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Gutfreund A, Matsuki H, Plastovets V, Noah A, Gorzawski L, Fridman N, Yang G, Buzdin A, Millo O, Robinson JWA, Anahory Y. Direct observation of a superconducting vortex diode. Nat Commun 2023; 14:1630. [PMID: 36959184 PMCID: PMC10036628 DOI: 10.1038/s41467-023-37294-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2022] [Accepted: 03/09/2023] [Indexed: 03/25/2023] Open
Abstract
The interplay between magnetism and superconductivity can lead to unconventional proximity and Josephson effects. A related phenomenon that has recently attracted considerable attention is the superconducting diode effect, in which a nonreciprocal critical current emerges. Although superconducting diodes based on superconductor/ferromagnet (S/F) bilayers were demonstrated more than a decade ago, the precise underlying mechanism remains unclear. While not formally linked to this effect, the Fulde-Ferrell-Larkin-Ovchinikov (FFLO) state is a plausible mechanism due to the twofold rotational symmetry breaking caused by the finite center-of-mass-momentum of the Cooper pairs. Here, we directly observe asymmetric vortex dynamics that uncover the mechanism behind the superconducting vortex diode effect in Nb/EuS (S/F) bilayers. Based on our nanoscale SQUID-on-tip (SOT) microscope and supported by in-situ transport measurements, we propose a theoretical model that captures our key results. The key conclusion of our model is that screening currents induced by the stray fields from the F layer are responsible for the measured nonreciprocal critical current. Thus, we determine the origin of the vortex diode effect, which builds a foundation for new device concepts.
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Affiliation(s)
- Alon Gutfreund
- The Racah Institute of Physics, The Hebrew University of Jerusalem, Jerusalem, 9190401, Israel.
| | - Hisakazu Matsuki
- Department of Materials Science & Metallurgy, University of Cambridge, Cambridge, CB3 0FS, United Kingdom
| | - Vadim Plastovets
- LOMA UMR-CNRS 5798, University of Bordeaux, Talence, F-33405, France
| | - Avia Noah
- The Racah Institute of Physics, The Hebrew University of Jerusalem, Jerusalem, 9190401, Israel
| | - Laura Gorzawski
- Department of Materials Science & Metallurgy, University of Cambridge, Cambridge, CB3 0FS, United Kingdom
| | - Nofar Fridman
- The Racah Institute of Physics, The Hebrew University of Jerusalem, Jerusalem, 9190401, Israel
| | - Guang Yang
- Department of Materials Science & Metallurgy, University of Cambridge, Cambridge, CB3 0FS, United Kingdom
| | - Alexander Buzdin
- LOMA UMR-CNRS 5798, University of Bordeaux, Talence, F-33405, France
| | - Oded Millo
- The Racah Institute of Physics, The Hebrew University of Jerusalem, Jerusalem, 9190401, Israel
| | - Jason W A Robinson
- Department of Materials Science & Metallurgy, University of Cambridge, Cambridge, CB3 0FS, United Kingdom.
| | - Yonathan Anahory
- The Racah Institute of Physics, The Hebrew University of Jerusalem, Jerusalem, 9190401, Israel.
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2
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Bhattacharyya S, Akhgar G, Gebert M, Karel J, Edmonds MT, Fuhrer MS. Recent Progress in Proximity Coupling of Magnetism to Topological Insulators. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2021; 33:e2007795. [PMID: 34185344 DOI: 10.1002/adma.202007795] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2020] [Revised: 01/11/2021] [Indexed: 05/08/2023]
Abstract
Inducing long-range magnetic order in 3D topological insulators can gap the Dirac-like metallic surface states, leading to exotic new phases such as the quantum anomalous Hall effect or the axion insulator state. These magnetic topological phases can host robust, dissipationless charge and spin currents or unique magnetoelectric behavior, which can be exploited in low-energy electronics and spintronics applications. Although several different strategies have been successfully implemented to realize these states, to date these phenomena have been confined to temperatures below a few Kelvin. This review focuses on one strategy: inducing magnetic order in topological insulators by proximity of magnetic materials, which has the capability for room temperature operation, unlocking the potential of magnetic topological phases for applications. The unique advantages of this strategy, the important physical mechanisms facilitating magnetic proximity effect, and the recent progress to achieve, understand, and harness proximity-coupled magnetic order in topological insulators are discussed. Some emerging new phenomena and applications enabled by proximity coupling of magnetism and topological materials, such as skyrmions and the topological Hall effect, are also highlighted, and the authors conclude with an outlook on remaining challenges and opportunities in the field.
