-polarized edge states within mean-field theory. We show that the beam-splitting effect survives the opening of the well-known correlation gap and, more strikingly, that a spin-dependent scattering potential emerges which spin polarizes the transmitted electrons in the two outputs. By studying different ribbons and intersection angles we provide evidence that this is a general feature with edge-polarized nanoribbons. A near-perfect polarization can be achieved by joining several junctions in series. Our findings suggest that GNRs are interesting building blocks in spintronics and quantum technologies with applications for interferometry and entanglement.
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Affiliation(s)
- Sofia Sanz
- Donostia International Physics Center (DIPC), E-20018 Donostia-San Sebastián, Spain
| | - Nick Papior
- DTU Computing Center, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark
| | - Géza Giedke
- Donostia International Physics Center (DIPC), E-20018 Donostia-San Sebastián, Spain
- IKERBASQUE, Basque Foundation for Science, E-48013 Bilbao, Spain
| | - Daniel Sánchez-Portal
- Centro de Física de Materiales (CFM) CSIC-UPV/EHU, E-20018 Donostia-San Sebastián, Spain
| | - Mads Brandbyge
- Center for Nanostructured Graphene, Department of Physics, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark
| | - Thomas Frederiksen
- Donostia International Physics Center (DIPC), E-20018 Donostia-San Sebastián, Spain
- IKERBASQUE, Basque Foundation for Science, E-48013 Bilbao, Spain
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9
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Wang T, Sanz S, Castro-Esteban J, Lawrence J, Berdonces-Layunta A, Mohammed MSG, Vilas-Varela M, Corso M, Peña D, Frederiksen T, de Oteyza DG. Magnetic Interactions Between Radical Pairs in Chiral Graphene Nanoribbons. Nano Lett 2022; 22:164-171. [PMID: 34936370 DOI: 10.1021/acs.nanolett.1c03578] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Open-shell graphene nanoribbons have become promising candidates for future applications, including quantum technologies. Here, we characterize magnetic states hosted by chiral graphene nanoribbons (chGNRs). The substitution of a hydrogen atom at the chGNR edge by a ketone effectively adds one pz electron to the π-electron network, producing an unpaired π-radical. A similar scenario occurs for regular ketone-functionalized chGNRs in which one ketone is missing. Two such radical states can interact via exchange coupling, and we study those interactions as a function of their relative position, which includes a remarkable dependence on the chirality, as well as on the nature of the surrounding ribbon, that is, with or without ketone functionalization. Besides, we determine the parameters whereby this type of system with oxygen heteroatoms can be adequately described within the widely used mean-field Hubbard model. Altogether, we provide insight to both theoretically model and devise GNR-based nanostructures with tunable magnetic properties.
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Affiliation(s)
- Tao Wang
- Donostia International Physics Center, 20018 San Sebastián, Spain
- Centro de Fisica de Materiales CFM/MPC, CSIC-UPV/EHU, 20018 San Sebastián, Spain
| | - Sofia Sanz
- Donostia International Physics Center, 20018 San Sebastián, Spain
| | - Jesús Castro-Esteban
- Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares (CiQUS) and Departamento de Química Orgánica, Universidade de Santiago de Compostela, 15782 Santiago de Compostela, Spain
| | - James Lawrence
- Donostia International Physics Center, 20018 San Sebastián, Spain
- Centro de Fisica de Materiales CFM/MPC, CSIC-UPV/EHU, 20018 San Sebastián, Spain
| | - Alejandro Berdonces-Layunta
- Donostia International Physics Center, 20018 San Sebastián, Spain
- Centro de Fisica de Materiales CFM/MPC, CSIC-UPV/EHU, 20018 San Sebastián, Spain
| | - Mohammed S G Mohammed
- Donostia International Physics Center, 20018 San Sebastián, Spain
- Centro de Fisica de Materiales CFM/MPC, CSIC-UPV/EHU, 20018 San Sebastián, Spain
| | - Manuel Vilas-Varela
- Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares (CiQUS) and Departamento de Química Orgánica, Universidade de Santiago de Compostela, 15782 Santiago de Compostela, Spain
| | - Martina Corso
- Donostia International Physics Center, 20018 San Sebastián, Spain
- Centro de Fisica de Materiales CFM/MPC, CSIC-UPV/EHU, 20018 San Sebastián, Spain
| | - Diego Peña
- Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares (CiQUS) and Departamento de Química Orgánica, Universidade de Santiago de Compostela, 15782 Santiago de Compostela, Spain
| | - Thomas Frederiksen
- Donostia International Physics Center, 20018 San Sebastián, Spain
- Ikerbasque, Basque Foundation for Science, 48013 Bilbao, Spain
| | - Dimas G de Oteyza
- Donostia International Physics Center, 20018 San Sebastián, Spain
- Centro de Fisica de Materiales CFM/MPC, CSIC-UPV/EHU, 20018 San Sebastián, Spain
- Ikerbasque, Basque Foundation for Science, 48013 Bilbao, Spain
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10
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Hieulle J, Castro S, Friedrich N, Vegliante A, Lara FR, Sanz S, Rey D, Corso M, Frederiksen T, Pascual JI, Peña D. On-Surface Synthesis and Collective Spin Excitations of a Triangulene-Based Nanostar. Angew Chem Int Ed Engl 2021; 60:25224-25229. [PMID: 34647398 PMCID: PMC9292598 DOI: 10.1002/anie.202108301] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2021] [Indexed: 12/02/2022]
Abstract
Triangulene nanographenes are open‐shell molecules with predicted high spin state due to the frustration of their conjugated network. Their long‐sought synthesis became recently possible over a metal surface. Here, we present a macrocycle formed by six [3]triangulenes, which was obtained by combining the solution synthesis of a dimethylphenyl‐anthracene cyclic hexamer and the on‐surface cyclodehydrogenation of this precursor over a gold substrate. The resulting triangulene nanostar exhibits a collective spin state generated by the interaction of its 12 unpaired π‐electrons along the conjugated lattice, corresponding to the antiferromagnetic ordering of six S=1 sites (one per triangulene unit). Inelastic electron tunneling spectroscopy resolved three spin excitations connecting the singlet ground state with triplet states. The nanostar behaves close to predictions from the Heisenberg model of an S=1 spin ring, representing a unique system to test collective spin modes in cyclic systems.
