1
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Saha D, Waters D, Yeh CC, Mhatre SM, Tran NTM, Hill HM, Watanabe K, Taniguchi T, Newell DB, Yankowitz M, Rigosi AF. Graphene-Based Analog of Single-Slit Electron Diffraction. PHYSICAL REVIEW. B 2023; 108:10.1103/physrevb.108.125420. [PMID: 37841515 PMCID: PMC10572097 DOI: 10.1103/physrevb.108.125420] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/17/2023]
Abstract
This work reports the experimental demonstration of single-slit diffraction exhibited by electrons propagating in encapsulated graphene with an effective de Broglie wavelength corresponding to their attributes as massless Dirac fermions. Nanometer-scale device designs were implemented to fabricate a single-slit followed by five detector paths. Predictive calculations were also utilized to readily understand the observations reported. These calculations required the modeling of wave propagation in ideal case scenarios of the reported device designs to more accurately describe the observed single-slit phenomenon. This experiment was performed at room temperature and 190 K, where data from the latter highlighted the exaggerated asymmetry between electrons and holes, recently ascribed to slightly different Fermi velocities near the K point. This observation and device concept may be used for building diffraction switches with versatile applicability.
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Affiliation(s)
- Dipanjan Saha
- Physical Measurement Laboratory, National Institute of Standards and Technology (NIST), Gaithersburg, MD 20899, United States
| | - Dacen Waters
- Intelligence Community Postdoctoral Research Fellowship Program, University of Washington, Seattle, WA 98195, United States
- Department of Physics, University of Washington, Seattle, WA 98195, United States
| | - Ching-Chen Yeh
- Physical Measurement Laboratory, National Institute of Standards and Technology (NIST), Gaithersburg, MD 20899, United States
- Department of Physics, National Taiwan University, Taipei 10617, Taiwan
| | - Swapnil M. Mhatre
- Physical Measurement Laboratory, National Institute of Standards and Technology (NIST), Gaithersburg, MD 20899, United States
| | - Ngoc Thanh Mai Tran
- Physical Measurement Laboratory, National Institute of Standards and Technology (NIST), Gaithersburg, MD 20899, United States
- Joint Quantum Institute, University of Maryland, College Park, Maryland 20742, United States
| | - Heather M. Hill
- Physical Measurement Laboratory, National Institute of Standards and Technology (NIST), Gaithersburg, MD 20899, United States
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - David B. Newell
- Physical Measurement Laboratory, National Institute of Standards and Technology (NIST), Gaithersburg, MD 20899, United States
| | - Matthew Yankowitz
- Department of Physics, University of Washington, Seattle, WA 98195, United States
- Department of Materials Science and Engineering, University of Washington, Seattle, WA 98195, United States
| | - Albert F. Rigosi
- Physical Measurement Laboratory, National Institute of Standards and Technology (NIST), Gaithersburg, MD 20899, United States
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2
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Schock RTK, Neuwald J, Möckel W, Kronseder M, Pirker L, Remškar M, Hüttel AK. Non-Destructive Low-Temperature Contacts to MoS 2 Nanoribbon and Nanotube Quantum Dots. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023; 35:e2209333. [PMID: 36624967 DOI: 10.1002/adma.202209333] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2022] [Revised: 12/15/2022] [Indexed: 06/17/2023]
Abstract
Molybdenum disulfide nanoribbons and nanotubes are quasi-1D semiconductors with strong spin-orbit interaction, a nanomaterial highly promising for quantum electronic applications. Here, it is demonstrated that a bismuth semimetal layer between the contact metal and this nanomaterial strongly improves the properties of the contacts. Two-point resistances on the order of 100 kΩ are observed at room temperature. At cryogenic temperature, Coulomb blockade is visible. The resulting stability diagrams indicate a marked absence of trap states at the contacts and the corresponding disorder, compared to previous devices that use low-work-function metals as contacts. Single-level quantum transport is observed at temperatures below 100 mK.
