1
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Kumar R, Srivastav SK, Roy U, Park J, Spånslätt C, Watanabe K, Taniguchi T, Gefen Y, Mirlin AD, Das A. Electrical noise spectroscopy of magnons in a quantum Hall ferromagnet. Nat Commun 2024; 15:4998. [PMID: 38866830 PMCID: PMC11169481 DOI: 10.1038/s41467-024-49446-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2023] [Accepted: 06/05/2024] [Indexed: 06/14/2024] Open
Abstract
Collective spin-wave excitations, magnons, are promising quasi-particles for next-generation spintronics devices, including platforms for information transfer. In a quantum Hall ferromagnets, detection of these charge-neutral excitations relies on the conversion of magnons into electrical signals in the form of excess electrons and holes, but if the excess electron and holes are equal, detecting an electrical signal is challenging. In this work, we overcome this shortcoming by measuring the electrical noise generated by magnons. We use the symmetry-broken quantum Hall ferromagnet of the zeroth Landau level in graphene to launch magnons. Absorption of these magnons creates excess noise above the Zeeman energy and remains finite even when the average electrical signal is zero. Moreover, we formulate a theoretical model in which the noise is produced by equilibration between edge channels and propagating magnons. Our model also allows us to pinpoint the regime of ballistic magnon transport in our device.
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Affiliation(s)
- Ravi Kumar
- Department of Physics, Indian Institute of Science, Bangalore, 560012, India
| | | | - Ujjal Roy
- Department of Physics, Indian Institute of Science, Bangalore, 560012, India
| | - Jinhong Park
- Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology, 76021, Karlsruhe, Germany
- Institut für Theorie der Kondensierten Materie, Karlsruhe Institute of Technology, 76128, Karlsruhe, Germany
| | - Christian Spånslätt
- Department of Microtechnology and Nanoscience (MC2), Chalmers University of Technology, S-412 96, Göteborg, Sweden
| | - K Watanabe
- National Institute of Material Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - T Taniguchi
- National Institute of Material Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - Yuval Gefen
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, 76100, Israel
| | - Alexander D Mirlin
- Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology, 76021, Karlsruhe, Germany
- Institut für Theorie der Kondensierten Materie, Karlsruhe Institute of Technology, 76128, Karlsruhe, Germany
| | - Anindya Das
- Department of Physics, Indian Institute of Science, Bangalore, 560012, India.
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2
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van Weerdenburg WJ, Osterhage H, Christianen R, Junghans K, Domínguez E, Kappen HJ, Khajetoorians AA. Stochastic Syncing in Sinusoidally Driven Atomic Orbital Memory. ACS NANO 2024; 18:4840-4846. [PMID: 38291572 PMCID: PMC10867893 DOI: 10.1021/acsnano.3c09635] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/05/2023] [Revised: 01/11/2024] [Accepted: 01/25/2024] [Indexed: 02/01/2024]
Abstract
Stochastically fluctuating multiwell systems are a promising route toward physical implementations of energy-based machine learning and neuromorphic hardware. One of the challenges is finding tunable material platforms that exhibit such multiwell behavior and understanding how complex dynamic input signals influence their stochastic response. One such platform is the recently discovered atomic Boltzmann machine, where each stochastic unit is represented by a binary orbital memory state of an individual atom. Here, we investigate the stochastic response of binary orbital memory states to sinusoidal input voltages. Using scanning tunneling microscopy, we investigated orbital memory derived from individual Fe and Co atoms on black phosphorus. We quantify the state residence times as a function of various input parameters such as frequency, amplitude, and offset voltage. The state residence times for both species, when driven by a sinusoidal signal, exhibit synchronization that can be quantitatively modeled by a Poisson process based on the switching rates in the absence of a sinusoidal signal. For individual Fe atoms, we also observe a frequency-dependent response of the state favorability, which can be tuned by the input parameters. In contrast to Fe, there is no significant frequency dependence in the state favorability for individual Co atoms. Based on the Poisson model, the difference in the response of the state favorability can be traced to the difference in the voltage-dependent switching rates of the two different species. This platform provides a tunable way to induce population changes in stochastic systems and provides a foundation toward understanding driven stochastic multiwell systems.
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Affiliation(s)
| | - Hermann Osterhage
- Institute
for Molecules and Materials, Radboud University, 6525 AJ Nijmegen, The Netherlands
| | - Ruben Christianen
- Institute
for Molecules and Materials, Radboud University, 6525 AJ Nijmegen, The Netherlands
| | - Kira Junghans
- Institute
for Molecules and Materials, Radboud University, 6525 AJ Nijmegen, The Netherlands
| | - Eduardo Domínguez
- Donders
Institute for Neuroscience, Radboud University, 6525 AJ Nijmegen, The Netherlands
| | - Hilbert J. Kappen
- Donders
Institute for Neuroscience, Radboud University, 6525 AJ Nijmegen, The Netherlands
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3
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Gozlinski T, Henn M, Wolf T, Le Tacon M, Schmalian J, Wulfhekel W. Bosonic excitation spectra of superconductingBi2Sr2CaCu2O8+δandYBa2Cu3O6+xextracted from scanning tunneling spectra. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2024; 36:175601. [PMID: 38194720 DOI: 10.1088/1361-648x/ad1ca8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2023] [Accepted: 01/09/2024] [Indexed: 01/11/2024]
Abstract
A detailed interpretation of scanning tunneling spectra obtained on unconventional superconductors enables one to gain information on the pairing boson. Decisive for this approach are inelastic tunneling events. Due to the lack of momentum conservation in tunneling from or to the sharp tip, those are enhanced in the geometry of a scanning tunneling microscope compared to planar tunnel junctions. This work extends the method of obtaining the bosonic excitation spectrum by deconvolution from tunneling spectra to nodald-wave superconductors. In particular, scanning tunneling spectra of slightly underdopedBi2Sr2CaCu2O8+δwith aTcof 82 K and optimally dopedYBa2Cu3O6+xwith aTcof 92 K reveal a resonance mode in their bosonic excitation spectrum atΩres≈63 meVandΩres≈61 meVrespectively. In both cases, the overall shape of the bosonic excitation spectrum is indicative of predominant spin scattering with a resonant mode atΩres<2Δand overdamped spin fluctuations for energies larger than 2Δ. To perform the deconvolution of the experimental data, we implemented an efficient iterative algorithm that significantly enhances the reliability of our analysis.
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Affiliation(s)
- Thomas Gozlinski
- Physikalisches Institut, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany
| | - Mirjam Henn
- Physikalisches Institut, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany
| | - Thomas Wolf
- Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen, Germany
| | - Matthieu Le Tacon
- Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen, Germany
| | - Jörg Schmalian
- Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen, Germany
- Institute for Theory of Condensed Matter, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany
| | - Wulf Wulfhekel
- Physikalisches Institut, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany
- Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen, Germany
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4
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Liang K, Bi L, Zhu Q, Zhou H, Li S. Ultrafast Dynamics Revealed with Time-Resolved Scanning Tunneling Microscopy: A Review. ACS APPLIED OPTICAL MATERIALS 2023; 1:924-938. [PMID: 37260467 PMCID: PMC10227725 DOI: 10.1021/acsaom.2c00169] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Accepted: 02/23/2023] [Indexed: 06/02/2023]
Abstract
A scanning tunneling microscope (STM) capable of performing pump-probe spectroscopy integrates unmatched atomic-scale resolution with high temporal resolution. In recent years, the union of electronic, terahertz, or visible/near-infrared pulses with STM has contributed to our understanding of the atomic-scale processes that happen between milliseconds and attoseconds. This time-resolved STM (TR-STM) technique is evolving into an unparalleled approach for exploring the ultrafast nuclear, electronic, or spin dynamics of molecules, low-dimensional structures, and material surfaces. Here, we review the recent advancements in TR-STM; survey its application in measuring the dynamics of three distinct systems, nucleus, electron, and spin; and report the studies on these transient processes in a series of materials. Besides the discussion on state-of-the-art techniques, we also highlight several emerging research topics about the ultrafast processes in nanoscale objects where we anticipate that the TR-STM can help broaden our knowledge.
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Affiliation(s)
- Kangkai Liang
- Department
of Chemistry and Biochemistry, University
of California, San Diego, La Jolla, California 92093-0309, United States
- Materials
Science and Engineering Program, University
of California, San Diego, La Jolla, California 92093-0418, United States
| | - Liya Bi
- Department
of Chemistry and Biochemistry, University
of California, San Diego, La Jolla, California 92093-0309, United States
- Materials
Science and Engineering Program, University
of California, San Diego, La Jolla, California 92093-0418, United States
| | - Qingyi Zhu
- Department
of Chemistry and Biochemistry, University
of California, San Diego, La Jolla, California 92093-0309, United States
| | - Hao Zhou
- Department
of Chemistry and Biochemistry, University
of California, San Diego, La Jolla, California 92093-0309, United States
- Materials
Science and Engineering Program, University
of California, San Diego, La Jolla, California 92093-0418, United States
| | - Shaowei Li
- Department
of Chemistry and Biochemistry, University
of California, San Diego, La Jolla, California 92093-0309, United States
- Materials
Science and Engineering Program, University
of California, San Diego, La Jolla, California 92093-0418, United States
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5
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Ganguli SC, Aapro M, Kezilebieke S, Amini M, Lado JL, Liljeroth P. Visualization of Moiré Magnons in Monolayer Ferromagnet. NANO LETTERS 2023; 23:3412-3417. [PMID: 37040471 PMCID: PMC10141560 DOI: 10.1021/acs.nanolett.3c00417] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/02/2023] [Revised: 04/04/2023] [Indexed: 06/19/2023]
Abstract
Two-dimensional magnetic materials provide an ideal platform to explore collective many-body excitations associated with spin fluctuations. In particular, it should be feasible to explore, manipulate, and ultimately design magnonic excitations in two-dimensional van der Waals magnets in a controllable way. Here we demonstrate the emergence of moiré magnon excitations, stemming from the interplay of spin-excitations in monolayer CrBr3 and the moiré pattern arising from the lattice mismatch with the underlying substrate. The existence of moiré magnons is further confirmed via inelastic quasiparticle interference, showing the appearance of a dispersion pattern correlated with the moiré length scale. Our results provide a direct visualization in real-space of the dispersion of moiré magnons, demonstrating the versatility of moiré patterns in creating emergent many-body excitations.
