1
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Anderson LE, Laitinen A, Zimmerman A, Werkmeister T, Shackleton H, Kruchkov A, Taniguchi T, Watanabe K, Sachdev S, Kim P. Magneto-Thermoelectric Transport in Graphene Quantum Dot with Strong Correlations. PHYSICAL REVIEW LETTERS 2024; 132:246502. [PMID: 38949367 DOI: 10.1103/physrevlett.132.246502] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2024] [Revised: 05/01/2024] [Accepted: 05/07/2024] [Indexed: 07/02/2024]
Abstract
Disorder at etched edges of graphene quantum dots (GQD) enables random all-to-all interactions between localized charges in partially filled Landau levels, providing a potential platform to realize the Sachdev-Ye-Kitaev (SYK) model. We use quantum Hall edge states in the graphene electrodes to measure electrical conductance and thermoelectric power across the GQD. In specific temperature ranges, we observe a suppression of electric conductance fluctuations and slowly decreasing thermoelectric power across the GQD with increasing temperature, consistent with recent theory for the SYK regime.
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Affiliation(s)
| | | | | | | | | | - Alexander Kruchkov
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
- Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
- Institute of Physics, École Polytechnique Fédérale de Lausanne, Lausanne, CH 1015, Switzerland and Branco Weiss Society in Science, ETH Zurich, Zurich, CH 8092, Switzerland
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2
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Huang W, Braun O, Indolese DI, Barin GB, Gandus G, Stiefel M, Olziersky A, Müllen K, Luisier M, Passerone D, Ruffieux P, Schönenberger C, Watanabe K, Taniguchi T, Fasel R, Zhang J, Calame M, Perrin ML. Edge Contacts to Atomically Precise Graphene Nanoribbons. ACS NANO 2023; 17:18706-18715. [PMID: 37578964 PMCID: PMC10569104 DOI: 10.1021/acsnano.3c00782] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2023] [Accepted: 08/08/2023] [Indexed: 08/16/2023]
Abstract
Bottom-up-synthesized graphene nanoribbons (GNRs) are an emerging class of designer quantum materials that possess superior properties, including atomically controlled uniformity and chemically tunable electronic properties. GNR-based devices are promising candidates for next-generation electronic, spintronic, and thermoelectric applications. However, due to their extremely small size, making electrical contact with GNRs remains a major challenge. Currently, the most commonly used methods are top metallic electrodes and bottom graphene electrodes, but for both, the contact resistance is expected to scale with overlap area. Here, we develop metallic edge contacts to contact nine-atom-wide armchair GNRs (9-AGNRs) after encapsulation in hexagonal boron-nitride (h-BN), resulting in ultrashort contact lengths. We find that charge transport in our devices occurs via two different mechanisms: at low temperatures (9 K), charges flow through single GNRs, resulting in quantum dot (QD) behavior with well-defined Coulomb diamonds (CDs), with addition energies in the range of 16 to 400 meV. For temperatures above 100 K, a combination of temperature-activated hopping and polaron-assisted tunneling takes over, with charges being able to flow through a network of 9-AGNRs across distances significantly exceeding the length of individual GNRs. At room temperature, our short-channel field-effect transistor devices exhibit on/off ratios as high as 3 × 105 with on-state current up to 50 nA at 0.2 V. Moreover, we find that the contact performance of our edge-contact devices is comparable to that of top/bottom contact geometries but with a significantly reduced footprint. Overall, our work demonstrates that 9-AGNRs can be contacted at their ends in ultra-short-channel FET devices while being encapsulated in h-BN.
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Affiliation(s)
- Wenhao Huang
- Transport
at Nanoscale Interfaces Laboratory, Empa, Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland
- Department
of Physics, University of Basel, 4056 Basel, Switzerland
| | - Oliver Braun
- Transport
at Nanoscale Interfaces Laboratory, Empa, Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland
- Department
of Physics, University of Basel, 4056 Basel, Switzerland
| | | | - Gabriela Borin Barin
- nanotech@surfaces
Laboratory, Empa, Swiss Federal Laboratories
for Materials Science and Technology, 8600 Dübendorf, Switzerland
| | - Guido Gandus
- nanotech@surfaces
Laboratory, Empa, Swiss Federal Laboratories
for Materials Science and Technology, 8600 Dübendorf, Switzerland
- Department
of Information Technology and Electrical Engineering, ETH Zurich, 8092 Zurich, Switzerland
| | - Michael Stiefel
- Transport
at Nanoscale Interfaces Laboratory, Empa, Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland
| | | | - Klaus Müllen
- Max Planck
Institute for Polymer Research, 55128 Mainz, Germany
| | - Mathieu Luisier
- Department
of Information Technology and Electrical Engineering, ETH Zurich, 8092 Zurich, Switzerland
- Quantum Center, ETH Zürich, 8093 Zürich, Switzerland
| | - Daniele Passerone
- nanotech@surfaces
Laboratory, Empa, Swiss Federal Laboratories
for Materials Science and Technology, 8600 Dübendorf, Switzerland
| | - Pascal Ruffieux
- nanotech@surfaces
Laboratory, Empa, Swiss Federal Laboratories
for Materials Science and Technology, 8600 Dübendorf, Switzerland
| | | | - 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
| | - Roman Fasel
- nanotech@surfaces
Laboratory, Empa, Swiss Federal Laboratories
for Materials Science and Technology, 8600 Dübendorf, Switzerland
- Department
of Chemistry, Biochemistry and Pharmaceutical Science, University of Bern, 3012 Bern, Switzerland
| | - Jian Zhang
- Transport
at Nanoscale Interfaces Laboratory, Empa, Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland
| | - Michel Calame
- Transport
at Nanoscale Interfaces Laboratory, Empa, Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland
- Department
of Physics, University of Basel, 4056 Basel, Switzerland
- Swiss Nanoscience
Institute, University of Basel, 4056 Basel, Switzerland
| | - Mickael L. Perrin
- Transport
at Nanoscale Interfaces Laboratory, Empa, Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland
- Department
of Information Technology and Electrical Engineering, ETH Zurich, 8092 Zurich, Switzerland
- Quantum Center, ETH Zürich, 8093 Zürich, Switzerland
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3
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Zhang J, Qian L, Barin GB, Daaoub AHS, Chen P, Müllen K, Sangtarash S, Ruffieux P, Fasel R, Sadeghi H, Zhang J, Calame M, Perrin ML. Contacting individual graphene nanoribbons using carbon nanotube electrodes. NATURE ELECTRONICS 2023; 6:572-581. [PMID: 37636241 PMCID: PMC10449622 DOI: 10.1038/s41928-023-00991-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/07/2022] [Accepted: 06/09/2023] [Indexed: 08/29/2023]
Abstract
Graphene nanoribbons synthesized using bottom-up approaches can be structured with atomic precision, allowing their physical properties to be precisely controlled. For applications in quantum technology, the manipulation of single charges, spins or photons is required. However, achieving this at the level of single graphene nanoribbons is experimentally challenging due to the difficulty of contacting individual nanoribbons, particularly on-surface synthesized ones. Here we report the contacting and electrical characterization of on-surface synthesized graphene nanoribbons in a multigate device architecture using single-walled carbon nanotubes as the electrodes. The approach relies on the self-aligned nature of both nanotubes, which have diameters as small as 1 nm, and the nanoribbon growth on their respective growth substrates. The resulting nanoribbon-nanotube devices exhibit quantum transport phenomena-including Coulomb blockade, excited states of vibrational origin and Franck-Condon blockade-that indicate the contacting of individual graphene nanoribbons.
