1
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Mao Y, Yan Q, Zhuang YC, Sun QF. Universal Spin Superconducting Diode Effect from Spin-Orbit Coupling. PHYSICAL REVIEW LETTERS 2024; 132:216001. [PMID: 38856265 DOI: 10.1103/physrevlett.132.216001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Revised: 04/11/2024] [Accepted: 04/24/2024] [Indexed: 06/11/2024]
Abstract
We propose a universal spin superconducting diode effect (SDE) induced by spin-orbit coupling (SOC) in systems with spin-triplet correlations, where the critical spin supercurrents in opposite directions are unequal. By analysis from both the Ginzburg-Landau theory and energy band analysis, we show that the spin-↑↑ and spin-↓↓ Cooper pairs possess opposite phase gradients and opposite momenta from the SOC, which leads to the spin SDE. Two superconductors with SOC, a p-wave superconductor as a toy model and a practical superconducting nanowire, are numerically studied and they both exhibit spin SDE. In addition, our theory also provides a unified picture for both spin and charge SDEs.
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Affiliation(s)
- Yue Mao
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Qing Yan
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Yu-Chen Zhuang
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Qing-Feng Sun
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
- Hefei National Laboratory, Hefei 230088, China
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2
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Singh A, Datta S, Pandeya RP, Kandukuri SC, Bapat R, Parmar J, Maiti K. Exceptional behavior of a high-temperature superconductor in proximity to a ferromagnet in a bilayer film, La 0.67Sr 0.33MnO 3/YBa 2Cu 3O 7. NANOSCALE 2024; 16:9819-9826. [PMID: 38700382 DOI: 10.1039/d3nr06636c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2024]
Abstract
We studied the electronic properties of a high-temperature superconductor in proximity to a ferromagnetic material in a bilayer film of La0.67Sr0.33MnO3 (LSMO)/YBa2Cu3O7 (YBCO). High-quality single-crystalline films of YBCO and LSMO/YBCO were grown epitaxially on an SrTiO3 (001) surface. Magnetization data of the LSMO/YBCO bilayer exhibit ferromagnetic transition at about 255 K, which is much smaller than the Curie temperature of bulk LSMO. Experimental data show the emergence of magnetic anisotropy with cooling, which becomes significantly stronger in the superconducting phase. The onset temperature of diamagnetism is observed at 86 K in the YBCO sample for the out-of-plane magnetization and at 89 K in the in-plane data. Interestingly, the diamagnetism sets in at about 86 K for both magnetization directions in the LSMO/YBCO film despite the presence of the ferromagnetic LSMO layer underneath. Ba 4d and Y 3d core-level spectra show different surface and bulk electronic structures. Surface contribution is reduced significantly in the LSMO/YBCO sample, suggesting enhanced bulk-like behavior due to an enhancement of electron density near the surface arising from charge transfer across the interface. These results reveal an outstanding platform for on-demand tuning of properties without affecting the superconductivity of the system for the exploration of fundamental science and applications in advanced technology.
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Affiliation(s)
- Ankita Singh
- Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai-400005, India.
| | - Sawani Datta
- Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai-400005, India.
| | - Ram Prakash Pandeya
- Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai-400005, India.
| | - Srinivas C Kandukuri
- Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai-400005, India.
| | - Rudheer Bapat
- Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai-400005, India.
| | - Jayesh Parmar
- Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai-400005, India.
| | - Kalobaran Maiti
- Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai-400005, India.
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3
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Sanchez-Manzano D, Orfila G, Sander A, Marcano L, Gallego F, Mawass MA, Grilli F, Arora A, Peralta A, Cuellar FA, Fernandez-Roldan JA, Reyren N, Kronast F, Leon C, Rivera-Calzada A, Villegas JE, Santamaria J, Valencia S. Size-Dependence and High Temperature Stability of Radial Vortex Magnetic Textures Imprinted by Superconductor Stray Fields. ACS APPLIED MATERIALS & INTERFACES 2024; 16:19681-19690. [PMID: 38564236 DOI: 10.1021/acsami.3c17671] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/04/2024]
Abstract
Swirling spin textures, including topologically nontrivial states, such as skyrmions, chiral domain walls, and magnetic vortices, have garnered significant attention within the scientific community due to their appeal from both fundamental and applied points of view. However, their creation, controlled manipulation, and stability are typically constrained to certain systems with specific crystallographic symmetries, bulk or interface interactions, and/or a precise stacking sequence of materials. Recently, a new approach has shown potential for the imprint of magnetic radial vortices in soft ferromagnetic compounds making use of the stray field of YBa2Cu3O7-δ superconducting microstructures in ferromagnet/superconductor (FM/SC) hybrids at temperatures below the superconducting transition temperature (TC). Here, we explore the lower size limit for the imprint of magnetic radial vortices in square and disc shaped structures as well as the persistence of these spin textures above TC, with magnetic domains retaining partial memory. Structures with circular geometry and with FM patterned to smaller radius than the superconductor island facilitate the imprinting of magnetic radial vortices and improve their stability above TC, in contrast to square structures where the presence of magnetic domains increases the dipolar energy. Micromagnetic modeling coupled with a SC field model reveals that the stabilization mechanism above TC is mediated by microstructural defects. Superconducting control of swirling spin textures, and their stabilization above the superconducting transition temperature by means of defect engineering holds promising prospects for shaping superconducting spintronics based on magnetic textures.
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Affiliation(s)
- David Sanchez-Manzano
- Laboratoire Albert Fert, CNRS, Thales, Université Paris-Saclay, 91767 Palaiseau, France
- GFMC. Department Física de Materiales. Facultad de Física. Universidad Complutense. 28040 Madrid, Spain
| | - Gloria Orfila
- GFMC. Department Física de Materiales. Facultad de Física. Universidad Complutense. 28040 Madrid, Spain
| | - Anke Sander
- Laboratoire Albert Fert, CNRS, Thales, Université Paris-Saclay, 91767 Palaiseau, France
| | - Lourdes Marcano
- Helmholtz-Zentrum Berlin, Albert-Einstein Str. 15, 12489 Berlin, Germany
- Department of Physics, Faculty of Science, University of Oviedo, 33007 Oviedo, Spain
- Center for Cooperative Research in Biomaterials (CIC biomaGUNE), Basque Research and Technology Alliance (BRTA), Paseo de Miramón 194, 20014 Donostia-San Sebastián, Spain
| | - Fernando Gallego
- GFMC. Department Física de Materiales. Facultad de Física. Universidad Complutense. 28040 Madrid, Spain
| | | | - Francesco Grilli
- Institute for Technical Physics Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen, Germany
| | - Ashima Arora
- Helmholtz-Zentrum Berlin, Albert-Einstein Str. 15, 12489 Berlin, Germany
| | - Andrea Peralta
- GFMC. Department Física de Materiales. Facultad de Física. Universidad Complutense. 28040 Madrid, Spain
| | - Fabian A Cuellar
- GFMC. Department Física de Materiales. Facultad de Física. Universidad Complutense. 28040 Madrid, Spain
| | - Jose A Fernandez-Roldan
- Helmholtz-Zentrum Dresden-Rossendorf e.V., Institute of Ion Beam Physics and Materials Research, 01328 Dresden, Germany
| | - Nicolas Reyren
- Laboratoire Albert Fert, CNRS, Thales, Université Paris-Saclay, 91767 Palaiseau, France
| | - Florian Kronast
- Helmholtz-Zentrum Berlin, Albert-Einstein Str. 15, 12489 Berlin, Germany
| | - Carlos Leon
- GFMC. Department Física de Materiales. Facultad de Física. Universidad Complutense. 28040 Madrid, Spain
| | - Alberto Rivera-Calzada
- GFMC. Department Física de Materiales. Facultad de Física. Universidad Complutense. 28040 Madrid, Spain
| | - Javier E Villegas
- Laboratoire Albert Fert, CNRS, Thales, Université Paris-Saclay, 91767 Palaiseau, France
| | - Jacobo Santamaria
- GFMC. Department Física de Materiales. Facultad de Física. Universidad Complutense. 28040 Madrid, Spain
| | - Sergio Valencia
- Helmholtz-Zentrum Berlin, Albert-Einstein Str. 15, 12489 Berlin, Germany
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4
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Bloom BP, Paltiel Y, Naaman R, Waldeck DH. Chiral Induced Spin Selectivity. Chem Rev 2024; 124:1950-1991. [PMID: 38364021 PMCID: PMC10906005 DOI: 10.1021/acs.chemrev.3c00661] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2023] [Revised: 01/16/2024] [Accepted: 01/23/2024] [Indexed: 02/18/2024]
Abstract
Since the initial landmark study on the chiral induced spin selectivity (CISS) effect in 1999, considerable experimental and theoretical efforts have been made to understand the physical underpinnings and mechanistic features of this interesting phenomenon. As first formulated, the CISS effect refers to the innate ability of chiral materials to act as spin filters for electron transport; however, more recent experiments demonstrate that displacement currents arising from charge polarization of chiral molecules lead to spin polarization without the need for net charge flow. With its identification of a fundamental connection between chiral symmetry and electron spin in molecules and materials, CISS promises profound and ubiquitous implications for existing technologies and new approaches to answering age old questions, such as the homochiral nature of life. This review begins with a discussion of the different methods for measuring CISS and then provides a comprehensive overview of molecules and materials known to exhibit CISS-based phenomena before proceeding to identify structure-property relations and to delineate the leading theoretical models for the CISS effect. Next, it identifies some implications of CISS in physics, chemistry, and biology. The discussion ends with a critical assessment of the CISS field and some comments on its future outlook.
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Affiliation(s)
- Brian P. Bloom
- Department
of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
| | - Yossi Paltiel
- Applied
Physics Department and Center for Nano-Science and Nano-Technology, The Hebrew University of Jerusalem, Jerusalem 9190401, Israel
| | - Ron Naaman
- Department
of Chemical and Biological Physics, Weizmann
Institute, Rehovot 76100, Israel
| | - David H. Waldeck
- Department
of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
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5
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Zhang SB, Hu LH, Neupert T. Finite-momentum Cooper pairing in proximitized altermagnets. Nat Commun 2024; 15:1801. [PMID: 38413591 PMCID: PMC10899178 DOI: 10.1038/s41467-024-45951-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2023] [Accepted: 02/08/2024] [Indexed: 02/29/2024] Open
Abstract
Finite-momentum Cooper pairing is an unconventional form of superconductivity that is widely believed to require finite magnetization. Altermagnetism is an emerging magnetic phase with highly anisotropic spin-splitting of specific symmetries, but zero net magnetization. Here, we study Cooper pairing in metallic altermagnets connected to conventional s-wave superconductors. Remarkably, we find that the Cooper pairs induced in the altermagnets acquire a finite center-of-mass momentum, despite the zero net magnetization in the system. This anomalous Cooper-pair momentum strongly depends on the propagation direction and exhibits unusual symmetric patterns. Furthermore, it yields several unique features: (i) highly orientation-dependent oscillations in the order parameter, (ii) controllable 0-π transitions in the Josephson supercurrent, (iii) large-oblique-angle Cooper-pair transfer trajectories in junctions parallel with the direction where spin splitting vanishes, and (iv) distinct Fraunhofer patterns in junctions oriented along different directions. Finally, we discuss the implementation of our predictions in candidate materials such as RuO2 and KRu4O8.
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Affiliation(s)
- Song-Bo Zhang
- Hefei National Laboratory, Hefei, Anhui, 230088, China.
- International Center for Quantum Design of Functional Materials (ICQD), University of Science and Technology of China, Hefei, Anhui, 230026, China.
- Department of Physics, University of Zürich, Winterthurerstrasse 190, 8057, Zürich, Switzerland.
| | - Lun-Hui Hu
- Department of Applied Physics, Aalto University School of Science, FI-00076, Aalto, Finland.
- Center for Correlated Matter and School of Physics, Zhejiang University, Hangzhou, 310058, China.
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, TN, 37996, USA.
| | - Titus Neupert
- Department of Physics, University of Zürich, Winterthurerstrasse 190, 8057, Zürich, Switzerland
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6
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Li W, Yang DJ, Lu WT. Enhancement and switch effect of equal-spin Andreev reflection in ferromagnet/insulator/Ising superconductor junctions. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2023; 36:135302. [PMID: 38091610 DOI: 10.1088/1361-648x/ad154d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2023] [Accepted: 12/13/2023] [Indexed: 12/29/2023]
Abstract
We study the property of equal-spin Andreev reflection (ESAR) in the ferromagnet/insulator/Ising superconductor junction where Ising spin-orbit coupling is taken into account in the insulator. It is found that the ESAR exhibits a regular oscillation with the insulating barrier, the amplitude and period of which can be effectively controlled by the chemical potentials. Compared to that in the ferromagnet/Ising superconductor junction, the ESAR is greatly increased due to the resonant mode, suggesting an enhanced spin-triplet pairing. As an application, the proposed junction may work as a switch to turn on and off the ESAR. Furthermore, the insulating barrier does not change the magnetoanisotropic period of ESAR because of the invariant symmetry of the system, however, the magnetoanisotropy is strengthened.
