1
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Caputo M, Studniarek M, Guedes EB, Schio L, Baiseitov K, Daffé N, Bachellier N, Chikina A, Di Santo G, Verdini A, Goldoni A, Muntwiler M, Piamonteze C, Floreano L, Radovic M, Dreiser J. Charge Transfer and Orbital Reconstruction at an Organic-Oxide Interface. Nano Lett 2023. [PMID: 38029285 DOI: 10.1021/acs.nanolett.3c03713] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/01/2023]
Abstract
The two-dimensional electron system (2DES) located at the surface of strontium titanate (STO) and at several other STO-based interfaces has been an established platform for the study of novel physical phenomena since its discovery. Here we report how the interfacing of STO and tetracyanoquinodimethane (TCNQ) results in a charge transfer that depletes the number of free carriers at the STO surface, with a strong impact on its electronic structure. Our study paves the way for efficient tuning of the electronic properties, which promises novel applications in the framework of oxide/organic-based electronics.
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Affiliation(s)
- Marco Caputo
- Elettra Sincrotrone Trieste, s.s. 14 km 163.5 in Area Science Park, 34149 Trieste, Italy
- MAX IV Laboratory, Lund University, PO Box 118, 22100 Lund, Sweden
| | - Michał Studniarek
- Swiss Light Source, Paul Scherrer Institut, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
| | - Eduardo Bonini Guedes
- Swiss Light Source, Paul Scherrer Institut, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
| | - Luca Schio
- Laboratorio TASC, Istituto Officina dei Materiali (IOM)-CNR, Area Science Park, S.S. 14 km 163.5, 34149 Trieste, Italy
| | - Kassymkhan Baiseitov
- Swiss Light Source, Paul Scherrer Institut, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
| | - Niéli Daffé
- Swiss Light Source, Paul Scherrer Institut, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
| | - Nicolas Bachellier
- Swiss Light Source, Paul Scherrer Institut, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
| | - Alla Chikina
- Swiss Light Source, Paul Scherrer Institut, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
| | - Giovanni Di Santo
- Elettra Sincrotrone Trieste, s.s. 14 km 163.5 in Area Science Park, 34149 Trieste, Italy
| | - Alberto Verdini
- Laboratorio TASC, Istituto Officina dei Materiali (IOM)-CNR, Area Science Park, S.S. 14 km 163.5, 34149 Trieste, Italy
| | - Andrea Goldoni
- Elettra Sincrotrone Trieste, s.s. 14 km 163.5 in Area Science Park, 34149 Trieste, Italy
| | - Matthias Muntwiler
- Swiss Light Source, Paul Scherrer Institut, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
| | - Cinthia Piamonteze
- Swiss Light Source, Paul Scherrer Institut, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
| | - Luca Floreano
- Laboratorio TASC, Istituto Officina dei Materiali (IOM)-CNR, Area Science Park, S.S. 14 km 163.5, 34149 Trieste, Italy
| | - Milan Radovic
- Swiss Light Source, Paul Scherrer Institut, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
| | - Jan Dreiser
- Swiss Light Source, Paul Scherrer Institut, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
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2
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Cochran TA, Belopolski I, Manna K, Yahyavi M, Liu Y, Sanchez DS, Cheng ZJ, Yang XP, Multer D, Yin JX, Borrmann H, Chikina A, Krieger JA, Sánchez-Barriga J, Le Fèvre P, Bertran F, Strocov VN, Denlinger JD, Chang TR, Jia S, Felser C, Lin H, Chang G, Hasan MZ. Visualizing Higher-Fold Topology in Chiral Crystals. Phys Rev Lett 2023; 130:066402. [PMID: 36827563 DOI: 10.1103/physrevlett.130.066402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2021] [Revised: 01/18/2022] [Accepted: 12/14/2022] [Indexed: 06/18/2023]
Abstract
Novel topological phases of matter are fruitful platforms for the discovery of unconventional electromagnetic phenomena. Higher-fold topology is one example, where the low-energy description goes beyond standard model analogs. Despite intensive experimental studies, conclusive evidence remains elusive for the multigap topological nature of higher-fold chiral fermions. In this Letter, we leverage a combination of fine-tuned chemical engineering and photoemission spectroscopy with photon energy contrast to discover the higher-fold topology of a chiral crystal. We identify all bulk branches of a higher-fold chiral fermion for the first time, critically important for allowing us to explore unique Fermi arc surface states in multiple interband gaps, which exhibit an emergent ladder structure. Through designer chemical gating of the samples in combination with our measurements, we uncover an unprecedented multigap bulk boundary correspondence. Our demonstration of multigap electronic topology will propel future research on unconventional topological responses.
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Affiliation(s)
- Tyler A Cochran
- Laboratory for Topological Quantum Matter and Advanced Spectroscopy (B7), Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
| | - Ilya Belopolski
- Laboratory for Topological Quantum Matter and Advanced Spectroscopy (B7), Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
| | - Kaustuv Manna
- Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany
- Department of Physics, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
| | - Mohammad Yahyavi
- Department of Physics, National Cheng Kung University, Tainan 70101, Taiwan
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link 637371, Singapore
| | - Yiyuan Liu
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Daniel S Sanchez
- Laboratory for Topological Quantum Matter and Advanced Spectroscopy (B7), Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
| | - Zi-Jia Cheng
- Laboratory for Topological Quantum Matter and Advanced Spectroscopy (B7), Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
| | - Xian P Yang
- Laboratory for Topological Quantum Matter and Advanced Spectroscopy (B7), Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
| | - Daniel Multer
- Laboratory for Topological Quantum Matter and Advanced Spectroscopy (B7), Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
| | - Jia-Xin Yin
- Laboratory for Topological Quantum Matter and Advanced Spectroscopy (B7), Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
| | - Horst Borrmann
- Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany
| | - Alla Chikina
- Swiss Light Source, Paul Scherrer Institute, 5232 Villigen, Switzerland
| | - Jonas A Krieger
- Swiss Light Source, Paul Scherrer Institute, 5232 Villigen, Switzerland
- Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, 5232 Villigen, Switzerland
| | - Jaime Sánchez-Barriga
- Helmholtz-Zentrum Berlin für Materialien und Energie, Elektronenspeicherring BESSY II, Albert-Einstein Strasse 15, 12489 Berlin, Germany
- IMDEA Nanoscience, C/ Faraday 9, Campus de Cantoblanco, 28049 Madrid, Spain
| | - Patrick Le Fèvre
- SOLEIL Synchrotron, L'Orme des Merisiers, Départementale 128, F-91190 Saint-Aubin, France
| | - François Bertran
- SOLEIL Synchrotron, L'Orme des Merisiers, Départementale 128, F-91190 Saint-Aubin, France
| | | | - Jonathan D Denlinger
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Tay-Rong Chang
- Department of Physics, National Cheng Kung University, Tainan 70101, Taiwan
| | - Shuang Jia
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link 637371, Singapore
| | - Claudia Felser
- Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany
| | - Hsin Lin
- Institute of Physics, Academia Sinica, Taipei 11529, Taiwan
| | - Guoqing Chang
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link 637371, Singapore
| | - M Zahid Hasan
- Laboratory for Topological Quantum Matter and Advanced Spectroscopy (B7), Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
- Princeton Institute for Science and Technology of Materials, Princeton University, Princeton, New Jersey 08544, USA
- Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
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3
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Voroshnin V, Tarasov AV, Bokai KA, Chikina A, Senkovskiy BV, Ehlen N, Usachov DY, Grüneis A, Krivenkov M, Sánchez-Barriga J, Fedorov A. Direct Spectroscopic Evidence of Magnetic Proximity Effect in MoS 2 Monolayer on Graphene/Co. ACS Nano 2022; 16:7448-7456. [PMID: 35442015 DOI: 10.1021/acsnano.1c10391] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
A magnetic field modifies optical properties and provides valley splitting in a molybdenum disulfide (MoS2) monolayer. Here we demonstrate a scalable approach to the epitaxial synthesis of MoS2 monolayer on a magnetic graphene/Co system. Using spin- and angle-resolved photoemission spectroscopy we observe a magnetic proximity effect that causes a 20 meV spin-splitting at the Γ̅ point and canting of spins at the K̅ point in the valence band toward the in-plane direction of cobalt magnetization. Our density functional theory calculations reveal that the in-plane spin component at K̅ is localized on Co atoms in the valence band, while in the conduction band it is localized on the MoS2 layer. The calculations also predict a 16 meV spin-splitting at the Γ̅ point and 8 meV K̅-K'¯ valley asymmetry for an out-of-plane magnetization. These findings suggest control over optical transitions in MoS2 via Co magnetization. Our estimations show that the magnetic proximity effect is equivalent to the action of the magnetic field as large as 100 T.