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Affiliation(s)
- Jian Zhang
- Transport at Nanoscale Interfaces Laboratory, Empa, Swiss Federal Laboratories for Materials Science and Technology, Dübendorf, Switzerland
| | - Liu Qian
- College of Chemistry and Molecular Engineering, Peking University, Beijing, China
| | - Gabriela Borin Barin
- nanotech@surfaces Laboratory, Empa, Swiss Federal Laboratories for Materials Science and Technology, Dübendorf, Switzerland
| | | | - Peipei Chen
- Nanofabrication Laboratory, National Center for Nanoscience and Technology, Beijing, China
| | - Klaus Müllen
- Max Planck Institute for Polymer Research, Mainz, Germany
| | | | - Pascal Ruffieux
- nanotech@surfaces Laboratory, Empa, Swiss Federal Laboratories for Materials Science and Technology, Dübendorf, Switzerland
| | - Roman Fasel
- nanotech@surfaces Laboratory, Empa, Swiss Federal Laboratories for Materials Science and Technology, Dübendorf, Switzerland
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Bern, Switzerland
| | - Hatef Sadeghi
- School of Engineering, University of Warwick, Coventry, UK
| | - Jin Zhang
- College of Chemistry and Molecular Engineering, Peking University, Beijing, China
| | - Michel Calame
- Transport at Nanoscale Interfaces Laboratory, Empa, Swiss Federal Laboratories for Materials Science and Technology, Dübendorf, Switzerland
- Department of Physics, University of Basel, Basel, Switzerland
- Swiss Nanoscience Institute, University of Basel, Basel, Switzerland
| | - Mickael L. Perrin
- Transport at Nanoscale Interfaces Laboratory, Empa, Swiss Federal Laboratories for Materials Science and Technology, Dübendorf, Switzerland
- Department of Information Technology and Electrical Engineering, ETH Zurich, Zurich, Switzerland
- Quantum Center, ETH Zurich, Zurich, Switzerland
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4
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Li X, Sui J, Fang J. Single-Electron Transport and Detection of Graphene Quantum Dots. NANOMATERIALS (BASEL, SWITZERLAND) 2023; 13:889. [PMID: 36903766 PMCID: PMC10005777 DOI: 10.3390/nano13050889] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/10/2023] [Revised: 02/22/2023] [Accepted: 02/24/2023] [Indexed: 06/18/2023]
Abstract
The integrated structure of graphene single-electron transistor and nanostrip electrometer was prepared using the semiconductor fabrication process. Through the electrical performance test of the large sample number, qualified devices were selected from low-yield samples, which exhibited an obvious Coulomb blockade effect. The results show that the device can deplete the electrons in the quantum dot structure at low temperatures, thus, accurately controlling the number of electrons captured by the quantum dot. At the same time, the nanostrip electrometer coupled with the quantum dot can be used to detect the quantum dot signal, that is, the change in the number of electrons in the quantum dot, because of its quantized conductivity characteristics.
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Affiliation(s)
- Xinxing Li
- School of Physics and Electronics, Central South University, Changsha 410083, China
- Key Laboratory of Nanodevices, Suzhou Institute of Nano-Tech and Nano-Bionics, CAS, Suzhou 215213, China
| | - Jinggao Sui
- National Innovation Institute of Defense Technology, Academy of Military Sciences PLA China, Beijing 100071, China
| | - Jingyue Fang
- School of Physics and Electronics, Central South University, Changsha 410083, China
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5
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Jin IK, Kumar K, Rendell MJ, Huang JY, Escott CC, Hudson FE, Lim WH, Dzurak AS, Hamilton AR, Liles SD. Combining n-MOS Charge Sensing with p-MOS Silicon Hole Double Quantum Dots in a CMOS platform. NANO LETTERS 2023; 23:1261-1266. [PMID: 36748989 DOI: 10.1021/acs.nanolett.2c04417] [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
Holes in silicon quantum dots are receiving attention due to their potential as fast, tunable, and scalable qubits in semiconductor quantum circuits. Despite this, challenges remain in this material system including difficulties using charge sensing to determine the number of holes in a quantum dot, and in controlling the coupling between adjacent quantum dots. We address these problems by fabricating an ambipolar complementary metal-oxide-semiconductor (CMOS) device using multilayer palladium gates. The device consists of an electron charge sensor adjacent to a hole double quantum dot. We demonstrate control of the spin state via electric dipole spin resonance. We achieve smooth control of the interdot coupling rate over 1 order of magnitude and use the charge sensor to perform spin-to-charge conversion to measure the hole singlet-triplet relaxation time of 11 μs for a known hole occupation. These results provide a path toward improving the quality and controllability of hole spin-qubits.
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Affiliation(s)
- Ik Kyeong Jin
- School of Physics, The University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Krittika Kumar
- School of Physics, The University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Matthew J Rendell
- School of Physics, The University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Jonathan Yue Huang
- School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney, New South Wales 2052, Australia
- Diraq, Sydney, New South Wales 2052, Australia
| | - Chris C Escott
- School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney, New South Wales 2052, Australia
- Diraq, Sydney, New South Wales 2052, Australia
| | - Fay E Hudson
- School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney, New South Wales 2052, Australia
- Diraq, Sydney, New South Wales 2052, Australia
| | - Wee Han Lim
- School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney, New South Wales 2052, Australia
- Diraq, Sydney, New South Wales 2052, Australia
| | - Andrew S Dzurak
- School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney, New South Wales 2052, Australia
- Diraq, Sydney, New South Wales 2052, Australia
| | - Alexander R Hamilton
- School of Physics, The University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Scott D Liles
- School of Physics, The University of New South Wales, Sydney, New South Wales 2052, Australia
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6
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Pal A, Zhang S, Chavan T, Agashiwala K, Yeh CH, Cao W, Banerjee K. Quantum-Engineered Devices Based on 2D Materials for Next-Generation Information Processing and Storage. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2022:e2109894. [PMID: 35468661 DOI: 10.1002/adma.202109894] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2021] [Revised: 04/11/2022] [Indexed: 06/14/2023]
Abstract
As an approximation to the quantum state of solids, the band theory, developed nearly seven decades ago, fostered the advance of modern integrated solid-state electronics, one of the most successful technologies in the history of human civilization. Nonetheless, their rapidly growing energy consumption and accompanied environmental issues call for more energy-efficient electronics and optoelectronics, which necessitate the exploration of more advanced quantum mechanical effects, such as band-to-band tunneling, spin-orbit coupling, spin-valley locking, and quantum entanglement. The emerging 2D layered materials, featured by their exotic electrical, magnetic, optical, and structural properties, provide a revolutionary low-dimensional and manufacture-friendly platform (and many more opportunities) to implement these quantum-engineered devices, compared to the traditional electronic materials system. Here, the progress in quantum-engineered devices is reviewed and the opportunities/challenges of exploiting 2D materials are analyzed to highlight their unique quantum properties that enable novel energy-efficient devices, and useful insights to quantum device engineers and 2D-material scientists are provided.
