1
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Zhai D, Lin Z, Yao W. Supersymmetry dictated topology in periodic gauge fields and realization in strained and twisted 2D materials. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2024; 87:108004. [PMID: 39241785 DOI: 10.1088/1361-6633/ad77f0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2024] [Accepted: 09/06/2024] [Indexed: 09/09/2024]
Abstract
Supersymmetry (SUSY) of a Hamiltonian dictates double degeneracy between a pair of superpartners (SPs) transformed by supercharge, except at zero energy where modes remain unpaired in many cases. Here we explore a SUSY of complete isospectrum between SPs-with paired zero modes-realized by 2D electrons in zero-flux periodic gauge fields, which can describe twisted or periodically strained 2D materials. We find their low-energy sector containing zero (or threshold) modes must be topologically non-trivial, by proving that Chern numbers of the two SPs have a finite difference dictated by the number of zero modes and energy dispersion in their vicinity. In 30° twisted bilayer (double bilayer) transition metal dichalcogenides subject to periodic strain, we find one SP is topologically trivial in its lowest miniband, while the twin SP of identical dispersion has a Chern number of 1 (2), in stark contrast to time-reversal partners that have to be simultaneously trivial or nontrivial. For systems whose physical Hamiltonian corresponds to the square root of a SUSY Hamiltonian, such as twisted or strained bilayer graphene, we reveal that topological properties of the two SUSY SPs are transferred respectively to the conduction and valence bands, including the contrasted topology in the low-energy sector and identical topology in the high-energy sector. This offers a unified perspective for understanding topological properties in many flat-band systems described by such square-root models. Both types of SUSY systems provide unique opportunities for exploring correlated and topological phases of matter.
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Affiliation(s)
- Dawei Zhai
- New Cornerstone Science Laboratory, Department of Physics, The University of Hong Kong, Hong Kong, People's Republic of China
| | - Zuzhang Lin
- New Cornerstone Science Laboratory, Department of Physics, The University of Hong Kong, Hong Kong, People's Republic of China
| | - Wang Yao
- New Cornerstone Science Laboratory, Department of Physics, The University of Hong Kong, Hong Kong, People's Republic of China
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2
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Icking E, Emmerich D, Watanabe K, Taniguchi T, Beschoten B, Lemme MC, Knoch J, Stampfer C. Ultrasteep Slope Cryogenic FETs Based on Bilayer Graphene. NANO LETTERS 2024; 24:11454-11461. [PMID: 39231534 DOI: 10.1021/acs.nanolett.4c02463] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/06/2024]
Abstract
Cryogenic field-effect transistors (FETs) offer great potential for applications, the most notable example being classical control electronics for quantum information processors. For the latter, on-chip FETs with low power consumption are crucial. This requires operating voltages in the millivolt range, which are only achievable in devices with ultrasteep subthreshold slopes. However, in conventional cryogenic metal-oxide-semiconductor (MOS)FETs based on bulk material, the experimentally achieved inverse subthreshold slopes saturate around a few mV/dec due to disorder and charged defects at the MOS interface. FETs based on two-dimensional materials offer a promising alternative. Here, we show that FETs based on Bernal stacked bilayer graphene encapsulated in hexagonal boron nitride and graphite gates exhibit inverse subthreshold slopes of down to 250 μV/dec at 0.1 K, approaching the Boltzmann limit. This result indicates an effective suppression of band tailing in van der Waals heterostructures without bulk interfaces, leading to superior device performance at cryogenic temperature.
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Affiliation(s)
- Eike Icking
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52074 Aachen, Germany
- Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, 52425 Jülich, Germany
| | - David Emmerich
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52074 Aachen, Germany
- Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, 52425 Jülich, Germany
| | - Kenji Watanabe
- Research Center for Electronic and Optical Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- Research Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Bernd Beschoten
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52074 Aachen, Germany
| | - Max C Lemme
- Chair of Electronic Devices, RWTH Aachen University, 52074 Aachen, Germany
- AMO GmbH, 52074 Aachen, Germany
| | | | - Christoph Stampfer
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52074 Aachen, Germany
- Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, 52425 Jülich, Germany
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3
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Mu L, Xing Q, Mou Y, Ma J, Wang C, Zhang J, Ma Y, Lei Y, Xie Y, Yu B, Pan C, Huang S, Yan H. Highly Tunable Interlayer Coupling and Electronic Structures of Few-Layer Graphene with Pressure. NANO LETTERS 2024. [PMID: 39259167 DOI: 10.1021/acs.nanolett.4c02035] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/12/2024]
Abstract
The interlayer electronic coupling is responsible for the electronic structure evolution from monolayer graphene to graphite and for the moiré potential in twisted bilayer graphene. Here we demonstrate that the interlayer transfer integral (hopping parameter) increases nearly 40% with a quite moderate pressure of ∼3.5 GPa, manifested by the resonance peak shift in the infrared spectra of all 2-10 L graphene. A simple model based on the Morse potential enabled us to establish the relationship between the transfer integral and pressure. Our work provides fundamental insights into the dependence of the electronic coupling on the interlayer distance.
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Affiliation(s)
- Lei Mu
- State Key Laboratory of Surface Physics, Key Laboratory of Micro- and Nano-Photonic Structures (Ministry of Education), Shanghai Key Laboratory of Metasurfaces for Light Manipulation and Department of Physics, Fudan University, Shanghai 200433, China
| | - Qiaoxia Xing
- State Key Laboratory of Surface Physics, Key Laboratory of Micro- and Nano-Photonic Structures (Ministry of Education), Shanghai Key Laboratory of Metasurfaces for Light Manipulation and Department of Physics, Fudan University, Shanghai 200433, China
| | - Yanlin Mou
- State Key Laboratory of Surface Physics, Key Laboratory of Micro- and Nano-Photonic Structures (Ministry of Education), Shanghai Key Laboratory of Metasurfaces for Light Manipulation and Department of Physics, Fudan University, Shanghai 200433, China
| | - Junwei Ma
- State Key Laboratory of Surface Physics, Key Laboratory of Micro- and Nano-Photonic Structures (Ministry of Education), Shanghai Key Laboratory of Metasurfaces for Light Manipulation and Department of Physics, Fudan University, Shanghai 200433, China
| | - Chong Wang
- 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
| | - Jiasheng Zhang
- State Key Laboratory of Surface Physics, Key Laboratory of Micro- and Nano-Photonic Structures (Ministry of Education), Shanghai Key Laboratory of Metasurfaces for Light Manipulation and Department of Physics, Fudan University, Shanghai 200433, China
| | - Yixuan Ma
- State Key Laboratory of Surface Physics, Key Laboratory of Micro- and Nano-Photonic Structures (Ministry of Education), Shanghai Key Laboratory of Metasurfaces for Light Manipulation and Department of Physics, Fudan University, Shanghai 200433, China
| | - Yuchen Lei
- State Key Laboratory of Surface Physics, Key Laboratory of Micro- and Nano-Photonic Structures (Ministry of Education), Shanghai Key Laboratory of Metasurfaces for Light Manipulation and Department of Physics, Fudan University, Shanghai 200433, China
| | - Yuangang Xie
- State Key Laboratory of Surface Physics, Key Laboratory of Micro- and Nano-Photonic Structures (Ministry of Education), Shanghai Key Laboratory of Metasurfaces for Light Manipulation and Department of Physics, Fudan University, Shanghai 200433, China
| | - Boyang Yu
- State Key Laboratory of Surface Physics, Key Laboratory of Micro- and Nano-Photonic Structures (Ministry of Education), Shanghai Key Laboratory of Metasurfaces for Light Manipulation and Department of Physics, Fudan University, Shanghai 200433, China
| | - Chenghao Pan
- State Key Laboratory of Surface Physics, Key Laboratory of Micro- and Nano-Photonic Structures (Ministry of Education), Shanghai Key Laboratory of Metasurfaces for Light Manipulation and Department of Physics, Fudan University, Shanghai 200433, China
| | - Shenyang Huang
- State Key Laboratory of Surface Physics, Key Laboratory of Micro- and Nano-Photonic Structures (Ministry of Education), Shanghai Key Laboratory of Metasurfaces for Light Manipulation and Department of Physics, Fudan University, Shanghai 200433, China
- Institute of Optoelectronics, Fudan University, Shanghai 200433, China
| | - Hugen Yan
- State Key Laboratory of Surface Physics, Key Laboratory of Micro- and Nano-Photonic Structures (Ministry of Education), Shanghai Key Laboratory of Metasurfaces for Light Manipulation and Department of Physics, Fudan University, Shanghai 200433, China
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4
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Sharma S, Gill D, Krishna J, Dewhurst JK, Shallcross S. Direct coupling of light to valley current. Nat Commun 2024; 15:7579. [PMID: 39217163 PMCID: PMC11365965 DOI: 10.1038/s41467-024-51968-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2023] [Accepted: 08/21/2024] [Indexed: 09/04/2024] Open
Abstract
The coupling of circularly polarized light to local band structure extrema ("valleys") in two dimensional semiconductors promises a new electronics based on the valley degree of freedom. Such pulses, however, couple only to valley charge and not to the valley current, precluding lightwave manipulation of this second vital element of valleytronic devices. Contradicting this established wisdom, we show that the few cycle limit of circularly polarized light is imbued with an emergent vectorial character that allows direct coupling to the valley current. The underlying physical mechanism involves the emergence of a momentum space valley dipole, the orientation and magnitude of which allows complete control over the direction and magnitude of the valley current. We demonstrate this effect via minimal tight-binding models both for the visible spectrum gaps of the transition metal dichalcogenides (generation time ~ 1 fs) as well as the infrared gaps of biased bilayer graphene ( ~ 14 fs); we further verify our findings with state-of-the-art time-dependent density functional theory incorporating transient excitonic effects. Our findings both mark a striking example of emergent physics in the ultrafast limit of light-matter coupling, as well as allowing the creation of valley currents on time scales that challenge quantum decoherence in matter.
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Affiliation(s)
- S Sharma
- Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Max-Born-Strasse 2A, 12489, Berlin, Germany.
- Institute for theoretical solid-state physics, Freie Universität Berlin, Arnimallee 14, 14195, Berlin, Germany.
| | - D Gill
- Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Max-Born-Strasse 2A, 12489, Berlin, Germany
| | - J Krishna
- Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Max-Born-Strasse 2A, 12489, Berlin, Germany
| | - J K Dewhurst
- Max-Planck-Institut für Mikrostrukturphysik Weinberg 2, D-06120, Halle, Germany
| | - S Shallcross
- Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Max-Born-Strasse 2A, 12489, Berlin, Germany.
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5
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Bhowmik S, Ghosh A, Chandni U. Emergent phases in graphene flat bands. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2024; 87:096401. [PMID: 39059412 DOI: 10.1088/1361-6633/ad67ed] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2023] [Accepted: 07/26/2024] [Indexed: 07/28/2024]
Abstract
Electronic correlations in two-dimensional materials play a crucial role in stabilising emergent phases of matter. The realisation of correlation-driven phenomena in graphene has remained a longstanding goal, primarily due to the absence of strong electron-electron interactions within its low-energy bands. In this context, magic-angle twisted bilayer graphene has recently emerged as a novel platform featuring correlated phases favoured by the low-energy flat bands of the underlying moiré superlattice. Notably, the observation of correlated insulators and superconductivity, and the interplay between these phases have garnered significant attention. A wealth of correlated phases with unprecedented tunability was discovered subsequently, including orbital ferromagnetism, Chern insulators, strange metallicity, density waves, and nematicity. However, a comprehensive understanding of these closely competing phases remains elusive. The ability to controllably twist and stack multiple graphene layers has enabled the creation of a whole new family of moiré superlattices with myriad properties. Here, we review the progress and development achieved so far, encompassing the rich phase diagrams offered by these graphene-based moiré systems. Additionally, we discuss multiple phases recently observed in non-moiré multilayer graphene systems. Finally, we outline future opportunities and challenges for the exploration of hidden phases in this new generation of moiré materials.