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Affiliation(s)
- Vladimir Voroshnin
- Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Strasse 24/25, Potsdam 14476, Germany
| | - Artem V Tarasov
- St. Petersburg State University, St. Petersburg 198504, Russia
| | - Kirill A Bokai
- St. Petersburg State University, St. Petersburg 198504, Russia
| | - Alla Chikina
- Paul Scherrer Institute, Forschungsstrasse 111, Villigen PSI 5232, Switzerland
| | - Boris V Senkovskiy
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Strasse 77, Köln 50937, Germany
| | - Niels Ehlen
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Strasse 77, Köln 50937, Germany
| | | | - Alexander Grüneis
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Strasse 77, Köln 50937, Germany
| | - Maxim Krivenkov
- Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin 12489, Germany
| | | | - Alexander Fedorov
- IFW Dresden, Leibniz Institute for Solid State and Materials Research, D-01171, Dresden 01069, Germany
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4
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Belopolski I, Chang G, Cochran TA, Cheng ZJ, Yang XP, Hugelmeyer C, Manna K, Yin JX, Cheng G, Multer D, Litskevich M, Shumiya N, Zhang SS, Shekhar C, Schröter NBM, Chikina A, Polley C, Thiagarajan B, Leandersson M, Adell J, Huang SM, Yao N, Strocov VN, Felser C, Hasan MZ. Observation of a linked-loop quantum state in a topological magnet. Nature 2022; 604:647-652. [PMID: 35478239 DOI: 10.1038/s41586-022-04512-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2020] [Accepted: 02/03/2022] [Indexed: 11/09/2022]
Abstract
Quantum phases can be classified by topological invariants, which take on discrete values capturing global information about the quantum state1-13. Over the past decades, these invariants have come to play a central role in describing matter, providing the foundation for understanding superfluids5, magnets6,7, the quantum Hall effect3,8, topological insulators9,10, Weyl semimetals11-13 and other phenomena. Here we report an unusual linking-number (knot theory) invariant associated with loops of electronic band crossings in a mirror-symmetric ferromagnet14-20. Using state-of-the-art spectroscopic methods, we directly observe three intertwined degeneracy loops in the material's three-torus, T3, bulk Brillouin zone. We find that each loop links each other loop twice. Through systematic spectroscopic investigation of this linked-loop quantum state, we explicitly draw its link diagram and conclude, in analogy with knot theory, that it exhibits the linking number (2, 2, 2), providing a direct determination of the invariant structure from the experimental data. We further predict and observe, on the surface of our samples, Seifert boundary states protected by the bulk linked loops, suggestive of a remarkable Seifert bulk-boundary correspondence. Our observation of a quantum loop link motivates the application of knot theory to the exploration of magnetic and superconducting quantum matter.
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Affiliation(s)
- Ilya Belopolski
- Laboratory for Topological Quantum Matter and Spectroscopy, Department of Physics, Princeton University, Princeton, NJ, USA. .,RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama, Japan.
| | - Guoqing Chang
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, Singapore
| | - Tyler A Cochran
- Laboratory for Topological Quantum Matter and Spectroscopy, Department of Physics, Princeton University, Princeton, NJ, USA
| | - Zi-Jia Cheng
- Laboratory for Topological Quantum Matter and Spectroscopy, Department of Physics, Princeton University, Princeton, NJ, USA
| | - Xian P Yang
- Laboratory for Topological Quantum Matter and Spectroscopy, Department of Physics, Princeton University, Princeton, NJ, USA
| | - Cole Hugelmeyer
- Department of Mathematics, Princeton University, Princeton, NJ, USA
| | - Kaustuv Manna
- Max Planck Institute for Chemical Physics of Solids, Dresden, Germany.,Department of Physics, Indian Institute of Technology Delhi, New Delhi, India
| | - Jia-Xin Yin
- Laboratory for Topological Quantum Matter and Spectroscopy, Department of Physics, Princeton University, Princeton, NJ, USA
| | - Guangming Cheng
- Princeton Institute for Science and Technology of Materials, Princeton University, Princeton, NJ, USA
| | - Daniel Multer
- Laboratory for Topological Quantum Matter and Spectroscopy, Department of Physics, Princeton University, Princeton, NJ, USA
| | - Maksim Litskevich
- Laboratory for Topological Quantum Matter and Spectroscopy, Department of Physics, Princeton University, Princeton, NJ, USA
| | - Nana Shumiya
- Laboratory for Topological Quantum Matter and Spectroscopy, Department of Physics, Princeton University, Princeton, NJ, USA
| | - Songtian S Zhang
- Laboratory for Topological Quantum Matter and Spectroscopy, Department of Physics, Princeton University, Princeton, NJ, USA
| | - Chandra Shekhar
- Max Planck Institute for Chemical Physics of Solids, Dresden, Germany
| | | | - Alla Chikina
- Swiss Light Source, Paul Scherrer Institut, Villigen, Switzerland
| | - Craig Polley
- MAX IV Laboratory, Lund University, Lund, Sweden
| | | | | | - Johan Adell
- MAX IV Laboratory, Lund University, Lund, Sweden
| | - Shin-Ming Huang
- Department of Physics, National Sun Yat-sen University, Kaohsiung City, Taiwan
| | - Nan Yao
- Princeton Institute for Science and Technology of Materials, Princeton University, Princeton, NJ, USA
| | | | - Claudia Felser
- Max Planck Institute for Chemical Physics of Solids, Dresden, Germany
| | - M Zahid Hasan
- Laboratory for Topological Quantum Matter and Spectroscopy, Department of Physics, Princeton University, Princeton, NJ, USA. .,Princeton Institute for Science and Technology of Materials, Princeton University, Princeton, NJ, USA. .,Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA. .,Quantum Science Center, Oak Ridge, TN, USA.