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Affiliation(s)
| | - Markus Aapro
- Department
of Applied Physics, Aalto University, FI-00076 Aalto, Finland
| | - Shawulienu Kezilebieke
- Department
of Physics, Department of Chemistry and Nanoscience Center, University of Jyväskylä, FI-40014 Jyväskylä, Finland
| | - Mohammad Amini
- Department
of Applied Physics, Aalto University, FI-00076 Aalto, Finland
| | - Jose L. Lado
- Department
of Applied Physics, Aalto University, FI-00076 Aalto, Finland
| | - Peter Liljeroth
- Department
of Applied Physics, Aalto University, FI-00076 Aalto, Finland
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6
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Chen G, Song F, Lado JL. Topological Spin Excitations in Non-Hermitian Spin Chains with a Generalized Kernel Polynomial Algorithm. PHYSICAL REVIEW LETTERS 2023; 130:100401. [PMID: 36962053 DOI: 10.1103/physrevlett.130.100401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/18/2022] [Revised: 12/09/2022] [Accepted: 02/06/2023] [Indexed: 06/18/2023]
Abstract
Spectral functions of non-Hermitian Hamiltonians can reveal the existence of topologically nontrivial line gaps and the associated topological edge modes. However, the computation of spectral functions in a non-Hermitian many-body system remains an open challenge. Here, we put forward a numerical approach to compute spectral functions of a non-Hermitian many-body Hamiltonian based on the kernel polynomial method and the matrix-product state formalism. We show that the local spectral functions computed with our algorithm reveal topological spin excitations in a non-Hermitian spin model, faithfully reflecting the nontrivial line gap topology in a many-body model. We further show that the algorithm works in the presence of the non-Hermitian skin effect. Our method offers an efficient way to compute local spectral functions in non-Hermitian many-body systems with tensor networks, allowing us to characterize line gap topology in non-Hermitian quantum many-body models.
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Affiliation(s)
- Guangze Chen
- Department of Applied Physics, Aalto University, 02150 Espoo, Finland
| | - Fei Song
- Institute for Advanced Study, Tsinghua University, Beijing 100084, China
| | - Jose L Lado
- Department of Applied Physics, Aalto University, 02150 Espoo, Finland
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7
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Brinker S, Küster F, Parkin SSP, Sessi P, Lounis S. Anomalous excitations of atomically crafted quantum magnets. SCIENCE ADVANCES 2022; 8:eabi7291. [PMID: 35080983 PMCID: PMC8791613 DOI: 10.1126/sciadv.abi7291] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Accepted: 12/06/2021] [Indexed: 06/14/2023]
Abstract
High-energy resolution spectroscopic studies of quantum magnets proved extremely valuable in accessing magnetodynamics quantities, such as energy barriers, magnetic interactions, and lifetime of excited states. Here, we investigate a previously unexplored flavor of low-energy spin excitations for quantum spins coupled to an electron bath. In sharp contrast to the usual tunneling signature of two steps symmetrically centered around the Fermi level, we find a single step in the conductance. Combining time-dependent and many-body perturbation theories, magnetic field-dependent tunneling spectra are explained as the result of an interplay between weak magnetic anisotropy energy, magnetic interactions, and Stoner-like electron-hole excitations that are strongly dependent on the magnetic states of the nanostructures. The results are rationalized in terms of a noncollinear magnetic ground state and the dominance of ferro- and antiferromagnetic interactions. The atomically crafted nanomagnets offer an appealing model for the exploration of electrically pumped spin systems.
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Affiliation(s)
- Sascha Brinker
- Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, Jülich D-52425, Germany
| | - Felix Küster
- Max Planck Institute of Microstructure Physics, Halle 06120, Germany
| | | | - Paolo Sessi
- Max Planck Institute of Microstructure Physics, Halle 06120, Germany
| | - Samir Lounis
- Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, Jülich D-52425, Germany
- Faculty of Physics, University of Duisburg-Essen and CENIDE, 47053 Duisburg, Germany
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8
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Chen Y, Bae Y, Heinrich AJ. Harnessing the Quantum Behavior of Spins on Surfaces. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2022:e2107534. [PMID: 34994026 DOI: 10.1002/adma.202107534] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2021] [Revised: 12/28/2021] [Indexed: 06/14/2023]
Abstract
The desire to control and measure individual quantum systems such as atoms and ions in a vacuum has led to significant scientific and engineering developments in the past decades that form the basis of today's quantum information science. Single atoms and molecules on surfaces, on the other hand, are heavily investigated by physicists, chemists, and material scientists in search of novel electronic and magnetic functionalities. These two paths crossed in 2015 when it was first clearly demonstrated that individual spins on a surface can be coherently controlled and read out in an all-electrical fashion. The enabling technique is a combination of scanning tunneling microscopy (STM) and electron spin resonance, which offers unprecedented coherent controllability at the Angstrom length scale. This review aims to illustrate the essential ingredients that allow the quantum operations of single spins on surfaces. Three domains of applications of surface spins, namely quantum sensing, quantum control, and quantum simulation, are discussed with physical principles explained and examples presented. Enabled by the atomically-precise fabrication capability of STM, single spins on surfaces might one day lead to the realization of quantum nanodevices and artificial quantum materials at the atomic scale.
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Affiliation(s)
- Yi Chen
- Center for Quantum Nanoscience, Institute for Basic Science (IBS), Seoul, 03760, Korea
- Department of Physics, Ewha Womans University, Seoul, 03760, Korea
| | - Yujeong Bae
- Center for Quantum Nanoscience, Institute for Basic Science (IBS), Seoul, 03760, Korea
- Department of Physics, Ewha Womans University, Seoul, 03760, Korea
| | - Andreas J Heinrich
- Center for Quantum Nanoscience, Institute for Basic Science (IBS), Seoul, 03760, Korea
- Department of Physics, Ewha Womans University, Seoul, 03760, Korea
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9
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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: 45] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [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 OrgánicaUniversidade de Santiago de Compostela15782-Santiago de CompostelaSpain
| | | | | | - Francisco Romero Lara
- CIC nanoGUNE-BRTA20018Donostia-San SebastiánSpain
- Centro de Física de Materiales CSIC/UPV-EHU-Materials Physics Center20018Donostia-San SebastiánSpain
| | - Sofía Sanz
- Donostia International Physics Center (DIPC)20018Donostia-San SebastiánSpain
| | - Dulce Rey
- Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares (CiQUS) and Departamento de Química OrgánicaUniversidade de Santiago de Compostela15782-Santiago de CompostelaSpain
| | - Martina Corso
- Centro de Física de Materiales CSIC/UPV-EHU-Materials Physics Center20018Donostia-San SebastiánSpain
- Donostia International Physics Center (DIPC)20018Donostia-San SebastiánSpain
| | - Thomas Frederiksen
- Donostia International Physics Center (DIPC)20018Donostia-San SebastiánSpain
- IkerbasqueBasque Foundation for Science48013BilbaoSpain
| | - Jose Ignacio Pascual
- CIC nanoGUNE-BRTA20018Donostia-San SebastiánSpain
- IkerbasqueBasque Foundation for Science48013BilbaoSpain
| | - Diego Peña
- Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares (CiQUS) and Departamento de Química OrgánicaUniversidade de Santiago de Compostela15782-Santiago de CompostelaSpain
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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. [DOI: 10.1002/ange.202108301] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [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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11
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Mishra S, Catarina G, Wu F, Ortiz R, Jacob D, Eimre K, Ma J, Pignedoli CA, Feng X, Ruffieux P, Fernández-Rossier J, Fasel R. Observation of fractional edge excitations in nanographene spin chains. Nature 2021; 598:287-292. [PMID: 34645998 DOI: 10.1038/s41586-021-03842-3] [Citation(s) in RCA: 78] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Accepted: 07/20/2021] [Indexed: 11/09/2022]
Abstract
Fractionalization is a phenomenon in which strong interactions in a quantum system drive the emergence of excitations with quantum numbers that are absent in the building blocks. Outstanding examples are excitations with charge e/3 in the fractional quantum Hall effect1,2, solitons in one-dimensional conducting polymers3,4 and Majorana states in topological superconductors5. Fractionalization is also predicted to manifest itself in low-dimensional quantum magnets, such as one-dimensional antiferromagnetic S = 1 chains. The fundamental features of this system are gapped excitations in the bulk6 and, remarkably, S = 1/2 edge states at the chain termini7-9, leading to a four-fold degenerate ground state that reflects the underlying symmetry-protected topological order10,11. Here, we use on-surface synthesis12 to fabricate one-dimensional spin chains that contain the S = 1 polycyclic aromatic hydrocarbon triangulene as the building block. Using scanning tunnelling microscopy and spectroscopy at 4.5 K, we probe length-dependent magnetic excitations at the atomic scale in both open-ended and cyclic spin chains, and directly observe gapped spin excitations and fractional edge states therein. Exact diagonalization calculations provide conclusive evidence that the spin chains are described by the S = 1 bilinear-biquadratic Hamiltonian in the Haldane symmetry-protected topological phase. Our results open a bottom-up approach to study strongly correlated phases in purely organic materials, with the potential for the realization of measurement-based quantum computation13.