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Affiliation(s)
- Saisab Bhowmik
- Department of Instrumentation and Applied Physics, Indian Institute of Science, Bangalore 560012, India
| | - Arindam Ghosh
- Department of Physics, Indian Institute of Science, Bangalore 560012, India
- Centre for Nano Science and Engineering, Indian Institute of Science, Bangalore 560012, India
| | - U Chandni
- Department of Instrumentation and Applied Physics, Indian Institute of Science, Bangalore 560012, India
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6
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Lin CY, Weng DW, Chiu CW, Gumbs G. Unique electronic and optical properties of stacking-modulated bilayer graphene under external magnetic fields. Phys Chem Chem Phys 2024; 26:19316-19331. [PMID: 38963725 DOI: 10.1039/d4cp01576b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/06/2024]
Abstract
This study delves into the magneto-electronic and magneto-optical properties of stacking-modulated bilayer graphene. By manipulating domain walls (DWs) across AB-BA domains periodically, we unveil oscillatory Landau subbands and the associated optical excitations. The DWs act as periodic potentials, yielding fascinating 1D spectral features. Our exploration reveals 1D phenomena localized to Bernal stacking, DW regions, and stacking boundaries, highlighting the intriguing formation of Landau state quantization influenced by the commensuration between the magnetic length and the system. The stable quantized localization within different regions leads to the emergence of unconventional quantized subbands. This study provides valuable insights into the essential properties of stacking-modulated bilayer graphene.
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Affiliation(s)
- Chiun-Yan Lin
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
| | - Da-We Weng
- Department of Physics, National Kaohsiung Normal University, Kaohsiung 82446, Taiwan
| | - Chih-Wei Chiu
- Department of Physics, National Kaohsiung Normal University, Kaohsiung 82446, Taiwan
| | - Godfrey Gumbs
- Department of Physics and Astronomy, Hunter College of the City University of New York, 695 Park Avenue, New York, NY 10065, USA.
- The Graduate School and University Center, The City University of New York, 365 Fifth Avenue, New York, NY 10016, USA
- Donostia International Physics Center (DIPC), P de Manuel Lardizabal, 4, 20018 San Sebastian, Basque Country, Spain
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7
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Castro M, Saéz G, Vergara Apaz P, Allende S, Nunez AS. Toward Fully Multiferroic van der Waals SpinFETs: Basic Design and Quantum Calculations. NANO LETTERS 2024; 24:7911-7918. [PMID: 38889449 DOI: 10.1021/acs.nanolett.4c01146] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/20/2024]
Abstract
Manipulating spin transport enhances the functionality of electronic devices, allowing them to surpass physical constraints related to speed and power. For this reason, the use of van der Waals multiferroics at the interface of heterostructures offers promising prospects for developing high-performance devices, enabling the electrical control of spin information. Our work focuses primarily on a mechanism for multiferroicity in two-dimensional van der Waals materials that stems from an interplay between antiferromagnetism and the breaking of inversion symmetry in certain bilayers. We provide evidence for spin-electrical couplings that include manipulating van der Waals multiferroic edges via external voltages and the subsequent control of spin transport including for fully multiferroic spin field-effect transistors.
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Affiliation(s)
- Mario Castro
- Departamento de Física, FCFM, Universidad de Chile, Santiago, 8370448, Chile
- Centro de Nanociencia y Nanotecnología CEDENNA, Santiago, 9170124, Chile
| | - Guidobeth Saéz
- Departamento de Física, FCFM, Universidad de Chile, Santiago, 8370448, Chile
- Centro de Nanociencia y Nanotecnología CEDENNA, Santiago, 9170124, Chile
| | | | - Sebastián Allende
- Centro de Nanociencia y Nanotecnología CEDENNA, Santiago, 9170124, Chile
- Departamento de Física, Universidad de Santiago de Chile, Santiago, 9170124, Chile
| | - Alvaro S Nunez
- Departamento de Física, FCFM, Universidad de Chile, Santiago, 8370448, Chile
- Centro de Nanociencia y Nanotecnología CEDENNA, Santiago, 9170124, Chile
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Chakraborti H, Gorini C, Knothe A, Liu MH, Makk P, Parmentier FD, Perconte D, Richter K, Roulleau P, Sacépé B, Schönenberger C, Yang W. Electron wave and quantum optics in graphene. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2024; 36:393001. [PMID: 38697131 DOI: 10.1088/1361-648x/ad46bc] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2023] [Accepted: 05/01/2024] [Indexed: 05/04/2024]
Abstract
In the last decade, graphene has become an exciting platform for electron optical experiments, in some aspects superior to conventional two-dimensional electron gases (2DEGs). A major advantage, besides the ultra-large mobilities, is the fine control over the electrostatics, which gives the possibility of realising gap-less and compact p-n interfaces with high precision. The latter host non-trivial states,e.g., snake states in moderate magnetic fields, and serve as building blocks of complex electron interferometers. Thanks to the Dirac spectrum and its non-trivial Berry phase, the internal (valley and sublattice) degrees of freedom, and the possibility to tailor the band structure using proximity effects, such interferometers open up a completely new playground based on novel device architectures. In this review, we introduce the theoretical background of graphene electron optics, fabrication methods used to realise electron-optical devices, and techniques for corresponding numerical simulations. Based on this, we give a comprehensive review of ballistic transport experiments and simple building blocks of electron optical devices both in single and bilayer graphene, highlighting the novel physics that is brought in compared to conventional 2DEGs. After describing the different magnetic field regimes in graphene p-n junctions and nanostructures, we conclude by discussing the state of the art in graphene-based Mach-Zender and Fabry-Perot interferometers.
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Affiliation(s)
| | - Cosimo Gorini
- Université Paris-Saclay, CEA, CNRS, SPEC, 91191 Gif-sur-Yvette, France
| | - Angelika Knothe
- Institut für Theoretische Physik, Universität Regensburg, D-93040 Regensburg, Germany
| | - Ming-Hao Liu
- Department of Physics and Center for Quantum Frontiers of Research and Technology (QFort), National Cheng Kung University, Tainan 70101, Taiwan
| | - Péter Makk
- Department of Physics, Institute of Physics, Budapest University of Technology and Economics, Műegyetem rkp. 3., Budapest H-1111, Hungary
- MTA-BME Correlated van der Waals Structures Momentum Research Group, Műegyetem rkp. 3., Budapest H-1111, Hungary
| | | | - David Perconte
- Université Grenoble Alpes, CNRS, Grenoble INP, Institut Néel, 38000 Grenoble, France
| | - Klaus Richter
- Institut für Theoretische Physik, Universität Regensburg, D-93040 Regensburg, Germany
| | - Preden Roulleau
- Université Paris-Saclay, CEA, CNRS, SPEC, 91191 Gif-sur-Yvette, France
| | - Benjamin Sacépé
- Université Grenoble Alpes, CNRS, Grenoble INP, Institut Néel, 38000 Grenoble, France
| | | | - Wenmin Yang
- Université Grenoble Alpes, CNRS, Grenoble INP, Institut Néel, 38000 Grenoble, France
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Li C, Xu F, Li B, Li J, Li G, Watanabe K, Taniguchi T, Tong B, Shen J, Lu L, Jia J, Wu F, Liu X, Li T. Tunable superconductivity in electron- and hole-doped Bernal bilayer graphene. Nature 2024; 631:300-306. [PMID: 38898282 DOI: 10.1038/s41586-024-07584-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2023] [Accepted: 05/17/2024] [Indexed: 06/21/2024]
Abstract
Graphene-based, high-quality, two-dimensional electronic systems have emerged as a highly tunable platform for studying superconductivity1-21. Specifically, superconductivity has been observed in both electron- and hole-doped twisted graphene moiré systems1-17, whereas in crystalline graphene systems, superconductivity has so far been observed only in hole-doped rhombohedral trilayer graphene (RTG)18 and hole-doped Bernal bilayer graphene (BBG)19-21. Recently, enhanced superconductivity has been demonstrated20,21 in BBG because of the proximity to a monolayer WSe2. Here we report the observation of superconductivity and a series of flavour-symmetry-breaking phases in electron- and hole-doped BBG/WSe2 devices by electrostatic doping. The strength of the observed superconductivity is tunable by applied vertical electric fields. The maximum Berezinskii-Kosterlitz-Thouless transition temperature for the electron- and hole-doped superconductivity is about 210 mK and 400 mK, respectively. Superconductivities emerge only when the applied electric fields drive the BBG electron or hole wavefunctions towards the WSe2 layer, underscoring the importance of the WSe2 layer in the observed superconductivity. The hole-doped superconductivity violates the Pauli paramagnetic limit, consistent with an Ising-like superconductor. By contrast, the electron-doped superconductivity obeys the Pauli limit, although the proximity-induced Ising spin-orbit coupling is also notable in the conduction band. Our findings highlight the rich physics associated with the conduction band in BBG, paving the way for further studies into the superconducting mechanisms of crystalline graphene and the development of superconductor devices based on BBG.
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Affiliation(s)
- Chushan Li
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, China
- Tsung-Dao Lee Institute, Shanghai Jiao Tong University, Shanghai, China
| | - Fan Xu
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, China
| | - Bohao Li
- School of Physics and Technology, Wuhan University, Wuhan, China
| | - Jiayi Li
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, China
| | - Guoan Li
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, China
| | - Kenji Watanabe
- Research Center for Electronic and Optical Materials, National Institute for Materials Science, Tsukuba, Japan
| | - Takashi Taniguchi
- Research Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Japan
| | - Bingbing Tong
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, China
| | - Jie Shen
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, China
| | - Li Lu
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, China
- Hefei National Laboratory, Hefei, China
| | - Jinfeng Jia
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, China
- Tsung-Dao Lee Institute, Shanghai Jiao Tong University, Shanghai, China
- Hefei National Laboratory, Hefei, China
- Shanghai Research Center for Quantum Sciences, Shanghai, China
| | - Fengcheng Wu
- School of Physics and Technology, Wuhan University, Wuhan, China.
- Wuhan Institute of Quantum Technology, Wuhan, China.
| | - Xiaoxue Liu
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, China.
- Tsung-Dao Lee Institute, Shanghai Jiao Tong University, Shanghai, China.
- Hefei National Laboratory, Hefei, China.
- Shanghai Research Center for Quantum Sciences, Shanghai, China.
| | - Tingxin Li
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, China.
- Tsung-Dao Lee Institute, Shanghai Jiao Tong University, Shanghai, China.
- Hefei National Laboratory, Hefei, China.
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10
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Zhou Y, Bauer RA, Zhang X, Hong N, Verweij H. Swelling of Thin Graphene Oxide Film in Water Vapor Studied by In Situ Spectroscopic Ellipsometry. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024; 40:12497-12503. [PMID: 38836692 DOI: 10.1021/acs.langmuir.4c00897] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2024]
Abstract
Graphene oxide (GO) is obtained by the chemical treatment of graphene sheets, resulting in decoration with oxygen-containing functional groups. In the work presented here, we examined marked changes that occur in a thin film of parallel aligned GO sheets when exposed to water vapor at various pressures. It was found that exceptionally fast and substantial water uptake and release occur that is accompanied by major changes in GO interlayer spacing. These characteristics were obtained in situ with spectroscopic ellipsometry. At 99% relative humidity (RH) and 25 °C, the interlayer spacing became 1.41 nm, which recovers to ∼0.8 nm within 30 s when exposed to 10% RH. Besides layer thickness values, uniaxial optical constants for the GO vs RH were derived from the ellipsometry data. Molar refraction theory was applied that indicated monolayer water formation at ∼91% RH at 25 °C upon water adsorption. Our findings contribute to the understanding of the interaction between GO and its environment. The very outspoken effect of external water vapor pressure on GO water content, interlayer spacing, and optical properties can be utilized in sensing and separation devices, subnanometer positioning, chemical switches, and environmentally aware materials.