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5
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Dreher P, Wan W, Chikina A, Bianchi M, Guo H, Harsh R, Mañas-Valero S, Coronado E, Martínez-Galera AJ, Hofmann P, Miwa JA, Ugeda MM. Proximity Effects on the Charge Density Wave Order and Superconductivity in Single-Layer NbSe 2. ACS Nano 2021; 15:19430-19438. [PMID: 34846856 PMCID: PMC8717633 DOI: 10.1021/acsnano.1c06012] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2021] [Accepted: 11/05/2021] [Indexed: 06/10/2023]
Abstract
Collective electronic states such as the charge density wave (CDW) order and superconductivity (SC) respond sensitively to external perturbations. Such sensitivity is dramatically enhanced in two dimensions (2D), where 2D materials hosting such electronic states are largely exposed to the environment. In this regard, the ineludible presence of supporting substrates triggers various proximity effects on 2D materials that may ultimately compromise the stability and properties of the electronic ground state. In this work, we investigate the impact of proximity effects on the CDW and superconducting states in single-layer (SL) NbSe2 on four substrates of diverse nature, namely, bilayer graphene (BLG), SL-boron nitride (h-BN), Au(111), and bulk WSe2. By combining low-temperature (340 mK) scanning tunneling microscopy/spectroscopy and angle-resolved photoemission spectroscopy, we compare the electronic structure of this prototypical 2D superconductor on each substrate. We find that, even when the electronic band structure of SL-NbSe2 remains largely unaffected by the substrate except when placed on Au(111), where a charge transfer occurs, both the CDW and SC show disparate behaviors. On the insulating h-BN/Ir(111) substrate and the metallic BLG/SiC(0001) substrate, both the 3 × 3 CDW and superconducting phases persist in SL-NbSe2 with very similar properties, which reveals the negligible impact of graphene on these electronic phases. In contrast, these collective electronic phases are severely weakened and even absent on the bulk insulating WSe2 substrate and the metallic single-crystal Au(111) substrate. Our results provide valuable insights into the fragile stability of such electronic ground states in 2D materials.
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Affiliation(s)
- Paul Dreher
- Donostia
International Physics Center (DIPC), Paseo Manuel de Lardizábal 4, 20018 San Sebastián, Spain
| | - Wen Wan
- Donostia
International Physics Center (DIPC), Paseo Manuel de Lardizábal 4, 20018 San Sebastián, Spain
| | - Alla Chikina
- Department
of Physics and Astronomy, Interdisciplinary Nanoscience Center, Aarhus University, 8000 Aarhus C, Denmark
| | - Marco Bianchi
- Department
of Physics and Astronomy, Interdisciplinary Nanoscience Center, Aarhus University, 8000 Aarhus C, Denmark
| | - Haojie Guo
- Departamento
de Física de la Materia Condensada, Universidad Autonoma de Madrid, Madrid E-28049, Spain
| | - Rishav Harsh
- Donostia
International Physics Center (DIPC), Paseo Manuel de Lardizábal 4, 20018 San Sebastián, Spain
| | - Samuel Mañas-Valero
- Instituto
de Ciencia Molecular (ICMol), Universitat
de València, c/
Catedrático José Beltrán 2, 46980 Paterna, Spain
| | - Eugenio Coronado
- Instituto
de Ciencia Molecular (ICMol), Universitat
de València, c/
Catedrático José Beltrán 2, 46980 Paterna, Spain
| | - Antonio J. Martínez-Galera
- Departamento
de Física de la Materia Condensada, Universidad Autonoma de Madrid, Madrid E-28049, Spain
- Insitituto
Nicolás Cabrera, Universidad Autnoma
de Madrid, Madrid E-28049, Spain
| | - Philip Hofmann
- Department
of Physics and Astronomy, Interdisciplinary Nanoscience Center, Aarhus University, 8000 Aarhus C, Denmark
| | - Jill A. Miwa
- Department
of Physics and Astronomy, Interdisciplinary Nanoscience Center, Aarhus University, 8000 Aarhus C, Denmark
| | - Miguel M. Ugeda
- Donostia
International Physics Center (DIPC), Paseo Manuel de Lardizábal 4, 20018 San Sebastián, Spain
- Centro
de Física de Materiales (CSIC-UPV-EHU), Paseo Manuel de Lardizábal 5, 20018 San Sebastián, Spain
- Ikerbasque,
Basque Foundation for Science, 48013 Bilbao, Spain
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6
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Chikina A, Christensen DV, Borisov V, Husanu MA, Chen Y, Wang X, Schmitt T, Radovic M, Nagaosa N, Mishchenko AS, Valentí R, Pryds N, Strocov VN. Band-Order Anomaly at the γ-Al 2O 3/SrTiO 3 Interface Drives the Electron-Mobility Boost. ACS Nano 2021; 15:4347-4356. [PMID: 33661601 DOI: 10.1021/acsnano.0c07609] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The rich functionalities of transition-metal oxides and their interfaces bear an enormous technological potential. Its realization in practical devices requires, however, a significant improvement of yet relatively low electron mobility in oxide materials. Recently, a mobility boost of about 2 orders of magnitude has been demonstrated at the spinel-perovskite γ-Al2O3/SrTiO3 interface compared to the paradigm perovskite-perovskite LaAlO3/SrTiO3 interface. We explore the fundamental physics behind this phenomenon from direct measurements of the momentum-resolved electronic structure of this interface using resonant soft-X-ray angle-resolved photoemission. We find an anomaly in orbital ordering of the mobile electrons in γ-Al2O3/SrTiO3 which depopulates electron states in the top SrTiO3 layer. This rearrangement of the mobile electron system pushes the electron density away from the interface, which reduces its overlap with the interfacial defects and weakens the electron-phonon interaction, both effects contributing to the mobility boost. A crystal-field analysis shows that the band order alters owing to the symmetry breaking between the spinel γ-Al2O3 and perovskite SrTiO3. Band-order engineering, exploiting the fundamental symmetry properties, emerges as another route to boost the performance of oxide devices.