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Affiliation(s)
- Arnab Pal
- ECE Department, University of California, Santa Barbara, Santa Barbara, CA, 93106, USA
| | - Shuo Zhang
- ECE Department, University of California, Santa Barbara, Santa Barbara, CA, 93106, USA
- College of ISEE, Zhejiang University, Hangzhou, 310027, China
| | - Tanmay Chavan
- ECE Department, University of California, Santa Barbara, Santa Barbara, CA, 93106, USA
| | - Kunjesh Agashiwala
- ECE Department, University of California, Santa Barbara, Santa Barbara, CA, 93106, USA
| | - Chao-Hui Yeh
- ECE Department, University of California, Santa Barbara, Santa Barbara, CA, 93106, USA
| | - Wei Cao
- ECE Department, University of California, Santa Barbara, Santa Barbara, CA, 93106, USA
| | - Kaustav Banerjee
- ECE Department, University of California, Santa Barbara, Santa Barbara, CA, 93106, USA
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7
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Cully JJ, Swett JL, Willick K, Baugh J, Mol JA. Graphene nanogaps for the directed assembly of single-nanoparticle devices. NANOSCALE 2021; 13:6513-6520. [PMID: 33885530 DOI: 10.1039/d1nr01450a] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Significant advances in the synthesis of low-dimensional materials with unique and tuneable electrical, optical and magnetic properties has led to an explosion of possibilities for realising hybrid nanomaterial devices with unconventional and desirable characteristics. However, the lack of ability to precisely integrate individual nanoparticles into devices at scale limits their technological application. Here, we report on a graphene nanogap based platform which employs the large electric fields generated around the point-like, atomically sharp nanogap electrodes to capture single nanoparticles from solution at predefined locations. We demonstrate how gold nanoparticles can be trapped and contacted to form single-electron transistors with a large coupling to a buried electrostatic gate. This platform offers a route to the creation of novel low-dimensional devices, nano- and optoelectronic applications, and the study of fundamental transport phenomena.
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Affiliation(s)
- John J Cully
- Department of Materials, University of Oxford, UK.
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8
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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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9
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Caneva S, Hermans M, Lee M, García-Fuente A, Watanabe K, Taniguchi T, Dekker C, Ferrer J, van der Zant HSJ, Gehring P. A Mechanically Tunable Quantum Dot in a Graphene Break Junction. NANO LETTERS 2020; 20:4924-4931. [PMID: 32551676 PMCID: PMC7349654 DOI: 10.1021/acs.nanolett.0c00984] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/05/2020] [Revised: 06/18/2020] [Indexed: 06/11/2023]
Abstract
Graphene quantum dots (QDs) are intensively studied as platforms for the next generation of quantum electronic devices. Fine tuning of the transport properties in monolayer graphene QDs, in particular with respect to the independent modulation of the tunnel barrier transparencies, remains challenging and is typically addressed using electrostatic gating. We investigate charge transport in back-gated graphene mechanical break junctions and reveal Coulomb blockade physics characteristic of a single, high-quality QD when a nanogap is opened in a graphene constriction. By mechanically controlling the distance across the newly formed graphene nanogap, we achieve reversible tunability of the tunnel coupling to the drain electrode by 5 orders of magnitude, while keeping the source-QD tunnel coupling constant. The break junction device can therefore become a powerful platform to study the physical parameters that are crucial to the development of future graphene-based devices, including energy converters and quantum calorimeters.
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Affiliation(s)
- Sabina Caneva
- Kavli
Institute of Nanotechnology, Lorentzweg 1, 2628
CJ Delft, The Netherlands
| | - Matthijs Hermans
- Kavli
Institute of Nanotechnology, Lorentzweg 1, 2628
CJ Delft, The Netherlands
| | - Martin Lee
- Kavli
Institute of Nanotechnology, Lorentzweg 1, 2628
CJ Delft, The Netherlands
| | - Amador García-Fuente
- Departamento
de Física, Universidad de Oviedo, 33007 Oviedo, Spain
- Centro
de Investigación en Nanomateriales y Nanotecnología, Universidad de Oviedo − CSIC, 33940 El Entrego, Spain
| | - 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
| | - Cees Dekker
- Kavli
Institute of Nanotechnology, Lorentzweg 1, 2628
CJ Delft, The Netherlands
| | - Jaime Ferrer
- Departamento
de Física, Universidad de Oviedo, 33007 Oviedo, Spain
- Centro
de Investigación en Nanomateriales y Nanotecnología, Universidad de Oviedo − CSIC, 33940 El Entrego, Spain
| | | | - Pascal Gehring
- Kavli
Institute of Nanotechnology, Lorentzweg 1, 2628
CJ Delft, The Netherlands
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10
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Iwasaki T, Nakaharai S, Wakayama Y, Watanabe K, Taniguchi T, Morita Y, Moriyama S. Single-Carrier Transport in Graphene/hBN Superlattices. NANO LETTERS 2020; 20:2551-2557. [PMID: 32186384 DOI: 10.1021/acs.nanolett.9b05332] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Graphene/hexagonal boron nitride (hBN) moiré superlattices have attracted interest for use in the study of many-body effects and fractal physics in Dirac fermion systems. Many exotic transport properties have been intensively examined in such superlattices, but previous studies have not focused on single-carrier transport. The investigation of the single-carrier behavior in these superlattices would lead to an understanding of the transition of single-particle/correlated phenomena. Here, we show the single-carrier transport in a high-quality bilayer graphene/hBN superlattice-based quantum dot device. We demonstrate remarkable device controllability in the energy range near the charge neutrality point (CNP) and the hole-side satellite point. Under a perpendicular magnetic field, Coulomb oscillations disappear near the CNP, which could be a signature of the crossover between Coulomb blockade and quantum Hall regimes. Our results pave the way for exploring the relationship of single-electron transport and fractal quantum Hall effects with correlated phenomena in two-dimensional quantum materials.