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Affiliation(s)
- Semonti Bhattacharyya
- School of Physics and Astronomy, Monash University, Victoria, 3800, Australia
- ARC Centre of Excellence in Future Low-Energy Electronics Technologies, Monash University, Victoria, 3800, Australia
| | - Golrokh Akhgar
- School of Physics and Astronomy, Monash University, Victoria, 3800, Australia
- ARC Centre of Excellence in Future Low-Energy Electronics Technologies, Monash University, Victoria, 3800, Australia
| | - Matthew Gebert
- School of Physics and Astronomy, Monash University, Victoria, 3800, Australia
- ARC Centre of Excellence in Future Low-Energy Electronics Technologies, Monash University, Victoria, 3800, Australia
| | - Julie Karel
- ARC Centre of Excellence in Future Low-Energy Electronics Technologies, Monash University, Victoria, 3800, Australia
- Department of Materials Science and Engineering, Monash University, Clayton, Victoria, 3800, Australia
| | - Mark T Edmonds
- School of Physics and Astronomy, Monash University, Victoria, 3800, Australia
- ARC Centre of Excellence in Future Low-Energy Electronics Technologies, Monash University, Victoria, 3800, Australia
| | - Michael S Fuhrer
- School of Physics and Astronomy, Monash University, Victoria, 3800, Australia
- ARC Centre of Excellence in Future Low-Energy Electronics Technologies, Monash University, Victoria, 3800, Australia
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3
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Liu Y, Luchini A, Martí-Sánchez S, Koch C, Schuwalow S, Khan SA, Stankevič T, Francoual S, Mardegan JRL, Krieger JA, Strocov VN, Stahn J, Vaz CAF, Ramakrishnan M, Staub U, Lefmann K, Aeppli G, Arbiol J, Krogstrup P. Coherent Epitaxial Semiconductor-Ferromagnetic Insulator InAs/EuS Interfaces: Band Alignment and Magnetic Structure. ACS APPLIED MATERIALS & INTERFACES 2020; 12:8780-8787. [PMID: 31877013 DOI: 10.1021/acsami.9b15034] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Hybrid semiconductor-ferromagnetic insulator heterostructures are interesting due to their tunable electronic transport, self-sustained stray field, and local proximitized magnetic exchange. In this work, we present lattice-matched hybrid epitaxy of semiconductor-ferromagnetic insulator InAs/EuS heterostructures and analyze the atomic-scale structure and their electronic and magnetic characteristics. The Fermi level at the InAs/EuS interface is found to be close to the InAs conduction band and in the band gap of EuS, thus preserving the semiconducting properties. Both neutron and X-ray reflectivity measurements show that the overall ferromagnetic component is mainly localized in the EuS thin film with a suppression of the Eu moment in the EuS layer nearest the InAs and magnetic moments outside the detection limits on the pure InAs side. This work presents a step toward realizing defect-free semiconductor-ferromagnetic insulator epitaxial hybrids for spin-lifted quantum and spintronic applications without external magnetic fields.
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Affiliation(s)
- Yu Liu
- Microsoft Quantum Materials Lab Copenhagen , 2800 Lyngby , Denmark
| | | | - Sara Martí-Sánchez
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST , Campus UAB, Bellaterra , 08193 Barcelona , Catalonia , Spain
| | - Christian Koch
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST , Campus UAB, Bellaterra , 08193 Barcelona , Catalonia , Spain
| | - Sergej Schuwalow
- Microsoft Quantum Materials Lab Copenhagen , 2800 Lyngby , Denmark
| | - Sabbir A Khan
- Microsoft Quantum Materials Lab Copenhagen , 2800 Lyngby , Denmark
| | - Tomaš Stankevič
- Microsoft Quantum Materials Lab Copenhagen , 2800 Lyngby , Denmark
| | - Sonia Francoual
- Deutsches Elektronen-Synchrotron DESY , Hamburg 22603 , Germany
| | | | | | | | - Jochen Stahn
- Paul Scherrer Institute , CH-5232 Villigen , Switzerland
| | - Carlos A F Vaz
- Paul Scherrer Institute , CH-5232 Villigen , Switzerland
| | | | - Urs Staub
- Paul Scherrer Institute , CH-5232 Villigen , Switzerland
| | | | - Gabriel Aeppli
- Paul Scherrer Institute , CH-5232 Villigen , Switzerland
- ETH , CH-8093 Zürich , Switzerland
- EPFL , CH-1015 Lausanne , Switzerland
| | - Jordi Arbiol
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST , Campus UAB, Bellaterra , 08193 Barcelona , Catalonia , Spain
- ICREA , Pg. Lluís Companys 23 , 08010 Barcelona , Catalonia , Spain
| | - Peter Krogstrup