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Affiliation(s)
- Alla Chikina
- Swiss Light Source, Paul Scherrer Institute, 5232 Villigen-PSI, Switzerland
- Institute of Physics and Astronomy, Aarhus University, Ny Munkegade 120, 8000 Aarhus, Denmark
| | - Dennis V Christensen
- Department of Energy Conversion and Storage, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
| | - Vladislav Borisov
- Institut für Theoretische Physik, Goethe-Universität Frankfurt am Main, Max-von-Laue-Strasse 1, 60438 Frankfurt am Main, Germany
- Department of Physics and Astronomy, Uppsala University, Box 516, 5120 Uppsala, Sweden
| | - Marius-Adrian Husanu
- Swiss Light Source, Paul Scherrer Institute, 5232 Villigen-PSI, Switzerland
- National Institute of Materials Physics, Atomistilor 405A, 077125 Magurele, Romania
| | - Yunzhong Chen
- Department of Energy Conversion and Storage, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Xiaoqiang Wang
- Swiss Light Source, Paul Scherrer Institute, 5232 Villigen-PSI, Switzerland
| | - Thorsten Schmitt
- Swiss Light Source, Paul Scherrer Institute, 5232 Villigen-PSI, Switzerland
| | - Milan Radovic
- Swiss Light Source, Paul Scherrer Institute, 5232 Villigen-PSI, Switzerland
| | - Naoto Nagaosa
- RIKEN Center for Emergent Matter Science, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
- Department of Applied Physics, University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Andrey S Mishchenko
- RIKEN Center for Emergent Matter Science, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Roser Valentí
- Institut für Theoretische Physik, Goethe-Universität Frankfurt am Main, Max-von-Laue-Strasse 1, 60438 Frankfurt am Main, Germany
| | - Nini Pryds
- Department of Energy Conversion and Storage, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
| | - Vladimir N Strocov
- Swiss Light Source, Paul Scherrer Institute, 5232 Villigen-PSI, Switzerland
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7
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Schuwalow S, Schröter NBM, Gukelberger J, Thomas C, Strocov V, Gamble J, Chikina A, Caputo M, Krieger J, Gardner GC, Troyer M, Aeppli G, Manfra MJ, Krogstrup P. Band Structure Extraction at Hybrid Narrow-Gap Semiconductor-Metal Interfaces. Adv Sci (Weinh) 2021; 8:2003087. [PMID: 33643798 PMCID: PMC7887586 DOI: 10.1002/advs.202003087] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/12/2020] [Revised: 10/07/2020] [Indexed: 06/12/2023]
Abstract
The design of epitaxial semiconductor-superconductor and semiconductor-metal quantum devices requires a detailed understanding of the interfacial electronic band structure. However, the band alignment of buried interfaces is difficult to predict theoretically and to measure experimentally. This work presents a procedure that allows to reliably determine critical parameters for engineering quantum devices; band offset, band bending profile, and number of occupied quantum well subbands of interfacial accumulation layers at semiconductor-metal interfaces. Soft X-ray angle-resolved photoemission is used to directly measure the quantum well states as well as valence bands and core levels for the InAs(100)/Al interface, an important platform for Majorana-zero-mode based topological qubits, and demonstrate that the fabrication process strongly influences the band offset, which in turn controls the topological phase diagrams. Since the method is transferable to other narrow gap semiconductors, it can be used more generally for engineering semiconductor-metal and semiconductor-superconductor interfaces in gate-tunable superconducting devices.
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Affiliation(s)
- Sergej Schuwalow
- Center for Quantum DevicesNiels Bohr InstituteUniversity of Copenhagen and Microsoft Quantum Materials Lab CopenhagenLyngbyDenmark
| | | | | | - Candice Thomas
- Microsoft Station Q PurdueBirck Nanotechnology CenterPurdue UniversityWest LafayetteIN47907USA
- Department of Physics and AstronomyPurdue UniversityWest LafayetteIN47907USA
| | - Vladimir Strocov
- Paul Scherrer InstitutSwiss Light SourcePSIVilligenCH‐5232Switzerland
| | - John Gamble
- Microsoft QuantumOne Microsoft WayRedmondWA98052USA
| | - Alla Chikina
- Paul Scherrer InstitutSwiss Light SourcePSIVilligenCH‐5232Switzerland
| | - Marco Caputo
- Paul Scherrer InstitutSwiss Light SourcePSIVilligenCH‐5232Switzerland
| | - Jonas Krieger
- Paul Scherrer InstitutSwiss Light SourcePSIVilligenCH‐5232Switzerland
| | - Geoffrey C. Gardner
- Microsoft Station Q PurdueBirck Nanotechnology CenterPurdue UniversityWest LafayetteIN47907USA
| | | | - Gabriel Aeppli
- Paul Scherrer InstitutSwiss Light SourcePSIVilligenCH‐5232Switzerland
- Physics DepartmentETHZurichCH‐8093Switzerland
- Institut de PhysiqueEPFLLausanneCH‐1015Switzerland
| | - Michael J. Manfra
- Microsoft Station Q PurdueBirck Nanotechnology CenterPurdue UniversityWest LafayetteIN47907USA
- Department of Physics and AstronomyPurdue UniversityWest LafayetteIN47907USA
- School of Electrical and Computer Engineering and School of Materials EngineeringPurdue UniversityWest LafayetteIN47907USA
| | - Peter Krogstrup
- Center for Quantum DevicesNiels Bohr InstituteUniversity of Copenhagen and Microsoft Quantum Materials Lab CopenhagenLyngbyDenmark
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8
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Ma J, Wang H, Nie S, Yi C, Xu Y, Li H, Jandke J, Wulfhekel W, Huang Y, West D, Richard P, Chikina A, Strocov VN, Mesot J, Weng H, Zhang S, Shi Y, Qian T, Shi M, Ding H. Emergence of Nontrivial Low-Energy Dirac Fermions in Antiferromagnetic EuCd 2 As 2. Adv Mater 2020; 32:e1907565. [PMID: 32091144 DOI: 10.1002/adma.201907565] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2019] [Revised: 01/20/2020] [Indexed: 06/10/2023]
Abstract
Parity-time symmetry plays an essential role for the formation of Dirac states in Dirac semimetals. So far, all of the experimentally identified topologically nontrivial Dirac semimetals (DSMs) possess both parity and time reversal symmetry. The realization of magnetic topological DSMs remains a major issue in topological material research. Here, combining angle-resolved photoemission spectroscopy with density functional theory calculations, it is ascertained that band inversion induces a topologically nontrivial ground state in EuCd2 As2 . As a result, ideal magnetic Dirac fermions with simplest double cone structure near the Fermi level emerge in the antiferromagnetic (AFM) phase. The magnetic order breaks time reversal symmetry, but preserves inversion symmetry. The double degeneracy of the Dirac bands is protected by a combination of inversion, time-reversal, and an additional translation operation. Moreover, the calculations show that a deviation of the magnetic moments from the c-axis leads to the breaking of C3 rotation symmetry, and thus, a small bandgap opens at the Dirac point in the bulk. In this case, the system hosts a novel state containing three different types of topological insulator: axion insulator, AFM topological crystalline insulator (TCI), and higher order topological insulator. The results provide an enlarged platform for the quest of topological Dirac fermions in a magnetic system.
