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Liu T, Adhikari Y, Wang H, Jiang Y, Hua Z, Liu H, Schlottmann P, Gao H, Weiss PS, Yan B, Zhao J, Xiong P. Chirality-Induced Magnet-Free Spin Generation in a Semiconductor. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2024; 36:e2406347. [PMID: 38926947 DOI: 10.1002/adma.202406347] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/03/2024] [Revised: 06/09/2024] [Indexed: 06/28/2024]
Abstract
Electrical generation and transduction of polarized electron spins in semiconductors (SCs) are of central interest in spintronics and quantum information science. While spin generation in SCs is frequently realized via electrical injection from a ferromagnet (FM), there are significant advantages in nonmagnetic pathways of creating spin polarization. One such pathway exploits the interplay of electron spin with chirality in electronic structures or real space. Here, utilizing chirality-induced spin selectivity (CISS), the efficient creation of spin accumulation in n-doped GaAs via electric current injection from a normal metal (Au) electrode through a self-assembled monolayer (SAM) of chiral molecules (α-helix l-polyalanine, AHPA-L), is demonstrated. The resulting spin polarization is detected as a Hanle effect in the n-GaAs, which is found to obey a distinct universal scaling with temperature and bias current consistent with chirality-induced spin accumulation. The experiment constitutes a definitive observation of CISS in a fully nonmagnetic device structure and demonstration of its ability to generate spin accumulation in a conventional SC. The results thus place key constraints on the physical mechanism of CISS and present a new scheme for magnet-free SC spintronics.
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Affiliation(s)
- Tianhan Liu
- Department of Physics, Florida State University, Tallahassee, FL, 32306, USA
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA, 90095, USA
| | - Yuwaraj Adhikari
- Department of Physics, Florida State University, Tallahassee, FL, 32306, USA
| | - Hailong Wang
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing, 100083, China
| | - Yiyang Jiang
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, 7610001, Israel
| | - Zhenqi Hua
- Department of Physics, Florida State University, Tallahassee, FL, 32306, USA
| | - Haoyang Liu
- Department of Physics, Florida State University, Tallahassee, FL, 32306, USA
| | - Pedro Schlottmann
- Department of Physics, Florida State University, Tallahassee, FL, 32306, USA
| | - Hanwei Gao
- Department of Physics, Florida State University, Tallahassee, FL, 32306, USA
| | - Paul S Weiss
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA, 90095, USA
- California NanoSystems Institute and Departments of Bioengineering and Materials Science and Engineering, University of California, Los Angeles, Los Angeles, CA, 90095, USA
| | - Binghai Yan
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, 7610001, Israel
| | - Jianhua Zhao
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing, 100083, China
| | - Peng Xiong
- Department of Physics, Florida State University, Tallahassee, FL, 32306, USA
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2
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Ponet L, Di Lucente E, Marzari N. The energy landscape of magnetic materials. NPJ COMPUTATIONAL MATERIALS 2024; 10:151. [PMID: 39026599 PMCID: PMC11251989 DOI: 10.1038/s41524-024-01310-w] [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: 09/15/2023] [Accepted: 05/25/2024] [Indexed: 07/20/2024]
Abstract
Magnetic materials can display many solutions to the electronic-structure problem, corresponding to different local or global minima of the energy functional. In Hartree-Fock or density-functional theory different single-determinant solutions lead to different magnetizations, ionic oxidation states, hybridizations, and inter-site magnetic couplings. The vast majority of these states can be fingerprinted through their projection on the atomic orbitals of the magnetic ions. We have devised an approach that provides an effective control over these occupation matrices, allowing us to systematically explore the landscape of the potential energy surface. We showcase the emergence of a complex zoology of self-consistent states; even more so when semi-local density-functional theory is augmented - and typically made more accurate - by Hubbard corrections. Such extensive explorations allow to robustly identify the ground state of magnetic systems, and to assess the accuracy (or not) of current functionals and approximations.
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Affiliation(s)
- Louis Ponet
- Theory and Simulation of Materials (THEOS) and National Centre for Computational Design and Discovery of Novel Materials (MARVEL), École Polytechnique Fédérale de Lausanne, Lausanne, 1015 Switzerland
- Laboratory for Materials Simulations (LMS), Paul Scherrer Insititute, Villigen, 5232 Switzerland
| | - Enrico Di Lucente
- Theory and Simulation of Materials (THEOS) and National Centre for Computational Design and Discovery of Novel Materials (MARVEL), École Polytechnique Fédérale de Lausanne, Lausanne, 1015 Switzerland
| | - Nicola Marzari
- Theory and Simulation of Materials (THEOS) and National Centre for Computational Design and Discovery of Novel Materials (MARVEL), École Polytechnique Fédérale de Lausanne, Lausanne, 1015 Switzerland
- Laboratory for Materials Simulations (LMS), Paul Scherrer Insititute, Villigen, 5232 Switzerland
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3
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Sohn J, Lee JM, Lee HW. Dyakonov-Perel-like Orbital and Spin Relaxations in Centrosymmetric Systems. PHYSICAL REVIEW LETTERS 2024; 132:246301. [PMID: 38949365 DOI: 10.1103/physrevlett.132.246301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2024] [Accepted: 05/15/2024] [Indexed: 07/02/2024]
Abstract
The Dyakonov-Perel (DP) mechanism of spin relaxation has long been considered irrelevant in centrosymmetric systems since it was developed originally for noncentrosymmetric ones. We investigate whether this conventional understanding extends to the realm of orbital relaxation, which has recently attracted significant attention. Surprisingly, we find that orbital relaxation in centrosymmetric systems exhibits the DP-like behavior in the weak scattering regime. Moreover, the DP-like orbital relaxation can make the spin relaxation in centrosymmetric systems DP-like through the spin-orbit coupling. We also find that the DP-like orbital and spin relaxations are anisotropic even in materials with high crystal symmetry (such as face-centered cubic structure) and may depend on the orbital and spin nature of electron wave functions.
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Sharma V, Negusse E, Kumar R, Budhani RC. Ferromagnetic resonance measurement with frequency modulation down to 2 K. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2024; 95:063902. [PMID: 38836719 DOI: 10.1063/5.0190105] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/2023] [Accepted: 05/20/2024] [Indexed: 06/06/2024]
Abstract
Ferromagnetic resonance (FMR) spectroscopy is a powerful technique to study the precessional dynamics of magnetization in thin film heterostructures. It provides valuable information about the mechanisms of exchange bias, spin angular momentum transfer across interfaces, and excitation of magnons. A key desirable feature of FMR spectrometers is the capability to study magnetization dynamics over a wide phase space of temperature (T), frequency (f), and magnetic field (B). The design, fabrication, and testing of such a spectrometer, which uses frequency modulation techniques for improved detection of microwave absorption, reduces heat load in the cryostat and allows simultaneous measurements of inverse spin Hall effect (ISHE) induced dc voltages, is described in this paper. The apparatus is based on a 2-port transmitted microwave signal measurement using a grounded co-planar waveguide. The input radio frequency (RF) signal, frequency modulated at a tunable f-band, excites spin precession in the sample, and the attenuated RF signal is measured phase sensitively. The sample stage, inserted in the bore of a superconducting solenoid, allows magnetic field and temperature variability of 0 to ±5 T and 2-310 K, respectively. We demonstrate the working of this Cryo-FMR and ISHE spectrometer on thin films of Ni80Fe20 and Fe60Co20B20 over a wide T, B, and f phase space.
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Affiliation(s)
- Vinay Sharma
- Department of Physics, Morgan State University, Baltimore, Maryland 21251, USA
| | - Ezana Negusse
- Department of Physics, Morgan State University, Baltimore, Maryland 21251, USA
| | - Ravinder Kumar
- Department of Physics, Morgan State University, Baltimore, Maryland 21251, USA
| | - Ramesh C Budhani
- Department of Physics, Morgan State University, Baltimore, Maryland 21251, USA
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5
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Sverdlov V, Choi SB. Editorial for the Special Issue on Magnetic and Spin Devices, Volume II. MICROMACHINES 2023; 14:2131. [PMID: 38004988 PMCID: PMC10672736 DOI: 10.3390/mi14112131] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2023] [Accepted: 11/19/2023] [Indexed: 11/26/2023]
Abstract
Although the miniaturization of metal-oxide-semiconductor field effect transistors (MOSFETs)-the main driver behind an outstanding increase in the speed, performance, density, and complexity of modern integrated circuits-is continuing, numerous outstanding technological challenges in complimentary metal-oxide-semiconductor (CMOS) device miniaturization are slowly bringing the downscaling to saturation [...].
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Affiliation(s)
- Viktor Sverdlov
- Christian Doppler Laboratory for Nonvolatile Magnetoresistive Memory and Logic, Institute for Microelectronics, TU Wien, 1040 Vienna, Austria
| | - Seung-Bok Choi
- Department of Mechanical Engineering, The State University of New York at Korea (SUNY Korea), 119 Songdo Moonhwa-Ro, Yeonsu-Gu, Incheon 21985, Republic of Korea
- Department of Mechanical Engineering, Industrial University of Ho Chi Minh City, Ho Chi Minh City 7000, Vietnam
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6
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Jiang M, Asahara H, Ohya S, Tanaka M. Electric Field Control of Spin-Orbit Torque Magnetization Switching in a Spin-Orbit Ferromagnet Single Layer. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2023; 10:e2301540. [PMID: 37329321 PMCID: PMC10460875 DOI: 10.1002/advs.202301540] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2023] [Revised: 04/29/2023] [Indexed: 06/19/2023]
Abstract
To achieve a desirable magnitude of spin-orbit torque (SOT) for magnetization switching and realize multifunctional spin logic and memory devices utilizing SOT, controlling the SOT manipulation is vitally important. In conventional SOT bilayer systems, researchers have tried to control the magnetization switching behavior via interfacial oxidization, modulation of spin-orbit effective field, and effective spin Hall angle; however, the switching efficiency is limited by the interface quality. A current-induced effective magnetic field in a single layer of a ferromagnet with strong spin-orbit interactions, the so-called spin-orbit ferromagnet, can be utilized to induce SOT. In spin-orbit ferromagnet systems, electric field application has the potential for manipulating the spin-orbit interactions via carrier concentration modulation. In this work, it is demonstrated that SOT magnetization switching can be successfully controlled via an external electric field using a (Ga, Mn)As single layer. By applying a gate voltage, the switching current density can be solidly and reversibly manipulated with a large ratio of 14.5%, which is ascribed to the successful modulation of the interfacial electric field. The findings of this work help further the understanding of the magnetization switching mechanism and advance the development of gate-controlled SOT devices.
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Affiliation(s)
- Miao Jiang
- School of Materials Science and EngineeringBeijing Institute of TechnologyZhongguancun South Street No.5, HaidianBeijing100081China
- Department of Electrical Engineering and Information SystemsThe University of Tokyo7‐3‐1 Hongo, Bunkyo‐kuTokyo113‐8656Japan
| | - Hirokatsu Asahara
- Department of Electrical Engineering and Information SystemsThe University of Tokyo7‐3‐1 Hongo, Bunkyo‐kuTokyo113‐8656Japan
| | - Shinobu Ohya
- Department of Electrical Engineering and Information SystemsThe University of Tokyo7‐3‐1 Hongo, Bunkyo‐kuTokyo113‐8656Japan
- Center for Spintronics Research Network (CSRN)Graduate School of EngineeringThe University of Tokyo7‐3‐1 Hongo, Bunkyo‐kuTokyo113‐8656Japan
| | - Masaaki Tanaka
- Department of Electrical Engineering and Information SystemsThe University of Tokyo7‐3‐1 Hongo, Bunkyo‐kuTokyo113‐8656Japan
- Center for Spintronics Research Network (CSRN)Graduate School of EngineeringThe University of Tokyo7‐3‐1 Hongo, Bunkyo‐kuTokyo113‐8656Japan
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7
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Anderson CR, Natera-Cordero N, Guarochico-Moreira VH, Grigorieva IV, Vera-Marun IJ. Exploring room temperature spin transport under band gap opening in bilayer graphene. Sci Rep 2023; 13:10343. [PMID: 37365221 PMCID: PMC10293296 DOI: 10.1038/s41598-023-36800-2] [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: 01/01/2023] [Accepted: 06/12/2023] [Indexed: 06/28/2023] Open
Abstract
We study the room-temperature electrical control of charge and spin transport in high-quality bilayer graphene, fully encapsulated with hBN and contacted via 1D spin injectors. We show that spin transport in this device architecture is measurable at room temperature and its spin transport parameters can be modulated by opening of a band gap via a perpendicular displacement field. The modulation of the spin current is dominated by the control of the spin relaxation time with displacement field, demonstrating the basic operation of a spin-based field-effect transistor.