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Affiliation(s)
- Robin T K Schock
- Institute for Experimental and Applied Physics, University of Regensburg, 93040, Regensburg, Germany
| | - Jonathan Neuwald
- Institute for Experimental and Applied Physics, University of Regensburg, 93040, Regensburg, Germany
| | - Wolfgang Möckel
- Institute for Experimental and Applied Physics, University of Regensburg, 93040, Regensburg, Germany
| | - Matthias Kronseder
- Institute for Experimental and Applied Physics, University of Regensburg, 93040, Regensburg, Germany
| | - Luka Pirker
- Solid State Physics Department, Jožef Stefan Institute, 1000, Ljubljana, Slovenia
- J. Heyrovský Institute of Physical Chemistry, v.v.i., Czech Academy of Sciences, 182 23, Prague, Czech Republic
| | - Maja Remškar
- Solid State Physics Department, Jožef Stefan Institute, 1000, Ljubljana, Slovenia
| | - Andreas K Hüttel
- Institute for Experimental and Applied Physics, University of Regensburg, 93040, Regensburg, Germany
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3
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Joucken F, Bena C, Ge Z, Quezada-Lopez E, Pinon S, Kaladzhyan V, Taniguchi T, Watanabe K, Ferreira A, Velasco J. Direct Visualization of Native Defects in Graphite and Their Effect on the Electronic Properties of Bernal-Stacked Bilayer Graphene. NANO LETTERS 2021; 21:7100-7108. [PMID: 34415771 DOI: 10.1021/acs.nanolett.1c01442] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Graphite crystals used to prepare graphene-based heterostructures are generally assumed to be defect free. We report here scanning tunneling microscopy results that show graphite commonly used to prepare graphene devices can contain a significant amount of native defects. Extensive scanning of the surface allows us to determine the concentration of native defects to be 6.6 × 108 cm-2. We further study the effects of these native defects on the electronic properties of Bernal-stacked bilayer graphene. We observe gate-dependent intravalley scattering and successfully compare our experimental results to T-matrix-based calculations, revealing a clear carrier density dependence in the distribution of the scattering vectors. We also present a technique for evaluating the spatial distribution of short-scale scattering. Finally, we present a theoretical analysis based on the Boltzmann transport equation that predicts that the dilute native defects identified in our study are an important extrinsic source of scattering, ultimately setting the charge carrier mobility at low temperatures.
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Affiliation(s)
- Frédéric Joucken
- Department of Physics, University of California, Santa Cruz, California 95064, United States
- Department of Physics, Arizona State University, Tempe, Arizona 85287, United States
| | - Cristina Bena
- Institut de Physique Théorique, Université Paris Saclay, CEA CNRS, Orme des Merisiers, 91190 Gif-sur-Yvette Cedex, France
| | - Zhehao Ge
- Department of Physics, University of California, Santa Cruz, California 95064, United States
| | - Eberth Quezada-Lopez
- Department of Physics, University of California, Santa Cruz, California 95064, United States
| | - Sarah Pinon
- Institut de Physique Théorique, Université Paris Saclay, CEA CNRS, Orme des Merisiers, 91190 Gif-sur-Yvette Cedex, France
| | - Vardan Kaladzhyan
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Aires Ferreira
- Department of Physics and York Centre for Quantum Technologies, University of York, York YO10 5DD, United Kingdom
| | - Jairo Velasco
- Department of Physics, University of California, Santa Cruz, California 95064, United States
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4
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Banszerus L, Rothstein A, Fabian T, Möller S, Icking E, Trellenkamp S, Lentz F, Neumaier D, Watanabe K, Taniguchi T, Libisch F, Volk C, Stampfer C. Electron-Hole Crossover in Gate-Controlled Bilayer Graphene Quantum Dots. NANO LETTERS 2020; 20:7709-7715. [PMID: 32986437 PMCID: PMC7564435 DOI: 10.1021/acs.nanolett.0c03227] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Revised: 09/28/2020] [Indexed: 05/21/2023]
Abstract
Electron and hole Bloch states in bilayer graphene exhibit topological orbital magnetic moments with opposite signs, which allows for tunable valley-polarization in an out-of-plane magnetic field. This property makes electron and hole quantum dots (QDs) in bilayer graphene interesting for valley and spin-valley qubits. Here, we show measurements of the electron-hole crossover in a bilayer graphene QD, demonstrating opposite signs of the magnetic moments associated with the Berry curvature. Using three layers of top gates, we independently control the tunneling barriers while tuning the occupation from the few-hole regime to the few-electron regime, crossing the displacement-field-controlled band gap. The band gap is around 25 meV, while the charging energies of the electron and hole dots are between 3 and 5 meV. The extracted valley g-factor is around 17 and leads to opposite valley polarization for electrons and holes at moderate B-fields. Our measurements agree well with tight-binding calculations for our device.