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Affiliation(s)
| | - Silvia Castro
- Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares (CiQUS) and Departamento de Química Orgánica, Universidade de Santiago de Compostela, 15782-, Santiago de Compostela, Spain
| | | | | | - Francisco Romero Lara
- CIC nanoGUNE-BRTA, 20018, Donostia-San Sebastián, Spain.,Centro de Física de Materiales CSIC/UPV-EHU-Materials Physics Center, 20018, Donostia-San Sebastián, Spain
| | - Sofía Sanz
- Donostia International Physics Center (DIPC), 20018, Donostia-San Sebastián, Spain
| | - Dulce Rey
- Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares (CiQUS) and Departamento de Química Orgánica, Universidade de Santiago de Compostela, 15782-, Santiago de Compostela, Spain
| | - Martina Corso
- Centro de Física de Materiales CSIC/UPV-EHU-Materials Physics Center, 20018, Donostia-San Sebastián, Spain.,Donostia International Physics Center (DIPC), 20018, Donostia-San Sebastián, Spain
| | - Thomas Frederiksen
- Donostia International Physics Center (DIPC), 20018, Donostia-San Sebastián, Spain.,Ikerbasque, Basque Foundation for Science, 48013, Bilbao, Spain
| | - Jose Ignacio Pascual
- CIC nanoGUNE-BRTA, 20018, Donostia-San Sebastián, Spain.,Ikerbasque, Basque Foundation for Science, 48013, Bilbao, Spain
| | - Diego Peña
- Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares (CiQUS) and Departamento de Química Orgánica, Universidade de Santiago de Compostela, 15782-, Santiago de Compostela, Spain
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11
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Hieulle J, Castro S, Friedrich N, Vegliante A, Lara FR, Sanz S, Rey D, Corso M, Frederiksen T, Pascual JI, Peña D. Frontispiece: On‐Surface Synthesis and Collective Spin Excitations of a Triangulene‐Based Nanostar. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/anie.202184861] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
| | - Silvia Castro
- Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares (CiQUS) and Departamento de Química Orgánica Universidade de Santiago de Compostela 15782- Santiago de Compostela Spain
| | | | | | - Francisco Romero Lara
- CIC nanoGUNE-BRTA 20018 Donostia-San Sebastián Spain
- Centro de Física de Materiales CSIC/UPV-EHU-Materials Physics Center 20018 Donostia-San Sebastián Spain
| | - Sofía Sanz
- Donostia International Physics Center (DIPC) 20018 Donostia-San Sebastián Spain
| | - Dulce Rey
- Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares (CiQUS) and Departamento de Química Orgánica Universidade de Santiago de Compostela 15782- Santiago de Compostela Spain
| | - Martina Corso
- Centro de Física de Materiales CSIC/UPV-EHU-Materials Physics Center 20018 Donostia-San Sebastián Spain
- Donostia International Physics Center (DIPC) 20018 Donostia-San Sebastián Spain
| | - Thomas Frederiksen
- Donostia International Physics Center (DIPC) 20018 Donostia-San Sebastián Spain
- Ikerbasque Basque Foundation for Science 48013 Bilbao Spain
| | - Jose Ignacio Pascual
- CIC nanoGUNE-BRTA 20018 Donostia-San Sebastián Spain
- Ikerbasque Basque Foundation for Science 48013 Bilbao Spain
| | - Diego Peña
- Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares (CiQUS) and Departamento de Química Orgánica Universidade de Santiago de Compostela 15782- Santiago de Compostela Spain
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12
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Hieulle J, Castro S, Friedrich N, Vegliante A, Lara FR, Sanz S, Rey D, Corso M, Frederiksen T, Pascual JI, Peña D. Frontispiz: On‐Surface Synthesis and Collective Spin Excitations of a Triangulene‐Based Nanostar. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202184861] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
| | - Silvia Castro
- Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares (CiQUS) and Departamento de Química Orgánica Universidade de Santiago de Compostela 15782- Santiago de Compostela Spain
| | | | | | - Francisco Romero Lara
- CIC nanoGUNE-BRTA 20018 Donostia-San Sebastián Spain
- Centro de Física de Materiales CSIC/UPV-EHU-Materials Physics Center 20018 Donostia-San Sebastián Spain
| | - Sofía Sanz
- Donostia International Physics Center (DIPC) 20018 Donostia-San Sebastián Spain
| | - Dulce Rey
- Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares (CiQUS) and Departamento de Química Orgánica Universidade de Santiago de Compostela 15782- Santiago de Compostela Spain
| | - Martina Corso
- Centro de Física de Materiales CSIC/UPV-EHU-Materials Physics Center 20018 Donostia-San Sebastián Spain
- Donostia International Physics Center (DIPC) 20018 Donostia-San Sebastián Spain
| | - Thomas Frederiksen
- Donostia International Physics Center (DIPC) 20018 Donostia-San Sebastián Spain
- Ikerbasque Basque Foundation for Science 48013 Bilbao Spain
| | - Jose Ignacio Pascual
- CIC nanoGUNE-BRTA 20018 Donostia-San Sebastián Spain
- Ikerbasque Basque Foundation for Science 48013 Bilbao Spain
| | - Diego Peña
- Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares (CiQUS) and Departamento de Química Orgánica Universidade de Santiago de Compostela 15782- Santiago de Compostela Spain
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13
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Hieulle J, Castro S, Friedrich N, Vegliante A, Lara FR, Sanz S, Rey D, Corso M, Frederiksen T, Pascual JI, Peña D. On‐Surface Synthesis and Collective Spin Excitations of a Triangulene‐Based Nanostar. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202108301] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
| | - Silvia Castro
- Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares (CiQUS) and Departamento de Química Orgánica Universidade de Santiago de Compostela 15782- Santiago de Compostela Spain
| | | | | | - Francisco Romero Lara
- CIC nanoGUNE-BRTA 20018 Donostia-San Sebastián Spain
- Centro de Física de Materiales CSIC/UPV-EHU-Materials Physics Center 20018 Donostia-San Sebastián Spain
| | - Sofía Sanz
- Donostia International Physics Center (DIPC) 20018 Donostia-San Sebastián Spain
| | - Dulce Rey
- Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares (CiQUS) and Departamento de Química Orgánica Universidade de Santiago de Compostela 15782- Santiago de Compostela Spain
| | - Martina Corso
- Centro de Física de Materiales CSIC/UPV-EHU-Materials Physics Center 20018 Donostia-San Sebastián Spain
- Donostia International Physics Center (DIPC) 20018 Donostia-San Sebastián Spain
| | - Thomas Frederiksen
- Donostia International Physics Center (DIPC) 20018 Donostia-San Sebastián Spain
- Ikerbasque Basque Foundation for Science 48013 Bilbao Spain
| | - Jose Ignacio Pascual
- CIC nanoGUNE-BRTA 20018 Donostia-San Sebastián Spain
- Ikerbasque Basque Foundation for Science 48013 Bilbao Spain
| | - Diego Peña
- Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares (CiQUS) and Departamento de Química Orgánica Universidade de Santiago de Compostela 15782- Santiago de Compostela Spain
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14
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Li J, Sanz S, Merino-Díez N, Vilas-Varela M, Garcia-Lekue A, Corso M, de Oteyza DG, Frederiksen T, Peña D, Pascual JI. Topological phase transition in chiral graphene nanoribbons: from edge bands to end states. Nat Commun 2021; 12:5538. [PMID: 34545075 PMCID: PMC8452617 DOI: 10.1038/s41467-021-25688-z] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Accepted: 08/20/2021] [Indexed: 02/08/2023] Open
Abstract
Precise control over the size and shape of graphene nanostructures allows engineering spin-polarized edge and topological states, representing a novel source of non-conventional π-magnetism with promising applications in quantum spintronics. A prerequisite for their emergence is the existence of robust gapped phases, which are difficult to find in extended graphene systems. Here we show that semi-metallic chiral GNRs (chGNRs) narrowed down to nanometer widths undergo a topological phase transition. We fabricated atomically precise chGNRs of different chirality and size by on surface synthesis using predesigned molecular precursors. Combining scanning tunneling microscopy (STM) measurements and theory simulations, we follow the evolution of topological properties and bulk band gap depending on the width, length, and chirality of chGNRs. Our findings represent a new platform for producing topologically protected spin states and demonstrate the potential of connecting chiral edge and defect structure with band engineering.
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Affiliation(s)
- Jingcheng Li
- grid.424265.30000 0004 1761 1166CIC nanoGUNE-BRTA, Donostia-San Sebastián, Spain ,Centro de Física de Materiales MPC (CSIC-UPV/EHU), Donostia-San Sebastián, Spain ,grid.12981.330000 0001 2360 039XPresent Address: School of Physics, Sun Yat-sen University, Guangzhou, China
| | - Sofia Sanz
- grid.452382.a0000 0004 1768 3100Donostia International Physics Center (DIPC), Donostia-San Sebastián, Spain
| | - Nestor Merino-Díez
- grid.424265.30000 0004 1761 1166CIC nanoGUNE-BRTA, Donostia-San Sebastián, Spain ,grid.452382.a0000 0004 1768 3100Donostia International Physics Center (DIPC), Donostia-San Sebastián, Spain
| | - Manuel Vilas-Varela
- grid.11794.3a0000000109410645Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares (CiQUS), Departamento de Química Orgánica, Universidade de Santiago de Compostela, Santiago de Compostela, Spain
| | - Aran Garcia-Lekue
- grid.452382.a0000 0004 1768 3100Donostia International Physics Center (DIPC), Donostia-San Sebastián, Spain ,grid.424810.b0000 0004 0467 2314Ikerbasque, Basque Foundation for Science, Bilbao, Spain
| | - Martina Corso
- Centro de Física de Materiales MPC (CSIC-UPV/EHU), Donostia-San Sebastián, Spain ,grid.452382.a0000 0004 1768 3100Donostia International Physics Center (DIPC), Donostia-San Sebastián, Spain ,grid.424810.b0000 0004 0467 2314Ikerbasque, Basque Foundation for Science, Bilbao, Spain
| | - Dimas G. de Oteyza
- Centro de Física de Materiales MPC (CSIC-UPV/EHU), Donostia-San Sebastián, Spain ,grid.452382.a0000 0004 1768 3100Donostia International Physics Center (DIPC), Donostia-San Sebastián, Spain ,grid.424810.b0000 0004 0467 2314Ikerbasque, Basque Foundation for Science, Bilbao, Spain
| | - Thomas Frederiksen
- grid.452382.a0000 0004 1768 3100Donostia International Physics Center (DIPC), Donostia-San Sebastián, Spain ,grid.424810.b0000 0004 0467 2314Ikerbasque, Basque Foundation for Science, Bilbao, Spain
| | - Diego Peña
- grid.11794.3a0000000109410645Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares (CiQUS), Departamento de Química Orgánica, Universidade de Santiago de Compostela, Santiago de Compostela, Spain
| | - Jose Ignacio Pascual
- grid.424265.30000 0004 1761 1166CIC nanoGUNE-BRTA, Donostia-San Sebastián, Spain ,grid.424810.b0000 0004 0467 2314Ikerbasque, Basque Foundation for Science, Bilbao, Spain
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15
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Affiliation(s)
- Thomas Frederiksen
- Donostia International Physics Center, Donostia-San Sebastián, Spain.
