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Krasovskii EE. Spin-orbit coupling at surfaces and 2D materials. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:493001. [PMID: 26580290 DOI: 10.1088/0953-8984/27/49/493001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Spin-orbit interaction gives rise to a splitting of surface states via the Rashba effect, and in topological insulators it leads to the existence of topological surface states. The resulting k(//) momentum separation between states with the opposite spin underlies a wide range of new phenomena at surfaces and interfaces, such as spin transfer, spin accumulation, spin-to-charge current conversion, which are interesting for fundamental science and may become the basis for a breakthrough in the spintronic technology. The present review summarizes recent theoretical and experimental efforts to reveal the microscopic structure and mechanisms of spin-orbit driven phenomena with the focus on angle and spin-resolved photoemission and scanning tunneling microscopy.
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Affiliation(s)
- E E Krasovskii
- Departamento de Física de Materiales, Universidad del Pais Vasco UPV/EHU, 20080 San Sebastián/Donostia, Spain. Donostia International Physics Center (DIPC), 20018 San Sebastián/Donostia, Spain. IKERBASQUE, Basque Foundation for Science, 48013 Bilbao, Spain
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2
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Gambardella P, Miron IM. Current-induced spin-orbit torques. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2011; 369:3175-3197. [PMID: 21727120 DOI: 10.1098/rsta.2010.0336] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The ability to reverse the magnetization of nanomagnets by current injection has attracted increased attention ever since the spin-transfer torque mechanism was predicted in 1996. In this paper, we review the basic theoretical and experimental arguments supporting a novel current-induced spin torque mechanism taking place in ferromagnetic (FM) materials. This effect, hereafter named spin-orbit (SO) torque, is produced by the flow of an electric current in a crystalline structure lacking inversion symmetry, which transfers orbital angular momentum from the lattice to the spin system owing to the combined action of SO and exchange coupling. SO torques are found to be prominent in both FM metal and semiconducting systems, allowing for great flexibility in adjusting their orientation and magnitude by proper material engineering. Further directions of research in this field are briefly outlined.
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Affiliation(s)
- Pietro Gambardella
- Institut Catalá de Nanotecnologia, Centre d'Investigaciò en Nanociència i Nanotecnologia (ICN-CIN2), UAB Campus, 08193 Barcelona, Spain.
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Dil JH. Spin and angle resolved photoemission on non-magnetic low-dimensional systems. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2009; 21:403001. [PMID: 21832402 DOI: 10.1088/0953-8984/21/40/403001] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The electronic structure of non-magnetic low-dimensional materials can acquire a spin structure due to the breaking of the inversion symmetry at the surface or interface. This so-called Rashba effect is a prime candidate for the manipulation of the electron spin without using any magnetic fields. This is crucial for the emerging field of spintronics, where the spin of the electron instead of its charge is used to transport or store information. Spin and angle resolved photoemission is currently one of the main experimental methods to measure the spin resolved electronic structure, which contains all the relevant information for spintronics. In this review, the technique of spin and angle resolved photoemission will be explained and recent results on low-dimensional non-magnetic structures will be discussed.
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Affiliation(s)
- J Hugo Dil
- Physik-Institut, Universität Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland. Swiss Light Source, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland
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Dil JH, Meier F, Lobo-Checa J, Patthey L, Bihlmayer G, Osterwalder J. Rashba-type spin-orbit splitting of quantum well states in ultrathin Pb films. PHYSICAL REVIEW LETTERS 2008; 101:266802. [PMID: 19113782 DOI: 10.1103/physrevlett.101.266802] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2008] [Indexed: 05/27/2023]
Abstract
A Rashba-type spin-orbit splitting is found for quantum well states formed in ultrathin Pb films on Si (111). The resulting momentum splitting is comparable to what is found for semiconductor heterostructures. The splitting shows no coverage dependency and the sign of the spin polarization is reversed compared to Rashba splitting in the Au(111) surface state. We explain our results by competing effects at the two boundaries of the Pb layer.
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Affiliation(s)
- J Hugo Dil
- Physik-Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
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5
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Varykhalov A, Sánchez-Barriga J, Shikin AM, Gudat W, Eberhardt W, Rader O. Quantum cavity for spin due to spin-orbit interaction at a metal boundary. PHYSICAL REVIEW LETTERS 2008; 101:256601. [PMID: 19113734 DOI: 10.1103/physrevlett.101.256601] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2008] [Indexed: 05/27/2023]
Abstract
A quantum cavity for spin is created using a tungsten crystal as substrate of high nuclear charge and breaking the structural inversion symmetry through deposition of a gold quantum film. Spin- and angle-resolved photoelectron spectroscopy shows directly that quantum-well states and the "matrioshka" or Russian nested doll Fermi surface of the gold film are spin polarized and spin-orbit split up to a thickness of at least nine atomic layers. Ferromagnetic materials or external magnetic fields are not required, and the quantum film does not need to possess a high atomic number as analogous results with silver show.