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Affiliation(s)
- Shantanu Mishra
- Empa-Swiss Federal Laboratories for Materials Science and Technology, Dübendorf, Switzerland.,IBM Research-Zurich, Rüschlikon, Switzerland
| | - Gonçalo Catarina
- International Iberian Nanotechnology Laboratory, Braga, Portugal.,University of Alicante, Sant Vicent del Raspeig, Spain
| | - Fupeng Wu
- Technical University of Dresden, Dresden, Germany
| | - Ricardo Ortiz
- University of Alicante, Sant Vicent del Raspeig, Spain
| | - David Jacob
- University of the Basque Country, San Sebastián, Spain.,IKERBASQUE, Basque Foundation for Science, Bilbao, Spain
| | - Kristjan Eimre
- Empa-Swiss Federal Laboratories for Materials Science and Technology, Dübendorf, Switzerland
| | - Ji Ma
- Technical University of Dresden, Dresden, Germany
| | - Carlo A Pignedoli
- Empa-Swiss Federal Laboratories for Materials Science and Technology, Dübendorf, Switzerland
| | - Xinliang Feng
- Technical University of Dresden, Dresden, Germany. .,Max Planck Institute of Microstructure Physics, Halle, Germany.
| | - Pascal Ruffieux
- Empa-Swiss Federal Laboratories for Materials Science and Technology, Dübendorf, Switzerland.
| | | | - Roman Fasel
- Empa-Swiss Federal Laboratories for Materials Science and Technology, Dübendorf, Switzerland.,University of Bern, Bern, Switzerland
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12
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Veldman LM, Farinacci L, Rejali R, Broekhoven R, Gobeil J, Coffey D, Ternes M, Otte AF. Free coherent evolution of a coupled atomic spin system initialized by electron scattering. Science 2021; 372:964-968. [PMID: 34045351 DOI: 10.1126/science.abg8223] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Revised: 02/19/2021] [Accepted: 04/23/2021] [Indexed: 11/02/2022]
Abstract
Full insight into the dynamics of a coupled quantum system depends on the ability to follow the effect of a local excitation in real-time. Here, we trace the free coherent evolution of a pair of coupled atomic spins by means of scanning tunneling microscopy. Rather than using microwave pulses, we use a direct-current pump-probe scheme to detect the local magnetization after a current-induced excitation performed on one of the spins. By making use of magnetic interaction with the probe tip, we are able to tune the relative precession of the spins. We show that only if their Larmor frequencies match, the two spins can entangle, causing angular momentum to be swapped back and forth. These results provide insight into the locality of electron spin scattering and set the stage for controlled migration of a quantum state through an extended spin lattice.
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Affiliation(s)
- Lukas M Veldman
- Department of Quantum Nanoscience, Kavli Institute of Nanoscience, Delft University of Technology, 2628 CJ Delft, the Netherlands
| | - Laëtitia Farinacci
- Department of Quantum Nanoscience, Kavli Institute of Nanoscience, Delft University of Technology, 2628 CJ Delft, the Netherlands
| | - Rasa Rejali
- Department of Quantum Nanoscience, Kavli Institute of Nanoscience, Delft University of Technology, 2628 CJ Delft, the Netherlands
| | - Rik Broekhoven
- Department of Quantum Nanoscience, Kavli Institute of Nanoscience, Delft University of Technology, 2628 CJ Delft, the Netherlands
| | - Jérémie Gobeil
- Department of Quantum Nanoscience, Kavli Institute of Nanoscience, Delft University of Technology, 2628 CJ Delft, the Netherlands
| | - David Coffey
- Department of Quantum Nanoscience, Kavli Institute of Nanoscience, Delft University of Technology, 2628 CJ Delft, the Netherlands
| | - Markus Ternes
- RWTH Aachen University, Institute of Physics, D-52074 Aachen, Germany.,Peter-Grünberg-Institute, Forschungszentrum Jülich, D-52425 Jülich, Germany
| | - Alexander F Otte
- Department of Quantum Nanoscience, Kavli Institute of Nanoscience, Delft University of Technology, 2628 CJ Delft, the Netherlands.
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13
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Malavolti L, McMurtrie G, Rolf-Pissarczyk S, Yan S, Burgess JAJ, Loth S. Minimally invasive spin sensing with scanning tunneling microscopy. NANOSCALE 2020; 12:11619-11626. [PMID: 32435779 DOI: 10.1039/c9nr10252c] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Minimizing the invasiveness of scanning tunneling measurements is paramount for observation of the magnetic properties of unperturbed atomic-scale objects. We show that the invasiveness of STM inspection on few-atom spin systems can be drastically reduced by means of a remote detection scheme, which makes use of a sensor spin weakly coupled to the sensed object. By comparing direct and remote measurements we identify the relevant perturbations caused by the local probe. For direct inspection we find that tunneling electrons strongly perturb the investigated object even for currents as low as 3 pA. Electrons injected into the sensor spin induce perturbations with much reduced probability. The sensing scheme uses standard differential conductance measurements, and is decoupled both by its non-local nature, and by dynamic decoupling due to the significantly different time scales at which the sensor and sensed object evolve. The latter makes it possible to effectively remove static interactions between the sensed object and the spin sensor while still allowing the spin sensing. In this way we achieve measurements with a reduction in perturbative effects of up to 100 times relative to direct scanning tunneling measurements, which enables minimally invasive measurements of a few-atom magnet's fragile spin states with STM.
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Affiliation(s)
- Luigi Malavolti
- Institute for Functional Matter and Quantum Technologies, University of Stuttgart, 70569 Stuttgart, Germany. and Max Planck Institute for the Structure and Dynamics of Matter, 22761 Hamburg, Germany and Max Planck Institute for Solid State Research, 70569 Stuttgart, Germany
| | - Gregory McMurtrie
- Institute for Functional Matter and Quantum Technologies, University of Stuttgart, 70569 Stuttgart, Germany. and Max Planck Institute for the Structure and Dynamics of Matter, 22761 Hamburg, Germany and Max Planck Institute for Solid State Research, 70569 Stuttgart, Germany
| | - Steffen Rolf-Pissarczyk
- Max Planck Institute for the Structure and Dynamics of Matter, 22761 Hamburg, Germany and Max Planck Institute for Solid State Research, 70569 Stuttgart, Germany
| | - Shichao Yan
- Max Planck Institute for the Structure and Dynamics of Matter, 22761 Hamburg, Germany and Max Planck Institute for Solid State Research, 70569 Stuttgart, Germany and School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Jacob A J Burgess
- Max Planck Institute for the Structure and Dynamics of Matter, 22761 Hamburg, Germany and Max Planck Institute for Solid State Research, 70569 Stuttgart, Germany and Department of Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba, Canada R3T 2N2
| | - Sebastian Loth
- Institute for Functional Matter and Quantum Technologies, University of Stuttgart, 70569 Stuttgart, Germany. and Max Planck Institute for the Structure and Dynamics of Matter, 22761 Hamburg, Germany and Max Planck Institute for Solid State Research, 70569 Stuttgart, Germany
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14
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Garlatti E, Allodi G, Bordignon S, Bordonali L, Timco GA, Winpenny REP, Lascialfari A, De Renzi R, Carretta S. Breaking the ring: 53Cr-NMR on the Cr 8Cd molecular nanomagnet. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:244003. [PMID: 32079012 DOI: 10.1088/1361-648x/ab7872] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
An accurate experimental characterization of finite antiferromagnetic (AF) spin chains is crucial for controlling and manipulating their magnetic properties and quantum states for potential applications in spintronics or quantum computation. In particular, finite AF chains are expected to show a different magnetic behaviour depending on their length and topology. Molecular AF rings are able to combine the quantum-magnetic behaviour of AF chains with a very remarkable tunability of their topological and geometrical properties. In this work we measure the 53Cr-NMR spectra of the Cr8Cd ring to study the local spin densities on the Cr sites. Cr8Cd can in fact be considered a model system of a finite AF open chain with an even number of spins. The NMR resonant frequencies are in good agreement with the theoretical local spin densities, by assuming a core polarization field A C = -12.7 T μ B -1. Moreover, these NMR results confirm the theoretically predicted non-collinear spin arrangement along the Cr8Cd ring, which is typical of an even-open AF spin chain.
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Affiliation(s)
- E Garlatti
- Dipartimento di Science Matematiche, Fisiche e Informatiche, Università di Parma, Parco Area delle Scienze 7/A, 43124 Parma, Italy
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15
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Kozanecki M, Rudowicz C. Importance of the fourth-rank zero field splitting parameters for Fe 2+ ( S = 2) adatoms on the CuN/Cu(100) surface evidenced by their determination based on DFT and experimental data. Phys Chem Chem Phys 2020; 22:19837-19844. [DOI: 10.1039/d0cp02986f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Equations allow to determine 2nd- and 4th-rank ZFSPs (Bkq) based on spin energy levels (λi) at B = 0. This method is applied to Fe2+ (S = 2) adatoms on CuN/Cu(100) surface using DFT and experimental data. Relative importance of ZFSPs is analyzed.