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Affiliation(s)
| | - Noel Natera-Cordero
- Department of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, UK
- Consejo Nacional de Ciencia y Tecnología (CONACyT), Mexico City, Mexico
| | - Victor H Guarochico-Moreira
- Department of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, UK
- Facultad de Ciencias Naturales y Matemáticas, Escuela Superior Politécnica del Litoral, ESPOL, Campus Gustavo Galindo, Km. 30.5 Vía Perimetral, P.O. Box 09-01-5863, 090902, Guayaquil, Ecuador
- Center of Nanotechnology Research and Development (CIDNA), Escuela Superior Politécnica del Litoral, ESPOL, Campus Gustavo Galindo Km 30.5 Vía Perimetral, Guayaquil, Ecuador
| | - Irina V Grigorieva
- Department of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, UK
- National Graphene Institute, University of Manchester, Manchester, M13 9PL, UK
| | - Ivan J Vera-Marun
- Department of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, UK
- National Graphene Institute, University of Manchester, Manchester, M13 9PL, UK
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8
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Gückelhorn J, de-la-Peña S, Scheufele M, Grammer M, Opel M, Geprägs S, Cuevas JC, Gross R, Huebl H, Kamra A, Althammer M. Observation of the Nonreciprocal Magnon Hanle Effect. PHYSICAL REVIEW LETTERS 2023; 130:216703. [PMID: 37295087 DOI: 10.1103/physrevlett.130.216703] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2022] [Revised: 12/14/2022] [Accepted: 04/18/2023] [Indexed: 06/12/2023]
Abstract
The precession of magnon pseudospin about the equilibrium pseudofield, the latter capturing the nature of magnonic eigenexcitations in an antiferromagnet, gives rise to the magnon Hanle effect. Its realization via electrically injected and detected spin transport in an antiferromagnetic insulator demonstrates its high potential for devices and as a convenient probe for magnon eigenmodes and the underlying spin interactions in the antiferromagnet. Here, we observe a nonreciprocity in the Hanle signal measured in hematite using two spatially separated platinum electrodes as spin injector or detector. Interchanging their roles was found to alter the detected magnon spin signal. The recorded difference depends on the applied magnetic field and reverses sign when the signal passes its nominal maximum at the so-called compensation field. We explain these observations in terms of a spin transport direction-dependent pseudofield. The latter leads to a nonreciprocity, which is found to be controllable via the applied magnetic field. The observed nonreciprocal response in the readily available hematite films opens interesting opportunities for realizing exotic physics predicted so far only for antiferromagnets with special crystal structures.
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Affiliation(s)
- Janine Gückelhorn
- Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, D-85748 Garching, Germany
- Technische Universität München, TUM School of Natural Sciences, Physik-Department, D-85748 Garching, Germany
| | - Sebastián de-la-Peña
- Condensed Matter Physics Center (IFIMAC) and Departamento de Física Teórica de la Materia Condensada, Universidad Autónoma de Madrid, E-28049 Madrid, Spain
| | - Monika Scheufele
- Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, D-85748 Garching, Germany
- Technische Universität München, TUM School of Natural Sciences, Physik-Department, D-85748 Garching, Germany
| | - Matthias Grammer
- Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, D-85748 Garching, Germany
- Technische Universität München, TUM School of Natural Sciences, Physik-Department, D-85748 Garching, Germany
| | - Matthias Opel
- Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, D-85748 Garching, Germany
| | - Stephan Geprägs
- Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, D-85748 Garching, Germany
| | - Juan Carlos Cuevas
- Condensed Matter Physics Center (IFIMAC) and Departamento de Física Teórica de la Materia Condensada, Universidad Autónoma de Madrid, E-28049 Madrid, Spain
| | - Rudolf Gross
- Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, D-85748 Garching, Germany
- Technische Universität München, TUM School of Natural Sciences, Physik-Department, D-85748 Garching, Germany
- Munich Center for Quantum Science and Technology (MCQST), D-80799 München, Germany
| | - Hans Huebl
- Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, D-85748 Garching, Germany
- Technische Universität München, TUM School of Natural Sciences, Physik-Department, D-85748 Garching, Germany
- Munich Center for Quantum Science and Technology (MCQST), D-80799 München, Germany
| | - Akashdeep Kamra
- Condensed Matter Physics Center (IFIMAC) and Departamento de Física Teórica de la Materia Condensada, Universidad Autónoma de Madrid, E-28049 Madrid, Spain
| | - Matthias Althammer
- Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, D-85748 Garching, Germany
- Technische Universität München, TUM School of Natural Sciences, Physik-Department, D-85748 Garching, Germany
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9
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Márkus BG, Gmitra M, Dóra B, Csősz G, Fehér T, Szirmai P, Náfrádi B, Zólyomi V, Forró L, Fabian J, Simon F. Ultralong 100 ns spin relaxation time in graphite at room temperature. Nat Commun 2023; 14:2831. [PMID: 37198155 DOI: 10.1038/s41467-023-38288-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Accepted: 04/24/2023] [Indexed: 05/19/2023] Open
Abstract
Graphite has been intensively studied, yet its electron spins dynamics remains an unresolved problem even 70 years after the first experiments. The central quantities, the longitudinal (T1) and transverse (T2) relaxation times were postulated to be equal, mirroring standard metals, but T1 has never been measured for graphite. Here, based on a detailed band structure calculation including spin-orbit coupling, we predict an unexpected behavior of the relaxation times. We find, based on saturation ESR measurements, that T1 is markedly different from T2. Spins injected with perpendicular polarization with respect to the graphene plane have an extraordinarily long lifetime of 100 ns at room temperature. This is ten times more than in the best graphene samples. The spin diffusion length across graphite planes is thus expected to be ultralong, on the scale of ~ 70 μm, suggesting that thin films of graphite - or multilayer AB graphene stacks - can be excellent platforms for spintronics applications compatible with 2D van der Waals technologies. Finally, we provide a qualitative account of the observed spin relaxation based on the anisotropic spin admixture of the Bloch states in graphite obtained from density functional theory calculations.
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Affiliation(s)
- B G Márkus
- Stavropoulos Center for Complex Quantum Matter, Department of Physics and Astronomy, University of Notre Dame, Notre Dame, IN, 46556, USA
- Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, Budapest, H-1525, Hungary
- Department of Physics, Institute of Physics, Budapest University of Technology and Economics, Műegyetem rkp. 3., H-1111, Budapest, Hungary
| | - M Gmitra
- Institute of Physics, Pavol Jozef Šafárik University in Košice, Park Angelinum 9, 040 01, Košice, Slovakia
- Institute of Experimental Physics, Slovak Academy of Sciences, Watsonova 47, 04001, Košice, Slovakia
| | - B Dóra
- Department of Theoretical Physics, Institute of Physics and MTA-BME Lendület Topology and Correlation Research Group Budapest University of Technology and Economics, Műegyetem rkp. 3., H-1111, Budapest, Hungary
| | - G Csősz
- Department of Physics, Institute of Physics, Budapest University of Technology and Economics, Műegyetem rkp. 3., H-1111, Budapest, Hungary
| | - T Fehér
- Department of Physics, Institute of Physics, Budapest University of Technology and Economics, Műegyetem rkp. 3., H-1111, Budapest, Hungary
| | - P Szirmai
- Laboratory of Physics of Complex Matter, École Polytechnique Fédérale de Lausanne, Lausanne, CH-1015, Switzerland
| | - B Náfrádi
- Laboratory of Physics of Complex Matter, École Polytechnique Fédérale de Lausanne, Lausanne, CH-1015, Switzerland
| | - V Zólyomi
- STFC Hartree Centre, Daresbury Laboratory, Daresbury, Warrington WA4 4AD, UK
| | - L Forró
- Stavropoulos Center for Complex Quantum Matter, Department of Physics and Astronomy, University of Notre Dame, Notre Dame, IN, 46556, USA
- Laboratory of Physics of Complex Matter, École Polytechnique Fédérale de Lausanne, Lausanne, CH-1015, Switzerland
| | - J Fabian
- Department of Physics, University of Regensburg, 93040, Regensburg, Germany.
| | - F Simon
- Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, Budapest, H-1525, Hungary.
- Department of Physics, Institute of Physics and ELKH-BME Condensed Matter Research Group Budapest University of Technology and Economics, Műegyetem rkp. 3., H-1111, Budapest, Hungary.
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10
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Fiorentini S, Bendra M, Ender J, de Orio RL, Goes W, Selberherr S, Sverdlov V. Spin and charge drift-diffusion in ultra-scaled MRAM cells. Sci Rep 2022; 12:20958. [PMID: 36471161 PMCID: PMC9723118 DOI: 10.1038/s41598-022-25586-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2022] [Accepted: 12/01/2022] [Indexed: 12/12/2022] Open
Abstract
Designing advanced single-digit shape-anisotropy MRAM cells requires an accurate evaluation of spin currents and torques in magnetic tunnel junctions (MTJs) with elongated free and reference layers. For this purpose, we extended the analysis approach successfully used in nanoscale metallic spin valves to MTJs by introducing proper boundary conditions for the spin currents at the tunnel barrier interfaces, and by employing a conductivity locally dependent on the angle between the magnetization vectors for the charge current. The experimentally measured voltage and angle dependencies of the torques acting on the free layer are thereby accurately reproduced. The switching behavior of ultra-scaled MRAM cells is in agreement with recent experiments on shape-anisotropy MTJs. Using our extended approach is absolutely essential to accurately capture the interplay of the Slonczewski and Zhang-Li torque contributions acting on a textured magnetization in composite free layers with the inclusion of several MgO barriers.
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Affiliation(s)
- Simone Fiorentini
- Christian Doppler Laboratory for Nonvolatile Magnetoresistive Memory and Logic, Vienna, Austria ,grid.5329.d0000 0001 2348 4034Institute for Microelectronics, TU Wien, Gußhausstraße 27–29/E360, 1040 Vienna, Austria
| | - Mario Bendra
- Christian Doppler Laboratory for Nonvolatile Magnetoresistive Memory and Logic, Vienna, Austria ,grid.5329.d0000 0001 2348 4034Institute for Microelectronics, TU Wien, Gußhausstraße 27–29/E360, 1040 Vienna, Austria
| | - Johannes Ender
- Christian Doppler Laboratory for Nonvolatile Magnetoresistive Memory and Logic, Vienna, Austria ,grid.5329.d0000 0001 2348 4034Institute for Microelectronics, TU Wien, Gußhausstraße 27–29/E360, 1040 Vienna, Austria
| | - Roberto L. de Orio
- Christian Doppler Laboratory for Nonvolatile Magnetoresistive Memory and Logic, Vienna, Austria ,grid.5329.d0000 0001 2348 4034Institute for Microelectronics, TU Wien, Gußhausstraße 27–29/E360, 1040 Vienna, Austria
| | | | - Siegfried Selberherr
- grid.5329.d0000 0001 2348 4034Institute for Microelectronics, TU Wien, Gußhausstraße 27–29/E360, 1040 Vienna, Austria
| | - Viktor Sverdlov
- Christian Doppler Laboratory for Nonvolatile Magnetoresistive Memory and Logic, Vienna, Austria ,grid.5329.d0000 0001 2348 4034Institute for Microelectronics, TU Wien, Gußhausstraße 27–29/E360, 1040 Vienna, Austria
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11
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de-la-Peña S, Schlitz R, Vélez S, Cuevas JC, Kamra A. Theory of drift-enabled control in nonlocal magnon transport. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 34:295801. [PMID: 35523156 DOI: 10.1088/1361-648x/ac6d9a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2022] [Accepted: 05/06/2022] [Indexed: 06/14/2023]
Abstract
Electrically injected and detected nonlocal magnon transport has emerged as a versatile method for transporting spin as well as probing the spin excitations in a magnetic insulator. We examine the role of drift currents in this phenomenon as a method for controlling the magnon propagation length. Formulating a phenomenological description, we identify the essential requirements for existence of magnon drift. Guided by this insight, we examine magnetic field gradient, asymmetric contribution to dispersion, and temperature gradient as three representative mechanisms underlying a finite magnon drift velocity, finding temperature gradient to be particularly effective.