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Affiliation(s)
- Wen Li
- School of Information Science and Technology, Nantong University, Nantong 226019, People's Republic of China
| | - De-Jing Yang
- College of Physics, Sichuan University, Chengdu 610064, People's Republic of China
| | - Wei-Tao Lu
- School of Sciences, Nantong University, Nantong 226019, People's Republic of China
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7
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Jo J, Peisen Y, Yang H, Mañas-Valero S, Baldoví JJ, Lu Y, Coronado E, Casanova F, Bergeret FS, Gobbi M, Hueso LE. Local control of superconductivity in a NbSe 2/CrSBr van der Waals heterostructure. Nat Commun 2023; 14:7253. [PMID: 37945570 PMCID: PMC10636142 DOI: 10.1038/s41467-023-43111-7] [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: 10/10/2023] [Accepted: 10/31/2023] [Indexed: 11/12/2023] Open
Abstract
Two-dimensional magnets and superconductors are emerging as tunable building-blocks for quantum computing and superconducting spintronic devices, and have been used to fabricate all two-dimensional versions of traditional devices, such as Josephson junctions. However, novel devices enabled by unique features of two-dimensional materials have not yet been demonstrated. Here, we present NbSe2/CrSBr van der Waals superconducting spin valves that exhibit infinite magnetoresistance and nonreciprocal charge transport. These responses arise from a unique metamagnetic transition in CrSBr, which controls the presence of localized stray fields suitably oriented to suppress the NbSe2 superconductivity in nanoscale regions and to break time reversal symmetry. Moreover, by integrating different CrSBr crystals in a lateral heterostructure, we demonstrate a superconductive spin valve characterized by multiple stable resistance states. Our results show how the unique physical properties of layered materials enable the realization of high-performance quantum devices based on novel working principles.
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Affiliation(s)
- Junhyeon Jo
- CIC nanoGUNE BRTA, Donostia-San Sebastian, Spain.
| | - Yuan Peisen
- CIC nanoGUNE BRTA, Donostia-San Sebastian, Spain
| | - Haozhe Yang
- CIC nanoGUNE BRTA, Donostia-San Sebastian, Spain
| | - Samuel Mañas-Valero
- Instituto de Ciencia Molecular (ICMol), Universitat de València, Paterna, Spain
| | - José J Baldoví
- Instituto de Ciencia Molecular (ICMol), Universitat de València, Paterna, Spain
| | - Yao Lu
- Centro de Física de Materiales (CFM-MPC) Centro Mixto CSIC-UPV/EHU, Donostia-San Sebastian, Spain
| | - Eugenio Coronado
- Instituto de Ciencia Molecular (ICMol), Universitat de València, Paterna, Spain
| | - Fèlix Casanova
- CIC nanoGUNE BRTA, Donostia-San Sebastian, Spain
- IKERBASQUE, Basque Foundation for Science, Bilbao, Spain
| | - F Sebastian Bergeret
- Centro de Física de Materiales (CFM-MPC) Centro Mixto CSIC-UPV/EHU, Donostia-San Sebastian, Spain
- Donostia International Physics Center (DIPC), E-20018, Donostia-San Sebastián, Spain
| | - Marco Gobbi
- Centro de Física de Materiales (CFM-MPC) Centro Mixto CSIC-UPV/EHU, Donostia-San Sebastian, Spain.
- IKERBASQUE, Basque Foundation for Science, Bilbao, Spain.
| | - Luis E Hueso
- CIC nanoGUNE BRTA, Donostia-San Sebastian, Spain.
- IKERBASQUE, Basque Foundation for Science, Bilbao, Spain.
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8
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Flokstra M, Stewart R, Yim CM, Trainer C, Wahl P, Miller D, Satchell N, Burnell G, Luetkens H, Prokscha T, Suter A, Morenzoni E, Bobkova IV, Bobkov AM, Lee S. Spin-orbit driven superconducting proximity effects in Pt/Nb thin films. Nat Commun 2023; 14:5081. [PMID: 37604804 PMCID: PMC10442328 DOI: 10.1038/s41467-023-40757-1] [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: 08/24/2022] [Accepted: 08/07/2023] [Indexed: 08/23/2023] Open
Abstract
Manipulating the spin state of thin layers of superconducting material is a promising route to generate dissipationless spin currents in spintronic devices. Approaches typically focus on using thin ferromagnetic elements to perturb the spin state of the superconducting condensate to create spin-triplet correlations. We have investigated simple structures that generate spin-triplet correlations without using ferromagnetic elements. Scanning tunneling spectroscopy and muon-spin rotation are used to probe the local electronic and magnetic properties of our hybrid structures, demonstrating a paramagnetic contribution to the magnetization that partially cancels the Meissner screening. This spin-orbit generated magnetization is shown to derive from the spin of the equal-spin pairs rather than from their orbital motion and is an important development in the field of superconducting spintronics.
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Affiliation(s)
- Machiel Flokstra
- School of Physics and Astronomy, SUPA, University of St. Andrews, St. Andrews, UK
| | - Rhea Stewart
- School of Physics and Astronomy, SUPA, University of St. Andrews, St. Andrews, UK
- ISIS Neutron and Muon Facility, Rutherford Appleton Laboratory, Science and Technology Facilities Council, Didcot, UK
| | - Chi-Ming Yim
- School of Physics and Astronomy, SUPA, University of St. Andrews, St. Andrews, UK
- Tsung-Dao Lee Institute, Shanghai Jiao Tong University, Shanghai, China
| | - Christopher Trainer
- School of Physics and Astronomy, SUPA, University of St. Andrews, St. Andrews, UK
| | - Peter Wahl
- School of Physics and Astronomy, SUPA, University of St. Andrews, St. Andrews, UK
| | - David Miller
- School of Chemistry, University of St. Andrews, St. Andrews, UK
| | - Nathan Satchell
- School of Physics and Astronomy, University of Leeds, Leeds, UK
| | - Gavin Burnell
- School of Physics and Astronomy, University of Leeds, Leeds, UK
| | - Hubertus Luetkens
- Labor für Myonspinspektroskopie, Paul Scherrer Institut, Villigen PSI, Switzerland
| | - Thomas Prokscha
- Labor für Myonspinspektroskopie, Paul Scherrer Institut, Villigen PSI, Switzerland
| | - Andreas Suter
- Labor für Myonspinspektroskopie, Paul Scherrer Institut, Villigen PSI, Switzerland
| | - Elvezio Morenzoni
- Labor für Myonspinspektroskopie, Paul Scherrer Institut, Villigen PSI, Switzerland
| | - Irina V Bobkova
- Institute of Solid State Physics, Chernogolovka, Russia
- Moscow Institute of Physics and Technology, Dolgoprudny, Russia
- National Research University Higher School of Economics, Moscow, Russia
| | | | - Stephen Lee
- School of Physics and Astronomy, SUPA, University of St. Andrews, St. Andrews, UK.
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9
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Wang Y, Yang SY, Sivakumar PK, Ortiz BR, Teicher SML, Wu H, Srivastava AK, Garg C, Liu D, Parkin SSP, Toberer ES, McQueen T, Wilson SD, Ali MN. Anisotropic proximity-induced superconductivity and edge supercurrent in Kagome metal, K 1-xV 3Sb 5. SCIENCE ADVANCES 2023; 9:eadg7269. [PMID: 37436976 DOI: 10.1126/sciadv.adg7269] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2023] [Accepted: 06/12/2023] [Indexed: 07/14/2023]
Abstract
Materials with Kagome nets are of particular importance for their potential combination of strong correlation, exotic magnetism, and electronic topology. KV3Sb5 was discovered to be a layered topological metal with a Kagome net of vanadium. Here, we fabricated Josephson Junctions of K1-xV3Sb5 and induced superconductivity over long junction lengths. Through magnetoresistance and current versus phase measurements, we observed a magnetic field sweeping direction-dependent magnetoresistance and an anisotropic interference pattern with a Fraunhofer pattern for in-plane magnetic field but a suppression of critical current for out-of-plane magnetic field. These results indicate an anisotropic internal magnetic field in K1-xV3Sb5 that influences the superconducting coupling in the junction, possibly giving rise to spin-triplet superconductivity. In addition, the observation of long-lived fast oscillations shows evidence of spatially localized conducting channels arising from edge states. These observations pave the way for studying unconventional superconductivity and Josephson device based on Kagome metals with electron correlation and topology.
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Affiliation(s)
- Yaojia Wang
- Max Planck Institute of Microstructure Physics, 06108 Halle, Saxony-Anhalt, Germany
- Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands
| | - Shuo-Ying Yang
- Max Planck Institute of Microstructure Physics, 06108 Halle, Saxony-Anhalt, Germany
| | - Pranava K Sivakumar
- Max Planck Institute of Microstructure Physics, 06108 Halle, Saxony-Anhalt, Germany
| | - Brenden R Ortiz
- Materials Department, University of California Santa Barbara, Santa Barbara, CA 93106, USA
| | - Samuel M L Teicher
- Materials Department, University of California Santa Barbara, Santa Barbara, CA 93106, USA
| | - Heng Wu
- Max Planck Institute of Microstructure Physics, 06108 Halle, Saxony-Anhalt, Germany
- Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands
| | - Abhay K Srivastava
- Max Planck Institute of Microstructure Physics, 06108 Halle, Saxony-Anhalt, Germany
| | - Chirag Garg
- Max Planck Institute of Microstructure Physics, 06108 Halle, Saxony-Anhalt, Germany
- IBM Almaden Research Center, San Jose, CA 95120, USA
| | - Defa Liu
- Max Planck Institute of Microstructure Physics, 06108 Halle, Saxony-Anhalt, Germany
- Department of Physics, Beijing Normal University, Beijing 100875, China
| | - Stuart S P Parkin
- Max Planck Institute of Microstructure Physics, 06108 Halle, Saxony-Anhalt, Germany
| | | | | | - Stephen D Wilson
- Materials Department, University of California Santa Barbara, Santa Barbara, CA 93106, USA
| | - Mazhar N Ali
- Max Planck Institute of Microstructure Physics, 06108 Halle, Saxony-Anhalt, Germany
- Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands
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10
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Jeon KR, Hazra BK, Kim JK, Jeon JC, Han H, Meyerheim HL, Kontos T, Cottet A, Parkin SSP. Chiral antiferromagnetic Josephson junctions as spin-triplet supercurrent spin valves and d.c. SQUIDs. NATURE NANOTECHNOLOGY 2023; 18:747-753. [PMID: 36997754 PMCID: PMC10359187 DOI: 10.1038/s41565-023-01336-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2021] [Accepted: 01/31/2023] [Indexed: 06/19/2023]
Abstract
Spin-triplet supercurrent spin valves are of practical importance for the realization of superconducting spintronic logic circuits. In ferromagnetic Josephson junctions, the magnetic-field-controlled non-collinearity between the spin-mixer and spin-rotator magnetizations switches the spin-polarized triplet supercurrents on and off. Here we report an antiferromagnetic equivalent of such spin-triplet supercurrent spin valves in chiral antiferromagnetic Josephson junctions as well as a direct-current superconducting quantum interference device. We employ the topological chiral antiferromagnet Mn3Ge, in which the Berry curvature of the band structure produces fictitious magnetic fields, and the non-collinear atomic-scale spin arrangement accommodates triplet Cooper pairing over long distances (>150 nm). We theoretically verify the observed supercurrent spin-valve behaviours under a small magnetic field of <2 mT for current-biased junctions and the direct-current superconducting quantum interference device functionality. Our calculations reproduce the observed hysteretic field interference of the Josephson critical current and link these to the magnetic-field-modulated antiferromagnetic texture that alters the Berry curvature. Our work employs band topology to control the pairing amplitude of spin-triplet Cooper pairs in a single chiral antiferromagnet.
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Affiliation(s)
- Kun-Rok Jeon
- Max Planck Institute of Microstructure Physics, Halle (Saale), Germany.
- Department of Physics, Chung-Ang University (CAU), Seoul, Republic of Korea.
| | | | - Jae-Keun Kim
- Max Planck Institute of Microstructure Physics, Halle (Saale), Germany
| | - Jae-Chun Jeon
- Max Planck Institute of Microstructure Physics, Halle (Saale), Germany
| | - Hyeon Han
- Max Planck Institute of Microstructure Physics, Halle (Saale), Germany
| | | | - Takis Kontos
- Laboratoire de Physique de l'Ecole normale supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université de Paris, Paris, France
| | - Audrey Cottet
- Laboratoire de Physique de l'Ecole normale supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université de Paris, Paris, France.
| | - Stuart S P Parkin
- Max Planck Institute of Microstructure Physics, Halle (Saale), Germany.
