1
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Chakraborti H, Gorini C, Knothe A, Liu MH, Makk P, Parmentier FD, Perconte D, Richter K, Roulleau P, Sacépé B, Schönenberger C, Yang W. Electron wave and quantum optics in graphene. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2024; 36:393001. [PMID: 38697131 DOI: 10.1088/1361-648x/ad46bc] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2023] [Accepted: 05/01/2024] [Indexed: 05/04/2024]
Abstract
In the last decade, graphene has become an exciting platform for electron optical experiments, in some aspects superior to conventional two-dimensional electron gases (2DEGs). A major advantage, besides the ultra-large mobilities, is the fine control over the electrostatics, which gives the possibility of realising gap-less and compact p-n interfaces with high precision. The latter host non-trivial states,e.g., snake states in moderate magnetic fields, and serve as building blocks of complex electron interferometers. Thanks to the Dirac spectrum and its non-trivial Berry phase, the internal (valley and sublattice) degrees of freedom, and the possibility to tailor the band structure using proximity effects, such interferometers open up a completely new playground based on novel device architectures. In this review, we introduce the theoretical background of graphene electron optics, fabrication methods used to realise electron-optical devices, and techniques for corresponding numerical simulations. Based on this, we give a comprehensive review of ballistic transport experiments and simple building blocks of electron optical devices both in single and bilayer graphene, highlighting the novel physics that is brought in compared to conventional 2DEGs. After describing the different magnetic field regimes in graphene p-n junctions and nanostructures, we conclude by discussing the state of the art in graphene-based Mach-Zender and Fabry-Perot interferometers.
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Affiliation(s)
| | - Cosimo Gorini
- Université Paris-Saclay, CEA, CNRS, SPEC, 91191 Gif-sur-Yvette, France
| | - Angelika Knothe
- Institut für Theoretische Physik, Universität Regensburg, D-93040 Regensburg, Germany
| | - Ming-Hao Liu
- Department of Physics and Center for Quantum Frontiers of Research and Technology (QFort), National Cheng Kung University, Tainan 70101, Taiwan
| | - Péter Makk
- Department of Physics, Institute of Physics, Budapest University of Technology and Economics, Műegyetem rkp. 3., Budapest H-1111, Hungary
- MTA-BME Correlated van der Waals Structures Momentum Research Group, Műegyetem rkp. 3., Budapest H-1111, Hungary
| | | | - David Perconte
- Université Grenoble Alpes, CNRS, Grenoble INP, Institut Néel, 38000 Grenoble, France
| | - Klaus Richter
- Institut für Theoretische Physik, Universität Regensburg, D-93040 Regensburg, Germany
| | - Preden Roulleau
- Université Paris-Saclay, CEA, CNRS, SPEC, 91191 Gif-sur-Yvette, France
| | - Benjamin Sacépé
- Université Grenoble Alpes, CNRS, Grenoble INP, Institut Néel, 38000 Grenoble, France
| | | | - Wenmin Yang
- Université Grenoble Alpes, CNRS, Grenoble INP, Institut Néel, 38000 Grenoble, France
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2
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Liu A, Zhang X, Liu Z, Li Y, Peng X, Li X, Qin Y, Hu C, Qiu Y, Jiang H, Wang Y, Li Y, Tang J, Liu J, Guo H, Deng T, Peng S, Tian H, Ren TL. The Roadmap of 2D Materials and Devices Toward Chips. NANO-MICRO LETTERS 2024; 16:119. [PMID: 38363512 PMCID: PMC10873265 DOI: 10.1007/s40820-023-01273-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Accepted: 10/30/2023] [Indexed: 02/17/2024]
Abstract
Due to the constraints imposed by physical effects and performance degradation, silicon-based chip technology is facing certain limitations in sustaining the advancement of Moore's law. Two-dimensional (2D) materials have emerged as highly promising candidates for the post-Moore era, offering significant potential in domains such as integrated circuits and next-generation computing. Here, in this review, the progress of 2D semiconductors in process engineering and various electronic applications are summarized. A careful introduction of material synthesis, transistor engineering focused on device configuration, dielectric engineering, contact engineering, and material integration are given first. Then 2D transistors for certain electronic applications including digital and analog circuits, heterogeneous integration chips, and sensing circuits are discussed. Moreover, several promising applications (artificial intelligence chips and quantum chips) based on specific mechanism devices are introduced. Finally, the challenges for 2D materials encountered in achieving circuit-level or system-level applications are analyzed, and potential development pathways or roadmaps are further speculated and outlooked.