- IKERBASQUE, Basque Foundation for Science, Bilbao, Spain.
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16
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Friedrich N, Brandimarte P, Li J, Saito S, Yamaguchi S, Pozo I, Peña D, Frederiksen T, Garcia-Lekue A, Sánchez-Portal D, Pascual JI. Magnetism of Topological Boundary States Induced by Boron Substitution in Graphene Nanoribbons. Phys Rev Lett 2020; 125:146801. [PMID: 33064521 DOI: 10.1103/physrevlett.125.146801] [Citation(s) in RCA: 43] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Accepted: 08/10/2020] [Indexed: 06/11/2023]
Abstract
Graphene nanoribbons (GNRs), low-dimensional platforms for carbon-based electronics, show the promising perspective to also incorporate spin polarization in their conjugated electron system. However, magnetism in GNRs is generally associated with localized states around zigzag edges, difficult to fabricate and with high reactivity. Here we demonstrate that magnetism can also be induced away from physical GNR zigzag edges through atomically precise engineering topological defects in its interior. A pair of substitutional boron atoms inserted in the carbon backbone breaks the conjugation of their topological bands and builds two spin-polarized boundary states around them. The spin state was detected in electrical transport measurements through boron-substituted GNRs suspended between the tip and the sample of a scanning tunneling microscope. First-principle simulations find that boron pairs induce a spin 1, which is modified by tuning the spacing between pairs. Our results demonstrate a route to embed spin chains in GNRs, turning them into basic elements of spintronic devices.
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Affiliation(s)
| | - Pedro Brandimarte
- Donostia International Physics Center (DIPC), 20018 Donostia-San Sebastián, Spain
| | - Jingcheng Li
- CIC nanoGUNE BRTA, 20018 Donostia-San Sebastián, Spain
| | - Shohei Saito
- Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | | | - Iago Pozo
- Centro de Investigación en Química Biolóxica e Materiais Moleculares (CiQUS) and Departamento de Química Orgánica, Universidade de Santiago de Compostela, 15782 Santiago de Compostela, Spain
| | - Diego Peña
- Centro de Investigación en Química Biolóxica e Materiais Moleculares (CiQUS) and Departamento de Química Orgánica, Universidade de Santiago de Compostela, 15782 Santiago de Compostela, Spain
| | - Thomas Frederiksen
- Donostia International Physics Center (DIPC), 20018 Donostia-San Sebastián, Spain
- Ikerbasque, Basque Foundation for Science, 48013 Bilbao, Spain
| | - Aran Garcia-Lekue
- Donostia International Physics Center (DIPC), 20018 Donostia-San Sebastián, Spain
- Ikerbasque, Basque Foundation for Science, 48013 Bilbao, Spain
| | - Daniel Sánchez-Portal
- Donostia International Physics Center (DIPC), 20018 Donostia-San Sebastián, Spain
- Centro de Física de Materiales CSIC-UPV/EHU, 20018 Donostia-San Sebastián, Spain
| | - José Ignacio Pascual
- CIC nanoGUNE BRTA, 20018 Donostia-San Sebastián, Spain
- Ikerbasque, Basque Foundation for Science, 48013 Bilbao, Spain
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17
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Li J, Sanz S, Castro-Esteban J, Vilas-Varela M, Friedrich N, Frederiksen T, Peña D, Pascual JI. Uncovering the Triplet Ground State of Triangular Graphene Nanoflakes Engineered with Atomic Precision on a Metal Surface. Phys Rev Lett 2020; 124:177201. [PMID: 32412280 DOI: 10.1103/physrevlett.124.177201] [Citation(s) in RCA: 72] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2019] [Revised: 02/17/2020] [Accepted: 04/02/2020] [Indexed: 06/11/2023]
Abstract
Graphene can develop large magnetic moments in custom-crafted open-shell nanostructures such as triangulene, a triangular piece of graphene with zigzag edges. Current methods of engineering graphene nanosystems on surfaces succeeded in producing atomically precise open-shell structures, but demonstration of their net spin remains elusive to date. Here, we fabricate triangulenelike graphene systems and demonstrate that they possess a spin S=1 ground state. Scanning tunneling spectroscopy identifies the fingerprint of an underscreened S=1 Kondo state on these flakes at low temperatures, signaling the dominant ferromagnetic interactions between two spins. Combined with simulations based on the meanfield Hubbard model, we show that this S=1 π paramagnetism is robust and can be turned into an S=1/2 state by additional H atoms attached to the radical sites. Our results demonstrate that π paramagnetism of high-spin graphene flakes can survive on surfaces, opening the door to study the quantum behavior of interacting π spins in graphene systems.
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Affiliation(s)
- Jingcheng Li
- CIC Nanogune BRTA, 20018 Donostia-San Sebastián, Spain
| | - Sofia Sanz
- Donostia International Physics Center (DIPC), 20018 Donostia-San Sebastián, Spain
| | - Jesus Castro-Esteban
- Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares (CiQUS), and Departamento de Química Orgánica, Universidade de Santiago de Compostela, 15705 Santiago de Compostela, Spain
| | - Manuel Vilas-Varela
- Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares (CiQUS), and Departamento de Química Orgánica, Universidade de Santiago de Compostela, 15705 Santiago de Compostela, Spain
| | | | - Thomas Frederiksen
- Donostia International Physics Center (DIPC), 20018 Donostia-San Sebastián, Spain
- Ikerbasque, Basque Foundation for Science, 48013 Bilbao, Spain
| | - Diego Peña
- Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares (CiQUS), and Departamento de Química Orgánica, Universidade de Santiago de Compostela, 15705 Santiago de Compostela, Spain
| | - Jose Ignacio Pascual
- CIC Nanogune BRTA, 20018 Donostia-San Sebastián, Spain
- Ikerbasque, Basque Foundation for Science, 48013 Bilbao, Spain
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Jasper-Toennies T, Gruber M, Johannsen S, Frederiksen T, Garcia-Lekue A, Jäkel T, Roehricht F, Herges R, Berndt R. Rotation of Ethoxy and Ethyl Moieties on a Molecular Platform on Au(111). ACS Nano 2020; 14:3907-3916. [PMID: 32073820 DOI: 10.1021/acsnano.0c00029] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Molecular rotors have attracted considerable interest for their prospects in nanotechnology. However, their adsorption on supporting substrates, where they may be addressed individually, usually modifies their properties. Here, we investigate the switching of two closely related three-state rotors mounted on platforms on Au(111) using low-temperature scanning tunneling microscopy and density functional theory calculations. Being physisorbed, the platforms retain important gas-phase properties of the rotor. This simplifies a detailed analysis and permits, for instance, the identification of the vibrational modes involved in the rotation process. The symmetry provided by the platform enables active control of the rotation direction through electrostatic interactions with the tip and charged neighboring adsorbates. The present investigation of two model systems may turn out useful for designing platforms that provide directional rotation and for transferring more sophisticated molecular machines from the gas phase to surfaces.