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11
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González-Ruano C, Caso D, Ouassou JA, Tiusan C, Lu Y, Linder J, Aliev FG. Observation of Magnetic State Dependent Thermoelectricity in Superconducting Spin Valves. PHYSICAL REVIEW LETTERS 2023; 130:237001. [PMID: 37354396 DOI: 10.1103/physrevlett.130.237001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2022] [Revised: 03/03/2023] [Accepted: 05/08/2023] [Indexed: 06/26/2023]
Abstract
Superconductor-ferromagnet tunnel junctions demonstrate giant thermoelectric effects that are being exploited to engineer ultrasensitive terahertz radiation detectors. Here, we experimentally observe the recently predicted complete magnetic control over thermoelectric effects in a superconducting spin valve, including the dependence of its sign on the magnetic state of the spin valve. The description of the experimental results is improved by the introduction of an interfacial domain wall in the spin filter layer interfacing the superconductor. Surprisingly, the application of high in-plane magnetic fields induces a double sign inversion of the thermoelectric effect, which exhibits large values even at applied fields twice the superconducting critical field.
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Affiliation(s)
- César González-Ruano
- Departamento Física de la Materia Condensada C-III, Universidad Autónoma de Madrid, Madrid 28049, Spain
| | - Diego Caso
- Departamento Física de la Materia Condensada C-III, Universidad Autónoma de Madrid, Madrid 28049, Spain
| | - Jabir Ali Ouassou
- Center for Quantum Spintronics, Department of Physics, Norwegian University of Science and Technology, NO-M7T9Q Trondheim, Norway
| | - Coriolan Tiusan
- Department of Solid State Physics and Advanced Technologies, Faculty of Physics, Babes-Bolyai University, Cluj Napoca 400114, Romania
- Institut Jean Lamour, Nancy Universitè, 54506 Vandoeuvre-les-Nancy Cedex, France
| | - Yuan Lu
- Institut Jean Lamour, Nancy Universitè, 54506 Vandoeuvre-les-Nancy Cedex, France
| | - Jacob Linder
- Center for Quantum Spintronics, Department of Physics, Norwegian University of Science and Technology, NO-M7T9Q Trondheim, Norway
| | - Farkhad G Aliev
- Departamento Física de la Materia Condensada C-III, Instituto Nicolás Cabrera (INC) and Condensed Matter Physics Institute (IFIMAC), Universidad Autónoma de Madrid, Madrid 28049, Spain
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12
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Díez-Mérida J, Díez-Carlón A, Yang SY, Xie YM, Gao XJ, Senior J, Watanabe K, Taniguchi T, Lu X, Higginbotham AP, Law KT, Efetov DK. Symmetry-broken Josephson junctions and superconducting diodes in magic-angle twisted bilayer graphene. Nat Commun 2023; 14:2396. [PMID: 37100775 PMCID: PMC10133447 DOI: 10.1038/s41467-023-38005-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2023] [Accepted: 04/06/2023] [Indexed: 04/28/2023] Open
Abstract
The coexistence of gate-tunable superconducting, magnetic and topological orders in magic-angle twisted bilayer graphene provides opportunities for the creation of hybrid Josephson junctions. Here we report the fabrication of gate-defined symmetry-broken Josephson junctions in magic-angle twisted bilayer graphene, where the weak link is gate-tuned close to the correlated insulator state with a moiré filling factor of υ = -2. We observe a phase-shifted and asymmetric Fraunhofer pattern with a pronounced magnetic hysteresis. Our theoretical calculations of the junction weak link-with valley polarization and orbital magnetization-explain most of these unconventional features. The effects persist up to the critical temperature of 3.5 K, with magnetic hysteresis observed below 800 mK. We show how the combination of magnetization and its current-induced magnetization switching allows us to realise a programmable zero-field superconducting diode. Our results represent a major advance towards the creation of future superconducting quantum electronic devices.
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Affiliation(s)
- J Díez-Mérida
- ICFO - Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, Castelldefels, Barcelona, 08860, Spain
| | - A Díez-Carlón
- ICFO - Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, Castelldefels, Barcelona, 08860, Spain
| | - S Y Yang
- ICFO - Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, Castelldefels, Barcelona, 08860, Spain
| | - Y-M Xie
- Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China
| | - X-J Gao
- Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China
| | - J Senior
- IST Austria, Am Campus 1, 3400, Klosterneuburg, Austria
| | - K Watanabe
- National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - T Taniguchi
- National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - X Lu
- ICFO - Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, Castelldefels, Barcelona, 08860, Spain
| | | | - K T Law
- Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China
| | - Dmitri K Efetov
- ICFO - Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, Castelldefels, Barcelona, 08860, Spain.
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13
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Hu G, Wang C, Wang S, Zhang Y, Feng Y, Wang Z, Niu Q, Zhang Z, Xiang B. Long-range skin Josephson supercurrent across a van der Waals ferromagnet. Nat Commun 2023; 14:1779. [PMID: 36997575 PMCID: PMC10063542 DOI: 10.1038/s41467-023-37603-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2022] [Accepted: 03/23/2023] [Indexed: 04/01/2023] Open
Abstract
AbstractThe emerging field of superconducting spintronics promises new quantum device architectures without energy dissipation. When entering a ferromagnet, a supercurrent commonly behaves as a spin singlet that decays rapidly; in contrast, a spin-triplet supercurrent can transport over much longer distances, and is therefore more desirable, but so far has been observed much less frequently. Here, by using the van der Waals ferromagnet Fe3GeTe2 (F) and spin-singlet superconductor NbSe2 (S), we construct lateral Josephson junctions of S/F/S with accurate interface control to realize long-range skin supercurrent. The observed supercurrent across the ferromagnet can extend over 300 nm, and exhibits distinct quantum interference patterns in an external magnetic field. Strikingly, the supercurrent displays pronounced skin characteristics, with its density peaked at the surfaces or edges of the ferromagnet. Our central findings shed new light on the convergence of superconductivity and spintronics based on two-dimensional materials.
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14
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Zhang G, Cui S, Zhang H, Feng Z, Wang G, Wang Q, Li Y, Liu C. High-pressure magnetic properties and electrical transport behaviors of half-metallic ferromagnet CrO 2. Phys Chem Chem Phys 2023; 25:7366-7372. [PMID: 36825775 DOI: 10.1039/d2cp05684d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
Abstract
The magnetic properties and electrical transport behaviors of half-metallic ferromagnet chromium dioxide (CrO2) powders under high pressure have been investigated by in situ electrical resistivity, magneto-resistivity, and Hall-effect measurements. Our results reveal that the Hall coefficient, carrier concentration, and mobility all present discontinuous changes from 11.7 GPa to 14.9 GPa which can be attributed to the second-order structural transition from the rutile-type to CaCl2-type. However, the resistivity decreases monotonically from ambient pressure to 16.5 GPa. This is due to, first, the decreased carrier concentration and the increased carrier mobility canceling the effects of each other on the resistivity; second, according to the calculation results, the bandgap of CrO2 decreased gradually with the pressure, and the bandgaps of the rutile-type phase and the CaCl2-type phase are extremely similar. CrO2 exhibits a linear and negative magnetoresistance under the applied magnetic field (0∼ ± 15 kOe). As the pressure increases, the magnetoresistance remains negative, but it becomes nonlinear and less symmetric, suggesting that pressure has an appreciable impact on the double-exchange mechanism leading to ferromagnetism in CrO2.
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Affiliation(s)
- Guozhao Zhang
- Shandong Key Laboratory of Optical Communication Science and Technology, School of Physical Science & Information Technology of Liaocheng University, Liaocheng 252059, China.
| | - Shouxin Cui
- Shandong Key Laboratory of Optical Communication Science and Technology, School of Physical Science & Information Technology of Liaocheng University, Liaocheng 252059, China.
| | - Haiwa Zhang
- Shandong Key Laboratory of Optical Communication Science and Technology, School of Physical Science & Information Technology of Liaocheng University, Liaocheng 252059, China.
| | - Zhenbao Feng
- Shandong Key Laboratory of Optical Communication Science and Technology, School of Physical Science & Information Technology of Liaocheng University, Liaocheng 252059, China.
| | - Guangyu Wang
- Shandong Key Laboratory of Optical Communication Science and Technology, School of Physical Science & Information Technology of Liaocheng University, Liaocheng 252059, China.
| | - Qinglin Wang
- Shandong Key Laboratory of Optical Communication Science and Technology, School of Physical Science & Information Technology of Liaocheng University, Liaocheng 252059, China.
| | - Yinwei Li
- Shandong Key Laboratory of Optical Communication Science and Technology, School of Physical Science & Information Technology of Liaocheng University, Liaocheng 252059, China. .,Laboratory of Quantum Functional Materials Design and Application, School of Physics and Electronic Engineering, Jiangsu Normal University, Xuzhou 221116, China
| | - Cailong Liu
- Shandong Key Laboratory of Optical Communication Science and Technology, School of Physical Science & Information Technology of Liaocheng University, Liaocheng 252059, China.
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15
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Machon P, Wolf MJ, Beckmann D, Belzig W. Experimental and theoretical study of field-dependent spin splitting at ferromagnetic insulator-superconductor interfaces. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2022; 13:682-688. [PMID: 35957675 PMCID: PMC9344541 DOI: 10.3762/bjnano.13.60] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/10/2022] [Accepted: 06/08/2022] [Indexed: 06/15/2023]
Abstract
We present a combined experimental and theoretical work that investigates the magnetic proximity effect at a ferromagnetic insulator-superconductor (FI-S) interface. The calculations are based on the boundary condition for diffusive quasiclassical Green's functions, which accounts for arbitrarily strong spin-dependent effects and spin mixing angles. The resulting phase diagram shows a transition from a first-order to a second-order phase transition for large spin mixing angles. The experimentally found differential conductance of an EuS-Al heterostructure is compared with the theoretical calculation. With the assumption of a uniform spin mixing angle that depends on the externally applied field, we find good agreement between theory and experiment. The theory depends only on very few parameters, mostly specified by the experimental setup. We determine the effective spin of the interface moments as J ≈ 0.74ℏ.
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Affiliation(s)
- Peter Machon
- Department of Physics, University of Konstanz, D-78457 Konstanz, Germany
| | - Michael J Wolf
- Institute of Nanotechnology, Karlsruhe Institute of Technology (KIT), D-76021 Karlsruhe, Germany
- present address: Institute for Technical Physics, Karlsruhe Institute of Technology (KIT), D-76021 Karlsruhe, Germany
| | - Detlef Beckmann
- Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology (KIT), D-76021 Karlsruhe, Germany
| | - Wolfgang Belzig
- Department of Physics, University of Konstanz, D-78457 Konstanz, Germany
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16
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Bobkova IV, Bobkov AM, Silaev MA. Magnetoelectric effects in Josephson junctions. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 34:353001. [PMID: 35709718 DOI: 10.1088/1361-648x/ac7994] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2021] [Accepted: 06/16/2022] [Indexed: 06/15/2023]
Abstract
The review is devoted to the fundamental aspects and characteristic features of the magnetoelectric effects, reported in the literature on Josephson junctions (JJs). The main focus of the review is on the manifestations of the direct and inverse magnetoelectric effects in various types of Josephson systems. They provide a coupling of the magnetization in superconductor/ferromagnet/superconductor JJs to the Josephson current. The direct magnetoelectric effect is a driving force of spin torques acting on the ferromagnet inside the JJ. Therefore it is of key importance for the electrical control of the magnetization. The inverse magnetoelectric effect accounts for the back action of the magnetization dynamics on the Josephson subsystem, in particular, making the JJ to be in the resistive state in the presence of the magnetization dynamics of any origin. The perspectives of the coupling of the magnetization in JJs with ferromagnetic interlayers to the Josephson current via the magnetoelectric effects are discussed.
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Affiliation(s)
- I V Bobkova
- Institute of Solid State Physics, Chernogolovka, Moscow Region 142432, Russia
- Moscow Institute of Physics and Technology, Dolgoprudny 141700, Russia
- National Research University Higher School of Economics, Moscow 101000, Russia
| | - A M Bobkov
- Institute of Solid State Physics, Chernogolovka, Moscow Region 142432, Russia
- Moscow Institute of Physics and Technology, Dolgoprudny 141700, Russia
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17
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Bromley D, Wright AJ, Jones LAH, Swallow JEN, Beesley T, Batty R, Weatherup RS, Dhanak VR, O'Brien L. Electron beam evaporation of superconductor-ferromagnet heterostructures. Sci Rep 2022; 12:7786. [PMID: 35545648 PMCID: PMC9095728 DOI: 10.1038/s41598-022-11828-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Accepted: 04/29/2022] [Indexed: 11/09/2022] Open
Abstract
We report on the electronic and magnetic properties of superconductor-ferromagnet heterostructures fabricated by electron beam evaporation on to unheated thermally oxidised Si substrates. Polycrystalline Nb thin films (5 to 50 nm thick) were shown to possess reliably high superconducting critical temperatures (\documentclass[12pt]{minimal}
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\begin{document}$$T_{c}$$\end{document}Tc), which correlate well with the residual resistivity ratio (RRR) of the film. These properties improved during ex-situ annealing, resulting in \documentclass[12pt]{minimal}
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\begin{document}$${\Delta }$$\end{document}ΔRRR increases of up 2.2 K (\documentclass[12pt]{minimal}
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\begin{document}$$\sim$$\end{document}∼ 40% of the pre-annealed \documentclass[12pt]{minimal}
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\begin{document}$$\sim$$\end{document}∼ 60% of the pre-annealed RRR) respectively. Nb/Pt/Co/Pt heterostructures showed substantial perpendicular anisotropy in the ultrathin limit (≤ 2.5 nm), even in the extreme limit of Pt(0.8 nm)/Co(1 nm)/Pt(0.6 nm). These results point to the use of electron beam evaporation as route to line-of-sight deposited, low-thickness, high quality Nb-based superspintronic multilayers.