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Affiliation(s)
- Takuya Iwasaki
- International Center for Young Scientists (ICYS), National Institute for Materials Science (NIMS), Tsukuba, Ibaraki 305-0044, Japan
- International Center for Materials Nanoarchitectonics (WPI-MANA), NIMS, Tsukuba, Ibaraki 305-0044, Japan
| | - Shu Nakaharai
- International Center for Materials Nanoarchitectonics (WPI-MANA), NIMS, Tsukuba, Ibaraki 305-0044, Japan
| | - Yutaka Wakayama
- International Center for Materials Nanoarchitectonics (WPI-MANA), NIMS, Tsukuba, Ibaraki 305-0044, Japan
| | - Kenji Watanabe
- Research Center for Functional Materials, NIMS, Tsukuba, Ibaraki 305-0044, Japan
| | - Takashi Taniguchi
- Research Center for Functional Materials, NIMS, Tsukuba, Ibaraki 305-0044, Japan
| | - Yoshifumi Morita
- Faculty of Engineering, Gunma University, Kiryu, Gunma 376-8515, Japan
| | - Satoshi Moriyama
- International Center for Materials Nanoarchitectonics (WPI-MANA), NIMS, Tsukuba, Ibaraki 305-0044, Japan
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11
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Kim G, Kim SS, Jeon J, Yoon SI, Hong S, Cho YJ, Misra A, Ozdemir S, Yin J, Ghazaryan D, Holwill M, Mishchenko A, Andreeva DV, Kim YJ, Jeong HY, Jang AR, Chung HJ, Geim AK, Novoselov KS, Sohn BH, Shin HS. Planar and van der Waals heterostructures for vertical tunnelling single electron transistors. Nat Commun 2019; 10:230. [PMID: 30651554 PMCID: PMC6335417 DOI: 10.1038/s41467-018-08227-1] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2018] [Accepted: 12/23/2018] [Indexed: 11/09/2022] Open
Abstract
Despite a rich choice of two-dimensional materials, which exists these days, heterostructures, both vertical (van der Waals) and in-plane, offer an unprecedented control over the properties and functionalities of the resulted structures. Thus, planar heterostructures allow p-n junctions between different two-dimensional semiconductors and graphene nanoribbons with well-defined edges; and vertical heterostructures resulted in the observation of superconductivity in purely carbon-based systems and realisation of vertical tunnelling transistors. Here we demonstrate simultaneous use of in-plane and van der Waals heterostructures to build vertical single electron tunnelling transistors. We grow graphene quantum dots inside the matrix of hexagonal boron nitride, which allows a dramatic reduction of the number of localised states along the perimeter of the quantum dots. The use of hexagonal boron nitride tunnel barriers as contacts to the graphene quantum dots make our transistors reproducible and not dependent on the localised states, opening even larger flexibility when designing future devices.
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Affiliation(s)
- Gwangwoo Kim
- Department of Energy Engineering, Ulsan National Institute of Science & Technology (UNIST), Ulsan, 44919, Republic of Korea
| | - Sung-Soo Kim
- Department of Chemistry, Seoul National University, Seoul, 08826, Republic of Korea.,Carbon Composite Materials Research Center, Korea Institute of Science and Technology (KIST), Wanju, 55324, Republic of Korea
| | - Jonghyuk Jeon
- Department of Chemistry, Seoul National University, Seoul, 08826, Republic of Korea
| | - Seong In Yoon
- Department of Energy Engineering, Ulsan National Institute of Science & Technology (UNIST), Ulsan, 44919, Republic of Korea
| | - Seokmo Hong
- Department of Chemistry, UNIST, Ulsan, 44919, Republic of Korea
| | - Young Jin Cho
- Department of Physics, Konkuk University, Seoul, 05029, Republic of Korea
| | - Abhishek Misra
- School of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, United Kingdom.,Department of Physics, Indian Institute of Technology Madras, Chennai, 600036, India
| | - Servet Ozdemir
- School of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, United Kingdom
| | - Jun Yin
- School of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, United Kingdom
| | - Davit Ghazaryan
- School of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, United Kingdom.,Department of Physics, National Research University Higher School of Economics, Staraya Basmannaya 21/4, Moscow, 105066, Russian Federation
| | - Matthew Holwill
- School of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, United Kingdom
| | - Artem Mishchenko
- School of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, United Kingdom
| | - Daria V Andreeva
- Department of Materials Science and Engineering, National University of Singapore, Singapore, 117575, Singapore
| | - Yong-Jin Kim
- Center for Multidimensional Carbon Materials, Institute of Basic Science (IBS), Ulsan, 44919, Republic of Korea
| | - Hu Young Jeong
- UNIST Central Research Facilities (UCRF), UNIST, Ulsan, 44919, Republic of Korea
| | - A-Rang Jang
- Department of Energy Engineering, Ulsan National Institute of Science & Technology (UNIST), Ulsan, 44919, Republic of Korea.,Department of Chemistry, UNIST, Ulsan, 44919, Republic of Korea
| | - Hyun-Jong Chung
- Department of Physics, Konkuk University, Seoul, 05029, Republic of Korea
| | - Andre K Geim
- School of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, United Kingdom
| | - Kostya S Novoselov
- School of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, United Kingdom.
| | - Byeong-Hyeok Sohn
- Department of Chemistry, Seoul National University, Seoul, 08826, Republic of Korea.
| | - Hyeon Suk Shin
- Department of Energy Engineering, Ulsan National Institute of Science & Technology (UNIST), Ulsan, 44919, Republic of Korea. .,Department of Chemistry, UNIST, Ulsan, 44919, Republic of Korea. .,Center for Multidimensional Carbon Materials, Institute of Basic Science (IBS), Ulsan, 44919, Republic of Korea. .,Low Dimensional Carbon Material Center, UNIST, Ulsan, 44919, Republic of Korea.
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12
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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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13
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Zhang GQ, Kang N, Li JY, Lin L, Peng H, Liu Z, Xu HQ. Low-field magnetotransport in graphene cavity devices. NANOTECHNOLOGY 2018; 29:205707. [PMID: 29509145 DOI: 10.1088/1361-6528/aab478] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Confinement and edge structures are known to play significant roles in the electronic and transport properties of two-dimensional materials. Here, we report on low-temperature magnetotransport measurements of lithographically patterned graphene cavity nanodevices. It is found that the evolution of the low-field magnetoconductance characteristics with varying carrier density exhibits different behaviors in graphene cavity and bulk graphene devices. In the graphene cavity devices, we observed that intravalley scattering becomes dominant as the Fermi level gets close to the Dirac point. We associate this enhanced intravalley scattering to the effect of charge inhomogeneities and edge disorder in the confined graphene nanostructures. We also observed that the dephasing rate of carriers in the cavity devices follows a parabolic temperature dependence, indicating that the direct Coulomb interaction scattering mechanism governs the dephasing at low temperatures. Our results demonstrate the importance of confinement in carrier transport in graphene nanostructure devices.
