1
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Escher M, Weber NB, Kühn TJ, Patt M. 2D imaging spin-filter for NanoESCA based on Au/Ir(001) or Fe(001)-p(1×1)O. Ultramicroscopy 2023; 253:113814. [PMID: 37515931 DOI: 10.1016/j.ultramic.2023.113814] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2022] [Revised: 06/30/2023] [Accepted: 07/12/2023] [Indexed: 07/31/2023]
Abstract
A two-dimensional imaging spin-filter for photo-emission electron microscopy is described. The spin-filter is capable of imaging the electron spin polarization of either real space or momentum space electron distributions. As a scattering target either Au/Ir(001) comes into use, where spin sensitivity results from using spin-orbit scattering or Fe(001)-p(1×1)O that exploits exchange interaction. Both scattering targets were characterized with respect to their working points and Sherman function in a separate setup. Spin-polarization images of secondary electrons from the magnetic domains of a poly-crystalline iron sample are shown using both scattering targets. Images with a spin-filter using Au/Ir(001) show more than 104 discrete detection channels which increases the effective two-dimensional figure-of-merit (FoM) of this spin-filter by four orders of magnitude compared to single-channel spin detectors. Using the exchange scattering target two spin-components have been imaged for the first time. A method to detect all three spin-components is also outlined.
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Affiliation(s)
- M Escher
- Focus GmbH, 65510 Hünstetten-Kesselbach, Germany.
| | - N B Weber
- Focus GmbH, 65510 Hünstetten-Kesselbach, Germany
| | - T-J Kühn
- Focus GmbH, 65510 Hünstetten-Kesselbach, Germany
| | - M Patt
- Focus GmbH, 65510 Hünstetten-Kesselbach, Germany
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2
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Jugovac M, Cojocariu I, Sánchez-Barriga J, Gargiani P, Valvidares M, Feyer V, Blügel S, Bihlmayer G, Perna P. Inducing Single Spin-Polarized Flat Bands in Monolayer Graphene. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023; 35:e2301441. [PMID: 37036386 DOI: 10.1002/adma.202301441] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2023] [Revised: 03/27/2023] [Indexed: 06/19/2023]
Abstract
Due to the fundamental and technological implications in driving the appearance of non-trivial, exotic topological spin textures and emerging symmetry-broken phases, flat electronic bands in 2D materials, including graphene, are nowadays a relevant topic in the field of spintronics. Here, via europium doping, single spin-polarized bands are generated in monolayer graphene supported by the Co(0001) surface. The doping is controlled by Eu positioning, allowing for the formation of aK ¯ $\bar{\mathrm{K}}$ -valley localized single spin-polarized low-dispersive parabolic band close to the Fermi energy when Eu is on top, and of a π* flat band with single spin character when Eu is intercalated underneath graphene. In the latter case, Eu also induces a bandgap opening at the Dirac point while the Eu 4f states act as a spin filter, splitting the π band into two spin-polarized branches. The generation of flat bands with single spin character, as revealed by the spin- and angle-resolved photoemission spectroscopy (ARPES) experiments, complemented by density functional theory (DFT) calculations, opens up new pathways toward the realization of spintronic devices exploiting such novel exotic electronic and magnetic states.