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Affiliation(s)
- D Bromley
- Department of Physics, University of Liverpool, Liverpool, L69 7ZE, UK
| | - A J Wright
- Department of Physics, University of Liverpool, Liverpool, L69 7ZE, UK
| | - L A H Jones
- Department of Physics, University of Liverpool, Liverpool, L69 7ZE, UK
| | - J E N Swallow
- Department of Materials, University of Oxford, Parks Road, Oxford, OX1 3PH, UK
| | - T Beesley
- Department of Physics, University of Liverpool, Liverpool, L69 7ZE, UK
| | - R Batty
- Department of Physics, University of Liverpool, Liverpool, L69 7ZE, UK
| | - R S Weatherup
- Department of Materials, University of Oxford, Parks Road, Oxford, OX1 3PH, UK
| | - V R Dhanak
- Department of Physics, University of Liverpool, Liverpool, L69 7ZE, UK
| | - L O'Brien
- Department of Physics, University of Liverpool, Liverpool, L69 7ZE, UK.
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18
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Zhao D, Zhao Z, Xu Y, Tong S, Lu J, Wei D. Transverse Magnetoresistance Induced by the Nonuniformity of Superconductor. NANOMATERIALS 2022; 12:nano12081313. [PMID: 35458021 PMCID: PMC9031214 DOI: 10.3390/nano12081313] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/12/2022] [Revised: 03/28/2022] [Accepted: 04/09/2022] [Indexed: 12/10/2022]
Abstract
The transverse magnetoresistance (Rxy) caused by inhomogeneous superconductivity is symmetric about the magnetic field around the critical magnetic field region. This has caused many disturbances during the study of vortex dynamics by Hall signals. Here, we found that the peak of Rxy measured in our samples was induced by the nonuniformity of the superconductors. The peak values of Rxy decrease with increasing applied current and temperature, which can be described by the theory of superconductivity inhomogeneity. Based on this, we have proposed and verified a method for separating the transverse voltage caused by the inhomogeneity of superconductivity. Additionally, quantity ΔB(0) can also be used to characterize the uniformity of superconductivity. This clears up the obstacles for studying vortex motion dynamics and reveals a way to study the influence of the domain wall on superconductivity.
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Affiliation(s)
- Duo Zhao
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China; (D.Z.); (Z.Z.); (Y.X.)
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100190, China
| | - Zhiyuan Zhao
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China; (D.Z.); (Z.Z.); (Y.X.)
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100190, China
| | - Yaohan Xu
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China; (D.Z.); (Z.Z.); (Y.X.)
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100190, China
| | - Shucheng Tong
- Beijing Academy of Quantum Information Sciences, Beijing 100193, China; (S.T.); (J.L.)
| | - Jun Lu
- Beijing Academy of Quantum Information Sciences, Beijing 100193, China; (S.T.); (J.L.)
| | - Dahai Wei
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China; (D.Z.); (Z.Z.); (Y.X.)
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100190, China
- Correspondence: ; Tel.: +86-10-8230-4515; Fax: +86-10-8230-5056
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19
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Fermin R, van Dinter D, Hubert M, Woltjes B, Silaev M, Aarts J, Lahabi K. Superconducting Triplet Rim Currents in a Spin-Textured Ferromagnetic Disk. NANO LETTERS 2022; 22:2209-2216. [PMID: 35239357 PMCID: PMC8949790 DOI: 10.1021/acs.nanolett.1c04051] [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: 10/19/2021] [Revised: 02/23/2022] [Indexed: 06/14/2023]
Abstract
Since the discovery of the long-range superconducting proximity effect, the interaction between spin-triplet Cooper pairs and magnetic structures such as domain walls and vortices has been the subject of intense theoretical discussions, while the relevant experiments remain scarce. We have developed nanostructured Josephson junctions with highly controllable spin texture, based on a disk-shaped Nb/Co bilayer. Here, the vortex magnetization of Co and the Cooper pairs of Nb conspire to induce long-range triplet (LRT) superconductivity in the ferromagnet. Surprisingly, the LRT correlations emerge in highly localized (sub-80 nm) channels at the rim of the ferromagnet, despite its trivial band structure. We show that these robust rim currents arise from the magnetization texture acting as an effective spin-orbit coupling, which results in spin accumulation at the bilayer-vacuum boundary. Lastly, we demonstrate that by altering the spin texture of a single ferromagnet, both 0 and π channels can be realized in the same device.
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Affiliation(s)
- Remko Fermin
- Huygens-Kamerlingh
Onnes Laboratory, Leiden University, P.O. Box 9504, 2300 RA Leiden, The Netherlands
| | - Dyon van Dinter
- Huygens-Kamerlingh
Onnes Laboratory, Leiden University, P.O. Box 9504, 2300 RA Leiden, The Netherlands
| | - Michel Hubert
- Huygens-Kamerlingh
Onnes Laboratory, Leiden University, P.O. Box 9504, 2300 RA Leiden, The Netherlands
| | - Bart Woltjes
- Huygens-Kamerlingh
Onnes Laboratory, Leiden University, P.O. Box 9504, 2300 RA Leiden, The Netherlands
| | - Mikhail Silaev
- Department
of Physics and Nanoscience Center, University
of Jyväskylä, P.O. Box 35 (YFL), FI-40014 Jyväskylä, Finland
- Computational
Physics Laboratory, Physics Unit, Faculty of Engineering and Natural
Sciences, Tampere University, P.O. Box 692, FI-33014 Tampere, Finland
| | - Jan Aarts
- Huygens-Kamerlingh
Onnes Laboratory, Leiden University, P.O. Box 9504, 2300 RA Leiden, The Netherlands
| | - Kaveh Lahabi
- Huygens-Kamerlingh
Onnes Laboratory, Leiden University, P.O. Box 9504, 2300 RA Leiden, The Netherlands
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20
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Birge NO. Supercurrents in magnetic materials heat up. NATURE MATERIALS 2022; 21:137-138. [PMID: 35110744 DOI: 10.1038/s41563-021-01189-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Affiliation(s)
- Norman O Birge
- Department of Physics and Astronomy, Michigan State University, East Lansing, MI, USA.
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21
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Sanchez-Manzano D, Mesoraca S, Cuellar FA, Cabero M, Rouco V, Orfila G, Palermo X, Balan A, Marcano L, Sander A, Rocci M, Garcia-Barriocanal J, Gallego F, Tornos J, Rivera A, Mompean F, Garcia-Hernandez M, Gonzalez-Calbet JM, Leon C, Valencia S, Feuillet-Palma C, Bergeal N, Buzdin AI, Lesueur J, Villegas JE, Santamaria J. Extremely long-range, high-temperature Josephson coupling across a half-metallic ferromagnet. NATURE MATERIALS 2022; 21:188-194. [PMID: 34857910 DOI: 10.1038/s41563-021-01162-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2020] [Accepted: 10/21/2021] [Indexed: 06/13/2023]
Abstract
The Josephson effect results from the coupling of two superconductors across a spacer such as an insulator, a normal metal or a ferromagnet to yield a phase coherent quantum state. However, in junctions with ferromagnetic spacers, very long-range Josephson effects have remained elusive. Here we demonstrate extremely long-range (micrometric) high-temperature (tens of kelvins) Josephson coupling across the half-metallic manganite La0.7Sr0.3MnO3 combined with the superconducting cuprate YBa2Cu3O7. These planar junctions, in addition to large critical currents, display the hallmarks of Josephson physics, such as critical current oscillations driven by magnetic flux quantization and quantum phase locking effects under microwave excitation (Shapiro steps). The latter display an anomalous doubling of the Josephson frequency predicted by several theories. In addition to its fundamental interest, the marriage between high-temperature, dissipationless quantum coherent transport and full spin polarization brings opportunities for the practical realization of superconducting spintronics, and opens new perspectives for quantum computing.
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Affiliation(s)
- D Sanchez-Manzano
- GFMC, Departamento Fisica de Materiales, Facultad de Fisica, Universidad Complutense, Madrid, Spain
| | - S Mesoraca
- Unité Mixte de Physique, CNRS, Thales, Université Paris-Saclay, Palaiseau, France
| | - F A Cuellar
- GFMC, Departamento Fisica de Materiales, Facultad de Fisica, Universidad Complutense, Madrid, Spain
| | - M Cabero
- IMDEA Nanoscience Institute, Universidad Autonoma, Cantoblanco, Spain
- Centro Nacional de Microscopia Electronica, Universidad Complutense, Madrid, Spain
| | - V Rouco
- GFMC, Departamento Fisica de Materiales, Facultad de Fisica, Universidad Complutense, Madrid, Spain
| | - G Orfila
- GFMC, Departamento Fisica de Materiales, Facultad de Fisica, Universidad Complutense, Madrid, Spain
| | - X Palermo
- Unité Mixte de Physique, CNRS, Thales, Université Paris-Saclay, Palaiseau, France
| | - A Balan
- Unité Mixte de Physique, CNRS, Thales, Université Paris-Saclay, Palaiseau, France
| | - L Marcano
- Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin, Germany
| | - A Sander
- Unité Mixte de Physique, CNRS, Thales, Université Paris-Saclay, Palaiseau, France
| | - M Rocci
- GFMC, Departamento Fisica de Materiales, Facultad de Fisica, Universidad Complutense, Madrid, Spain
- Instituto Nanoscienze, Consiglio Thales Alenia Space Italia, L'Aquila, Italy
| | | | - F Gallego
- GFMC, Departamento Fisica de Materiales, Facultad de Fisica, Universidad Complutense, Madrid, Spain
| | - J Tornos
- GFMC, Departamento Fisica de Materiales, Facultad de Fisica, Universidad Complutense, Madrid, Spain
| | - A Rivera
- GFMC, Departamento Fisica de Materiales, Facultad de Fisica, Universidad Complutense, Madrid, Spain
| | - F Mompean
- Instituto de Ciencia de Materiales de Madrid (ICMM, CSIC), Cantoblanco, Spain
- Laboratorio de Heteroestructuras con Aplicación en Spintrónica, Unidad Asociada (UCM-CSIC), Madrid, Spain
| | - M Garcia-Hernandez
- Instituto de Ciencia de Materiales de Madrid (ICMM, CSIC), Cantoblanco, Spain
- Laboratorio de Heteroestructuras con Aplicación en Spintrónica, Unidad Asociada (UCM-CSIC), Madrid, Spain
| | - J M Gonzalez-Calbet
- Centro Nacional de Microscopia Electronica, Universidad Complutense, Madrid, Spain
- Departamento Química Inorgánica, Facultad de Química, Universidad Complutense, Madrid, Spain
| | - C Leon
- GFMC, Departamento Fisica de Materiales, Facultad de Fisica, Universidad Complutense, Madrid, Spain
| | - S Valencia
- Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin, Germany
| | - C Feuillet-Palma
- Laboratoire de Physique et d'Etude des Matériaux, ESPCI Paris, CNRS, PSL Research University, Sorbonne University, Paris, France
| | - N Bergeal
- Laboratoire de Physique et d'Etude des Matériaux, ESPCI Paris, CNRS, PSL Research University, Sorbonne University, Paris, France
| | - A I Buzdin
- LOMA, CNRS, Université Bordeaux, Talence, France
- Digital Biodesign and Personalized Healthcare, Sechenov First Moscow State Medical University, Moscow, Russia
| | - J Lesueur
- Laboratoire de Physique et d'Etude des Matériaux, ESPCI Paris, CNRS, PSL Research University, Sorbonne University, Paris, France
| | - Javier E Villegas
- Unité Mixte de Physique, CNRS, Thales, Université Paris-Saclay, Palaiseau, France.
| | - J Santamaria
- GFMC, Departamento Fisica de Materiales, Facultad de Fisica, Universidad Complutense, Madrid, Spain.
- Laboratorio de Heteroestructuras con Aplicación en Spintrónica, Unidad Asociada (UCM-CSIC), Madrid, Spain.
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22
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Koren G, Eyal A, Iomin L, Nitzav Y. Observation of Josephson-like Tunneling Junction Characteristics and Positive Magnetoresistance in Oxygen Deficient Nickelate Films of Nd 0.8Sr 0.2NiO 3-δ. MATERIALS (BASEL, SWITZERLAND) 2021; 14:7689. [PMID: 34947282 PMCID: PMC8707323 DOI: 10.3390/ma14247689] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/26/2021] [Revised: 09/13/2021] [Accepted: 12/08/2021] [Indexed: 11/16/2022]
Abstract
Nickelate films have recently attracted broad attention due to the observation of superconductivity in the infinite layer phase of Nd0.8Sr0.2NiO2 (obtained by reducing Sr doped NdNiO3 films) and their similarity to the cuprates high temperature superconductors. Here, we report on the observation of a new type of transport in oxygen poor Nd0.8Sr0.2NiO3-δ films. At high temperatures, variable range hopping is observed while at low temperatures a novel tunneling behavior is found where a Josephson-like tunneling junction characteristic with serial resistance is revealed. We attribute this phenomenon to coupling between superconductive (S) surfaces of the grains in our Oxygen poor films via the insulating (I) grain boundaries, which yields SIS junctions in series with the normal (N) resistance of the grains themselves. The similarity of the observed conductance spectra to the tunneling junction characteristic with Josephson-like current is striking, and seems to support the existence of superconductivity in our samples.