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Affiliation(s)
- Michał Kozanecki
- Faculty of Chemistry
- Adam Mickiewicz University
- 61-614 Poznań
- Poland
| | - Czesław Rudowicz
- Faculty of Chemistry
- Adam Mickiewicz University
- 61-614 Poznań
- Poland
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16
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Friedlein J, Harm J, Lindner P, Bargsten L, Bazarnik M, Krause S, Wiesendanger R. A radio-frequency spin-polarized scanning tunneling microscope. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2019; 90:123705. [PMID: 31893779 DOI: 10.1063/1.5104317] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2019] [Accepted: 11/29/2019] [Indexed: 06/10/2023]
Abstract
A scanning tunneling microscope for spin-resolved studies of dynamic systems is presented. The cryogenic setup allows the scanning tunneling microscope to achieve a cutoff frequency beyond 26 GHz at the tunnel junction and to be operable at temperatures of 1.1 K-100 K in a magnetic field of up to 3 T. For this purpose, the microscope and its wiring as well as the associated cryostat system were specially designed and manufactured. For sample preparation, an ultrahigh vacuum system was developed, which is equipped with modular preparation platforms. Measurements showing the characteristics of the scanning tunneling microscope in the time and frequency domain are presented. As a proof of concept, experimental data of the Pd/Fe/Ir(111) sample system at 95 K in a magnetic field of 3 T are presented.
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Affiliation(s)
- J Friedlein
- Department of Physics, University of Hamburg, Jungiusstrasse 11, 20355 Hamburg, Germany
| | - J Harm
- Department of Physics, University of Hamburg, Jungiusstrasse 11, 20355 Hamburg, Germany
| | - P Lindner
- Department of Physics, University of Hamburg, Jungiusstrasse 11, 20355 Hamburg, Germany
| | - L Bargsten
- Department of Physics, University of Hamburg, Jungiusstrasse 11, 20355 Hamburg, Germany
| | - M Bazarnik
- Department of Physics, University of Hamburg, Jungiusstrasse 11, 20355 Hamburg, Germany
| | - S Krause
- Department of Physics, University of Hamburg, Jungiusstrasse 11, 20355 Hamburg, Germany
| | - R Wiesendanger
- Department of Physics, University of Hamburg, Jungiusstrasse 11, 20355 Hamburg, Germany
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17
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The effect of material defects on resonant spin wave modes in a nanomagnet. Sci Rep 2019; 9:16635. [PMID: 31719613 PMCID: PMC6851160 DOI: 10.1038/s41598-019-53244-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2018] [Accepted: 10/22/2019] [Indexed: 11/12/2022] Open
Abstract
We have theoretically studied how resonant spin wave modes in an elliptical nanomagnet are affected by fabrication defects, such as small local thickness variations. Our results indicate that defects of this nature, which can easily result from the fabrication process, or are sometimes deliberately introduced during the fabrication process, will significantly alter the frequencies, magnetic field dependence of the frequencies, and the power and phase profiles of the resonant spin wave modes. They can also spawn new resonant modes and quench existing ones. All this has important ramifications for multi-device circuits based on spin waves, such as phase locked oscillators for neuromorphic computing, where the device-to-device variability caused by defects can be inhibitory.
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18
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Non-collinear spin states in bottom-up fabricated atomic chains. Nat Commun 2018; 9:2853. [PMID: 30030446 PMCID: PMC6054618 DOI: 10.1038/s41467-018-05364-5] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2018] [Accepted: 06/25/2018] [Indexed: 11/08/2022] Open
Abstract
Non-collinear spin states with unique rotational sense, such as chiral spin-spirals, are recently heavily investigated because of advantages for future applications in spintronics and information technology and as potential hosts for Majorana Fermions when coupled to a superconductor. Tuning the properties of such spin states, e.g., the rotational period and sense, is a highly desirable yet difficult task. Here, we experimentally demonstrate the bottom-up assembly of a spin-spiral derived from a chain of iron atoms on a platinum substrate using the magnetic tip of a scanning tunneling microscope as a tool. We show that the spin-spiral is induced by the interplay of the Heisenberg and Dzyaloshinskii-Moriya components of the Ruderman-Kittel-Kasuya-Yosida interaction between the iron atoms. The relative strengths and signs of these two components can be adjusted by the interatomic iron distance, which enables tailoring of the rotational period and sense of the spin-spiral.
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19
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Klein DR, MacNeill D, Lado JL, Soriano D, Navarro-Moratalla E, Watanabe K, Taniguchi T, Manni S, Canfield P, Fernández-Rossier J, Jarillo-Herrero P. Probing magnetism in 2D van der Waals crystalline insulators via electron tunneling. Science 2018; 360:1218-1222. [DOI: 10.1126/science.aar3617] [Citation(s) in RCA: 508] [Impact Index Per Article: 84.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2017] [Accepted: 04/24/2018] [Indexed: 12/14/2022]
Abstract
Magnetic insulators are a key resource for next-generation spintronic and topological devices. The family of layered metal halides promises varied magnetic states, including ultrathin insulating multiferroics, spin liquids, and ferromagnets, but device-oriented characterization methods are needed to unlock their potential. Here, we report tunneling through the layered magnetic insulator CrI3 as a function of temperature and applied magnetic field. We electrically detect the magnetic ground state and interlayer coupling and observe a field-induced metamagnetic transition. The metamagnetic transition results in magnetoresistances of 95, 300, and 550% for bilayer, trilayer, and tetralayer CrI3 barriers, respectively. We further measure inelastic tunneling spectra for our junctions, unveiling a rich spectrum consistent with collective magnetic excitations (magnons) in CrI3.
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20
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von Allwörden H, Eich A, Knol EJ, Hermenau J, Sonntag A, Gerritsen JW, Wegner D, Khajetoorians AA. Design and performance of an ultra-high vacuum spin-polarized scanning tunneling microscope operating at 30 mK and in a vector magnetic field. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2018; 89:033902. [PMID: 29604794 DOI: 10.1063/1.5020045] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We describe the design and performance of a scanning tunneling microscope (STM) that operates at a base temperature of 30 mK in a vector magnetic field. The cryogenics is based on an ultra-high vacuum (UHV) top-loading wet dilution refrigerator that contains a vector magnet allowing for fields up to 9 T perpendicular and 4 T parallel to the sample. The STM is placed in a multi-chamber UHV system, which allows in situ preparation and exchange of samples and tips. The entire system rests on a 150-ton concrete block suspended by pneumatic isolators, which is housed in an acoustically isolated and electromagnetically shielded laboratory optimized for extremely low noise scanning probe measurements. We demonstrate the overall performance by illustrating atomic resolution and quasiparticle interference imaging and detail the vibrational noise of both the laboratory and microscope. We also determine the electron temperature via measurement of the superconducting gap of Re(0001) and illustrate magnetic field-dependent measurements of the spin excitations of individual Fe atoms on Pt(111). Finally, we demonstrate spin resolution by imaging the magnetic structure of the Fe double layer on W(110).
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Affiliation(s)
- Henning von Allwörden
- Scanning Probe Microscopy Department, Institute for Molecules and Materials, Radboud University, Nijmegen, The Netherlands
| | - Andreas Eich
- Scanning Probe Microscopy Department, Institute for Molecules and Materials, Radboud University, Nijmegen, The Netherlands
| | - Elze J Knol
- Scanning Probe Microscopy Department, Institute for Molecules and Materials, Radboud University, Nijmegen, The Netherlands
| | - Jan Hermenau
- Department of Physics, Hamburg University, Hamburg, Germany
| | | | - Jan W Gerritsen
- Scanning Probe Microscopy Department, Institute for Molecules and Materials, Radboud University, Nijmegen, The Netherlands
| | - Daniel Wegner
- Scanning Probe Microscopy Department, Institute for Molecules and Materials, Radboud University, Nijmegen, The Netherlands
| | - Alexander A Khajetoorians
- Scanning Probe Microscopy Department, Institute for Molecules and Materials, Radboud University, Nijmegen, The Netherlands
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21
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Willke P, Paul W, Natterer FD, Yang K, Bae Y, Choi T, Fernández-Rossier J, Heinrich AJ, Lutz CP. Probing quantum coherence in single-atom electron spin resonance. SCIENCE ADVANCES 2018; 4:eaaq1543. [PMID: 29464211 PMCID: PMC5815865 DOI: 10.1126/sciadv.aaq1543] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2017] [Accepted: 01/16/2018] [Indexed: 05/24/2023]
Abstract
Spin resonance of individual spin centers allows applications ranging from quantum information technology to atomic-scale magnetometry. To protect the quantum properties of a spin, control over its local environment, including energy relaxation and decoherence processes, is crucial. However, in most existing architectures, the environment remains fixed by the crystal structure and electrical contacts. Recently, spin-polarized scanning tunneling microscopy (STM), in combination with electron spin resonance (ESR), allowed the study of single adatoms and inter-atomic coupling with an unprecedented combination of spatial and energy resolution. We elucidate and control the interplay of an Fe single spin with its atomic-scale environment by precisely tuning the phase coherence time T2 using the STM tip as a variable electrode. We find that the decoherence rate is the sum of two main contributions. The first scales linearly with tunnel current and shows that, on average, every tunneling electron causes one dephasing event. The second, effective even without current, arises from thermally activated spin-flip processes of tip spins. Understanding these interactions allows us to maximize T2 and improve the energy resolution. It also allows us to maximize the amplitude of the ESR signal, which supports measurements even at elevated temperatures as high as 4 K. Thus, ESR-STM allows control of quantum coherence in individual, electrically accessible spins.