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Affiliation(s)
- G Q Zhang
- Beijing Key Laboratory of Quantum Devices, Key Laboratory for the Physics and Chemistry of Nanodevices and Department of Electronics, Peking University, Beijing 100871, People's Republic of China
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14
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Spruijtenburg PC, Amitonov SV, Wiel WGVD, Zwanenburg FA. A fabrication guide for planar silicon quantum dot heterostructures. NANOTECHNOLOGY 2018; 29:143001. [PMID: 29384491 DOI: 10.1088/1361-6528/aaabf5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We describe important considerations to create top-down fabricated planar quantum dots in silicon, often not discussed in detail in literature. The subtle interplay between intrinsic material properties, interfaces and fabrication processes plays a crucial role in the formation of electrostatically defined quantum dots. Processes such as oxidation, physical vapor deposition and atomic-layer deposition must be tailored in order to prevent unwanted side effects such as defects, disorder and dewetting. In two directly related manuscripts written in parallel we use techniques described in this work to create depletion-mode quantum dots in intrinsic silicon, and low-disorder silicon quantum dots defined with palladium gates. While we discuss three different planar gate structures, the general principles also apply to 0D and 1D systems, such as self-assembled islands and nanowires.
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Affiliation(s)
- Paul C Spruijtenburg
- NanoElectronics Group, MESA+ Institute for Nanotechnology, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands
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15
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Xiong H, Jiang W, Song Y, Duan L. Bound state properties of ABC-stacked trilayer graphene quantum dots. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:215002. [PMID: 28367830 DOI: 10.1088/1361-648x/aa6aac] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The few-layer graphene quantum dot provides a promising platform for quantum computing with both spin and valley degrees of freedom. Gate-defined quantum dots in particular can avoid noise from edge disorders. In connection with the recent experimental efforts (Song et al 2016 Nano Lett. 16 6245), we investigate the bound state properties of trilayer graphene (TLG) quantum dots (QDs) through numerical simulations. We show that the valley degeneracy can be lifted by breaking the time reversal symmetry through the application of a perpendicular magnetic field. The spectrum under such a potential exhibits a transition from one group of Landau levels to another group, which can be understood analytically through perturbation theory. Our results provide insight into the transport property of TLG QDs, with possible applications to study of spin qubits and valleytronics in TLG QDs.
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Affiliation(s)
- Haonan Xiong
- Department of Physics, Tsinghua University, Beijing 100084, People's Republic of China. Center for Quantum Information, IIIS, Tsinghua University, Beijing 100084, People's Republic of China
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16
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Song Y, Xiong H, Jiang W, Zhang H, Xue X, Ma C, Ma Y, Sun L, Wang H, Duan L. Coulomb Oscillations in a Gate-Controlled Few-Layer Graphene Quantum Dot. NANO LETTERS 2016; 16:6245-6251. [PMID: 27632023 DOI: 10.1021/acs.nanolett.6b02522] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Graphene quantum dots could be an ideal host for spin qubits and thus have been extensively investigated based on graphene nanoribbons and etched nanostructures; however, edge and substrate-induced disorders severely limit device functionality. Here, we report the confinement of quantum dots in few-layer graphene with tunable barriers, defined by local strain and electrostatic gating. Transport measurements unambiguously reveal that confinement barriers are formed by inducing a band gap via the electrostatic gating together with local strain induced constriction. Numerical simulations according to the local top-gate geometry confirm the band gap opening by a perpendicular electric field. We investigate the magnetic field dependence of the energy-level spectra in these graphene quantum dots. Experimental results reveal a complex evolution of Coulomb oscillations with the magnetic field, featuring kinks at level crossings. The simulation of energy spectrum shows that the kink features and the magnetic field dependence are consistent with experimental observations, implying the hybridized nature of energy-level spectrum of these graphene quantum dots.
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Affiliation(s)
- Yipu Song
- Center for Quantum Information, IIIS, Tsinghua University , Beijing 100084, China
| | - Haonan Xiong
- Center for Quantum Information, IIIS, Tsinghua University , Beijing 100084, China
- Department of Physics, Tsinghua University , Beijing 100084, China
| | - Wentao Jiang
- Center for Quantum Information, IIIS, Tsinghua University , Beijing 100084, China
- Department of Physics, Tsinghua University , Beijing 100084, China
| | - Hongyi Zhang
- Center for Quantum Information, IIIS, Tsinghua University , Beijing 100084, China
| | - Xiao Xue
- Center for Quantum Information, IIIS, Tsinghua University , Beijing 100084, China
| | - Cheng Ma
- Center for Quantum Information, IIIS, Tsinghua University , Beijing 100084, China
| | - Yulin Ma
- Center for Quantum Information, IIIS, Tsinghua University , Beijing 100084, China
| | - Luyan Sun
- Center for Quantum Information, IIIS, Tsinghua University , Beijing 100084, China
| | - Haiyan Wang
- Center for Quantum Information, IIIS, Tsinghua University , Beijing 100084, China
| | - Luming Duan
- Center for Quantum Information, IIIS, Tsinghua University , Beijing 100084, China
- Department of Physics, University of Michigan , Ann Arbor, Michigan 48109, United States
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17
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Chung HC, Chang CP, Lin CY, Lin MF. Electronic and optical properties of graphene nanoribbons in external fields. Phys Chem Chem Phys 2016; 18:7573-616. [PMID: 26744847 DOI: 10.1039/c5cp06533j] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
A review work is done for the electronic and optical properties of graphene nanoribbons in magnetic, electric, composite, and modulated fields. Effects due to the lateral confinement, curvature, stacking, non-uniform subsystems and hybrid structures are taken into account. The special electronic properties, induced by complex competitions between external fields and geometric structures, include many one-dimensional parabolic subbands, standing waves, peculiar edge-localized states, width- and field-dependent energy gaps, magnetic-quantized quasi-Landau levels, curvature-induced oscillating Landau subbands, crossings and anti-crossings of quasi-Landau levels, coexistence and combination of energy spectra in layered structures, and various peak structures in the density of states. There exist diverse absorption spectra and different selection rules, covering edge-dependent selection rules, magneto-optical selection rule, splitting of the Landau absorption peaks, intragroup and intergroup Landau transitions, as well as coexistence of monolayer-like and bilayer-like Landau absorption spectra. Detailed comparisons are made between the theoretical calculations and experimental measurements. The predicted results, the parabolic subbands, edge-localized states, gap opening and modulation, and spatial distribution of Landau subbands, have been identified by various experimental measurements.