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Affiliation(s)
- Junzhang Ma
- Paul Scherrer Institute, Swiss Light Source, CH-5232, Villigen, PSI, Switzerland
- Institute of Condensed Matter Physics, École Polytechnique Fédérale de Lausanne, CH-10 15, Lausanne, Switzerland
| | - Han Wang
- Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, Troy, NY, 12180, USA
| | - Simin Nie
- Department of Materials Science and Engineering, Stanford University, Stanford, CA, 94305, USA
| | - Changjiang Yi
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physics, University of Chinese Academy of Sciences, Beijing, 100190, China
| | - Yuanfeng Xu
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physics, University of Chinese Academy of Sciences, Beijing, 100190, China
| | - Hang Li
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physics, University of Chinese Academy of Sciences, Beijing, 100190, China
| | - Jasmin Jandke
- Paul Scherrer Institute, Swiss Light Source, CH-5232, Villigen, PSI, Switzerland
| | - Wulf Wulfhekel
- Physikalisches Institut, Karlsruhe Institute of Technology, 76131, Karlsruhe, Germany
| | - Yaobo Huang
- Shanghai Synchrotron Radiation Facility, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai, 201204, China
| | - Damien West
- Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, Troy, NY, 12180, USA
| | - Pierre Richard
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physics, University of Chinese Academy of Sciences, Beijing, 100190, China
- Institut quantique, Université de Sherbrooke, 2500 boulevard de l'Université, Sherbrooke, Québec, J1K 2R1, Canada
| | - Alla Chikina
- Paul Scherrer Institute, Swiss Light Source, CH-5232, Villigen, PSI, Switzerland
| | - Vladimir N Strocov
- Paul Scherrer Institute, Swiss Light Source, CH-5232, Villigen, PSI, Switzerland
| | - Joël Mesot
- Paul Scherrer Institute, Swiss Light Source, CH-5232, Villigen, PSI, Switzerland
- Institute of Condensed Matter Physics, École Polytechnique Fédérale de Lausanne, CH-10 15, Lausanne, Switzerland
| | - Hongming Weng
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- Songshan Lake Materials Laboratory Dongguan, Guangdong, 523808, China
| | - Shengbai Zhang
- Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, Troy, NY, 12180, USA
| | - Youguo Shi
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- Songshan Lake Materials Laboratory Dongguan, Guangdong, 523808, China
| | - Tian Qian
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- Songshan Lake Materials Laboratory Dongguan, Guangdong, 523808, China
| | - Ming Shi
- Paul Scherrer Institute, Swiss Light Source, CH-5232, Villigen, PSI, Switzerland
| | - Hong Ding
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physics, University of Chinese Academy of Sciences, Beijing, 100190, China
- Songshan Lake Materials Laboratory Dongguan, Guangdong, 523808, China
- CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing, 100190, China
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9
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Ma JZ, Nie SM, Yi CJ, Jandke J, Shang T, Yao MY, Naamneh M, Yan LQ, Sun Y, Chikina A, Strocov VN, Medarde M, Song M, Xiong YM, Xu G, Wulfhekel W, Mesot J, Reticcioli M, Franchini C, Mudry C, Müller M, Shi YG, Qian T, Ding H, Shi M. Spin fluctuation induced Weyl semimetal state in the paramagnetic phase of EuCd 2As 2. Sci Adv 2019; 5:eaaw4718. [PMID: 31309151 PMCID: PMC6625818 DOI: 10.1126/sciadv.aaw4718] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2018] [Accepted: 06/10/2019] [Indexed: 05/22/2023]
Abstract
Weyl fermions as emergent quasiparticles can arise in Weyl semimetals (WSMs) in which the energy bands are nondegenerate, resulting from inversion or time-reversal symmetry breaking. Nevertheless, experimental evidence for magnetically induced WSMs is scarce. Here, using photoemission spectroscopy, we observe that the degeneracy of Bloch bands is already lifted in the paramagnetic phase of EuCd2As2. We attribute this effect to the itinerant electrons experiencing quasi-static and quasi-long-range ferromagnetic fluctuations. Moreover, the spin-nondegenerate band structure harbors a pair of ideal Weyl nodes near the Fermi level. Hence, we show that long-range magnetic order and the spontaneous breaking of time-reversal symmetry are not essential requirements for WSM states in centrosymmetric systems and that WSM states can emerge in a wider range of condensed matter systems than previously thought.
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Affiliation(s)
- J.-Z. Ma
- Swiss Light Source, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
- Institute of Condensed Matter Physics, École Polytechnique Fédérale de Lausanne, CH-10 15 Lausanne, Switzerland
| | - S. M. Nie
- Department of Materials Science and Engineering, Stanford University, Stanford, CA 94305, USA
| | - C. J. Yi
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physics, University of Chinese Academy of Sciences, Beijing 100190, China
| | - J. Jandke
- Swiss Light Source, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
| | - T. Shang
- Swiss Light Source, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
- Institute of Condensed Matter Physics, École Polytechnique Fédérale de Lausanne, CH-10 15 Lausanne, Switzerland
- Laboratory for Multiscale Materials Experiments, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
| | - M. Y. Yao
- Swiss Light Source, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
| | - M. Naamneh
- Swiss Light Source, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
| | - L. Q. Yan
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Y. Sun
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physics, University of Chinese Academy of Sciences, Beijing 100190, China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China
| | - A. Chikina
- Swiss Light Source, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
| | - V. N. Strocov
- Swiss Light Source, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
| | - M. Medarde
- Laboratory for Multiscale Materials Experiments, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
| | - M. Song
- Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions, High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei, Anhui 230031, China
- University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Y.-M. Xiong
- Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions, High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei, Anhui 230031, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, China
| | - G. Xu
- Wuhan National High Magnetic Field Center and School of Physics, Huazhong University of Science and Technology, Wuhan 430074, China
| | - W. Wulfhekel
- Physikalisches Institut, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany
| | - J. Mesot
- Swiss Light Source, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
- Institute of Condensed Matter Physics, École Polytechnique Fédérale de Lausanne, CH-10 15 Lausanne, Switzerland
- Laboratory for Solid State Physics, ETH Zürich, CH-8093 Zürich, Switzerland
| | - M. Reticcioli
- Faculty of Physics, Center for Computational Materials Science, University of Vienna, A-1090 Vienna, Austria
| | - C. Franchini
- Faculty of Physics, Center for Computational Materials Science, University of Vienna, A-1090 Vienna, Austria
- Dipartimento di Fisica e Astronomia, Università di Bologna, 40127 Bologna, Italy
| | - C. Mudry
- Condensed Matter Theory Group, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
- Institute of Physics, Ecole Polytechnique Federale de Lausanne, CH1015 Lausanne, Switzerland
| | - M. Müller
- Condensed Matter Theory Group, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
| | - Y. G. Shi
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China
| | - T. Qian
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China
- CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing 100190, China
| | - H. Ding
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physics, University of Chinese Academy of Sciences, Beijing 100190, China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China
- CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing 100190, China
| | - M. Shi
- Swiss Light Source, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
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10
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Güttler M, Generalov A, Fujimori SI, Kummer K, Chikina A, Seiro S, Danzenbächer S, Koroteev YM, Chulkov EV, Radovic M, Shi M, Plumb NC, Laubschat C, Allen JW, Krellner C, Geibel C, Vyalikh DV. Divalent EuRh 2Si 2 as a reference for the Luttinger theorem and antiferromagnetism in trivalent heavy-fermion YbRh 2Si 2. Nat Commun 2019; 10:796. [PMID: 30770811 PMCID: PMC6377675 DOI: 10.1038/s41467-019-08688-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2018] [Accepted: 01/25/2019] [Indexed: 11/08/2022] Open
Abstract
Application of the Luttinger theorem to the Kondo lattice YbRh2Si2 suggests that its large 4f-derived Fermi surface (FS) in the paramagnetic (PM) regime should be similar in shape and volume to that of the divalent local-moment antiferromagnet (AFM) EuRh2Si2 in its PM regime. Here we show by angle-resolved photoemission spectroscopy that paramagnetic EuRh2Si2 has a large FS essentially similar to the one seen in YbRh2Si2 down to 1 K. In EuRh2Si2 the onset of AFM order below 24.5 K induces an extensive fragmentation of the FS due to Brillouin zone folding, intersection and resulting hybridization of the Fermi-surface sheets. Our results on EuRh2Si2 indicate that the formation of the AFM state in YbRh2Si2 is very likely also connected with similar changes in the FS, which have to be taken into account in the controversial analysis and discussion of anomalies observed at the quantum critical point in this system.