- Microsoft Quantum Materials Lab Copenhagen , 2800 Lyngby , Denmark
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4
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Liu Y, Vaitiekėnas S, Martí-Sánchez S, Koch C, Hart S, Cui Z, Kanne T, Khan SA, Tanta R, Upadhyay S, Cachaza ME, Marcus CM, Arbiol J, Moler KA, Krogstrup P. Semiconductor-Ferromagnetic Insulator-Superconductor Nanowires: Stray Field and Exchange Field. NANO LETTERS 2020; 20:456-462. [PMID: 31769993 DOI: 10.1021/acs.nanolett.9b04187] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Nanowires can serve as flexible substrates for hybrid epitaxial growth on selected facets, allowing for the design of heterostructures with complex material combinations and geometries. In this work we report on hybrid epitaxy of freestanding vapor-liquid-solid grown and in-plane selective area grown semiconductor-ferromagnetic insulator-superconductor (InAs/EuS/Al) nanowire heterostructures. We study the crystal growth and complex epitaxial matching of wurtzite and zinc-blende InAs/rock-salt EuS interfaces as well as rock-salt EuS/face-centered cubic Al interfaces. Because of the magnetic anisotropy originating from the nanowire shape, the magnetic structure of the EuS phase is easily tuned into single magnetic domains. This effect efficiently ejects the stray field lines along the nanowires. With tunnel spectroscopy measurements of the density of states, we show that the material has a hard induced superconducting gap, and magnetic hysteretic evolution which indicates that the magnetic exchange fields are not negligible. These hybrid nanowires fulfill key material requirements for serving as a platform for spin-based quantum applications, such as scalable topological quantum computing.
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Affiliation(s)
- Yu Liu
- Microsoft Quantum Materials Lab Copenhagen , 2800 Lyngby , Denmark
- Center for Quantum Devices, Niels Bohr Institute , University of Copenhagen , 2100 Copenhagen , Denmark
| | - Saulius Vaitiekėnas
- Center for Quantum Devices, Niels Bohr Institute , University of Copenhagen , 2100 Copenhagen , Denmark
- Microsoft Quantum Lab Copenhagen, Niels Bohr Institute , University of Copenhagen , 2100 Copenhagen , Denmark
| | - Sara Martí-Sánchez
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST , Campus UAB, Bellaterra, Barcelona , 08193 Catalonia , Spain
| | - Christian Koch
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST , Campus UAB, Bellaterra, Barcelona , 08193 Catalonia , Spain
| | - Sean Hart
- Stanford Institute for Materials and Energy Sciences , SLAC National Accelerator Laboratory , Menlo Park , California 94025 , United States
- Department of Physics , Stanford University , Stanford , California 94305 , United States
| | - Zheng Cui
- Stanford Institute for Materials and Energy Sciences , SLAC National Accelerator Laboratory , Menlo Park , California 94025 , United States
- Department of Applied Physics , Stanford University , Stanford , California 94305 , United States
| | - Thomas Kanne
- Center for Quantum Devices, Niels Bohr Institute , University of Copenhagen , 2100 Copenhagen , Denmark
| | - Sabbir A Khan
- Microsoft Quantum Materials Lab Copenhagen , 2800 Lyngby , Denmark
- Center for Quantum Devices, Niels Bohr Institute , University of Copenhagen , 2100 Copenhagen , Denmark
| | - Rawa Tanta
- Microsoft Quantum Materials Lab Copenhagen , 2800 Lyngby , Denmark
- Center for Quantum Devices, Niels Bohr Institute , University of Copenhagen , 2100 Copenhagen , Denmark
| | - Shivendra Upadhyay
- Center for Quantum Devices, Niels Bohr Institute , University of Copenhagen , 2100 Copenhagen , Denmark
- Microsoft Quantum Lab Copenhagen, Niels Bohr Institute , University of Copenhagen , 2100 Copenhagen , Denmark
| | - Martin Espiñeira Cachaza
- Microsoft Quantum Materials Lab Copenhagen , 2800 Lyngby , Denmark
- Center for Quantum Devices, Niels Bohr Institute , University of Copenhagen , 2100 Copenhagen , Denmark
| | - Charles M Marcus
- Center for Quantum Devices, Niels Bohr Institute , University of Copenhagen , 2100 Copenhagen , Denmark
- Microsoft Quantum Lab Copenhagen, Niels Bohr Institute , University of Copenhagen , 2100 Copenhagen , Denmark
| | - Jordi Arbiol
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST , Campus UAB, Bellaterra, Barcelona , 08193 Catalonia , Spain
- ICREA , Pg. Lluís Companys 23 , Barcelona , 08010 Catalonia , Spain
| | - Kathryn A Moler
