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Sheverdyaeva PM, Bihlmayer G, Cappelluti E, Pacilé D, Mazzola F, Atodiresei N, Jugovac M, Grimaldi I, Contini G, Kundu AK, Vobornik I, Fujii J, Moras P, Carbone C, Ferrari L. Spin-Dependent ππ^{*} Gap in Graphene on a Magnetic Substrate. PHYSICAL REVIEW LETTERS 2024; 132:266401. [PMID: 38996316 DOI: 10.1103/physrevlett.132.266401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2023] [Revised: 03/06/2024] [Accepted: 05/21/2024] [Indexed: 07/14/2024]
Abstract
We present a detailed analysis of the electronic properties of graphene/Eu/Ni(111). By using angle- and spin-resolved photoemission spectroscopy and ab initio calculations, we show that the intercalation of Eu in the graphene/Ni(111) interface gives rise to a gapped freestanding dispersion of the ππ^{*} Dirac cones at the K[over ¯] point with an additional lifting of the spin degeneracy due to the mixing of graphene and Eu states. The interaction with the magnetic substrate results in a large spin-dependent gap in the Dirac cones with a topological nature characterized by a large Berry curvature and a spin-polarized Van Hove singularity, whose closeness to the Fermi level gives rise to a polaronic band.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | - Asish K Kundu
- CNR-Istituto di Struttura della Materia (CNR-ISM), Strada Statale 14, km 163.5, 34149 Trieste, Italy
- International Center for Theoretical Physics (ICTP), Trieste 34151, Italy
- National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, New York 11973, USA
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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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Kolmer M, Ko W, Hall J, Chen S, Zhang J, Zhao H, Ke L, Wang CZ, Li AP, Tringides MC. Breaking of Inversion Symmetry and Interlayer Electronic Coupling in Bilayer Graphene Heterostructure by Structural Implementation of High Electric Displacement Fields. J Phys Chem Lett 2022; 13:11571-11580. [PMID: 36475696 DOI: 10.1021/acs.jpclett.2c02407] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Controlling the interlayer coupling in two-dimensional (2D) materials generates novel electronic and topological phases. Its effective implementation is commonly done with a transverse electric field. However, phases generated by high displacement fields are elusive in this standard approach. Here, we introduce an exceptionally large displacement field by structural modification of a model system: AB-stacked bilayer graphene (BLG) on a SiC(0001) surface. We show that upon intercalation of gadolinium, electronic states in the top graphene layers exhibit a significant difference in the on-site potential energy, which effectively breaks the interlayer coupling between them. As a result, for energies close to the corresponding Dirac points, the BLG system behaves like two electronically isolated single graphene layers. This is proven by local scanning tunneling microscopy (STM)/spectroscopy, corroborated by density functional theory, tight binding, and multiprobe STM transport. The work presents metal intercalation as a promising approach for the synthesis of 2D graphene heterostructures with electronic phases generated by giant displacement fields.
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Affiliation(s)
- Marek Kolmer
- Ames National Laboratory, U.S. Department of Energy, Ames, Iowa50011, United States
| | - Wonhee Ko
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee37831, United States
| | - Joseph Hall
- Ames National Laboratory, U.S. Department of Energy, Ames, Iowa50011, United States
- Department of Physics and Astronomy, Iowa State University, Ames, Iowa50011, United States
| | - Shen Chen
- Ames National Laboratory, U.S. Department of Energy, Ames, Iowa50011, United States
- Department of Physics and Astronomy, Iowa State University, Ames, Iowa50011, United States
| | - Jianhua Zhang
- Department of Physics, Hainan University, Haikou570228, China
| | - Haijun Zhao
- School of Physics, Southeast University, Nanjing211189, China
| | - Liqin Ke
- Ames National Laboratory, U.S. Department of Energy, Ames, Iowa50011, United States
| | - Cai-Zhuang Wang
- Ames National Laboratory, U.S. Department of Energy, Ames, Iowa50011, United States
- Department of Physics and Astronomy, Iowa State University, Ames, Iowa50011, United States
| | - An-Ping Li
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee37831, United States
| | - Michael C Tringides
- Ames National Laboratory, U.S. Department of Energy, Ames, Iowa50011, United States
- Department of Physics and Astronomy, Iowa State University, Ames, Iowa50011, United States
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Shukla V. Observation of critical magnetic behavior in 2D carbon based composites. NANOSCALE ADVANCES 2020; 2:962-990. [PMID: 36133050 PMCID: PMC9418615 DOI: 10.1039/c9na00663j] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2019] [Accepted: 01/08/2020] [Indexed: 05/30/2023]
Abstract
Two dimensional (2D) carbonaceous materials such as graphene and its derivatives, e.g., graphdiyne, have enormous potential possibilities in major fields of scientific research. Theoretically, it has been proposed that the perfect atomic lattice arrangement of these materials is responsible for their outstanding physical and chemical properties, and also for their poor magnetic properties. Experimentally, it is difficult to obtain a perfect atomic lattice of carbon atoms due to the appearance of structural disorder. This structural disorder is generated during the growth or synthesis of carbon-related materials. Investigations of structural disorder reveal that it can offer both advantages and disadvantages depending on the application. For instance, disorder reduces the thermal and mechanical stability, and deteriorates the performance of 2D carbon-based electronic devices. The most interesting effect of structural disorder can be seen in the field of magnetism. Disorder not only creates magnetic ordering within 2D carbon materials but also influences the local electronic structure, which opens the door for future spintronic devices. Although various studies on the disorder induced magnetism of 2D carbon materials are available in the literature, some parts of the above field have still not been fully exploited. This review presents existing work for the future development of 2D carbon-based devices.