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Affiliation(s)
- M Güttler
- Institut für Festkörper- und Materialphysik, Technische Universität Dresden, D-01062, Dresden, Germany
| | - A Generalov
- MAX IV Laboratory, Lund University, Box 118, 22100, Lund, Sweden
| | - S I Fujimori
- Materials Sciences Research Center, Japan Atomic Energy Agency, Sayo, Hyogo, 679-5148, Japan
| | - K Kummer
- European Synchrotron Radiation Facility, 71 Avenue des Martyrs, 38043 Grenoble, France
| | - A Chikina
- Swiss Light Source and Swiss FEL, Paul Scherrer Institute, CH-5232, Villigen-PSI, Switzerland
| | - S Seiro
- IFW Dresden, Helmholtzstr. 20, 01069, Dresden, Germany
- Max-Planck-Institut für Chemische Physik fester Stoffe, 01187, Dresden, Germany
| | - S Danzenbächer
- Institut für Festkörper- und Materialphysik, Technische Universität Dresden, D-01062, Dresden, Germany
| | - Yu M Koroteev
- Tomsk State University, Lenina Av., 36, Tomsk, Russia, 634050
- Institute of Strength Physics and Materials Science, RAS, Tomsk, Russia, 634055
| | - E V Chulkov
- Tomsk State University, Lenina Av., 36, Tomsk, Russia, 634050
- Centro de Física de Materiales CFM-MPC and Centro Mixto CSIC-UPV/EHU, 20018, San Sebastián/Donostia, Spain
- Donostia International Physics Center (DIPC), 20080, San Sebastian, Spain
- Saint Petersburg State University, Saint Petersburg, Russia, 198504
| | - M Radovic
- Swiss Light Source and Swiss FEL, Paul Scherrer Institute, CH-5232, Villigen-PSI, Switzerland
| | - M Shi
- Swiss Light Source and Swiss FEL, Paul Scherrer Institute, CH-5232, Villigen-PSI, Switzerland
| | - N C Plumb
- Swiss Light Source and Swiss FEL, Paul Scherrer Institute, CH-5232, Villigen-PSI, Switzerland
| | - C Laubschat
- Institut für Festkörper- und Materialphysik, Technische Universität Dresden, D-01062, Dresden, Germany
| | - J W Allen
- Randall Laboratory, University of Michigan, 450 Church St, Ann Arbor, MI, 48109-1040, USA
| | - C Krellner
- Kristall- und Materiallabor, Physikalisches Institut, Goethe-Universität Frankfurt, Max-von-Laue Strasse 1, 60438, Frankfurt am Main, Germany
| | - C Geibel
- Max-Planck-Institut für Chemische Physik fester Stoffe, 01187, Dresden, Germany
| | - D V Vyalikh
- Donostia International Physics Center (DIPC), 20080, San Sebastian, Spain.
- IKERBASQUE, Basque Foundation for Science, 48011, Bilbao, Spain.
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11
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Chikina A, Lechermann F, Husanu MA, Caputo M, Cancellieri C, Wang X, Schmitt T, Radovic M, Strocov VN. Orbital Ordering of the Mobile and Localized Electrons at Oxygen-Deficient LaAlO 3/SrTiO 3 Interfaces. ACS Nano 2018; 12:7927-7935. [PMID: 29995384 DOI: 10.1021/acsnano.8b02335] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Interfacing different transition-metal oxides opens a route to functionalizing their rich interplay of electron, spin, orbital, and lattice degrees of freedom for electronic and spintronic devices. Electronic and magnetic properties of SrTiO3-based interfaces hosting a mobile two-dimensional electron system (2DES) are strongly influenced by oxygen vacancies, which form an electronic dichotomy, where strongly correlated localized electrons in the in-gap states (IGSs) coexist with noncorrelated delocalized 2DES. Here, we use resonant soft-X-ray photoelectron spectroscopy to prove the eg character of the IGSs, as opposed to the t2g character of the 2DES in the paradigmatic LaAlO3/SrTiO3 interface. We furthermore separate the d xy and d xz/d xz orbital contributions based on deeper consideration of the resonant photoexcitation process in terms of orbital and momentum selectivity. Supported by a self-consistent combination of density functional theory and dynamical mean field theory calculations, this experiment identifies local orbital reconstruction that goes beyond the conventional eg- vs-t2g band ordering. A hallmark of oxygen-deficient LaAlO3/SrTiO3 is a significant hybridization of the eg and t2g orbitals. Our findings provide routes for tuning the electronic and magnetic properties of oxide interfaces through "defect engineering" with oxygen vacancies.
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Affiliation(s)
- Alla Chikina
- Swiss Light Source, Paul Scherrer Institute , Villigen CH-5232 , Switzerland
| | - Frank Lechermann
- Institut für Theoretische Physik , Universität Hamburg , Jungiusstrasse 9 , Hamburg DE-20355 , Germany
| | - Marius-Adrian Husanu
- Swiss Light Source, Paul Scherrer Institute , Villigen CH-5232 , Switzerland
- National Institute of Materials Physics , Atomistilor 405A , Magurele RO-077125 , Romania
| | - Marco Caputo
- Swiss Light Source, Paul Scherrer Institute , Villigen CH-5232 , Switzerland
| | - Claudia Cancellieri
- Swiss Light Source, Paul Scherrer Institute , Villigen CH-5232 , Switzerland
- Empa, Swiss Federal Laboratories for Materials Science & Technology , Ueberlandstrasse 129 , Duebendorf CH-8600 , Switzerland
| | - Xiaoqiang Wang
- Swiss Light Source, Paul Scherrer Institute , Villigen CH-5232 , Switzerland
| | - Thorsten Schmitt
- Swiss Light Source, Paul Scherrer Institute , Villigen CH-5232 , Switzerland
| | - Milan Radovic
- Swiss Light Source, Paul Scherrer Institute , Villigen CH-5232 , Switzerland
| | - Vladimir N Strocov
- Swiss Light Source, Paul Scherrer Institute , Villigen CH-5232 , Switzerland
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12
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Horio M, Hauser K, Sassa Y, Mingazheva Z, Sutter D, Kramer K, Cook A, Nocerino E, Forslund OK, Tjernberg O, Kobayashi M, Chikina A, Schröter NBM, Krieger JA, Schmitt T, Strocov VN, Pyon S, Takayama T, Takagi H, Lipscombe OJ, Hayden SM, Ishikado M, Eisaki H, Neupert T, Månsson M, Matt CE, Chang J. Three-Dimensional Fermi Surface of Overdoped La-Based Cuprates. Phys Rev Lett 2018; 121:077004. [PMID: 30169083 DOI: 10.1103/physrevlett.121.077004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2018] [Indexed: 06/08/2023]
Abstract
We present a soft x-ray angle-resolved photoemission spectroscopy study of overdoped high-temperature superconductors. In-plane and out-of-plane components of the Fermi surface are mapped by varying the photoemission angle and the incident photon energy. No k_{z} dispersion is observed along the nodal direction, whereas a significant antinodal k_{z} dispersion is identified for La-based cuprates. Based on a tight-binding parametrization, we discuss the implications for the density of states near the van Hove singularity. Our results suggest that the large electronic specific heat found in overdoped La_{2-x}Sr_{x}CuO_{4} cannot be assigned to the van Hove singularity alone. We therefore propose quantum criticality induced by a collapsing pseudogap phase as a plausible explanation for observed enhancement of electronic specific heat.