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Affiliation(s)
- Gad Koren
- Department of Physics, Technion—Israel Institute of Technology, Haifa 32000, Israel; (A.E.); (L.I.); (Y.N.)
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23
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Johnsen LG, Simensen HT, Brataas A, Linder J. Magnon Spin Current Induced by Triplet Cooper Pair Supercurrents. PHYSICAL REVIEW LETTERS 2021; 127:207001. [PMID: 34860055 DOI: 10.1103/physrevlett.127.207001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2021] [Accepted: 10/15/2021] [Indexed: 06/13/2023]
Abstract
At the interface between a ferromagnetic insulator and a superconductor there is a coupling between the spins of the two materials. We show that when a supercurrent carried by triplet Cooper pairs flows through the superconductor, the coupling induces a magnon spin current in the adjacent ferromagnetic insulator. The effect is dominated by Cooper pairs polarized in the same direction as the ferromagnetic insulator, so that charge and spin supercurrents produce similar results. Our findings demonstrate a way of converting Cooper pair supercurrents to magnon spin currents.
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Affiliation(s)
- Lina G Johnsen
- Center for Quantum Spintronics, Department of Physics, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway
| | - Haakon T Simensen
- Center for Quantum Spintronics, Department of Physics, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway
| | - Arne Brataas
- Center for Quantum Spintronics, Department of Physics, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway
| | - Jacob Linder
- Center for Quantum Spintronics, Department of Physics, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway
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24
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Jeon KR, Hazra BK, Cho K, Chakraborty A, Jeon JC, Han H, Meyerheim HL, Kontos T, Parkin SSP. Long-range supercurrents through a chiral non-collinear antiferromagnet in lateral Josephson junctions. NATURE MATERIALS 2021; 20:1358-1363. [PMID: 34354216 PMCID: PMC8463295 DOI: 10.1038/s41563-021-01061-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/20/2021] [Accepted: 06/22/2021] [Indexed: 06/13/2023]
Abstract
The proximity-coupling of a chiral non-collinear antiferromagnet (AFM)1-5 with a singlet superconductor allows spin-unpolarized singlet Cooper pairs to be converted into spin-polarized triplet pairs6-8, thereby enabling non-dissipative, long-range spin correlations9-14. The mechanism of this conversion derives from fictitious magnetic fields that are created by a non-zero Berry phase15 in AFMs with non-collinear atomic-scale spin arrangements1-5. Here we report long-ranged lateral Josephson supercurrents through an epitaxial thin film of the triangular chiral AFM Mn3Ge (refs. 3-5). The Josephson supercurrents in this chiral AFM decay by approximately one to two orders of magnitude slower than would be expected for singlet pair correlations9-14 and their response to an external magnetic field reflects a clear spatial quantum interference. Given the long-range supercurrents present in both single- and mixed-phase Mn3Ge, but absent in a collinear AFM IrMn16, our results pave a way for the topological generation of spin-polarized triplet pairs6-8 via Berry phase engineering15 of the chiral AFMs.
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Affiliation(s)
- Kun-Rok Jeon
- Max Planck Institute of Microstructure Physics, Halle (Saale), Germany.
| | | | - Kyungjune Cho
- Max Planck Institute of Microstructure Physics, Halle (Saale), Germany
| | | | - Jae-Chun Jeon
- Max Planck Institute of Microstructure Physics, Halle (Saale), Germany
| | - Hyeon Han
- Max Planck Institute of Microstructure Physics, Halle (Saale), Germany
| | | | - Takis Kontos
- Laboratoire de Physique de l'Ecole Normale Supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université de Paris, Paris, France
| | - Stuart S P Parkin
- Max Planck Institute of Microstructure Physics, Halle (Saale), Germany.
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25
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Xu SY, Ma Q. Supercurrents in a topological antiferromagnet. NATURE MATERIALS 2021; 20:1306-1307. [PMID: 34561626 DOI: 10.1038/s41563-021-01100-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Affiliation(s)
- Su-Yang Xu
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA.
| | - Qiong Ma
- Department of Physics, Boston College, Chestnut Hill, MA, USA
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26
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González-Ruano C, Caso D, Johnsen LG, Tiusan C, Hehn M, Banerjee N, Linder J, Aliev FG. Superconductivity assisted change of the perpendicular magnetic anisotropy in V/MgO/Fe junctions. Sci Rep 2021; 11:19041. [PMID: 34561472 PMCID: PMC8463706 DOI: 10.1038/s41598-021-98079-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2021] [Accepted: 08/30/2021] [Indexed: 11/28/2022] Open
Abstract
Controlling the perpendicular magnetic anisotropy (PMA) in thin films has received considerable attention in recent years due to its technological importance. PMA based devices usually involve heavy-metal (oxide)/ferromagnetic-metal bilayers, where, thanks to interfacial spin-orbit coupling (SOC), the in-plane (IP) stability of the magnetisation is broken. Here we show that in V/MgO/Fe(001) epitaxial junctions with competing in-plane and out-of-plane (OOP) magnetic anisotropies, the SOC mediated interaction between a ferromagnet (FM) and a superconductor (SC) enhances the effective PMA below the superconducting transition. This produces a partial magnetisation reorientation without any applied field for all but the largest junctions, where the IP anisotropy is more robust; for the smallest junctions there is a reduction of the field required to induce a complete OOP transition (\documentclass[12pt]{minimal}
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\begin{document}$$H_\text {OOP}$$\end{document}HOOP) due to the stronger competition between the IP and OOP anisotropies. Our results suggest that the degree of effective PMA could be controlled by the junction lateral size in the presence of superconductivity and an applied electric field. We also discuss how the \documentclass[12pt]{minimal}
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\begin{document}$$H_\text {OOP}$$\end{document}HOOP field could be affected by the interaction between magnetic stray fields and superconducting vortices. Our experimental findings, supported by numerical modelling of the ferromagnet-superconductor interaction, open pathways to active control of magnetic anisotropy in the emerging dissipation-free superconducting spin electronics.
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Affiliation(s)
- César González-Ruano
- Departamento Física de la Materia Condensada C-III, Instituto Nicolás Cabrera (INC) and Condensed Matter Physics Institute (IFIMAC), Universidad Autónoma de Madrid, Madrid, 28049, Spain
| | - Diego Caso
- Departamento Física de la Materia Condensada C-III, Instituto Nicolás Cabrera (INC) and Condensed Matter Physics Institute (IFIMAC), Universidad Autónoma de Madrid, Madrid, 28049, Spain
| | - Lina G Johnsen
- Department of Physics, Center for Quantum Spintronics, Norwegian University of Science and Technology, 7491, Trondheim, Norway
| | - Coriolan Tiusan
- Department of Physics and Chemistry, Center of Superconductivity Spintronics and Surface Science C4S, Technical University of Cluj-Napoca, Cluj-Napoca, 400114, Romania.,Institut Jean Lamour, Nancy Universitè, 54506, Vandoeuvre-les-Nancy Cedex, France
| | - Michel Hehn
- Institut Jean Lamour, Nancy Universitè, 54506, Vandoeuvre-les-Nancy Cedex, France
| | - Niladri Banerjee
- Department of Physics, Loughborough University, Epinal Way, Loughborough, LE11 3TU, UK
| | - Jacob Linder
- Department of Physics, Center for Quantum Spintronics, Norwegian University of Science and Technology, 7491, Trondheim, Norway
| | - Farkhad G Aliev
- Departamento Física de la Materia Condensada C-III, Instituto Nicolás Cabrera (INC) and Condensed Matter Physics Institute (IFIMAC), Universidad Autónoma de Madrid, Madrid, 28049, Spain.
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27
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Bhatia E, Hussain Z, Reddy VR, Barber ZH, Senapati K. Unconventional domain wall magnetoresistance of patterned Ni/Nb bilayer structures below superconducting transition temperature of Nb. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 33:295803. [PMID: 33975294 DOI: 10.1088/1361-648x/ac0022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2021] [Accepted: 05/11/2021] [Indexed: 06/12/2023]
Abstract
Scattering of spin-up and spin-down electrons while passing through a ferromagnetic domain wall (DW) leads to an additional resistance for transport current, usually observed prominently in constricted magnetic structures. In this report we use the resistance of the DW as a probe to find an indirect signatures of the theoretically predicted spin-singlet supercurrent to spin-triplet supercurrent conversion effect of ferromagnetic DWs. Here we examine the DW induced resistance in Ni stripe in a bilayer Ni/Nb geometry in the normal state and in the superconducting state of Nb. By making a 3μm wide gap in the top Nb layer we routed the transport current through the Ni layer in the normal state and in the superconducting state of Nb. In the normal state of Nb, in-field transport measurements showed a clear domain wall magneto-resistance (DWMR) peak of amplitude ∼5.9 mΩ near the coercive field, where the DW density is expected to be maximum. Interestingly, however, below the superconducting transition temperature of Nb, the DWMR peak of the Ni layer showed a sharp drop in the field range where the number of DWs become maximum. This observation may be a possible signature of magnetic DW induced spin-triplet correlations in the Ni layer due to the direct injection of spin-singlet Cooper pairs from Nb into the magnetic DWs.
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Affiliation(s)
- Ekta Bhatia
- School of Physical Sciences, National Institute of Science Education and Research (NISER), HBNI, Bhubaneswar, Odisha, 752050, India
| | - Zainab Hussain
- UGC-DAE Consortium for Scientific Research, Indore Centre, 452017, India
| | | | - Zoe H Barber
- Department of Materials Science & Metallurgy, University of Cambridge, 27 Charles Babbage Road, CB3 0FS, United Kingdom
| | - Kartik Senapati
- School of Physical Sciences, National Institute of Science Education and Research (NISER), HBNI, Bhubaneswar, Odisha, 752050, India
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28
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Bhatia E, Srivastava A, Devine-Stoneman J, Stelmashenko NA, Barber ZH, Robinson JWA, Senapati K. Nanoscale Domain Wall Engineered Spin-Triplet Josephson Junctions and SQUID. NANO LETTERS 2021; 21:3092-3097. [PMID: 33724857 DOI: 10.1021/acs.nanolett.1c00273] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Spin-singlet Cooper pairs convert to spin-triplet Cooper pairs on passing through a magnetically noncollinear structure at a superconductor(S)/ferromagnet(F) interface. In this context, the generation of triplet supercurrents through intrinsic ferromagnetic domain walls, which are naturally occurring noncollinear magnetic features, was proposed theoretically in the past decade. However, an experimental demonstration has been lacking in the literature, particularly because of the difficulty in accessing a single domain wall, which is typically buried between two domains in a ferromagnetic material. By patterning a ferromagnetic nanoconstriction, we have been able to realize a nanoscale S/F/S planar junction, where a single domain wall (pinned at the nanoconstriction) acts as a Josephson barrier. In this geometry, we are able to show the predicted long-range triplet supercurrent across a ferromagnetic barrier exceeding 70 nm. Using this technique, we have demonstrated a ferromagnetic planar nano-SQUID device consisting of two Nb/Ni/Nb spin-triplet Josephson junctions.
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Affiliation(s)
- Ekta Bhatia
- School of Physical Sciences, National Institute of Science Education and Research (NISER), HBNI, Bhubaneswar, Odisha 752050, India
| | - Anand Srivastava
- Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, United Kingdom
| | - James Devine-Stoneman
- Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, United Kingdom
| | - Nadia A Stelmashenko
- Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, United Kingdom
| | - Zoe H Barber
- Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, United Kingdom
| | - Jason W A Robinson
- Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, United Kingdom
| | - Kartik Senapati
- School of Physical Sciences, National Institute of Science Education and Research (NISER), HBNI, Bhubaneswar, Odisha 752050, India
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29
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Müller M, Liensberger L, Flacke L, Huebl H, Kamra A, Belzig W, Gross R, Weiler M, Althammer M. Temperature-Dependent Spin Transport and Current-Induced Torques in Superconductor-Ferromagnet Heterostructures. PHYSICAL REVIEW LETTERS 2021; 126:087201. [PMID: 33709738 DOI: 10.1103/physrevlett.126.087201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2020] [Revised: 12/01/2020] [Accepted: 01/21/2021] [Indexed: 06/12/2023]
Abstract
We investigate the injection of quasiparticle spin currents into a superconductor via spin pumping from an adjacent ferromagnetic metal layer. To this end, we use NbN-Ni_{80}Fe_{20}(Py) heterostructures with a Pt spin sink layer and excite ferromagnetic resonance in the Permalloy layer by placing the samples onto a coplanar waveguide. A phase sensitive detection of the microwave transmission signal is used to quantitatively extract the inductive coupling strength between the sample and the coplanar waveguide, interpreted in terms of inverse current-induced torques, in our heterostructures as a function of temperature. Below the superconducting transition temperature T_{c}, we observe a suppression of the dampinglike torque generated in the Pt layer by the inverse spin Hall effect, which can be understood by the changes in spin current transport in the superconducting NbN layer. Moreover, below T_{c} we find a large fieldlike current-induced torque.