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Affiliation(s)
- Sebastián de-la-Peña
- Condensed Matter Physics Center (IFIMAC), Instituto 'Nicolás Cabrera' and Departamento de Física Teórica de la Materia Condensada, Universidad Autónoma de Madrid, E-28049 Madrid, Spain
| | - Richard Schlitz
- Department of Materials, ETH Zürich, 8093 Zürich, Switzerland
| | - Saül Vélez
- Condensed Matter Physics Center (IFIMAC), Instituto 'Nicolás Cabrera' and Departamento de Física Teórica de la Materia Condensada, Universidad Autónoma de Madrid, E-28049 Madrid, Spain
| | - Juan Carlos Cuevas
- Condensed Matter Physics Center (IFIMAC), Instituto 'Nicolás Cabrera' and Departamento de Física Teórica de la Materia Condensada, Universidad Autónoma de Madrid, E-28049 Madrid, Spain
| | - Akashdeep Kamra
- Condensed Matter Physics Center (IFIMAC) and Departamento de Física Teórica de la Materia Condensada, Universidad Autónoma de Madrid, E-28049 Madrid, Spain
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12
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Spin-orbit coupling in buckled monolayer nitrogene. Sci Rep 2022; 12:3201. [PMID: 35217687 PMCID: PMC8881460 DOI: 10.1038/s41598-022-07215-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2021] [Accepted: 02/07/2022] [Indexed: 11/25/2022] Open
Abstract
Buckled monolayer nitrogene has been recently predicted to be stable above the room temperature. The low atomic number of nitrogen atom suggests, that spin–orbit coupling in nitrogene is weak, similar to graphene or silicene. We employ first principles calculations and perform a systematic study of the intrinsic and extrinsic spin–orbit coupling in this material. We calculate the spin mixing parameter \documentclass[12pt]{minimal}
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\begin{document}$$b^2$$\end{document}b2, reflecting the strength of the intrinsic spin–orbit coupling and find, that \documentclass[12pt]{minimal}
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\begin{document}$$\Omega$$\end{document}Ω. We find, that \documentclass[12pt]{minimal}
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\begin{document}$$\Omega$$\end{document}Ω are on the order of a single \documentclass[12pt]{minimal}
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\begin{document}$$\Omega$$\end{document}Ω is also anisotropic, in particular for the conduction electrons.
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Nishizawa N, Munekata H. Lateral-Type Spin-Photonics Devices: Development and Applications. MICROMACHINES 2021; 12:mi12060644. [PMID: 34072992 PMCID: PMC8226829 DOI: 10.3390/mi12060644] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Revised: 05/22/2021] [Accepted: 05/29/2021] [Indexed: 11/13/2022]
Abstract
Spin-photonic devices, represented by spin-polarized light emitting diodes and spin-polarized photodiodes, have great potential for practical use in circularly polarized light (CPL) applications. Focusing on the lateral-type spin-photonic devices that can exchange CPL through their side facets, this review describes their functions in practical CPL applications in terms of: (1) Compactness and integrability, (2) stand-alone (monolithic) nature, (3) room temperature operation, (4) emission with high circular polarization, (5) polarization controllability, and (6) CPL detection. Furthermore, it introduces proposed CPL applications in a wide variety of fields and describes the application of these devices in biological diagnosis using CPL scattering. Finally, it discusses the current state of spin-photonic devices and their applications and future prospects.
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14
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Wang G, Qin W, Wang S, Teketel BS, Yu W, Luo T, Xu B, Lin B. CrI 3/Y 2CH 2 Heterointerface-Induced Stable Half-Metallicity of Two-Dimensional CrI 3 Monolayer Ferromagnets. ACS APPLIED MATERIALS & INTERFACES 2021; 13:16694-16703. [PMID: 33818069 DOI: 10.1021/acsami.1c01768] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Two-dimensional (2D) CrI3 monolayer ferromagnets are key to the development of future miniature spintronic devices and modulating them into a half-metal will greatly expand the application scenarios of CrI3 in nanospintronics. Nevertheless, existing strategies to induce half-metallicity of a CrI3 monolayer remain experimentally challenging and have unstable issues. In this work, the introduction of a 2D electride [Y2C]2+·2e- as an auxiliary layer is shown to be an effective way to achieve the generation of stable half-metallicity in the CrI3 monolayer. When the fully hydrogenated Y2CH2 and ferromagnetic CrI3 monolayer combine to form a heterostructure, surprisingly the appropriate amount of charge injection (0.72 e) turns CrI3 into a half-metal. Hetero-interfacial half-metallicity in CrI3 is an intrinsic one and does not require any chemical functionalization or external physical modification. Therefore, it is advantageous for practical applications of CrI3 in miniature spintronic devices, such as magnetic tunnel junctions, spin valves or spin field-effect transistors. A new strategy of the stable CrI3/Y2CH2 heterostructure was successfully developed to induce the half-metallicity of 2D CrI3 ferromagnets, which is experimentally feasible and half-metallic stable enough. This work paves the way for the application of the CrI3 monolayer in half-metallic-based spintronics.
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Affiliation(s)
- Guoqing Wang
- Institute of Fundamental and Frontier Sciences & School of Mechanical and Electrical Engineering, University of Electronic Science and Technology of China, Chengdu 610054, China
| | - Wenjing Qin
- Department of Physics, Laboratory of Computational Materials Physics, Jiangxi Normal University, Nanchang 330022, China
| | - Siyuan Wang
- Institute of Fundamental and Frontier Sciences & School of Mechanical and Electrical Engineering, University of Electronic Science and Technology of China, Chengdu 610054, China
| | - Birkneh Sirak Teketel
- Institute of Fundamental and Frontier Sciences & School of Mechanical and Electrical Engineering, University of Electronic Science and Technology of China, Chengdu 610054, China
| | - Weili Yu
- The Guo Photonics Laboratory, Changchun Institute of Optics, Fine Mechanics and Physics (CIOMP), Chinese Academy of Science (CAS), Changchun 130033 China
| | - Tianyong Luo
- Institute of Fundamental and Frontier Sciences & School of Mechanical and Electrical Engineering, University of Electronic Science and Technology of China, Chengdu 610054, China
| | - Bo Xu
- Department of Physics, Laboratory of Computational Materials Physics, Jiangxi Normal University, Nanchang 330022, China
| | - Bin Lin
- Institute of Fundamental and Frontier Sciences & School of Mechanical and Electrical Engineering, University of Electronic Science and Technology of China, Chengdu 610054, China
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15
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Deb S, Dhar S. Spin transport in polarization induced two-dimensional electron gas channel in c-GaN nano-wedges. Sci Rep 2021; 11:5277. [PMID: 33674637 PMCID: PMC7935858 DOI: 10.1038/s41598-021-84451-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2020] [Accepted: 02/16/2021] [Indexed: 11/23/2022] Open
Abstract
A two-dimensional electron gas (2DEG), which has recently been shown to develop in the central vertical plane of a wedge-shaped c-oriented GaN nanowall due to spontaneous polarization effect, offers a unique scenario, where the symmetry between the conduction and valence band is preserved over the entire confining potential. This results in the suppression of Rashba coupling even when the shape of the wedge is not symmetric. Here, for such a 2DEG channel, relaxation time for different spin projections is calculated as a function of donor concentration and gate bias. Our study reveals a strong dependence of the relaxation rate on the spin-orientation and density of carriers in the channel. Most interestingly, relaxation of spin oriented along the direction of confinement has been found to be completely switched off. Upon applying a suitable bias at the gate, the process can be switched on again. Exploiting this fascinating effect, an electrically driven spin-transistor has been proposed.
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Affiliation(s)
- Swarup Deb
- Department of Physics, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India
| | - Subhabrata Dhar
- Department of Physics, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India.
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16
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Jiang Y, de Jong EJ, van de Sande V, Gazibegovic S, Badawy G, Bakkers EPAM, Frolov SM. Hysteretic magnetoresistance in nanowire devices due to stray fields induced by micromagnets. NANOTECHNOLOGY 2021; 32:095001. [PMID: 33142271 DOI: 10.1088/1361-6528/abc70f] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
We study hysteretic magnetoresistance in InSb nanowires due to stray magnetic fields from CoFe micromagnets. Devices without any ferromagnetic components show that the magnetoresistance of InSb nanowires commonly exhibits either a local maximum or local minimum at zero magnetic field. Switching of microstrip magnetizations then results in positive or negative hysteretic dependence as conductance maxima or minima shift with respect to the global external field. Stray fields are found to be in the range of tens of millitesla, comparable to the scale over which the nanowire magnetoresistance develops. We observe that the stray field signal is similar to that obtained in devices with ferromagnetic contacts (spin valves). We perform micromagnetic simulations which are in reasonable agreement with the experiment. The use of locally varying magnetic fields may bring new ideas for Majorana circuits in which nanowire networks require control over field orientation at the nanoscale.
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Affiliation(s)
- Y Jiang
- University of Pittsburgh, Pittsburgh, PA 15260, United States of America
| | - E J de Jong
- Eindhoven University of Technology, 5600 MB, Eindhoven, The Netherlands
| | - V van de Sande
- Eindhoven University of Technology, 5600 MB, Eindhoven, The Netherlands
| | - S Gazibegovic
- Eindhoven University of Technology, 5600 MB, Eindhoven, The Netherlands
| | - G Badawy
- Eindhoven University of Technology, 5600 MB, Eindhoven, The Netherlands
| | - E P A M Bakkers
- Eindhoven University of Technology, 5600 MB, Eindhoven, The Netherlands
| | - S M Frolov
- University of Pittsburgh, Pittsburgh, PA 15260, United States of America
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17
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Wimmer T, Kamra A, Gückelhorn J, Opel M, Geprägs S, Gross R, Huebl H, Althammer M. Observation of Antiferromagnetic Magnon Pseudospin Dynamics and the Hanle Effect. PHYSICAL REVIEW LETTERS 2020; 125:247204. [PMID: 33412012 DOI: 10.1103/physrevlett.125.247204] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Revised: 10/02/2020] [Accepted: 11/09/2020] [Indexed: 06/12/2023]
Abstract
We report on experiments demonstrating coherent control of magnon spin transport and pseudospin dynamics in a thin film of the antiferromagnetic insulator hematite utilizing two Pt strips for all-electrical magnon injection and detection. The measured magnon spin signal at the detector reveals an oscillation of its polarity as a function of the externally applied magnetic field. We quantitatively explain our experiments in terms of diffusive magnon transport and a coherent precession of the magnon pseudospin caused by the easy-plane anisotropy and the Dzyaloshinskii-Moriya interaction. This experimental observation can be viewed as the magnonic analog of the electronic Hanle effect and the Datta-Das transistor, unlocking the high potential of antiferromagnetic magnonics toward the realization of rich electronics-inspired phenomena.
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Affiliation(s)
- T Wimmer
- Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany
- Physik-Department, Technische Universität München, 85748 Garching, Germany
| | - A Kamra
- Center for Quantum Spintronics, Department of Physics, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway
| | - J Gückelhorn
- Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany
- Physik-Department, Technische Universität München, 85748 Garching, Germany
| | - M Opel
- Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany
| | - S Geprägs
- Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, 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, D-80799 München, 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, D-80799 München, 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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18
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Abstract
We show that the axial symmetry of the Bychkov–Rashba interaction can be exploited to produce electron spin-flip in a circular quantum dot, without lifting the time reversal symmetry. In order to elucidate this effect, we consider ballistic electron transmission through a two-dimensional circular billiard coupled to two one-dimensional electrodes. Using the tight-binding approximation, we derive the scattering matrix and the effective Hamiltonian for the considered system. Within this approach, we found the conditions for the optimal realization of this effect in the transport properties of the quantum dot. Numerical analysis of the system, extended to the case of two-dimensional electrodes, confirms our findings. The relatively strong quantization of the quantum dot can make this effect robust against the temperature effects.