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Affiliation(s)
- Torben Jasper-Toennies
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität, 24098 Kiel, Germany
| | - Manuel Gruber
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität, 24098 Kiel, Germany
| | - Sven Johannsen
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität, 24098 Kiel, Germany
| | - Thomas Frederiksen
- Donostia International Physics Center, DIPC, Paseo Manuel de Lardizabal 4, E-20018 Donostia-San Sebastián, Spain
- IKERBASQUE, Basque Foundation for Science, E-48013 Bilbao, Spain
| | - Aran Garcia-Lekue
- Donostia International Physics Center, DIPC, Paseo Manuel de Lardizabal 4, E-20018 Donostia-San Sebastián, Spain
- IKERBASQUE, Basque Foundation for Science, E-48013 Bilbao, Spain
| | - Torben Jäkel
- Otto-Diels-Institut für Organische Chemie, Christian-Albrechts-Universität, 24098 Kiel, Germany
| | - Fynn Roehricht
- Otto-Diels-Institut für Organische Chemie, Christian-Albrechts-Universität, 24098 Kiel, Germany
| | - Rainer Herges
- Otto-Diels-Institut für Organische Chemie, Christian-Albrechts-Universität, 24098 Kiel, Germany
| | - Richard Berndt
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität, 24098 Kiel, Germany
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19
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Schaeverbeke Q, Avriller R, Frederiksen T, Pistolesi F. Single-Photon Emission Mediated by Single-Electron Tunneling in Plasmonic Nanojunctions. Phys Rev Lett 2019; 123:246601. [PMID: 31922843 DOI: 10.1103/physrevlett.123.246601] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2019] [Indexed: 05/24/2023]
Abstract
Recent scanning tunneling microscopy (STM) experiments reported single-molecule fluorescence induced by tunneling currents in the nanoplasmonic cavity formed by the STM tip and the substrate. The electric field of the cavity mode couples with the current-induced charge fluctuations of the molecule, allowing the excitation of photons. We investigate theoretically this system for the experimentally relevant limit of large damping rate κ for the cavity mode and arbitrary coupling strength to a single-electronic level. We find that for bias voltages close to the first inelastic threshold of photon emission, the emitted light displays antibunching behavior with vanishing second-order photon correlation function. At the same time, the current and the intensity of emitted light display Franck-Condon steps at multiples of the cavity frequency ω_{c} with a width controlled by κ rather than the temperature T. For large bias voltages, we predict strong photon bunching of the order of κ/Γ where Γ is the electronic tunneling rate. Our theory thus predicts that strong coupling to a single level allows current-driven nonclassical light emission.
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Affiliation(s)
- Q Schaeverbeke
- Univ. Bordeaux, CNRS, LOMA, UMR 5798, F-33405 Talence, France
- Donostia International Physics Center (DIPC), E-20018 Donostia-San Sebastián, Spain
| | - R Avriller
- Univ. Bordeaux, CNRS, LOMA, UMR 5798, F-33405 Talence, France
| | - T Frederiksen
- Donostia International Physics Center (DIPC), E-20018 Donostia-San Sebastián, Spain
- Ikerbasque, Basque Foundation for Science, E-48013 Bilbao, Spain
| | - F Pistolesi
- Univ. Bordeaux, CNRS, LOMA, UMR 5798, F-33405 Talence, France
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20
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Jasper-Tönnies T, Garcia-Lekue A, Frederiksen T, Ulrich S, Herges R, Berndt R. High-conductance contacts to functionalized molecular platforms physisorbed on Au(1 1 1). J Phys Condens Matter 2019; 31:18LT01. [PMID: 30721893 DOI: 10.1088/1361-648x/ab0489] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The conductances of molecules physisorbed to Au(1 1 1) via an extended [Formula: see text] system are probed with the tip of a low-temperature scanning tunneling microscope to maximize the control of the junction geometry. Inert hydrogen, methyl, and reactive propynyl subunits were attached to the platform and stand upright. Because of their different reactivities, either non-bonding (hydrogen and methyl) or bonding (propynyl) tip-molecule contacts are formed. The conductances exhibit little scatter between different experimental runs on different molecules, display distinct evolutions with the tip-subunit distance, and reach contact values of 0.003-0.05 G 0. For equal tip-platform distances the contact conductance of the inert methyl is close to that of the reactive propynyl. Under further compression, the inert species, hydrogen and methyl, are found to be better conductors. This shows that the current flow is not directly correlated with the chemical interaction. Atomistic calculations for the methyl case reproduce the conductance evolution and reveal the role of the junction geometry, forces and orbital symmetries at the tip-molecule interface. The current flow is controlled by orbital symmetries at the electrode interfaces rather than by the energy alignment of the molecular orbitals and electrode states. Functionalized molecular platforms thus open new ways to control and engineer electron conduction through metal-molecule interfaces at the atomic level.
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Affiliation(s)
- Torben Jasper-Tönnies
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität, 24098 Kiel, Germany
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21
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Li J, Sanz S, Corso M, Choi DJ, Peña D, Frederiksen T, Pascual JI. Single spin localization and manipulation in graphene open-shell nanostructures. Nat Commun 2019; 10:200. [PMID: 30643120 PMCID: PMC6331630 DOI: 10.1038/s41467-018-08060-6] [Citation(s) in RCA: 92] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2018] [Accepted: 12/11/2018] [Indexed: 11/09/2022] Open
Abstract
Turning graphene magnetic is a promising challenge to make it an active material for spintronics. Predictions state that graphene structures with specific shapes can spontaneously develop magnetism driven by Coulomb repulsion of π-electrons, but its experimental verification is demanding. Here, we report on the observation and manipulation of individual magnetic moments in graphene open-shell nanostructures on a gold surface. Using scanning tunneling spectroscopy, we detect the presence of single electron spins localized around certain zigzag sites of the carbon backbone via the Kondo effect. We find near-by spins coupled into a singlet ground state and quantify their exchange interaction via singlet-triplet inelastic electron excitations. Theoretical simulations picture how electron correlations result in spin-polarized radical states with the experimentally observed spatial distributions. Extra hydrogen atoms bound to radical sites quench their magnetic moment and switch the spin of the nanostructure in half-integer amounts. Our work demonstrates the intrinsic π-paramagnetism of graphene nanostructures.
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Affiliation(s)
- Jingcheng Li
- CIC nanoGUNE, 20018, Donostia-San Sebastián, Spain
| | - Sofia Sanz
- Donostia International Physics Center (DIPC), 20018, Donostia-San Sebastián, Spain
| | - Martina Corso
- Donostia International Physics Center (DIPC), 20018, Donostia-San Sebastián, Spain.,Centro de Física de Materiales CFM/MPC (CSIC-UPV/EHU), 20018, Donostia-San Sebastián, Spain
| | - Deung Jang Choi
- Donostia International Physics Center (DIPC), 20018, Donostia-San Sebastián, Spain.,Centro de Física de Materiales CFM/MPC (CSIC-UPV/EHU), 20018, Donostia-San Sebastián, Spain.,Ikerbasque, Basque Foundation for Science, 48013, Bilbao, Spain
| | - Diego Peña
- Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares (CiQUS), and Departamento de Química Orgánica, Universidade de Santiago de Compostela, Santiago de Compostela, 15782, Spain
| | - Thomas Frederiksen
- Donostia International Physics Center (DIPC), 20018, Donostia-San Sebastián, Spain.,Ikerbasque, Basque Foundation for Science, 48013, Bilbao, Spain
| | - Jose Ignacio Pascual
- CIC nanoGUNE, 20018, Donostia-San Sebastián, Spain. .,Ikerbasque, Basque Foundation for Science, 48013, Bilbao, Spain.
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22
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Calogero G, Papior NR, Kretz B, Garcia-Lekue A, Frederiksen T, Brandbyge M. Electron Transport in Nanoporous Graphene: Probing the Talbot Effect. Nano Lett 2019; 19:576-581. [PMID: 30539639 DOI: 10.1021/acs.nanolett.8b04616] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Electrons in graphene can show diffraction and interference phenomena fully analogous to light thanks to their Dirac-like energy dispersion. However, it is not clear how this optical analogy persists in nanostructured graphene, for example, with pores. Nanoporous graphene (NPG) consisting of linked graphene nanoribbons has recently been fabricated using molecular precursors and bottom-up assembly (Moreno et al. Science 2018, 360, 199). We predict that electrons propagating in NPG exhibit the interference Talbot effect, analogous to photons in coupled waveguides. Our results are obtained by parameter-free atomistic calculations of real-sized NPG samples based on seamlessly integrated density functional theory and tight-binding regions. We link the origins of this interference phenomenon to the band structure of the NPG. Most importantly, we demonstrate how the Talbot effect may be detected experimentally using dual-probe scanning tunneling microscopy. Talbot interference of electron waves in NPG or other related materials may open up new opportunities for future quantum electronics, computing, or sensing.