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Affiliation(s)
- L. Banszerus
- JARA-FIT
and 2nd Institute of Physics, RWTH Aachen
University, 52074 Aachen, Germany, E.U
- Peter
Grünberg Institute (PGI-9), Forschungszentrum
Jülich, 52425 Jülich, Germany, E.U
| | - A. Rothstein
- JARA-FIT
and 2nd Institute of Physics, RWTH Aachen
University, 52074 Aachen, Germany, E.U
| | - T. Fabian
- Institute
for Theoretical Physics, TU Wien, 1040 Vienna, Austria, E.U
| | - S. Möller
- JARA-FIT
and 2nd Institute of Physics, RWTH Aachen
University, 52074 Aachen, Germany, E.U
- Peter
Grünberg Institute (PGI-9), Forschungszentrum
Jülich, 52425 Jülich, Germany, E.U
| | - E. Icking
- JARA-FIT
and 2nd Institute of Physics, RWTH Aachen
University, 52074 Aachen, Germany, E.U
- Peter
Grünberg Institute (PGI-9), Forschungszentrum
Jülich, 52425 Jülich, Germany, E.U
| | - S. Trellenkamp
- Helmholtz
Nano Facility, Forschungszentrum Jülich, 52425 Jülich, Germany
| | - F. Lentz
- Helmholtz
Nano Facility, Forschungszentrum Jülich, 52425 Jülich, Germany
| | - D. Neumaier
- AMO
GmbH, Gesellschaft für
Angewandte Mikro- und Optoelektronik, 52074 Aachen, Germany, E.U
- University
of Wuppertal, 42285 Wuppertal, Germany, E.U
| | - 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
| | - F. Libisch
- Institute
for Theoretical Physics, TU Wien, 1040 Vienna, Austria, E.U
| | - C. Volk
- JARA-FIT
and 2nd Institute of Physics, RWTH Aachen
University, 52074 Aachen, Germany, E.U
- Peter
Grünberg Institute (PGI-9), Forschungszentrum
Jülich, 52425 Jülich, Germany, E.U
| | - C. Stampfer
- JARA-FIT
and 2nd Institute of Physics, RWTH Aachen
University, 52074 Aachen, Germany, E.U
- Peter
Grünberg Institute (PGI-9), Forschungszentrum
Jülich, 52425 Jülich, Germany, E.U
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5
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Wang L, Makk P, Zihlmann S, Baumgartner A, Indolese DI, Watanabe K, Taniguchi T, Schönenberger C. Mobility Enhancement in Graphene by in situ Reduction of Random Strain Fluctuations. PHYSICAL REVIEW LETTERS 2020; 124:157701. [PMID: 32357042 DOI: 10.1103/physrevlett.124.157701] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Accepted: 03/16/2020] [Indexed: 06/11/2023]
Abstract
Microscopic corrugations are ubiquitous in graphene even when placed on atomically flat substrates. These result in random local strain fluctuations limiting the carrier mobility of high quality hBN-supported graphene devices. We present transport measurements in hBN-encapsulated devices where such strain fluctuations can be in situ reduced by increasing the average uniaxial strain. When ∼0.2% of uniaxial strain is applied to the graphene, an enhancement of the carrier mobility by ∼35% is observed while the residual doping reduces by ∼39%. We demonstrate a strong correlation between the mobility and the residual doping, from which we conclude that random local strain fluctuations are the dominant source of disorder limiting the mobility in these devices. Our findings are also supported by Raman spectroscopy measurements.
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Affiliation(s)
- Lujun Wang
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
- Swiss Nanoscience Institute, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
| | - Péter Makk
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
- Department of Physics, Budapest University of Technology and Economics and Nanoelectronics Momentum Research Group of the Hungarian Academy of Sciences, Budafoki ut 8, 1111 Budapest, Hungary
| | - Simon Zihlmann
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
| | - Andreas Baumgartner
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
- Swiss Nanoscience Institute, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
| | - David I Indolese
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
| | - Kenji Watanabe
- National Institute for Material Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - Takashi Taniguchi
- National Institute for Material Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - Christian Schönenberger
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
- Swiss Nanoscience Institute, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
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6
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Banszerus L, Möller S, Icking E, Watanabe K, Taniguchi T, Volk C, Stampfer C. Single-Electron Double Quantum Dots in Bilayer Graphene. NANO LETTERS 2020; 20:2005-2011. [PMID: 32083885 DOI: 10.1021/acs.nanolett.9b05295] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
We present transport measurements through an electrostatically defined bilayer graphene double quantum dot in the single-electron regime. With the help of a back gate, two split gates, and two finger gates, we are able to control the number of charge carriers on two gate-defined quantum dots independently between zero and five. The high tunability of the device meets requirements to make such a device a suitable building block for spin-qubits. In the single-electron regime, we determine interdot tunnel rates on the order of 2 GHz. Both, the interdot tunnel coupling as well as the capacitive interdot coupling increase with dot occupation, leading to the transition to a single quantum dot. Finite bias magneto-spectroscopy measurements allow to resolve the excited-state spectra of the first electrons in the double quantum dot and are in agreement with spin and valley conserving interdot tunneling processes.