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Affiliation(s)
- Matteo Jugovac
- Elettra - Sincrotrone Trieste, S.S. 14 - km 163.5, Basovizza, 34149, Trieste, Italy
| | - Iulia Cojocariu
- Elettra - Sincrotrone Trieste, S.S. 14 - km 163.5, Basovizza, 34149, Trieste, Italy
- Peter Grünberg Institute (PGI-6), Forschungszentrum Jülich GmbH, 52425, Jülich, Germany
- Dipartimento di Fisica, Università degli studi di Trieste, Via A. Valerio 2, 34127, Trieste, Italy
| | - Jaime Sánchez-Barriga
- Helmholtz-Zentrum Berlin für Materialien und Energie, Elektronenspeicherring BESSY II, Albert-Einstein-Str. 15, 12489, Berlin, Germany
- IMDEA Nanociencia, Campus de Cantoblanco, c/ Faraday 9, 28049, Madrid, Spain
| | | | | | - Vitaliy Feyer
- Peter Grünberg Institute (PGI-6), Forschungszentrum Jülich GmbH, 52425, Jülich, Germany
| | - Stefan Blügel
- Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, 52425, Jülich, Germany
| | - Gustav Bihlmayer
- Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, 52425, Jülich, Germany
| | - Paolo Perna
- IMDEA Nanociencia, Campus de Cantoblanco, c/ Faraday 9, 28049, Madrid, Spain
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3
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Janas DM, Droghetti A, Ponzoni S, Cojocariu I, Jugovac M, Feyer V, Radonjić MM, Rungger I, Chioncel L, Zamborlini G, Cinchetti M. Enhancing Electron Correlation at a 3d Ferromagnetic Surface. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023; 35:e2205698. [PMID: 36300806 DOI: 10.1002/adma.202205698] [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: 06/22/2022] [Revised: 10/07/2022] [Indexed: 06/16/2023]
Abstract
Spin-resolved momentum microscopy and theoretical calculations are combined beyond the one-electron approximation to unveil the spin-dependent electronic structure of the interface formed between iron (Fe) and an ordered oxygen (O) atomic layer, and an adsorbate-induced enhancement of electronic correlations is found. It is demonstrated that this enhancement is responsible for a drastic narrowing of the Fe d-bands close to the Fermi energy (EF ) and a reduction of the exchange splitting, which is not accounted for in the Stoner picture of ferromagnetism. In addition, correlation leads to a significant spin-dependent broadening of the electronic bands at higher binding energies and their merging with satellite features, which are manifestations of a pure many-electron behavior. Overall, adatom adsorption can be used to vary the material parameters of transition metal surfaces to access different intermediate electronic correlated regimes, which will otherwise not be accessible. The results show that the concepts developed to understand the physics and chemistry of adsorbate-metal interfaces, relevant for a variety of research areas, from spintronics to catalysis, need to be reconsidered with many-particle effects being of utmost importance. These may affect chemisorption energy, spin transport, magnetic order, and even play a key role in the emergence of ferromagnetism at interfaces between non-magnetic systems.
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Affiliation(s)
| | - Andrea Droghetti
- School of Physics & CRANN, Trinity College, Dublin, D02 PN40, Ireland
| | - Stefano Ponzoni
- TU Dortmund University, Department of Physics, 44227, Dortmund, Germany
| | - Iulia Cojocariu
- Peter Grünberg Institute (PGI-6), Forschungszentrum Jülich GmbH, 52428, Jülich, Germany
| | - Matteo Jugovac
- Peter Grünberg Institute (PGI-6), Forschungszentrum Jülich GmbH, 52428, Jülich, Germany
| | - Vitaliy Feyer
- Peter Grünberg Institute (PGI-6), Forschungszentrum Jülich GmbH, 52428, Jülich, Germany
| | - Miloš M Radonjić
- Institute of Physics Belgrade, University of Belgrade, Pregrevica 118, Belgrade, 11080, Serbia
| | - Ivan Rungger
- National Physical Laboratory, Teddington, TW11 0LW, UK
| | - Liviu Chioncel
- Theoretical Physics III, Center for Electronic Correlations and Magnetism, Institute of Physics and Augsburg Center for Innovative Technologies, University of Augsburg, 86159, Augsburg, Germany
| | | | - Mirko Cinchetti
- TU Dortmund University, Department of Physics, 44227, Dortmund, Germany
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4
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Spanning Fermi arcs in a two-dimensional magnet. Nat Commun 2022; 13:5309. [PMID: 36085323 PMCID: PMC9463448 DOI: 10.1038/s41467-022-32948-z] [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: 12/17/2021] [Accepted: 08/24/2022] [Indexed: 11/08/2022] Open
Abstract
The discovery of topological states of matter has led to a revolution in materials research. When external or intrinsic parameters break symmetries, global properties of topological materials change drastically. A paramount example is the emergence of Weyl nodes under broken inversion symmetry. While a rich variety of non-trivial quantum phases could in principle also originate from broken time-reversal symmetry, realizing systems that combine magnetism with complex topological properties is remarkably elusive. Here, we demonstrate that giant open Fermi arcs are created at the surface of ultrathin hybrid magnets where the Fermi-surface topology is substantially modified by hybridization with a heavy-metal substrate. The interplay between magnetism and topology allows us to control the shape and the location of the Fermi arcs by tuning the magnetization direction. The hybridization points in the Fermi surface can be attributed to a non-trivial mixed topology and induce hot-spots in the Berry curvature, dominating spin and charge transport as well as magneto-electric coupling effects. It has been predicted that elemental Iron, with low dimensionality, will be a topological metal hosting Weyl nodes. Here, Chen et al. grow iron on tungsten, a heavy metal with a strong spin-orbit interaction, and using momentum microscopy, show the emergence of giant open Fermi arcs which can be shaped by varying the magnetization of the iron.