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Affiliation(s)
- M Horio
- Physik-Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
| | - K Hauser
- Physik-Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
| | - Y Sassa
- Department of Physics and Astronomy, Uppsala University, SE-75121 Uppsala, Sweden
| | - Z Mingazheva
- Physik-Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
| | - D Sutter
- Physik-Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
| | - K Kramer
- Physik-Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
| | - A Cook
- Physik-Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
| | - E Nocerino
- Department of Applied Physics, KTH Royal Institute of Technology, Electrum 229, SE-16440 Stockholm Kista, Sweden
| | - O K Forslund
- Department of Applied Physics, KTH Royal Institute of Technology, Electrum 229, SE-16440 Stockholm Kista, Sweden
| | - O Tjernberg
- Department of Applied Physics, KTH Royal Institute of Technology, Electrum 229, SE-16440 Stockholm Kista, Sweden
| | - M Kobayashi
- Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
| | - A Chikina
- Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
| | - N B M Schröter
- Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
| | - J A Krieger
- Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
- Laboratorium für Festkörperphysik, ETH Zürich, CH-8093 Zürich, Switzerland
| | - T Schmitt
- Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
| | - V N Strocov
- Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
| | - S Pyon
- Department of Advanced Materials, University of Tokyo, Kashiwa 277-8561, Japan
| | - T Takayama
- Department of Advanced Materials, University of Tokyo, Kashiwa 277-8561, Japan
| | - H Takagi
- Department of Advanced Materials, University of Tokyo, Kashiwa 277-8561, Japan
| | - O J Lipscombe
- H. H. Wills Physics Laboratory, University of Bristol, Bristol BS8 1TL, United Kingdom
| | - S M Hayden
- H. H. Wills Physics Laboratory, University of Bristol, Bristol BS8 1TL, United Kingdom
| | - M Ishikado
- Comprehensive Research Organization for Science and Society (CROSS), Tokai, Ibaraki 319-1106, Japan
| | - H Eisaki
- Electronics and Photonics Research Institute, National Institute of Advanced Industrial Science and Technology, Ibaraki 305-8568, Japan
| | - T Neupert
- Physik-Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
| | - M Månsson
- Department of Applied Physics, KTH Royal Institute of Technology, Electrum 229, SE-16440 Stockholm Kista, Sweden
| | - C E Matt
- Physik-Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
- Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
- Department of Physics, Harvard University, Cambridge, MA 02138, USA
| | - J Chang
- Physik-Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
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13
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Generalov A, Otrokov MM, Chikina A, Kliemt K, Kummer K, Höppner M, Güttler M, Seiro S, Fedorov A, Schulz S, Danzenbächer S, Chulkov EV, Geibel C, Laubschat C, Dudin P, Hoesch M, Kim T, Radovic M, Shi M, Plumb NC, Krellner C, Vyalikh DV. Spin Orientation of Two-Dimensional Electrons Driven by Temperature-Tunable Competition of Spin-Orbit and Exchange-Magnetic Interactions. Nano Lett 2017; 17:811-820. [PMID: 28032768 DOI: 10.1021/acs.nanolett.6b04036] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Finding ways to create and control the spin-dependent properties of two-dimensional electron states (2DESs) is a major challenge for the elaboration of novel spin-based devices. Spin-orbit and exchange-magnetic interactions (SOI and EMI) are two fundamental mechanisms that enable access to the tunability of spin-dependent properties of carriers. The silicon surface of HoRh2Si2 appears to be a unique model system, where concurrent SOI and EMI can be visualized and controlled by varying the temperature. The beauty and simplicity of this system lie in the 4f moments, which act as a multiple tuning instrument on the 2DESs, as the 4f projections parallel and perpendicular to the surface order at essentially different temperatures. Here we show that the SOI locks the spins of the 2DESs exclusively in the surface plane when the 4f moments are disordered: the Rashba-Bychkov effect. When the temperature is gradually lowered and the system experiences magnetic order, the rising EMI progressively competes with the SOI leading to a fundamental change in the spin-dependent properties of the 2DESs. The spins rotate and reorient toward the out-of-plane Ho 4f moments. Our findings show that the direction of the spins and the spin-splitting of the two-dimensional electrons at the surface can be manipulated in a controlled way by using only one parameter: the temperature.
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Affiliation(s)
| | - Mikhail M Otrokov
- Departamento de Fisica de Materiales and CFM-MPC UPV/EHU, Donostia International Physics Center (DIPC) , 20080 San Sebastian, Spain
- Tomsk State University, Lenina Av., 36, 634050 Tomsk, Russia
| | - Alla Chikina
- Institute of Solid State Physics, Dresden University of Technology , Zellescher Weg 16, D-01062 Dresden, Germany
| | - Kristin Kliemt
- Kristall- und Materiallabor, Physikalisches Institut, Goethe-Universität Frankfurt , Max-von-Laue Straße 1, D-60438 Frankfurt am Main, Germany
| | - Kurt Kummer
- European Synchrotron Radiation Facility, 71 Avenue des Martyrs, CS40220, F-38043 Grenoble Cedex 9, France
| | - Marc Höppner
- Max Planck Institute for Solid State Research, Heisenberg Straße 1, D-70569 Stuttgart, Germany
| | - Monika Güttler
- Institute of Solid State Physics, Dresden University of Technology , Zellescher Weg 16, D-01062 Dresden, Germany
| | - Silvia Seiro
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, D-01187 Dresden, Germany
| | | | - Susanne Schulz
- Institute of Solid State Physics, Dresden University of Technology , Zellescher Weg 16, D-01062 Dresden, Germany
| | - Steffen Danzenbächer
- Institute of Solid State Physics, Dresden University of Technology , Zellescher Weg 16, D-01062 Dresden, Germany
| | - Evgueni V Chulkov
- Departamento de Fisica de Materiales and CFM-MPC UPV/EHU, Donostia International Physics Center (DIPC) , 20080 San Sebastian, Spain
- Tomsk State University, Lenina Av., 36, 634050 Tomsk, Russia
- Saint Petersburg State University , 198504 Saint Petersburg, Russia
| | - Christoph Geibel
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, D-01187 Dresden, Germany
| | - Clemens Laubschat
- Institute of Solid State Physics, Dresden University of Technology , Zellescher Weg 16, D-01062 Dresden, Germany
| | | | | | - Timur Kim
- Diamond Light Source, Didcot OX11 0DE, U.K
| | | | | | | | - Cornelius Krellner
- Kristall- und Materiallabor, Physikalisches Institut, Goethe-Universität Frankfurt , Max-von-Laue Straße 1, D-60438 Frankfurt am Main, Germany
| | - Denis V Vyalikh
- Departamento de Fisica de Materiales and CFM-MPC UPV/EHU, Donostia International Physics Center (DIPC) , 20080 San Sebastian, Spain
- Institute of Solid State Physics, Dresden University of Technology , Zellescher Weg 16, D-01062 Dresden, Germany
- Saint Petersburg State University , 198504 Saint Petersburg, Russia
- IKERBASQUE, Basque Foundation for Science , 48011 Bilbao, Spain
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15
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Usachov D, Fedorov A, Otrokov MM, Chikina A, Vilkov O, Petukhov A, Rybkin AG, Koroteev YM, Chulkov EV, Adamchuk VK, Grüneis A, Laubschat C, Vyalikh DV. Observation of single-spin Dirac fermions at the graphene/ferromagnet interface. Nano Lett 2015; 15:2396-2401. [PMID: 25734657 DOI: 10.1021/nl504693u] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
With the discovery and first characterization of graphene, its potential for spintronic applications was recognized immediately. Since then, an active field of research has developed trying to overcome the practical hurdles. One of the most severe challenges is to find appropriate interfaces between graphene and ferromagnetic layers, which are granting efficient injection of spin-polarized electrons. Here, we show that graphene grown under appropriate conditions on Co(0001) demonstrates perfect structural properties and simultaneously exhibits highly spin-polarized charge carriers. The latter was conclusively proven by observation of a single-spin Dirac cone near the Fermi level. This was accomplished experimentally using spin- and angle-resolved photoelectron spectroscopy, and theoretically with density functional calculations. Our results demonstrate that the graphene/Co(0001) system represents an interesting candidate for applications in devices using the spin degree of freedom.