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Affiliation(s)
- Anhan Liu
- School of Integrated Circuits and Beijing National Research Center for Information Science and Technology (BNRist), Tsinghua University, Beijing, 100049, People's Republic of China
| | - Xiaowei Zhang
- School of Integrated Circuits and Beijing National Research Center for Information Science and Technology (BNRist), Tsinghua University, Beijing, 100049, People's Republic of China
| | - Ziyu Liu
- School of Microelectronics, Fudan University, Shanghai, 200433, People's Republic of China
| | - Yuning Li
- School of Electronic and Information Engineering, Beijing Jiaotong University, Beijing, 100044, People's Republic of China
| | - Xueyang Peng
- High-Frequency High-Voltage Device and Integrated Circuits R&D Center, Institute of Microelectronics, Chinese Academy of Sciences, Beijing, 100029, People's Republic of China
- School of Integrated Circuits, University of Chinese Academy of Sciences, Beijing, 100049, People's Republic of China
| | - Xin Li
- State Key Laboratory of Dynamic Measurement Technology, Shanxi Province Key Laboratory of Quantum Sensing and Precision Measurement, North University of China, Taiyuan, 030051, People's Republic of China
| | - Yue Qin
- State Key Laboratory of Dynamic Measurement Technology, Shanxi Province Key Laboratory of Quantum Sensing and Precision Measurement, North University of China, Taiyuan, 030051, People's Republic of China
| | - Chen Hu
- High-Frequency High-Voltage Device and Integrated Circuits R&D Center, Institute of Microelectronics, Chinese Academy of Sciences, Beijing, 100029, People's Republic of China
- School of Integrated Circuits, University of Chinese Academy of Sciences, Beijing, 100049, People's Republic of China
| | - Yanqing Qiu
- High-Frequency High-Voltage Device and Integrated Circuits R&D Center, Institute of Microelectronics, Chinese Academy of Sciences, Beijing, 100029, People's Republic of China
- School of Integrated Circuits, University of Chinese Academy of Sciences, Beijing, 100049, People's Republic of China
| | - Han Jiang
- School of Microelectronics, Fudan University, Shanghai, 200433, People's Republic of China
| | - Yang Wang
- School of Microelectronics, Fudan University, Shanghai, 200433, People's Republic of China
| | - Yifan Li
- School of Integrated Circuits and Beijing National Research Center for Information Science and Technology (BNRist), Tsinghua University, Beijing, 100049, People's Republic of China
| | - Jun Tang
- State Key Laboratory of Dynamic Measurement Technology, Shanxi Province Key Laboratory of Quantum Sensing and Precision Measurement, North University of China, Taiyuan, 030051, People's Republic of China
| | - Jun Liu
- State Key Laboratory of Dynamic Measurement Technology, Shanxi Province Key Laboratory of Quantum Sensing and Precision Measurement, North University of China, Taiyuan, 030051, People's Republic of China
| | - Hao Guo
- State Key Laboratory of Dynamic Measurement Technology, Shanxi Province Key Laboratory of Quantum Sensing and Precision Measurement, North University of China, Taiyuan, 030051, People's Republic of China.
| | - Tao Deng
- School of Electronic and Information Engineering, Beijing Jiaotong University, Beijing, 100044, People's Republic of China.
| | - Songang Peng
- High-Frequency High-Voltage Device and Integrated Circuits R&D Center, Institute of Microelectronics, Chinese Academy of Sciences, Beijing, 100029, People's Republic of China.
- IMECAS-HKUST-Joint Laboratory of Microelectronics, Beijing, 100029, People's Republic of China.
| | - He Tian
- School of Integrated Circuits and Beijing National Research Center for Information Science and Technology (BNRist), Tsinghua University, Beijing, 100049, People's Republic of China.
| | - Tian-Ling Ren
- School of Integrated Circuits and Beijing National Research Center for Information Science and Technology (BNRist), Tsinghua University, Beijing, 100049, People's Republic of China.