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Affiliation(s)
- Hsien-Ching Chung
- Department of Physics, National Cheng Kung University, Tainan 70101, Taiwan. and Center for Micro/Nano Science and Technology (CMNST), National Cheng Kung University, Tainan 70101, Taiwan
| | - Cheng-Peng Chang
- Center for General Education, Tainan University of Technology, Tainan 701, Taiwan
| | - Chiun-Yan Lin
- Department of Physics, National Cheng Kung University, Tainan 70101, Taiwan.
| | - Ming-Fa Lin
- Department of Physics, National Cheng Kung University, Tainan 70101, Taiwan.
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18
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The effect of magnetic field on chiral transmission in p-n-p graphene junctions. Sci Rep 2015; 5:18458. [PMID: 26679991 PMCID: PMC4683455 DOI: 10.1038/srep18458] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2015] [Accepted: 11/18/2015] [Indexed: 11/10/2022] Open
Abstract
We investigate Klein tunneling in graphene heterojunctions under the influence of a perpendicular magnetic field via the non-equilibrium Green’s function method. We find that the angular dependence of electron transmission is deflected sideways, resulting in the suppression of normally incident electrons and overall decrease in conductance. The off-normal symmetry axis of the transmission profile was analytically derived. Overall tunneling conductance decreases to almost zero regardless of the potential barrier height when the magnetic field (B-field) exceeds a critical value, thus achieving effective confinement of Dirac fermions. The critical field occurs when the width of the magnetic field region matches the diameter of the cyclotron orbit. The potential barrier also induces distinct Fabry-Pérot fringe patterns, with a “constriction region” of low transmission when is close to the Fermi energy. Application of B-field deflects the Fabry-Pérot interference pattern to an off-normal angle. Thus, the conductance of the graphene heterojunctions can be sharply modulated by adjusting the B-field strength and the potential barrier height relative to the Fermi energy.
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19
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Mueller F, Konstantaras G, Spruijtenburg PC, van der Wiel WG, Zwanenburg FA. Electron-Hole Confinement Symmetry in Silicon Quantum Dots. NANO LETTERS 2015; 15:5336-5341. [PMID: 26134900 DOI: 10.1021/acs.nanolett.5b01706] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We report electrical transport measurements on a gate-defined ambipolar quantum dot in intrinsic silicon. The ambipolarity allows its operation as either an electron or a hole quantum dot of which we change the dot occupancy by 20 charge carriers in each regime. Electron-hole confinement symmetry is evidenced by the extracted gate capacitances and charging energies. The results demonstrate that ambipolar quantum dots offer great potential for spin-based quantum information processing, since confined electrons and holes can be compared and manipulated in the same crystalline environment.
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Affiliation(s)
- Filipp Mueller
- NanoElectronics Group, MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - Georgios Konstantaras
- NanoElectronics Group, MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - Paul C Spruijtenburg
- NanoElectronics Group, MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - Wilfred G van der Wiel
- NanoElectronics Group, MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - Floris A Zwanenburg
- NanoElectronics Group, MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
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20
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Lee YL. Electrical transport through a quantum dot side-coupled to a topological superconductor. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2014; 26:455702. [PMID: 25327622 DOI: 10.1088/0953-8984/26/45/455702] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We propose to measure the differential conductance G as a function of the bias V for a quantum dot side-coupled to a topological superconductor to detect the existence of the chiral Majorana edge states. It turns out that G for the spinless dot is an oscillatory (but not periodic) function of eV due to the coupling to the chiral Majorana edge states, where -e is the charge carried by the electron. The behaviour of G versus eV is distinguished from that of a multi-level dot in three respects. First of all, due to the coupling to the topological superconductor, the value of G will shift upon adding or removing a vortex in the topological superconductor. Next, for an off-resonance dot, the conductance peak in the present case takes a universal value e(2)/(2h) when the two leads are symmetrically coupled to the dot. Finally, for a symmetric setup and an on-resonance dot, the conductance peak will approach the same universal value e(2)/(2h) at a large bias.
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Affiliation(s)
- Yu-Li Lee
- Department of Physics, National Changhua University of Education, Changhua, Taiwan, People's Republic of China
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21
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Zhu RJ, Huang YQ, Kang N, Xu HQ. Gate tunable nonlinear rectification effects in three-terminal graphene nanojunctions. NANOSCALE 2014; 6:4527-4531. [PMID: 24658185 DOI: 10.1039/c3nr06404b] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We report on a study of the room-temperature nonlinear charge transport properties of three-terminal junction devices made from graphene. We demonstrate that the graphene three terminal junction devices show a rectification characteristic, namely, when voltages VL = V and VR = -V are applied to the left and the right terminal in a push-pull configuration, the voltage output from the central terminal VC is finite and is scaled approximately with V(2). The rectification coefficient can be effectively tuned by a gate voltage and shows a transport carrier polarity dependence. We further show that the nonlinear charge transport characteristics can be used to probe the electronic structure of graphene nanostructures and to study the thermoelectrical power of graphene. These results show that the graphene three-terminal junction devices could be used as novel building blocks for nanoelectronics and as novel devices for the study of the material properties of graphene on the nanoscale.
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Affiliation(s)
- R J Zhu
- School of Physics and Optoelectronic Technology, College of Advanced Science and Technology, Dalian University of Technology, Dalian 116024, China
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22
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Volk C, Neumann C, Kazarski S, Fringes S, Engels S, Haupt F, Müller A, Stampfer C. Probing relaxation times in graphene quantum dots. Nat Commun 2013; 4:1753. [PMID: 23612294 PMCID: PMC3644082 DOI: 10.1038/ncomms2738] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2012] [Accepted: 03/14/2013] [Indexed: 11/10/2022] Open
Abstract
Graphene quantum dots are attractive candidates for solid-state quantum bits. In fact, the predicted weak spin-orbit and hyperfine interaction promise spin qubits with long coherence times. Graphene quantum dots have been extensively investigated with respect to their excitation spectrum, spin-filling sequence and electron-hole crossover. However, their relaxation dynamics remain largely unexplored. This is mainly due to challenges in device fabrication, in particular concerning the control of carrier confinement and the tunability of the tunnelling barriers, both crucial to experimentally investigate decoherence times. Here we report pulsed-gate transient current spectroscopy and relaxation time measurements of excited states in graphene quantum dots. This is achieved by an advanced device design that allows to individually tune the tunnelling barriers down to the low megahertz regime, while monitoring their asymmetry. Measuring transient currents through electronic excited states, we estimate a lower bound for charge relaxation times on the order of 60-100 ns.
