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Ichinokura S, Tokuda K, Toyoda M, Tanaka K, Saito S, Hirahara T. Van Hove Singularity and Enhanced Superconductivity in Ca-Intercalated Bilayer Graphene Induced by Confinement Epitaxy. ACS NANO 2024; 18:13738-13744. [PMID: 38741024 DOI: 10.1021/acsnano.4c01757] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2024]
Abstract
We demonstrate the impact of high-density calcium introduction into Ca-intercalated bilayer graphene on a SiC substrate, wherein a metallic layer of Ca has been identified at the interface. We have discerned that the additional Ca layer engenders a free-electron-like band, which subsequently hybridizes with a Dirac band, leading to the emergence of a van Hove singularity. Coinciding with this, there is an increase in the critical temperature for superconductivity. These findings allude to the manifestation of Ca-driven confinement epitaxy, augmenting superconductivity through the enhancement of attractive interactions in a pair of electron and hole bands with flat dispersion around the Fermi level.
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Affiliation(s)
- Satoru Ichinokura
- Department of Physics, Tokyo Institute of Technology, Tokyo 152-8551, Japan
| | - Kei Tokuda
- Department of Physics, Tokyo Institute of Technology, Tokyo 152-8551, Japan
| | - Masayuki Toyoda
- Department of Physics, Tokyo Institute of Technology, Tokyo 152-8551, Japan
| | - Kiyohisa Tanaka
- UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
| | - Susumu Saito
- Department of Physics, Tokyo Institute of Technology, Tokyo 152-8551, Japan
| | - Toru Hirahara
- Department of Physics, Tokyo Institute of Technology, Tokyo 152-8551, Japan
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2
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Narayan J, Bezborah K. Recent advances in the functionalization, substitutional doping and applications of graphene/graphene composite nanomaterials. RSC Adv 2024; 14:13413-13444. [PMID: 38660531 PMCID: PMC11041312 DOI: 10.1039/d3ra07072g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2023] [Accepted: 04/01/2024] [Indexed: 04/26/2024] Open
Abstract
Recently, graphene and graphene-based nanomaterials have emerged as advanced carbon functional materials with specialized unique electronic, optical, mechanical, and chemical properties. These properties have made graphene an exceptional material for a wide range of promising applications in biological and non-biological fields. The present review illustrates the structural modifications of pristine graphene resulting in a wide variety of derivatives. The significance of substitutional doping with alkali-metals, alkaline earth metals, and III-VII group elements apart from the transition metals of the periodic table is discussed. The paper reviews various chemical and physical preparation routes of graphene, its derivatives and graphene-based nanocomposites at room and elevated temperatures in various solvents. The difficulty in dispersing it in water and organic solvents make it essential to functionalize graphene and its derivatives. Recent trends and advances are discussed at length. Controlled reduction reactions in the presence of various dopants leading to nanocomposites along with suitable surfactants essential to enhance its potential applications in the semiconductor industry and biological fields are discussed in detail.
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Affiliation(s)
- Jyoti Narayan
- Synthetic Nanochemistry Laboratory, Department of Basic Sciences & Social Sciences, (Chemistry Division) School of Technology, North Eastern Hill University Shillong 793022 Meghalaya India
| | - Kangkana Bezborah
- Synthetic Nanochemistry Laboratory, Department of Basic Sciences & Social Sciences, (Chemistry Division) School of Technology, North Eastern Hill University Shillong 793022 Meghalaya India
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3
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Dong C, Lu LS, Lin YC, Robinson JA. Air-Stable, Large-Area 2D Metals and Semiconductors. ACS NANOSCIENCE AU 2024; 4:115-127. [PMID: 38644964 PMCID: PMC11027125 DOI: 10.1021/acsnanoscienceau.3c00047] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/18/2023] [Revised: 12/16/2023] [Accepted: 12/18/2023] [Indexed: 04/23/2024]
Abstract
Two-dimensional (2D) materials are popular for fundamental physics study and technological applications in next-generation electronics, spintronics, and optoelectronic devices due to a wide range of intriguing physical and chemical properties. Recently, the family of 2D metals and 2D semiconductors has been expanding rapidly because they offer properties once unknown to us. One of the challenges to fully access their properties is poor stability in ambient conditions. In the first half of this Review, we briefly summarize common methods of preparing 2D metals and highlight some recent approaches for making air-stable 2D metals. Additionally, we introduce the physicochemical properties of some air-stable 2D metals recently explored. The second half discusses the air stability and oxidation mechanisms of 2D transition metal dichalcogenides and some elemental 2D semiconductors. Their air stability can be enhanced by optimizing growth temperature, substrates, and precursors during 2D material growth to improve material quality, which will be discussed. Other methods, including doping, postgrowth annealing, and encapsulation of insulators that can suppress defects and isolate the encapsulated samples from the ambient environment, will be reviewed.