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5
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Polyakov A, Mohseni K, Felici R, Tusche C, Chen YJ, Feyer V, Geck J, Ritschel T, Ernst A, Rubio-Zuazo J, Castro GR, Meyerheim HL, Parkin SSP. Fermi surface chirality induced in a TaSe 2 monosheet formed by a Ta/Bi 2Se 3 interface reaction. Nat Commun 2022; 13:2472. [PMID: 35513364 PMCID: PMC9072342 DOI: 10.1038/s41467-022-30093-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2020] [Accepted: 04/14/2022] [Indexed: 11/09/2022] Open
Abstract
Spin-momentum locking in topological insulators and materials with Rashba-type interactions is an extremely attractive feature for novel spintronic devices and is therefore under intense investigation. Significant efforts are underway to identify new material systems with spin-momentum locking, but also to create heterostructures with new spintronic functionalities. In the present study we address both subjects and investigate a van der Waals-type heterostructure consisting of the topological insulator Bi2Se3 and a single Se-Ta-Se triple-layer (TL) of H-type TaSe2 grown by a method which exploits an interface reaction between the adsorbed metal and selenium. We then show, using surface x-ray diffraction, that the symmetry of the TaSe2-like TL is reduced from D3h to C3v resulting from a vertical atomic shift of the tantalum atom. Spin- and momentum-resolved photoemission indicates that, owing to the symmetry lowering, the states at the Fermi surface acquire an in-plane spin component forming a surface contour with a helical Rashba-like spin texture, which is coupled to the Dirac cone of the substrate. Our approach provides a route to realize chiral two-dimensional electron systems via interface engineering in van der Waals epitaxy that do not exist in the corresponding bulk materials. Current limitations of spintronics devices based on bulk topological materials stimulate the search for new materials and structures with interesting spin properties. Here the authors report a chiral spin texture around the Fermi level related to structural symmetry breaking in a TaSe2 layer grown on a Bi2Se3 surface.
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Affiliation(s)
- Andrey Polyakov
- Max-Planck-Institut für Mikrostukturphysik, Weinberg 2, 06120, Halle, Germany
| | - Katayoon Mohseni
- Max-Planck-Institut für Mikrostukturphysik, Weinberg 2, 06120, Halle, Germany
| | - Roberto Felici
- Consiglio Nazionale delle Ricerche - SPIN, Via del Politecnico, 1, Roma, 00133, Italy
| | - Christian Tusche
- Forschungszentrum Jülich GmbH, Peter Grünberg Institut (PGI-6), 52425, Jülich, Germany.,Fakultät für Physik, Universität Duisburg-Essen, 47057, Duisburg, Germany
| | - Ying-Jun Chen
- Forschungszentrum Jülich GmbH, Peter Grünberg Institut (PGI-6), 52425, Jülich, Germany.,Fakultät für Physik, Universität Duisburg-Essen, 47057, Duisburg, Germany
| | - Vitaly Feyer
- Forschungszentrum Jülich GmbH, Peter Grünberg Institut (PGI-6), 52425, Jülich, Germany.,Fakultät für Physik, Universität Duisburg-Essen, 47057, Duisburg, Germany
| | - Jochen Geck
- Institut für Festkörper- und Materialphysik, Technische Universität Dresden, 01062, Dresden, Germany.,Würzburg-Dresden Cluster of Excellence ct.qmat, Technische Universität Dresden, 01062, Dresden, Germany
| | - Tobias Ritschel
- Institut für Festkörper- und Materialphysik, Technische Universität Dresden, 01062, Dresden, Germany
| | - Arthur Ernst
- Institut für Theoretische Physik, Johannes Kepler Universität, A 4040, Linz, Austria
| | - Juan Rubio-Zuazo
- SpLine, Spanish CRG BM25 Beamline at the ESRF (The European Synchrotron), F-38000, Grenoble, France
| | - German R Castro
- SpLine, Spanish CRG BM25 Beamline at the ESRF (The European Synchrotron), F-38000, Grenoble, France
| | - Holger L Meyerheim
- Max-Planck-Institut für Mikrostukturphysik, Weinberg 2, 06120, Halle, Germany.