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Affiliation(s)
- Yi Zhou
- Department of Materials Science and Engineering, The Ohio State University, Suite 2136, Mars G. Fontana Laboratories, 140 W 19th Avenue, Columbus, Ohio 43210, United States
| | - Ralph A Bauer
- Global R&D Inc., 539 Industrial Mile Road, Columbus, Ohio 43228, United States
| | - Xin Zhang
- State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing Tech University, 30 South Puzhu Road, Nanjing 211816, P. R. China
| | - Nina Hong
- J.A. Woollam Co. Inc., 311 South seventh Street, Lincoln, Nebraska 68508, United States
| | - Hendrik Verweij
- Department of Materials Science and Engineering, The Ohio State University, Suite 2136, Mars G. Fontana Laboratories, 140 W 19th Avenue, Columbus, Ohio 43210, United States
- State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing Tech University, 30 South Puzhu Road, Nanjing 211816, P. R. China
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11
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Klanurak I, Watanabe K, Taniguchi T, Chatraphorn S, Taychatanapat T. Probing the Anisotropic Fermi Surface in Tetralayer Graphene via Transverse Magnetic Focusing. NANO LETTERS 2024; 24:6330-6336. [PMID: 38723237 PMCID: PMC11140744 DOI: 10.1021/acs.nanolett.4c01133] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2024] [Revised: 05/04/2024] [Accepted: 05/08/2024] [Indexed: 05/15/2024]
Abstract
Bernal-stacked tetralayer graphene (4LG) exhibits intriguing low-energy properties, featuring two massive sub-bands and showcasing diverse features of topologically distinct, anisotropic Fermi surfaces, including Lifshitz transitions and trigonal warping. Here, we study the influence of the band structure on electron dynamics within 4LG using transverse magnetic focusing. Our analysis reveals two distinct focusing peaks corresponding to the two sub-bands. Furthermore, we uncover a pronounced dependence of the focusing spectra on crystal orientations, indicative of an anisotropic Fermi surface. Utilizing the semiclassical model, we attribute this orientation-dependent behavior to the trigonal warping of the band structure. This phenomenon leads to variations in electron trajectories based on crystal orientation. Our findings not only enhance our understanding of the dynamics of electrons in 4LG but also offer a promising method for probing anisotropic Fermi surfaces in other materials.
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Affiliation(s)
- Illias Klanurak
- Department
of Physics, Faculty of Science, Chulalongkorn
University, Patumwan, Bangkok 10330, Thailand
| | - Kenji Watanabe
- Research
Center for Electronic and Optical Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- Research
Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Sojiphong Chatraphorn
- Department
of Physics, Faculty of Science, Chulalongkorn
University, Patumwan, Bangkok 10330, Thailand
| | - Thiti Taychatanapat
- Department
of Physics, Faculty of Science, Chulalongkorn
University, Patumwan, Bangkok 10330, Thailand
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12
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Logrado AL, Cassiano TDSA, da Cunha WF, Gargano R, E Silva GM, de Oliveira Neto PH. Width effects on bilayer graphene nanoribbon polarons. Phys Chem Chem Phys 2024; 26:14948-14959. [PMID: 38739011 DOI: 10.1039/d4cp00760c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/14/2024]
Abstract
Recent progress in nanoelectronics suggests that stacking armchair graphene nanoribbons (AGNRs) into bilayer systems can generate materials with emergent quasiparticle properties. In this context, the impact of width changes is especially relevant. However, its effect on charged carriers remains elusive. In this work, we investigate the effect of width and interlayer interaction changes on polaron states via a hybrid Hamiltonian that couples the electronic and lattice interactions. Results show the rising of two interlayer polarons: the non-symmetric and the symmetric. The coupling strength needed to induce the transition between states depends on the nanoribbon width, being at the most extreme case of ≈174 meV. Electronic properties such as the coupling strength threshold, carrier size, and gap are shown to respect the AGNR width family 3p, 3p + 1, and 3p + 2 rule. The findings demonstrate that strong interlayer interaction simultaneously delocalizes the carriers and reduces the gap up to 0.6 eV. Additionally, it is found that some layers are more prone to share charge, indicating a potential heterogeneous stacking where a particular electronic pathway is favored. The results present an encouraging prospect for integrating AGNR bilayers in future flexible electronics.
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Affiliation(s)
- André Lima Logrado
- Institute of Physics, University of Brasília, 70919-970, Brasília, Brazil.
| | | | | | - Ricardo Gargano
- Institute of Physics, University of Brasília, 70919-970, Brasília, Brazil.
| | | | - Pedro Henrique de Oliveira Neto
- Institute of Physics, University of Brasília, 70919-970, Brasília, Brazil.
- International Center of Physics, University of Brasília, 70919-970, Brazil
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13
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Zhong J, Zhang S, Duan J, Peng H, Feng Q, Hu Y, Wang Q, Mao J, Liu J, Yao Y. Effective Manipulation of a Colossal Second-Order Transverse Response in an Electric-Field-Tunable Graphene Moiré System. NANO LETTERS 2024; 24:5791-5798. [PMID: 38695400 DOI: 10.1021/acs.nanolett.4c00933] [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
The second-order nonlinear transport illuminates a frequency-doubling response emerging in quantum materials with a broken inversion symmetry. The two principal driving mechanisms, the Berry curvature dipole and the skew scattering, reflect various information including ground-state symmetries, band dispersions, and topology of electronic wave functions. However, effective manipulation of them in a single system has been lacking, hindering the pursuit of strong responses. Here, we report on the effective manipulation of the two mechanisms in a single graphene moiré superlattice, AB-BA stacked twisted double bilayer graphene. Most saliently, by virtue of the high tunability of moiré band structures and scattering rates, a record-high second-order transverse conductivity ∼ 510 μm S V-1 is observed, which is orders of magnitude higher than any reported values in the literature. Our findings establish the potential of electrically tunable graphene moiré systems for nonlinear transport manipulations and applications.
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Affiliation(s)
- Jinrui Zhong
- Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE), School of Physics, Beijing Institute of Technology, Beijing 100086, China
| | - Shihao Zhang
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
- School of Physics and Electronics, Hunan University, Changsha 410082, China
| | - Junxi Duan
- Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE), School of Physics, Beijing Institute of Technology, Beijing 100086, China
| | - Huimin Peng
- Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE), School of Physics, Beijing Institute of Technology, Beijing 100086, China
| | - Qi Feng
- Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE), School of Physics, Beijing Institute of Technology, Beijing 100086, China
| | - Yuqing Hu
- Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE), School of Physics, Beijing Institute of Technology, Beijing 100086, China
| | - Qinsheng Wang
- Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE), School of Physics, Beijing Institute of Technology, Beijing 100086, China
| | - Jinhai Mao
- School of Physical Sciences and CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Jianpeng Liu
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
- ShanghaiTech Laboratory for Topological Physics, ShanghaiTech University, Shanghai 201210, China
| | - Yugui Yao
- Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE), School of Physics, Beijing Institute of Technology, Beijing 100086, China
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14
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Zhou BT, Pathak V, Franz M. Quantum-Geometric Origin of Out-of-Plane Stacking Ferroelectricity. PHYSICAL REVIEW LETTERS 2024; 132:196801. [PMID: 38804928 DOI: 10.1103/physrevlett.132.196801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2023] [Revised: 11/16/2023] [Accepted: 04/10/2024] [Indexed: 05/29/2024]
Abstract
Stacking ferroelectricity (SFE) has been discovered in a wide range of van der Waals materials and holds promise for applications, including photovoltaics and high-density memory devices. We show that the microscopic origin of out-of-plane stacking ferroelectric polarization can be generally understood as a consequence of a nontrivial Berry phase borne out of an effective Su-Schrieffer-Heeger model description with broken sublattice symmetry, thus elucidating the quantum-geometric origin of polarization in the extremely nonperiodic bilayer limit. Our theory applies to known stacking ferroelectrics such as bilayer transition-metal dichalcogenides in 3R and T_{d} phases, as well as general AB-stacked honeycomb bilayers with staggered sublattice potential. Our explanatory and self-consistent framework based on the quantum-geometric perspective establishes quantitative understanding of out-of-plane SFE materials beyond symmetry principles.
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Affiliation(s)
- Benjamin T Zhou
- Department of Physics and Astronomy & Stewart Blusson Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
| | - Vedangi Pathak
- Department of Physics and Astronomy & Stewart Blusson Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
| | - Marcel Franz
- Department of Physics and Astronomy & Stewart Blusson Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
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15
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Qing F, Guo X, Hou Y, Ning C, Wang Q, Li X. Toward the Production of Super Graphene. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2024:e2310678. [PMID: 38708801 DOI: 10.1002/smll.202310678] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2023] [Revised: 04/10/2024] [Indexed: 05/07/2024]
Abstract
The quality requirements of graphene depend on the applications. Some have a high tolerance for graphene quality and even require some defects, while others require graphene as perfect as possible to achieve good performance. So far, synthesis of large-area graphene films by chemical vapor deposition of carbon precursors on metal substrates, especially on Cu, remains the main way to produce high-quality graphene, which has been significantly developed in the past 15 years. However, although many prototypes are demonstrated, their performance is still more or less far from the theoretical property limit of graphene. This review focuses on how to make super graphene, namely graphene with a perfect structure and free of contaminations. More specially, this study focuses on graphene synthesis on Cu substrates. Typical defects in graphene are first discussed together with the formation mechanisms and how they are characterized normally, followed with a brief review of graphene properties and the effects of defects. Then, the synthesis progress of super graphene from the aspects of substrate, grain size, wrinkles, contamination, adlayers, and point defects are reviewed. Graphene transfer is briefly discussed as well. Finally, the challenges to make super graphene are discussed and a strategy is proposed.
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Affiliation(s)
- Fangzhu Qing
- School of Integrated Circuit Science and Engineering (Exemplary School of Microelectronics), University of Electronic Science and Technology of China, Chengdu, 611731, China
- State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 611731, China
- Shenzhen Institute for Advanced Study, University of Electronic Science and Technology of China, Shenzhen, 518110, China
| | - Xiaomeng Guo
- School of Integrated Circuit Science and Engineering (Exemplary School of Microelectronics), University of Electronic Science and Technology of China, Chengdu, 611731, China
| | - Yuting Hou
- School of Integrated Circuit Science and Engineering (Exemplary School of Microelectronics), University of Electronic Science and Technology of China, Chengdu, 611731, China
| | - Congcong Ning
- School of Integrated Circuit Science and Engineering (Exemplary School of Microelectronics), University of Electronic Science and Technology of China, Chengdu, 611731, China
| | - Qisong Wang
- School of Integrated Circuit Science and Engineering (Exemplary School of Microelectronics), University of Electronic Science and Technology of China, Chengdu, 611731, China
| | - Xuesong Li
- School of Integrated Circuit Science and Engineering (Exemplary School of Microelectronics), University of Electronic Science and Technology of China, Chengdu, 611731, China
- State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 611731, China
- Shenzhen Institute for Advanced Study, University of Electronic Science and Technology of China, Shenzhen, 518110, China
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16
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Maji K, Sarkar J, Mandal S, H S, Hingankar M, Mukherjee A, Samal S, Bhattacharjee A, Patankar MP, Watanabe K, Taniguchi T, Deshmukh MM. Superconducting Cavity-Based Sensing of Band Gaps in 2D Materials. NANO LETTERS 2024; 24:4369-4375. [PMID: 38393831 DOI: 10.1021/acs.nanolett.3c04990] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/25/2024]
Abstract
The superconducting coplanar waveguide (SCPW) cavity plays an essential role in various areas like superconducting qubits, parametric amplifiers, radiation detectors, and studying magnon-photon and photon-phonon coupling. Despite its wide-ranging applications, the use of SCPW cavities to study various van der Waals 2D materials has been relatively unexplored. The resonant modes of the SCPW cavity exquisitely sense the dielectric environment. In this work, we measure the charge compressibility of bilayer graphene coupled to a half-wavelength SCPW cavity. Our approach provides a means to detect subtle changes in the capacitance of the bilayer graphene heterostructure, which depends on the compressibility of bilayer graphene, manifesting as shifts in the resonant frequency of the cavity. This method holds promise for exploring a wide class of van der Waals 2D materials, including transition metal dichalcogenides (TMDs) and their moiré, where DC transport measurement is challenging.