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Affiliation(s)
- Luca Banszerus
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52074 Aachen, Germany
- Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, 52425 Jülich, Germany
| | - Samuel Möller
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52074 Aachen, Germany
- Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, 52425 Jülich, Germany
| | - 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
| | - Kenji Watanabe
- National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Christian Volk
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 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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7
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Nakamura H, Huang D, Merz J, Khalaf E, Ostrovsky P, Yaresko A, Samal D, Takagi H. Robust weak antilocalization due to spin-orbital entanglement in Dirac material Sr 3SnO. Nat Commun 2020; 11:1161. [PMID: 32127524 PMCID: PMC7054336 DOI: 10.1038/s41467-020-14900-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Accepted: 02/11/2020] [Indexed: 11/17/2022] Open
Abstract
The presence of both inversion (P) and time-reversal (T) symmetries in solids leads to a double degeneracy of the electronic bands (Kramers degeneracy). By lifting the degeneracy, spin textures manifest themselves in momentum space, as in topological insulators or in strong Rashba materials. The existence of spin textures with Kramers degeneracy, however, is difficult to observe directly. Here, we use quantum interference measurements to provide evidence for the existence of hidden entanglement between spin and momentum in the antiperovskite-type Dirac material Sr3SnO. We find robust weak antilocalization (WAL) independent of the position of EF. The observed WAL is fitted using a single interference channel at low doping, which implies that the different Dirac valleys are mixed by disorder. Notably, this mixing does not suppress WAL, suggesting contrasting interference physics compared to graphene. We identify scattering among axially spin-momentum locked states as a key process that leads to a spin-orbital entanglement.
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Affiliation(s)
- H Nakamura
- Max Planck Institute for Solid State Research, 70569, Stuttgart, Germany.
- Department of Physics, University of Arkansas, Fayetteville, AR, 72701, USA.
| | - D Huang
- Max Planck Institute for Solid State Research, 70569, Stuttgart, Germany
| | - J Merz
- Max Planck Institute for Solid State Research, 70569, Stuttgart, Germany
| | - E Khalaf
- Max Planck Institute for Solid State Research, 70569, Stuttgart, Germany
- Department of Physics, Harvard University, Cambridge, MA, 02138, USA
| | - P Ostrovsky
- Max Planck Institute for Solid State Research, 70569, Stuttgart, Germany
- L. D. Landau Institute for Theoretical Physics RAS, 119334, Moscow, Russia
| | - A Yaresko
- Max Planck Institute for Solid State Research, 70569, Stuttgart, Germany
| | - D Samal
- Institute of Physics, Bhubaneswar, 751005, India
- Homi Bhabha National Institute, Mumbai, 400085, India
| | - H Takagi
- Max Planck Institute for Solid State Research, 70569, Stuttgart, Germany
- Department of Physics, University of Tokyo, 113-0033, Tokyo, Japan
- Institute for Functional Matter and Quantum Technologies, University of Stuttgart, 70569, Stuttgart, Germany
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8
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Lee H, Park GH, Park J, Lee GH, Watanabe K, Taniguchi T, Lee HJ. Edge-Limited Valley-Preserved Transport in Quasi-1D Constriction of Bilayer Graphene. NANO LETTERS 2018; 18:5961-5966. [PMID: 30110547 DOI: 10.1021/acs.nanolett.8b02750] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We investigated the quantization of the conductance of quasi-one-dimensional (quasi-1D) constrictions in high-mobility bilayer graphene (BLG) with different geometrical aspect ratios. Ultrashort (a few tens of nanometers long) constrictions were fabricated by applying an under-cut etching technique. Conductance was quantized in steps of ∼4 e2/ h (∼2 e2/ h) in devices with aspect ratios smaller (larger) than 1. We argue that scattering at the edges of a quasi-1D BLG constriction limits the intervalley scattering length, which causes valley-preserved (valley-broken) quantum transport in devices with aspect ratios smaller (larger) than 1. The subband energy levels, analyzed in terms of the bias-voltage and temperature dependences of the quantized conductance, indicated that they corresponded well to the effective channel width of a physically defined conducting channel with a hard-wall confining potential. Our study in ultrashort high-mobility BLG nano constrictions with physically tailored edges clearly confirms that physical edges are the major source of intervalley scattering in graphene in the ballistic limit.