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Affiliation(s)
- A Varykhalov
- Helmholtz-Zentrum für Materialien und Energie, Elektronenspeicherring BESSY II, Albert-Einstein-Strasse 15, D-12489 Berlin, Germany
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He K, Hirahara T, Okuda T, Hasegawa S, Kakizaki A, Matsuda I. Spin polarization of quantum well states in Ag films induced by the Rashba effect at the surface. PHYSICAL REVIEW LETTERS 2008; 101:107604. [PMID: 18851258 DOI: 10.1103/physrevlett.101.107604] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2008] [Indexed: 05/26/2023]
Abstract
The electronic structure of Ag(111) quantum well films covered with a (sqrt[3]xsqrt[3]) R30 degrees Bi/Ag surface ordered alloy, which shows a Rashba spin-split surface state, is investigated with angle-resolved photoemission spectroscopy. The band dispersion of the spin-split surface state is significantly modified by the interaction with the quantum well states of Ag films. The interaction is well described by the band hybridization model, which concludes the spin polarization of the quantum well states.
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Affiliation(s)
- Ke He
- Institute for Solid State Physics (ISSP), the University of Tokyo, 5-1-5 Kashiwanoha, Chiba 277-8581, Japan
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Shikin AM, Varykhalov A, Prudnikova GV, Usachov D, Adamchuk VK, Yamada Y, Riley JD, Rader O. Origin of spin-orbit splitting for monolayers of au and ag on w(110) and mo(110). PHYSICAL REVIEW LETTERS 2008; 100:057601. [PMID: 18352430 DOI: 10.1103/physrevlett.100.057601] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/03/2007] [Indexed: 05/26/2023]
Abstract
Spin-orbit coupling can give rise to spin-split electronic states without a ferromagnet or an external magnetic field. We create large spin-orbit splittings in a Au and Ag monolayer on W(110) and show that the size of the splitting does not depend on the atomic number of the Au or Ag overlayer but of the W substrate. Spin- and angle-resolved photoemission and Fermi-surface scans reveal that the overlayer states acquire spin polarization through spin-dependent overlayer-substrate hybridization.
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Affiliation(s)
- A M Shikin
- Institute of Physics, St. Petersburg State University, St. Petersburg, 198504, Russia
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Moras P, Ferrari L, Spezzani C, Gardonio S, Lezaić M, Mavropoulos P, Blügel S, Carbone C. Probing quasiparticle states bound by disparate periodic potentials. PHYSICAL REVIEW LETTERS 2006; 97:206802. [PMID: 17155702 DOI: 10.1103/physrevlett.97.206802] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2006] [Indexed: 05/12/2023]
Abstract
Thin films of Ag(111) with two-dimensional crystallinity of large lateral coherence grow on Ge(111), free of in-plane registry with the underlying substrate. Ag s-p electrons forming two-dimensional quantum well states scatter coherently at the buried interface potential, resulting in an unexpected set of new quasiparticle states, as observed by angle-resolved photoemission. These new features originate from interactions among Ag quantum well bands, gaining a momentum equivalent to a reciprocal vector of the substrate lattice.
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Affiliation(s)
- P Moras
- Istituto di Struttura della Materia, Consiglio Nazionale delle Ricerche, Trieste, Italy
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Chulkov EV, Borisov AG, Gauyacq JP, Sanchez-Portal D, Silkin VM, Zhukov VP, Echenique PM. Electronic Excitations in Metals and at Metal Surfaces. Chem Rev 2006; 106:4160-206. [PMID: 17031983 DOI: 10.1021/cr050166o] [Citation(s) in RCA: 208] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- E V Chulkov
- Departamento de Física de Materiales and Centro Mixto CSIC-UPV/EHU, Facultad de Ciencias Químicas, Universidad del País Vasco UPV/EHU, Apdo. 1072, 20080 San Sebastian/Donostia, Basque Country, Spain.
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Schiller F, Keyling R, Chulkov EV, Ortega JE. Surface state scattering at a buried interface. PHYSICAL REVIEW LETTERS 2005; 95:126402. [PMID: 16197091 DOI: 10.1103/physrevlett.95.126402] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/05/2004] [Indexed: 05/04/2023]
Abstract
The free-electron-like surface state of Mg(0001) is strongly modified in thin films grown on W(110). The long bulk penetration length of its wave function makes it sensitive to the reflective properties of the buried interface, and hence to the complex electronic structure of the substrate. In particular we find a many-fold splitting of the Mg surface band by entering a wide projected band gap of W(110). There is a strong thickness-dependent two-band splitting, which is a clear signature of the formation of a surface-interface resonant state. An additional split-off from these two surface bands is explained by the substrate induced spin-orbit interaction.
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Affiliation(s)
- F Schiller
- Donostia International Physics Center, Paseo Manuel Lardizabal 4, E-20018 San Sebastián, Spain
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