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Affiliation(s)
- Chengye Dong
- 2-Dimensional
Crystal Consortium, The Pennsylvania State
University, University
Park, Pennsylvania 16802, United States
| | - Li-Syuan Lu
- Department
of Materials Science and Engineering, The
Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Yu-Chuan Lin
- Department
of Materials Science and Engineering, The
Pennsylvania State University, University Park, Pennsylvania 16802, United States
- Department
of Materials Science and Engineering, National
Yang Ming Chiao Tung University, Hsinchu 300, Taiwan
| | - Joshua A. Robinson
- 2-Dimensional
Crystal Consortium, The Pennsylvania State
University, University
Park, Pennsylvania 16802, United States
- Department
of Materials Science and Engineering, The
Pennsylvania State University, University Park, Pennsylvania 16802, United States
- Center
for Atomically Thin Multifunctional Coatings, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
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4
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Aygar AM, Durnan O, Molavi B, Bovey SNR, Grüneis A, Szkopek T. Mass Inversion at the Lifshitz Transition in Monolayer Graphene by Diffusive, High-Density, On-Chip Doping. ACS NANO 2024; 18:9092-9099. [PMID: 38479375 DOI: 10.1021/acsnano.3c13187] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/27/2024]
Abstract
Experimental setups for charge transport measurements are typically not compatible with the ultrahigh vacuum conditions for chemical doping, limiting the charge carrier density that can be investigated by transport methods. Field-effect methods, including dielectric gating and ionic liquid gating, achieve too low a carrier density to induce electronic phase transitions. To bridge this gap, we developed an integrated flip-chip method to dope graphene by alkali vapor in the diffusive regime, suitable for charge transport measurements at ultrahigh charge carrier density. We introduce a cesium droplet into a sealed cavity filled with inert gas to dope a monolayer graphene sample by the process of cesium atom diffusion, adsorption, and ionization at the graphene surface, with doping beyond an electron density of 4.7 × 1014 cm-2 monitored by operando Hall measurement. The sealed assembly is stable against oxidation, enabling measurement of charge transport versus temperature and magnetic field. Cyclotron mass inversion is observed via the Hall effect, indicative of the change in Fermi surface geometry associated with the Liftshitz transition at the hyperbolic M point of monolayer graphene. The transparent quartz substrate also functions as an optical window, enabling nonresonant Raman scattering. Our findings show that chemical doping, hitherto restricted to ultrahigh vacuum, can be applied in a diffusive regime at ambient pressure in an inert gas environment and thus enable charge transport studies in standard cryogenic environments.
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Affiliation(s)
- Ayse Melis Aygar
- Department of Electrical and Computer Engineering, McGill University, Québec, Montréal H3A-0E9, Canada
| | - Oliver Durnan
- Department of Electrical Engineering, Columbia University, New York, New York 10027, United States
| | - Bahar Molavi
- Department of Electrical and Computer Engineering, McGill University, Québec, Montréal H3A-0E9, Canada
| | - Sam N R Bovey
- Department of Electrical and Computer Engineering, McGill University, Québec, Montréal H3A-0E9, Canada
| | - Alexander Grüneis
- Institut für Festkörperelektronik, Technische Universität Wien, Vienna 1040, Austria
| | - Thomas Szkopek
- Department of Electrical and Computer Engineering, McGill University, Québec, Montréal H3A-0E9, Canada
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5
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Norimatsu W. A Review on Carrier Mobilities of Epitaxial Graphene on Silicon Carbide. MATERIALS (BASEL, SWITZERLAND) 2023; 16:7668. [PMID: 38138815 PMCID: PMC10744437 DOI: 10.3390/ma16247668] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2023] [Revised: 12/11/2023] [Accepted: 12/14/2023] [Indexed: 12/24/2023]
Abstract
Graphene growth by thermal decomposition of silicon carbide (SiC) is a technique that produces wafer-scale, single-orientation graphene on an insulating substrate. It is often referred to as epigraphene, and has been thought to be suitable for electronics applications. In particular, high-frequency devices for communication technology or large quantum Hall plateau for metrology applications using epigraphene are expected, which require high carrier mobility. However, the carrier mobility of as-grown epigraphene exhibit the relatively low values of about 1000 cm2/Vs. Fortunately, we can hope to improve this situation by controlling the electronic state of epigraphene by modifying the surface and interface structures. In this paper, the mobility of epigraphene and the factors that govern it will be described, followed by a discussion of attempts that have been made to improve mobility in this field. These understandings are of great importance for next-generation high-speed electronics using graphene.
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Affiliation(s)
- Wataru Norimatsu
- Faculty of Science and Engineering, Waseda University, Tokyo 169-8555, Japan
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6
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Sidiropoulos TPH, Di Palo N, Rivas DE, Summers A, Severino S, Reduzzi M, Biegert J. Enhanced optical conductivity and many-body effects in strongly-driven photo-excited semi-metallic graphite. Nat Commun 2023; 14:7407. [PMID: 37973799 PMCID: PMC10654445 DOI: 10.1038/s41467-023-43191-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2023] [Accepted: 11/02/2023] [Indexed: 11/19/2023] Open
Abstract
The excitation of quasi-particles near the extrema of the electronic band structure is a gateway to electronic phase transitions in condensed matter. In a many-body system, quasi-particle dynamics are strongly influenced by the electronic single-particle structure and have been extensively studied in the weak optical excitation regime. Yet, under strong optical excitation, where light fields coherently drive carriers, the dynamics of many-body interactions that can lead to new quantum phases remain largely unresolved. Here, we induce such a highly non-equilibrium many-body state through strong optical excitation of charge carriers near the van Hove singularity in graphite. We investigate the system's evolution into a strongly-driven photo-excited state with attosecond soft X-ray core-level spectroscopy. We find an enhancement of the optical conductivity of nearly ten times the quantum conductivity and pinpoint it to carrier excitations in flat bands. This interaction regime is robust against carrier-carrier interaction with coherent optical phonons acting as an attractive force reminiscent of superconductivity. The strongly-driven non-equilibrium state is markedly different from the single-particle structure and macroscopic conductivity and is a consequence of the non-adiabatic many-body state.
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Affiliation(s)
- T P H Sidiropoulos
- ICFO - Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, 08860, Barcelona, Spain.
- Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, 12489, Berlin, Germany.
| | - N Di Palo
- ICFO - Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, 08860, Barcelona, Spain
| | - D E Rivas
- ICFO - Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, 08860, Barcelona, Spain
| | - A Summers
- ICFO - Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, 08860, Barcelona, Spain
| | - S Severino
- ICFO - Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, 08860, Barcelona, Spain
| | - M Reduzzi
- ICFO - Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, 08860, Barcelona, Spain
| | - J Biegert
- ICFO - Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, 08860, Barcelona, Spain.
- ICREA - Institució Catalana de Recerca i Estudis Avançats, Barcelona, Spain.