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Affiliation(s)
- Hyunwoo Lee
- Department of Physics , Pohang University of Science and Technology , Pohang , 37673 , Korea
| | - Geon-Hyoung Park
- Department of Physics , Pohang University of Science and Technology , Pohang , 37673 , Korea
| | - Jinho Park
- Department of Physics , Pohang University of Science and Technology , Pohang , 37673 , Korea
| | - Gil-Ho Lee
- Department of Physics , Pohang University of Science and Technology , Pohang , 37673 , Korea
| | - Kenji Watanabe
- National Institute for Material Science , Tsukuba , 305-0044 , Japan
| | - Takashi Taniguchi
- National Institute for Material Science , Tsukuba , 305-0044 , Japan
| | - Hu-Jong Lee
- Department of Physics , Pohang University of Science and Technology , Pohang , 37673 , Korea
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9
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Banszerus L, Frohn B, Epping A, Neumaier D, Watanabe K, Taniguchi T, Stampfer C. Gate-Defined Electron-Hole Double Dots in Bilayer Graphene. NANO LETTERS 2018; 18:4785-4790. [PMID: 29949375 DOI: 10.1021/acs.nanolett.8b01303] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
We present gate-controlled single-, double-, and triple-dot operation in electrostatically gapped bilayer graphene. Thanks to the recent advancements in sample fabrication, which include the encapsulation of bilayer graphene in hexagonal boron nitride and the use of graphite gates, it has become possible to electrostatically confine carriers in bilayer graphene and to completely pinch-off current through quantum dot devices. Here, we discuss the operation and characterization of electron-hole double dots. We show a remarkable degree of control of our device, which allows the implementation of two different gate-defined electron-hole double-dot systems with very similar energy scales. In the single-dot regime, we extract excited state energies and investigate their evolution in a parallel magnetic field, which is in agreement with a Zeeman-spin-splitting expected for a g-factor of 2.
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Affiliation(s)
- L Banszerus
- JARA-FIT and 2nd Institute of Physics , RWTH Aachen University , 52074 Aachen , Germany, European Union
- Peter Grünberg Institute (PGI-9) , Forschungszentrum Jülich , 52425 Jülich , Germany, European Union
| | - B Frohn
- JARA-FIT and 2nd Institute of Physics , RWTH Aachen University , 52074 Aachen , Germany, European Union
| | - A Epping
- JARA-FIT and 2nd Institute of Physics , RWTH Aachen University , 52074 Aachen , Germany, European Union
- Peter Grünberg Institute (PGI-9) , Forschungszentrum Jülich , 52425 Jülich , Germany, European Union
| | - D Neumaier
- AMO GmbH, Gesellschaft für Angewandte Mikro- und Optoelektronik , 52074 Aachen , Germany, European Union
| | - K Watanabe
- National Institute for Materials Science , 1-1 Namiki , Tsukuba , 305-0044 , Japan
| | - T Taniguchi
- National Institute for Materials Science , 1-1 Namiki , Tsukuba , 305-0044 , Japan
| | - C Stampfer
- JARA-FIT and 2nd Institute of Physics , RWTH Aachen University , 52074 Aachen , Germany, European Union
- Peter Grünberg Institute (PGI-9) , Forschungszentrum Jülich , 52425 Jülich , Germany, European Union
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10
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Tang S. Extracting the Energy Sensitivity of Charge Carrier Transport and Scattering. Sci Rep 2018; 8:10597. [PMID: 30006531 PMCID: PMC6045660 DOI: 10.1038/s41598-018-28288-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2017] [Accepted: 06/15/2018] [Indexed: 11/09/2022] Open
Abstract
It is a challenge to extract the energy sensitivity of charge carriers’ transport and scattering from experimental data, although a theoretical estimation in which the existing scattering mechanism(s) are preliminarily assumed can be easily done. To tackle this problem, we have developed a method to experimentally determine the energy sensitivities, which can then serve as an important statistical measurement to further understand the collective behaviors of multi-carrier transport systems. This method is validated using a graphene system at different temperatures. Further, we demonstrate the application of this method to other two-dimensional (2D) materials as a guide for future experimental work on the optimization of materials performance for electronic components, Peltier coolers, thermoelectricity generators, thermocouples, thermopiles, electrical converters and other conductivity and/or Seebeck-effect-related sensors.
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Affiliation(s)
- Shuang Tang
- College of Engineering, State University of New York, Polytechnic Institute, Albany, New York, 12203, USA.