| | - Stuart S P Parkin
- Max-Planck-Institut für Mikrostukturphysik, Weinberg 2, 06120, Halle, Germany
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6
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Golyashov VA, Rusetsky VS, Shamirzaev TS, Dmitriev DV, Kislykh NV, Mironov AV, Aksenov VV, Tereshchenko OE. Spectral detection of spin-polarized ultra low-energy electrons in semiconductor heterostructures. Ultramicroscopy 2020; 218:113076. [PMID: 32738565 DOI: 10.1016/j.ultramic.2020.113076] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Revised: 07/07/2020] [Accepted: 07/11/2020] [Indexed: 10/23/2022]
Abstract
The circularly polarized cathodoluminescence (CL) technique has been used to study the free spin-polarized electron injection in semiconductor heterostructures with quantum wells (QWs). A polarized electron beam was created by the emission of optically oriented electrons from the p-GaAs(Cs,O) negative electron affinity (NEA) photocathode. The prepared beam was injected in a semiconductor QW target, which was activated by cesium and oxygen to reduce the work function. To study the spin-dependent injection, we developed a spin-detector prototype, which consists of a compact proximity focused vacuum tube with the source and target placed parallel to each other on the opposite ends of the vacuum tube (photodiode). The injection of polarized low-energy electrons into the target by varying the kinetic energy in the range of 0.5-5.0 eV and temperature in the range of 90-300 K was studied. The CL was polarized to 2 % by the injection of 20 % spin-polarized electron beam with the energy of 0.5 eV at room temperature. The asymmetry (Sherman function) of spin detection was estimated. It was shown that the dependence of the CL polarization degree on the injected electron energy is satisfactory described by the model that considers the electron spin relaxation in the heterostructure matrix and QWs. The results demonstrate that semiconductor detectors are promising for the spin-polarimetry applications based on the optical detection of free-electron spin polarization.
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Affiliation(s)
- V A Golyashov
- Rzhanov Institute of Semiconductor Physics, Siberian Branch, Russian Academy of Sciences, Novosibirsk 630090, Russian Federation; Novosibirsk State University, Novosibirsk, 630090, Russian Federation
| | - V S Rusetsky
- Rzhanov Institute of Semiconductor Physics, Siberian Branch, Russian Academy of Sciences, Novosibirsk 630090, Russian Federation; CJSC EKRAN-FEP, Novosibirsk 630060, Russian Federation
| | - T S Shamirzaev
- Rzhanov Institute of Semiconductor Physics, Siberian Branch, Russian Academy of Sciences, Novosibirsk 630090, Russian Federation; Novosibirsk State University, Novosibirsk, 630090, Russian Federation
| | - D V Dmitriev
- Rzhanov Institute of Semiconductor Physics, Siberian Branch, Russian Academy of Sciences, Novosibirsk 630090, Russian Federation
| | - N V Kislykh
- CJSC EKRAN-FEP, Novosibirsk 630060, Russian Federation
| | - A V Mironov
- CJSC EKRAN-FEP, Novosibirsk 630060, Russian Federation
| | - V V Aksenov
- CJSC EKRAN-FEP, Novosibirsk 630060, Russian Federation
| | - O E Tereshchenko
- Rzhanov Institute of Semiconductor Physics, Siberian Branch, Russian Academy of Sciences, Novosibirsk 630090, Russian Federation; Novosibirsk State University, Novosibirsk, 630090, Russian Federation.