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3
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Ingla-Aynés J, Manesco ALR, Ghiasi TS, Volosheniuk S, Watanabe K, Taniguchi T, van der Zant HSJ. Specular Electron Focusing between Gate-Defined Quantum Point Contacts in Bilayer Graphene. NANO LETTERS 2023; 23:5453-5459. [PMID: 37289250 PMCID: PMC10311585 DOI: 10.1021/acs.nanolett.3c00499] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2023] [Revised: 06/02/2023] [Indexed: 06/09/2023]
Abstract
We report multiterminal measurements in a ballistic bilayer graphene (BLG) channel, where multiple spin- and valley-degenerate quantum point contacts (QPCs) are defined by electrostatic gating. By patterning QPCs of different shapes along different crystallographic directions, we study the effect of size quantization and trigonal warping on transverse electron focusing (TEF). Our TEF spectra show eight clear peaks with comparable amplitudes and weak signatures of quantum interference at the lowest temperature, indicating that reflections at the gate-defined edges are specular, and transport is phase coherent. The temperature dependence of the focusing signal shows that, despite the small gate-induced bandgaps in our sample (≲45 meV), several peaks are visible up to 100 K. The achievement of specular reflection, which is expected to preserve the pseudospin information of the electron jets, is promising for the realization of ballistic interconnects for new valleytronic devices.
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Affiliation(s)
- Josep Ingla-Aynés
- Kavli
Institute of Nanoscience, Delft University
of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands
| | - Antonio L. R. Manesco
- Kavli
Institute of Nanoscience, Delft University
of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands
| | - Talieh S. Ghiasi
- Kavli
Institute of Nanoscience, Delft University
of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands
| | - Serhii Volosheniuk
- Kavli
Institute of Nanoscience, Delft University
of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands
| | - Kenji Watanabe
- Research
Center for Functional Materials, National
Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- International
Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Herre S. J. van der Zant
- Kavli
Institute of Nanoscience, Delft University
of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands
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4
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Miranda LP, da Costa DR, Peeters FM, Costa Filho RN. Vacancy clustering effect on the electronic and transport properties of bilayer graphene nanoribbons. NANOTECHNOLOGY 2022; 34:055706. [PMID: 36322965 DOI: 10.1088/1361-6528/ac9f50] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2022] [Accepted: 11/01/2022] [Indexed: 06/16/2023]
Abstract
Experimental realizations of two-dimensional materials are hardly free of structural defects such as e.g. vacancies, which, in turn, modify drastically its pristine physical defect-free properties. In this work, we explore effects due to point defect clustering on the electronic and transport properties of bilayer graphene nanoribbons, for AA and AB stacking and zigzag and armchair boundaries, by means of the tight-binding approach and scattering matrix formalism. Evident vacancy concentration signatures exhibiting a maximum amplitude and an universality regardless of the system size, stacking and boundary types, in the density of states around the zero-energy level are observed. Our results are explained via the coalescence analysis of the strong sizeable vacancy clustering effect in the system and the breaking of the inversion symmetry at high vacancy densities, demonstrating a similar density of states for two equivalent degrees of concentration disorder, below and above the maximum value.
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Affiliation(s)
- L P Miranda
- Departamento de Física, Universidade Federal do Ceará, Campus do Pici, Fortaleza, Ceará, Brazil
| | - D R da Costa
- Departamento de Física, Universidade Federal do Ceará, Campus do Pici, Fortaleza, Ceará, Brazil
- Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education & Hunan Provincial Key Laboratory of Low-Dimensional Structural Physics and Devices, School of Physics and Electronics, Hunan University, Changsha 410082, People's Republic of China
| | - F M Peeters
- Department of Physics, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp, Belgium
| | - R N Costa Filho
- Departamento de Física, Universidade Federal do Ceará, Campus do Pici, Fortaleza, Ceará, Brazil
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5
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Iwakiri S, de Vries FK, Portolés E, Zheng G, Taniguchi T, Watanabe K, Ihn T, Ensslin K. Gate-Defined Electron Interferometer in Bilayer Graphene. NANO LETTERS 2022; 22:6292-6297. [PMID: 35880910 DOI: 10.1021/acs.nanolett.2c01874] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
We present an electron interferometer defined purely by electrostatic gating in an encapsulated bilayer graphene. This minimizes possible sample degradation introduced by conventional etching methods when preparing quantum devices. The device quality is demonstrated by observing Aharonov-Bohm (AB) oscillations with a period of h/e, h/2e, h/3e, and h/4e, witnessing a coherence length of many microns. The AB oscillations as well as the type of carriers (electrons or holes) are seamlessly tunable with gating. The coherence length longer than the ring perimeter and semiclassical trajectory of the carrier are established from the analysis of the temperature and magnetic field dependence of the oscillations. Our gate-defined ring geometry has the potential to evolve into a platform for exploring correlated quantum states such as superconductivity in interferometers in twisted bilayer graphene.