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7
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Rossi A, Johnson C, Balgley J, Thomas JC, Francaviglia L, Dettori R, Schmid AK, Watanabe K, Taniguchi T, Cothrine M, Mandrus DG, Jozwiak C, Bostwick A, Henriksen EA, Weber-Bargioni A, Rotenberg E. Direct Visualization of the Charge Transfer in a Graphene/α-RuCl 3 Heterostructure via Angle-Resolved Photoemission Spectroscopy. NANO LETTERS 2023; 23:8000-8005. [PMID: 37639696 PMCID: PMC10510581 DOI: 10.1021/acs.nanolett.3c01974] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2023] [Revised: 08/21/2023] [Indexed: 08/31/2023]
Abstract
We investigate the electronic properties of a graphene and α-ruthenium trichloride (α-RuCl3) heterostructure using a combination of experimental techniques. α-RuCl3 is a Mott insulator and a Kitaev material. Its combination with graphene has gained increasing attention due to its potential applicability in novel optoelectronic devices. By using a combination of spatially resolved photoemission spectroscopy and low-energy electron microscopy, we are able to provide a direct visualization of the massive charge transfer from graphene to α-RuCl3, which can modify the electronic properties of both materials, leading to novel electronic phenomena at their interface. A measurement of the spatially resolved work function allows for a direct estimate of the interface dipole between graphene and α-RuCl3. Their strong coupling could lead to new ways of manipulating electronic properties of a two-dimensional heterojunction. Understanding the electronic properties of this structure is pivotal for designing next generation low-power optoelectronics devices.
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Affiliation(s)
- Antonio Rossi
- Advanced
Light Source, Lawrence Berkeley National
Laboratory, Berkeley, California 94720, United States
- The
Molecular Foundry, Lawrence Berkeley National
Laboratory, Berkeley, California 94720, United States
- Center
for Nanotechnology Innovation @ NEST, Istituto
Italiano di Tecnologia, Pisa 56127, Italy
| | - Cameron Johnson
- The
Molecular Foundry, Lawrence Berkeley National
Laboratory, Berkeley, California 94720, United States
| | - Jesse Balgley
- Department
of Physics and Institute for Materials Science and Engineering, Washington University in St. Louis, St. Louis, Missouri 63130, United States
| | - John C. Thomas
- The
Molecular Foundry, Lawrence Berkeley National
Laboratory, Berkeley, California 94720, United States
| | - Luca Francaviglia
- The
Molecular Foundry, Lawrence Berkeley National
Laboratory, Berkeley, California 94720, United States
| | - Riccardo Dettori
- Physical
and Life Sciences Directorate, Lawrence
Livermore National Laboratory, Livermore, California 94550, United States
| | - Andreas K. Schmid
- The
Molecular Foundry, Lawrence Berkeley National
Laboratory, Berkeley, California 94720, United States
| | - Kenji Watanabe
- Research
Center for Functional Materials, National
Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- International
Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Matthew Cothrine
- Material
Science & Technology Division, Oak Ridge
National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - David G. Mandrus
- Material
Science & Technology Division, Oak Ridge
National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Chris Jozwiak
- Advanced
Light Source, Lawrence Berkeley National
Laboratory, Berkeley, California 94720, United States
| | - Aaron Bostwick
- Advanced
Light Source, Lawrence Berkeley National
Laboratory, Berkeley, California 94720, United States
| | - Erik A. Henriksen
- Department
of Physics and Institute for Materials Science and Engineering, Washington University in St. Louis, St. Louis, Missouri 63130, United States
| | - Alexander Weber-Bargioni
- The
Molecular Foundry, Lawrence Berkeley National
Laboratory, Berkeley, California 94720, United States
| | - Eli Rotenberg
- Advanced
Light Source, Lawrence Berkeley National
Laboratory, Berkeley, California 94720, United States
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8
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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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9
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Wang C, Wang K, Wang H, Tian Q, Zong J, Qiu X, Ren W, Wang L, Li FS, Zhang WB, Zhang H, Zhang Y. Observation of a Folded Dirac Cone in Heavily Doped Graphene. J Phys Chem Lett 2023; 14:7149-7156. [PMID: 37540032 DOI: 10.1021/acs.jpclett.3c01271] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/05/2023]
Abstract
Superlattice potentials imposed on graphene can alter its Dirac states, enabling the realization of various quantum phases. We report the experimental observation of a replica Dirac cone at the Brillouin zone center induced by a superlattice in heavily doped graphene with Gd intercalation using angle-resolved photoemission spectroscopy (ARPES). The replica Dirac cone arises from the (√3× √3)R30° superlattice formed by the intervalley coupling of two nonequivalent valleys (e.g., the Kekulé-like distortion phase), accompanied by a bandgap opening. According to the findings, the replica Dirac band in Gd-intercalated graphene disappears beyond a critical temperature of 30 K and can be suppressed by potassium adsorption. The modulation of the replica Dirac band is primarily attributable to the residual frozen gas, which can act as a source of intervalley scattering at temperatures below 30 K. Our results highlight the persistence of the hidden Kekulé-like phase within the heavily doped graphene, enriching our current understanding of its replica Dirac Fermions.