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7
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Angrick C, Braun J, Ebert H, Donath M. Spin-dependent electron reflection at W(110). JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 33:115001. [PMID: 33316786 DOI: 10.1088/1361-648x/abd338] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Spin-dependent reflection of low-energy electrons at the W(110) surface caused by spin-orbit interaction was studied experimentally and theoretically. Comprehensive information for a wide range of electron incidence angles and energies was collected via maps for the reflectivity, the spin-dependent reflection asymmetry, and the figure of merit of the spin separation. The experimental results are compared with calculations of the scattering process using a realistic surface potential barrier. The results are discussed in view of possible applications of W(110) as a scattering target in spin-polarization detectors. Possible working points for use in single- as well as multi-channel spin-polarization-detection devices are identified and discussed.
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Affiliation(s)
- C Angrick
- Physikalisches Institut, Westfälische Wilhelms-Universität, Wilhelm-Klemm-Straße 10, 48149 Münster, Germany
| | - J Braun
- Department Chemie, Physikalische Chemie, Ludwig-Maximilians-Universität, Butenandtstraße 11, 81377 München, Germany
| | - H Ebert
- Department Chemie, Physikalische Chemie, Ludwig-Maximilians-Universität, Butenandtstraße 11, 81377 München, Germany
| | - M Donath
- Physikalisches Institut, Westfälische Wilhelms-Universität, Wilhelm-Klemm-Straße 10, 48149 Münster, Germany
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8
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Kink far below the Fermi level reveals new electron-magnon scattering channel in Fe. Nat Commun 2019; 10:505. [PMID: 30705281 PMCID: PMC6355843 DOI: 10.1038/s41467-019-08445-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2018] [Accepted: 01/04/2019] [Indexed: 11/25/2022] Open
Abstract
Many properties of real materials can be modeled using ab initio methods within a single-particle picture. However, for an accurate theoretical treatment of excited states, it is necessary to describe electron-electron correlations including interactions with bosons: phonons, plasmons, or magnons. In this work, by comparing spin- and momentum-resolved photoemission spectroscopy measurements to many-body calculations carried out with a newly developed first-principles method, we show that a kink in the electronic band dispersion of a ferromagnetic material can occur at much deeper binding energies than expected (Eb = 1.5 eV). We demonstrate that the observed spectral signature reflects the formation of a many-body state that includes a photohole bound to a coherent superposition of renormalized spin-flip excitations. The existence of such a many-body state sheds new light on the physics of the electron-magnon interaction which is essential in fields such as spintronics and Fe-based superconductivity. The conduction electron and magnon interactions are essential for the understanding and development of spintronics and superconductivity. Here the authors show a deep binding energy kink in spin-resolved photoemission spectra which is understood as a signature the many-body spin flip excitation in Fe single crystal thin film.
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9
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Tusche C, Ellguth M, Feyer V, Krasyuk A, Wiemann C, Henk J, Schneider CM, Kirschner J. Nonlocal electron correlations in an itinerant ferromagnet. Nat Commun 2018; 9:3727. [PMID: 30213929 PMCID: PMC6137183 DOI: 10.1038/s41467-018-05960-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2017] [Accepted: 07/27/2018] [Indexed: 11/29/2022] Open
Abstract
Our understanding of the properties of ferromagnetic materials, widely used in spintronic devices, is fundamentally based on their electronic band structure. However, even for the most simple elemental ferromagnets, electron correlations are prevalent, requiring descriptions of their electronic structure beyond the simple picture of independent quasi-particles. Here, we give evidence that in itinerant ferromagnets like cobalt these electron correlations are of nonlocal origin, manifested in a complex self-energy Σσ(E,k) that disperses as function of spin σ, energy E, and momentum vector k. Together with one-step photoemission calculations, our experiments allow us to quantify the dispersive behaviour of the complex self-energy over the whole Brillouin zone. At the same time we observe regions of anomalously large "waterfall"-like band renormalization, previously only attributed to strong electron correlations in high-TC superconductors, making itinerant ferromagnets a paradigmatic test case for the interplay between band structure, magnetism, and many-body correlations.
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Affiliation(s)
- Christian Tusche
- Forschungszentrum Jülich, Peter Grünberg Institut (PGI-6), 52425, Jülich, Germany.