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19
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Chabi S, Kadel K. Two-Dimensional Silicon Carbide: Emerging Direct Band Gap Semiconductor. NANOMATERIALS (BASEL, SWITZERLAND) 2020; 10:E2226. [PMID: 33182438 PMCID: PMC7697452 DOI: 10.3390/nano10112226] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/08/2020] [Revised: 11/05/2020] [Accepted: 11/06/2020] [Indexed: 11/17/2022]
Abstract
As a direct wide bandgap semiconducting material, two-dimensional, 2D, silicon carbide has the potential to bring revolutionary advances into optoelectronic and electronic devices. It can overcome current limitations with silicon, bulk SiC, and gapless graphene. In addition to SiC, which is the most stable form of monolayer silicon carbide, other compositions, i.e., SixCy, are also predicted to be energetically favorable. Depending on the stoichiometry and bonding, monolayer SixCy may behave as a semiconductor, semimetal or topological insulator. With different Si/C ratios, the emerging 2D silicon carbide materials could attain novel electronic, optical, magnetic, mechanical, and chemical properties that go beyond those of graphene, silicene, and already discovered 2D semiconducting materials. This paper summarizes key findings in 2D SiC and provides insight into how changing the arrangement of silicon and carbon atoms in SiC will unlock incredible electronic, magnetic, and optical properties. It also highlights the significance of these properties for electronics, optoelectronics, magnetic, and energy devices. Finally, it will discuss potential synthesis approaches that can be used to grow 2D silicon carbide.
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Affiliation(s)
- Sakineh Chabi
- Department of Mechanical Engineering, University of New Mexico, Albuquerque, NM 87131, USA;
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20
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Gupta DD, Maiti SK. Can a sample having zero net magnetization produce polarized spin current? JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:505803. [PMID: 32750689 DOI: 10.1088/1361-648x/abac24] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2020] [Accepted: 08/04/2020] [Indexed: 06/11/2023]
Abstract
Antiferromagnetic materials can be the suitable functional elements for designing of future spin based electronic devices, circumventing the use of conventional ferromagnetic materials and spin-orbit coupled systems. In the present work first time we put forward the underlying physical mechanism, to the best of our knowledge, to generate polarized spin current through a magnetic material having zero net magnetization. Our proposal is substantiated by considering a 2D geometry which is composed of several concentric 1D rings where neighboring rings are mutually connected with each other. The misalignment of up and down spin bands, which is the primary requirement to have finite spin polarization, is described analytically and then several aspects of spin polarization are studied numerically. Finally, we discuss experimental realization of the proposed magnetic quantum system. Our analysis can be utilized to any other complicated magnetic geometries, and may open up a new platform for future spintronic applications.
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Affiliation(s)
- Debjani Das Gupta
- Physics and Applied Mathematics Unit, Indian Statistical Institute, 203 Barrackpore Trunk Road, Kolkata-700 108, India
| | - Santanu K Maiti
- Physics and Applied Mathematics Unit, Indian Statistical Institute, 203 Barrackpore Trunk Road, Kolkata-700 108, India
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21
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Vila M, Garcia JH, Cummings AW, Power SR, Groth CW, Waintal X, Roche S. Nonlocal Spin Dynamics in the Crossover from Diffusive to Ballistic Transport. PHYSICAL REVIEW LETTERS 2020; 124:196602. [PMID: 32469541 DOI: 10.1103/physrevlett.124.196602] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2019] [Accepted: 04/27/2020] [Indexed: 06/11/2023]
Abstract
Improved fabrication techniques have enabled the possibility of ballistic transport and unprecedented spin manipulation in ultraclean graphene devices. Spin transport in graphene is typically probed in a nonlocal spin valve and is analyzed using spin diffusion theory, but this theory is not necessarily applicable when charge transport becomes ballistic or when the spin diffusion length is exceptionally long. Here, we study these regimes by performing quantum simulations of graphene nonlocal spin valves. We find that conventional spin diffusion theory fails to capture the crossover to the ballistic regime as well as the limit of long spin diffusion length. We show that the latter can be described by an extension of the current theoretical framework. Finally, by covering the whole range of spin dynamics, our study opens a new perspective to predict and scrutinize spin transport in graphene and other two-dimensional material-based ultraclean devices.
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Affiliation(s)
- Marc Vila
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, Bellaterra, 08193 Barcelona, Spain
- Department of Physics, Universitat Autònoma de Barcelona, Campus UAB, Bellaterra, 08193 Barcelona, Spain
| | - Jose H Garcia
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, Bellaterra, 08193 Barcelona, Spain
| | - Aron W Cummings
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, Bellaterra, 08193 Barcelona, Spain
| | - Stephen R Power
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, Bellaterra, 08193 Barcelona, Spain
- Universitat Autònoma de Barcelona, Campus UAB, Bellaterra, 08193 Barcelona, Spain
- School of Physics, Trinity College Dublin, Dublin 2, Ireland
| | - Christoph W Groth
- Université Grenoble Alpes, CEA, IRIG-PHELIQS, 38000 Grenoble, France
| | - Xavier Waintal
- Université Grenoble Alpes, CEA, IRIG-PHELIQS, 38000 Grenoble, France
| | - Stephan Roche
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, Bellaterra, 08193 Barcelona, Spain
- ICREA-Institució Catalana de Recerca i Estudis Avançats, 08010 Barcelona, Spain
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22
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Abendroth JM, Stemer DM, Bloom BP, Roy P, Naaman R, Waldeck DH, Weiss PS, Mondal PC. Spin Selectivity in Photoinduced Charge-Transfer Mediated by Chiral Molecules. ACS NANO 2019; 13:4928-4946. [PMID: 31016968 DOI: 10.1021/acsnano.9b01876] [Citation(s) in RCA: 54] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Optical control and readout of electron spin and spin currents in thin films and nanostructures have remained attractive yet challenging goals for emerging technologies designed for applications in information processing and storage. Recent advances in room-temperature spin polarization using nanometric chiral molecular assemblies suggest that chemically modified surfaces or interfaces can be used for optical spin conversion by exploiting photoinduced charge separation and injection from well-coupled organic chromophores or quantum dots. Using light to drive photoexcited charge-transfer processes mediated by molecules with central or helical chirality enables indirect measurements of spin polarization attributed to the chiral-induced spin selectivity effect and of the efficiency of spin-dependent electron transfer relative to competitive relaxation pathways. Herein, we highlight recent approaches used to detect and to analyze spin selectivity in photoinduced charge transfer including spin-transfer torque for local magnetization, nanoscale charge separation and polarization, and soft ferromagnetic substrate magnetization- and chirality-dependent photoluminescence. Building on these methods through systematic investigation of molecular and environmental parameters that influence spin filtering should elucidate means to manipulate electron spins and photoexcited states for room-temperature optoelectronic and photospintronic applications.
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Affiliation(s)
- John M Abendroth
- California NanoSystems Institute , University of California, Los Angeles , Los Angeles , California 90095 , United States
- Department of Chemistry and Biochemistry , University of California, Los Angeles , Los Angeles , California 90095 , United States
| | - Dominik M Stemer
- California NanoSystems Institute , University of California, Los Angeles , Los Angeles , California 90095 , United States
- Department of Materials Science and Engineering , University of California, Los Angeles , Los Angeles , California 90095 , United States
| | - Brian P Bloom
- Department of Chemistry , University of Pittsburgh , Pittsburgh , Pennsylvania 15260 , United States
| | - Partha Roy
- Department of Chemistry , Central University of Rajasthan , Kishangarh 305817 Ajmer , India
| | - Ron Naaman
- Department of Chemical and Biological Physics , Weizmann Institute of Science , Rehovot 76100 , Israel
| | - David H Waldeck
- Department of Chemistry , University of Pittsburgh , Pittsburgh , Pennsylvania 15260 , United States
| | - Paul S Weiss
- California NanoSystems Institute , University of California, Los Angeles , Los Angeles , California 90095 , United States
- Department of Chemistry and Biochemistry , University of California, Los Angeles , Los Angeles , California 90095 , United States
- Department of Materials Science and Engineering , University of California, Los Angeles , Los Angeles , California 90095 , United States
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23
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Safeer CK, Ingla-Aynés J, Herling F, Garcia JH, Vila M, Ontoso N, Calvo MR, Roche S, Hueso LE, Casanova F. Room-Temperature Spin Hall Effect in Graphene/MoS 2 van der Waals Heterostructures. NANO LETTERS 2019; 19:1074-1082. [PMID: 30608710 DOI: 10.1021/acs.nanolett.8b04368] [Citation(s) in RCA: 62] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Graphene is an excellent material for long-distance spin transport but allows little spin manipulation. Transition-metal dichalcogenides imprint their strong spin-orbit coupling into graphene via the proximity effect, and it has been predicted that efficient spin-to-charge conversion due to spin Hall and Rashba-Edelstein effects could be achieved. Here, by combining Hall probes with ferromagnetic electrodes, we unambiguously demonstrate experimentally the spin Hall effect in graphene induced by MoS2 proximity and for varying temperatures up to room temperature. The fact that spin transport and the spin Hall effect occur in different parts of the same material gives rise to a hitherto unreported efficiency for the spin-to-charge voltage output. Additionally, for a single graphene/MoS2 heterostructure-based device, we evidence a superimposed spin-to-charge current conversion that can be indistinguishably associated with either the proximity-induced Rashba-Edelstein effect in graphene or the spin Hall effect in MoS2. By a comparison of our results to theoretical calculations, the latter scenario is found to be the most plausible one. Our findings pave the way toward the combination of spin information transport and spin-to-charge conversion in two-dimensional materials, opening exciting opportunities in a variety of future spintronic applications.
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Affiliation(s)
- C K Safeer
- CIC nanoGUNE , 20018 Donostia-San Sebastian , Basque Country , Spain
| | - Josep Ingla-Aynés
- CIC nanoGUNE , 20018 Donostia-San Sebastian , Basque Country , Spain
| | - Franz Herling
- CIC nanoGUNE , 20018 Donostia-San Sebastian , Basque Country , Spain
| | - José H Garcia
- Catalan Institute of Nanoscience and Nanotechnology (ICN2) , CSIC and The Barcelona Institute of Science and Technology , Campus UAB , 08193 Bellaterra , Catalonia , Spain
| | - Marc Vila
- Catalan Institute of Nanoscience and Nanotechnology (ICN2) , CSIC and The Barcelona Institute of Science and Technology , Campus UAB , 08193 Bellaterra , Catalonia , Spain
- Department of Physics , Universitat Autònoma de Barcelona , Campus UAB , 08193 Bellaterra , Catalonia , Spain
| | - Nerea Ontoso
- CIC nanoGUNE , 20018 Donostia-San Sebastian , Basque Country , Spain
| | - M Reyes Calvo
- CIC nanoGUNE , 20018 Donostia-San Sebastian , Basque Country , Spain
- IKERBASQUE , Basque Foundation for Science , 48013 Bilbao , Basque Country , Spain
| | - Stephan Roche
- Catalan Institute of Nanoscience and Nanotechnology (ICN2) , CSIC and The Barcelona Institute of Science and Technology , Campus UAB , 08193 Bellaterra , Catalonia , Spain
- ICREA - Institució Catalana de Recerca i Estudis Avançats , 08010 Barcelona , Catalonia , Spain
| | - Luis E Hueso
- CIC nanoGUNE , 20018 Donostia-San Sebastian , Basque Country , Spain
- IKERBASQUE , Basque Foundation for Science , 48013 Bilbao , Basque Country , Spain
| | - Fèlix Casanova
- CIC nanoGUNE , 20018 Donostia-San Sebastian , Basque Country , Spain
- IKERBASQUE , Basque Foundation for Science , 48013 Bilbao , Basque Country , Spain
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24
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Santos JI, Rivilla I, Cossío FP, Matxain JM, Grzelczak M, Mazinani SKS, Ugalde JM, Mujica V. Chirality-Induced Electron Spin Polarization and Enantiospecific Response in Solid-State Cross-Polarization Nuclear Magnetic Resonance. ACS NANO 2018; 12:11426-11433. [PMID: 30407788 DOI: 10.1021/acsnano.8b06467] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
NMR-based techniques are supposed to be incapable of distinguishing pure crystalline chemical enantiomers. However, through systematic studies of cross-polarization magic angle spinning (CP-MAS) NMR in a series of amino acids, we have found a rather unexpected behavior in the intensity pattern of optical isomers in hydrogen/nitrogen nuclear polarization transfer that would allow the use of CP NMR as a nondestructive enantioselective detection technique. In all molecules considered, the d isomer yields higher intensity than the l form, while the chemical shift for all nuclei involved remains unchanged. We attribute this striking result to the onset of electron spin polarization, accompanying bond charge polarization through a chiral center, a secondary mechanism for polarization transfer that is triggered only in the CP experimental setup. Electron spin polarization is due to the chiral-induced spin selectivity effect (CISS), which creates an enantioselective response, analogous to the one involved in molecular recognition and enantiospecific separation with achiral magnetic substrates. This polarization influences the molecular magnetic environment, modifying the longitudinal relaxation time T1 of 1H, and ultimately provoking the observed asymmetry in the enantiomeric response.