- Stanford Institute for Materials and Energy Sciences , SLAC National Accelerator Laboratory , Menlo Park , California 94025 , United States
- Department of Physics , Stanford University , Stanford , California 94305 , United States
- Department of Applied Physics , Stanford University , Stanford , California 94305 , United States
| | - Peter Krogstrup
- Microsoft Quantum Materials Lab Copenhagen , 2800 Lyngby , Denmark
- Center for Quantum Devices, Niels Bohr Institute , University of Copenhagen , 2100 Copenhagen , Denmark
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5
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Wei P, Manna S, Eich M, Lee P, Moodera J. Superconductivity in the Surface State of Noble Metal Gold and its Fermi Level Tuning by EuS Dielectric. PHYSICAL REVIEW LETTERS 2019; 122:247002. [PMID: 31322391 DOI: 10.1103/physrevlett.122.247002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2019] [Revised: 03/27/2019] [Indexed: 06/10/2023]
Abstract
The induced superconductivity (SC) in a robust and scalable quantum material with strong Rashba spin-orbit coupling is particularly attractive for generating topological superconductivity and Majorana bound states (MBS). Gold (111) thin film has been proposed as a promising candidate because of the large Rashba energy, the predicted topological nature, and the possibility for large-scale MBS device fabrications. We experimentally demonstrate two important steps towards achieving such a goal. We successfully show induced SC in the Shockley surface state (SS) of ultrathin Au(111) layers grown over epitaxial vanadium films, which is easily achievable on a wafer scale. The emergence of SC in the SS, which is physically separated from a bulk superconductor, is attained by indirect quasiparticle scattering processes instead of by conventional interfacial Andreev reflections. We further show the ability to tune the SS Fermi level (E_{F}) by interfacing SS with a high-κ dielectric ferromagnetic insulator EuS. The shift of E_{F} from ∼550 to ∼34 mV in superconducting SS is an important step towards realizing MBS in this robust system.
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Affiliation(s)
- Peng Wei
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
- Department of Physics and Astronomy, University of California, Riverside, California 92521, USA
| | - Sujit Manna
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Marius Eich
- Plasma Science and Fusion Center & Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
- Solid State Physics Laboratory, ETH Zurich, 8093 Zurich, Switzerland
| | - Patrick Lee
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Jagadeesh Moodera
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
- Plasma Science and Fusion Center & Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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6
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Cai X, Song T, Wilson NP, Clark G, He M, Zhang X, Taniguchi T, Watanabe K, Yao W, Xiao D, McGuire MA, Cobden DH, Xu X. Atomically Thin CrCl 3: An In-Plane Layered Antiferromagnetic Insulator. NANO LETTERS 2019; 19:3993-3998. [PMID: 31083954 DOI: 10.1021/acs.nanolett.9b01317] [Citation(s) in RCA: 92] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
The recent discovery of magnetism in atomically thin layers of van der Waals (vdW) crystals has created new opportunities for exploring magnetic phenomena in the two-dimensional (2D) limit. In most 2D magnets studied to date, the c-axis is an easy axis, so that at zero applied field the polarization of each layer is perpendicular to the plane. Here, we demonstrate that atomically thin CrCl3 is a layered antiferromagnetic insulator with an easy-plane normal to the c-axis, that is, the polarization is in the plane of each layer and has no preferred direction within it. Ligand-field photoluminescence at 870 nm is observed down to the monolayer limit, demonstrating its insulating properties. We investigate the in-plane magnetic order using tunneling magnetoresistance in graphene/CrCl3/graphene tunnel junctions, establishing that the interlayer coupling is antiferromagnetic down to the bilayer. From the temperature dependence of the magnetoresistance, we obtain an effective magnetic phase diagram for the bilayer. Our result shows that CrCl3 should be useful for studying the physics of 2D phase transitions and for making new kinds of vdW spintronic devices.