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Affiliation(s)
- Christian Volk
- JARA-FIT and II Institute of Physics B, RWTH Aachen, 52074 Aachen, Germany
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23
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Güttinger J, Molitor F, Stampfer C, Schnez S, Jacobsen A, Dröscher S, Ihn T, Ensslin K. Transport through graphene quantum dots. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2012; 75:126502. [PMID: 23144122 DOI: 10.1088/0034-4885/75/12/126502] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We review transport experiments on graphene quantum dots and narrow graphene constrictions. In a quantum dot, electrons are confined in all lateral dimensions, offering the possibility for detailed investigation and controlled manipulation of individual quantum systems. The recently isolated two-dimensional carbon allotrope graphene is an interesting host to study quantum phenomena, due to its novel electronic properties and the expected weak interaction of the electron spin with the material. Graphene quantum dots are fabricated by etching mono-layer flakes into small islands (diameter 60-350 nm) with narrow connections to contacts (width 20-75 nm), serving as tunneling barriers for transport spectroscopy. Electron confinement in graphene quantum dots is observed by measuring Coulomb blockade and transport through excited states, a manifestation of quantum confinement. Measurements in a magnetic field perpendicular to the sample plane allowed to identify the regime with only a few charge carriers in the dot (electron-hole transition), and the crossover to the formation of the graphene specific zero-energy Landau level at high fields. After rotation of the sample into parallel magnetic field orientation, Zeeman spin splitting with a g-factor of g ≈ 2 is measured. The filling sequence of subsequent spin states is similar to what was found in GaAs and related to the non-negligible influence of exchange interactions among the electrons.
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Affiliation(s)
- J Güttinger
- Solid State Physics Laboratory, ETH Zurich, 8092 Zurich, Switzerland.
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24
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Tuning charge and spin excitations in zigzag edge nanographene ribbons. Sci Rep 2012; 2:519. [PMID: 22816042 PMCID: PMC3399123 DOI: 10.1038/srep00519] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2012] [Accepted: 06/27/2012] [Indexed: 11/08/2022] Open
Abstract
Graphene and its quasi-one-dimensional counterpart, graphene nanoribbons, present an ideal platform for tweaking their unique electronic, magnetic and mechanical properties by various means for potential next-generation device applications. However, such tweaking requires knowledge of the electron-electron interactions that play a crucial role in these confined geometries. Here, we have investigated the magnetic and conducting properties of zigzag edge graphene nanoribbons (ZGNRs) using the many-body configuration interaction (CI) method on the basis of the Hubbard Hamiltonian. For the half-filled case, the many-body ground state shows a ferromagnetic spin-spin correlation along the zigzag edge, which supports the picture obtained from one-electron theory. However, hole doping reduces the spin and charge excitation gap, making the ground state conducting and magnetic. We also provide a two-state model that explains the low-lying charge and spin excitation spectrum of ZGNRs. An experimental setup to confirm the hole-mediated conducting and magnetic states is discussed.
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25
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Klimov NN, Jung S, Zhu S, Li T, Wright CA, Solares SD, Newell DB, Zhitenev NB, Stroscio JA. Electromechanical Properties of Graphene Drumheads. Science 2012; 336:1557-61. [DOI: 10.1126/science.1220335] [Citation(s) in RCA: 241] [Impact Index Per Article: 20.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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26
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Yamamoto M, Wakabayashi K. Magnetic response of conductance peak structure in junction-confined graphene nanoribbons. NANOSCALE 2012; 4:1138-1145. [PMID: 22080960 DOI: 10.1039/c1nr11056j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We have numerically investigated the magnetic response of the conductance peak structures in the transport gap of graphene nanoribbons. It is shown that the magnetic field induces a number of new conductance peaks within the transport gap of graphene nanoribbons confined by structural junctions. In addition, the magnetic field causes a shift of the conductance peak position and broadening of the peak width. This behaviour is due to the disappearance of zero conductance dips at the junction as a result of breaking time-reversal symmetry. Such behaviour is, however, not observed in the electronic transport of graphene nanoribbons confined by potential barriers, i.e. p-n-junctions. Thus, the magnetic response of conductance peaks may be used to distinguish the origin of the conductance peak structure within the transport gap observed in the experiments.
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Affiliation(s)
- Masayuki Yamamoto
- International Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), Namiki 1-1, Tsukuba, 305-0044, Ibaraki, Japan
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Subramaniam D, Libisch F, Li Y, Pauly C, Geringer V, Reiter R, Mashoff T, Liebmann M, Burgdörfer J, Busse C, Michely T, Mazzarello R, Pratzer M, Morgenstern M. Wave-function mapping of graphene quantum dots with soft confinement. PHYSICAL REVIEW LETTERS 2012; 108:046801. [PMID: 22400872 DOI: 10.1103/physrevlett.108.046801] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2011] [Indexed: 05/31/2023]
Abstract
Using low-temperature scanning tunneling spectroscopy, we map the local density of states of graphene quantum dots supported on Ir(111). Because of a band gap in the projected Ir band structure around the graphene K point, the electronic properties of the QDs are dominantly graphenelike. Indeed, we compare the results favorably with tight binding calculations on the honeycomb lattice based on parameters derived from density functional theory. We find that the interaction with the substrate near the edge of the island gradually opens a gap in the Dirac cone, which implies soft-wall confinement. Interestingly, this confinement results in highly symmetric wave functions. Further influences of the substrate are given by the known moiré potential and a 10% penetration of an Ir surface resonance into the graphene layer.
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Affiliation(s)
- D Subramaniam
- II Physikalisches Institut B and JARA-FIT, RWTH Aachen University, D-52074 Aachen, Germany
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28
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Volk C, Fringes S, Terrés B, Dauber J, Engels S, Trellenkamp S, Stampfer C. Electronic excited states in bilayer graphene double quantum dots. NANO LETTERS 2011; 11:3581-3586. [PMID: 21805985 DOI: 10.1021/nl201295s] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We report tunneling spectroscopy experiments on a bilayer graphene double quantum dot device that can be tuned by all-graphene lateral gates. The diameter of the two quantum dots are around 50 nm and the constrictions acting as tunneling barriers are 30 nm in width. The double quantum dot features additional energies on the order of 20 meV. Charge stability diagrams allow us to study the tunable interdot coupling energy as well as the spectrum of the electronic excited states on a number of individual triple points over a large energy range. The obtained constant level spacing of 1.75 meV over a wide energy range is in good agreement with the expected single-particle energy spacing in bilayer graphene quantum dots. Finally, we investigate the evolution of the electronic excited states in a parallel magnetic field.