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Affiliation(s)
- Can Wang
- Hunan Provincial Key Laboratory of Flexible Electronic Materials Genome Engineering, School of Physics and Electronic Sciences, Changsha University of Science and Technology, Changsha 410114, China
- National Laboratory of Solid State Microstructure, School of Physics, Nanjing University, Nanjing 210093, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Kaili Wang
- National Laboratory of Solid State Microstructure, School of Physics, Nanjing University, Nanjing 210093, China
| | - Huaiqiang Wang
- National Laboratory of Solid State Microstructure, School of Physics, Nanjing University, Nanjing 210093, China
| | - Qichao Tian
- National Laboratory of Solid State Microstructure, School of Physics, Nanjing University, Nanjing 210093, China
| | - Junyu Zong
- National Laboratory of Solid State Microstructure, School of Physics, Nanjing University, Nanjing 210093, China
| | - Xiaodong Qiu
- National Laboratory of Solid State Microstructure, School of Physics, Nanjing University, Nanjing 210093, China
| | - Wei Ren
- Vacuum Interconnected Nanotech Workstation (Nano-X), Suzhou Institute of Nano-Tech and Nano-Bionics (SINANO), Chinese Academy of Sciences (CAS), Suzhou 215123, China
| | - Li Wang
- Vacuum Interconnected Nanotech Workstation (Nano-X), Suzhou Institute of Nano-Tech and Nano-Bionics (SINANO), Chinese Academy of Sciences (CAS), Suzhou 215123, China
| | - Fang-Sen Li
- Vacuum Interconnected Nanotech Workstation (Nano-X), Suzhou Institute of Nano-Tech and Nano-Bionics (SINANO), Chinese Academy of Sciences (CAS), Suzhou 215123, China
| | - Wei-Bing Zhang
- Hunan Provincial Key Laboratory of Flexible Electronic Materials Genome Engineering, School of Physics and Electronic Sciences, Changsha University of Science and Technology, Changsha 410114, China
| | - Haijun Zhang
- National Laboratory of Solid State Microstructure, School of Physics, Nanjing University, Nanjing 210093, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Yi Zhang
- National Laboratory of Solid State Microstructure, School of Physics, Nanjing University, Nanjing 210093, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
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10
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Abbas G, Sonia FJ, Jindra M, Červenka J, Kalbáč M, Frank O, Velický M. Electrostatic Gating of Monolayer Graphene by Concentrated Aqueous Electrolytes. J Phys Chem Lett 2023; 14:4281-4288. [PMID: 37126786 PMCID: PMC10184166 DOI: 10.1021/acs.jpclett.3c00814] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Electrostatic gating using electrolytes is a powerful approach for controlling the electronic properties of atomically thin two-dimensional materials such as graphene. However, the role of the ionic type, size, and concentration and the resulting gating efficiency is unclear due to the complex interplay of electrochemical processes and charge doping. Understanding these relationships facilitates the successful design of electrolyte gates and supercapacitors. To that end, we employ in situ Raman microspectroscopy combined with electrostatic gating using various concentrated aqueous electrolytes. We show that while the ionic type and concentration alter the initial doping state of graphene, they have no measurable influence over the rate of the doping of graphene with applied voltage in the high ionic strength limit of 3-15 M. Crucially, unlike for conventional dielectric gates, a large proportion of the applied voltage contributes to the Fermi level shift of graphene in concentrated electrolytes. We provide a practical overview of the doping efficiency for different gating systems.
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Affiliation(s)
- Ghulam Abbas
- J. Heyrovský Institute of Physical Chemistry, Czech Academy of Sciences, Dolejškova 2155/3, 182 23 Prague, Czech Republic
- FZU - Institute of Physics, Czech Academy of Sciences, Cukrovarnická 10/112, 162 00 Prague 6, Czech Republic
| | - Farjana J Sonia
- J. Heyrovský Institute of Physical Chemistry, Czech Academy of Sciences, Dolejškova 2155/3, 182 23 Prague, Czech Republic
| | - Martin Jindra
- J. Heyrovský Institute of Physical Chemistry, Czech Academy of Sciences, Dolejškova 2155/3, 182 23 Prague, Czech Republic
- Department of Physical Chemistry, University of Chemistry and Technology, 16628 Prague, Czech Republic
| | - Jiří Červenka
- FZU - Institute of Physics, Czech Academy of Sciences, Cukrovarnická 10/112, 162 00 Prague 6, Czech Republic
| | - Martin Kalbáč
- J. Heyrovský Institute of Physical Chemistry, Czech Academy of Sciences, Dolejškova 2155/3, 182 23 Prague, Czech Republic
| | - Otakar Frank
- J. Heyrovský Institute of Physical Chemistry, Czech Academy of Sciences, Dolejškova 2155/3, 182 23 Prague, Czech Republic
| | - Matěj Velický
- J. Heyrovský Institute of Physical Chemistry, Czech Academy of Sciences, Dolejškova 2155/3, 182 23 Prague, Czech Republic
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11
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Aggarwal D, Narula R, Ghosh S. A primer on twistronics: a massless Dirac fermion's journey to moiré patterns and flat bands in twisted bilayer graphene. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2023; 35:143001. [PMID: 36745922 DOI: 10.1088/1361-648x/acb984] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2022] [Accepted: 02/06/2023] [Indexed: 06/18/2023]
Abstract
The recent discovery of superconductivity in magic-angle twisted bilayer graphene (TBLG) has sparked a renewed interest in the strongly-correlated physics ofsp2carbons, in stark contrast to preliminary investigations which were dominated by the one-body physics of the massless Dirac fermions. We thus provide a self-contained, theoretical perspective of the journey of graphene from its single-particle physics-dominated regime to the strongly-correlated physics of the flat bands. Beginning from the origin of the Dirac points in condensed matter systems, we discuss the effect of the superlattice on the Fermi velocity and Van Hove singularities in graphene and how it leads naturally to investigations of the moiré pattern in van der Waals heterostructures exemplified by graphene-hexagonal boron-nitride and TBLG. Subsequently, we illuminate the origin of flat bands in TBLG at the magic angles by elaborating on a broad range of prominent theoretical works in a pedagogical way while linking them to available experimental support, where appropriate. We conclude by providing a list of topics in the study of the electronic properties of TBLG not covered by this review but may readily be approached with the help of this primer.