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Affiliation(s)
- Philip Willke
- Center for Quantum Nanoscience, Institute for Basic Science, Seoul 03760, Republic of Korea
- IBM Almaden Research Center, San Jose, CA 95120, USA
- Department of Physics, Ewha Womans University, Seoul 03760, Republic of Korea
- IV. Physical Institute, University of Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - William Paul
- IBM Almaden Research Center, San Jose, CA 95120, USA
| | - Fabian D. Natterer
- IBM Almaden Research Center, San Jose, CA 95120, USA
- Institute of Physics, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
| | - Kai Yang
- IBM Almaden Research Center, San Jose, CA 95120, USA
| | - Yujeong Bae
- Center for Quantum Nanoscience, Institute for Basic Science, Seoul 03760, Republic of Korea
- IBM Almaden Research Center, San Jose, CA 95120, USA
- Department of Physics, Ewha Womans University, Seoul 03760, Republic of Korea
| | - Taeyoung Choi
- Center for Quantum Nanoscience, Institute for Basic Science, Seoul 03760, Republic of Korea
- Department of Physics, Ewha Womans University, Seoul 03760, Republic of Korea
| | - Joaquin Fernández-Rossier
- QuantaLab, International Iberian Nanotechnology Laboratory, Avenida Mestre José Veiga, 4715-310 Braga, Portugal
| | - Andreas J. Heinrich
- Center for Quantum Nanoscience, Institute for Basic Science, Seoul 03760, Republic of Korea
- Department of Physics, Ewha Womans University, Seoul 03760, Republic of Korea
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22
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Yang K, Bae Y, Paul W, Natterer FD, Willke P, Lado JL, Ferrón A, Choi T, Fernández-Rossier J, Heinrich AJ, Lutz CP. Engineering the Eigenstates of Coupled Spin-1/2 Atoms on a Surface. PHYSICAL REVIEW LETTERS 2017; 119:227206. [PMID: 29286811 DOI: 10.1103/physrevlett.119.227206] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/03/2017] [Indexed: 06/07/2023]
Abstract
Quantum spin networks having engineered geometries and interactions are eagerly pursued for quantum simulation and access to emergent quantum phenomena such as spin liquids. Spin-1/2 centers are particularly desirable, because they readily manifest coherent quantum fluctuations. Here we introduce a controllable spin-1/2 architecture consisting of titanium atoms on a magnesium oxide surface. We tailor the spin interactions by atomic-precision positioning using a scanning tunneling microscope (STM) and subsequently perform electron spin resonance on individual atoms to drive transitions into and out of quantum eigenstates of the coupled-spin system. Interactions between the atoms are mapped over a range of distances extending from highly anisotropic dipole coupling to strong exchange coupling. The local magnetic field of the magnetic STM tip serves to precisely tune the superposition states of a pair of spins. The precise control of the spin-spin interactions and ability to probe the states of the coupled-spin network by addressing individual spins will enable the exploration of quantum many-body systems based on networks of spin-1/2 atoms on surfaces.
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Affiliation(s)
- Kai Yang
- IBM Almaden Research Center, San Jose, California 95120, USA
| | - Yujeong Bae
- IBM Almaden Research Center, San Jose, California 95120, USA
- Center for Quantum Nanoscience, Institute for Basic Science (IBS), Seoul 03760, Republic of Korea
- Department of Physics, Ewha Womans University, Seoul 03760, Republic of Korea
| | - William Paul
- IBM Almaden Research Center, San Jose, California 95120, USA
| | - Fabian D Natterer
- IBM Almaden Research Center, San Jose, California 95120, USA
- Institute of Physics, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
| | - Philip Willke
- IBM Almaden Research Center, San Jose, California 95120, USA
- Center for Quantum Nanoscience, Institute for Basic Science (IBS), Seoul 03760, Republic of Korea
- Department of Physics, Ewha Womans University, Seoul 03760, Republic of Korea
| | - Jose L Lado
- QuantaLab, International Iberian Nanotechnology Laboratory (INL), Avenida Mestre José Veiga, 4715-310 Braga, Portugal
| | - Alejandro Ferrón
- Instituto de Modelado e Innovación Tecnológica (CONICET-UNNE), and Facultad de Ciencias Exactas, Naturales y Agrimensura, Universidad Nacional del Nordeste, Avenida Libertad 5400, W3404AAS Corrientes, Argentina
| | - Taeyoung Choi
- Center for Quantum Nanoscience, Institute for Basic Science (IBS), Seoul 03760, Republic of Korea
- Department of Physics, Ewha Womans University, Seoul 03760, Republic of Korea
| | - Joaquín Fernández-Rossier
- QuantaLab, International Iberian Nanotechnology Laboratory (INL), Avenida Mestre José Veiga, 4715-310 Braga, Portugal
- Departamento de Física Aplicada, Universidad de Alicante, San Vicente del Raspeig 03690, Spain
| | - Andreas J Heinrich
- Center for Quantum Nanoscience, Institute for Basic Science (IBS), Seoul 03760, Republic of Korea
- Department of Physics, Ewha Womans University, Seoul 03760, Republic of Korea
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23
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Rolf-Pissarczyk S, Yan S, Malavolti L, Burgess JAJ, McMurtrie G, Loth S. Dynamical Negative Differential Resistance in Antiferromagnetically Coupled Few-Atom Spin Chains. PHYSICAL REVIEW LETTERS 2017; 119:217201. [PMID: 29219401 DOI: 10.1103/physrevlett.119.217201] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2017] [Indexed: 06/07/2023]
Abstract
We present the appearance of negative differential resistance (NDR) in spin-dependent electron transport through a few-atom spin chain. A chain of three antiferromagnetically coupled Fe atoms (Fe trimer) was positioned on a Cu_{2}N/Cu(100) surface and contacted with the spin-polarized tip of a scanning tunneling microscope, thus coupling the Fe trimer to one nonmagnetic and one magnetic lead. Pronounced NDR appears at the low bias of 7 mV, where inelastic electron tunneling dynamically locks the atomic spin in a long-lived excited state. This causes a rapid increase of the magnetoresistance between the spin-polarized tip and Fe trimer and quenches elastic tunneling. By varying the coupling strength between the tip and Fe trimer, we find that in this transport regime the dynamic locking of the Fe trimer competes with magnetic exchange interaction, which statically forces the Fe trimer into its high-magnetoresistance state and removes the NDR.
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Affiliation(s)
- Steffen Rolf-Pissarczyk
- Max Planck Institute for the Structure and Dynamics of Matter, Luruper Chaussee 149, 22761 Hamburg, Germany
- Max Planck Institute for Solid State Research, Heisenbergstraße 1, 70569 Stuttgart, Germany
| | - Shichao Yan
- Max Planck Institute for the Structure and Dynamics of Matter, Luruper Chaussee 149, 22761 Hamburg, Germany
- Max Planck Institute for Solid State Research, Heisenbergstraße 1, 70569 Stuttgart, Germany
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Luigi Malavolti
- Max Planck Institute for the Structure and Dynamics of Matter, Luruper Chaussee 149, 22761 Hamburg, Germany
- Max Planck Institute for Solid State Research, Heisenbergstraße 1, 70569 Stuttgart, Germany
| | - Jacob A J Burgess
- Max Planck Institute for the Structure and Dynamics of Matter, Luruper Chaussee 149, 22761 Hamburg, Germany
- Max Planck Institute for Solid State Research, Heisenbergstraße 1, 70569 Stuttgart, Germany
- Department of Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada
| | - Gregory McMurtrie
- Max Planck Institute for the Structure and Dynamics of Matter, Luruper Chaussee 149, 22761 Hamburg, Germany
- Max Planck Institute for Solid State Research, Heisenbergstraße 1, 70569 Stuttgart, Germany
| | - Sebastian Loth
- Max Planck Institute for the Structure and Dynamics of Matter, Luruper Chaussee 149, 22761 Hamburg, Germany
- Max Planck Institute for Solid State Research, Heisenbergstraße 1, 70569 Stuttgart, Germany
- University of Stuttgart-Institute for Functional Matter and Quantum Technologies, Pfaffenwaldring 57, 70569 Stuttgart, Germany
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24
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Information processing in patterned magnetic nanostructures with edge spin waves. Sci Rep 2017; 7:5597. [PMID: 28717147 PMCID: PMC5514091 DOI: 10.1038/s41598-017-05737-8] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2017] [Accepted: 05/30/2017] [Indexed: 11/08/2022] Open
Abstract
Low dissipation data processing with spins is one of the promising directions for future information and communication technologies. Despite a significant progress, the available magnonic devices are not broadband yet and have restricted capabilities to redirect spin waves. Here we propose a breakthrough approach to spin wave manipulation in patterned magnetic nanostructures with unmatched characteristics, which exploits a spin wave analogue to edge waves propagating along a water-wall boundary. Using theory, micromagnetic simulations and experiment we investigate spin waves propagating along the edges in magnetic structures, under an in-plane DC magnetic field inclined with respect to the edge. The proposed edge spin waves overcome important challenges faced by previous technologies such as the manipulation of the spin wave propagation direction, and they substantially improve the capability of transmitting information at frequencies exceeding 10 GHz. The concept of the edge spin waves allows to design a broad of logic devices such as splitters, interferometers, or edge spin wave transistors with unprecedented characteristics and a potentially strong impact on information technologies.