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Affiliation(s)
- Xinghan Cai
- Department of Physics , University of Washington , Seattle , Washington 98195 , United States
- National Key Laboratory of Science and Technology on Micro/Nano Fabrication, Department of Micro/Nano Electronics , Shanghai Jiao Tong University , Shanghai 200240 , China
| | - Tiancheng Song
- Department of Physics , University of Washington , Seattle , Washington 98195 , United States
| | - Nathan P Wilson
- Department of Physics , University of Washington , Seattle , Washington 98195 , United States
| | - Genevieve Clark
- Department of Materials Science and Engineering , University of Washington , Seattle , Washington 98195 , United States
| | - Minhao He
- Department of Physics , University of Washington , Seattle , Washington 98195 , United States
| | - Xiaoou Zhang
- Department of Physics , Carnegie Mellon University , Pittsburgh , Pennsylvania 15213 , United States
| | - Takashi Taniguchi
- National Institute for Materials Science , Tsukuba , Ibaraki 305-0044 , Japan
| | - Kenji Watanabe
- National Institute for Materials Science , Tsukuba , Ibaraki 305-0044 , Japan
| | - Wang Yao
- Department of Physics and Center of Theoretical and Computational Physics , University of Hong Kong , Hong Kong , China
| | - Di Xiao
- Department of Physics , Carnegie Mellon University , Pittsburgh , Pennsylvania 15213 , United States
| | - Michael A McGuire
- Materials Science and Technology Division , Oak Ridge National Laboratory , Oak Ridge , Tennessee 37831 , United States
| | - David H Cobden
- Department of Physics , University of Washington , Seattle , Washington 98195 , United States
| | - Xiaodong Xu
- Department of Physics , University of Washington , Seattle , Washington 98195 , United States
- Department of Materials Science and Engineering , University of Washington , Seattle , Washington 98195 , United States
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7
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Vargunin A, Silaev M. Flux flow spin Hall effect in type-II superconductors with spin-splitting field. Sci Rep 2019; 9:5914. [PMID: 30976007 PMCID: PMC6459863 DOI: 10.1038/s41598-019-42034-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2018] [Accepted: 03/19/2019] [Indexed: 11/09/2022] Open
Abstract
We predict the very large spin Hall effect in type-II superconductors whose mechanism is drastically different from the previously known ones. We find that in the flux-flow regime the spin is transported by the spin-polarized Abrikosov vortices moving under the action of the Lorenz force in the direction perpendicular to the applied electric current. Due to the large vortex velocities the spin Hall angle can be of the order of unity in realistic systems based on the high-field superconductors, superconductor/ferromagnet hybrid structures or the recently developed superconductor/ferromagnetic insulator proximity structures. We propose the realization of high-frequency pure spin current generator based on the periodic structure of moving vortex lattices. We find the patterns of charge imbalance and spin accumulation generated by moving vortices, which can be used for the electrical detection of individual vortex motion. The new mechanism of inverse flux-flow spin Hall effect is found based on the driving force acting on the vortices in the presence of injected spin current which results in the generation of transverse voltage.
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Affiliation(s)
- Artjom Vargunin
- Department of Physics and Nanoscience Center, University of Jyväskylä, Jyväskylä, P.O. Box 35 (YFL), FI-40014, Finland
- Institute of Physics, University of Tartu, Tartu, EE-50411, Estonia
| | - Mikhail Silaev
- Department of Physics and Nanoscience Center, University of Jyväskylä, Jyväskylä, P.O. Box 35 (YFL), FI-40014, Finland.
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8
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De Simoni G, Strambini E, Moodera JS, Bergeret FS, Giazotto F. Toward the Absolute Spin-Valve Effect in Superconducting Tunnel Junctions. NANO LETTERS 2018; 18:6369-6374. [PMID: 30248266 DOI: 10.1021/acs.nanolett.8b02723] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
A superconductor with a spin-split excitation spectrum behaves as an ideal ferromagnetic spin-injector in a tunneling junction. It was theoretically predicted that the combination of two such spin-split superconductors with independently tunable magnetizations may be used as an ideal absolute spin-valve. Here, we report on the first switchable superconducting spin-valve based on two EuS/Al bilayers coupled through an aluminum oxide tunnel barrier. The spin-valve shows a relative resistance change between the parallel and antiparallel configuration of the EuS layers up to 900% that demonstrates a highly spin-polarized current through the junction. Our device may be pivotal for realization of thermoelectric radiation detectors, a logical element for a memory cell in cryogenics, superconductor-based computers, and superconducting spintronics in general.