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11
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Overweg H, Eggimann H, Liu MH, Varlet A, Eich M, Simonet P, Lee Y, Watanabe K, Taniguchi T, Richter K, Fal'ko VI, Ensslin K, Ihn T. Oscillating Magnetoresistance in Graphene p-n Junctions at Intermediate Magnetic Fields. NANO LETTERS 2017; 17:2852-2857. [PMID: 28383919 DOI: 10.1021/acs.nanolett.6b05318] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We report on the observation of magnetoresistance oscillations in graphene p-n junctions. The oscillations have been observed for six samples, consisting of single-layer and bilayer graphene, and persist up to temperatures of 30 K, where standard Shubnikov-de Haas oscillations are no longer discernible. The oscillatory magnetoresistance can be reproduced by tight-binding simulations. We attribute this phenomenon to the modulated densities of states in the n- and p-regions.
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Affiliation(s)
- Hiske Overweg
- Solid State Physics Laboratory, ETH Zürich , CH-8093 Zürich, Switzerland
| | - Hannah Eggimann
- Solid State Physics Laboratory, ETH Zürich , CH-8093 Zürich, Switzerland
| | - Ming-Hao Liu
- Institut für Theoretische Physik, Universität Regensburg , D-93040 Regensburg, Germany
- Department of Physics, National Cheng Kung University , Tainan 70101, Taiwan
| | - Anastasia Varlet
- Solid State Physics Laboratory, ETH Zürich , CH-8093 Zürich, Switzerland
| | - Marius Eich
- Solid State Physics Laboratory, ETH Zürich , CH-8093 Zürich, Switzerland
| | - Pauline Simonet
- Solid State Physics Laboratory, ETH Zürich , CH-8093 Zürich, Switzerland
| | - Yongjin Lee
- Solid State Physics Laboratory, ETH Zürich , CH-8093 Zürich, Switzerland
| | - Kenji Watanabe
- Advanced Materials Laboratory, National Institute for Material Science , 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- Advanced Materials Laboratory, National Institute for Material Science , 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Klaus Richter
- Institut für Theoretische Physik, Universität Regensburg , D-93040 Regensburg, Germany
| | - Vladimir I Fal'ko
- National Graphene Institute, University of Manchester , Manchester M13 9PL, United Kingdom
| | - Klaus Ensslin
- Solid State Physics Laboratory, ETH Zürich , CH-8093 Zürich, Switzerland
| | - Thomas Ihn
- Solid State Physics Laboratory, ETH Zürich , CH-8093 Zürich, Switzerland
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12
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Li J, Wang K, McFaul KJ, Zern Z, Ren Y, Watanabe K, Taniguchi T, Qiao Z, Zhu J. Gate-controlled topological conducting channels in bilayer graphene. NATURE NANOTECHNOLOGY 2016; 11:1060-1065. [PMID: 27570941 DOI: 10.1038/nnano.2016.158] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Accepted: 07/20/2016] [Indexed: 06/06/2023]
Abstract
The existence of inequivalent valleys K and K' in the momentum space of 2D hexagonal lattices provides a new electronic degree of freedom, the manipulation of which can potentially lead to new types of electronics, analogous to the role played by electron spin. In materials with broken inversion symmetry, such as an electrically gated bilayer graphene (BLG), the momentum-space Berry curvature Ω carries opposite sign in the K and K' valleys. A sign reversal of Ω along an internal boundary of the sheet gives rise to counterpropagating 1D conducting modes encoded with opposite-valley indices. These metallic states are topologically protected against backscattering in the absence of valley-mixing scattering, and thus can carry current ballistically. In BLG, the reversal of Ω can occur at the domain wall of AB- and BA-stacked domains, or at the line junction of two oppositely gated regions. The latter approach can provide a scalable platform to implement valleytronic operations, such as valves and waveguides, but it is technically challenging to realize. Here, we fabricate a dual-split-gate structure in BLG and present evidence of the predicted metallic states in electrical transport. The metallic states possess a mean free path (MFP) of up to a few hundred nanometres in the absence of a magnetic field. The application of a perpendicular magnetic field suppresses the backscattering significantly and enables a junction 400 nm in length to exhibit conductance close to the ballistic limit of 4e2/h at 8 T. Our experiment paves the way to the realization of gate-controlled ballistic valley transport and the development of valleytronic applications in atomically thin materials.