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Affiliation(s)
- M Müller
- Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany
- Physik-Department, Technische Universität München, 85748 Garching, Germany
| | - L Liensberger
- Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany
- Physik-Department, Technische Universität München, 85748 Garching, Germany
| | - L Flacke
- Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany
- Physik-Department, Technische Universität München, 85748 Garching, Germany
| | - H Huebl
- Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany
- Physik-Department, Technische Universität München, 85748 Garching, Germany
- Munich Center for Quantum Science and Technology (MCQST), Schellingstraße 4, 80799 München, Germany
| | - A Kamra
- Center for Quantum Spintronics, Department of Physics, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway
| | - W Belzig
- Fachbereich Physik, Universität Konstanz, 78457 Konstanz, Germany
| | - R Gross
- Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany
- Physik-Department, Technische Universität München, 85748 Garching, Germany
- Munich Center for Quantum Science and Technology (MCQST), Schellingstraße 4, 80799 München, Germany
| | - M Weiler
- Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany
- Physik-Department, Technische Universität München, 85748 Garching, Germany
| | - M Althammer
- Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany
- Physik-Department, Technische Universität München, 85748 Garching, Germany
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30
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Komori S, Devine-Stoneman JM, Ohnishi K, Yang G, Devizorova Z, Mironov S, Montiel X, Olde Olthof LAB, Cohen LF, Kurebayashi H, Blamire MG, Buzdin AI, Robinson JWA. Spin-orbit coupling suppression and singlet-state blocking of spin-triplet Cooper pairs. SCIENCE ADVANCES 2021; 7:eabe0128. [PMID: 33523885 PMCID: PMC7806214 DOI: 10.1126/sciadv.abe0128] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/25/2020] [Accepted: 11/17/2020] [Indexed: 06/12/2023]
Abstract
An inhomogeneous magnetic exchange field at a superconductor/ferromagnet interface converts spin-singlet Cooper pairs to a spin-polarized triplet state. Although the decay envelope of triplet pairs within ferromagnetic materials is well studied, little is known about their decay in nonmagnetic metals and superconductors and, in particular, in the presence of spin-orbit coupling (SOC). Here, we investigate devices in which singlet and triplet supercurrents propagate into the s-wave superconductor Nb. In the normal state of Nb, triplet supercurrents decay over a distance of 5 nm, which is an order of magnitude smaller than the decay of spin-singlet pairs due to the SOC. In the superconducting state of Nb, triplet supercurrents are not able to couple with the singlet wave function and are thus blocked by the absence of available equilibrium states in the singlet gap. The results offer insight into the dynamics between s-wave singlet and s-wave triplet states.
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Affiliation(s)
- Sachio Komori
- Department of Materials Science & Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, UK.
| | - James M Devine-Stoneman
- Department of Materials Science & Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, UK
| | - Kohei Ohnishi
- Department of Physics, Kyushu University, 744 Motooka, Fukuoka 819-0395, Japan
- Research Center for Quantum Nano-Spin Sciences, 744 Motooka, Fukuoka 819-0395, Japan
| | - Guang Yang
- Department of Materials Science & Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, UK
| | - Zhanna Devizorova
- Moscow Institute of Physics and Technology, Dolgoprudny 141700, Russia
- Kotelnikov Institute of Radio-engineering and Electronics RAS, Moscow 125009, Russia
| | - Sergey Mironov
- Institute for Physics of Microstructures, Russian Academy of Sciences, GSP-105, Nizhny Novgorod 603950, Russia
| | - Xavier Montiel
- Department of Materials Science & Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, UK
| | - Linde A B Olde Olthof
- Department of Materials Science & Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, UK
| | - Lesley F Cohen
- The Blackett Laboratory, Imperial College London SW7 2AZ, UK
| | - Hidekazu Kurebayashi
- London Centre for Nanotechnology and Department of Electronic and Electrical Engineering at University College London, London WC1H 01H, UK
| | - Mark G Blamire
- Department of Materials Science & Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, UK
| | - Alexandre I Buzdin
- University Bordeaux, LOMA UMR-CNRS 5798,, F-33405 Talence Cedex, France
- Sechenov First Moscow State Medical University, Moscow 119991, Russia
| | - Jason W A Robinson
- Department of Materials Science & Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, UK.
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31
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Han W, Maekawa S, Xie XC. Spin current as a probe of quantum materials. NATURE MATERIALS 2020; 19:139-152. [PMID: 31451780 DOI: 10.1038/s41563-019-0456-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2018] [Accepted: 07/15/2019] [Indexed: 06/10/2023]
Abstract
Spin current historically referred to the flow of electrons carrying spin information, in particular since the discovery of giant magnetoresistance in the 1980s. Recently, it has been found that spin current can also be mediated by spin-triplet supercurrent, superconducting quasiparticles, spinons, magnons, spin superfluidity and so on. Here, we review key progress concerning the developing research direction utilizing spin current as a probe of quantum materials. We focus on spin-triplet superconductivity and spin dynamics in the ferromagnet/superconductor heterostructures, quantum spin liquids, magnetic phase transitions, magnon-polarons, magnon-polaritons, magnon Bose-Einstein condensates and spin superfluidity. The unique characteristics of spin current as a probe will be fruitful for future investigation of spin-dependent properties and the identification of new quantum materials.
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Affiliation(s)
- Wei Han
- International Center for Quantum Materials, School of Physics, Peking University, Beijing, China.
- Collaborative Innovation Center of Quantum Matter, Beijing, China.
| | - Sadamichi Maekawa
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Japan
- Kavli Institute for Theoretical Sciences (KITS), University of Chinese Academy of Sciences, Beijing, China
| | - Xin-Cheng Xie
- International Center for Quantum Materials, School of Physics, Peking University, Beijing, China
- Collaborative Innovation Center of Quantum Matter, Beijing, China
- CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing, China
- Beijing Academy of Quantum Information Sciences, Beijing, China
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32
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Anomalous anisotropic behaviour of spin-triplet proximity effect in Au/SrRuO 3/Sr 2RuO 4 junctions. Sci Rep 2019; 9:15827. [PMID: 31676832 PMCID: PMC6825120 DOI: 10.1038/s41598-019-52003-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2019] [Accepted: 10/10/2019] [Indexed: 11/23/2022] Open
Abstract
Spin-polarized supercurrents can be generated with magnetic inhomogeneity at a ferromagnet/spin-singlet-superconductor interface. In such systems, complex magnetic inhomogeneity makes it difficult to functionalise the spin-polarized supercurrents. However, spin-polarized supercurrents in ferromagnet/spin-triplet-superconductor junctions can be controlled by the angle between magnetization and spin of Copper pairs (d-vector), that can effectively be utilized in developing of a field of research known as superconducting spintronics. Recently, we found induction of spin-triplet correlation into a ferromagnet SrRuO3 epitaxially deposited on a spin-triplet superconductor Sr2RuO4, without any electronic spin-flip scattering. Here, we present systematic magnetic field dependence of the proximity effect in Au/SrRuO3/Sr2RuO4 junctions. It is found that induced triplet correlations exhibit strongly anisotropic field response. Such behaviour is attributed to the rotation of the d-vector of Sr2RuO4. This anisotropic behaviour is in contrast with the vortex dynamic. Our results will stimulate study of interaction between ferromagnetism and unconventional superconductivity.
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33
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Chen YC, Yen M, Lai YH, Markou A, Zhang L, Chin YY, Lin HJ, Chen CT, Felser C, Chu YH. Heteroepitaxy of Co-Based Heusler Compound/Muscovite for Flexible Spintronics. ACS APPLIED MATERIALS & INTERFACES 2019; 11:35162-35168. [PMID: 31476857 DOI: 10.1021/acsami.9b12219] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Materials with high spin-polarization play an important role in the development of spintronics. Co-based Heusler compounds are a promising candidate for practical applications because of their high Curie temperature and tunable half-metallicity. However, it is a challenge to integrate Heusler compounds into thin film heterostructures because of the lack of control on crystallinity and chemical disorder, critical factors of novel behaviors. Here, muscovite is introduced as a growth substrate to fabricate epitaxial Co2MnGa films with mechanical flexibility. The feature of heteroepitaxy is evidenced by the results of X-ray diffraction and transmission electron microscopy. Moreover, high chemical ordering with superior properties is delivered according to the observation of large Hall conductivity (680 Ω-1 cm-1) and highly saturated magnetic moment (∼3.93 μB/f.u.), matching well with bulk crystals. Furthermore, the excellence of magnetic and electrical properties is retained under the various mechanical bending conditions. Such a result suggests that the development of Co2MnGa/muscovite heteroepitaxy provides not only a pathway to the thin film heterostructure based on high-quality Heusler compounds but also a new aspect of spintronic applications on flexible substrates.
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Affiliation(s)
- Yi-Cheng Chen
- Max Planck Institute for Chemical Physics of Solids , Dresden 01187 , Germany
| | | | | | - Anastasios Markou
- Max Planck Institute for Chemical Physics of Solids , Dresden 01187 , Germany
| | - Liguo Zhang
- Max Planck Institute for Chemical Physics of Solids , Dresden 01187 , Germany
| | - Yi-Ying Chin
- Department of Physics , National Chung Cheng University , Chiayi 62102 , Taiwan
| | - Hong-Ji Lin
- National Synchrotron Radiation Research Center , Hsinchu 30010 , Taiwan
| | - Chien-Te Chen
- National Synchrotron Radiation Research Center , Hsinchu 30010 , Taiwan
| | - Claudia Felser
- Max Planck Institute for Chemical Physics of Solids , Dresden 01187 , Germany
| | - Ying-Hao Chu
- Institute of Physics , Academia Sinica , Taipei 11529 , Taiwan
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Controlling spin supercurrents via nonequilibrium spin injection. Sci Rep 2019; 9:12731. [PMID: 31519921 PMCID: PMC6744513 DOI: 10.1038/s41598-019-48945-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2019] [Accepted: 07/17/2019] [Indexed: 11/22/2022] Open
Abstract
We propose a mechanism whereby spin supercurrents can be manipulated in superconductor/ferromagnet proximity systems via nonequilibrium spin injection. We find that if a spin supercurrent exists in equilibrium, a nonequilibrium spin accumulation will exert a torque on the spins transported by this current. This interaction causes a new spin supercurrent contribution to manifest out of equilibrium, which is proportional to and polarized perpendicularly to both the injected spins and the equilibrium spin current. This is interesting for several reasons: as a fundamental physical effect; due to possible applications as a way to control spin supercurrents; and timeliness in light of recent experiments on spin injection in proximitized superconductors.
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Ivanov YP, Soltan S, Albrecht J, Goering E, Schütz G, Zhang Z, Chuvilin A. The Route to Supercurrent Transparent Ferromagnetic Barriers in Superconducting Matrix. ACS NANO 2019; 13:5655-5661. [PMID: 30977633 PMCID: PMC8830211 DOI: 10.1021/acsnano.9b00888] [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: 01/31/2019] [Accepted: 04/12/2019] [Indexed: 06/09/2023]
Abstract
A ferromagnetic barrier thinner than the coherence length in high-temperature superconductors is realized in the multilayers of YBa2Cu3O7-δ and La0.67Ca0.33MnO3. We used epitaxial growth of YBCO on ⟨110⟩ SrTiO3 substrates by pulsed laser deposition to prepare thin superconducting films with copper oxide planes oriented at an angle to the substrate surface. Subsequent deposition of LCMO and finally a second YBCO layer produces a superconductor/ferromagnet/superconductor trilayer containing an ultrathin ferromagnetic barrier with sophisticated geometry at which the long axis of coherence length ovoid of YBCO is pointing across the LCMO ferromagnetic layer. A detailed characterization of this structure is achieved using high-resolution electron microscopy.