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Affiliation(s)
- Shuichi Iwakiri
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | | | - Elías Portolés
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Giulia Zheng
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, 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
| | - Thomas Ihn
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
- Quantum Center, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Klaus Ensslin
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
- Quantum Center, ETH Zurich, CH-8093 Zurich, Switzerland
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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: 6] [Impact Index Per Article: 3.0] [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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Biomolecular control over local gating in bilayer graphene induced by ferritin. iScience 2022; 25:104128. [PMID: 35434555 PMCID: PMC9010634 DOI: 10.1016/j.isci.2022.104128] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2021] [Revised: 01/11/2022] [Accepted: 03/17/2022] [Indexed: 11/30/2022] Open
Abstract
Electrical field-induced charge modulation in graphene-based devices at the nanoscale with ultrahigh density carrier accumulation is important for various practical applications. In bilayer graphene (BLG), inversion symmetry can simply be broken by an external electric field. However, control over charge carrier density at the nanometer scale is a challenging task. We demonstrate local gating of BLG in the nanometer range by adsorption of AfFtnAA (which is a bioengineered ferritin, an iron-storing globular protein with ∅ = 12 nm). Low-temperature electrical transport measurements with field-effect transistors with these AfFtnAA/BLG surfaces show hysteresis with two Dirac peaks. One peak at a gate voltage VBG = 35 V is associated with pristine BLG, while the second peak at VBG = 5 V results from local doping by ferritin. This charge trapping at the biomolecular length scale offers a straightforward and non-destructive method to alter the local electronic structure of BLG. Local gating with 12 nm resolution by charge trapping in ferritin. Adsorption of ferritin on graphene via non-invasive self-assembly. Charging controlled via iron oxide loading of ferritin. Visualization of individual ferritins on graphene by atomic force microscopy.
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8
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Cheng R, Xiang Y, Guo R, Li L, Zou G, Fu C, Hou H, Ji X. Structure and Interface Modification of Carbon Dots for Electrochemical Energy Application. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2021; 17:e2102091. [PMID: 34318998 DOI: 10.1002/smll.202102091] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2021] [Indexed: 05/15/2023]
Abstract
Carbon dots (CDs) as new nanomaterials have attracted much attention in recent years due to their unique characteristics. Notably, structure and interface modification (carbon core, edge, defects, and functional groups) of CDs have been considered as valid methods to regulate their properties, which contain electron transfer effect, electrochemical activity, fluorescence luminescent, and so on. Additionally, CDs with ultrasmall size, excellent dispersibility, high specific surface area, and abundant functional groups can guarantee positive and extraordinary effects in electrical energy storage and conversion. Therefore, CDs are used to couple with other materials by constructing a special interface structure to enhance their properties. Here, diverse structural and interfacial modifications of CDs with various heteroatoms and synergy effects are systematically analyzed. And not only several main syntheses of CDs-based composites (CDs/X) are summarized but also the merit and demerit of CDs/X in electrical energy storage are discussed. Finally, the applications of CDs/X in energy storage devices (supercapacitors, batteries) and electrocatalysts for practical applications are discussed. This review mainly provides a comprehensive summary and future prospect for synthesis, modification, and electrochemical applications of CDs.