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Affiliation(s)
- Gaetano Calogero
- Department of Micro- and Nanotechnology, Center for Nanostructured Graphene (CNG) , Technical University of Denmark , DK-2800 Kongens Lyngby , Denmark
| | - Nick R Papior
- Department of Micro- and Nanotechnology, Center for Nanostructured Graphene (CNG) , Technical University of Denmark , DK-2800 Kongens Lyngby , Denmark
| | - Bernhard Kretz
- Institute of Theoretical Physics , University of Regensburg , 93040 Regensburg , Germany
| | - Aran Garcia-Lekue
- Donostia International Physics Center (DIPC) , 20018 San Sebastian , Spain
- Ikerbasque, Basque Foundation for Science , 48013 Bilbao , Spain
| | - Thomas Frederiksen
- Donostia International Physics Center (DIPC) , 20018 San Sebastian , Spain
- Ikerbasque, Basque Foundation for Science , 48013 Bilbao , Spain
| | - Mads Brandbyge
- Department of Micro- and Nanotechnology, Center for Nanostructured Graphene (CNG) , Technical University of Denmark , DK-2800 Kongens Lyngby , Denmark
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23
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de la Torre B, Švec M, Foti G, Krejčí O, Hapala P, Garcia-Lekue A, Frederiksen T, Zbořil R, Arnau A, Vázquez H, Jelínek P. Submolecular Resolution by Variation of the Inelastic Electron Tunneling Spectroscopy Amplitude and its Relation to the AFM/STM Signal. Phys Rev Lett 2017; 119:166001. [PMID: 29099201 DOI: 10.1103/physrevlett.119.166001] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2017] [Indexed: 05/27/2023]
Abstract
Here we show scanning tunneling microscopy (STM), noncontact atomic force microscopy (AFM), and inelastic electron tunneling spectroscopy (IETS) measurements on an organic molecule with a CO-terminated tip at 5 K. The high-resolution contrast observed simultaneously in all channels unambiguously demonstrates the common imaging mechanism in STM/AFM/IETS, related to the lateral bending of the CO-functionalized tip. The IETS spectroscopy reveals that the submolecular contrast at 5 K consists of both renormalization of vibrational frequency and variation of the amplitude of the IETS signal. This finding is also corroborated by first principles simulations. We extend accordingly the probe-particle AFM/STM/IETS model to include these two main ingredients necessary to reproduce the high-resolution IETS contrast. We also employ the first principles simulations to get more insight into a different response of frustrated translation and rotational modes of the CO tip during imaging.
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Affiliation(s)
- Bruno de la Torre
- Institute of Physics, Academy of Sciences of the Czech Republic, v.v.i., Cukrovarnická 10, 162 00 Prague, Czech Republic
- Regional Centre of Advanced Technologies and Materials, Palacký University, Šlechtitelů 27, 78371 Olomouc, Czech Republic
| | - Martin Švec
- Institute of Physics, Academy of Sciences of the Czech Republic, v.v.i., Cukrovarnická 10, 162 00 Prague, Czech Republic
- Regional Centre of Advanced Technologies and Materials, Palacký University, Šlechtitelů 27, 78371 Olomouc, Czech Republic
| | - Giuseppe Foti
- Institute of Physics, Academy of Sciences of the Czech Republic, v.v.i., Cukrovarnická 10, 162 00 Prague, Czech Republic
| | - Ondřej Krejčí
- Institute of Physics, Academy of Sciences of the Czech Republic, v.v.i., Cukrovarnická 10, 162 00 Prague, Czech Republic
- Faculty of Mathematics and Physics, Department of Surface and Plasma Science, Charles University, V Holešovičkách 2, 180 00 Prague, Czech Republic
| | - Prokop Hapala
- Institute of Physics, Academy of Sciences of the Czech Republic, v.v.i., Cukrovarnická 10, 162 00 Prague, Czech Republic
| | - Aran Garcia-Lekue
- Donostia International Physics Center (DIPC), Paseo Manuel Lardizabal 4, E-20018 San Sebastian, Spain
- Ikerbasque, Basque Foundation for Science, 48013 Bilbao, Spain
| | - Thomas Frederiksen
- Donostia International Physics Center (DIPC), Paseo Manuel Lardizabal 4, E-20018 San Sebastian, Spain
- Ikerbasque, Basque Foundation for Science, 48013 Bilbao, Spain
| | - Radek Zbořil
- Regional Centre of Advanced Technologies and Materials, Palacký University, Šlechtitelů 27, 78371 Olomouc, Czech Republic
| | - Andres Arnau
- Donostia International Physics Center (DIPC), Paseo Manuel Lardizabal 4, E-20018 San Sebastian, Spain
| | - Héctor Vázquez
- Institute of Physics, Academy of Sciences of the Czech Republic, v.v.i., Cukrovarnická 10, 162 00 Prague, Czech Republic
| | - Pavel Jelínek
- Institute of Physics, Academy of Sciences of the Czech Republic, v.v.i., Cukrovarnická 10, 162 00 Prague, Czech Republic
- Regional Centre of Advanced Technologies and Materials, Palacký University, Šlechtitelů 27, 78371 Olomouc, Czech Republic
- Donostia International Physics Center (DIPC), Paseo Manuel Lardizabal 4, E-20018 San Sebastian, Spain
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24
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Jasper-Tönnies T, Garcia-Lekue A, Frederiksen T, Ulrich S, Herges R, Berndt R. Conductance of a Freestanding Conjugated Molecular Wire. Phys Rev Lett 2017; 119:066801. [PMID: 28949604 DOI: 10.1103/physrevlett.119.066801] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2017] [Indexed: 06/07/2023]
Abstract
A freestanding molecular wire is placed vertically on Au(111) using a platform molecule and contacted by a scanning tunneling microscope. Despite the simplicity of the single-molecule junction, its conductance G reproducibly varies in a complex manner with the electrode separation. Transport calculations show that G is controlled by a deformation of the molecule, a symmetry mismatch between the tip and molecule orbitals, and the breaking of a C≡C triple in favor of a Au─C─C bond. This tip-controlled reversible bond formation or rupture alters the electronic spectrum of the junction and the states accessible for transport, resulting in an order of magnitude variation of the conductance.
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Affiliation(s)
- Torben Jasper-Tönnies
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany
| | - Aran Garcia-Lekue
- Donostia International Physics Center, DIPC, Paseo Manuel de Lardizabal 4, E-20018 Donostia-San Sebastián, Spain
- IKERBASQUE, Basque Foundation for Science, E-48013 Bilbao, Spain
| | - Thomas Frederiksen
- Donostia International Physics Center, DIPC, Paseo Manuel de Lardizabal 4, E-20018 Donostia-San Sebastián, Spain
- IKERBASQUE, Basque Foundation for Science, E-48013 Bilbao, Spain
| | - Sandra Ulrich
- Otto-Diels-Institut für Organische Chemie, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany
| | - Rainer Herges
- Otto-Diels-Institut für Organische Chemie, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany
| | - Richard Berndt
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany
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25
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Brandimarte P, Engelund M, Papior N, Garcia-Lekue A, Frederiksen T, Sánchez-Portal D. Publisher’s Note: “A tunable electronic beam splitter realized with crossed graphene nanoribbons” [J. Chem. Phys. 146, 092318 (2017)]. J Chem Phys 2017; 146:199902. [DOI: 10.1063/1.4983823] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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26
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Brandimarte P, Engelund M, Papior N, Garcia-Lekue A, Frederiksen T, Sánchez-Portal D. A tunable electronic beam splitter realized with crossed graphene nanoribbons. J Chem Phys 2017. [DOI: 10.1063/1.4974895] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Pedro Brandimarte
- Centro de Física de Materiales (CFM) CSIC-UPV/EHU, Paseo Manuel de Lardizabal 5, E-20018 Donostia-San Sebastián, Spain
| | - Mads Engelund
- Centro de Física de Materiales (CFM) CSIC-UPV/EHU, Paseo Manuel de Lardizabal 5, E-20018 Donostia-San Sebastián, Spain
| | - Nick Papior
- Institut Catala de Nanociencia i Nanotecnologia (ICN2), Campus de la UAB, Bellaterra (Barcelona), Spain
| | - Aran Garcia-Lekue
- Donostia International Physics Center, DIPC, Paseo Manuel de Lardizabal 4, E-20018 Donostia-San Sebastián, Spain
- IKERBASQUE, Basque Foundation for Science, E-48013 Bilbao, Spain
| | - Thomas Frederiksen
- Donostia International Physics Center, DIPC, Paseo Manuel de Lardizabal 4, E-20018 Donostia-San Sebastián, Spain
- IKERBASQUE, Basque Foundation for Science, E-48013 Bilbao, Spain
| | - Daniel Sánchez-Portal
- Centro de Física de Materiales (CFM) CSIC-UPV/EHU, Paseo Manuel de Lardizabal 5, E-20018 Donostia-San Sebastián, Spain
- Donostia International Physics Center, DIPC, Paseo Manuel de Lardizabal 4, E-20018 Donostia-San Sebastián, Spain
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27
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Engelund M, Godlewski S, Kolmer M, Zuzak R, Such B, Frederiksen T, Szymonski M, Sánchez-Portal D. The butterfly - a well-defined constant-current topography pattern on Si(001):H and Ge(001):H resulting from current-induced defect fluctuations. Phys Chem Chem Phys 2016; 18:19309-17. [PMID: 27375264 DOI: 10.1039/c6cp04031d] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Dangling bond (DB) arrays on Si(001):H and Ge(001):H surfaces can be patterned with atomic precision and they exhibit complex and rich physics making them interesting from both technological and fundamental perspectives. But their complex behavior often makes scanning tunneling microscopy (STM) images difficult to interpret and simulate. Recently it was shown that low-temperature imaging of unoccupied states of an unpassivated dimer on Ge(001):H results in a symmetric butterfly-like STM pattern, despite the fact that the equilibrium dimer configuration is expected to be a bistable, buckled geometry. Here, based on a thorough characterization of the low-bias switching events on Ge(001):H, we propose a new imaging model featuring a dynamical two-state rate equation. On both Si(001):H and Ge(001):H, this model allows us to reproduce the features of the observed symmetric empty-state images which strongly corroborates the idea that the patterns arise due to fast switching events and provides an insight into the relationship between the tunneling current and switching rates. We envision that our new imaging model can be applied to simulate other bistable systems where fluctuations arise from transiently charged electronic states.