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Affiliation(s)
- Jing Li
- Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Ke Wang
- ICQD, Hefei National Laboratory for Physical Sciences at Microscale, and Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Kenton J McFaul
- Department of Electrical Engineering, Grove City College, Grove City, Pennsylvania 16127, USA
| | - Zachary Zern
- Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Yafei Ren
- ICQD, Hefei National Laboratory for Physical Sciences at Microscale, and Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Kenji Watanabe
- National Institute for Material Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- National Institute for Material Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Zhenhua Qiao
- ICQD, Hefei National Laboratory for Physical Sciences at Microscale, and Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Jun Zhu
- Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
- Center for 2-Dimensional and Layered Materials, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
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13
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Neumann C, Rizzi L, Reichardt S, Terrés B, Khodkov T, Watanabe K, Taniguchi T, Beschoten B, Stampfer C. Spatial Control of Laser-Induced Doping Profiles in Graphene on Hexagonal Boron Nitride. ACS APPLIED MATERIALS & INTERFACES 2016; 8:9377-9383. [PMID: 26986938 DOI: 10.1021/acsami.6b01727] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We present a method to create and erase spatially resolved doping profiles in graphene-hexagonal boron nitride heterostructures. The technique is based on photoinduced doping by a focused laser beam and does neither require masks nor photoresists. This makes our technique interesting for rapid prototyping of unconventional electronic device schemes, where the spatial resolution of the rewritable, long-term stable doping profiles is limited by only the laser spot size (≈600 nm) and the accuracy of sample positioning. Our optical doping method offers a way to implement and to test different, complex doping patterns in one and the very same graphene device, which is not achievable with conventional gating techniques.
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Affiliation(s)
- Christoph Neumann
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University , 52074 Aachen, Germany
- Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich , 52425 Jülich, Germany
| | - Leo Rizzi
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University , 52074 Aachen, Germany
| | - Sven Reichardt
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University , 52074 Aachen, Germany
- Physics and Materials Science Research Unit, Université du Luxembourg , 1511 Luxembourg, Luxembourg
| | - Bernat Terrés
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University , 52074 Aachen, Germany
- Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich , 52425 Jülich, Germany
| | - Timofiy Khodkov
- 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
- National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- 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
| | - 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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14
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Ghahari F, Xie HY, Taniguchi T, Watanabe K, Foster MS, Kim P. Enhanced Thermoelectric Power in Graphene: Violation of the Mott Relation by Inelastic Scattering. PHYSICAL REVIEW LETTERS 2016; 116:136802. [PMID: 27081996 DOI: 10.1103/physrevlett.116.136802] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/24/2016] [Indexed: 05/21/2023]
Abstract
We report the enhancement of the thermoelectric power (TEP) in graphene with extremely low disorder. At high temperature we observe that the TEP is substantially larger than the prediction of the Mott relation, approaching to the hydrodynamic limit due to strong inelastic scattering among the charge carriers. However, closer to room temperature the inelastic carrier-optical-phonon scattering becomes more significant and limits the TEP below the hydrodynamic prediction. We support our observation by employing a Boltzmann theory incorporating disorder, electron interactions, and optical phonons.
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Affiliation(s)
- Fereshte Ghahari
- Department of Physics, Columbia University, New York, New York 10027, USA
| | - Hong-Yi Xie
- Physics and Astronomy Department, Rice University, Houston, Texas 77005, USA
| | - Takashi Taniguchi
- National Institute for Material Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan
| | - Kenji Watanabe
- National Institute for Material Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan
| | - Matthew S Foster
- Physics and Astronomy Department, Rice University, Houston, Texas 77005, USA
- Rice Center for Quantum Materials, Rice University, Houston, Texas 77005, USA
| | - Philip Kim
- Department of Physics, Columbia University, New York, New York 10027, USA
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
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15
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Tien DH, Park JY, Kim KB, Lee N, Choi T, Kim P, Taniguchi T, Watanabe K, Seo Y. Study of Graphene-based 2D-Heterostructure Device Fabricated by All-Dry Transfer Process. ACS APPLIED MATERIALS & INTERFACES 2016; 8:3072-3078. [PMID: 26771834 DOI: 10.1021/acsami.5b10370] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We developed a technique for transferring graphene and hexagonal boron nitride (hBN) in dry conditions for fabrication of van der Waals heterostructures. The graphene layer was encapsulated between two hBN layers so that it was kept intact during fabrication of the device. For comparison, we also fabricated the devices containing graphene on SiO2/Si wafer and graphene on hBN. Electrical properties of the devices were investigated at room temperature. The mobility of the graphene on SiO2 devices and graphene on hBN devices were 15,000 and 37,000 cm(2) V(-1) s(-1), respectively, while the mobility of the sandwich structure device reached the highest value of ∼100,000 cm(2) V(-1) s(-1), at room temperature. The electrical measurements of the samples were carried out in air and vacuum environments. We found that the electrical properties of the encapsulated graphene devices remained at a similar level both in a vacuum and in air, whereas the properties of the graphene without encapsulation were influenced by the external environment.