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Affiliation(s)
- Ruiqi Cheng
- School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Yinger Xiang
- College of Chemistry and Chemical Engineering, Central South University, Changsha, 410083, China
| | - Ruiting Guo
- College of Chemistry and Chemical Engineering, Central South University, Changsha, 410083, China
| | - Lin Li
- College of Chemistry and Chemical Engineering, Central South University, Changsha, 410083, China
| | - Guoqiang Zou
- College of Chemistry and Chemical Engineering, Central South University, Changsha, 410083, China
| | - Chaopeng Fu
- School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Hongshuai Hou
- College of Chemistry and Chemical Engineering, Central South University, Changsha, 410083, China
| | - Xiaobo Ji
- College of Chemistry and Chemical Engineering, Central South University, Changsha, 410083, China
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9
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Joucken F, Bena C, Ge Z, Quezada-Lopez EA, Ducastelle F, Tanagushi T, Watanabe K, Velasco J. Sublattice Dependence and Gate Tunability of Midgap and Resonant States Induced by Native Dopants in Bernal-Stacked Bilayer Graphene. PHYSICAL REVIEW LETTERS 2021; 127:106401. [PMID: 34533366 DOI: 10.1103/physrevlett.127.106401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Accepted: 07/08/2021] [Indexed: 06/13/2023]
Abstract
The properties of semiconductors can be crucially impacted by midgap states induced by dopants, which can be native or intentionally incorporated in the crystal lattice. For Bernal-stacked bilayer graphene (BLG), which has a tunable band gap, the existence of midgap states induced by dopants or adatoms has been investigated theoretically and observed indirectly in electron transport experiments. Here, we characterize BLG midgap states in real space, with atomic-scale resolution with scanning tunneling microscopy and spectroscopy. We show that the midgap states in BLG-for which we demonstrate gate tunability-appear when the dopant is hosted on the nondimer sublattice sites. We further evidence the presence of narrow resonances at the onset of the high-energy bands (valence or conduction, depending on the dopant type) when the dopants lie on the dimer sublattice sites. Our results are supported by tight-binding calculations that agree remarkably well with the experimental findings.
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Affiliation(s)
- Frédéric Joucken
- Department of Physics, University of California, Santa Cruz, California 95064, USA
- Department of Physics, Box 871504, Arizona State University, Tempe, Arizona 85287, USA
| | - 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, USA
| | | | - François Ducastelle
- Laboratoire d'Etude des Microstructures, ONERA-CNRS, UMR104, Université Paris-Saclay, B.P. 72, 92322 Châtillon Cedex, France
| | - Takashi Tanagushi
- 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
| | - Jairo Velasco
- Department of Physics, University of California, Santa Cruz, California 95064, USA
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10
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Zare M, Haghdoust S. Magneto-optical properties of bilayer phosphorene quantum dots. Phys Chem Chem Phys 2021; 23:17645-17655. [PMID: 34370800 DOI: 10.1039/d1cp01377g] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Using the tight-binding approach, we investigate the electronic and magneto-optical properties of bilayer phosphorene quantum dots (BLPQDs) in the presence of perpendicular electric and magnetic fields. The magneto-energy spectra of the BLPQDs exhibit Aharonov-Bohm oscillations. The period and the amplitude of the oscillation decrease with the size of the BLPQDs. An oscillatory behavior of the local density of states (LDOS) versus the magnetic field is observed, as well as the appearance of the spatial Aharonov-Bohm oscillations in the LDOS. In the absence of the electric field, there exists an s-fold degeneracy (s absolutely flat bands at exactly zero energy) arising from the edge-mode states, where s is the smaller value between M and N, where M and N are the number of phosphorus atoms along the x and y axis, respectively, in a rectangular BLBPQD. The absorption spectra of the BLPQDs are obtained for both in-plane and out-of-plane polarizations. Compared with the absorption spectra of graphene dots, the absorption of an out-of-plane polarization of the incident light is high compared to that of in-plane polarizations. On the other hand, the absorption spectra due to in-plane polarizations are almost the same in the case of graphene, whereas they are considerably different in BLBPQDs. Importantly, the appearance of several sharp and high absorption peaks in the near-infrared (NIR) range dictates the BLBPQDs for application and development of bioimaging, biomedicine and drug delivery technology. More importantly, both the location and intensity of these NIR peaks depend characteristically on the orientation of the polarization of the incident light, which can be desirably tuned by the simultaneous engineering of magnetic and electric fields. Such unique advantage of the anisotropic optical feature enables a new degree of freedom for achieving novel polarization-dependent photonic devices. The dual magnetic and electric field tunable optical and electrical features of the BLPQDs are expected to have important consequences for the development of multifunctional magneto-optoelectronic devices and provide insight into the applicability of quantum photopic technologies based on BLBPQDs.