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Affiliation(s)
- Krishnendu Maji
- Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400005, India
| | - Joydip Sarkar
- Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400005, India
| | - Supriya Mandal
- Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400005, India
| | - Sriram H
- Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400005, India
| | - Mahesh Hingankar
- Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400005, India
| | - Ayshi Mukherjee
- Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400005, India
| | - Soumyajit Samal
- Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400005, India
| | - Anirban Bhattacharjee
- Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400005, India
| | - Meghan P Patankar
- Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400005, India
| | - 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
| | - Mandar M Deshmukh
- Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400005, India
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17
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Seiler AM, Jacobsen N, Statz M, Fernandez N, Falorsi F, Watanabe K, Taniguchi T, Dong Z, Levitov LS, Weitz RT. Probing the tunable multi-cone band structure in Bernal bilayer graphene. Nat Commun 2024; 15:3133. [PMID: 38605052 PMCID: PMC11009389 DOI: 10.1038/s41467-024-47342-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2024] [Accepted: 03/27/2024] [Indexed: 04/13/2024] Open
Abstract
Bernal bilayer graphene (BLG) offers a highly flexible platform for tuning the band structure, featuring two distinct regimes. One is a tunable band gap induced by large displacement fields. Another is a gapless metallic band occurring at low fields, featuring rich fine structure consisting of four linearly dispersing Dirac cones and van Hove singularities. Even though BLG has been extensively studied experimentally, the evidence of this band structure is still elusive, likely due to insufficient energy resolution. Here, we use Landau levels as markers of the energy dispersion and analyze the Landau level spectrum in a regime where the cyclotron orbits of electrons or holes in momentum space are small enough to resolve the distinct mini Dirac cones. We identify the presence of four Dirac cones and map out topological transitions induced by displacement field. By clarifying the low-energy properties of BLG bands, these findings provide a valuable addition to the toolkit for graphene electronics.
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Affiliation(s)
- Anna M Seiler
- 1st Physical Institute, Faculty of Physics, University of Göttingen, Friedrich-Hund-Platz 1, Göttingen, Germany
| | - Nils Jacobsen
- 1st Physical Institute, Faculty of Physics, University of Göttingen, Friedrich-Hund-Platz 1, Göttingen, Germany
| | - Martin Statz
- 1st Physical Institute, Faculty of Physics, University of Göttingen, Friedrich-Hund-Platz 1, Göttingen, Germany
| | - Noelia Fernandez
- 1st Physical Institute, Faculty of Physics, University of Göttingen, Friedrich-Hund-Platz 1, Göttingen, Germany
| | - Francesca Falorsi
- 1st Physical Institute, Faculty of Physics, University of Göttingen, Friedrich-Hund-Platz 1, Göttingen, Germany
| | - Kenji Watanabe
- Research Center for Electronic and Optical Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Japan
| | - Takashi Taniguchi
- Research Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Japan
| | - Zhiyu Dong
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
| | - Leonid S Levitov
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
| | - R Thomas Weitz
- 1st Physical Institute, Faculty of Physics, University of Göttingen, Friedrich-Hund-Platz 1, Göttingen, Germany.
- International Center for Advanced Studies of Energy Conversion (ICASEC), University of Göttingen, Göttingen, Germany.
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18
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Wang T, Vila M, Zaletel MP, Chatterjee S. Electrical Control of Spin and Valley in Spin-Orbit Coupled Graphene Multilayers. PHYSICAL REVIEW LETTERS 2024; 132:116504. [PMID: 38563932 DOI: 10.1103/physrevlett.132.116504] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/11/2023] [Revised: 01/30/2024] [Accepted: 02/20/2024] [Indexed: 04/04/2024]
Abstract
Electrical control of magnetism has been a major technological pursuit of the spintronics community, owing to its far-reaching implications for data storage and transmission. Here, we propose and analyze a new mechanism for electrical switching of isospin, using chiral-stacked graphene multilayers, such as Bernal bilayer graphene or rhombohedral trilayer graphene, encapsulated by transition metal dichalcogenide (TMD) substrates. Leveraging the proximity-induced spin-orbit coupling from the TMD, we demonstrate electrical switching of correlation-induced spin and/or valley polarization, by reversing a perpendicular displacement field or the chemical potential. We substantiate our proposal with both analytical arguments and self-consistent Hartree-Fock numerics. Finally, we illustrate how the relative alignment of the TMDs, together with the top and bottom gate voltages, can be used to selectively switch distinct isospin flavors, putting forward correlated Van der Waals heterostructures as a promising platform for spintronics and valleytronics.
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Affiliation(s)
- Taige Wang
- Department of Physics, University of California, Berkeley, California 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Marc Vila
- Department of Physics, University of California, Berkeley, California 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Michael P Zaletel
- Department of Physics, University of California, Berkeley, California 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Shubhayu Chatterjee
- Department of Physics, University of California, Berkeley, California 94720, USA
- Department of Physics, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
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19
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Graziotto L, Macheda F, Venanzi T, Marchese G, Sotgiu S, Ouaj T, Stellino E, Fasolato C, Postorino P, Metzelaars M, Kögerler P, Beschoten B, Calandra M, Ortolani M, Stampfer C, Mauri F, Baldassarre L. Infrared Resonance Raman of Bilayer Graphene: Signatures of Massive Fermions and Band Structure on the 2D Peak. NANO LETTERS 2024; 24:1867-1873. [PMID: 38306119 DOI: 10.1021/acs.nanolett.3c03502] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2024]
Abstract
Few-layer graphene possesses low-energy carriers that behave as massive Fermions, exhibiting intriguing properties in both transport and light scattering experiments. Lowering the excitation energy of resonance Raman spectroscopy down to 1.17 eV, we target these massive quasiparticles in the split bands close to the K point. The low excitation energy weakens some of the Raman processes that are resonant in the visible, and induces a clearer frequency-separation of the substructures of the resonance 2D peak in bi- and trilayer samples. We follow the excitation-energy dependence of the intensity of each substructure, and comparing experimental measurements on bilayer graphene with ab initio theoretical calculations, we trace back such modifications on the joint effects of probing the electronic dispersion close to the band splitting and enhancement of electron-phonon matrix elements.
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Affiliation(s)
- Lorenzo Graziotto
- Department of Physics, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Rome, Italy
| | - Francesco Macheda
- Department of Physics, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Rome, Italy
- Istituto Italiano di Tecnologia, Graphene Labs, Via Morego 30, 16163 Genoa, Italy
| | - Tommaso Venanzi
- Department of Physics, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Rome, Italy
| | - Guglielmo Marchese
- Department of Physics, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Rome, Italy
| | - Simone Sotgiu
- Department of Physics, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Rome, Italy
| | - Taoufiq Ouaj
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52074 Aachen, Germany
| | - Elena Stellino
- Department of Physics and Geology, University of Perugia, Via Alessandro Pascoli, 06123 Perugia, Italy
| | - Claudia Fasolato
- Institute for Complex Systems, National Research Council (ISC-CNR), 00185 Rome, Italy
| | - Paolo Postorino
- Department of Physics, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Rome, Italy
| | - Marvin Metzelaars
- Institute of Inorganic Chemistry, RWTH Aachen University, 52074 Aachen, Germany
| | - Paul Kögerler
- Institute of Inorganic Chemistry, RWTH Aachen University, 52074 Aachen, Germany
| | - Bernd Beschoten
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52074 Aachen, Germany
| | - Matteo Calandra
- Istituto Italiano di Tecnologia, Graphene Labs, Via Morego 30, 16163 Genoa, Italy
- Department of Physics, University of Trento, Via Sommarive 14, 38123 Povo, Italy
| | - Michele Ortolani
- Department of Physics, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Rome, Italy
| | - Christoph Stampfer
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52074 Aachen, Germany
| | - Francesco Mauri
- Department of Physics, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Rome, Italy
- Istituto Italiano di Tecnologia, Graphene Labs, Via Morego 30, 16163 Genoa, Italy
| | - Leonetta Baldassarre
- Department of Physics, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Rome, Italy
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20
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Bocarsly M, Uzan M, Roy I, Grover S, Xiao J, Dong Z, Labendik M, Uri A, Huber ME, Myasoedov Y, Watanabe K, Taniguchi T, Yan B, Levitov LS, Zeldov E. De Haas-van Alphen spectroscopy and magnetic breakdown in moiré graphene. Science 2024; 383:42-48. [PMID: 38175887 DOI: 10.1126/science.adh3499] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2023] [Accepted: 11/23/2023] [Indexed: 01/06/2024]
Abstract
Quantum oscillations originating from the quantization of electron cyclotron orbits provide sensitive diagnostics of electron bands and interactions. We report on nanoscale imaging of the thermodynamic magnetization oscillations caused by the de Haas-van Alphen effect in moiré graphene. Scanning by means of superconducting quantum interference device (SQUID)-on-tip in Bernal bilayer graphene crystal axis-aligned to hexagonal boron nitride reveals large magnetization oscillations with amplitudes reaching 500 Bohr magneton per electron in weak magnetic fields, unexpectedly low frequencies, and high sensitivity to superlattice filling fraction. The oscillations allow us to reconstruct the complex band structure, revealing narrow moiré bands with multiple overlapping Fermi surfaces separated by unusually small momentum gaps. We identified sets of oscillations that violate the textbook Onsager Fermi surface sum rule, signaling formation of broad-band particle-hole superposition states induced by coherent magnetic breakdown.
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Affiliation(s)
- Matan Bocarsly
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Matan Uzan
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Indranil Roy
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Sameer Grover
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Jiewen Xiao
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Zhiyu Dong
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Mikhail Labendik
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Aviram Uri
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Martin E Huber
- Departments of Physics and Electrical Engineering, University of Colorado Denver, Denver, CO 80217, USA
| | - Yuri Myasoedov
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Kenji Watanabe
- Research Center for Electronic and Optical Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- Research Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Binghai Yan
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Leonid S Levitov
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Eli Zeldov
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 7610001, Israel
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21
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Hecker K, Banszerus L, Schäpers A, Möller S, Peters A, Icking E, Watanabe K, Taniguchi T, Volk C, Stampfer C. Coherent charge oscillations in a bilayer graphene double quantum dot. Nat Commun 2023; 14:7911. [PMID: 38036517 PMCID: PMC10689829 DOI: 10.1038/s41467-023-43541-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2023] [Accepted: 11/13/2023] [Indexed: 12/02/2023] Open
Abstract
The coherent dynamics of a quantum mechanical two-level system passing through an anti-crossing of two energy levels can give rise to Landau-Zener-Stückelberg-Majorana (LZSM) interference. LZSM interference spectroscopy has proven to be a fruitful tool to investigate charge noise and charge decoherence in semiconductor quantum dots (QDs). Recently, bilayer graphene has developed as a promising platform to host highly tunable QDs potentially useful for hosting spin and valley qubits. So far, in this system no coherent oscillations have been observed and little is known about charge noise in this material. Here, we report coherent charge oscillations and [Formula: see text] charge decoherence times in a bilayer graphene double QD. The charge decoherence times are measured independently using LZSM interference and photon assisted tunneling. Both techniques yield [Formula: see text] average values in the range of 400-500 ps. The observation of charge coherence allows to study the origin and spectral distribution of charge noise in future experiments.
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Affiliation(s)
- K Hecker
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52074, Aachen, Germany.
- Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, 52425, Jülich, Germany.
| | - L Banszerus
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52074, Aachen, Germany
- Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, 52425, Jülich, Germany
| | - A Schäpers
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52074, Aachen, Germany
| | - S Möller
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52074, Aachen, Germany
- Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, 52425, Jülich, Germany
| | - A Peters
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52074, Aachen, Germany
| | - E Icking
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52074, Aachen, Germany
- Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, 52425, Jülich, Germany
| | - K Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - T Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - C Volk
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52074, Aachen, Germany
- Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, 52425, Jülich, Germany
| | - C Stampfer
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52074, Aachen, Germany
- Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, 52425, Jülich, Germany
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22
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Naumis GG, Herrera SA, Poudel SP, Nakamura H, Barraza-Lopez S. Mechanical, electronic, optical, piezoelectric and ferroic properties of strained graphene and other strained monolayers and multilayers: an update. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2023; 87:016502. [PMID: 37879327 DOI: 10.1088/1361-6633/ad06db] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2023] [Accepted: 10/25/2023] [Indexed: 10/27/2023]
Abstract
This is an update of a previous review (Naumiset al2017Rep. Prog. Phys.80096501). Experimental and theoretical advances for straining graphene and other metallic, insulating, ferroelectric, ferroelastic, ferromagnetic and multiferroic 2D materials were considered. We surveyed (i) methods to induce valley and sublattice polarisation (P) in graphene, (ii) time-dependent strain and its impact on graphene's electronic properties, (iii) the role of local and global strain on superconductivity and other highly correlated and/or topological phases of graphene, (iv) inducing polarisationPon hexagonal boron nitride monolayers via strain, (v) modifying the optoelectronic properties of transition metal dichalcogenide monolayers through strain, (vi) ferroic 2D materials with intrinsic elastic (σ), electric (P) and magnetic (M) polarisation under strain, as well as incipient 2D multiferroics and (vii) moiré bilayers exhibiting flat electronic bands and exotic quantum phase diagrams, and other bilayer or few-layer systems exhibiting ferroic orders tunable by rotations and shear strain. The update features the experimental realisations of a tunable two-dimensional Quantum Spin Hall effect in germanene, of elemental 2D ferroelectric bismuth, and 2D multiferroic NiI2. The document was structured for a discussion of effects taking place in monolayers first, followed by discussions concerning bilayers and few-layers, and it represents an up-to-date overview of exciting and newest developments on the fast-paced field of 2D materials.