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Affiliation(s)
- Jose I Santos
- SGIker-UPV/EHU , Centro "Joxe Mari Korta" , Tolosa Hiribidea, 72 , E-20018 , Donostia- San Sebastián , Spain
| | - Iván Rivilla
- Department of Organic Chemistry I, Universidad del País Vasco/Euskal Herriko Unibertsitatea (UPV/EHU) , Centro de Innovación en Química Avanzada (ORFEO-CINQA) , Paseo de Manuel Lardizabal 3 , 20018 , Donostia- San Sebastián , Spain
- Donostia International Physics Center , Paseo de Manuel Lardizabal 4 , 20018 , Donostia- San Sebastián , Spain
| | - Fernando P Cossío
- Department of Organic Chemistry I, Universidad del País Vasco/Euskal Herriko Unibertsitatea (UPV/EHU) , Centro de Innovación en Química Avanzada (ORFEO-CINQA) , Paseo de Manuel Lardizabal 3 , 20018 , Donostia- San Sebastián , Spain
- Donostia International Physics Center , Paseo de Manuel Lardizabal 4 , 20018 , Donostia- San Sebastián , Spain
| | - Jon M Matxain
- Donostia International Physics Center , Paseo de Manuel Lardizabal 4 , 20018 , Donostia- San Sebastián , Spain
- Kimika Fakultatea , Euskal Herriko Unibertsitatea (UPV/EHU) Lardizabal Pasealekua 3 , 20018 , Donostia- San Sebastián , Spain
| | - Marek Grzelczak
- Donostia International Physics Center , Paseo de Manuel Lardizabal 4 , 20018 , Donostia- San Sebastián , Spain
- Ikerbasque , Basque Foundation for Science , 48013 , Bilbao , Spain
| | - Shobeir K S Mazinani
- School of Molecular Sciences , Arizona State University , Tempe , Arizona 85287 , United States
| | - Jesus M Ugalde
- Donostia International Physics Center , Paseo de Manuel Lardizabal 4 , 20018 , Donostia- San Sebastián , Spain
- Kimika Fakultatea , Euskal Herriko Unibertsitatea (UPV/EHU) Lardizabal Pasealekua 3 , 20018 , Donostia- San Sebastián , Spain
| | - Vladimiro Mujica
- School of Molecular Sciences , Arizona State University , Tempe , Arizona 85287 , United States
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25
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Leutenantsmeyer JC, Ingla-Aynés J, Fabian J, van Wees BJ. Observation of Spin-Valley-Coupling-Induced Large Spin-Lifetime Anisotropy in Bilayer Graphene. PHYSICAL REVIEW LETTERS 2018; 121:127702. [PMID: 30296147 DOI: 10.1103/physrevlett.121.127702] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2018] [Indexed: 05/22/2023]
Abstract
We report the first observation of a large spin-lifetime anisotropy in bilayer graphene (BLG) fully encapsulated between hexagonal boron nitride. We characterize the out-of-plane (τ_{⊥}) and in-plane (τ_{∥}) spin lifetimes by oblique Hanle spin precession. At 75 K and the charge neutrality point (CNP), we observe a strong anisotropy of τ_{⊥}/τ_{∥}=8±2. This value is comparable to graphene-transition-metal-dichalcogenide heterostructures, whereas our high-quality BLG provides with τ_{⊥} up to 9 ns, a spin lifetime more than 2 orders of magnitude larger. The anisotropy decreases to 3.5±1 at a carrier density of n=6×10^{11} cm^{-2}. Temperature-dependent measurements show above 75 K a decrease of τ_{⊥}/τ_{∥} with increasing temperature, reaching the isotropic case close to room temperature. We explain our findings with electric-field-induced spin-valley coupling arising from the small intrinsic spin-orbit fields in BLG of 12 μeV at the CNP.
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Affiliation(s)
| | - Josep Ingla-Aynés
- Physics of Nanodevices, Zernike Institute for Advanced Materials, University of Groningen, 9747 AG Groningen, Netherlands
| | - Jaroslav Fabian
- Institute for Theoretical Physics, University of Regensburg, 93040 Regensburg, Germany
| | - Bart J van Wees
- Physics of Nanodevices, Zernike Institute for Advanced Materials, University of Groningen, 9747 AG Groningen, Netherlands
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26
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Kountouriotis K, Barreda JL, Keiper TD, Zhang M, Xiong P. Electrical Spin Injection and Detection in Silicon Nanowires with Axial Doping Gradient. NANO LETTERS 2018; 18:4386-4395. [PMID: 29898367 DOI: 10.1021/acs.nanolett.8b01423] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The interest in spin transport in nanoscopic semiconductor channels is driven by both the inevitable miniaturization of spintronics devices toward nanoscale and the rich spin-dependent physics the quantum confinement engenders. For such studies, the all-important issue of the ferromagnet/semiconductor (FM/SC) interface becomes even more critical at nanoscale. Here we elucidate the effects of the FM/SC interface on electrical spin injection and detection at nanoscale dimensions, utilizing a unique type of Si nanowires (NWs) with an inherent axial doping gradient. Two-terminal and nonlocal four-terminal lateral spin-valve measurements were performed using different combinations from a series of FM contacts positioned along the same NW. The data are analyzed with a general model of spin accumulation in a normal channel under electrical spin injection from a FM, which reveals a distinct correlation of decreasing spin-valve signal with increasing injector junction resistance. The observation is attributed to the diminishing contribution of the d-electrons in the FM to the injected current spin polarization with increasing Schottky barrier width. The results demonstrate that there is a window of interface parameters for optimal spin injection efficiency and current spin polarization, which provides important design guidelines for nanospintronic devices with quasi-one-dimensional semiconductor channels.
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Affiliation(s)
| | - Jorge L Barreda
- Department of Physics , Florida State University , Tallahassee , Florida 32306 , United States
| | - Timothy D Keiper
- Department of Physics , Florida State University , Tallahassee , Florida 32306 , United States
| | - Mei Zhang
- Department of Industrial and Manufacturing Engineering, College of Engineering , Florida A&M University-Florida State University (FAMU-FSU) , Tallahassee , Florida 32310 , United States
| | - Peng Xiong
- Department of Physics , Florida State University , Tallahassee , Florida 32306 , United States
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27
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Guimarães MHD, Koopmans B. Spin Accumulation and Dynamics in Inversion-Symmetric van der Waals Crystals. PHYSICAL REVIEW LETTERS 2018; 120:266801. [PMID: 30004759 DOI: 10.1103/physrevlett.120.266801] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2018] [Revised: 04/25/2018] [Indexed: 06/08/2023]
Abstract
Inversion-symmetric materials are forbidden to show an overall spin texture in their band structure in the presence of time-reversal symmetry. However, in van der Waals materials which lack inversion symmetry within a single layer, it has been proposed that a layer-dependent spin texture can arise leading to a coupled spin-layer degree of freedom. Here we use time-resolved Kerr rotation in inversion-symmetric WSe_{2} and MoSe_{2} bulk crystals to study this spin-layer polarization and unveil its dynamics. Our measurements show that the spin-layer relaxation time in WSe_{2} is limited by phonon scattering at high temperatures and that the interlayer hopping can be tuned by a small in-plane magnetic field at low temperatures, enhancing the relaxation rates. We find a significantly lower lifetime for MoSe_{2} which agrees with theoretical expectations of a spin-layer polarization stabilized by the larger spin-orbit coupling in WSe_{2}.
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Affiliation(s)
- M H D Guimarães
- Department of Applied Physics, Eindhoven University of Technology, Eindhoven, Netherlands
| | - B Koopmans
- Department of Applied Physics, Eindhoven University of Technology, Eindhoven, Netherlands
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28
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Pauyac CO, Chshiev M, Manchon A, Nikolaev SA. Spin Hall and Spin Swapping Torques in Diffusive Ferromagnets. PHYSICAL REVIEW LETTERS 2018; 120:176802. [PMID: 29756815 DOI: 10.1103/physrevlett.120.176802] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2017] [Indexed: 06/08/2023]
Abstract
A complete set of the generalized drift-diffusion equations for a coupled charge and spin dynamics in ferromagnets in the presence of extrinsic spin-orbit coupling is derived from the quantum kinetic approach, covering major transport phenomena, such as the spin and anomalous Hall effects, spin swapping, spin precession, and relaxation processes. We argue that the spin swapping effect in ferromagnets is enhanced due to spin polarization, while the overall spin texture induced by the interplay of spin-orbital and spin precession effects displays a complex spatial dependence that can be exploited to generate torques and nucleate or propagate domain walls in centrosymmetric geometries without the use of external polarizers, as opposed to the conventional understanding of spin-orbit mediated torques.
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Affiliation(s)
- Christian Ortiz Pauyac
- Physical Science and Engineering Division (PSE), King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
- Univ. Grenoble Alpes, CNRS, CEA, Grenoble INP, INAC-SPINTEC, 38000 Grenoble, France
| | - Mairbek Chshiev
- Univ. Grenoble Alpes, CNRS, CEA, Grenoble INP, INAC-SPINTEC, 38000 Grenoble, France
| | - Aurelien Manchon
- Physical Science and Engineering Division (PSE), King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
- Computer, Electrical and Mathematical Science and Engineering (CEMSE), King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
| | - Sergey A Nikolaev
- Univ. Grenoble Alpes, CNRS, CEA, Grenoble INP, INAC-SPINTEC, 38000 Grenoble, France
- Ural Federal University, 10 Mira Street, 620002 Ekaterinburg, Russia
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29
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Frank T, Högl P, Gmitra M, Kochan D, Fabian J. Protected Pseudohelical Edge States in Z_{2}-Trivial Proximitized Graphene. PHYSICAL REVIEW LETTERS 2018; 120:156402. [PMID: 29756852 DOI: 10.1103/physrevlett.120.156402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2017] [Revised: 11/10/2017] [Indexed: 06/08/2023]
Abstract
We investigate topological properties of models that describe graphene on realistic substrates which induce proximity spin-orbit coupling in graphene. A Z_{2} phase diagram is calculated for the parameter space of (generally different) intrinsic spin-orbit coupling on the two graphene sublattices, in the presence of Rashba coupling. The most fascinating case is that of staggered intrinsic spin-orbit coupling which, despite being topologically trivial, Z_{2}=0, does exhibit edge states protected by time-reversal symmetry for zigzag ribbons as wide as micrometers. We call these states pseudohelical as their helicity is locked to the sublattice. The spin character and robustness of the pseudohelical modes is best exhibited on a finite flake, which shows that the edge states have zero g factor, carry a pure spin current in the cross section of the flake, and exhibit spin-flip reflectionless tunneling at the armchair edges.