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Affiliation(s)
- Giorgio De Simoni
- NEST Istituto Nanoscienze-CNR and Scuola Normale Superiore , I-56127 Pisa , Italy
| | - Elia Strambini
- NEST Istituto Nanoscienze-CNR and Scuola Normale Superiore , I-56127 Pisa , Italy
| | - Jagadeesh S Moodera
- Department of Physics, Francis Bitter Magnet Lab and Plasma Science and Fusion Center , Massachusetts Institute of Technology , Cambridge , Massachusetts 02139 , United States
| | - F Sebastian Bergeret
- Centro de Fisica de Materiales (CFM-MPC), Centro Mixto CSIC-UPV/EHU , Manuel de Lardizabal 5 , E-20018 San Sebastian , Spain
- Donostia International Physics Center (DIPC) , Manuel de Lardizabal 4 , E-20018 San Sebastian , Spain
| | - Francesco Giazotto
- NEST Istituto Nanoscienze-CNR and Scuola Normale Superiore , I-56127 Pisa , Italy
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9
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Komori S, Di Bernardo A, Buzdin AI, Blamire MG, Robinson JWA. Magnetic Exchange Fields and Domain Wall Superconductivity at an All-Oxide Superconductor-Ferromagnet Insulator Interface. PHYSICAL REVIEW LETTERS 2018; 121:077003. [PMID: 30169105 DOI: 10.1103/physrevlett.121.077003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2018] [Revised: 05/20/2018] [Indexed: 06/08/2023]
Abstract
At a superconductor-ferromagnet (S/F) interface, the F layer can introduce a magnetic exchange field within the S layer, which acts to locally spin split the superconducting density of states. The effect of magnetic exchange fields on superconductivity has been thoroughly explored at S-ferromagnet insulator (S/FI) interfaces for isotropic s-wave S and a thickness that is smaller than the superconducting coherence length. Here we report a magnetic exchange field effect at an all-oxide S/FI interface involving the anisotropic d-wave high temperature superconductor praseodymium cerium copper oxide (PCCO) and the FI praseodymium calcium manganese oxide (PCMO). The magnetic exchange field in PCCO, detected via magnetotransport measurements through the superconducting transition, is localized to the PCCO/PCMO interface with an average magnitude that depends on the presence or absence of magnetic domain walls in PCMO. The results are promising for the development of all-oxide superconducting spintronic devices involving unconventional pairing and high temperature superconductors.
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Affiliation(s)
- S Komori
- Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, United Kingdom
| | - A Di Bernardo
- Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, United Kingdom
| | - A I Buzdin
- Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, United Kingdom
- University Bordeaux, LOMA UMR-CNRS 5798, F-33405 Talence Cedex, France
| | - M G Blamire
- Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, United Kingdom
| | - J W A Robinson
- Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, United Kingdom
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10
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Kolenda S, Machon P, Beckmann D, Belzig W. Nonlinear thermoelectric effects in high-field superconductor-ferromagnet tunnel junctions. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2016; 7:1579-1585. [PMID: 28144509 PMCID: PMC5238697 DOI: 10.3762/bjnano.7.152] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/04/2016] [Accepted: 10/11/2016] [Indexed: 06/06/2023]
Abstract
Background: Thermoelectric effects result from the coupling of charge and heat transport and can be used for thermometry, cooling and harvesting of thermal energy. The microscopic origin of thermoelectric effects is a broken electron-hole symmetry, which is usually quite small in metal structures. In addition, thermoelectric effects decrease towards low temperatures, which usually makes them vanishingly small in metal nanostructures in the sub-Kelvin regime. Results: We report on a combined experimental and theoretical investigation of thermoelectric effects in superconductor/ferromagnet hybrid structures. We investigate the dependence of thermoelectric currents on the thermal excitation, as well as on the presence of a dc bias voltage across the junction. Conclusion: Large thermoelectric effects are observed in superconductor/ferromagnet and superconductor/normal-metal hybrid structures. The spin-independent signals observed under finite voltage bias are shown to be reciprocal to the physics of superconductor/normal-metal microrefrigerators. The spin-dependent thermoelectric signals in the linear regime are due to the coupling of spin and heat transport, and can be used to design more efficient refrigerators.
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Affiliation(s)
- Stefan Kolenda
- Karlsruher Institut für Technologie (KIT), Institut für Nanotechnologie, P.O. Box 3640, D-72021 Karlsruhe, Germany
| | - Peter Machon
- Department of Physics, University of Konstanz, D-78457 Konstanz, Germany
| | - Detlef Beckmann
- Karlsruher Institut für Technologie (KIT), Institut für Nanotechnologie, P.O. Box 3640, D-72021 Karlsruhe, Germany
| | - Wolfgang Belzig
- Department of Physics, University of Konstanz, D-78457 Konstanz, Germany
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11
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Beckmann D. Spin manipulation in nanoscale superconductors. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2016; 28:163001. [PMID: 27001949 DOI: 10.1088/0953-8984/28/16/163001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The interplay of superconductivity and magnetism in nanoscale structures has attracted considerable attention in recent years due to the exciting new physics created by the competition of these antagonistic ordering phenomena, and the prospect of exploiting this competition for superconducting spintronics devices. While much of the attention is focused on spin-polarized supercurrents created by the triplet proximity effect, the recent discovery of long range quasiparticle spin transport in high-field superconductors has rekindled interest in spin-dependent nonequilibrium properties of superconductors. In this review, the experimental situation on nonequilibrium spin injection into superconductors is discussed, and open questions and possible future directions of the field are outlined.