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Affiliation(s)
- Gerardo G Naumis
- Departamento de Sistemas Complejos, Instituto de Física, Universidad Nacional Autónoma de México (UNAM), Apdo. Postal 20-364, CDMX, 01000, Mexico
| | - Saúl A Herrera
- Departamento de Sistemas Complejos, Instituto de Física, Universidad Nacional Autónoma de México (UNAM), Apdo. Postal 20-364, CDMX, 01000, Mexico
| | - Shiva P Poudel
- Department of Physics, University of Arkansas, Fayetteville, AR 72701, United States of America
- MonArk NSF Quantum Foundry, University of Arkansas, Fayetteville, AR 72701, United States of America
| | - Hiro Nakamura
- Department of Physics, University of Arkansas, Fayetteville, AR 72701, United States of America
- MonArk NSF Quantum Foundry, University of Arkansas, Fayetteville, AR 72701, United States of America
| | - Salvador Barraza-Lopez
- Department of Physics, University of Arkansas, Fayetteville, AR 72701, United States of America
- MonArk NSF Quantum Foundry, University of Arkansas, Fayetteville, AR 72701, United States of America
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23
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Xiang F, Gupta A, Chaves A, Krix ZE, Watanabe K, Taniguchi T, Fuhrer MS, Peeters FM, Neilson D, Milošević MV, Hamilton AR. Intra-Zero-Energy Landau Level Crossings in Bilayer Graphene at High Electric Fields. NANO LETTERS 2023; 23:9683-9689. [PMID: 37883804 DOI: 10.1021/acs.nanolett.3c01456] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/28/2023]
Abstract
The highly tunable band structure of the zero-energy Landau level (zLL) of bilayer graphene makes it an ideal platform for engineering novel quantum states. However, the zero-energy Landau level at high electric fields has remained largely unexplored. Here we present magnetotransport measurements of bilayer graphene in high transverse electric fields. We observe previously undetected Landau level crossings at filling factors ν = -2, 1, and 3 at high electric fields. These crossings provide constraints for theoretical models of the zero-energy Landau level and show that the orbital, valley, and spin character of the quantum Hall states at high electric fields is very different from low electric fields. At high E, new transitions between states at ν = -2 with different orbital and spin polarization can be controlled by the gate bias, while the transitions between ν = 0 → 1 and ν = 2 → 3 show anomalous behavior.
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Affiliation(s)
- Feixiang Xiang
- School of Physics, University of New South Wales, Sydney, New South Wales 2052, Australia
- ARC Centre of Excellence in Future Low-Energy Electronics Technologies, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Abhay Gupta
- School of Physics, University of New South Wales, Sydney, New South Wales 2052, Australia
- ARC Centre of Excellence in Future Low-Energy Electronics Technologies, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Andrey Chaves
- Universidade Federal do Ceará, Departamento de Física, Caixa Postal 6030, 60455-760 Fortaleza, Ceará Brazil
- Department of Physics, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp, Belgium
| | - Zeb E Krix
- School of Physics, University of New South Wales, Sydney, New South Wales 2052, Australia
- ARC Centre of Excellence in Future Low-Energy Electronics Technologies, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Kenji Watanabe
- National Institute for Materials Science, Namiki 1-1, Tsukuba, Ibaraki 305-0044, Japan
| | - Takashi Taniguchi
- National Institute for Materials Science, Namiki 1-1, Tsukuba, Ibaraki 305-0044, Japan
| | - Michael S Fuhrer
- School of Physics and Astronomy and ARC Centre of Excellence in Future Low-Energy Electronics Technologies (FLEET), Monash University, Clayton, Victoria 3800, Australia
| | - François M Peeters
- Universidade Federal do Ceará, Departamento de Física, Caixa Postal 6030, 60455-760 Fortaleza, Ceará Brazil
- Department of Physics, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp, Belgium
| | - David Neilson
- ARC Centre of Excellence in Future Low-Energy Electronics Technologies, University of New South Wales, Sydney, New South Wales 2052, Australia
- Department of Physics, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp, Belgium
| | - Milorad V Milošević
- Department of Physics, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp, Belgium
- NANOlab Center of Excellence, University of Antwerp, B-2020 Antwerp, Belgium
| | - Alexander R Hamilton
- School of Physics, University of New South Wales, Sydney, New South Wales 2052, Australia
- ARC Centre of Excellence in Future Low-Energy Electronics Technologies, University of New South Wales, Sydney, New South Wales 2052, Australia
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24
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Lee KW, Lee CE. Gapless edge states localized to odd/even layers of AA'-stacked honeycomb multilayers with staggered AB-sublattice potentials. Sci Rep 2023; 13:16915. [PMID: 37805558 PMCID: PMC10560242 DOI: 10.1038/s41598-023-44084-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2023] [Accepted: 10/03/2023] [Indexed: 10/09/2023] Open
Abstract
In honeycomb multilayers with staggered AB-sublattice potentials, we predict gapless edge states localized to either of the odd and the even layers for the AA[Formula: see text] stacking order in which the sublattice-pseudospin polarizations of adjacent layers are antiparallel. Gaps in the projected layer-pseudospin spectrum suppress interlayer hopping between odd and even layers. The layer-valley Chern number corresponding to the edge states was obtained by decomposing the occupied state into two layer-pseudospin sectors by using a projected layer-pseudospin operator. For the AB[Formula: see text] stacking, the sublattice-pseudospin polarizations of adjacent layers are antiparallel, but the layer-pseudospin spectrum gap closes at the interface of the topologically different states, leading to gapped edge states. For the AA and AB stackings where the sublattice-pseudospin polarizations of the adjacent layers are parallel, the gapless edge states corresponding to quantum valley Hall states are evenly distributed across the layers.
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Affiliation(s)
- Kyu Won Lee
- Department of Physics, Korea University, Seoul, 02841, Republic of Korea
| | - Cheol Eui Lee
- Department of Physics, Korea University, Seoul, 02841, Republic of Korea.
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25
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Dong Z, Lee PA, Levitov LS. Signatures of Cooper pair dynamics and quantum-critical superconductivity in tunable carrier bands. Proc Natl Acad Sci U S A 2023; 120:e2305943120. [PMID: 37738298 PMCID: PMC10523641 DOI: 10.1073/pnas.2305943120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2023] [Accepted: 06/21/2023] [Indexed: 09/24/2023] Open
Abstract
Different superconducting pairing mechanisms are markedly distinct in the underlying Cooper pair kinematics. Quantum-critical soft modes drive pairing interactions in which the pair scattering processes are highly collinear and can be classified into two categories: forward scattering and backscattering. Conversely, in conventional phonon mechanisms, Cooper pair scattering is of a generic noncollinear character. In this study, we present a method to discern the kinematic type by observing the evolution of superconductivity while adjusting the Fermi surface geometry. To demonstrate our approach, we utilize the recently reported phase diagrams of untwisted graphene multilayers. Our analysis connects the emergence of superconductivity at "ghost crossings" of Fermi surfaces in distinct valleys to the pair kinematics of a backscattering type. Together with the observed nonmonotonic behavior of superconductivity near its onset (sharp rise followed by a drop), it lends strong support to a particular quantum-critical superconductivity scenario in which pairing is driven by intervalley coherence fluctuations. These findings offer direct insights into the genesis of pairing in these systems, providing compelling evidence for the electron-electron interactions driving superconductivity. More broadly, our work highlights the potential of tuning bands via ghost crossings as a promising means of boosting superconductivity.
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Affiliation(s)
- Zhiyu Dong
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA02139
| | - Patrick A. Lee
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA02139
| | - Leonid S. Levitov
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA02139
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26
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Li S, Chen MLN, Lan Z, Li P. Coexistence of large-area topological pseudospin and valley states in a tri-band heterostructure system. OPTICS LETTERS 2023; 48:4693-4696. [PMID: 37656588 DOI: 10.1364/ol.501977] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2023] [Accepted: 08/14/2023] [Indexed: 09/03/2023]
Abstract
The rapid development of topological photonics has significantly revolutionized our comprehension of electromagnetic wave manipulation in recent decades. Recent research exploiting large-area topological states inserts an additional gapless PC structure between topologically trivial and nontrivial PCs, effectively introducing the mode width degree of freedom. Nevertheless, these heterostructures mainly support only single-type waveguide states operating within a single frequency band. To address these limitations, we propose a novel, to the best of our knowledge, tri-band three-layer heterostructure system, supporting both large-area pseudospin- and valley-locked states. The system showcases tunable mode widths with different operational bandwidths. Moreover, the heterostructures exhibit inherent topological characteristics and reflection-free interfacing, which are verified in the well-designed Z-shaped channels. The proposed heterostructure system can be used to design multi-band multi-functional high-flexibility topological devices, providing great advantages for enlarging the on-chip integrated communication systems.
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27
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Korkusinski M, Saleem Y, Dusko A, Miravet D, Hawrylak P. Spontaneous Spin and Valley Symmetry-Broken States of Interacting Massive Dirac Fermions in a Bilayer Graphene Quantum Dot. NANO LETTERS 2023; 23:7546-7551. [PMID: 37561956 DOI: 10.1021/acs.nanolett.3c02073] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/12/2023]
Abstract
We predict the existence of spontaneous spin and valley symmetry-broken states of interacting massive Dirac Fermions in a gated bilayer graphene quantum dot based on the exact diagonalization of the many-body Hamiltonian. The dot is defined by a vertical electric field and lateral gates, and its single-particle (SP) energies, wave functions, and Coulomb matrix elements are computed by using the atomistic tight-binding model. The effect of the Coulomb interaction is measured by the ratio of Coulomb elements to the SP level spacing. As we increase the interaction strength, we find the electrons in a series of spin and valley symmetry-broken phases with increasing valley and spin polarizations. The phase transitions result from the competition of the SP, exchange, and correlation energy scales. A phase diagram for N = 1-6 electrons is mapped out as a function of the Coulomb interaction strength.
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Affiliation(s)
- Marek Korkusinski
- Physics Department, University of Ottawa, Ottawa K1N6N5, Canada
- Security and Disruptive Technologies, National Research Council, Ottawa K1A0R6, Canada
| | - Yasser Saleem
- Physics Department, University of Ottawa, Ottawa K1N6N5, Canada
| | - Amintor Dusko
- Physics Department, University of Ottawa, Ottawa K1N6N5, Canada
| | - Daniel Miravet
- Physics Department, University of Ottawa, Ottawa K1N6N5, Canada
| | - Pawel Hawrylak
- Physics Department, University of Ottawa, Ottawa K1N6N5, Canada
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28
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Chavda CP, Srivastava A, Vaughan E, Wang J, Gartia MR, Veronis G. Effect of gamma irradiation on the physical properties of MoS 2 monolayer. Phys Chem Chem Phys 2023; 25:22359-22369. [PMID: 37580985 DOI: 10.1039/d3cp02925e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/16/2023]
Abstract
Two-dimensional transition metal dichalcogenides (2D-TMDs) have been proposed as novel optoelectronic materials for space applications due to their relatively light weight. MoS2 has been shown to have excellent semiconducting and photonic properties. Although the strong interaction of ionizing gamma radiation with bulk materials has been demonstrated, understanding its effect on atomically thin materials has scarcely been investigated. Here, we report the effect of gamma irradiation on the structural and electronic properties of a monolayer of MoS2. We perform Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) studies of MoS2, before and after gamma ray irradiation with varying doses and density functional theory (DFT) calculations. The Raman spectra and XPS results demonstrate that point defects dominate after the gamma irradiation of MoS2. DFT calculations elucidate the electronic properties of MoS2 before and after irradiation. Our work makes several contributions to the field of 2D materials research. First, our study of the electronic density of states and the electronic properties of a MoS2 monolayer irradiated by gamma rays sheds light on the properties of a MoS2 monolayer under gamma irradiation. Second, our study confirms that point defects are formed as a result of gamma irradiation. And third, our DFT calculations qualitatively suggest that the conductivity of the MoS2 monolayer may increase after gamma irradiation due to the creation of additional defect states.