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Affiliation(s)
- Tobias Frank
- Institute for Theoretical Physics, University of Regensburg, 93040 Regensburg, Germany
| | - Petra Högl
- Institute for Theoretical Physics, University of Regensburg, 93040 Regensburg, Germany
| | - Martin Gmitra
- Institute for Theoretical Physics, University of Regensburg, 93040 Regensburg, Germany
| | - Denis Kochan
- Institute for Theoretical Physics, University of Regensburg, 93040 Regensburg, Germany
| | - Jaroslav Fabian
- Institute for Theoretical Physics, University of Regensburg, 93040 Regensburg, Germany
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30
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Abstract
Singlet fission is a photophysical reaction in which a singlet excited electronic state splits into two spin-triplet states. Singlet fission was discovered more than 50 years ago, but the interest in this process has gained a lot of momentum in the past decade due to its potential as a way to boost solar cell efficiencies. This review presents and discusses the most recent advances with respect to the theoretical and computational studies on the singlet fission phenomenon. The work revisits important aspects regarding electronic states involved in the process, the evaluation of fission rates and interstate couplings, the study of the excited state dynamics in singlet fission, and the advances in the design and characterization of singlet fission compounds and materials such as molecular dimers, polymers, or extended structures. Finally, the review tries to pinpoint some aspects that need further improvement and proposes future lines of research for theoretical and computational chemists and physicists in order to further push the understanding and applicability of singlet fission.
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Affiliation(s)
- David Casanova
- Kimika Fakultatea , Euskal Herriko Unibertsitatea (UPV/EHU) and Donostia International Physics Center (DIPC) , P.K. 1072, 20080 Donostia , Euskadi, Spain.,IKERBASQUE, Basque, Foundation for Science , 48013 Bilbao , Euskadi, Spain
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31
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Song K, Soriano D, Cummings AW, Robles R, Ordejón P, Roche S. Spin Proximity Effects in Graphene/Topological Insulator Heterostructures. NANO LETTERS 2018; 18:2033-2039. [PMID: 29481087 DOI: 10.1021/acs.nanolett.7b05482] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Enhancing the spin-orbit interaction in graphene, via proximity effects with topological insulators, could create a novel 2D system that combines nontrivial spin textures with high electron mobility. To engineer practical spintronics applications with such graphene/topological insulator (Gr/TI) heterostructures, an understanding of the hybrid spin-dependent properties is essential. However, to date, despite the large number of experimental studies on Gr/TI heterostructures reporting a great variety of remarkable (spin) transport phenomena, little is known about the true nature of the spin texture of the interface states as well as their role on the measured properties. Here, we use ab initio simulations and tight-binding models to determine the precise spin texture of electronic states in graphene interfaced with a Bi2Se3 topological insulator. Our calculations predict the emergence of a giant spin lifetime anisotropy in the graphene layer, which should be a measurable hallmark of spin transport in Gr/TI heterostructures and suggest novel types of spin devices.
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Affiliation(s)
- Kenan Song
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC, and BIST , Campus UAB , 08193 Barcelona , Spain
| | - David Soriano
- QuantaLab & International Iberian Nanotechnology Laboratory (INL) , Av. Mestre José Veiga , 4715-330 Braga , Portugal
| | - Aron W Cummings
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC, and BIST , Campus UAB , 08193 Barcelona , Spain
| | - Roberto Robles
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC, and BIST , Campus UAB , 08193 Barcelona , Spain
| | - Pablo Ordejón
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC, and BIST , Campus UAB , 08193 Barcelona , Spain
| | - Stephan Roche
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC, and BIST , Campus UAB , 08193 Barcelona , Spain
- ICREA - Institució Catalana de Recerca i Estudis Avançats , 08010 Barcelona , Spain
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32
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Garcia JH, Vila M, Cummings AW, Roche S. Spin transport in graphene/transition metal dichalcogenide heterostructures. Chem Soc Rev 2018; 47:3359-3379. [DOI: 10.1039/c7cs00864c] [Citation(s) in RCA: 112] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
This review summarizes the theoretical and experimental studies of spin transport in graphene interfaced with transition metal dichalcogenides, and assesses its potential for future spintronic applications.
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Affiliation(s)
- Jose H. Garcia
- Catalan Institute of Nanoscience and Nanotechnology (ICN2)
- CSIC and BIST
- 08193 Barcelona
- Spain
| | - Marc Vila
- Catalan Institute of Nanoscience and Nanotechnology (ICN2)
- CSIC and BIST
- 08193 Barcelona
- Spain
- Department of Physics
| | - Aron W. Cummings
- Catalan Institute of Nanoscience and Nanotechnology (ICN2)
- CSIC and BIST
- 08193 Barcelona
- Spain
| | - Stephan Roche
- Catalan Institute of Nanoscience and Nanotechnology (ICN2)
- CSIC and BIST
- 08193 Barcelona
- Spain
- ICREA – Institució Catalana de Recerca i Estudis Avançats
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33
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Ghiasi TS, Ingla-Aynés J, Kaverzin AA, van Wees BJ. Large Proximity-Induced Spin Lifetime Anisotropy in Transition-Metal Dichalcogenide/Graphene Heterostructures. NANO LETTERS 2017; 17:7528-7532. [PMID: 29172543 PMCID: PMC5770138 DOI: 10.1021/acs.nanolett.7b03460] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/13/2017] [Revised: 10/24/2017] [Indexed: 05/22/2023]
Abstract
Van der Waals heterostructures have become a paradigm for designing new materials and devices in which specific functionalities can be tailored by combining the properties of the individual 2D layers. A single layer of transition-metal dichalcogenide (TMD) is an excellent complement to graphene (Gr) because the high quality of charge and spin transport in Gr is enriched with the large spin-orbit coupling of the TMD via the proximity effect. The controllable spin-valley coupling makes these heterostructures particularly attractive for spintronic and opto-valleytronic applications. In this work, we study spin precession in a monolayer MoSe2/Gr heterostructure and observe an unconventional, dramatic modulation of the spin signal, showing 1 order of magnitude longer lifetime of out-of-plane spins compared to that of in-plane spins (τ⊥ ≈ 40 ps and τ∥ ≈ 3.5 ps). This demonstration of a large spin lifetime anisotropy in TMD/Gr heterostructures, is a direct evidence of induced spin-valley coupling in Gr and provides an accessible route for manipulation of spin dynamics in Gr, interfaced with TMDs.
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34
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Cummings AW, Garcia JH, Fabian J, Roche S. Giant Spin Lifetime Anisotropy in Graphene Induced by Proximity Effects. PHYSICAL REVIEW LETTERS 2017; 119:206601. [PMID: 29219336 DOI: 10.1103/physrevlett.119.206601] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2017] [Indexed: 06/07/2023]
Abstract
We report on fundamental aspects of spin dynamics in heterostructures of graphene and transition metal dichalcogenides (TMDCs). By using realistic models derived from first principles we compute the spin lifetime anisotropy, defined as the ratio of lifetimes for spins pointing out of the graphene plane to those pointing in the plane. We find that the anisotropy can reach values of tens to hundreds, which is unprecedented for typical 2D systems with spin-orbit coupling and indicates a qualitatively new regime of spin relaxation. This behavior is mediated by spin-valley locking, which is strongly imprinted onto graphene by TMDCs. Our results indicate that this giant spin lifetime anisotropy can serve as an experimental signature of materials with strong spin-valley locking, including graphene-TMDC heterostructures and TMDCs themselves. Additionally, materials with giant spin lifetime anisotropy can provide an exciting platform for manipulating the valley and spin degrees of freedom, and for designing novel spintronic devices.
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Affiliation(s)
- Aron W Cummings
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, Bellaterra, 08193 Barcelona, Spain
| | - Jose H Garcia
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, Bellaterra, 08193 Barcelona, Spain
| | - Jaroslav Fabian
- Insitute for Theoretical Physics, University of Regensburg, 93040 Regensburg, Germany
| | - Stephan Roche
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, Bellaterra, 08193 Barcelona, Spain
- ICREA, Institució Catalana de Recerca i Estudis Avançats, 08070 Barcelona, Spain
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35
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Gmitra M, Fabian J. Proximity Effects in Bilayer Graphene on Monolayer WSe_{2}: Field-Effect Spin Valley Locking, Spin-Orbit Valve, and Spin Transistor. PHYSICAL REVIEW LETTERS 2017; 119:146401. [PMID: 29053300 DOI: 10.1103/physrevlett.119.146401] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2017] [Indexed: 05/21/2023]
Abstract
Proximity orbital and spin-orbit effects of bilayer graphene on monolayer WSe_{2} are investigated from first principles. We find that the built-in electric field induces an orbital band gap of about 10 meV in bilayer graphene. Remarkably, the proximity spin-orbit splitting for holes is 2 orders of magnitude-the spin-orbit splitting of the valence band at K is about 2 meV-more than for electrons. Effectively, holes experience spin valley locking due to the strong proximity of the lower graphene layer to WSe_{2}. However, applying an external transverse electric field of some 1 V/nm, countering the built-in field of the heterostructure, completely reverses this effect and allows, instead of holes, electrons to be spin valley locked with 2 meV spin-orbit splitting. Such a behavior constitutes a highly efficient field-effect spin-orbit valve, making bilayer graphene on WSe_{2} a potential platform for a field-effect spin transistor.
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Affiliation(s)
- Martin Gmitra
- Institute for Theoretical Physics, University of Regensburg, 93040 Regensburg, Germany
| | - Jaroslav Fabian
- Institute for Theoretical Physics, University of Regensburg, 93040 Regensburg, Germany
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36
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Scharf B, Xu G, Matos-Abiague A, Žutić I. Magnetic Proximity Effects in Transition-Metal Dichalcogenides: Converting Excitons. PHYSICAL REVIEW LETTERS 2017; 119:127403. [PMID: 29341642 DOI: 10.1103/physrevlett.119.127403] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2017] [Indexed: 06/07/2023]
Abstract
The two-dimensional character and reduced screening in monolayer transition-metal dichalcogenides (TMDs) lead to the ubiquitous formation of robust excitons with binding energies orders of magnitude larger than in bulk semiconductors. Focusing on neutral excitons, bound electron-hole pairs that dominate the optical response in TMDs, it is shown that they can provide fingerprints for magnetic proximity effects in magnetic heterostructures. These proximity effects cannot be described by the widely used single-particle description but instead reveal the possibility of a conversion between optically inactive and active excitons by rotating the magnetization of the magnetic substrate. With recent breakthroughs in fabricating Mo- and W-based magnetic TMD heterostructures, this emergent optical response can be directly tested experimentally.
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Affiliation(s)
- Benedikt Scharf
- Institute for Theoretical Physics and Astrophysics, University of Würzburg, Am Hubland, 97074 Würzburg, Germany
- Institute for Theoretical Physics, University of Regensburg, 93040 Regensburg, Germany
- Department of Physics, University at Buffalo, State University of New York, Buffalo, New York 14260, USA
| | - Gaofeng Xu
- Department of Physics, University at Buffalo, State University of New York, Buffalo, New York 14260, USA
| | - Alex Matos-Abiague
- Department of Physics, University at Buffalo, State University of New York, Buffalo, New York 14260, USA
| | - Igor Žutić
- Department of Physics, University at Buffalo, State University of New York, Buffalo, New York 14260, USA
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37
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Banik S, Das PK, Bendounan A, Vobornik I, Arya A, Beaulieu N, Fujii J, Thamizhavel A, Sastry PU, Sinha AK, Phase DM, Deb SK. Giant Rashba effect at the topological surface of PrGe revealing antiferromagnetic spintronics. Sci Rep 2017; 7:4120. [PMID: 28646153 PMCID: PMC5482886 DOI: 10.1038/s41598-017-02401-z] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2016] [Accepted: 04/11/2017] [Indexed: 11/17/2022] Open
Abstract
Rashba spin-orbit splitting in the magnetic materials opens up a new perspective in the field of spintronics. Here, we report a giant Rashba spin-orbit splitting on the PrGe [010] surface in the paramagnetic phase with Rashba coefficient α R = 5 eVÅ. We find that α R can be tuned in this system as a function of temperature at different magnetic phases. Rashba type spin polarized surface states originates due to the strong hybridization between Pr 4f states with the conduction electrons. Significant changes observed in the spin polarized surface states across the magnetic transitions are due to the competition between Dzyaloshinsky-Moriya interaction and exchange interaction present in this system. Presence of Dzyaloshinsky-Moriya interaction on the topological surface give rise to Saddle point singularity which leads to electron-like and hole-like Rashba spin split bands in the [Formula: see text] and [Formula: see text] directions, respectively. Supporting evidences of Dzyaloshinsky-Moriya interaction have been obtained as anisotropic magnetoresistance with respect to field direction and first-order type hysteresis in the X-ray diffraction measurements. A giant negative magnetoresistance of 43% in the antiferromagnetic phase and tunable Rashba parameter with temperature makes this material a suitable candidate for application in the antiferromagnetic spintronic devices.