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Affiliation(s)
- Mads Engelund
- Centro de Física de Materiales (CFM), CSIC-UPV/EHU, Paseo Manuel de Lardizabal 5, 20018, Donostia-San Sebastián, Spain.
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28
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Kitaguchi Y, Habuka S, Okuyama H, Hatta S, Aruga T, Frederiksen T, Paulsson M, Ueba H. Controlled switching of single-molecule junctions by mechanical motion of a phenyl ring. Beilstein J Nanotechnol 2015; 6:2088-95. [PMID: 26665080 PMCID: PMC4660945 DOI: 10.3762/bjnano.6.213] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/09/2015] [Accepted: 10/21/2015] [Indexed: 06/05/2023]
Abstract
Mechanical methods for single-molecule control have potential for wide application in nanodevices and machines. Here we demonstrate the operation of a single-molecule switch made functional by the motion of a phenyl ring, analogous to the lever in a conventional toggle switch. The switch can be actuated by dual triggers, either by a voltage pulse or by displacement of the electrode, and electronic manipulation of the ring by chemical substitution enables rational control of the on-state conductance. Owing to its simple mechanics, structural robustness, and chemical accessibility, we propose that phenyl rings are promising components in mechanical molecular devices.
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Affiliation(s)
- Yuya Kitaguchi
- Department of Chemistry, Graduate School of Science, Kyoto University, 606-8502 Kyoto, Japan
| | - Satoru Habuka
- Department of Chemistry, Graduate School of Science, Kyoto University, 606-8502 Kyoto, Japan
| | - Hiroshi Okuyama
- Department of Chemistry, Graduate School of Science, Kyoto University, 606-8502 Kyoto, Japan
| | - Shinichiro Hatta
- Department of Chemistry, Graduate School of Science, Kyoto University, 606-8502 Kyoto, Japan
| | - Tetsuya Aruga
- Department of Chemistry, Graduate School of Science, Kyoto University, 606-8502 Kyoto, Japan
| | - Thomas Frederiksen
- Donostia International Physics Center (DIPC), 20018 San Sebastián, Spain
- IKERBASQUE, Basque Foundation for Science, 48013 Bilbao, Spain
| | - Magnus Paulsson
- School of Computer Science, Physics and Mathematics, Linnaeus University, 391 82 Kalmar, Sweden
| | - Hiromu Ueba
- Division of Nano and New Functional Materials Science, Graduate School of Science and Engineering, University of Toyama, 930-8555 Toyama, Japan
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29
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Engelund M, Zuzak R, Godlewski S, Kolmer M, Frederiksen T, García-Lekue A, Sánchez-Portal D, Szymonski M. Tunneling spectroscopy of close-spaced dangling-bond pairs in Si(001):H. Sci Rep 2015; 5:14496. [PMID: 26404520 PMCID: PMC4585918 DOI: 10.1038/srep14496] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2015] [Accepted: 09/01/2015] [Indexed: 11/12/2022] Open
Abstract
We present a combined experimental and theoretical study of the electronic properties of close-spaced dangling-bond (DB) pairs in a hydrogen-passivated Si(001):H p-doped surface. Two types of DB pairs are considered, called “cross” and “line” structures. Our scanning tunneling spectroscopy (STS) data show that, although the spectra taken over different DBs in each pair exhibit a remarkable resemblance, they appear shifted by a constant energy that depends on the DB-pair type. This spontaneous asymmetry persists after repeated STS measurements. By comparison with density functional theory (DFT) calculations, we demonstrate that the magnitude of this shift and the relative position of the STS peaks can be explained by distinct charge states for each DB in the pair. We also explain how the charge state is modified by the presence of the scanning tunneling microscopy (STM) tip and the applied bias. Our results indicate that, using the STM tip, it is possible to control the charge state of individual DBs in complex structures, even if they are in close proximity. This observation might have important consequences for the design of electronic circuits and logic gates based on DBs in passivated silicon surfaces.
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Affiliation(s)
- Mads Engelund
- Centro de Física de Materiales CSIC-UPV/EHU, Paseo Manual de Lardizabal 5, E-20018, Donostia-San Sebastián, Spain
| | - Rafał Zuzak
- Center for Nanometer-Scale Science and Advanced Materials, NANOSAM, Faculty of Physics, Astronomy and Applied Computer Science, Jagiellonian University, PL-30-348, Krakow, Poland
| | - Szymon Godlewski
- Center for Nanometer-Scale Science and Advanced Materials, NANOSAM, Faculty of Physics, Astronomy and Applied Computer Science, Jagiellonian University, PL-30-348, Krakow, Poland
| | - Marek Kolmer
- Center for Nanometer-Scale Science and Advanced Materials, NANOSAM, Faculty of Physics, Astronomy and Applied Computer Science, Jagiellonian University, PL-30-348, Krakow, Poland
| | - Thomas Frederiksen
- Donostia International Physics Center, Paseo Manual de Lardizabal 4, 20018, Donostia-San Sebastián, Spain.,IKERBASQUE, Basque Foundation for Science, E-48013, Bilbao, Spain
| | - Aran García-Lekue
- Donostia International Physics Center, Paseo Manual de Lardizabal 4, 20018, Donostia-San Sebastián, Spain.,IKERBASQUE, Basque Foundation for Science, E-48013, Bilbao, Spain
| | - Daniel Sánchez-Portal
- Centro de Física de Materiales CSIC-UPV/EHU, Paseo Manual de Lardizabal 5, E-20018, Donostia-San Sebastián, Spain.,Donostia International Physics Center, Paseo Manual de Lardizabal 4, 20018, Donostia-San Sebastián, Spain
| | - Marek Szymonski
- Center for Nanometer-Scale Science and Advanced Materials, NANOSAM, Faculty of Physics, Astronomy and Applied Computer Science, Jagiellonian University, PL-30-348, Krakow, Poland
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30
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Smaali K, Desbief S, Foti G, Frederiksen T, Sanchez-Portal D, Arnau A, Nys JP, Leclère P, Vuillaume D, Clément N. On the mechanical and electronic properties of thiolated gold nanocrystals. Nanoscale 2015; 7:1809-1819. [PMID: 25518743 DOI: 10.1039/c4nr06180b] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We present a quantitative exploration, combining experiment and simulation, of the mechanical and electronic properties, as well as the modifications induced by an alkylthiolated coating, at the single nanoparticle (NP) level. We determined the response of the NPs to external pressure in a controlled manner using an atomic force microscope tip. We found a strong reduction in their Young's modulus, as compared to bulk gold, and a significant influence of strain on the electronic properties of the alkylthiolated NPs. Electron transport measurements of tiny molecular junctions (NP/alkylthiol/CAFM tip) show that the effective tunnelling barrier through the adsorbed monolayer strongly decreases by increasing the applied load, which translates in a remarkable and unprecedented increase in the tunnel current. These observations are successfully explained using simulations based on the finite element analysis (FEA) and first-principles calculations that permit one to consider the coupling between the mechanical response of the system and the electric dipole variations at the interface.
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Affiliation(s)
- K Smaali
- Institute of Electronics, Microelectronics and Nanotechnology, CNRS, Avenue Poincaré, 59652, Villeneuve d'Ascq, France.