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Affiliation(s)
- C Volk
- JARA-FIT and II. Institute of Physics B, RWTH Aachen University, 52074 Aachen, Germany
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29
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Molitor F, Güttinger J, Stampfer C, Dröscher S, Jacobsen A, Ihn T, Ensslin K. Electronic properties of graphene nanostructures. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2011; 23:243201. [PMID: 21613728 DOI: 10.1088/0953-8984/23/24/243201] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
In this review, recent developments in the fabrication and understanding of the electronic properties of graphene nanostructures are discussed. After a brief overview of the structure of graphene and the two-dimensional transport properties, the focus is put on graphene constrictions, quantum dots and double quantum dots. For constrictions with a width below 100 nm, the current through the constriction is strongly suppressed for a certain back gate voltage range, related to the so-called transport gap. This transport gap is due to the formation of localized puddles in the constriction, and its size depends strongly on the constriction width. Such constrictions can be used to confine charge carriers in quantum dots, leading to Coulomb blockade effects.
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Affiliation(s)
- F Molitor
- Solid State Physics Laboratory, ETH Zurich, Zurich, Switzerland
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30
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Güttinger J, Stampfer C, Frey T, Ihn T, Ensslin K. Transport through a strongly coupled graphene quantum dot in perpendicular magnetic field. NANOSCALE RESEARCH LETTERS 2011; 6:253. [PMID: 21711781 PMCID: PMC3211315 DOI: 10.1186/1556-276x-6-253] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/02/2010] [Accepted: 03/24/2011] [Indexed: 05/31/2023]
Abstract
We present transport measurements on a strongly coupled graphene quantum dot in a perpendicular magnetic field. The device consists of an etched single-layer graphene flake with two narrow constrictions separating a 140 nm diameter island from source and drain graphene contacts. Lateral graphene gates are used to electrostatically tune the device. Measurements of Coulomb resonances, including constriction resonances and Coulomb diamonds prove the functionality of the graphene quantum dot with a charging energy of approximately 4.5 meV. We show the evolution of Coulomb resonances as a function of perpendicular magnetic field, which provides indications of the formation of the graphene specific 0th Landau level. Finally, we demonstrate that the complex pattern superimposing the quantum dot energy spectra is due to the formation of additional localized states with increasing magnetic field.
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Affiliation(s)
| | - Christoph Stampfer
- Solid State Physics Laboratory, ETH Zurich, 8093 Zurich, Switzerland
- Current Address: JARA-FIT and II, Institute of Physics, RWTH Aachen, 52074 Aachen, Germany
| | - Tobias Frey
- Solid State Physics Laboratory, ETH Zurich, 8093 Zurich, Switzerland
| | - Thomas Ihn
- Solid State Physics Laboratory, ETH Zurich, 8093 Zurich, Switzerland
| | - Klaus Ensslin
- Solid State Physics Laboratory, ETH Zurich, 8093 Zurich, Switzerland
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31
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Roulleau P, Baer S, Choi T, Molitor F, Güttinger J, Müller T, Dröscher S, Ensslin K, Ihn T. Coherent electron–phonon coupling in tailored quantum systems. Nat Commun 2011; 2:239. [DOI: 10.1038/ncomms1241] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2010] [Accepted: 02/16/2011] [Indexed: 11/09/2022] Open
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32
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Wakabayashi K, Sasaki KI, Nakanishi T, Enoki T. Electronic states of graphene nanoribbons and analytical solutions. SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS 2010; 11:054504. [PMID: 27877361 PMCID: PMC5090620 DOI: 10.1088/1468-6996/11/5/054504] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2010] [Revised: 11/29/2010] [Accepted: 08/29/2010] [Indexed: 05/30/2023]
Abstract
Graphene is a one-atom-thick layer of graphite, where low-energy electronic states are described by the massless Dirac fermion. The orientation of the graphene edge determines the energy spectrum of π-electrons. For example, zigzag edges possess localized edge states with energies close to the Fermi level. In this review, we investigate nanoscale effects on the physical properties of graphene nanoribbons and clarify the role of edge boundaries. We also provide analytical solutions for electronic dispersion and the corresponding wavefunction in graphene nanoribbons with their detailed derivation using wave mechanics based on the tight-binding model. The energy band structures of armchair nanoribbons can be obtained by making the transverse wavenumber discrete, in accordance with the edge boundary condition, as in the case of carbon nanotubes. However, zigzag nanoribbons are not analogous to carbon nanotubes, because in zigzag nanoribbons the transverse wavenumber depends not only on the ribbon width but also on the longitudinal wavenumber. The quantization rule of electronic conductance as well as the magnetic instability of edge states due to the electron-electron interaction are briefly discussed.
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Affiliation(s)
- Katsunori Wakabayashi
- International Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), Namiki 1-1, Tsukuba 305-0044, Japan; PRESTO, Japan Science and Technology Agency (JST), Kawaguchi 332-0012, Japan
| | - Ken-Ichi Sasaki
- International Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), Namiki 1-1, Tsukuba 305-0044, Japan
| | - Takeshi Nakanishi
- Nanotube Research Center, AIST, Higashi 1-1-1, Tsukuba 305-8565, Japan
| | - Toshiaki Enoki
- Department of Chemistry, Tokyo Institute of Technology, Tokyo 152-8551, Japan
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33
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Güttinger J, Frey T, Stampfer C, Ihn T, Ensslin K. Spin states in graphene quantum dots. PHYSICAL REVIEW LETTERS 2010; 105:116801. [PMID: 20867593 DOI: 10.1103/physrevlett.105.116801] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2010] [Indexed: 05/29/2023]
Abstract
We investigate ground and excited state transport through small (d≈70 nm) graphene quantum dots. The successive spin filling of orbital states is detected by measuring the difference between ground-state energies as a function of a magnetic field. For a magnetic field in-plane of the quantum dot the Zeeman splitting of spin states is measured. The results are compatible with a g factor of 2, and we detect a spin-filling sequence for a series of states which is reasonable given the strength of exchange interaction effects expected by comparing Coulomb interaction energy and kinetic energy of charge carriers in graphene.
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Affiliation(s)
- J Güttinger
- Solid State Physics Laboratory, ETH Zurich, 8093 Zurich, Switzerland.
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34
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Neubeck S, Ponomarenko LA, Freitag F, Giesbers AJM, Zeitler U, Morozov SV, Blake P, Geim AK, Novoselov KS. From one electron to one hole: quasiparticle counting in graphene quantum dots determined by electrochemical and plasma etching. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2010; 6:1469-73. [PMID: 20593379 DOI: 10.1002/smll.201000291] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Affiliation(s)
- Soeren Neubeck
- School of Physics & Astronomy University of Manchester, UK
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