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Affiliation(s)
| | - Rohit Narula
- Department of Physics, IIT Delhi, Hauz Khas, New Delhi, India
| | - Sankalpa Ghosh
- Department of Physics, IIT Delhi, Hauz Khas, New Delhi, India
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12
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Grushevskaya H, Timoshchenko A, Lipnevich I. Topological Defects Created by Gamma Rays in a Carbon Nanotube Bilayer. NANOMATERIALS (BASEL, SWITZERLAND) 2023; 13:410. [PMID: 36770369 PMCID: PMC9921100 DOI: 10.3390/nano13030410] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/09/2022] [Revised: 12/29/2022] [Accepted: 01/07/2023] [Indexed: 06/18/2023]
Abstract
Graphene sheets are a highly radiation-resistant material for prospective nuclear applications and nanoscale defect engineering. However, the precise mechanism of graphene radiation hardness has remained elusive. In this paper, we study the origin and nature of defects induced by gamma radiation in a graphene rolled-up plane. In order to reduce the environmental influence on graphene and reveal the small effects of gamma rays, we have synthesized a novel graphene-based nanocomposite material containing a bilayer of highly aligned carbon nanotube assemblies that have been decorated by organometallic compounds and suspended on nanoporous Al2O3 membranes. The bilayer samples were irradiated by gamma rays from a 137Cs source with a fluence rate of the order of 105 m-2s-1. The interaction between the samples and gamma quanta results in the appearance of three characteristic photon escape peaks in the radiation spectra. We explain the mechanism of interaction between the graphene sheets and gamma radiation using a pseudo-Majorana fermion graphene model, which is a quasi-relativistic N=3-flavor graphene model with a Majorana-like mass term. This model admits the existence of giant charge carrier currents that are sufficient to neutralize the impact of ionizing radiation. Experimental evidence is provided for the prediction that the 661.7-keV gamma quanta transfer enough energy to the electron subsystem of graphene to bring about the deconfinement of the bound pseudo-Majorana modes and involve C atoms in a vortical motion of the electron density flows in the graphene plane. We explain the radiation hardness of graphene by the topological non-triviality of the pseudo-Majorana fermion configurations comprising the graphene charge carriers.
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13
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Marchiani D, Tonelli A, Mariani C, Frisenda R, Avila J, Dudin P, Jeong S, Ito Y, Magnani FS, Biagi R, De Renzi V, Betti MG. Tuning the Electronic Response of Metallic Graphene by Potassium Doping. NANO LETTERS 2023; 23:170-176. [PMID: 36562744 PMCID: PMC9838101 DOI: 10.1021/acs.nanolett.2c03891] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/04/2022] [Revised: 12/19/2022] [Indexed: 06/17/2023]
Abstract
Electron doping of graphene has been extensively studied on graphene-supported surfaces, where the metallicity is influenced by the substrate. Herewith we propose potassium adsorption on free-standing nanoporous graphene, thus eluding any effect due to the substrate. We monitor the electron migration in the π* downward-shifted conduction band. In this rigid band shift, we correlate the spectral density of the π* state in the upper Dirac cone with the associated plasmon, blue-shifted with increasing K dose, as deduced by electron energy loss spectroscopy. These results are confirmed by the Dirac plasmon activated by the C 1s emitted electrons, thanks to spatially resolved photoemission. This crosscheck constitutes a reference on the correlation between the electronic π* states in the conduction band and the Dirac plasmon evolution upon in situ electron doping of fully free-standing graphene.
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Affiliation(s)
- Dario Marchiani
- Physics
Department, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185Rome, Italy
| | - Andrea Tonelli
- Dipartimento
di Scienze Fisiche, Informatiche e Matematiche (FIM), Università di Modena e Reggio Emilia, 41125Modena, Italy
| | - Carlo Mariani
- Physics
Department, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185Rome, Italy
| | - Riccardo Frisenda
- Physics
Department, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185Rome, Italy
| | - José Avila
- Synchrotron
SOLEIL, Université Paris-Saclay, Saint Aubin, BP 48, 91192Gif sur Yvette, France
| | - Pavel Dudin
- Synchrotron
SOLEIL, Université Paris-Saclay, Saint Aubin, BP 48, 91192Gif sur Yvette, France
| | - Samuel Jeong
- Institute
of Applied Physics, Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba305-8573, Japan
| | - Yoshikazu Ito
- Institute
of Applied Physics, Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba305-8573, Japan
| | - Francesco Saverio Magnani
- Dipartimento
di Scienze Fisiche, Informatiche e Matematiche (FIM), Università di Modena e Reggio Emilia, 41125Modena, Italy
| | - Roberto Biagi
- Dipartimento
di Scienze Fisiche, Informatiche e Matematiche (FIM), Università di Modena e Reggio Emilia, 41125Modena, Italy
- S3,
Istituto Nanoscienze, Consiglio Nazionale
delle Ricerche (CNR), Via Campi 213/A, 41125Modena, Italy
| | - Valentina De Renzi
- Dipartimento
di Scienze Fisiche, Informatiche e Matematiche (FIM), Università di Modena e Reggio Emilia, 41125Modena, Italy
- S3,
Istituto Nanoscienze, Consiglio Nazionale
delle Ricerche (CNR), Via Campi 213/A, 41125Modena, Italy
| | - Maria Grazia Betti
- Physics
Department, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185Rome, Italy
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14
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Fu B, Zhang RW, Fan X, Li S, Ma DS, Liu CC. 2D Ladder Polyborane: An Ideal Dirac Semimetal with a Multi-Field-Tunable Band Gap. ACS NANO 2023; 17:1638-1645. [PMID: 36596227 DOI: 10.1021/acsnano.2c11612] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Hydrogen, a simple and magic element, has attracted increasing attention for its effective incorporation within solids and powerful manipulation of electronic states. Here, we show that hydrogenation tackles common problems in two-dimensional borophene, e.g., stability and applicability. As a prominent example, a ladder-like boron hydride sheet, named as 2D ladder polyborane, achieves the desired outcome, enjoying the cleanest scenario with an anisotropic and tilted Dirac cone, that can be fully depicted by a minimal two-band tight-binding model. Introducing external fields, such as an electric field or a circularly polarized light field, can effectively induce distinctive massive Dirac fermions, whereupon four types of multi-field-driven topological domain walls hosting tunable chirality and valley indexes are further established. Moreover, the 2D ladder polyborane is thermodynamically stable at room temperature and supports highly switchable Dirac fermions, providing an ideal platform for realizing and exploring the various multi-field-tunable electronic states.