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Affiliation(s)
- D Beckmann
- Karlsruhe Institute of Technology (KIT), Institute of Nanotechnology, 76021 Karlsruhe, Germany
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Blamire MG, Robinson JWA. The interface between superconductivity and magnetism: understanding and device prospects. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2014; 26:453201. [PMID: 25318455 DOI: 10.1088/0953-8984/26/45/453201] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Ferromagnetism and conventional singlet superconductivity can be regarded as competing ordering phenomena. A considerable body of theoretical work over the past twenty years has predicted that at interfaces between the two systems competition or coupling between superconducting and magnetic phenomena are possible. Despite the very short lengthscales over which some of the phenomena exist, many of these predictions have been experimentally realized. The aim of this topical review is to provide an overview of the experimental position and to discuss the potential developments and applications of existing results.
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Affiliation(s)
- M G Blamire
- Department of Materials Science, University of Cambridge, 27 Charles Babbage Road, Cambridge, UK
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Spin regulation in composite spin-filter barrier devices. Nat Commun 2014; 5:3682. [PMID: 24759596 DOI: 10.1038/ncomms4682] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2013] [Accepted: 03/18/2014] [Indexed: 11/09/2022] Open
Abstract
Magnetic insulators are known to provide large effective Zeeman fields that are confined at an interface, making them especially powerful in modifying adjacent one- or two-dimensional electronic structures. Utilizing this phenomenon and the other important property of magnetic insulators--spin filtering--here we report the generation and subsequent detection of a large interface field, as large as tens of tesla in EuS/Al/EuS heterostructures with metallic coulomb islands confined within a magnetic insulator barrier. The unique energy profile across this sandwich structure produces spin-assisted charge transfer across the device, generating a spontaneous spin current and voltage. These unique properties can be practical for controlling spin flows in electronic devices and for energy harvesting.
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Wei P, Katmis F, Assaf BA, Steinberg H, Jarillo-Herrero P, Heiman D, Moodera JS. Exchange-coupling-induced symmetry breaking in topological insulators. PHYSICAL REVIEW LETTERS 2013; 110:186807. [PMID: 23683236 DOI: 10.1103/physrevlett.110.186807] [Citation(s) in RCA: 90] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2012] [Indexed: 05/22/2023]
Abstract
An exchange gap in the Dirac surface states of a topological insulator (TI) is necessary for observing the predicted unique features such as the topological magnetoelectric effect as well as to confine Majorana fermions. We experimentally demonstrate proximity-induced ferromagnetism in a TI, combining a ferromagnetic insulator EuS layer with Bi(2)Se(3), without introducing defects. By magnetic and magnetotransport studies, including anomalous Hall effect and magnetoresistance measurements, we show the emergence of a ferromagnetic phase in TI, a step forward in unveiling their exotic properties.
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Affiliation(s)
- Peng Wei
- Francis Bitter Magnet Lab, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
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Li B, Roschewsky N, Assaf BA, Eich M, Epstein-Martin M, Heiman D, Münzenberg M, Moodera JS. Superconducting spin switch with infinite magnetoresistance induced by an internal exchange field. PHYSICAL REVIEW LETTERS 2013; 110:097001. [PMID: 23496737 DOI: 10.1103/physrevlett.110.097001] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2012] [Indexed: 06/01/2023]
Abstract
A theoretical prediction by de Gennes suggests that the resistance in a FI/S/FI (where FI is a ferromagnetic insulator, and S is a superconductor) structure will depend on the magnetization direction of the two FI layers. We report a magnetotransport measurement in a EuS/Al/EuS structure, showing that an infinite magnetoresistance can be produced by tuning the internal exchange field at the FI/S interface. This proximity effect at the interface can be suppressed by an Al(2)O(3) barrier as thin as 0.3 nm, showing the extreme confinement of the interaction to the interface giving rise to the demonstrated phenomena.
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Affiliation(s)
- Bin Li
- Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
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Liu TJ, Prestigiacomo JC, Xiong YM, Adams PW. Exchange field-mediated magnetoresistance in the correlated insulator phase of Be films. PHYSICAL REVIEW LETTERS 2012; 109:147207. [PMID: 23083279 DOI: 10.1103/physrevlett.109.147207] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2012] [Indexed: 06/01/2023]
Abstract
We present a study of the proximity effect between a ferromagnet and a paramagnetic metal of varying disorder. Thin beryllium films are deposited onto a 5 nm thick layer of the ferromagnetic insulator EuS. This bilayer arrangement induces an exchange field, H(ex), of a few tesla in low-resistance Be films with sheet resistance R≪R(Q), where R(Q)=h/e2 is the quantum resistance. We show that H(ex) survives in very high-resistance films and, in fact, appears to be relatively insensitive to the Be disorder. We exploit this fact to produce a giant low-field magnetoresistance in the correlated-insulator phase of Be films with R≫R(Q).