- Fakultät für Physik, Universität Duisburg-Essen, 47057, Duisburg, Germany.
- Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, 06120, Halle, Germany.
| | - Martin Ellguth
- Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, 06120, Halle, Germany
| | - Vitaliy Feyer
- Forschungszentrum Jülich, Peter Grünberg Institut (PGI-6), 52425, Jülich, Germany
| | - Alexander Krasyuk
- Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, 06120, Halle, Germany
| | - Carsten Wiemann
- Forschungszentrum Jülich, Peter Grünberg Institut (PGI-6), 52425, Jülich, Germany
| | - Jürgen Henk
- Institut für Physik, Martin-Luther-Universität Halle-Wittenberg, 06120, Halle, Germany
| | - Claus M Schneider
- Forschungszentrum Jülich, Peter Grünberg Institut (PGI-6), 52425, Jülich, Germany
- Fakultät für Physik, Universität Duisburg-Essen, 47057, Duisburg, Germany
| | - Jürgen Kirschner
- Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, 06120, Halle, Germany
- Institut für Physik, Martin-Luther-Universität Halle-Wittenberg, 06120, Halle, Germany
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10
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Pincelli T, Grasselli F, Petrov VN, Torelli P, Rossi G. Performance of photoelectron spin polarimeters with continuous and pulsed sources: from storage rings to free electron lasers. JOURNAL OF SYNCHROTRON RADIATION 2017; 24:175-187. [PMID: 28009557 DOI: 10.1107/s1600577516017513] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2016] [Accepted: 11/01/2016] [Indexed: 06/06/2023]
Abstract
In this work the experimental uncertainties concerning electron spin polarization (SP) under various realistic measurement conditions are theoretically derived. The accuracy of the evaluation of the SP of the photoelectron current is analysed as a function of the detector parameters and specifications, as well as of the characteristics of the photoexcitation sources. In particular, the different behaviour of single counter or twin counter detectors when the intensity fluctuations of the source are considered have been addressed, leading to a new definition of the SP detector performance. The widely used parameter called the figure of merit is shown to be inadequate for describing the efficiency of SP polarimeters, especially when they are operated with time-structured excitation sources such as free-electron lasers. Numerical simulations have been performed and yield strong implications in the choice of the detecting instruments in spin-polarization experiments, that are constrained in a limited measurement time. Our results are therefore applied to the characteristics of a wide set of state-of-the-art spectroscopy facilities all over the world, and an efficiency diagram for SP experiments is derived. These results also define new mathematical instruments for handling the correct statistics of SP measurements in the presence of source intensity fluctuations.
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Affiliation(s)
- T Pincelli
- Dipartimento di Fisica, Università degli studi di Milano, Via Celoria 16, 20133 Milano, Italy
| | - F Grasselli
- Dipartimento di Scienze Fisiche, Informatiche e Matematiche, Università degli Studi di Modena e Reggio Emilia, Via Campi 213/a, Modena, Italy
| | - V N Petrov
- Saint Petersburg State Polytechnical University, Politechnicheskaya Street 29, 195251, Russian Federation
| | - P Torelli
- Laboratorio TASC, IOM-CNR, SS 14 km 163.5, Basovizza, 34149 Trieste, Italy
| | - G Rossi
- Dipartimento di Fisica, Università degli studi di Milano, Via Celoria 16, 20133 Milano, Italy
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11
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Spin texture of time-reversal symmetry invariant surface states on W(110). Sci Rep 2016; 6:29394. [PMID: 27406652 PMCID: PMC4942615 DOI: 10.1038/srep29394] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2016] [Accepted: 06/16/2016] [Indexed: 11/11/2022] Open
Abstract
We find in the case of W(110) previously overlooked anomalous surface states having their spin locked at right angle to their momentum using spin-resolved momentum microscopy. In addition to the well known Dirac-like surface state with Rashba spin texture near the -point, we observe a tilted Dirac cone with circularly shaped cross section and a Dirac crossing at 0.28 × within the projected bulk band gap of tungsten. This state has eye-catching similarities to the spin-locked surface state of a topological insulator. The experiments are fortified by a one-step photoemission calculation in its density-matrix formulation.