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Affiliation(s)
- Dmitry Usachov
- †St. Petersburg State University, 198504 St. Petersburg, Russia
| | - Alexander Fedorov
- †St. Petersburg State University, 198504 St. Petersburg, Russia
- ‡Physikalisches Institut, Universität zu Köln, Zülpicher Strasse 77, 50937 Köln, Germany
- ¶IFW Dresden, P.O. Box 270116, D-01171 Dresden, Germany
| | - Mikhail M Otrokov
- §Tomsk State University, Lenina Avenue 36, 634050 Tomsk, Russia
- ∥Donostia International Physics Center (DIPC), Departamento de Fisica de Materiales and CFM-MPC UPV/EHU, 20080 San Sebastian, Spain
| | - Alla Chikina
- †St. Petersburg State University, 198504 St. Petersburg, Russia
- ⊥Institute of Solid State Physics, Dresden University of Technology, D-01062 Dresden, Germany
| | - Oleg Vilkov
- †St. Petersburg State University, 198504 St. Petersburg, Russia
| | | | - Artem G Rybkin
- †St. Petersburg State University, 198504 St. Petersburg, Russia
| | - Yury M Koroteev
- §Tomsk State University, Lenina Avenue 36, 634050 Tomsk, Russia
- #Institute of Strength Physics and Materials Science of Siberian Branch Russian Academy of Sciences, pr. Akademicheskii, 2/4, 634021 Tomsk, Russia
| | - Evgueni V Chulkov
- §Tomsk State University, Lenina Avenue 36, 634050 Tomsk, Russia
- ∥Donostia International Physics Center (DIPC), Departamento de Fisica de Materiales and CFM-MPC UPV/EHU, 20080 San Sebastian, Spain
| | - Vera K Adamchuk
- †St. Petersburg State University, 198504 St. Petersburg, Russia
| | - Alexander Grüneis
- ‡Physikalisches Institut, Universität zu Köln, Zülpicher Strasse 77, 50937 Köln, Germany
| | - Clemens Laubschat
- ⊥Institute of Solid State Physics, Dresden University of Technology, D-01062 Dresden, Germany
| | - Denis V Vyalikh
- †St. Petersburg State University, 198504 St. Petersburg, Russia
- ⊥Institute of Solid State Physics, Dresden University of Technology, D-01062 Dresden, Germany
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16
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Gofryk K, Saparov B, Durakiewicz T, Chikina A, Danzenbächer S, Vyalikh DV, Graf MJ, Sefat AS. Fermi-surface reconstruction and complex phase equilibria in CaFe2As2. Phys Rev Lett 2014; 112:186401. [PMID: 24856707 DOI: 10.1103/physrevlett.112.186401] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2013] [Indexed: 06/03/2023]
Abstract
Fermi-surface topology governs the relationship between magnetism and superconductivity in iron-based materials. Using low-temperature transport, angle-resolved photoemission, and x-ray diffraction, we show unambiguous evidence of large Fermi-surface reconstruction in CaFe2As2 at magnetic spin-density-wave and nonmagnetic collapsed-tetragonal (cT) transitions. For the cT transition, the change in the Fermi-surface topology has a different character with no contribution from the hole part of the Fermi surface. In addition, the results suggest that the pressure effect in CaFe2As2 is mainly leading to a rigid-band-like change of the valence electronic structure. We discuss these results and their implications for magnetism and superconductivity in this material.
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Affiliation(s)
- K Gofryk
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - B Saparov
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - T Durakiewicz
- Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - A Chikina
- Department of Physics, St. Petersburg State University, St. Petersburg 198504, Russia and Institute of Solid State Physics, Dresden University of Technology, Zellescher Weg 16, D-01062 Dresden, Germany
| | - S Danzenbächer
- Institute of Solid State Physics, Dresden University of Technology, Zellescher Weg 16, D-01062 Dresden, Germany
| | - D V Vyalikh
- Department of Physics, St. Petersburg State University, St. Petersburg 198504, Russia and Institute of Solid State Physics, Dresden University of Technology, Zellescher Weg 16, D-01062 Dresden, Germany
| | - M J Graf
- Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - A S Sefat
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
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17
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Höppner M, Seiro S, Chikina A, Fedorov A, Güttler M, Danzenbächer S, Generalov A, Kummer K, Patil S, Molodtsov SL, Kucherenko Y, Geibel C, Strocov VN, Shi M, Radovic M, Schmitt T, Laubschat C, Vyalikh DV. Interplay of Dirac fermions and heavy quasiparticles in solids. Nat Commun 2013; 4:1646. [PMID: 23552061 DOI: 10.1038/ncomms2654] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2012] [Accepted: 02/26/2013] [Indexed: 11/09/2022] Open
Abstract
Many-body interactions in crystalline solids can be conveniently described in terms of quasiparticles with strongly renormalized masses as compared with those of non-interacting particles. Examples of extreme mass renormalization are on the one hand graphene, where the charge carriers obey the linear dispersion relation of massless Dirac fermions, and on the other hand heavy-fermion materials where the effective electron mass approaches the mass of a proton. Here we show that both extremes, Dirac fermions, like they are found in graphene and extremely heavy quasiparticles characteristic for Kondo materials, may not only coexist in a solid but can also undergo strong mutual interactions. Using the example of EuRh₂Si₂, we explicitly demonstrate that these interactions can take place at the surface and in the bulk. The presence of the linear dispersion is imposed solely by the crystal symmetry, whereas the existence of heavy quasiparticles is caused by the localized nature of the 4f states.
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Affiliation(s)
- M Höppner
- Max Planck Institute for Solid State Research, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
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