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25
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Switching of spins and entanglement in surface-supported antiferromagnetic chains. Sci Rep 2017; 7:2759. [PMID: 28584280 PMCID: PMC5459826 DOI: 10.1038/s41598-017-02972-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2017] [Accepted: 04/20/2017] [Indexed: 11/08/2022] Open
Abstract
Previous experimental studies discovered universal growth of chains and nanowires of various chemical elements on a corrugated molecular network of Cu3N on the Cu(110). Herein, performing combined ab initio and quantum Hamiltonian studies we demonstrate that such chains can be used for a fast spin switching and entanglement generation by locally applied magnetic pulses. As an example, we show that in antiferromagnetic Co chains a strong entanglement between ends of chains occurs during spin switching. A novel parity effect in spin dynamics is reported. Even-numbered chains are found to exhibit significantly faster spin switching than odd-numbered counterparts. Moreover, at certain parameters of the system the dimerization effect in the spin dynamics of the chains was found. Our studies give a clear evidence that tailoring spin dynamics and entanglement can be achieved by magnetic fields and by tuning exchange interactions in supported chains.
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26
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Yan S, Malavolti L, Burgess JAJ, Droghetti A, Rubio A, Loth S. Nonlocally sensing the magnetic states of nanoscale antiferromagnets with an atomic spin sensor. SCIENCE ADVANCES 2017; 3:e1603137. [PMID: 28560346 PMCID: PMC5446215 DOI: 10.1126/sciadv.1603137] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2016] [Accepted: 03/27/2017] [Indexed: 05/11/2023]
Abstract
The ability to sense the magnetic state of individual magnetic nano-objects is a key capability for powerful applications ranging from readout of ultradense magnetic memory to the measurement of spins in complex structures with nanometer precision. Magnetic nano-objects require extremely sensitive sensors and detection methods. We create an atomic spin sensor consisting of three Fe atoms and show that it can detect nanoscale antiferromagnets through minute, surface-mediated magnetic interaction. Coupling, even to an object with no net spin and having vanishing dipolar stray field, modifies the transition matrix element between two spin states of the Fe atom-based spin sensor that changes the sensor's spin relaxation time. The sensor can detect nanoscale antiferromagnets at up to a 3-nm distance and achieves an energy resolution of 10 μeV, surpassing the thermal limit of conventional scanning probe spectroscopy. This scheme permits simultaneous sensing of multiple antiferromagnets with a single-spin sensor integrated onto the surface.
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Affiliation(s)
- Shichao Yan
- Max Planck Institute for the Structure and Dynamics of Matter, 22761 Hamburg, Germany
- Max Planck Institute for Solid State Research, 70569 Stuttgart, Germany
| | - Luigi Malavolti
- Max Planck Institute for the Structure and Dynamics of Matter, 22761 Hamburg, Germany
- Max Planck Institute for Solid State Research, 70569 Stuttgart, Germany
| | - Jacob A. J. Burgess
- Max Planck Institute for the Structure and Dynamics of Matter, 22761 Hamburg, Germany
- Max Planck Institute for Solid State Research, 70569 Stuttgart, Germany
| | - Andrea Droghetti
- Nano-Bio Spectroscopy Group, Department of Materials Science, Universidad del País Vasco, Avenida Tolosa 72, 20018 San Sebastian, Spain
| | - Angel Rubio
- Max Planck Institute for the Structure and Dynamics of Matter, 22761 Hamburg, Germany
- Nano-Bio Spectroscopy Group, Department of Materials Science, Universidad del País Vasco, Avenida Tolosa 72, 20018 San Sebastian, Spain
| | - Sebastian Loth
- Max Planck Institute for the Structure and Dynamics of Matter, 22761 Hamburg, Germany
- Max Planck Institute for Solid State Research, 70569 Stuttgart, Germany
- Institute for Functional Matter and Quantum Technologies, University of Stuttgart, 70569 Stuttgart, Germany
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27
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Banchi L, Fernández-Rossier J, Hirjibehedin CF, Bose S. Gating Classical Information Flow via Equilibrium Quantum Phase Transitions. PHYSICAL REVIEW LETTERS 2017; 118:147203. [PMID: 28430458 DOI: 10.1103/physrevlett.118.147203] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2016] [Indexed: 06/07/2023]
Abstract
The development of communication channels at the ultimate size limit of atomic scale physical dimensions will make the use of quantum entities an imperative. In this regime, quantum fluctuations naturally become prominent and are generally considered to be detrimental. Here, we show that for spin-based information processing, these fluctuations can be uniquely exploited to gate the flow of classical binary information across a magnetic chain in thermal equilibrium. Moreover, this information flow can be controlled with a modest external magnetic field that drives the system through different many-body quantum phases in which the orientation of the final spin does or does not reflect the orientation of the initial input. Our results are general for a wide class of anisotropic spin chains that act as magnetic cellular automata and suggest that quantum phase transitions play a unique role in driving classical information flow at the atomic scale.
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Affiliation(s)
- Leonardo Banchi
- Department of Physics and Astronomy, University College London (UCL), London WC1E 6BT, United Kingdom
| | - Joaquín Fernández-Rossier
- Quantalab, International Iberian Nanotechnology Laboratory, 4715-330 Braga, Portugal
- Departamento de Fsica Aplicada, Universidad de Alicante, 03690 San Vicente del Raspeig, Spain
| | - Cyrus F Hirjibehedin
- Department of Physics and Astronomy, University College London (UCL), London WC1E 6BT, United Kingdom
- London Centre for Nanotechnology, UCL, London WC1H 0AH, United Kingdom
- Department of Chemistry, UCL, London WC1H 0AJ, United Kingdom
| | - Sougato Bose
- Department of Physics and Astronomy, University College London (UCL), London WC1E 6BT, United Kingdom
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28
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Bergman A, Hellsvik J, Bessarab PF, Delin A. Spin relaxation signature of colossal magnetic anisotropy in platinum atomic chains. Sci Rep 2016; 6:36872. [PMID: 27841287 PMCID: PMC5107922 DOI: 10.1038/srep36872] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2016] [Accepted: 10/21/2016] [Indexed: 11/09/2022] Open
Abstract
Recent experimental data demonstrate emerging magnetic order in platinum atomically thin nanowires. Furthermore, an unusual form of magnetic anisotropy - colossal magnetic anisotropy (CMA) - was earlier predicted to exist in atomically thin platinum nanowires. Using spin dynamics simulations based on first-principles calculations, we here explore the spin dynamics of atomically thin platinum wires to reveal the spin relaxation signature of colossal magnetic anisotropy, comparing it with other types of anisotropy such as uniaxial magnetic anisotropy (UMA). We find that the CMA alters the spin relaxation process distinctly and, most importantly, causes a large speed-up of the magnetic relaxation compared to uniaxial magnetic anisotropy. The magnetic behavior of the nanowire exhibiting CMA should be possible to identify experimentally at the nanosecond time scale for temperatures below 5 K. This time-scale is accessible in e.g., soft x-ray free electron laser experiments.
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Affiliation(s)
- Anders Bergman
- Department of Physics and Astronomy, Materials Theory Division, Uppsala University, Box 516, SE-75120 Uppsala, Sweden
| | - Johan Hellsvik
- Department of Materials and Nano Physics, School of Information and Communication Technology, KTH Royal Institute of Technology, Electrum 229, SE-16440 Kista, Sweden
| | - Pavel F. Bessarab
- Department of Materials and Nano Physics, School of Information and Communication Technology, KTH Royal Institute of Technology, Electrum 229, SE-16440 Kista, Sweden
- Science Institute, University of Iceland, VR-III, 107 Reykjavík, Iceland
| | - Anna Delin
- Department of Physics and Astronomy, Materials Theory Division, Uppsala University, Box 516, SE-75120 Uppsala, Sweden
- Department of Materials and Nano Physics, School of Information and Communication Technology, KTH Royal Institute of Technology, Electrum 229, SE-16440 Kista, Sweden
- Swedish e-Science Research Center (SeRC), KTH Royal Institute of Technology, SE-10044 Stockholm, Sweden
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29
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Kalff FE, Rebergen MP, Fahrenfort E, Girovsky J, Toskovic R, Lado JL, Fernández-Rossier J, Otte AF. A kilobyte rewritable atomic memory. NATURE NANOTECHNOLOGY 2016; 11:926-929. [PMID: 27428273 DOI: 10.1038/nnano.2016.131] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2016] [Accepted: 06/15/2016] [Indexed: 05/08/2023]
Abstract
The advent of devices based on single dopants, such as the single-atom transistor, the single-spin magnetometer and the single-atom memory, has motivated the quest for strategies that permit the control of matter with atomic precision. Manipulation of individual atoms by low-temperature scanning tunnelling microscopy provides ways to store data in atoms, encoded either into their charge state, magnetization state or lattice position. A clear challenge now is the controlled integration of these individual functional atoms into extended, scalable atomic circuits. Here, we present a robust digital atomic-scale memory of up to 1 kilobyte (8,000 bits) using an array of individual surface vacancies in a chlorine-terminated Cu(100) surface. The memory can be read and rewritten automatically by means of atomic-scale markers and offers an areal density of 502 terabits per square inch, outperforming state-of-the-art hard disk drives by three orders of magnitude. Furthermore, the chlorine vacancies are found to be stable at temperatures up to 77 K, offering the potential for expanding large-scale atomic assembly towards ambient conditions.