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Affiliation(s)
- Botao Fu
- College of Physics and Electronic Engineering, Center for Computational Sciences, Sichuan Normal University, Chengdu, 610068, China
| | - Run-Wu Zhang
- Centre for Quantum Physics, Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE), School of Physics, Beijing Institute of Technology, Beijing, 100081, China
- Beijing Key Lab of Nanophotonics & Ultrafine Optoelectronic Systems, School of Physics, Beijing Institute of Technology, Beijing, 100081, China
| | - Xiaotong Fan
- Centre for Quantum Physics, Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE), School of Physics, Beijing Institute of Technology, Beijing, 100081, China
- Beijing Key Lab of Nanophotonics & Ultrafine Optoelectronic Systems, School of Physics, Beijing Institute of Technology, Beijing, 100081, China
| | - Si Li
- School of Physics, Northwest University, Xi'an, 710127, China
- Shaanxi Key Laboratory for Theoretical Physics Frontiers, Xi'an, 710127, China
| | - Da-Shuai Ma
- Institute for Structure and Function & Department of Physics, Chongqing University, Chongqing, 400044, China
| | - Cheng-Cheng Liu
- Centre for Quantum Physics, Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE), School of Physics, Beijing Institute of Technology, Beijing, 100081, China
- Beijing Key Lab of Nanophotonics & Ultrafine Optoelectronic Systems, School of Physics, Beijing Institute of Technology, Beijing, 100081, China
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15
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Li WB, Lin SY, Lin MF, Khuong Dien V, Lin KI. Fundamental features of AlCl 4 --/AlCl 4-graphite intercalation compounds of aluminum-ion-based battery cathodes. RSC Adv 2022; 13:281-291. [PMID: 36605661 PMCID: PMC9782379 DOI: 10.1039/d2ra06079e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2022] [Accepted: 12/07/2022] [Indexed: 12/24/2022] Open
Abstract
Up to now, many guest atoms/molecules/ions have been successfully synthesized into graphite to form various compounds. For example, alkali-atom graphite intercalation compounds are verified to reveal stage-n structures, including LiC6n and LiM8n [M = K, Rb, and Cs; n = 1, 2, 3; 4]. On the other side, AlCl4 --ion/AlCl4-molecule compounds are found to show stage-4 and stage-3 structures at room and lower temperatures, respectively. Stage-1 and stage-2 configurations, with the higher intercalant concentrations, cannot be synthesized in experimental laboratories. This might arise from the fact that it is quite difficult to build periodical arrangements along the longitudinal z and transverse directions simultaneously for large ions or molecules. Our work is mainly focused on stage-1 and stage-2 systems in terms of geometric and electronic properties. The critical features, being associated with the atom-dominated energy spectra and wave functions within the specific energy ranges, the active multi-orbital hybridization in distinct chemical bonds, and atom- & orbital-decomposed van Hove singularities, will be thoroughly clarified by the delicate simulations and analyses.
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Affiliation(s)
- Wei-Bang Li
- Department of Physics, National Cheng Kung UniversityTainanTaiwan
| | - Shih-Yang Lin
- Department of Physics, National Cheng Kung UniversityTainanTaiwan
| | - Ming-Fa Lin
- Department of Physics, National Cheng Kung UniversityTainanTaiwan,Hierarchical Green-Energy Materials (Hi-GEM) Research Center, National Cheng Kung UniversityTainanTaiwan
| | - Vo Khuong Dien
- Department of Physics, National Cheng Kung UniversityTainanTaiwan
| | - Kuang-I. Lin
- Core Facility Center, National Cheng Kung UniversityTainanTaiwan
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16
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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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17
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Wang X, Liu N, Wu Y, Qu Y, Zhang W, Wang J, Guan D, Wang S, Zheng H, Li Y, Liu C, Jia J. Strong Coupling Superconductivity in Ca-Intercalated Bilayer Graphene on SiC. NANO LETTERS 2022; 22:7651-7658. [PMID: 36066512 DOI: 10.1021/acs.nanolett.2c02804] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
The metal-intercalated bilayer graphene has a flat band with a high density of states near the Fermi energy and thus is anticipated to exhibit an enhanced strong correlation effect and associated fascinating phenomena, including superconductivity. By using a self-developed multifunctional scanning tunneling microscope, we succeeded in observing the superconducting energy gap and diamagnetic response of a Ca-intercalated bilayer graphene below a critical temperature of 8.83 K. The revealed high value of gap ratio, 2Δ/kBTc ≈ 5.0, indicates a strong coupling superconductivity, while the variation of penetration depth with temperature and magnetic field indicates an isotropic s-wave superconductor. These results provide crucial experimental clues for understanding the origin and mechanism of superconductivity in carrier-doped graphene.