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Affiliation(s)
- Chintan P Chavda
- Division of Electrical and Computer Engineering, Louisiana State University, Baton Rouge, LA, USA.
| | - Ashok Srivastava
- Division of Electrical and Computer Engineering, Louisiana State University, Baton Rouge, LA, USA.
| | - Erin Vaughan
- United States Airforce Research Laboratory, Albuquerque, NM, USA.
| | - Jianwei Wang
- Department of Geology and Geophysics, Louisiana State University, Baton Rouge, LA, USA.
| | - Manas Ranjan Gartia
- Department of Mechanical and Industrial Engineering, Louisiana State University, Baton Rouge, LA, USA.
| | - Georgios Veronis
- Division of Electrical and Computer Engineering, Louisiana State University, Baton Rouge, LA, USA.
- Center for Computation and Technology, Louisiana State University, Baton Rouge, LA, USA.
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29
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Ali H, Serra L. Electrostatic Tuning of Bilayer Graphene Edge Modes. NANOMATERIALS (BASEL, SWITZERLAND) 2023; 13:2102. [PMID: 37513113 PMCID: PMC10383601 DOI: 10.3390/nano13142102] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2023] [Revised: 07/04/2023] [Accepted: 07/14/2023] [Indexed: 07/30/2023]
Abstract
We study the effect of a local potential shift induced by a side electrode on the edge modes at the boundary between gapped and ungapped bilayer graphene. A potential shift close to the gapped-ungapped boundary causes the emergence of unprotected edge modes, propagating in both directions along the boundary. These counterpropagating edge modes allow edge backscattering, as opposed to the case of valley-momentum-locked edge modes. We then calculate the conductance of a bilayer graphene wire in presence of finger-gate electrodes, finding strong asymmetries with energy inversion and deviations from conductance quantization that can be understood with the gate-induced unprotected edge modes.
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Affiliation(s)
- Hira Ali
- Institute for Cross-Disciplinary Physics and Complex Systems IFISC (CSIC-UIB), E-07122 Palma, Spain
| | - Llorenç Serra
- Institute for Cross-Disciplinary Physics and Complex Systems IFISC (CSIC-UIB), E-07122 Palma, Spain
- Physics Department, University of the Balearic Islands, E-07122 Palma, Spain
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30
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Ingla-Aynés J, Manesco ALR, Ghiasi TS, Volosheniuk S, Watanabe K, Taniguchi T, van der Zant HSJ. Specular Electron Focusing between Gate-Defined Quantum Point Contacts in Bilayer Graphene. NANO LETTERS 2023; 23:5453-5459. [PMID: 37289250 PMCID: PMC10311585 DOI: 10.1021/acs.nanolett.3c00499] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2023] [Revised: 06/02/2023] [Indexed: 06/09/2023]
Abstract
We report multiterminal measurements in a ballistic bilayer graphene (BLG) channel, where multiple spin- and valley-degenerate quantum point contacts (QPCs) are defined by electrostatic gating. By patterning QPCs of different shapes along different crystallographic directions, we study the effect of size quantization and trigonal warping on transverse electron focusing (TEF). Our TEF spectra show eight clear peaks with comparable amplitudes and weak signatures of quantum interference at the lowest temperature, indicating that reflections at the gate-defined edges are specular, and transport is phase coherent. The temperature dependence of the focusing signal shows that, despite the small gate-induced bandgaps in our sample (≲45 meV), several peaks are visible up to 100 K. The achievement of specular reflection, which is expected to preserve the pseudospin information of the electron jets, is promising for the realization of ballistic interconnects for new valleytronic devices.
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Affiliation(s)
- Josep Ingla-Aynés
- Kavli
Institute of Nanoscience, Delft University
of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands
| | - Antonio L. R. Manesco
- Kavli
Institute of Nanoscience, Delft University
of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands
| | - Talieh S. Ghiasi
- Kavli
Institute of Nanoscience, Delft University
of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands
| | - Serhii Volosheniuk
- Kavli
Institute of Nanoscience, Delft University
of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands
| | - 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
| | - Herre S. J. van der Zant
- Kavli
Institute of Nanoscience, Delft University
of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands
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31
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Banszerus L, Möller S, Hecker K, Icking E, Watanabe K, Taniguchi T, Hassler F, Volk C, Stampfer C. Particle-hole symmetry protects spin-valley blockade in graphene quantum dots. Nature 2023:10.1038/s41586-023-05953-5. [PMID: 37138084 DOI: 10.1038/s41586-023-05953-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Accepted: 03/14/2023] [Indexed: 05/05/2023]
Abstract
Particle-hole symmetry plays an important role in the characterization of topological phases in solid-state systems1. It is found, for example, in free-fermion systems at half filling and it is closely related to the notion of antiparticles in relativistic field theories2. In the low-energy limit, graphene is a prime example of a gapless particle-hole symmetric system described by an effective Dirac equation3,4 in which topological phases can be understood by studying ways to open a gap by preserving (or breaking) symmetries5,6. An important example is the intrinsic Kane-Mele spin-orbit gap of graphene, which leads to a lifting of the spin-valley degeneracy and renders graphene a topological insulator in a quantum spin Hall phase7 while preserving particle-hole symmetry. Here we show that bilayer graphene allows the realization of electron-hole double quantum dots that exhibit near-perfect particle-hole symmetry, in which transport occurs via the creation and annihilation of single electron-hole pairs with opposite quantum numbers. Moreover, we show that particle-hole symmetric spin and valley textures lead to a protected single-particle spin-valley blockade. The latter will allow robust spin-to-charge and valley-to-charge conversion, which are essential for the operation of spin and valley qubits.
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Affiliation(s)
- L Banszerus
- JARA-FIT and 2nd Institute of Physics A, RWTH Aachen University, Aachen, Germany
- Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, Jülich, Germany
| | - S Möller
- JARA-FIT and 2nd Institute of Physics A, RWTH Aachen University, Aachen, Germany
- Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, Jülich, Germany
| | - K Hecker
- JARA-FIT and 2nd Institute of Physics A, RWTH Aachen University, Aachen, Germany
- Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, Jülich, Germany
| | - E Icking
- JARA-FIT and 2nd Institute of Physics A, RWTH Aachen University, Aachen, Germany
- Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, Jülich, Germany
| | - K Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, Tsukuba, Japan
| | - T Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Japan
| | - F Hassler
- JARA-Institute for Quantum Information, RWTH Aachen University, Aachen, Germany
| | - C Volk
- JARA-FIT and 2nd Institute of Physics A, RWTH Aachen University, Aachen, Germany
- Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, Jülich, Germany
| | - C Stampfer
- JARA-FIT and 2nd Institute of Physics A, RWTH Aachen University, Aachen, Germany.
- Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, Jülich, Germany.
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32
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Saleem Y, Sadecka K, Korkusinski M, Miravet D, Dusko A, Hawrylak P. Theory of Excitons in Gated Bilayer Graphene Quantum Dots. NANO LETTERS 2023; 23:2998-3004. [PMID: 36962005 DOI: 10.1021/acs.nanolett.3c00406] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
We present a theory of excitons in gated bilayer graphene (BLG) quantum dots (QDs). Electrical gating of BLG opens an energy gap, turning this material into an electrically tunable semiconductor. Unlike in laterally gated semiconductor QDs, where electrons are attracted and holes repelled, we show here that lateral structuring of metallic gates results in a gated lateral QD confining both electrons and holes. Using an accurate atomistic approach and exact diagonalization tools, we describe strongly interacting electrons and holes forming an electrically tunable exciton. We find these excitons to be different from those found in semiconductor QDs and nanocrystals, with exciton energy tunable by voltage from the terahertz to far infrared (FIR) range. The conservation of spin, valley, and orbital angular momentum results in an exciton fine structure with a band of dark low-energy states, making this system a promising candidate for storage, detection and emission of photons in the terahertz range.
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Affiliation(s)
- Yasser Saleem
- Department of Physics, University of Ottawa, Ottawa K1N6N5, Canada
| | - Katarzyna Sadecka
- Department of Physics, University of Ottawa, Ottawa K1N6N5, Canada
- Institute of Theoretical Physics, Wrocław University of Science and Technology, Wybrzeże Wyspiańskiego 27, 50-370 Wrocław, Poland
| | - Marek Korkusinski
- Department of Physics, University of Ottawa, Ottawa K1N6N5, Canada
- Security and Disruptive Technologies, National Research Council, Ottawa K1A0R6, Canada
| | - Daniel Miravet
- Department of Physics, University of Ottawa, Ottawa K1N6N5, Canada
| | - Amintor Dusko
- Department of Physics, University of Ottawa, Ottawa K1N6N5, Canada
| | - Pawel Hawrylak
- Department of Physics, University of Ottawa, Ottawa K1N6N5, Canada
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33
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Dey A, Chowdhury SA, Peña T, Singh S, Wu SM, Askari H. An Atomistic Insight into Moiré Reconstruction in Twisted Bilayer Graphene beyond the Magic Angle. ACS APPLIED ENGINEERING MATERIALS 2023; 1:970-982. [PMID: 37008886 PMCID: PMC10043875 DOI: 10.1021/acsaenm.2c00259] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2022] [Accepted: 03/01/2023] [Indexed: 03/18/2023]
Abstract
Twisted bilayer graphene exhibits electronic properties strongly correlated with the size and arrangement of moiré patterns. While rigid rotation of the two graphene layers results in a moiré interference pattern, local rearrangements of atoms due to interlayer van der Waals interactions result in atomic reconstruction within the moiré cells. Manipulating these patterns by controlling the twist angle and externally applied strain provides a promising route to tuning their properties. Atomic reconstruction has been extensively studied for angles close to or smaller than the magic angle (θ m = 1.1°). However, this effect has not been explored for applied strain and is believed to be negligible for high twist angles. Using interpretive and fundamental physical measurements, we use theoretical and numerical analyses to resolve atomic reconstruction in angles above θ m . In addition, we propose a method to identify local regions within moiré cells and track their evolution with strain for a range of representative high twist angles. Our results show that atomic reconstruction is actively present beyond the magic angle, and its contribution to the moiré cell evolution is significant. Our theoretical method to correlate local and global phonon behavior further validates the role of reconstruction at higher angles. Our findings provide a better understanding of moiré reconstruction in large twist angles and the evolution of moiré cells under the application of strain, which might be potentially crucial for twistronics-based applications.
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Affiliation(s)
- Aditya Dey
- Department of Mechanical Engineering, University of Rochester, Rochester, New York 14627, United States
| | - Shoieb Ahmed Chowdhury
- Department of Mechanical Engineering, University of Rochester, Rochester, New York 14627, United States
| | - Tara Peña
- Department of Electrical and Computer Engineering, University of Rochester, Rochester, New York 14627, United States
| | - Sobhit Singh
- Department of Mechanical Engineering, University of Rochester, Rochester, New York 14627, United States
| | - Stephen M. Wu
- Department of Electrical and Computer Engineering, University of Rochester, Rochester, New York 14627, United States
| | - Hesam Askari
- Department of Mechanical Engineering, University of Rochester, Rochester, New York 14627, United States
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34
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Wei X, Jin L, Zhang X, Liu Y, Dai X, Liu G. A two-dimensional tunable double Weyl fermion in BL-α borophene. Phys Chem Chem Phys 2023; 25:7338-7343. [PMID: 36825463 DOI: 10.1039/d2cp05559g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/15/2023]
Abstract
Two-dimensional (2D) materials with nontrivial band crossings, namely linear or double Weyl points, have been attracting tremendous attention. However, it remains a challenge to find existing 2D materials that host such nontrivial states. Here, based on first-principles calculations and symmetry analysis, we discover that the recently synthesized BL-α borophene is a metal with a tunable double Weyl point. Remarkably, both bands forming the double Weyl point have upward band bending. In addition, it shows an anisotropic band dispersion when away from the double Weyl point. To characterize its anisotropy, we define a quantity G, which could be changed from 1 to infinity when going from the energy of the double Weyl point to the Fermi level. Furthermore, the outer band of the double Weyl point is sensitive to biaxial strain, and could be changed from upward bending to downward bending. During this process, it has a critical case, in which the outer-band becomes flat. The changes in outer-band induce a variation in the density of states around the double Weyl point, thus giving rise to changes in its macroscopic physical properties. Applying a uniaxial strain enables the double Weyl point to transform into a pair of Weyl points by breaking the threefold rotation of BL-α borophene. When breaking the inversion symmetry and in-plane twofold rotation symmetry by a vertical symmetry, the double Weyl point still persisted; meanwhile, an additional pair of linear Weyl points appears on the high-symmetry path, giving rise to a Weyl complex case. Overall, our work thus provides an existing 2D material, BL-α borophene, to study the nontrivial band crossings in 2D.
