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Sunko V, Rosner H, Kushwaha P, Khim S, Mazzola F, Bawden L, Clark OJ, Riley JM, Kasinathan D, Haverkort MW, Kim TK, Hoesch M, Fujii J, Vobornik I, Mackenzie AP, King PDC. Maximal Rashba-like spin splitting via kinetic-energy-coupled inversion-symmetry breaking. Nature 2018; 549:492-496. [PMID: 28959958 DOI: 10.1038/nature23898] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Accepted: 07/26/2017] [Indexed: 11/09/2022]
Abstract
Engineering and enhancing the breaking of inversion symmetry in solids-that is, allowing electrons to differentiate between 'up' and 'down'-is a key goal in condensed-matter physics and materials science because it can be used to stabilize states that are of fundamental interest and also have potential practical applications. Examples include improved ferroelectrics for memory devices and materials that host Majorana zero modes for quantum computing. Although inversion symmetry is naturally broken in several crystalline environments, such as at surfaces and interfaces, maximizing the influence of this effect on the electronic states of interest remains a challenge. Here we present a mechanism for realizing a much larger coupling of inversion-symmetry breaking to itinerant surface electrons than is typically achieved. The key element is a pronounced asymmetry of surface hopping energies-that is, a kinetic-energy-coupled inversion-symmetry breaking, the energy scale of which is a substantial fraction of the bandwidth. Using spin- and angle-resolved photoemission spectroscopy, we demonstrate that such a strong inversion-symmetry breaking, when combined with spin-orbit interactions, can mediate Rashba-like spin splittings that are much larger than would typically be expected. The energy scale of the inversion-symmetry breaking that we achieve is so large that the spin splitting in the CoO2- and RhO2-derived surface states of delafossite oxides becomes controlled by the full atomic spin-orbit coupling of the 3d and 4d transition metals, resulting in some of the largest known Rashba-like spin splittings. The core structural building blocks that facilitate the bandwidth-scaled inversion-symmetry breaking are common to numerous materials. Our findings therefore provide opportunities for creating spin-textured states and suggest routes to interfacial control of inversion-symmetry breaking in designer heterostructures of oxides and other material classes.
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Affiliation(s)
- Veronika Sunko
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews KY16 9SS, UK.,Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany
| | - H Rosner
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany
| | - P Kushwaha
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany
| | - S Khim
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany
| | - F Mazzola
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews KY16 9SS, UK
| | - L Bawden
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews KY16 9SS, UK
| | - O J Clark
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews KY16 9SS, UK
| | - J M Riley
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews KY16 9SS, UK.,Diamond Light Source, Harwell Campus, Didcot OX11 0DE, UK
| | - D Kasinathan
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany
| | - M W Haverkort
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany.,Institute for Theoretical Physics, Heidelberg University, Philosophenweg 19, 69120 Heidelberg, Germany
| | - T K Kim
- Diamond Light Source, Harwell Campus, Didcot OX11 0DE, UK
| | - M Hoesch
- Diamond Light Source, Harwell Campus, Didcot OX11 0DE, UK
| | - J Fujii
- Istituto Officina dei Materiali (IOM)-CNR, Laboratorio TASC, Area Science Park, S.S.14, Km 163.5, 34149 Trieste, Italy
| | - I Vobornik
- Istituto Officina dei Materiali (IOM)-CNR, Laboratorio TASC, Area Science Park, S.S.14, Km 163.5, 34149 Trieste, Italy
| | - A P Mackenzie
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews KY16 9SS, UK.,Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany
| | - P D C King
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews KY16 9SS, UK
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Sundermann M, Yavaş H, Chen K, Kim DJ, Fisk Z, Kasinathan D, Haverkort MW, Thalmeier P, Severing A, Tjeng LH. 4f Crystal Field Ground State of the Strongly Correlated Topological Insulator SmB_{6}. Phys Rev Lett 2018; 120:016402. [PMID: 29350947 DOI: 10.1103/physrevlett.120.016402] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/20/2017] [Revised: 09/25/2017] [Indexed: 06/07/2023]
Abstract
We investigated the crystal-electric field ground state of the 4f manifold in the strongly correlated topological insulator SmB_{6} using core-level nonresonant inelastic x-ray scattering. The directional dependence of the scattering function that arises from higher multipole transitions establishes unambiguously that the Γ_{8} quartet state of the Sm f^{5} J=5/2 configuration governs the ground-state symmetry and, hence, the topological properties of SmB_{6}. Our findings contradict the results of density functional calculations reported so far.