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Affiliation(s)
- Yurii P. Ivanov
- Department
of Materials Science and Metallurgy, University
of Cambridge, Cambridge CB3 0FS, United Kingdom
- Erich
Schmid Institute of Materials Science, Austrian
Academy of Sciences, Jahnstraße 12, A-8700 Leoben, Austria
- School
of Natural Sciences, Far Eastern Federal
University, 690950 Vladivostok, Russia
| | - Soltan Soltan
- Department
of Physics, Faculty of Science, Helwan University, 11792 Cairo, Egypt
- Max-Planck-Institute
for Intelligent Systems, Heisenbergstr. 3, D-70569 Stuttgart, Germany
| | - Joachim Albrecht
- Research
Institute for Innovative Surfaces FINO, Beethovenstr. 1, D-73430 Aalen, Germany
| | - Eberhard Goering
- Max-Planck-Institute
for Intelligent Systems, Heisenbergstr. 3, D-70569 Stuttgart, Germany
| | - Gisela Schütz
- Max-Planck-Institute
for Intelligent Systems, Heisenbergstr. 3, D-70569 Stuttgart, Germany
| | - Zaoli Zhang
- Erich
Schmid Institute of Materials Science, Austrian
Academy of Sciences, Jahnstraße 12, A-8700 Leoben, Austria
| | - Andrey Chuvilin
- CIC
nanoGUNE Consolider, Av. de Tolosa 76, 20018 San Sebastian, Spain
- Basque
Foundation for Science, IKERBASQUE, Maria Diaz de Haro 3, 48013 Bilbao, Spain
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Nakamura T, Anh LD, Hashimoto Y, Ohya S, Tanaka M, Katsumoto S. Evidence for Spin-Triplet Electron Pairing in the Proximity-Induced Superconducting State of an Fe-Doped InAs Semiconductor. PHYSICAL REVIEW LETTERS 2019; 122:107001. [PMID: 30932666 DOI: 10.1103/physrevlett.122.107001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2018] [Indexed: 06/09/2023]
Abstract
We provide evidence for spin-triplet electron pairing in proximity-induced superconductivity in a ferromagnetic semiconductor (In,Fe)As. As discovered in half-metallic materials, an extraordinarily long proximity range is observed. More surprising is a very strong concentration of supercurrent to the edges of the superconducting region, which is deduced from the extremely persistent oscillation of the critical current vs magnetic field. The maxima of the critical current appear not at the zero magnetic flux but at around the maximum magnetic disorder, reflecting the connectivity between the spin-triplet and singlet pairings. These spin-triplet natures in proximity superconductivity also reveal ferromagnetic properties of (In,Fe)As.
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Affiliation(s)
- Taketomo Nakamura
- Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan
| | - Le Duc Anh
- Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656, Japan
- Institute of Engineering Innovation, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Yoshiaki Hashimoto
- Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan
| | - Shinobu Ohya
- Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656, Japan
- Institute of Engineering Innovation, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
- Center for Spintronics Research Network (CSRN), The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Masaaki Tanaka
- Institute of Engineering Innovation, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
- Center for Spintronics Research Network (CSRN), The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Shingo Katsumoto
- Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan
- Center for Spintronics Research Network (CSRN), The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
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Caruso R, Massarotti D, Campagnano G, Pal A, Ahmad HG, Lucignano P, Eschrig M, Blamire MG, Tafuri F. Tuning of Magnetic Activity in Spin-Filter Josephson Junctions Towards Spin-Triplet Transport. PHYSICAL REVIEW LETTERS 2019; 122:047002. [PMID: 30768353 DOI: 10.1103/physrevlett.122.047002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2018] [Indexed: 06/09/2023]
Abstract
The study of superconductor-ferromagnet interfaces has generated great interest in the last decades, leading to the observation of spin-aligned triplet supercurrents and 0-π transitions in Josephson junctions where two superconductors are separated by an itinerant ferromagnet. Recently, spin-filter Josephson junctions with ferromagnetic barriers have shown unique transport properties, when compared to standard metallic ferromagnetic junctions, due to the intrinsically nondissipative nature of the tunneling process. Here we present the first extensive characterization of spin polarized Josephson junctions down to 0.3 K, and the first evidence of an incomplete 0-π transition in highly spin polarized tunnel ferromagnetic junctions. Experimental data are consistent with a progressive enhancement of the magnetic activity with the increase of the barrier thickness, as neatly captured by the simplest theoretical approach including a nonuniform exchange field. For very long junctions, unconventional magnetic activity of the barrier points to the presence of spin-triplet correlations.
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Affiliation(s)
- R Caruso
- Dipartimento di Fisica E. Pancini, Università degli Studi di Napoli Federico II, Monte S. Angelo, via Cinthia, I-80126 Napoli, Italy
- CNR-SPIN, c/o complesso di Monte S. Angelo, via Cinthia, I-80126 Napoli, Italy
- SeeQC-eu, via dei Due Macelli 66, I-00187 Roma, Italy
| | - D Massarotti
- CNR-SPIN, c/o complesso di Monte S. Angelo, via Cinthia, I-80126 Napoli, Italy
- Dipartimento di Ingegneria Elettrica e delle Tecnologie dell'Informazione, Università degli Studi di Napoli Federico II, via Claudio, I-80125 Napoli, Italy
| | - G Campagnano
- Dipartimento di Fisica E. Pancini, Università degli Studi di Napoli Federico II, Monte S. Angelo, via Cinthia, I-80126 Napoli, Italy
- CNR-SPIN, c/o complesso di Monte S. Angelo, via Cinthia, I-80126 Napoli, Italy
| | - A Pal
- Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, United Kingdom
| | - H G Ahmad
- Dipartimento di Fisica E. Pancini, Università degli Studi di Napoli Federico II, Monte S. Angelo, via Cinthia, I-80126 Napoli, Italy
- CNR-SPIN, c/o complesso di Monte S. Angelo, via Cinthia, I-80126 Napoli, Italy
| | - P Lucignano
- Dipartimento di Fisica E. Pancini, Università degli Studi di Napoli Federico II, Monte S. Angelo, via Cinthia, I-80126 Napoli, Italy
- CNR-SPIN, c/o complesso di Monte S. Angelo, via Cinthia, I-80126 Napoli, Italy
| | - M Eschrig
- Department of Physics, Royal Holloway, University of London, Egham, Surrey TW20 0EX, United Kingdom
| | - M G Blamire
- Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, United Kingdom
| | - F Tafuri
- Dipartimento di Fisica E. Pancini, Università degli Studi di Napoli Federico II, Monte S. Angelo, via Cinthia, I-80126 Napoli, Italy
- CNR-SPIN, c/o complesso di Monte S. Angelo, via Cinthia, I-80126 Napoli, Italy
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Diesch S, Machon P, Wolz M, Sürgers C, Beckmann D, Belzig W, Scheer E. Creation of equal-spin triplet superconductivity at the Al/EuS interface. Nat Commun 2018; 9:5248. [PMID: 30531894 PMCID: PMC6286363 DOI: 10.1038/s41467-018-07597-w] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2018] [Accepted: 11/12/2018] [Indexed: 11/09/2022] Open
Abstract
In conventional superconductors, electrons of opposite spins are bound into Cooper pairs. However, when the superconductor is in contact with a non-uniformly ordered ferromagnet, an exotic type of superconductivity can appear at the interface, with electrons bound into three possible spin-triplet states. Triplet pairs with equal spin play a vital role in low-dissipation spintronics. Despite the observation of supercurrents through ferromagnets, spectroscopic evidence for the existence of equal-spin triplet pairs is still missing. Here we show a theoretical model that reveals a characteristic gap structure in the quasiparticle density of states which provides a unique signature for the presence of equal-spin triplet pairs. By scanning tunnelling spectroscopy we measure the local density of states to reveal the spin configuration of triplet pairs. We demonstrate that the Al/EuS interface causes strong and tunable spin-mixing by virtue of its spin-dependent transmission.
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Affiliation(s)
- S Diesch
- Department of Physics, University of Konstanz, Universitätsstraße 10, D-78457, Konstanz, Germany
| | - P Machon
- Department of Physics, University of Konstanz, Universitätsstraße 10, D-78457, Konstanz, Germany
| | - M Wolz
- Department of Physics, University of Konstanz, Universitätsstraße 10, D-78457, Konstanz, Germany
| | - C Sürgers
- Physikalisches Institut, Karlsruhe Institute of Technology (KIT), Wolfgang Gaede Straße 1, D-76131, Karlsruhe, Germany
| | - D Beckmann
- Institute of Nanotechnology, Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, D-76344, Eggenstein-Leopoldshafen, Germany
| | - W Belzig
- Department of Physics, University of Konstanz, Universitätsstraße 10, D-78457, Konstanz, Germany.
| | - E Scheer
- Department of Physics, University of Konstanz, Universitätsstraße 10, D-78457, Konstanz, Germany.
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40
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Cao X, Li XF, Hu W. Tunable Electronic and Magnetic Properties of Graphene-Embedded Transition Metal-N 4 Complexes: Insight From First-Principles Calculations. Chem Asian J 2018; 13:3239-3245. [PMID: 30151862 DOI: 10.1002/asia.201801052] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2018] [Indexed: 11/09/2022]
Abstract
Motivated by the development of transition-metal-nitrogen-carbon (TM-N-C) materials for catalysts and molecular electronics, we investigated the electronic and magnetic properties of TMN4 -graphene materials with different central atoms (TM=Ti, V, Cr, Mn, Fe, Co, Ni and Cu) and different concentrations. The first-principles results show that a widely tunable magnetic moment in the range from 0 to 4 μB can be obtained in this kind of material by varying the central TM atom, and a regular transition of the electronic property from metallic to half-metallic and to semiconducting characteristics is observed in MnN4 -graphene upon changing the concentration. We find that the peculiar relationship between the electronic characteristics of graphene and its lattice parameters plays a decisive role in determining the electronic and magnetic properties. Our findings are useful for the design of TM-N-C materials for catalysis, spintronics, and molectronics.
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Affiliation(s)
- Xinrui Cao
- Department of Physics and Collaborative Innovation Center for Optoelectronic Semiconductors and Efficient Devices, Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, Xiamen University, Xiamen, Fujian, 361005, China
| | - Xiao-Fei Li
- School of Optoelectronic Information, University of Electronic Science and Technology of China, Chengdu, Sichuan, 610054, China
| | - Wei Hu
- School of Chemistry and Materials Science, University of Science and Technology of China and iChEM, Hefei, 230026, China
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41
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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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42
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Holmqvist C, Belzig W, Fogelström M. Non-equilibrium charge and spin transport in superconducting-ferromagnetic-superconducting point contacts. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2018; 376:20150229. [PMID: 29941627 PMCID: PMC6030142 DOI: 10.1098/rsta.2015.0229] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 04/16/2016] [Indexed: 06/08/2023]
Abstract
The conventional Josephson effect may be modified by introducing spin-active scattering in the interface layer of the junction. Here, we discuss a Josephson junction consisting of two s-wave superconducting leads coupled over a classical spin that precesses with the Larmor frequency due to an external magnetic field. This magnetically active interface results in a time-dependent boundary condition with different tunnelling amplitudes for spin-up and -down quasi-particles and where the precession produces spin-flip scattering processes. As a result, the Andreev states develop sidebands and a non-equilibrium population that depend on the details of the spin precession. The Andreev states carry a steady-state Josephson charge current and a time-dependent spin current, whose current-phase relations could be used to characterize the precessing spin. The spin current is supported by spin-triplet correlations induced by the spin precession and creates a feedback effect on the classical spin in the form of a torque that shifts the precession frequency. By applying a bias voltage, the Josephson frequency adds another complexity to the situation and may create resonances together with the Larmor frequency. These Shapiro resonances manifest as torques and, under suitable conditions, are able to reverse the direction of the classical spin in sub-nanosecond time. Another characteristic feature is the subharmonic gap structure in the DC charge current displaying an even-odd effect attributable to precession-assisted multiple Andreev reflections.This article is part of the theme issue 'Andreev bound states'.
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Affiliation(s)
- C Holmqvist
- Department of Physics, Norwegian University of Science and Technology, 7491 Trondheim, Norway
| | - W Belzig
- Fachbereich Physik, Universität Konstanz, 78457 Konstanz, Germany
| | - M Fogelström
- Department of Microtechnology and Nanoscience - MC2, Chalmers University of Technology, 412 96 Göteborg, Sweden
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43
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Millo O, Koren G. What can Andreev bound states tell us about superconductors? PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2018; 376:rsta.2014.0143. [PMID: 29941620 PMCID: PMC6030152 DOI: 10.1098/rsta.2014.0143] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 02/07/2016] [Indexed: 06/08/2023]
Abstract
Zero-energy Andreev bound states, which manifest themselves in the tunnelling spectra as zero-bias conductance peaks (ZBCPs), are abundant at interfaces between superconductors and other materials and on the nodal surface of high-temperature superconductors. In this review, we focus on the information such excitations can provide on the properties of superconductor systems. First, a general introduction to the physics of Andreev bound states in superconductor/normal metal interfaces is given with a particular emphasis on why they appear at zero energy in d-wave superconductors. Then, specific spectroscopic tunnelling studies of thin films, bilayers and junctions are described, focusing on the corresponding ZBCP features. Scanning tunnelling spectroscopy (STS) studies show that the ZBCPs on the c-axis YBa2Cu3O7-δ (YBCO) films are correlated with the surface morphology and appear only in proximity to (110) facets. STS on c-axis La1.88Sr0.12CuO4 (LSCO) films exhibiting the 1/8 anomaly shows spatially modulated peaks near zero bias associated with the anti-phase ordering of the d-wave order parameter predicted at this doping level. ZBCPs were also found in micrometre-size edge junctions of YBCO/SrRuO3/YBCO, where SrRuO3 is ferromagnetic. Here, the results are consistent with a crossed Andreev reflection effect (CARE) at the narrow domain walls of the SrRuO3 ZBCPs measured in STS studies of manganite/cuprate bilayers could not be attributed to CARE because the manganite's domain wall is much larger than the coherence length in YBCO, and instead are attributed to proximity-induced triplet-pairing superconductivity with non-conventional symmetry. And finally, ZBCPs found in junctions of non-intentionally doped topological insulator films of Bi2Se3 and the s-wave superconductor NbN are attributed to proximity-induced px + ipy triplet order parameter in the topological material.This article is part of the theme issue 'Andreev bound states'.