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Affiliation(s)
- Xutao Wang
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, People's Republic of China
| | - Ningning Liu
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, People's Republic of China
| | - Yanfu Wu
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, People's Republic of China
| | - Yueqiao Qu
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, People's Republic of China
| | - Wenxuan Zhang
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, People's Republic of China
| | - Jinyue Wang
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, People's Republic of China
| | - Dandan Guan
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, People's Republic of China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, People's Republic of China
| | - Shiyong Wang
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, People's Republic of China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, People's Republic of China
| | - Hao Zheng
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, People's Republic of China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, People's Republic of China
| | - Yaoyi Li
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, People's Republic of China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, People's Republic of China
| | - Canhua Liu
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, People's Republic of China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, People's Republic of China
- Tsung-Dao Lee Institute, Shanghai 200240, People's Republic of China
| | - Jinfeng Jia
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, People's Republic of China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, People's Republic of China
- Tsung-Dao Lee Institute, Shanghai 200240, People's Republic of China
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18
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Ghosal C, Gruschwitz M, Koch J, Gemming S, Tegenkamp C. Proximity-Induced Gap Opening by Twisted Plumbene in Epitaxial Graphene. PHYSICAL REVIEW LETTERS 2022; 129:116802. [PMID: 36154419 DOI: 10.1103/physrevlett.129.116802] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2022] [Accepted: 08/17/2022] [Indexed: 06/16/2023]
Abstract
Besides graphene, further honeycomb 2D structures were successfully synthesized on various surfaces. However, almost flat plumbene hosting topologically protected edge states could not yet be realized. In this Letter, we investigated the intercalation of Pb on buffer layers on SiC(0001). Thereby, suspended and charge neutral graphene emerged, and the intercalated Pb formed plumbene honeycomb lattices, which are rotated by ±7.5° with respect to graphene. Along with this twist, a proximity-induced modulation of the hopping parameter in graphene opens a band gap of around 30 meV at the Fermi energy, giving rise to a metal-insulator transition. Moreover, the edges of the intercalated plumbene layers revealed edge states within the gap of the conduction bands at around 1 eV as expected for charge neutral plumbene.
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Affiliation(s)
- Chitran Ghosal
- Institut für Physik,Technische Universität Chemnitz, Reichenhainer Straße 70, 09126 Chemnitz, Germany
| | - Markus Gruschwitz
- Institut für Physik,Technische Universität Chemnitz, Reichenhainer Straße 70, 09126 Chemnitz, Germany
| | - Julian Koch
- Institut für Physik,Technische Universität Chemnitz, Reichenhainer Straße 70, 09126 Chemnitz, Germany
| | - Sibylle Gemming
- Institut für Physik,Technische Universität Chemnitz, Reichenhainer Straße 70, 09126 Chemnitz, Germany
| | - Christoph Tegenkamp
- Institut für Physik,Technische Universität Chemnitz, Reichenhainer Straße 70, 09126 Chemnitz, Germany
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19
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Li L, Zhang S, Hu G, Guo L, Wei T, Qin W, Xiang B, Zeng C, Zhang Z, Cui P. Converting a Monolayered NbSe 2 into an Ising Superconductor with Nontrivial Band Topology via Physical or Chemical Pressuring. NANO LETTERS 2022; 22:6767-6774. [PMID: 35930622 DOI: 10.1021/acs.nanolett.2c02422] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Two-dimensional transition metal dichalcogenides possessing superconductivity and strong spin-orbit coupling exhibit high in-plane upper critical fields due to Ising pairing. Yet to date, whether such systems can become topological Ising superconductors remains to be materialized. Here we show that monolayered NbSe2 can be converted into Ising superconductors with nontrivial band topology via physical or chemical pressuring. Using first-principles calculations, we first demonstrate that a hydrostatic pressure higher than 2.5 GPa can induce a p-d band inversion, rendering nontrivial band topology to NbSe2. We then illustrate that Te-doping can function as chemical pressuring in inducing nontrivial topology in NbSe2-xTex with x ≥ 0.8, due to a larger atomic radius and stronger spin-orbit coupling of Te. We also evaluate the upper critical fields within both approaches, confirming the enhanced Ising superconductivity nature, as experimentally observed. Our findings may prove to be instrumental in material realization of topological Ising superconductivity in two-dimensional systems.
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Affiliation(s)
- Leiqiang Li
- International Center for Quantum Design of Functional Materials (ICQD), and CAS Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Shunhong Zhang
- International Center for Quantum Design of Functional Materials (ICQD), and CAS Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Guojing Hu
- Department of Materials Science & Engineering, CAS Key Lab of Materials for Energy Conversion, Anhui Laboratory of Advanced Photon Science and Technology, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Linhai Guo
- International Center for Quantum Design of Functional Materials (ICQD), and CAS Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Tong Wei
- International Center for Quantum Design of Functional Materials (ICQD), and CAS Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Wei Qin
- Department of Physics, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Bin Xiang
- Department of Materials Science & Engineering, CAS Key Lab of Materials for Energy Conversion, Anhui Laboratory of Advanced Photon Science and Technology, University of Science and Technology of China, Hefei, Anhui 230026, China
- Hefei National Laboratory, University of Science and Technology of China, Hefei 230088, China
| | - Changgan Zeng
- International Center for Quantum Design of Functional Materials (ICQD), and CAS Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- Hefei National Laboratory, University of Science and Technology of China, Hefei 230088, China
| | - Zhenyu Zhang
- International Center for Quantum Design of Functional Materials (ICQD), and CAS Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- Hefei National Laboratory, University of Science and Technology of China, Hefei 230088, China
| | - Ping Cui
- International Center for Quantum Design of Functional Materials (ICQD), and CAS Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- Hefei National Laboratory, University of Science and Technology of China, Hefei 230088, China