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12
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Maaß H, Bentmann H, Seibel C, Tusche C, Eremeev SV, Peixoto TRF, Tereshchenko OE, Kokh KA, Chulkov EV, Kirschner J, Reinert F. Spin-texture inversion in the giant Rashba semiconductor BiTeI. Nat Commun 2016; 7:11621. [PMID: 27188584 PMCID: PMC4873970 DOI: 10.1038/ncomms11621] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Accepted: 04/14/2016] [Indexed: 11/24/2022] Open
Abstract
Semiconductors with strong spin-orbit interaction as the underlying mechanism for the generation of spin-polarized electrons are showing potential for applications in spintronic devices. Unveiling the full spin texture in momentum space for such materials and its relation to the microscopic structure of the electronic wave functions is experimentally challenging and yet essential for exploiting spin-orbit effects for spin manipulation. Here we employ a state-of-the-art photoelectron momentum microscope with a multichannel spin filter to directly image the spin texture of the layered polar semiconductor BiTeI within the full two-dimensional momentum plane. Our experimental results, supported by relativistic ab initio calculations, demonstrate that the valence and conduction band electrons in BiTeI have spin textures of opposite chirality and of pronounced orbital dependence beyond the standard Rashba model, the latter giving rise to strong optical selection-rule effects on the photoelectron spin polarization. These observations open avenues for spin-texture manipulation by atomic-layer and charge carrier control in polar semiconductors.
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Affiliation(s)
- Henriette Maaß
- Experimentelle Physik VII, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Hendrik Bentmann
- Experimentelle Physik VII, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Christoph Seibel
- Experimentelle Physik VII, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Christian Tusche
- Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, 06120 Halle, Germany
| | - Sergey V. Eremeev
- Institute of Strength Physics and Materials Science, 634055 Tomsk, Russia
- Tomsk State University, 634050 Tomsk, Russia
- Saint Petersburg State University, 198504 Saint Petersburg, Russia
| | - Thiago R. F. Peixoto
- Experimentelle Physik VII, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Oleg E. Tereshchenko
- Saint Petersburg State University, 198504 Saint Petersburg, Russia
- Institute of Semiconductor Physics, 636090 Novosibirsk, Russia
- Novosibirsk State University, 636090 Novosibirsk, Russia
| | - Konstantin A. Kokh
- Saint Petersburg State University, 198504 Saint Petersburg, Russia
- Novosibirsk State University, 636090 Novosibirsk, Russia
- Institute of Geology and Mineralogy, 630090 Novosibirsk, Russia
| | - Evgueni V. Chulkov
- Tomsk State University, 634050 Tomsk, Russia
- Saint Petersburg State University, 198504 Saint Petersburg, Russia
- Donostia International Physics Center (DIPC), 20018 San Sebastián/Donostia, Basque Country, Spain
- Departamento de Física de Materiales and Centro Mixto CSIC-UPV/EHU, Facultad de Ciencias Qumicas, Universidad del Pais Vasco/Euskal Herriko Unibertsitatea, Apdo. 1072, 20080 San Sebastián/Donostia, Basque Country, Spain
| | - Jürgen Kirschner
- Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, 06120 Halle, Germany
| | - Friedrich Reinert
- Experimentelle Physik VII, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
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Ellguth M, Tusche C, Kirschner J. Optical Generation of Hot Spin-Polarized Electrons from a Ferromagnetic Two-Dimensional Electron Gas. PHYSICAL REVIEW LETTERS 2015; 115:266801. [PMID: 26765012 DOI: 10.1103/physrevlett.115.266801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2015] [Indexed: 06/05/2023]
Abstract
Linearly polarized light with an energy of 3.1 eV has been used to excite highly spin-polarized electrons in an ultrathin film of face-centered-tetragonal cobalt to majority-spin quantum well states (QWS) derived from an sp band at the border of the Brillouin zone. The spin-selective excitation process has been studied by spin- and momentum-resolved two-photon photoemission. Analyzing the photoemission patterns in two-dimensional momentum planes, we find that the optically driven transition from the valence band to the QWS acts almost exclusively on majority-spin electrons. The mechanism providing the high spin polarization is discussed by the help of a density-functional theory calculation. Additionally, a sizable effect of spin-orbit coupling for the QWS is evidenced.