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Affiliation(s)
- F E Kalff
- Department of Quantum Nanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands
| | - M P Rebergen
- Department of Quantum Nanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands
| | - E Fahrenfort
- Department of Quantum Nanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands
| | - J Girovsky
- Department of Quantum Nanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands
| | - R Toskovic
- Department of Quantum Nanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands
| | - J L Lado
- International Iberian Nanotechnology Laboratory (INL), Avenida Mestre José Veiga, 4715-310 Braga, Portugal
| | - J Fernández-Rossier
- International Iberian Nanotechnology Laboratory (INL), Avenida Mestre José Veiga, 4715-310 Braga, Portugal
- Departamento de Física Aplicada, Universidad de Alicante, San Vicente del Raspeig 03690, Spain
| | - A F Otte
- Department of Quantum Nanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands
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30
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Zhou GJ, Richter J, Schnack J, Zheng YZ. Hydrophobicity-Driven Self-Assembly of an Eighteen-Membered Honeycomb Lattice with Almost Classical Spins. Chemistry 2016; 22:14846-14850. [DOI: 10.1002/chem.201603559] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Indexed: 01/05/2023]
Affiliation(s)
- Guo-Jun Zhou
- Frontier Institute of Science and Technology (FIST); State Key Laboratory of Mechanical Behavior for Materials and MOE, Key Laboratory for Nonequilibrium Synthesis; Xi'an Jiaotong University.; Xi'an 710054 P. R. China
| | - Johannes Richter
- Institut für Theoretische Physik; Otto-von-Guericke-Universität Magdeburg, PF 4120; 39016 Magdeburg Germany
| | - Jürgen Schnack
- Faculty of Physics; Bielefeld University, PO box 100131; 33501 Bielefeld Germany
| | - Yan-Zhen Zheng
- Frontier Institute of Science and Technology (FIST); State Key Laboratory of Mechanical Behavior for Materials and MOE, Key Laboratory for Nonequilibrium Synthesis; Xi'an Jiaotong University.; Xi'an 710054 P. R. China
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31
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Singha A, Donati F, Wäckerlin C, Baltic R, Dreiser J, Pivetta M, Rusponi S, Brune H. Magnetic Hysteresis in Er Trimers on Cu(111). NANO LETTERS 2016; 16:3475-3481. [PMID: 27152738 DOI: 10.1021/acs.nanolett.5b05214] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We report magnetic hysteresis in Er clusters on Cu(111) starting from the size of three atoms. Combining X-ray magnetic circular dichroism, scanning tunneling microscopy, and mean-field nucleation theory, we determine the size-dependent magnetic properties of the Er clusters. Er atoms and dimers are paramagnetic, and their easy magnetization axes are oriented in-plane. In contrast, trimers and bigger clusters exhibit magnetic hysteresis at 2.5 K with a relaxation time of 2 min at 0.1 T and out-of-plane easy axis. This appearance of magnetic stability for trimers coincides with their enhanced structural stability.
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Affiliation(s)
- Aparajita Singha
- Institute of Physics, École Polytechnique Fédérale de Lausanne , Station 3, CH-1015 Lausanne, Switzerland
| | - Fabio Donati
- Institute of Physics, École Polytechnique Fédérale de Lausanne , Station 3, CH-1015 Lausanne, Switzerland
| | - Christian Wäckerlin
- Institute of Physics, École Polytechnique Fédérale de Lausanne , Station 3, CH-1015 Lausanne, Switzerland
| | - Romana Baltic
- Institute of Physics, École Polytechnique Fédérale de Lausanne , Station 3, CH-1015 Lausanne, Switzerland
| | - Jan Dreiser
- Institute of Physics, École Polytechnique Fédérale de Lausanne , Station 3, CH-1015 Lausanne, Switzerland
- Swiss Light Source, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
| | - Marina Pivetta
- Institute of Physics, École Polytechnique Fédérale de Lausanne , Station 3, CH-1015 Lausanne, Switzerland
| | - Stefano Rusponi
- Institute of Physics, École Polytechnique Fédérale de Lausanne , Station 3, CH-1015 Lausanne, Switzerland
| | - Harald Brune
- Institute of Physics, École Polytechnique Fédérale de Lausanne , Station 3, CH-1015 Lausanne, Switzerland
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32
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Saygun T, Bylin J, Hammar H, Fransson J. Voltage-Induced Switching Dynamics of a Coupled Spin Pair in a Molecular Junction. NANO LETTERS 2016; 16:2824-2829. [PMID: 27010805 DOI: 10.1021/acs.nanolett.6b00628] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Molecular spintronics is made possible by the coupling between electronic configuration and magnetic polarization of the molecules. For control and application of the individual molecular states, it is necessary to both read and write their spin states. Conventionally, this is achieved by means of external magnetic fields or ferromagnetic contacts, which may change the intentional spin state and may present additional challenges when downsizing devices. Here, we predict that coupling magnetic molecules together opens up possibilities for all electrical control of both the molecular spin states as well as the current flow through the system. By tuning between the regimes of ferromagnetic and antiferromagnetic exchange interaction, the current can be at least an order of magnitude enhanced or reduced. The effect is susceptible to the tunnel coupling and molecular level alignment that can be used to achieve current rectification.
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Affiliation(s)
- T Saygun
- Department of Physics and Astronomy, Uppsala University , Box 516, 75120 Uppsala, Sweden
| | - J Bylin
- Department of Physics and Astronomy, Uppsala University , Box 516, 75120 Uppsala, Sweden
| | - H Hammar
- Department of Physics and Astronomy, Uppsala University , Box 516, 75120 Uppsala, Sweden
| | - J Fransson
- Department of Physics and Astronomy, Uppsala University , Box 516, 75120 Uppsala, Sweden
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33
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Yu H, d' Allivy Kelly O, Cros V, Bernard R, Bortolotti P, Anane A, Brandl F, Heimbach F, Grundler D. Approaching soft X-ray wavelengths in nanomagnet-based microwave technology. Nat Commun 2016; 7:11255. [PMID: 27063401 PMCID: PMC4831022 DOI: 10.1038/ncomms11255] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2015] [Accepted: 03/07/2016] [Indexed: 12/25/2022] Open
Abstract
Seven decades after the discovery of collective spin excitations in microwave-irradiated ferromagnets, there has been a rebirth of magnonics. However, magnetic nanodevices will enable smart GHz-to-THz devices at low power consumption only, if such spin waves (magnons) are generated and manipulated on the sub-100 nm scale. Here we show how magnons with a wavelength of a few 10 nm are exploited by combining the functionality of insulating yttrium iron garnet and nanodisks from different ferromagnets. We demonstrate magnonic devices at wavelengths of 88 nm written/read by conventional coplanar waveguides. Our microwave-to-magnon transducers are reconfigurable and thereby provide additional functionalities. The results pave the way for a multi-functional GHz technology with unprecedented miniaturization exploiting nanoscale wavelengths that are otherwise relevant for soft X-rays. Nanomagnonics integrated with broadband microwave circuitry offer applications that are wide ranging, from nanoscale microwave components to nonlinear data processing, image reconstruction and wave-based logic.
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Affiliation(s)
- Haiming Yu
- Physik Department E10, Technische Universität München, James-Franck-Strasse 1, D-85748 Garching bei München, Germany.,Fert Beijing Institute, School of Electronic and Information Engineering, Beihang University, Xueyuan Road 37, Beijing 100191, China
| | - O d' Allivy Kelly
- Unité Mixte de Physique, CNRS, Thales, Univ Paris-Sud, Université Paris-Saclay, 91767 Palaiseau, France
| | - V Cros
- Unité Mixte de Physique, CNRS, Thales, Univ Paris-Sud, Université Paris-Saclay, 91767 Palaiseau, France
| | - R Bernard
- Unité Mixte de Physique, CNRS, Thales, Univ Paris-Sud, Université Paris-Saclay, 91767 Palaiseau, France
| | - P Bortolotti
- Unité Mixte de Physique, CNRS, Thales, Univ Paris-Sud, Université Paris-Saclay, 91767 Palaiseau, France
| | - A Anane
- Unité Mixte de Physique, CNRS, Thales, Univ Paris-Sud, Université Paris-Saclay, 91767 Palaiseau, France
| | - F Brandl
- Physik Department E10, Technische Universität München, James-Franck-Strasse 1, D-85748 Garching bei München, Germany
| | - F Heimbach
- Physik Department E10, Technische Universität München, James-Franck-Strasse 1, D-85748 Garching bei München, Germany
| | - D Grundler
- Physik Department E10, Technische Universität München, James-Franck-Strasse 1, D-85748 Garching bei München, Germany.,Laboratory of Nanoscale Magnetic Materials and Magnonics, Institute of Materials, School of Engineering, École Polytechnique Fédérale de Lausanne, STI-IMX-LMGN, Station 17, CH-1015 Lausanne, Switzerland
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34
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Absence of a spin-signature from a single Ho adatom as probed by spin-sensitive tunneling. Nat Commun 2016; 7:10454. [PMID: 26838811 PMCID: PMC4742789 DOI: 10.1038/ncomms10454] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2015] [Accepted: 12/10/2015] [Indexed: 11/08/2022] Open
Abstract
Whether rare-earth materials can be used as single-atom magnetic memory is an ongoing debate in recent literature. Here we show, by inelastic and spin-resolved scanning tunnelling-based methods, that we observe a strong magnetic signal and excitation from Fe atoms adsorbed on Pt(111), but see no signatures of magnetic excitation or spin-based telegraph noise for Ho atoms. Moreover, we observe that the indirect exchange field produced by a single Ho atom is negligible, as sensed by nearby Fe atoms. We demonstrate, using ab initio methods, that this stems from a comparatively weak coupling of the Ho 4f electrons with both tunnelling electrons and substrate-derived itinerant electrons, making both magnetic coupling and detection very difficult when compared to 3d elements. We discuss these results in the context of ongoing disputes and clarify important controversies. Magnetic stability of holmium atoms on a platinum(111) surface has recently been reported, raising prospects for atomic-scale spintronics, however contradictory results have since emerged. Here, Steinbrecher et al. find evidence for an invisibility of the holmium spin to scanning tunnelling spectroscopy techniques which challenges recent results.