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Affiliation(s)
- Soma Banik
- Synchrotrons Utilization Section, Raja Ramanna Centre for Advanced Technology, Indore, 452013, India.
| | - Pranab Kumar Das
- Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai, 400005, India
- International Centre for Theoretical Physics, Strada Costiera 11, 34100, Trieste, Italy
| | - Azzedine Bendounan
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin, BP 48, FR-91192, Gif-sur-Yvette Cedex, France
| | - Ivana Vobornik
- Istituto Officina dei Materiali (IOM)-CNR, Laboratorio TASC, in Area Science Park, S.S.14, Km 163.5, I-34149, Trieste, Italy
| | - A Arya
- Materials Science Division, Bhabha Atomic Research Centre, Mumbai, 400085, India
| | - Nathan Beaulieu
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin, BP 48, FR-91192, Gif-sur-Yvette Cedex, France
| | - Jun Fujii
- Istituto Officina dei Materiali (IOM)-CNR, Laboratorio TASC, in Area Science Park, S.S.14, Km 163.5, I-34149, Trieste, Italy
| | - A Thamizhavel
- Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai, 400005, India
| | - P U Sastry
- Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai, 400085, India
| | - A K Sinha
- Synchrotrons Utilization Section, Raja Ramanna Centre for Advanced Technology, Indore, 452013, India
| | - D M Phase
- UGC-DAE Consortium for Scientific Research, Khandwa Road, Indore, 452001, India
| | - S K Deb
- Synchrotrons Utilization Section, Raja Ramanna Centre for Advanced Technology, Indore, 452013, India
- Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India
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38
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Singh S, Katoch J, Zhu T, Meng KY, Liu T, Brangham JT, Yang F, Flatté ME, Kawakami RK. Strong Modulation of Spin Currents in Bilayer Graphene by Static and Fluctuating Proximity Exchange Fields. PHYSICAL REVIEW LETTERS 2017; 118:187201. [PMID: 28524685 DOI: 10.1103/physrevlett.118.187201] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2016] [Indexed: 06/07/2023]
Abstract
Two-dimensional materials provide a unique platform to explore the full potential of magnetic proximity-driven phenomena, which can be further used for applications in next-generation spintronic devices. Of particular interest is to understand and control spin currents in graphene by the magnetic exchange field of a nearby ferromagnetic material in graphene-ferromagnetic-insulator (FMI) heterostructures. Here, we present the experimental study showing the strong modulation of spin currents in graphene layers by controlling the direction of the exchange field due to FMI magnetization. Owing to clean interfaces, a strong magnetic exchange coupling leads to the experimental observation of complete spin modulation at low externally applied magnetic fields in short graphene channels. Additionally, we discover that the graphene spin current can be fully dephased by randomly fluctuating exchange fields. This is manifested as an unusually strong temperature dependence of the nonlocal spin signals in graphene, which is due to spin relaxation by thermally induced transverse fluctuations of the FMI magnetization.
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Affiliation(s)
- Simranjeet Singh
- Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA
| | - Jyoti Katoch
- Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA
| | - Tiancong Zhu
- Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA
| | - Keng-Yuan Meng
- Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA
| | - Tianyu Liu
- Optical Science and Technology Center and Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa 52242, USA
| | - Jack T Brangham
- Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA
| | - Fengyuan Yang
- Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA
| | - Michael E Flatté
- Optical Science and Technology Center and Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa 52242, USA
| | - Roland K Kawakami
- Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA
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39
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Zhong D, Seyler KL, Linpeng X, Cheng R, Sivadas N, Huang B, Schmidgall E, Taniguchi T, Watanabe K, McGuire MA, Yao W, Xiao D, Fu KMC, Xu X. Van der Waals engineering of ferromagnetic semiconductor heterostructures for spin and valleytronics. SCIENCE ADVANCES 2017; 3:e1603113. [PMID: 28580423 PMCID: PMC5451195 DOI: 10.1126/sciadv.1603113] [Citation(s) in RCA: 257] [Impact Index Per Article: 36.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2016] [Accepted: 04/03/2017] [Indexed: 05/22/2023]
Abstract
The integration of magnetic material with semiconductors has been fertile ground for fundamental science as well as of great practical interest toward the seamless integration of information processing and storage. We create van der Waals heterostructures formed by an ultrathin ferromagnetic semiconductor CrI3 and a monolayer of WSe2. We observe unprecedented control of the spin and valley pseudospin in WSe2, where we detect a large magnetic exchange field of nearly 13 T and rapid switching of the WSe2 valley splitting and polarization via flipping of the CrI3 magnetization. The WSe2 photoluminescence intensity strongly depends on the relative alignment between photoexcited spins in WSe2 and the CrI3 magnetization, because of ultrafast spin-dependent charge hopping across the heterostructure interface. The photoluminescence detection of valley pseudospin provides a simple and sensitive method to probe the intriguing domain dynamics in the ultrathin magnet, as well as the rich spin interactions within the heterostructure.
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Affiliation(s)
- Ding Zhong
- Department of Physics, University of Washington, Seattle, WA 98195, USA
| | - Kyle L. Seyler
- Department of Physics, University of Washington, Seattle, WA 98195, USA
| | - Xiayu Linpeng
- Department of Physics, University of Washington, Seattle, WA 98195, USA
| | - Ran Cheng
- Department of Physics, Carnegie Mellon University, Pittsburg, PA 15213, USA
| | - Nikhil Sivadas
- Department of Physics, Carnegie Mellon University, Pittsburg, PA 15213, USA
| | - Bevin Huang
- Department of Physics, University of Washington, Seattle, WA 98195, USA
| | - Emma Schmidgall
- Department of Physics, University of Washington, Seattle, WA 98195, USA
| | - Takashi Taniguchi
- National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Kenji Watanabe
- National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Michael A. McGuire
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Wang Yao
- Department of Physics and Center of Theoretical and Computational Physics, University of Hong Kong, Hong Kong, China
| | - Di Xiao
- Department of Physics, Carnegie Mellon University, Pittsburg, PA 15213, USA
| | - Kai-Mei C. Fu
- Department of Physics, University of Washington, Seattle, WA 98195, USA
- Department of Electrical Engineering, University of Washington, Seattle, WA 98195, USA
| | - Xiaodong Xu
- Department of Physics, University of Washington, Seattle, WA 98195, USA
- Department of Materials Science and Engineering, University of Washington, Seattle, WA 98195, USA
- Corresponding author.
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40
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Feng YP, Shen L, Yang M, Wang A, Zeng M, Wu Q, Chintalapati S, Chang CR. Prospects of spintronics based on 2D materials. WILEY INTERDISCIPLINARY REVIEWS-COMPUTATIONAL MOLECULAR SCIENCE 2017. [DOI: 10.1002/wcms.1313] [Citation(s) in RCA: 101] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Yuan Ping Feng
- Department of Physics; National University of Singapore; Singapore
- Centre for Advanced Two-dimensional Materials; National University of Singapore; Singapore
| | - Lei Shen
- Department of Mechanical Engineering; National University of Singapore; Singapore
- Engineering Science Programme; National University of Singapore; Singapore
| | - Ming Yang
- Institute of Materials Science and Engineering; A*STAR; Singapore
| | - Aizhu Wang
- Department of Physics; National University of Singapore; Singapore
- Department of Electrical and Computer Engineering; National University of Singapore; Singapore
| | | | - Qingyun Wu
- Department of Materials Science and Engineering; National University of Singapore; Singapore
| | - Sandhya Chintalapati
- Centre for Advanced Two-dimensional Materials; National University of Singapore; Singapore
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41
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42
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Ciorga M. Electrical spin injection and detection in high mobility 2DEG systems. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2016; 28:453003. [PMID: 27619530 DOI: 10.1088/0953-8984/28/45/453003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
In this review paper we present the current status of research related to the topic of electrical spin injection and detection in two-dimensional electron gas (2DEG) systems, formed typically at the interface between two III-V semiconductor compounds. We discuss both theoretical aspects of spin injection in case of ballistic transport as well as give an overview of available reports on spin injection experiments performed on 2DEG structures. In the experimental part we focus particularly on our recent work on all-semiconductor structures with a 2DEG confined at an inverted GaAs/(Al,Ga)As interface and with a ferromagnetic semiconductor (Ga,Mn)As employed as a source of spin-polarized electrons.
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Affiliation(s)
- M Ciorga
- Institute for Experimental and Applied Physics, University of Regensburg, 93040 Regensburg, Germany
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43
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Scharf B, Matos-Abiague A, Han JE, Hankiewicz EM, Žutić I. Tunneling Planar Hall Effect in Topological Insulators: Spin Valves and Amplifiers. PHYSICAL REVIEW LETTERS 2016; 117:166806. [PMID: 27792378 DOI: 10.1103/physrevlett.117.166806] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/29/2015] [Indexed: 06/06/2023]
Abstract
We investigate tunneling across a single ferromagnetic barrier on the surface of a three-dimensional topological insulator. In the presence of a magnetization component along the bias direction, a tunneling planar Hall conductance (TPHC), transverse to the applied bias, develops. Electrostatic control of the barrier enables a giant Hall angle, with the TPHC exceeding the longitudinal tunneling conductance. By changing the in-plane magnetization direction, it is possible to change the sign of both the longitudinal and transverse differential conductance without opening a gap in the topological surface state. The transport in a topological-insulator-ferromagnet junction can, thus, be drastically altered from a simple spin valve to an amplifier.
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Affiliation(s)
- Benedikt Scharf
- Department of Physics, University at Buffalo, State University of New York, Buffalo, New York 14260, USA
| | - Alex Matos-Abiague
- Department of Physics, University at Buffalo, State University of New York, Buffalo, New York 14260, USA
| | - Jong E Han
- Department of Physics, University at Buffalo, State University of New York, Buffalo, New York 14260, USA
| | - Ewelina M Hankiewicz
- Institute for Theoretical Physics and Astrophysics, University of Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Igor Žutić
- Department of Physics, University at Buffalo, State University of New York, Buffalo, New York 14260, USA
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44
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Buchner M, Högl P, Putz S, Gmitra M, Günther S, Schoen MAW, Kronseder M, Schuh D, Bougeard D, Fabian J, Back CH. Anisotropic Polar Magneto-Optic Kerr Effect of Ultrathin Fe/GaAs(001) Layers due to Interfacial Spin-Orbit Interaction. PHYSICAL REVIEW LETTERS 2016; 117:157202. [PMID: 27768325 DOI: 10.1103/physrevlett.117.157202] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2016] [Indexed: 06/06/2023]
Abstract
We report the observation of the anisotropic polar magneto-optical Kerr effect in thin layers of epitaxial Fe/GaAs(001) at room temperature. A clear twofold symmetry of the Kerr rotation angle depending on the orientation of the linear polarization of the probing laser beam with respect to the crystallographic directions of the sample is detected for ultrathin magnetic films saturated out of the film plane. The amplitude of the anisotropy decreases with increasing Fe film thickness, suggesting that the interfacial region is the origin of the anisotropy. The twofold symmetry is fully reproduced by model calculations based on an interference of interfacial Bychkov-Rashba and Dresselhaus spin-orbit coupling.