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Affiliation(s)
- Oded Millo
- Racah Institute of Physics, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - Gad Koren
- Department of Physics, Technion-Israel Institute of Technology, Haifa 32000, Israel
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44
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Birge NO. Spin-triplet supercurrents in Josephson junctions containing strong ferromagnetic materials. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2018; 376:20150150. [PMID: 29941625 PMCID: PMC6030151 DOI: 10.1098/rsta.2015.0150] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 06/28/2015] [Indexed: 06/08/2023]
Abstract
The proximity effect between a superconducting material and a non-superconducting normal metal can extend over distances of the order of micrometres at sufficiently low temperatures. If the normal metal is replaced by a ferromagnetic material, the spatial extent of the proximity effect drops precipitously due to the exchange splitting between the majority and minority spin bands in the ferromagnet. In 2001, several theorists predicted that spin-triplet pair correlations could be induced in proximity systems involving multiple ferromagnetic materials (or multiple domains in one material) with non-collinear magnetizations. Such spin-triplet pair correlations should extend deep into the ferromagnet, producing a long-range proximity effect. In this paper, we review our experimental work in this area, which has focused primarily on Josephson junctions containing strong ferromagnetic materials. We show that Josephson junctions containing particular combinations of strong ferromagnetic materials can carry spin-triplet supercurrent over distances of at least several tens of nanometres, whereas spin-singlet supercurrent in similar samples decays over a length scale of about 1 nm. We also mention important work by other groups; however, this article is not intended to be a review of the whole field.This article is part of the theme issue 'Andreev bound states'.
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Affiliation(s)
- Norman O Birge
- Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824, USA
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45
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Huang S, Wu X, Niu J, Qin S. Structural, magnetic and electronic properties of CrO 2 at multimegabar pressures. RSC Adv 2018; 8:24561-24570. [PMID: 35539182 PMCID: PMC9082015 DOI: 10.1039/c8ra04537b] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2018] [Accepted: 06/29/2018] [Indexed: 11/26/2022] Open
Abstract
As the only half-metallic ferromagnetic material in 3d transition metal dioxides, CrO2 has attracted great scientific interest from materials science to physical chemistry. Here, an investigation into the structural, magnetic and electronic properties of CrO2 under high pressure has been conducted by first-principles calculations based on density functional theory. Static calculations have predicted that CrO2 undergoes structural transitions with the sequence of rutile-type → CaCl2-type → pyrite-type → Pnma → (Fe2P-type→) I4/mmm at high pressures. In addition, a transition from the ferromagnetic state to the non-magnetic state with the magnetic collapse of Cr is observed in CrO2 at the pyrite-Pnma transition. This transition also delocalizes the 3d electrons of Cr and leads to a metallic character of CrO2. The equation of state, elasticity and band gap for each energetically favorable phase of CrO2 are determined. Our results not only bridge the gap about the high-pressure behavior of CrO2 in previous studies but also extend our understanding of its properties up to multimegabar conditions. According to previous data and present results, we further discuss and summarize the high-pressure behavior of various AO2 compounds. This can contribute to investigating properties of other AO2 compounds or exploring novel materials at high pressures.
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Affiliation(s)
- Shengxuan Huang
- Key Laboratory of Orogenic Belts and Crustal Evolution, MOE, School of Earth and Space Sciences, Peking University Beijing 100871 P. R. China
| | - Xiang Wu
- State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences Wuhan 430074 P. R. China
| | - Jingjing Niu
- Key Laboratory of Orogenic Belts and Crustal Evolution, MOE, School of Earth and Space Sciences, Peking University Beijing 100871 P. R. China
| | - Shan Qin
- Key Laboratory of Orogenic Belts and Crustal Evolution, MOE, School of Earth and Space Sciences, Peking University Beijing 100871 P. R. China
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Glick JA, Aguilar V, Gougam AB, Niedzielski BM, Gingrich EC, Loloee R, Pratt WP, Birge NO. Phase control in a spin-triplet SQUID. SCIENCE ADVANCES 2018; 4:eaat9457. [PMID: 30062127 PMCID: PMC6063539 DOI: 10.1126/sciadv.aat9457] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2018] [Accepted: 06/18/2018] [Indexed: 06/01/2023]
Abstract
It is now well established that a Josephson junction made from conventional spin-singlet superconductors containing ferromagnetic layers can carry spin-triplet supercurrent under certain conditions. The first experimental signature of that fact is the propagation of such supercurrent over long distances through strong ferromagnetic materials. Surprisingly, one of the most salient predictions of the theory has yet to be verified experimentally-namely, that a Josephson junction containing three magnetic layers with coplanar magnetizations should exhibit a ground-state phase shift of either zero or π depending on the relative orientations of those magnetizations. We demonstrate this property using Josephson junctions containing three different types of magnetic layers, chosen so that the magnetization of one layer can be switched by 180° without disturbing the other two. Phase-sensitive detection is accomplished using a superconducting quantum interference device, or SQUID. Such a phase-controllable junction could be used as the memory element in a fully superconducting computer.
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Affiliation(s)
| | | | - Adel B. Gougam
- Michigan State University, East Lansing, MI 48824, USA
- Khalifa University of Science and Technology/Masdar Institute, Abu Dhabi, UAE
| | | | | | - Reza Loloee
- Michigan State University, East Lansing, MI 48824, USA
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Tao Z, Chen FJ, Zhou LY, Li B, Tao YC, Wang J. Superconductivity switch from spin-singlet to -triplet pairing in a topological superconducting junction. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:225302. [PMID: 29651996 DOI: 10.1088/1361-648x/aabdfd] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The interedge coupling is the cardinal characteristic of the narrow quantum spin Hall (QSH) insulator, and thus could bring about exotic transport phenomena. Herein, we present a theoretical investigation of the spin-resolved Andreev reflection (AR) in a QSH insulator strip touching on two neighbouring ferromagnetic insulators and one s-wave superconductor. It is demonstrated that, due to the interplay of the interedge coupling and ferromagnetic configuration, there could be not only usual local ARs leading to the spin-singlet pairing with the incident electron and Andreev-reflected hole from different spin subbands, but also novel local ARs giving rise to the spin-triplet pairing from the same spin subband. However, only the latter exists in the absence of the interedge coupling, and therefore the two pairings in turn testify the helical spin texture of the edge states. By proper tuning of the band structures of the ferromagnetic layers, under the resonance bias voltage, the usual and novel local ARs of [Formula: see text] can be all exhibited, resulting in fully spin-polarized pure spin-singlet superconductivity and pure spin-triplet superconductivity, respectively, which suggests a superconductivity switch from spin-singlet to -triplet pairing by electrical control. The results can be experimentally confirmed by the tunneling conductance and the noise power.
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Affiliation(s)
- Ze Tao
- College of Telecommunications & Information Engineering, Nanjing University of Posts and Telecommunications, Nanjing 210023, People's Republic of China
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Margaris I, Paltoglou V, Flytzanis N. Current phase relation from graphs and diagrams and application to thick ferromagnetic Josephson junctions. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:195303. [PMID: 29664012 DOI: 10.1088/1361-648x/aaba04] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
In this work we present a method of representing terms in the current-phase-relation of a ballistic Josephson junction by combinations of diagrams, used in previous work to represent an equivalent of the matching condition determinant of the junction. This is accomplished by the expansion of the logarithm of this determinant in Taylor series and keeping track of surviving terms, i.e. terms that do not annihilate each other. The types of the surviving terms are represented by connected graphs, whose points represent diagrammatic terms of the determinant expansion. Then the theory is applied to obtain approximations of the current-phase relation of relatively thick ballistic ferromagnetic Josephson junctions with non-collinear magnetizations. This demonstrates the versatility of the method in developing approximations schemes and providing physical insight into the nature of contributions to the supercurrent from the available particle excitations in the junction. We also discuss the strong second harmonic contribution to the supercurrent in junctions with three mutually orthogonal magnetization vectors and a weak intermediate ferromagnet.
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Affiliation(s)
- I Margaris
- Department of Electrical and Computer Engineering, University of Thessaly, 37 Glavani 28th October Str, 38221 Volos, Magnesia, Greece
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Matsuo S, Ueda K, Baba S, Kamata H, Tateno M, Shabani J, Palmstrøm CJ, Tarucha S. Equal-Spin Andreev Reflection on Junctions of Spin-Resolved Quantum Hall Bulk State and Spin-Singlet Superconductor. Sci Rep 2018; 8:3454. [PMID: 29472574 PMCID: PMC5823919 DOI: 10.1038/s41598-018-21707-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2017] [Accepted: 02/09/2018] [Indexed: 12/02/2022] Open
Abstract
The recent development of superconducting spintronics has revealed the spin-triplet superconducting proximity effect from a spin-singlet superconductor into a spin-polarized normal metal. In addition recently superconducting junctions using semiconductors are in demand for highly controlled experiments to engineer topological superconductivity. Here we report experimental observation of Andreev reflection in junctions of spin-resolved quantum Hall (QH) states in an InAs quantum well and the spin-singlet superconductor NbTi. The measured conductance indicates a sub-gap feature and two peaks on the outer side of the sub-gap feature in the QH plateau-transition regime increases. The observed structures can be explained by considering transport with Andreev reflection from two channels, one originating from equal-spin Andreev reflection intermediated by spin-flip processes and second arising from normal Andreev reflection. This result indicates the possibility to induce the superconducting proximity gap in the the QH bulk state, and the possibility for the development of superconducting spintronics in semiconductor devices.
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Affiliation(s)
- Sadashige Matsuo
- Department of Applied Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan.
| | - Kento Ueda
- Department of Applied Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Shoji Baba
- Department of Applied Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Hiroshi Kamata
- Department of Applied Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
- Center for Emergent Matter Science, RIKEN, 2-1, Hirosawa, Wako-shi, Saitama, 351-0198, Japan
| | - Mizuki Tateno
- Department of Applied Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Javad Shabani
- California NanoSystems Institute, University of California, Santa Barbara, California, 93106, USA
- Center for Quantum Phenomena, Physics Department, New York University, NY, 10003, USA
| | - Christopher J Palmstrøm
- California NanoSystems Institute, University of California, Santa Barbara, California, 93106, USA
- Electrical and Computer Engineering, University of California, Santa Barbara, California, 93106, USA
- Materials Department, University of California, Santa Barbara, California, 93106, USA
| | - Seigo Tarucha
- Department of Applied Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan.
- Center for Emergent Matter Science, RIKEN, 2-1, Hirosawa, Wako-shi, Saitama, 351-0198, Japan.
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Ouassou JA, Pal A, Blamire M, Eschrig M, Linder J. Triplet Cooper pairs induced in diffusive s-wave superconductors interfaced with strongly spin-polarized magnetic insulators or half-metallic ferromagnets. Sci Rep 2017; 7:1932. [PMID: 28512309 PMCID: PMC5434070 DOI: 10.1038/s41598-017-01330-1] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2016] [Accepted: 03/28/2017] [Indexed: 11/23/2022] Open
Abstract
Interfacing superconductors with strongly spin-polarized magnetic materials opens the possibility to discover new spintronic devices in which spin-triplet Cooper pairs play a key role. Motivated by the recent derivation of spin-polarized quasiclassical boundary conditions capable of describing such a scenario in the diffusive limit, we consider the emergent physics in hybrid structures comprised of a conventional s-wave superconductor (e.g. Nb, Al) and either strongly spin-polarized ferromagnetic insulators (e.g. EuO, GdN) or halfmetallic ferromagnets (e.g. CrO2, LCMO). In contrast to most previous works, we focus on how the superconductor itself is influenced by the proximity effect, and how the generated triplet Cooper pairs manifest themselves in the self-consistently computed density of states (DOS) and the superconducting critical temperature Tc. We provide a comprehensive treatment of how the superconductor and its properties are affected by the triplet pairs, demonstrating that our theory can reproduce the recent observation of an unusually large zero-energy peak in a superconductor interfaced with a half-metal, which even exceeds the normal-state DOS. We also discuss the recent observation of a large superconducting spin-valve effect with a Tc change ~1 K in superconductor/half-metal structures, in which case our results indicate that the experiment cannot be explained fully by a long-ranged triplet proximity effect.
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Affiliation(s)
- Jabir Ali Ouassou
- Department of Physics, NTNU, Norwegian University of Science and Technology, N-7491, Trondheim, Norway.
| | - Avradeep Pal
- Department of Materials Science, University of Cambridge, Cambridge, CB3 0FS, United Kingdom
| | - Mark Blamire
- Department of Materials Science, University of Cambridge, Cambridge, CB3 0FS, United Kingdom
| | - Matthias Eschrig
- Department of Physics, Royal Holloway, University of London, Surrey, TW20 0EX, United Kingdom
| | - Jacob Linder
- Department of Physics, NTNU, Norwegian University of Science and Technology, N-7491, Trondheim, Norway
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