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20
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Guo Q, Ovcharenko R, Paulus B, Dedkov Y, Voloshina E. Electronic and Magnetic Properties of The Graphene/RE/Ni(111) (RE: La, Yb) Intercalation‐Like Interfaces: A DFT Analysis. ADVANCED THEORY AND SIMULATIONS 2022. [DOI: 10.1002/adts.202100621] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Qilin Guo
- Department of Physics Shanghai University Shangda Road 99 Shanghai 200444 China
| | - Roman Ovcharenko
- Max‐Born‐Institut für Nichtlineare Optik und Kurzzeitspektroskopie Max‐Born‐Straße 2A Berlin 12489 Germany
| | - Beate Paulus
- Institut für Chemie und Biochemie Freie Universität Berlin Arnimallee 22 Berlin 14195 Germany
| | - Yuriy Dedkov
- Department of Physics Shanghai University Shangda Road 99 Shanghai 200444 China
- Centre of Excellence ENSEMBLE3 Sp.z o. o. Wolczynska Str. 133 Warsaw 01‐919 Poland
| | - Elena Voloshina
- Department of Physics Shanghai University Shangda Road 99 Shanghai 200444 China
- Institut für Chemie und Biochemie Freie Universität Berlin Arnimallee 22 Berlin 14195 Germany
- Centre of Excellence ENSEMBLE3 Sp.z o. o. Wolczynska Str. 133 Warsaw 01‐919 Poland
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21
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Rich nature of Van Hove singularities in Kagome superconductor CsV 3Sb 5. Nat Commun 2022; 13:2220. [PMID: 35468883 PMCID: PMC9038924 DOI: 10.1038/s41467-022-29828-x] [Citation(s) in RCA: 22] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2021] [Accepted: 03/30/2022] [Indexed: 11/16/2022] Open
Abstract
The recently discovered layered kagome metals AV3Sb5 (A = K, Rb, Cs) exhibit diverse correlated phenomena, which are intertwined with a topological electronic structure with multiple van Hove singularities (VHSs) in the vicinity of the Fermi level. As the VHSs with their large density of states enhance correlation effects, it is of crucial importance to determine their nature and properties. Here, we combine polarization-dependent angle-resolved photoemission spectroscopy with density functional theory to directly reveal the sublattice properties of 3d-orbital VHSs in CsV3Sb5. Four VHSs are identified around the M point and three of them are close to the Fermi level, with two having sublattice-pure and one sublattice-mixed nature. Remarkably, the VHS just below the Fermi level displays an extremely flat dispersion along MK, establishing the experimental discovery of higher-order VHS. The characteristic intensity modulation of Dirac cones around K further demonstrates the sublattice interference embedded in the kagome Fermiology. The crucial insights into the electronic structure, revealed by our work, provide a solid starting point for the understanding of the intriguing correlation phenomena in the kagome metals AV3Sb5. Predictions suggest enhanced correlation effect due to multiple van Hove singularities (VHS) in the vicinity of the Fermi level in the recently discovered AV3Sb5 kagome metals. Here the authors identify three VHSs close to the Fermi level with diverse sublattice characters in CsV3Sb5, and one of them shows flat dispersion suggesting the higher-order nature.
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22
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Hamer M, Giampietri A, Kandyba V, Genuzio F, Menteş TO, Locatelli A, Gorbachev RV, Barinov A, Mucha-Kruczyński M. Moiré Superlattice Effects and Band Structure Evolution in Near-30-Degree Twisted Bilayer Graphene. ACS NANO 2022; 16:1954-1962. [PMID: 35073479 PMCID: PMC9007532 DOI: 10.1021/acsnano.1c06439] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2021] [Accepted: 01/20/2022] [Indexed: 06/01/2023]
Abstract
In stacks of two-dimensional crystals, mismatch of their lattice constants and misalignment of crystallographic axes lead to formation of moiré patterns. We show that moiré superlattice effects persist in twisted bilayer graphene (tBLG) with large twists and short moiré periods. Using angle-resolved photoemission, we observe dramatic changes in valence band topology across large regions of the Brillouin zone, including the vicinity of the saddle point at M and across 3 eV from the Dirac points. In this energy range, we resolve several moiré minibands and detect signatures of secondary Dirac points in the reconstructed dispersions. For twists θ > 21.8°, the low-energy minigaps are not due to cone anticrossing as is the case at smaller twist angles but rather due to moiré scattering of electrons in one graphene layer on the potential of the other which generates intervalley coupling. Our work demonstrates the robustness of the mechanisms which enable engineering of electronic dispersions of stacks of two-dimensional crystals by tuning the interface twist angles. It also shows that large-angle tBLG hosts electronic minigaps and van Hove singularities of different origin which, given recent progress in extreme doping of graphene, could be explored experimentally.
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Affiliation(s)
- Matthew
J. Hamer
- Department
of Physics, University of Manchester, Oxford Road, Manchester M13 9PL, United
Kingdom
- National
Graphene Institute, University of Manchester, Booth Street East, Manchester M13 9PL, United Kingdom
| | | | | | | | | | | | - Roman V. Gorbachev
- Department
of Physics, University of Manchester, Oxford Road, Manchester M13 9PL, United
Kingdom
- National
Graphene Institute, University of Manchester, Booth Street East, Manchester M13 9PL, United Kingdom
- Henry
Royce Institute, Oxford
Road, Manchester M13 9PL, United Kingdom
| | | | - Marcin Mucha-Kruczyński
- Department
of Physics, University of Bath, Claverton Down, Bath BA2 7AY, United Kingdom
- Centre
for Nanoscience and Nanotechnology, University
of Bath, Claverton Down, Bath BA2
7AY, United Kingdom
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Gruschwitz M, Ghosal C, Shen TH, Wolff S, Seyller T, Tegenkamp C. Surface Transport Properties of Pb-Intercalated Graphene. MATERIALS 2021; 14:ma14247706. [PMID: 34947298 PMCID: PMC8705698 DOI: 10.3390/ma14247706] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/05/2021] [Revised: 12/06/2021] [Accepted: 12/09/2021] [Indexed: 11/26/2022]
Abstract
Intercalation experiments on epitaxial graphene are attracting a lot of attention at present as a tool to further boost the electronic properties of 2D graphene. In this work, we studied the intercalation of Pb using buffer layers on 6H-SiC(0001) by means of electron diffraction, scanning tunneling microscopy, photoelectron spectroscopy and in situ surface transport. Large-area intercalation of a few Pb monolayers succeeded via surface defects. The intercalated Pb forms a characteristic striped phase and leads to formation of almost charge neutral graphene in proximity to a Pb layer. The Pb intercalated layer consists of 2 ML and shows a strong structural corrugation. The epitaxial heterostructure provides an extremely high conductivity of σ=100 mS/□. However, at low temperatures (70 K), we found a metal-insulator transition that we assign to the formation of minigaps in epitaxial graphene, possibly induced by a static distortion of graphene following the corrugation of the interface layer.
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