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Affiliation(s)
- Dung Hoang Tien
- Faculty of Nanotechnology & Advanced Materials, HMC, and GRI, Sejong University , Seoul 143-747, South Korea
| | - Jun-Young Park
- Faculty of Nanotechnology & Advanced Materials, HMC, and GRI, Sejong University , Seoul 143-747, South Korea
| | - Ki Buem Kim
- Faculty of Nanotechnology & Advanced Materials, HMC, and GRI, Sejong University , Seoul 143-747, South Korea
| | - Naesung Lee
- Faculty of Nanotechnology & Advanced Materials, HMC, and GRI, Sejong University , Seoul 143-747, South Korea
| | - Taekjib Choi
- Faculty of Nanotechnology & Advanced Materials, HMC, and GRI, Sejong University , Seoul 143-747, South Korea
| | - Philip Kim
- Department of Physics, Harvard University , Cambridge, Massachusetts 02138, United States
| | | | - Kenji Watanabe
- National Institute of Materials Science , Ibaraki 305-0044, Japan
| | - Yongho Seo
- Faculty of Nanotechnology & Advanced Materials, HMC, and GRI, Sejong University , Seoul 143-747, South Korea
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16
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Schmidt H, Yudhistira I, Chu L, Castro Neto AH, Özyilmaz B, Adam S, Eda G. Quantum Transport and Observation of Dyakonov-Perel Spin-Orbit Scattering in Monolayer MoS_{2}. PHYSICAL REVIEW LETTERS 2016; 116:046803. [PMID: 26871351 DOI: 10.1103/physrevlett.116.046803] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2015] [Indexed: 06/05/2023]
Abstract
Monolayers of group 6 transition metal dichalcogenides are promising candidates for future spin-, valley-, and charge-based applications. Quantum transport in these materials reflects a complex interplay between real spin and pseudospin (valley) relaxation processes, which leads to either positive or negative quantum correction to the classical conductivity. Here we report experimental observation of a crossover from weak localization to weak antilocalization in highly n-doped monolayer MoS_{2}. We show that the crossover can be explained by a single parameter associated with electron spin lifetime of the system. At low temperatures and high carrier densities, the spin lifetime is inversely proportional to momentum relaxation time; this indicates that spin relaxation occurs via a Dyakonov-Perel mechanism.
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Affiliation(s)
- H Schmidt
- Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, 6 Science Drive 2, 117546 Singapore
- Department of Physics, National University of Singapore, 2 Science Drive 3, 117551 Singapore
| | - I Yudhistira
- Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, 6 Science Drive 2, 117546 Singapore
- Department of Physics, National University of Singapore, 2 Science Drive 3, 117551 Singapore
| | - L Chu
- Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, 6 Science Drive 2, 117546 Singapore
- Department of Physics, National University of Singapore, 2 Science Drive 3, 117551 Singapore
| | - A H Castro Neto
- Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, 6 Science Drive 2, 117546 Singapore
- Department of Physics, National University of Singapore, 2 Science Drive 3, 117551 Singapore
| | - B Özyilmaz
- Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, 6 Science Drive 2, 117546 Singapore
- Department of Physics, National University of Singapore, 2 Science Drive 3, 117551 Singapore
| | - S Adam
- Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, 6 Science Drive 2, 117546 Singapore
- Department of Physics, National University of Singapore, 2 Science Drive 3, 117551 Singapore
- Yale-NUS College, 16 College Ave West, 138527 Singapore
| | - G Eda
- Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, 6 Science Drive 2, 117546 Singapore
- Department of Physics, National University of Singapore, 2 Science Drive 3, 117551 Singapore
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, 117543 Singapore
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17
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Neumann C, Reichardt S, Drögeler M, Terrés B, Watanabe K, Taniguchi T, Beschoten B, Rotkin SV, Stampfer C. Low B field magneto-phonon resonances in single-layer and bilayer graphene. NANO LETTERS 2015; 15:1547-1552. [PMID: 25646665 DOI: 10.1021/nl5038825] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Many-body effects resulting from strong electron-electron and electron-phonon interactions play a significant role in graphene physics. We report on their manifestation in low B field magneto-phonon resonances in high-quality exfoliated single-layer and bilayer graphene encapsulated in hexagonal boron nitride. These resonances allow us to extract characteristic effective Fermi velocities, as high as 1.20 × 10(6) m/s, for the observed "dressed" Landau level transitions, as well as the broadening of the resonances, which increases with the Landau level index.
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Affiliation(s)
- Christoph Neumann
- JARA-FIT and 2nd Institute of Physics, RWTH Aachen University , 52074 Aachen, Germany
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