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Affiliation(s)
- Moslem Zare
- Department of Physics, Yasouj University, Yasouj, Iran 75914-353, Iran.
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11
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Flat band carrier confinement in magic-angle twisted bilayer graphene. Nat Commun 2021; 12:4180. [PMID: 34234146 PMCID: PMC8263728 DOI: 10.1038/s41467-021-24480-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2020] [Accepted: 06/14/2021] [Indexed: 11/08/2022] Open
Abstract
Magic-angle twisted bilayer graphene has emerged as a powerful platform for studying strongly correlated electron physics, owing to its almost dispersionless low-energy bands and the ability to tune the band filling by electrostatic gating. Techniques to control the twist angle between graphene layers have led to rapid experimental progress but improving sample quality is essential for separating the delicate correlated electron physics from disorder effects. Owing to the 2D nature of the system and the relatively low carrier density, the samples are highly susceptible to small doping inhomogeneity which can drastically modify the local potential landscape. This potential disorder is distinct from the twist angle variation which has been studied elsewhere. Here, by using low temperature scanning tunneling spectroscopy and planar tunneling junction measurements, we demonstrate that flat bands in twisted bilayer graphene can amplify small doping inhomogeneity that surprisingly leads to carrier confinement, which in graphene could previously only be realized in the presence of a strong magnetic field.
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12
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Kim BK, Choi DH, Yu BS, Kim M, Watanabe K, Taniguchi T, Kim JJ, Bae MH. Gate-tunable quantum dot formation between localized-resonant states in a few-layer MoS 2. NANOTECHNOLOGY 2021; 32:195207. [PMID: 33530078 DOI: 10.1088/1361-6528/abe262] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
We demonstrate a gate-tunable quantum dot (QD) located between two potential barriers defined in a few-layer MoS2. Although both local gates used to tune the potential barriers have disorder-induced QDs, we observe diagonal current stripes in current resonant islands formed by the alignment of the Fermi levels of the electrodes and the energy levels of the disorder-induced QDs, as evidence of the gate-tunable QD. We demonstrate that the charging energy of the designed QD can be tuned in the range of 2-6 meV by changing the local-gate voltages in ∼1 V.
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Affiliation(s)
- Bum-Kyu Kim
- Korea Research Institute of Standards and Science, Daejeon 34113, Republic of Korea
| | - Dong-Hwan Choi
- Korea Research Institute of Standards and Science, Daejeon 34113, Republic of Korea
- Department of Physics, Jeonbuk National University, Jeonju 54896, Republic of Korea
| | - Byung-Sung Yu
- Korea Research Institute of Standards and Science, Daejeon 34113, Republic of Korea
- Department of Physics, Jeonbuk National University, Jeonju 54896, Republic of Korea
| | - Minsoo Kim
- Department of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, United Kingdom
| | - 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
| | - Ju-Jin Kim
- Department of Physics, Jeonbuk National University, Jeonju 54896, Republic of Korea
| | - Myung-Ho Bae
- Korea Research Institute of Standards and Science, Daejeon 34113, Republic of Korea
- Department of Nano Science, University of Science and Technology, Daejeon, 34113, Republic of Korea
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13
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Ge Z, Joucken F, Quezada E, da Costa DR, Davenport J, Giraldo B, Taniguchi T, Watanabe K, Kobayashi NP, Low T, Velasco J. Visualization and Manipulation of Bilayer Graphene Quantum Dots with Broken Rotational Symmetry and Nontrivial Topology. NANO LETTERS 2020; 20:8682-8688. [PMID: 33226819 DOI: 10.1021/acs.nanolett.0c03453] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Electrostatically defined quantum dots (QDs) in Bernal stacked bilayer graphene (BLG) are a promising quantum information platform because of their long spin decoherence times, high sample quality, and tunability. Importantly, the shape of QD states determines the electron energy spectrum, the interactions between electrons, and the coupling of electrons to their environment, all of which are relevant for quantum information processing. Despite its importance, the shape of BLG QD states remains experimentally unexamined. Here we report direct visualization of BLG QD states by using a scanning tunneling microscope. Strikingly, we find these states exhibit a robust broken rotational symmetry. By using a numerical tight-binding model, we determine that the observed broken rotational symmetry can be attributed to low energy anisotropic bands. We then compare confined holes and electrons and demonstrate the influence of BLG's nontrivial band topology. Our study distinguishes BLG QDs from prior QD platforms with trivial band topology.