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Affiliation(s)
- Martin Ellguth
- Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, 06120 Halle, Germany
| | - Christian Tusche
- Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, 06120 Halle, Germany
| | - Jürgen Kirschner
- Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, 06120 Halle, Germany
- Institut für Physik, Martin-Luther-Universität Halle-Wittenberg, 06120 Halle, Germany
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14
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Tusche C, Krasyuk A, Kirschner J. Spin resolved bandstructure imaging with a high resolution momentum microscope. Ultramicroscopy 2015; 159 Pt 3:520-9. [DOI: 10.1016/j.ultramic.2015.03.020] [Citation(s) in RCA: 94] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2014] [Accepted: 03/22/2015] [Indexed: 10/23/2022]
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15
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Gotlieb K, Hussain Z, Bostwick A, Lanzara A, Jozwiak C. Rapid high-resolution spin- and angle-resolved photoemission spectroscopy with pulsed laser source and time-of-flight spectrometer. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2013; 84:093904. [PMID: 24089838 DOI: 10.1063/1.4821247] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
A high-efficiency spin- and angle-resolved photoemission spectroscopy (spin-ARPES) spectrometer is coupled with a laboratory-based laser for rapid high-resolution measurements. The spectrometer combines time-of-flight (TOF) energy measurements with low-energy exchange scattering spin polarimetry for high detection efficiencies. Samples are irradiated with fourth harmonic photons generated from a cavity-dumped Ti:sapphire laser that provides high photon flux in a narrow bandwidth, with a pulse timing structure ideally matched to the needs of the TOF spectrometer. The overall efficiency of the combined system results in near-E(F) spin-resolved ARPES measurements with an unprecedented combination of energy resolution and acquisition speed. This allows high-resolution spin measurements with a large number of data points spanning multiple dimensions of interest (energy, momentum, photon polarization, etc.) and thus enables experiments not otherwise possible. The system is demonstrated with spin-resolved energy and momentum mapping of the L-gap Au(111) surface states, a prototypical Rashba system. The successful integration of the spectrometer with the pulsed laser system demonstrates its potential for simultaneous spin- and time-resolved ARPES with pump-probe based measurements.
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Affiliation(s)
- K Gotlieb
- Graduate Group in Applied Science and Technology, University of California, Berkeley, California 94720, USA
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16
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Kutnyakhov D, Lushchyk P, Fognini A, Perriard D, Kolbe M, Medjanik K, Fedchenko E, Nepijko SA, Elmers HJ, Salvatella G, Stieger C, Gort R, Bähler T, Michlmayer T, Acremann Y, Vaterlaus A, Giebels F, Gollisch H, Feder R, Tusche C, Krasyuk A, Kirschner J, Schönhense G. Imaging spin filter for electrons based on specular reflection from iridium (001). Ultramicroscopy 2013; 130:63-9. [PMID: 23639852 DOI: 10.1016/j.ultramic.2013.03.017] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2012] [Revised: 03/15/2013] [Accepted: 03/18/2013] [Indexed: 11/18/2022]
Abstract
As Stern-Gerlach type spin filters do not work with electrons, spin analysis of electron beams is accomplished by spin-dependent scattering processes based on spin-orbit or exchange interaction. Existing polarimeters are single-channel devices characterized by an inherently low figure of merit (FoM) of typically 10⁻⁴-10⁻³. This single-channel approach is not compatible with parallel imaging microscopes and also not with modern electron spectrometers that acquire a certain energy and angular interval simultaneously. We present a novel type of polarimeter that can transport a full image by making use of k-parallel conservation in low-energy electron diffraction. We studied specular reflection from Ir (001) because this spin-filter crystal provides a high analyzing power combined with a "lifetime" in UHV of a full day. One good working point is centered at 39 eV scattering energy with a broad maximum of 5 eV usable width. A second one at about 10 eV shows a narrower profile but much higher FoM. A relativistic layer-KKR SPLEED calculation shows good agreement with measurements.
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Affiliation(s)
- D Kutnyakhov
- Johannes Gutenberg-Universität, Institut für Physik, 55099 Mainz, Germany
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