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Affiliation(s)
- Vineeta Shukla
- Nuclear Condensed Matter Physics Laboratory, Department of Physics, Indian Institute of Technology Kharagpur-721302 India
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Briggs N, Gebeyehu ZM, Vera A, Zhao T, Wang K, De La Fuente Duran A, Bersch B, Bowen T, Knappenberger KL, Robinson JA. Epitaxial graphene/silicon carbide intercalation: a minireview on graphene modulation and unique 2D materials. NANOSCALE 2019; 11:15440-15447. [PMID: 31393495 DOI: 10.1039/c9nr03721g] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Intercalation of atomic species through epitaxial graphene on silicon carbide began only a few years following its initial report in 2004. The impact of intercalation on the electronic properties of the graphene is well known; however, the intercalant itself can also exhibit intriguing properties not found in nature. This realization has inspired new interest in epitaxial graphene/silicon carbide (EG/SiC) intercalation, where the scope of the technique extends beyond modulation of graphene properties to the creation of new 2D forms of 3D materials. The mission of this minireview is to provide a concise introduction to EG/SiC intercalation and to demonstrate a simplified approach to EG/SiC intercalation. We summarize the primary techniques used to achieve and characterize EG/SiC intercalation, and show that thermal evaporation-based methods can effectively substitute for more complex synthesis techniques, enabling large-scale intercalation of non-refractory metals and compounds including two-dimensional silver (2D-Ag) and gallium nitride (2D-GaNx).
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Affiliation(s)
- Natalie Briggs
- Department of Materials Science & Engineering, Pennsylvania State University, University Park, PA 16802, USA. and Center for 2-Dimensional and Layered Materials, Pennsylvania State University, University Park, PA 16802, USA and 2-Dimensional Crystal Consortium Materials Innovation Platform, Pennsylvania State University, University Park, PA 16802, USA
| | - Zewdu M Gebeyehu
- Department of Materials Science & Engineering, Pennsylvania State University, University Park, PA 16802, USA. and Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC, The Barcelona Institute of Science and Technology (BIST), Campus UAB, Bellaterra, Barcelona, Spain and Universitat Autònoma de Barcelona (UAB), Bellaterra, Spain
| | - Alexander Vera
- Department of Materials Science & Engineering, Pennsylvania State University, University Park, PA 16802, USA. and Center for 2-Dimensional and Layered Materials, Pennsylvania State University, University Park, PA 16802, USA
| | - Tian Zhao
- Department of Chemistry, Pennsylvania State University, University Park, PA 16802, USA
| | - Ke Wang
- Materials Characterization Laboratory, University Park, PA 16802, USA
| | - Ana De La Fuente Duran
- Department of Materials Science & Engineering, Pennsylvania State University, University Park, PA 16802, USA.
| | - Brian Bersch
- Department of Materials Science & Engineering, Pennsylvania State University, University Park, PA 16802, USA. and Center for 2-Dimensional and Layered Materials, Pennsylvania State University, University Park, PA 16802, USA
| | - Timothy Bowen
- Department of Materials Science & Engineering, Pennsylvania State University, University Park, PA 16802, USA. and Center for 2-Dimensional and Layered Materials, Pennsylvania State University, University Park, PA 16802, USA
| | | | - Joshua A Robinson
- Department of Materials Science & Engineering, Pennsylvania State University, University Park, PA 16802, USA. and Center for 2-Dimensional and Layered Materials, Pennsylvania State University, University Park, PA 16802, USA and 2-Dimensional Crystal Consortium Materials Innovation Platform, Pennsylvania State University, University Park, PA 16802, USA and Center for Atomically-Thin Multifunctional Coatings, Pennsylvania State University, University Park, PA 16802, USA
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Surface potential and thin film quality of low work function metals on epitaxial graphene. Sci Rep 2018; 8:16487. [PMID: 30405192 PMCID: PMC6220296 DOI: 10.1038/s41598-018-34595-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2018] [Accepted: 10/18/2018] [Indexed: 11/09/2022] Open
Abstract
Metal films deposited on graphene are known to influence its electronic properties, but little is known about graphene's interactions with very low work function rare earth metals. Here we report on the work functions of a wide range of metals deposited on n-type epitaxial graphene (EG) as measured by Kelvin Probe Force Microscopy (KPFM). We compare the behaviors of rare earth metals (Pr, Eu, Er, Yb, and Y) with commonly used noble metals (Cr, Cu, Rh, Ni, Au, and Pt). The rare earth films oxidize rapidly, and exhibit unique behaviors when on graphene. We find that the measured work function of the low work function group is consistently higher than predicted, unlike the noble metals, which is likely due to rapid oxidation during measurement. Some of the low work function metals interact with graphene; for example, Eu exhibits bonding anomalies along the metal-graphene perimeter. We observe no correlation between metal work function and photovoltage, implying the metal-graphene interface properties are a more determinant factor. Yb emerges as the best choice for future applications requiring a low-work function electrical contact on graphene. Yb films have the strongest photovoltage response and maintains a relatively low surface roughness, ~5 nm, despite sensitivity to oxidation.
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