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Affiliation(s)
- M Sundermann
- Institute of Physics II, University of Cologne, Zülpicher Straße 77, 50937 Cologne, Germany
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany
| | - H Yavaş
- PETRA III, Deutsches Elektronen-Synchrotron (DESY), Notkestraße 85, 22607 Hamburg, Germany
| | - K Chen
- Institute of Physics II, University of Cologne, Zülpicher Straße 77, 50937 Cologne, Germany
| | - D J Kim
- Department of Physics and Astronomy, University of California, Irvine, California 92697, USA
| | - Z Fisk
- Department of Physics and Astronomy, University of California, Irvine, California 92697, USA
| | - D Kasinathan
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany
| | - M W Haverkort
- Institute for Theoretical Physics, Heidelberg University, Philosophenweg 19, 69120 Heidelberg, Germany
| | - P Thalmeier
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany
| | - A Severing
- Institute of Physics II, University of Cologne, Zülpicher Straße 77, 50937 Cologne, Germany
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany
| | - L H Tjeng
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany
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Mydeen K, Kasinathan D, Koz C, Rößler S, Rößler UK, Hanfland M, Tsirlin AA, Schwarz U, Wirth S, Rosner H, Nicklas M. Pressure-Induced Ferromagnetism due to an Anisotropic Electronic Topological Transition in Fe_{1.08}Te. Phys Rev Lett 2017; 119:227003. [PMID: 29286759 DOI: 10.1103/physrevlett.119.227003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2017] [Indexed: 06/07/2023]
Abstract
A rapid and anisotropic modification of the Fermi-surface shape can be associated with abrupt changes in crystalline lattice geometry or in the magnetic state of a material. We show that such an electronic topological transition is at the basis of the formation of an unusual pressure-induced tetragonal ferromagnetic phase in Fe_{1.08}Te. Around 2 GPa, the orthorhombic and incommensurate antiferromagnetic ground state of Fe_{1.08}Te is transformed upon increasing pressure into a tetragonal ferromagnetic state via a conventional first-order transition. On the other hand, an isostructural transition takes place from the paramagnetic high-temperature state into the ferromagnetic phase as a rare case of a "type-0" transformation with anisotropic properties. Electronic-structure calculations in combination with electrical resistivity, magnetization, and x-ray diffraction experiments show that the electronic system of Fe_{1.08}Te is instable with respect to profound topological transitions that can drive fundamental changes of the lattice anisotropy and the associated magnetic order.
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Affiliation(s)
- K Mydeen
- Max-Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany
| | - D Kasinathan
- Max-Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany
| | - C Koz
- Max-Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany
| | - S Rößler
- Max-Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany
| | - U K Rößler
- Leibniz-Institut für Festkörper- und Werkstoffforschung IFW, Helmholtz Straße 20, 01171 Dresden, Germany
| | - M Hanfland
- ESRF, BP 220, F-38043 Grenoble Cedex 9, France
| | - A A Tsirlin
- Experimental Physics VI, Center for Electronic Correlations and Magnetism, Institute of Physics, University of Augsburg, 86135 Augsburg, Germany
| | - U Schwarz
- Max-Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany
| | - S Wirth
- Max-Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany
| | - H Rosner
- Max-Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany
| | - M Nicklas
- Max-Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany
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Pogrebnyakov AV, Redwing JM, Raghavan S, Vaithyanathan V, Schlom DG, Xu SY, Li Q, Tenne DA, Soukiassian A, Xi XX, Johannes MD, Kasinathan D, Pickett WE, Wu JS, Spence JCH. Enhancement of the superconducting transition temperature of MgB2 by a strain-induced bond-stretching mode softening. Phys Rev Lett 2004; 93:147006. [PMID: 15524834 DOI: 10.1103/physrevlett.93.147006] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2004] [Indexed: 05/24/2023]
Abstract
We report a systematic increase of the superconducting transition temperature T(c) with a biaxial tensile strain in MgB2 films to well beyond the bulk value. The tensile strain increases with the MgB2 film thickness, caused primarily by the coalescence of initially nucleated discrete islands (the Volmer-Weber growth mode.) The T(c) increase was observed in epitaxial films on SiC and sapphire substrates, although the T(c) values were different for the two substrates due to different lattice parameters and thermal expansion coefficients. We identified, by first-principles calculations, the underlying mechanism for the T(c) increase to be the softening of the bond-stretching E(2g) phonon mode, and we confirmed this conclusion by Raman scattering measurements. The result suggests that the E(2g) phonon softening is a possible avenue to achieve even higher T(c) in MgB2-related material systems.
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Affiliation(s)
- A V Pogrebnyakov
- Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
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