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35
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Exploring the phase diagram of the two-impurity Kondo problem. Nat Commun 2015; 6:10046. [PMID: 26616044 PMCID: PMC4674668 DOI: 10.1038/ncomms10046] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2015] [Accepted: 10/29/2015] [Indexed: 12/04/2022] Open
Abstract
A system of two exchange-coupled Kondo impurities in a magnetic field gives rise to a rich phase space hosting a multitude of correlated phenomena. Magnetic atoms on surfaces probed through scanning tunnelling microscopy provide an excellent platform to investigate coupled impurities, but typical high Kondo temperatures prevent field-dependent studies from being performed, rendering large parts of the phase space inaccessible. We present a study of pairs of Co atoms on insulating Cu2N/Cu(100), which each have a Kondo temperature of only 2.6 K. The pairs are designed to have interaction strengths similar to the Kondo temperature. By applying a sufficiently strong magnetic field, we are able to access a new phase in which the two coupled impurities are simultaneously screened. Comparison of differential conductance spectra taken on the atoms to simulated curves, calculated using a third-order transport model, allows us to independently determine the degree of Kondo screening in each phase. Magnetic atoms on a surface possess diverse correlated phases under an applied magnetic field due to a balance of exchange interaction and carrier-mediated coupling. Here, the authors use scanning tunnel microscopy to explore the phase diagram of coupled Co atom pairs on the surface of Cu2N/Cu(100).
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36
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Bryant B, Toskovic R, Ferrón A, Lado JL, Spinelli A, Fernández-Rossier J, Otte AF. Controlled Complete Suppression of Single-Atom Inelastic Spin and Orbital Cotunneling. NANO LETTERS 2015; 15:6542-6546. [PMID: 26366713 DOI: 10.1021/acs.nanolett.5b02200] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The inelastic portion of the tunnel current through an individual magnetic atom grants unique access to read out and change the atom's spin state, but it also provides a path for spontaneous relaxation and decoherence. Controlled closure of the inelastic channel would allow for the latter to be switched off at will, paving the way to coherent spin manipulation in single atoms. Here, we demonstrate complete closure of the inelastic channels for both spin and orbital transitions due to a controlled geometric modification of the atom's environment, using scanning tunneling microscopy (STM). The observed suppression of the excitation signal, which occurs for Co atoms assembled into chains on a Cu2N substrate, indicates a structural transition affecting the dz(2) orbital, effectively cutting off the STM tip from the spin-flip cotunneling path.
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Affiliation(s)
- Benjamin Bryant
- Department of Quantum Nanoscience, Kavli Institute of Nanoscience, Delft University of Technology , Lorentzweg 1, 2628 CJ Delft, The Netherlands
| | - Ranko Toskovic
- Department of Quantum Nanoscience, Kavli Institute of Nanoscience, Delft University of Technology , Lorentzweg 1, 2628 CJ Delft, The Netherlands
| | - Alejandro Ferrón
- International Iberian Nanotechnology Laboratory (INL) , Avenida Mestre José Veiga, 4715-330 Braga, Portugal
- Instituto de Modelado e Innovación Tecnológica (CONICET-UNNE) , Avenida Libertad 5400, W3404AAS Corrientes, Argentina
| | - José L Lado
- International Iberian Nanotechnology Laboratory (INL) , Avenida Mestre José Veiga, 4715-330 Braga, Portugal
| | - Anna Spinelli
- Department of Quantum Nanoscience, Kavli Institute of Nanoscience, Delft University of Technology , Lorentzweg 1, 2628 CJ Delft, The Netherlands
| | - Joaquín Fernández-Rossier
- International Iberian Nanotechnology Laboratory (INL) , Avenida Mestre José Veiga, 4715-330 Braga, Portugal
- Departamento de Fı́sica Aplicada, Universidad de Alicante , San Vicente del Raspeig, 03690, Spain
| | - Alexander F Otte
- Department of Quantum Nanoscience, Kavli Institute of Nanoscience, Delft University of Technology , Lorentzweg 1, 2628 CJ Delft, The Netherlands
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37
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Nanometre-scale probing of spin waves using single-electron spins. Nat Commun 2015; 6:7886. [PMID: 26249673 PMCID: PMC4918315 DOI: 10.1038/ncomms8886] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2014] [Accepted: 06/23/2015] [Indexed: 11/15/2022] Open
Abstract
Pushing the frontiers of condensed-matter magnetism requires the development of tools that provide real-space, few-nanometre-scale probing of correlated-electron magnetic excitations under ambient conditions. Here we present a practical approach to meet this challenge, using magnetometry based on single nitrogen-vacancy centres in diamond. We focus on spin-wave excitations in a ferromagnetic microdisc, and demonstrate local, quantitative and phase-sensitive detection of the spin-wave magnetic field at ∼50 nm from the disc. We map the magnetic-field dependence of spin-wave excitations by detecting the associated local reduction in the disc's longitudinal magnetization. In addition, we characterize the spin–noise spectrum by nitrogen-vacancy spin relaxometry, finding excellent agreement with a general analytical description of the stray fields produced by spin–spin correlations in a 2D magnetic system. These complementary measurement modalities pave the way towards imaging the local excitations of systems such as ferromagnets and antiferromagnets, skyrmions, atomically assembled quantum magnets, and spin ice. Exploring magnetic excitations and spin textures on the nanoscale may lead to new spintronic technologies and new understanding of condensed matter. Here, the authors demonstrate the potential of single-electron spins in diamond to image such excitations by characterizing spin waves in a ferromagnetic microdisc.
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38
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Spinelli A, Rebergen MP, Otte AAF. Atomically crafted spin lattices as model systems for quantum magnetism. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:243203. [PMID: 26034814 DOI: 10.1088/0953-8984/27/24/243203] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Low-dimensional quantum magnetism presents a seemingly unlimited source of rich, intriguing physics. Yet, because realistic experimental representations are difficult to come by, the field remains predominantly theoretical. In recent years, artificial spin structures built through manipulation of magnetic atoms in a scanning tunnelling microscope have developed into a promising testing ground for experimental verification of theoretical models. Here, we present an overview of available tools and discuss recent achievements as well as future avenues. Moreover, we show new observations on magnetic switching in a bistable bit that can be used to extrapolate information on the magnetisation of the microscope tip.
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Affiliation(s)
- A Spinelli
- Department of Quantum Nanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, the Netherlands
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39
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Direct observation of finite size effects in chains of antiferromagnetically coupled spins. Nat Commun 2015; 6:7061. [PMID: 25952539 PMCID: PMC4432630 DOI: 10.1038/ncomms8061] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2014] [Accepted: 03/26/2015] [Indexed: 11/14/2022] Open
Abstract
Finite spin chains made of few magnetic ions are the ultimate-size structures that can be engineered to perform spin manipulations for quantum information devices. Their spin structure is expected to show finite size effects and its knowledge is of great importance both for fundamental physics and applications. Until now a direct and quantitative measurement of the spatial distribution of the magnetization of such small structures has not been achieved even with the most advanced microscopic techniques. Here we present measurements of the spin density distribution of a finite chain of eight spin-3/2 ions using polarized neutron diffraction. The data reveal edge effects that are a consequence of the finite size and of the parity of the chain and indicate a noncollinear spin arrangement. This is in contrast with the uniform spin distribution observed in the parent closed chain and the collinear arrangement in odd-open chains. Molecular magnets are among the smallest structures that may be exploited for quantum information processing. Here, Guidi et al. use polarized neutron scattering to observe finite size effects and a noncollinear spin arrangement in a Cr8Cd ring molecule, an even-numbered open antiferromagnetic spin-3/2 chain.
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40
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Rohart S, Rodary G. Spin waves: close-up on spin dynamics. NATURE MATERIALS 2014; 13:770-771. [PMID: 24997738 DOI: 10.1038/nmat4038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Affiliation(s)
- Stanislas Rohart
- Laboratoire de Physique des Solides, Université Paris-Sud and CNRS, Bâtiment 510, 91405 Orsay cedex, France
| | - Guillemin Rodary
- Laboratoire de Photonique et de Nanostructures, CNRS, Route de Nozay, 91460 Marcoussis, France
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