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Affiliation(s)
- Xiaoyu Wei
- State Key Laboratory of Reliability and Intelligence of Electrical Equipment, Hebei University of Technology, Tianjin 300130, China. .,School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130, China.
| | - Lei Jin
- State Key Laboratory of Reliability and Intelligence of Electrical Equipment, Hebei University of Technology, Tianjin 300130, China. .,School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130, China.
| | - Xiaoming Zhang
- State Key Laboratory of Reliability and Intelligence of Electrical Equipment, Hebei University of Technology, Tianjin 300130, China. .,School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130, China.
| | - Ying Liu
- School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130, China.
| | - Xuefang Dai
- School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130, China.
| | - Guodong Liu
- State Key Laboratory of Reliability and Intelligence of Electrical Equipment, Hebei University of Technology, Tianjin 300130, China. .,School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130, China.
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35
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Smeyers R, Milošević MV, Covaci L. Strong gate-tunability of flat bands in bilayer graphene due to moiré encapsulation between hBN monolayers. NANOSCALE 2023; 15:4561-4569. [PMID: 36762535 DOI: 10.1039/d2nr07171a] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
When using hexagonal boron-nitride (hBN) as a substrate for graphene, the resulting moiré pattern creates secondary Dirac points. By encapsulating a multilayer graphene within aligned hBN sheets the controlled moiré stacking may offer even richer benefits. Using advanced tight-binding simulations on atomistically-relaxed heterostructures, here we show that the gap at the secondary Dirac point can be opened in selected moiré-stacking configurations, and is independent of any additional vertical gating of the heterostructure. On the other hand, gating can broadly tune the gap at the principal Dirac point, and may thereby strongly compress the first moiré mini-band in width against the moiré-induced gap at the secondary Dirac point. We reveal that in hBN-encapsulated bilayer graphene this novel mechanism can lead to isolated bands flatter than 10 meV under moderate gating, hence presenting a convenient pathway towards electronically-controlled strongly-correlated states on demand.
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Affiliation(s)
- Robin Smeyers
- Department of Physics and NANOlab Center of Excellence, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium.
| | - Milorad V Milošević
- Department of Physics and NANOlab Center of Excellence, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium.
- Instituto de Física, Universidade Federal de Mato Grosso, Cuiabá, Mato Grosso 78060-900, Brazil
| | - Lucian Covaci
- Department of Physics and NANOlab Center of Excellence, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium.
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36
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Romeo A, Supèr H. Optimal twist angle for a graphene-like bilayer. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2023; 35:165302. [PMID: 36745921 DOI: 10.1088/1361-648x/acb985] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2022] [Accepted: 02/06/2023] [Indexed: 06/18/2023]
Abstract
The first optimal-or 'magic'-angle leading to the nullity of the Dirac/Fermi velocity for twisted bilayer graphene is re-evaluated in the Bistritzer-MacDonald set-up (Bistritzer and MacDonald 2011Proc. Natl Acad. Sci.10812233-7). From the details of that calculation we study the resulting alterations when the properties of the two layers are not exactly the same. A moiré combination of lattices without relative rotation but with different spacing lengths may also lead to a vanishing Dirac velocity. Hopping amplitudes can vary as well, and curvature is one of the possible causes for their change. In the case of small curvature values and situations dominated by hopping energy scales, the optimal angle becomes wider than in the 'flat' case.
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Affiliation(s)
| | - Hans Supèr
- University of Barcelona, Barcelona, Spain
- Catalan Institution for Research and Advanced Studies (ICREA), Barcelona, Spain
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37
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Demin VA, Chernozatonskii LA. Diamane-like Films Based on Twisted G/BN Bilayers: DFT Modelling of Atomic Structures and Electronic Properties. NANOMATERIALS (BASEL, SWITZERLAND) 2023; 13:841. [PMID: 36903720 PMCID: PMC10004773 DOI: 10.3390/nano13050841] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/26/2023] [Revised: 02/21/2023] [Accepted: 02/22/2023] [Indexed: 06/18/2023]
Abstract
Diamanes are unique 2D carbon materials that can be obtained by the adsorption of light atoms or molecular groups onto the surfaces of bilayer graphene. Modification of the parent bilayers, such as through twisting of the layers and the substitution of one of the layers with BN, leads to drastic changes in the structure and properties of diamane-like materials. Here, we present the results of the DFT modelling of new stable diamane-like films based on twisted Moiré G/BN bilayers. The set of angles at which this structure becomes commensurate was found. We used two commensurate structures with twisted angles of θ = 10.9° and θ = 25.3° with the smallest period as the base for the formation of the diamane-like material. Previous theoretical investigations did not take into account the incommensurability of graphene and boron nitride monolayers when considering diamane-like films. The double-sided hydrogenation or fluorination of Moiré G/BN bilayers and the following interlayer covalent bonding led to the opening of a gap up to 3.1 eV, which was lower than the corresponding values of h-BN and c-BN. The considered G/BN diamane-like films offer great potential in the future for a variety of engineering applications.
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38
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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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39
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Hu LH, Zhang RX. Topological superconducting vortex from trivial electronic bands. Nat Commun 2023; 14:640. [PMID: 36746955 PMCID: PMC9902606 DOI: 10.1038/s41467-023-36347-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2022] [Accepted: 01/24/2023] [Indexed: 02/08/2023] Open
Abstract
Superconducting vortices are promising traps to confine non-Abelian Majorana quasi-particles. It has been widely believed that bulk-state topology, of either normal-state or superconducting ground-state wavefunctions, is crucial for enabling Majorana zero modes in solid-state systems. This common belief has shaped two major search directions for Majorana modes, in either intrinsic topological superconductors or trivially superconducting topological materials. Here we show that Majorana-carrying superconducting vortex is not exclusive to bulk-state topology, but can arise from topologically trivial quantum materials as well. We predict that the trivial bands in superconducting HgTe-class materials are responsible for inducing anomalous vortex topological physics that goes beyond any existing theoretical paradigms. A feasible scheme of strain-controlled Majorana engineering and experimental signatures for vortex Majorana modes are also discussed. Our work provides new guidelines for vortex-based Majorana search in general superconductors.
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Affiliation(s)
- Lun-Hui Hu
- grid.411461.70000 0001 2315 1184Department of Physics and Astronomy, The University of Tennessee, Knoxville, TN 37996 USA ,grid.411461.70000 0001 2315 1184Institute for Advanced Materials and Manufacturing, The University of Tennessee, Knoxville, TN 37920 USA
| | - Rui-Xing Zhang
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, TN, 37996, USA. .,Institute for Advanced Materials and Manufacturing, The University of Tennessee, Knoxville, TN, 37920, USA. .,Department of Materials Science and Engineering, The University of Tennessee, Knoxville, TN, 37996, USA.
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40
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Sarkar N, Bandaru PR, Dynes RC. Probing interlayer van der Waals strengths of two-dimensional surfaces and defects, through STM tip-induced elastic deformations. NANOTECHNOLOGY 2023; 34:15LT01. [PMID: 36652700 DOI: 10.1088/1361-6528/acb442] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2022] [Accepted: 01/18/2023] [Indexed: 06/17/2023]
Abstract
A methodology to test the interlayer bonding strength of two-dimensional (2D) surfaces and associated one (1D)- and two (2D)- dimensional surface defects using scanning tunneling microscope tip-induced deformation, is demonstrated. Surface elastic deformation characteristics of soft 2D monatomic sheets of graphene and graphite in contrast to NbSe2indicates related association with the underlying local bonding configurations. Surface deformation of 2D graphitic moiré patterns reveal the inter-layer van der Waals strength varying across its domains. These results help in the understanding of the comparable interlayer bonding strength of 1D grain boundary as well as the grains. Anomalous phenomena related to probing 2D materials at small gap distances as a function of strain is discussed.
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Affiliation(s)
- N Sarkar
- Department of Mechanical Engineering, University of California San Diego, La Jolla, CA 92093-0411, United States of America
| | - P R Bandaru
- Department of Mechanical Engineering, University of California San Diego, La Jolla, CA 92093-0411, United States of America
- Program in Materials Science, University of California San Diego, La Jolla, CA 92093-0411, United States of America
| | - R C Dynes
- Department of Physics, University of California San Diego, La Jolla, CA 92093-0411, United States of America
- Program in Materials Science, University of California San Diego, La Jolla, CA 92093-0411, United States of America
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41
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Chen H, Zhao ZF, Li WJ, Cheng ZD, Suo JJ, Li BL, Guo ML, Fan BY, Zhou Q, Wang Y, Song HZ, Niu XB, Li XY, Arutyunov KY, Guo GC, Deng GW. Gate-tunable bolometer based on strongly coupled graphene mechanical resonators. OPTICS LETTERS 2023; 48:81-84. [PMID: 36563374 DOI: 10.1364/ol.476010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/26/2022] [Accepted: 11/21/2022] [Indexed: 06/17/2023]
Abstract
Bolometers based on graphene have demonstrated outstanding performance with high sensitivity and short response time. In situ adjustment of bolometers is very important in various applications, but it is still difficult to implement in many systems. Here we propose a gate-tunable bolometer based on two strongly coupled graphene nanomechanical resonators. Both resonators are exposed to the same light field, and we can measure the properties of one bolometer by directly tracking the resonance frequency shifts, and indirectly measure the other bolometer through mechanical coupling. We find that the sensitivity and the response bandwidth of both bolometers can be independently adjusted by tuning the corresponding gate voltages. Moreover, the properties of the indirectly measured bolometer show a dependence on the coupling between the two resonators, with other parameters being fixed. Our method has the potential to optimize the design of large-scale bolometer arrays, and open new horizons in infrared/terahertz astronomy and communication systems.
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42
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Enhanced superconductivity in spin-orbit proximitized bilayer graphene. Nature 2023; 613:268-273. [PMID: 36631645 DOI: 10.1038/s41586-022-05446-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2022] [Accepted: 10/14/2022] [Indexed: 01/13/2023]
Abstract
In the presence of a large perpendicular electric field, Bernal-stacked bilayer graphene (BLG) features several broken-symmetry metallic phases1-3 as well as magnetic-field-induced superconductivity1. The superconducting state is quite fragile, however, appearing only in a narrow window of density and with a maximum critical temperature Tc ≈ 30 mK. Here we show that placing monolayer tungsten diselenide (WSe2) on BLG promotes Cooper pairing to an extraordinary degree: superconductivity appears at zero magnetic field, exhibits an order of magnitude enhancement in Tc and occurs over a density range that is wider by a factor of eight. By mapping quantum oscillations in BLG-WSe2 as a function of electric field and doping, we establish that superconductivity emerges throughout a region for which the normal state is polarized, with two out of four spin-valley flavours predominantly populated. In-plane magnetic field measurements further reveal that superconductivity in BLG-WSe2 can exhibit striking dependence of the critical field on doping, with the Chandrasekhar-Clogston (Pauli) limit roughly obeyed on one end of the superconducting dome, yet sharply violated on the other. Moreover, the superconductivity arises only for perpendicular electric fields that push BLG hole wavefunctions towards WSe2, indicating that proximity-induced (Ising) spin-orbit coupling plays a key role in stabilizing the pairing. Our results pave the way for engineering robust, highly tunable and ultra-clean graphene-based superconductors.