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31
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Frederiksen T, Foti G, Scheurer F, Speisser V, Schull G. Chemical control of electrical contact to sp² carbon atoms. Nat Commun 2014; 5:3659. [PMID: 24736561 PMCID: PMC3997807 DOI: 10.1038/ncomms4659] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2013] [Accepted: 03/14/2014] [Indexed: 11/15/2022] Open
Abstract
Carbon-based nanostructures are attracting tremendous interest as components in ultrafast electronics and optoelectronics. The electrical interfaces to these structures play a crucial role for the electron transport, but the lack of control at the atomic scale can hamper device functionality and integration into operating circuitry. Here we study a prototype carbon-based molecular junction consisting of a single C60 molecule and probe how the electric current through the junction depends on the chemical nature of the foremost electrode atom in contact with the molecule. We find that the efficiency of charge injection to a C60 molecule varies substantially for the considered metallic species, and demonstrate that the relative strength of the metal-C bond can be extracted from our transport measurements. Our study further suggests that a single-C60 junction is a basic model to explore the properties of electrical contacts to meso- and macroscopic sp2 carbon structures. Understanding metal-molecule contacts is crucial for molecular electronic devices. Here, the authors use a C60-terminated scanning tunnelling tip to probe how the chemical nature of the contacting atom on the substrate electrode determines the transport properties.
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Affiliation(s)
- Thomas Frederiksen
- 1] Donostia International Physics Center (DIPC), Paseo Manuel de Lardizabal 4, E-20018 Donostia-San Sebastián, Spain [2] IKERBASQUE, Basque Foundation for Science, E-48011 Bilbao, Spain
| | - Giuseppe Foti
- 1] Donostia International Physics Center (DIPC), Paseo Manuel de Lardizabal 4, E-20018 Donostia-San Sebastián, Spain [2] Centro de Física de Materiales, Centro Mixto CSIC-UPV, Paseo Manuel de Lardizabal 5, E-20018 Donostia-San Sebastián, Spain
| | - Fabrice Scheurer
- Institut de Physique et Chimie des Matériaux de Strasbourg, UMR 7504 (CNRS-Université de Strasbourg), Strasbourg 67034, France
| | - Virginie Speisser
- Institut de Physique et Chimie des Matériaux de Strasbourg, UMR 7504 (CNRS-Université de Strasbourg), Strasbourg 67034, France
| | - Guillaume Schull
- Institut de Physique et Chimie des Matériaux de Strasbourg, UMR 7504 (CNRS-Université de Strasbourg), Strasbourg 67034, France
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32
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Kim Y, Garcia-Lekue A, Sysoiev D, Frederiksen T, Groth U, Scheer E. Charge transport in azobenzene-based single-molecule junctions. Phys Rev Lett 2012; 109:226801. [PMID: 23368145 DOI: 10.1103/physrevlett.109.226801] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2012] [Indexed: 05/21/2023]
Abstract
Azobenzene-derivative molecules change their conformation as a result of a cis-trans transition when exposed to ultraviolet or visible light irradiation and this is expected to induce a significant variation in the conductance of molecular devices. Despite extensive investigations carried out on this type of molecule, a detailed understanding of the charge transport for the two isomers is still lacking. We report a combined experimental and theoretical analysis of electron transport through azobenzene-derivative single-molecule break junctions with Au electrodes. Current-voltage and inelastic electron tunneling spectroscopy (IETS) measurements performed at 4.2 K are interpreted based on first-principles calculations of electron transmission and IETS spectra. This qualitative study unravels the origin of a slightly higher conductance of junctions with the cis isomer and demonstrates that IETS spectra of cis and trans forms show distinct vibrational fingerprints that can be used for identifying the isomer.
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Affiliation(s)
- Youngsang Kim
- Department of Physics, University of Konstanz, 78457 Konstanz, Germany
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33
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Heinrich BW, Rastei MV, Choi DJ, Frederiksen T, Limot L. Engineering negative differential conductance with the Cu(111) surface state. Phys Rev Lett 2011; 107:246801. [PMID: 22243018 DOI: 10.1103/physrevlett.107.246801] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2011] [Indexed: 05/31/2023]
Abstract
Low-temperature scanning tunneling microscopy and spectroscopy are employed to investigate electron tunneling from a C60-terminated tip into a Cu(111) surface. Tunneling between a C60 orbital and the Shockley surface states of copper is shown to produce negative differential conductance (NDC) contrary to conventional expectations. NDC can be tuned through barrier thickness or C60 orientation up to complete extinction. The orientation dependence of NDC is a result of a symmetry matching between the molecular tip and the surface states.
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Affiliation(s)
- B W Heinrich
- Institut de Physique et Chimie des Matériaux de Strasbourg, CNRS Université de Strasbourg, F-67034 Strasbourg, France
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34
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Kumagai T, Shiotari A, Okuyama H, Hatta S, Aruga T, Hamada I, Frederiksen T, Ueba H. H-atom relay reactions in real space. Nat Mater 2011; 11:167-172. [PMID: 22120414 DOI: 10.1038/nmat3176] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/10/2011] [Accepted: 10/20/2011] [Indexed: 05/31/2023]
Abstract
Hydrogen bonds are the path through which protons and hydrogen atoms can be transferred between molecules. The relay mechanism, in which H-atom transfer occurs in a sequential fashion along hydrogen bonds, plays an essential role in many functional compounds. Here we use the scanning tunnelling microscope to construct and operate a test-bed for real-space observation of H-atom relay reactions at a single-molecule level. We demonstrate that the transfer of H-atoms along hydrogen-bonded chains assembled on a Cu(110) surface is controllable and reversible, and is triggered by excitation of molecular vibrations induced by inelastic tunnelling electrons. The experimental findings are rationalized by ab initio calculations for adsorption geometry, active vibrational modes and reaction pathway, to reach a detailed microscopic picture of the elementary processes.
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Affiliation(s)
- T Kumagai
- Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
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35
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Schull G, Frederiksen T, Arnau A, Sánchez-Portal D, Berndt R. Atomic-scale engineering of electrodes for single-molecule contacts. Nat Nanotechnol 2011; 6:23-7. [PMID: 21076405 DOI: 10.1038/nnano.2010.215] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2010] [Accepted: 10/07/2010] [Indexed: 05/22/2023]
Abstract
The transport of charge through a conducting material depends on the intrinsic ability of the material to conduct current and on the charge injection efficiency at the contacts between the conductor and the electrodes carrying current to and from the material. According to theoretical considerations, this concept remains valid down to the limit of single-molecule junctions. Exploring this limit in experiments requires atomic-scale control of the junction geometry. Here we present a method for probing the current through a single C(60) molecule while changing, one by one, the number of atoms in the electrode that are in contact with the molecule. We show quantitatively that the contact geometry has a strong influence on the conductance. We also find a crossover from a regime in which the conductance is limited by charge injection at the contact to a regime in which the conductance is limited by scattering at the molecule. Thus, the concepts of 'good' and 'bad' contacts, commonly used in macro- and mesoscopic physics, can also be applied at the molecular scale.
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Affiliation(s)
- Guillaume Schull
- Institut de Physique et Chimie des Matériaux de Strasbourg, UMR 7504 (CNRS - Université de Strasbourg), 67034 Strasbourg, France.
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36
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Abstract
Conduction properties of nanoscale contacts can be studied using first-principles simulations. Such calculations give insight into details behind the conductance that is not readily available in experiments. For example, we may learn how the bonding conditions of a molecule to the electrodes affect the electronic transport. Here we describe key computational ingredients and discuss these in relation to simulations for scanning tunneling microscopy (STM) experiments with C60 molecules where the experimental geometry is well characterized. We then show how molecular dynamics simulations may be combined with transport calculations to study more irregular situations, such as the evolution of a nanoscale contact with the mechanically controllable break-junction technique. Finally we discuss calculations of inelastic electron tunnelling spectroscopy as a characterization technique that reveals information about the atomic arrangement and transport channels.
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Affiliation(s)
- Magnus Paulsson
- School of Computer Science, Physics and Mathematics, Linnaeus University, Kalmar, Sweden
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37
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Vitali L, Ohmann R, Kern K, Garcia-Lekue A, Frederiksen T, Sanchez-Portal D, Arnau A. Surveying molecular vibrations during the formation of metal-molecule nanocontacts. Nano Lett 2010; 10:657-660. [PMID: 20085284 DOI: 10.1021/nl903760k] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Molecular junctions have been characterized to determine the influence of the metal contact formation in the electron transport process through a single molecule. With inelastic electron tunneling spectroscopy and first-principles calculations, the vibration modes of a carbon monoxide molecule have been surveyed as a function of the distance from a copper electrode with unprecedented accuracy. We observe a continuous but nonlinear blue shift of the frustrated rotation mode in tunneling with decreasing distance followed by an abrupt softening upon contact formation. This indicates that the presence of the metal electrode sensibly alters the structural and conductive properties of the junction even without the formation of a strong chemical bond.