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Affiliation(s)
- M Buchner
- Institute of Experimental and Applied Physics, University of Regensburg, Regensburg 93040, Germany
| | - P Högl
- Institute of Theoretical Physics, University of Regensburg, Regensburg 93040, Germany
| | - S Putz
- Institute of Theoretical Physics, University of Regensburg, Regensburg 93040, Germany
| | - M Gmitra
- Institute of Theoretical Physics, University of Regensburg, Regensburg 93040, Germany
| | - S Günther
- Department of Materials, ETH Zürich, Zürich 8093, Switzerland
| | - M A W Schoen
- Institute of Experimental and Applied Physics, University of Regensburg, Regensburg 93040, Germany
| | - M Kronseder
- Institute of Experimental and Applied Physics, University of Regensburg, Regensburg 93040, Germany
| | - D Schuh
- Institute of Experimental and Applied Physics, University of Regensburg, Regensburg 93040, Germany
| | - D Bougeard
- Institute of Experimental and Applied Physics, University of Regensburg, Regensburg 93040, Germany
| | - J Fabian
- Institute of Theoretical Physics, University of Regensburg, Regensburg 93040, Germany
| | - C H Back
- Institute of Experimental and Applied Physics, University of Regensburg, Regensburg 93040, Germany
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45
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Fatin GL, Matos-Abiague A, Scharf B, Žutić I. Wireless Majorana Bound States: From Magnetic Tunability to Braiding. PHYSICAL REVIEW LETTERS 2016; 117:077002. [PMID: 27563991 DOI: 10.1103/physrevlett.117.077002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/2015] [Indexed: 06/06/2023]
Abstract
We propose a versatile platform to investigate the existence of Majorana bound states (MBSs) and their non-Abelian statistics through braiding. This implementation combines a two-dimensional electron gas formed in a semiconductor quantum well grown on the surface of an s-wave superconductor with a nearby array of magnetic tunnel junctions (MTJs). The underlying magnetic textures produced by MTJs provide highly controllable topological phase transitions to confine and transport MBSs in two dimensions, overcoming the requirement for a network of wires. Obtained scaling relations confirm that various semiconductor quantum well materials are suitable for this proposal.
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Affiliation(s)
- Geoffrey L Fatin
- Department of Physics, University at Buffalo, State University of New York, Buffalo, New York 14260, USA
| | - Alex Matos-Abiague
- Department of Physics, University at Buffalo, State University of New York, Buffalo, New York 14260, USA
| | - Benedikt Scharf
- Department of Physics, University at Buffalo, State University of New York, Buffalo, New York 14260, USA
| | - Igor Žutić
- Department of Physics, University at Buffalo, State University of New York, Buffalo, New York 14260, USA
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46
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Enhanced spin-orbit coupling in core/shell nanowires. Nat Commun 2016; 7:12413. [PMID: 27491871 PMCID: PMC4980452 DOI: 10.1038/ncomms12413] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2016] [Accepted: 06/30/2016] [Indexed: 12/02/2022] Open
Abstract
The spin–orbit coupling (SOC) in semiconductors is strongly influenced by structural asymmetries, as prominently observed in bulk crystal structures that lack inversion symmetry. Here we study an additional effect on the SOC: the asymmetry induced by the large interface area between a nanowire core and its surrounding shell. Our experiments on purely wurtzite GaAs/AlGaAs core/shell nanowires demonstrate optical spin injection into a single free-standing nanowire and determine the effective electron g-factor of the hexagonal GaAs wurtzite phase. The spin relaxation is highly anisotropic in time-resolved micro-photoluminescence measurements on single nanowires, showing a significant increase of spin relaxation in external magnetic fields. This behaviour is counterintuitive compared with bulk wurtzite crystals. We present a model for the observed electron spin dynamics highlighting the dominant role of the interface-induced SOC in these core/shell nanowires. This enhanced SOC may represent an interesting tuning parameter for the implementation of spin–orbitronic concepts in semiconductor-based structures. Spin-orbit coupling underlies many important spintronic concepts, and is strongly influenced by crystal symmetry. Here, the authors demonstrate a strong enhancement of spin-orbit coupling in core/shell semiconductor nanowires induced by the large interfacial surface areas
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47
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Ryu J, Kohda M, Nitta J. Observation of the D'yakonov-Perel' Spin Relaxation in Single-Crystalline Pt Thin Films. PHYSICAL REVIEW LETTERS 2016; 116:256802. [PMID: 27391739 DOI: 10.1103/physrevlett.116.256802] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Indexed: 06/06/2023]
Abstract
The spin relaxation mechanism in single-crystalline and polycrystalline platinum (Pt) thin films is revealed by a quantum interference effect. Examining the relationship between the spin relaxation rate and momentum scattering rate by changing Pt thickness, we find that the spin relaxation rate of Pt strongly depends on both crystal structure and thickness even though the quality of material (Pt) is unchanged. In particular, the D'yakonov-Perel' mechanism is considered as a dominant mechanism under cases where scattering events are suppressed or the interface effect is not negligible.
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Affiliation(s)
- Jeongchun Ryu
- Department of Materials Science, Tohoku University, Sendai 980-8579, Japan
| | - Makoto Kohda
- Department of Materials Science, Tohoku University, Sendai 980-8579, Japan
| | - Junsaku Nitta
- Department of Materials Science, Tohoku University, Sendai 980-8579, Japan
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48
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Drögeler M, Franzen C, Volmer F, Pohlmann T, Banszerus L, Wolter M, Watanabe K, Taniguchi T, Stampfer C, Beschoten B. Spin Lifetimes Exceeding 12 ns in Graphene Nonlocal Spin Valve Devices. NANO LETTERS 2016; 16:3533-9. [PMID: 27210240 DOI: 10.1021/acs.nanolett.6b00497] [Citation(s) in RCA: 72] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
We show spin lifetimes of 12.6 ns and spin diffusion lengths as long as 30.5 μm in single layer graphene nonlocal spin transport devices at room temperature. This is accomplished by the fabrication of Co/MgO-electrodes on a Si/SiO2 substrate and the subsequent dry transfer of a graphene-hBN-stack on top of this electrode structure where a large hBN flake is needed in order to diminish the ingress of solvents along the hBN-to-substrate interface. Interestingly, long spin lifetimes are observed despite the fact that both conductive scanning force microscopy and contact resistance measurements reveal the existence of conducting pinholes throughout the MgO spin injection/detection barriers. Compared to previous devices, we observe an enhancement of the spin lifetime in single layer graphene by a factor of 6. We demonstrate that the spin lifetime does not depend on the contact resistance area products when comparing all bottom-up devices indicating that spin absorption at the contacts is not the predominant source for spin dephasing.
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Affiliation(s)
- Marc Drögeler
- 2nd Institute of Physics and JARA-FIT, RWTH Aachen University , 52074 Aachen, Germany
| | - Christopher Franzen
- 2nd Institute of Physics and JARA-FIT, RWTH Aachen University , 52074 Aachen, Germany
| | - Frank Volmer
- 2nd Institute of Physics and JARA-FIT, RWTH Aachen University , 52074 Aachen, Germany
| | - Tobias Pohlmann
- 2nd Institute of Physics and JARA-FIT, RWTH Aachen University , 52074 Aachen, Germany
| | - Luca Banszerus
- 2nd Institute of Physics and JARA-FIT, RWTH Aachen University , 52074 Aachen, Germany
| | - Maik Wolter
- 2nd Institute of Physics and JARA-FIT, RWTH Aachen University , 52074 Aachen, Germany
| | - Kenji Watanabe
- National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - Takashi Taniguchi
- National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - Christoph Stampfer
- 2nd Institute of Physics and JARA-FIT, RWTH Aachen University , 52074 Aachen, Germany
- Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, 52425 Jülich, Germany
| | - Bernd Beschoten
- 2nd Institute of Physics and JARA-FIT, RWTH Aachen University , 52074 Aachen, Germany
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49
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Raes B, Scheerder JE, Costache MV, Bonell F, Sierra JF, Cuppens J, Van de Vondel J, Valenzuela SO. Determination of the spin-lifetime anisotropy in graphene using oblique spin precession. Nat Commun 2016; 7:11444. [PMID: 27157318 PMCID: PMC4865811 DOI: 10.1038/ncomms11444] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2015] [Accepted: 03/28/2016] [Indexed: 11/24/2022] Open
Abstract
We determine the spin-lifetime anisotropy of spin-polarized carriers in graphene. In contrast to prior approaches, our method does not require large out-of-plane magnetic fields and thus it is reliable for both low- and high-carrier densities. We first determine the in-plane spin lifetime by conventional spin precession measurements with magnetic fields perpendicular to the graphene plane. Then, to evaluate the out-of-plane spin lifetime, we implement spin precession measurements under oblique magnetic fields that generate an out-of-plane spin population. We find that the spin-lifetime anisotropy of graphene on silicon oxide is independent of carrier density and temperature down to 150 K, and much weaker than previously reported. Indeed, within the experimental uncertainty, the spin relaxation is isotropic. Altogether with the gate dependence of the spin lifetime, this indicates that the spin relaxation is driven by magnetic impurities or random spin-orbit or gauge fields.
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Affiliation(s)
- Bart Raes
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and The Barcelona Institute of Science and Technology, Campus UAB, Barcelona 08193, Spain
| | - Jeroen E. Scheerder
- INPAC—Institute for Nanoscale Physics and Chemistry, Department of Physics and Astronomy, KU Leuven, Celestijnenlaan 200D, B-3001 Leuven, Belgium
| | - Marius V. Costache
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and The Barcelona Institute of Science and Technology, Campus UAB, Barcelona 08193, Spain
| | - Frédéric Bonell
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and The Barcelona Institute of Science and Technology, Campus UAB, Barcelona 08193, Spain
| | - Juan F. Sierra
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and The Barcelona Institute of Science and Technology, Campus UAB, Barcelona 08193, Spain
| | - Jo Cuppens
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and The Barcelona Institute of Science and Technology, Campus UAB, Barcelona 08193, Spain
| | - Joris Van de Vondel
- INPAC—Institute for Nanoscale Physics and Chemistry, Department of Physics and Astronomy, KU Leuven, Celestijnenlaan 200D, B-3001 Leuven, Belgium
| | - Sergio O. Valenzuela
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and The Barcelona Institute of Science and Technology, Campus UAB, Barcelona 08193, Spain
- Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona 08070, Spain
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50
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Fang H, Xiao M, Rui W, Du J, Tao Z. Magnetic coherent tunnel junctions with periodic grating barrier. Sci Rep 2016; 6:24300. [PMID: 27063998 PMCID: PMC4827029 DOI: 10.1038/srep24300] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2015] [Accepted: 03/23/2016] [Indexed: 11/26/2022] Open
Abstract
A new spintronic theory has been developed for the magnetic tunnel junction (MTJ) with single-crystal barrier. The barrier will be treated as a diffraction grating with intralayer periodicity, the diffracted waves of tunneling electrons thus contain strong coherence, both in charge and especially in spin. The theory can answer the two basic problems present in MgO-based MTJs: (1) Why does the tunneling magnetoresistance (TMR) oscillate with the barrier thickness? (2) Why is the TMR still far away from infinity when the two electrodes are both half-metallic? Other principal features of TMR can also be explained and reproduced by the present work. It also provides possible ways to modulate the oscillation of TMR, and to enhance TMR so that it can tend to infinity. Within the theory, the barrier, as a periodic diffraction grating, can get rid of the confinement in width, it can vary from nanoscale to microscale. Based on those results, a future-generation MTJ is proposed where the three pieces can be fabricated separately and then assembled together, it is especially appropriate for the layered materials, e.g., MoS2 and graphite, and most feasible for industries.
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Affiliation(s)
- Henan Fang
- Nanjing University of Posts and Telecommunications, Nanjing 210023, China
| | - Mingwen Xiao
- Department of Physics, Nanjing University, Nanjing 210093, China
| | - Wenbin Rui
- Department of Physics, Nanjing University, Nanjing 210093, China
| | - Jun Du
- Department of Physics, Nanjing University, Nanjing 210093, China.,Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Zhikuo Tao
- Nanjing University of Posts and Telecommunications, Nanjing 210023, China
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