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43
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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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44
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Liu HY, Wu JY. Feature-Rich Electronic Properties of Sliding Bilayer Germanene. ACS OMEGA 2022; 7:42304-42312. [PMID: 36440158 PMCID: PMC9686190 DOI: 10.1021/acsomega.2c05219] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/14/2022] [Accepted: 10/31/2022] [Indexed: 06/16/2023]
Abstract
This study employs first-principles calculations to elucidate the properties of sliding bilayer germanene (BLGe). The buckled structure of germanene can afford a greater number of metastable stacking configurations than planar graphene and enrich the electronic properties. Herein, a detailed analysis of the structural variety, shift-dependent energy bands, and spatial charge densities of BLGe is presented. The projected density of states (PDOS) reveals diverse structures such as plateaus, dips, symmetric/asymmetric peaks, and shoulders. The low-lying ones of the prominent structures could correspond to single or multiorbital hybridization, depending on the stacking configuration.
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Affiliation(s)
- Hsin-Yi Liu
- Department
of Physics/QTC/Hi-GEM, National Cheng Kung
University, Tainan 70148, Taiwan
| | - Jhao-Ying Wu
- Center
of General Studies, National Kaohsiung University
of Science and Technology, Kaohsiung 811213, Taiwan
- Department
of Energy and Refrigerating Air-Conditioning Engineering, National Kaohsiung University of Science and Technology, Kaohsiung 811213, Taiwan
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45
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Miranda LP, da Costa DR, Peeters FM, Costa Filho RN. Vacancy clustering effect on the electronic and transport properties of bilayer graphene nanoribbons. NANOTECHNOLOGY 2022; 34:055706. [PMID: 36322965 DOI: 10.1088/1361-6528/ac9f50] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2022] [Accepted: 11/01/2022] [Indexed: 06/16/2023]
Abstract
Experimental realizations of two-dimensional materials are hardly free of structural defects such as e.g. vacancies, which, in turn, modify drastically its pristine physical defect-free properties. In this work, we explore effects due to point defect clustering on the electronic and transport properties of bilayer graphene nanoribbons, for AA and AB stacking and zigzag and armchair boundaries, by means of the tight-binding approach and scattering matrix formalism. Evident vacancy concentration signatures exhibiting a maximum amplitude and an universality regardless of the system size, stacking and boundary types, in the density of states around the zero-energy level are observed. Our results are explained via the coalescence analysis of the strong sizeable vacancy clustering effect in the system and the breaking of the inversion symmetry at high vacancy densities, demonstrating a similar density of states for two equivalent degrees of concentration disorder, below and above the maximum value.
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Affiliation(s)
- L P Miranda
- Departamento de Física, Universidade Federal do Ceará, Campus do Pici, Fortaleza, Ceará, Brazil
| | - D R da Costa
- Departamento de Física, Universidade Federal do Ceará, Campus do Pici, Fortaleza, Ceará, Brazil
- Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education & Hunan Provincial Key Laboratory of Low-Dimensional Structural Physics and Devices, School of Physics and Electronics, Hunan University, Changsha 410082, People's Republic of China
| | - F M Peeters
- Department of Physics, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp, Belgium
| | - R N Costa Filho
- Departamento de Física, Universidade Federal do Ceará, Campus do Pici, Fortaleza, Ceará, Brazil
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46
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Jakubský V, Zelaya K. Landau levels and snake states of pseudo-spin-1 Dirac-like electrons in gapped Lieb lattices. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 51:025302. [PMID: 36317292 DOI: 10.1088/1361-648x/ac9e84] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2022] [Accepted: 10/28/2022] [Indexed: 06/16/2023]
Abstract
This work reports the three-band structure associated with a Lieb lattice with arbitrary nearest and next-nearest neighbors hopping interactions. For specific configurations, the system admits a flat band located between two dispersion bands, where three inequivalent Dirac valleys are identified. Furthermore, quasi-particles are effectively described by a spin-1 Dirac-type equation. Under external homogeneous magnetic fields, the Landau levels are exactly determined as the third-order polynomial equation for the energy can be solved using Cardano's formula. It is also shown that an external anti-symmetric field promotes the existence of current-carrying states, so-called snake states, confined at the interface where the external field changes its sign.
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Affiliation(s)
- V Jakubský
- Nuclear Physics Institute, Czech Academy of Sciences, Řež 250 68, Czech Republic
| | - K Zelaya
- Nuclear Physics Institute, Czech Academy of Sciences, Řež 250 68, Czech Republic
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47
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Georgoulea NC, Power SR, Caffrey NM. Strain-induced stacking transition in bilayer graphene. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 34:475302. [PMID: 36174544 DOI: 10.1088/1361-648x/ac965d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2022] [Accepted: 09/29/2022] [Indexed: 06/16/2023]
Abstract
Strain, both naturally occurring and deliberately engineered, can have a considerable effect on the structural and electronic properties of 2D and layered materials. Uniaxial or biaxial heterostrain modifies the stacking arrangement of bilayer graphene (BLG) which subsequently influences the electronic structure of the bilayer. Here, we use density functional theory (DFT) calculations to investigate the interplay between an external applied heterostrain and the resulting stacking in BLG. We determine how a strain applied to one layer is transferred to a second, 'free' layer and at what critical strain the ground-state AB-stacking is disrupted. To overcome limitations introduced by periodic boundary conditions, we consider an approximate system consisting of an infinite graphene sheet and an armchair graphene nanoribbon. We find that above a critical strain of∼1%, it is energetically favourable for the free layer to be unstrained, indicating a transition between uniform AB-stacking and non-uniform mixed stacking. This is in agreement with a simple model estimate based on the individual energy contributions of strain and stacking effects. Our findings suggest that small levels of strain provide a platform to reversibly engineer stacking order and Moiré features in bilayers, providing a viable alternative to twistronics to engineer topological and exotic physical phenomena in such systems.
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Affiliation(s)
- Nina C Georgoulea
- School of Physics, AMBER & CRANN Institute, Trinity College Dublin, Dublin 2, Ireland
| | - Stephen R Power
- School of Physics, AMBER & CRANN Institute, Trinity College Dublin, Dublin 2, Ireland
- School of Physical Sciences, Dublin City University, Dublin 9, Ireland
| | - Nuala M Caffrey
- School of Physics, University College Dublin, Dublin 4, Ireland
- Centre for Quantum Engineering, Science, and Technology, University College Dublin, Dublin 4, Ireland
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Brown CD, Chang SW, Schwarz MN, Leung TH, Kozii V, Avdoshkin A, Moore JE, Stamper-Kurn D. Direct geometric probe of singularities in band structure. Science 2022; 377:1319-1322. [DOI: 10.1126/science.abm6442] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
A quantum system’s energy landscape may have points where multiple energy surfaces are degenerate and that exhibit singular geometry of the wave function manifold, with major consequences for the system’s properties. Ultracold atoms in optical lattices have been used to indirectly characterize such points in the band structure. We measured the non-Abelian transformation produced by transport directly through the singularities. We accelerated atoms along a quasi-momentum trajectory that enters, turns, and then exits the singularities at linear and quadratic band-touching points of a honeycomb lattice. Measurements after transport identified the topological winding numbers of these singularities to be 1 and 2, respectively. Our work introduces a distinct method for probing singularities that enables the study of non-Dirac singularities in ultracold-atom quantum simulators.
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Affiliation(s)
- Charles D. Brown
- Department of Physics, University of California, Berkeley, Berkeley, CA 94720, USA
- Challenge Institute for Quantum Computation, University of California, Berkeley, Berkeley, CA 94720, USA
- Department of Physics, Yale University, New Haven, CT 06520, USA
| | - Shao-Wen Chang
- Department of Physics, University of California, Berkeley, Berkeley, CA 94720, USA
- Challenge Institute for Quantum Computation, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Malte N. Schwarz
- Department of Physics, University of California, Berkeley, Berkeley, CA 94720, USA
- Challenge Institute for Quantum Computation, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Tsz-Him Leung
- Department of Physics, University of California, Berkeley, Berkeley, CA 94720, USA
- Challenge Institute for Quantum Computation, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Vladyslav Kozii
- Department of Physics, University of California, Berkeley, Berkeley, CA 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
- Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213, USA
| | - Alexander Avdoshkin
- Department of Physics, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Joel E. Moore
- Department of Physics, University of California, Berkeley, Berkeley, CA 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Dan Stamper-Kurn
- Department of Physics, University of California, Berkeley, Berkeley, CA 94720, USA
- Challenge Institute for Quantum Computation, University of California, Berkeley, Berkeley, CA 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
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Li L, Xia Y, Zeng M, Fu L. Facet engineering of ultrathin two-dimensional materials. Chem Soc Rev 2022; 51:7327-7343. [PMID: 35924550 DOI: 10.1039/d2cs00067a] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Ultrathin two-dimensional (2D) materials exhibit broad application prospects in many fields due to the enhanced specific surface area to volume ratio and quantum confinement effect. Because of the atomic thickness and various orientations, ultrathin 2D materials exposing specific facets have drawn great attention for various applications in catalysis, batteries, optoelectronics, magnetism, epitaxial template for material growth, etc. Though maintaining the atomic thickness of 2D materials while controlling crystal facets is an enormous challenge, breakthroughs are being made. This review provides a comprehensive overview of the recent advances in the facet engineering of 2D materials, ranging from a basic understanding of facets and the corresponding approaches and the significance of facet engineering. We also propose current challenges and forecast future development directions including the establishment of a facet database, the fabrication of new 2D materials, the design of specific substrates, and the introduction of theoretical calculations and in situ characterization techniques. This review can guide researchers to design ultrathin 2D materials with unique and distinct facets and provide an insight into the applications of energy, magnetism, optics, biomedicine, and other fields.
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Affiliation(s)
- Linyang Li
- College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, China.
| | - Yabei Xia
- College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, China.
| | - Mengqi Zeng
- College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, China.
| | - Lei Fu
- College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, China. .,The Institute for Advanced Studies (IAS), Wuhan University, Wuhan 430072, China.
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Hesp NCH, Svendsen MK, Watanabe K, Taniguchi T, Thygesen KS, Torre I, Koppens FHL. WSe 2 as Transparent Top Gate for Infrared Near-Field Microscopy. NANO LETTERS 2022; 22:6200-6206. [PMID: 35872651 DOI: 10.1021/acs.nanolett.2c01658] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Independent control of carrier density and out-of-plane displacement field is essential for accessing novel phenomena in two-dimensional (2D) material heterostructures. While this is achieved with independent top and bottom metallic gate electrodes in transport experiments, it remains a challenge for near-field optical studies as the top electrode interferes with the optical path. Here, we characterize the requirements for a material to be used as the top-gate electrode and demonstrate experimentally that few-layer WSe2 can be used as a transparent, ambipolar top-gate electrode in infrared near-field microscopy. We carry out nanoimaging of plasmons in a bilayer graphene heterostructure tuning the plasmon wavelength using a trilayer WSe2 gate, achieving a density modulation amplitude exceeding 2 × 1012 cm-2. The observed ambipolar gate-voltage response allows us to extract the energy gap of WSe2, yielding a value of 1.05 eV. Our results provide an additional tuning knob to cryogenic near-field experiments on emerging phenomena in 2D materials and moiré heterostructures.
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Affiliation(s)
- Niels C H Hesp
- ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology, Av. Carl Friedrich Gauss 3, 08860 Castelldefels, Barcelona, Spain
| | - Mark Kamper Svendsen
- CAMD, Computational Atomic-Scale Materials Design, Department of Physics, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark
| | - 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
| | - Kristian S Thygesen
- CAMD, Computational Atomic-Scale Materials Design, Department of Physics, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark
- Center for Nanostructured Graphene (CNG), Department of Physics, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark
| | - Iacopo Torre
- ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology, Av. Carl Friedrich Gauss 3, 08860 Castelldefels, Barcelona, Spain
| | - Frank H L Koppens
- ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology, Av. Carl Friedrich Gauss 3, 08860 Castelldefels, Barcelona, Spain
- ICREA-Institució Catalana de Recerca i Estudis Avançats, 08010 Barcelona, Spain
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