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Affiliation(s)
- T J Liu
- Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, USA
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Cottet A. Inducing odd-frequency triplet superconducting correlations in a normal metal. PHYSICAL REVIEW LETTERS 2011; 107:177001. [PMID: 22107564 DOI: 10.1103/physrevlett.107.177001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2011] [Indexed: 05/31/2023]
Abstract
This work discusses theoretically the interplay between the superconducting and ferromagnetic proximity effects, in a diffusive normal metal strip in contact with a superconductor and a nonuniformly magnetized ferromagnetic insulator. The quasiparticle density of states of the normal metal shows clear qualitative signatures of triplet correlations with spin one (TCS1). When one goes away from the superconducting contact, TCS1 focus at zero energy under the form of a peak surrounded by dips, which show a typical spatial scaling behavior. This effect can coexist with a focusing of singlet correlations and triplet correlations with spin zero at finite but subgap energies. The simultaneous observation of both effects would enable an unambiguous characterization of TCS1.
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Affiliation(s)
- Audrey Cottet
- Laboratoire Pierre Aigrain, Ecole Normale Supérieure, CNRS (UMR 8551), Université Pierre et Marie Curie, Université Denis Diderot, 24 rue Lhomond, 75231 Paris Cedex 05, France
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Xiong YM, Stadler S, Adams PW, Catelani G. Spin-resolved tunneling studies of the exchange field in EuS/Al bilayers. PHYSICAL REVIEW LETTERS 2011; 106:247001. [PMID: 21770590 DOI: 10.1103/physrevlett.106.247001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2011] [Indexed: 05/31/2023]
Abstract
We use spin-resolved electron tunneling to study the exchange field in the Al component of EuS/Al bilayers, in both the superconducting and normal-state phases of the Al. Contrary to expectation, we show that the exchange field H(ex) is a nonlinear function of applied field, even in applied fields that are well beyond the EuS coercive field. Furthermore, the magnitude H(ex) is unaffected by the superconducting phase. In addition, H(ex) decreases significantly with increasing temperature in the temperature range of 0.1-1 K. We discuss these results in the context of recent theories of generalized spin-dependent boundary conditions at a superconductor-ferromagnet interface.
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Affiliation(s)
- Y M Xiong
- Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, USA
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Mohite AD, Santos TS, Moodera JS, Alphenaar BW. Observation of the triplet exciton in EuS-coated single-walled nanotubes. NATURE NANOTECHNOLOGY 2009; 4:425-429. [PMID: 19581894 DOI: 10.1038/nnano.2009.122] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2009] [Accepted: 04/28/2009] [Indexed: 05/28/2023]
Abstract
Photon absorption by carbon nanotubes creates bound electron-hole pairs called excitons, which can exist in spin-polarized triplet or spin-unpolarized singlet configurations. Triplet excitons are optically inactive owing to the weak spin-orbit coupling in nanotubes. This prevents the optical injection of electron spin into nanotubes for spintronic applications and limits the efficiency of photocurrent generation. Here, we show that it is possible to optically excite the triplet exciton by using a ferromagnetic semiconductor as a spin filter to mix the singlet and triplet excitons. The triplet contribution to the photocurrent is detected, representing the first direct evidence of the triplet exciton in carbon nanotubes.
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Affiliation(s)
- Aditya D Mohite
- Department of Electrical and Computer Engineering, University of Louisville, Louisville, Kentucky 40292, USA
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Izyumov YA, Proshin YN, Khusainov MG. Competition between superconductivity and magnetism in ferromagnet/superconductor heterostructures. ACTA ACUST UNITED AC 2002. [DOI: 10.3367/ufnr.0172.200202a.0113] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022]
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Krivoruchko VN, Belogolovskii MA. Proximity-induced superconductivity in an antiferromagnetic exchange field. PHYSICAL REVIEW. B, CONDENSED MATTER 1995; 52:9709-9713. [PMID: 9980022 DOI: 10.1103/physrevb.52.9709] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Moodera JS, Meservey R, Hao X. Variation of the electron-spin polarization in EuSe tunnel junctions from zero to near 100% in a magnetic field. PHYSICAL REVIEW LETTERS 1993; 70:853-856. [PMID: 10054220 DOI: 10.1103/physrevlett.70.853] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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