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Affiliation(s)
- Lucia Vitali
- Max-Planck-Institute fuer Festkoerperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, Germany.
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38
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Abstract
The charge flow from a single C(60) molecule to another one has been probed. The conformation and electronic states of both molecules on the contacting electrodes have been characterized using a cryogenic scanning tunneling microscope. While the contact conductance of a single molecule between two Cu electrodes can vary up to a factor of 3 depending on electrode geometry, the conductance of the C(60)-C(60) contact is consistently lower by 2 orders of magnitude. First-principles transport calculations reproduce the experimental results, allow a determination of the actual C(60)-C(60) distances, and identify the essential role of the intermolecular link in bi- and trimolecular chains.
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Affiliation(s)
- Guillaume Schull
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, D-24098 Kiel, Germany
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39
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Frederiksen T, Munuera C, Ocal C, Brandbyge M, Paulsson M, Sanchez-Portal D, Arnau A. Exploring the tilt-angle dependence of electron tunneling across molecular junctions of self-assembled alkanethiols. ACS Nano 2009; 3:2073-80. [PMID: 19637887 DOI: 10.1021/nn9000808] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Electronic transport mechanisms in molecular junctions are investigated by a combination of first-principles calculations and current-voltage measurements of several well-characterized structures. We study self-assembled layers of alkanethiols grown on Au(111) and form tunnel junctions by contacting the molecular layers with the tip of a conductive force microscope. Measurements done under low-load conditions permit us to obtain reliable tilt-angle and molecular length dependencies of the low-bias conductance through the alkanethiol layers. The observed dependence on tilt-angle is stronger for the longer molecular chains. Our calculations confirm the observed trends and explain them as a result of two mechanisms, namely, a previously proposed intermolecular tunneling enhancement as well as a hitherto overlooked tilt-dependent molecular gate effect.
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Affiliation(s)
- T Frederiksen
- Donostia International Physics Center (DIPC), Paseo Manuel de Lardizabal 4, San Sebastian 20018, Spain.
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40
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Paulsson M, Krag C, Frederiksen T, Brandbyge M. Conductance of alkanedithiol single-molecule junctions: a molecular dynamics study. Nano Lett 2009; 9:117-121. [PMID: 19061346 DOI: 10.1021/nl802643h] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
We study formation and conductance of alkanedithiol junctions using density functional based molecular dynamics. The formation involves straightening of the molecule, migration of thiol end-groups, and pulling out Au atoms. Plateaus are found in the low-bias conductance traces which decrease by 1 order of magnitude when gauche defects are present. We further show that the inelastic electron tunneling spectra depend on the junction geometry. In particular, our simulations suggest ways to identify gauche defects.
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Affiliation(s)
- Magnus Paulsson
- School of Pure and Applied Natural Sciences, University of Kalmar, 391 82 Kalmar, Sweden.
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41
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Paulsson M, Frederiksen T, Ueba H, Lorente N, Brandbyge M. Unified description of inelastic propensity rules for electron transport through nanoscale junctions. Phys Rev Lett 2008; 100:226604. [PMID: 18643440 DOI: 10.1103/physrevlett.100.226604] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2007] [Indexed: 05/26/2023]
Abstract
We present a method to analyze the results of first-principles based calculations of electronic currents including inelastic electron-phonon effects. This method allows us to determine the electronic and vibrational symmetries in play, and hence to obtain the so-called propensity rules for the studied systems. We show that only a few scattering states--namely those belonging to the most transmitting eigenchannels--need to be considered for a complete description of the electron transport. We apply the method on first-principles calculations of four different systems and obtain the propensity rules in each case.
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Affiliation(s)
- Magnus Paulsson
- Division of Physics, School of Pure and Applied Natural Science, University of Kalmar, 391 82 Kalmar, Sweden.
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42
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Abstract
The tip of a low-temperature scanning tunneling microscope is approached towards a C60 molecule adsorbed at a pentagon-hexagon bond on Cu(100) to form a tip-molecule contact. The conductance rapidly increases to approximately 0.25 conductance quanta in the transition region from tunneling to contact. Ab-initio calculations within density functional theory and nonequilibrium Green's function techniques explain the experimental data in terms of the conductance of an essentially undeformed C60. The conductance in the transition region is affected by structural fluctuations which modulate the tip-molecule distance.
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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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43
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Paulsson M, Frederiksen T, Brandbyge M. Phonon scattering in nanoscale systems: lowest order expansion of the current and power expressions. ACTA ACUST UNITED AC 2006. [DOI: 10.1088/1742-6596/35/1/022] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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44
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Paulsson M, Frederiksen T, Brandbyge M. Inelastic transport through molecules: comparing first-principles calculations to experiments. Nano Lett 2006; 6:258-62. [PMID: 16464046 DOI: 10.1021/nl052224r] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
We present calculations of the elastic and inelastic conductance through three different hydrocarbon molecules connected to gold electrodes. Our method is based on a combination of the nonequilibrium Green's function method with density functional theory. Vibrational effects in these molecular junctions were previously investigated experimentally by Kushmerick et al. (Nano Lett. 2004, 4, 639). Our results are in good agreement with the measurements and provide insights into (i) which vibrational modes are responsible for inelastic scattering, (ii) the width of the inelastic electron tunneling signals, and (iii) the mechanisms of heating and cooling of the vibrational modes induced by the coupling to the charge carriers.
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Affiliation(s)
- Magnus Paulsson
- MIC-Department of Micro and Nanotechnology, NanoDTU, Technical University of Denmark, Ørsteds Plads, Building 345E, DK-2800 Lyngby, Denmark
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45
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Frederiksen T, Brandbyge M, Lorente N, Jauho AP. Inelastic scattering and local heating in atomic gold wires. Phys Rev Lett 2004; 93:256601. [PMID: 15697922 DOI: 10.1103/physrevlett.93.256601] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/25/2004] [Indexed: 05/24/2023]
Abstract
We present a method for including inelastic scattering in a first-principles density-functional computational scheme for molecular electronics. As an application, we study two geometries of four-atom gold wires corresponding to two different values of strain and present results for nonlinear differential conductance vs device bias. Our theory is in quantitative agreement with experimental results and explains the experimentally observed mode selectivity. We also identify the signatures of phonon heating.
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Affiliation(s)
- Thomas Frederiksen
- MIC-Department of Micro and Nanotechnology, Technical University of Denmark, DK-2800 Lyngby, Denmark.
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46
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Jamil NE, Nguyen NT, Falk C, Frederiksen T, Deleuran BW. [Heavy white coats are not the cause of physicians' headaches and shoulder pain]. Ugeskr Laeger 2001; 163:7271-2. [PMID: 11797560] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/23/2023]
Abstract
The weight of doctors' white coats was examined and correlated to the degree of headache and muscle pain in the shoulders. The coat weight of doctors was 1.5 kg (1.1 kg-1.9 kg) (median with 25%-75% in parenthesis). The highest weight was found in the coats of young physicians 2.0 kg (1.7 kg-2.2 kg), which was higher than those of young surgeons. No correlation was seen in the degree of headache and muscle pain in the shoulders. With the long walking distances in hospitals, it would seem that internal medicine is not only an intellectually, but also a physically, demanding job.
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Affiliation(s)
- N E Jamil
- Odense Universitetshospital, medicinsk afdeling C
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47
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Frederiksen T. [Kirsten Lyloff on death causes of German immigrant children]. Ugeskr Laeger 2000; 162:2765. [PMID: 10827554] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/16/2023]
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48
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Abstract
A behavioural method of habit reversal, in combination with a hydrocortisone cream, was compared with the use of cream alone in the treatment of 17 patients with atopic dermatitis. The patients were assigned randomly to two groups, one of which received the combination treatment and the other regular ointment treatment. The patients' skin status was assessed before and after treatment, and the patients recorded their scratching during the study. Both groups improved, but the group which received habit-reversal therapy improved significantly more. A strong correlation was found between reduction in scratching and improvement in skin status.
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49
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Laursen NP, Frederiksen T. [Traumatic lesions of the liver. II. Investigation of an operative technique by animal experiments]. Ugeskr Laeger 1973; 135:2614-6. [PMID: 4782903] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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50
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Dyreborg U, Frederiksen T, Ingstrup H, Madsen CM, Reiter S. [The diagnostic value of mammography in patients with palpable indurations in the breasts]. Nord Med 1971; 86:1115-6. [PMID: 5127578] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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