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Affiliation(s)
- Zhehao Ge
- Department of Physics, University of California, Santa Cruz, California 95064, United States
| | - Frederic Joucken
- Department of Physics, University of California, Santa Cruz, California 95064, United States
| | - Eberth Quezada
- Department of Physics, University of California, Santa Cruz, California 95064, United States
| | - Diego R da Costa
- Departamento de Física, Universidade Federal do Ceará, Caixa Postal 6030, Campus do Pici, 60455-900 Fortaleza, Ceará, Brazil
| | - John Davenport
- Department of Physics, University of California, Santa Cruz, California 95064, United States
| | - Brian Giraldo
- Jack Baskin School of Engineering, University of California, Santa Cruz, California 95064, United States
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectronics, 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
| | - Nobuhiko P Kobayashi
- Jack Baskin School of Engineering, University of California, Santa Cruz, California 95064, United States
| | - Tony Low
- Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Jairo Velasco
- Department of Physics, University of California, Santa Cruz, California 95064, United States
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14
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Mills SM, Averin DV, Du X. Localizing Fractional Quasiparticles on Graphene Quantum Hall Antidots. PHYSICAL REVIEW LETTERS 2020; 125:227701. [PMID: 33315430 DOI: 10.1103/physrevlett.125.227701] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2020] [Accepted: 10/26/2020] [Indexed: 06/12/2023]
Abstract
We report localization of fractional quantum Hall (QH) quasiparticles on graphene antidots. By studying coherent tunneling through the localized QH edge modes on the antidot, we measured the QH quasiparticle charges to be approximately ±e/3 at fractional fillings of ν=±1/3. The Dirac spectrum in graphene allows large energy scales and robust quasiparticle localization against thermal excitation. The capability of localizing fractional quasiparticles on QH antidots brings promising opportunities for realizing anyon braiding and novel quantum electronics.
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Affiliation(s)
- S M Mills
- Department of Physics, Stony Brook University, Stony Brook, New York 11794, USA
| | - D V Averin
- Department of Physics, Stony Brook University, Stony Brook, New York 11794, USA
| | - X Du
- Department of Physics, Stony Brook University, Stony Brook, New York 11794, USA
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15
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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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16
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Rickhaus P, Zheng G, Lado JL, Lee Y, Kurzmann A, Eich M, Pisoni R, Tong C, Garreis R, Gold C, Masseroni M, Taniguchi T, Wantanabe K, Ihn T, Ensslin K. Gap Opening in Twisted Double Bilayer Graphene by Crystal Fields. NANO LETTERS 2019; 19:8821-8828. [PMID: 31670969 DOI: 10.1021/acs.nanolett.9b03660] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Crystal fields occur due to a potential difference between chemically different atomic species. In van der Waals heterostructures such fields are naturally present perpendicular to the planes. It has been realized recently that twisted graphene multilayers provide powerful playgrounds to engineer electronic properties by the number of layers, the twist angle, applied electric biases, electronic interactions, and elastic relaxations, but crystal fields have not received the attention they deserve. Here, we show that the band structure of large-angle twisted double bilayer graphene is strongly modified by crystal fields. In particular, we experimentally demonstrate that twisted double bilayer graphene, encapsulated between hBN layers, exhibits an intrinsic band gap. By the application of an external field, the gaps in the individual bilayers can be closed, allowing to determine the crystal fields. We find that crystal fields point from the outer to the inner layers with strengths in the bottom/top bilayer [Formula: see text] = 0.13 V/nm ≈ [Formula: see text] = 0.12 V/nm. We show both by means of first-principles calculations and low energy models that crystal fields open a band gap in the ground state. Our results put forward a physical scenario in which a crystal field effect in carbon substantially impacts the low energy properties of twisted double bilayer graphene, suggesting that such contributions must be taken into account in other regimes to faithfully predict the electronic properties of twisted graphene multilayers.
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Affiliation(s)
- Peter Rickhaus
- Solid State Physics Laboratory , ETH Zürich , CH-8093 Zürich , Switzerland
| | - Giulia Zheng
- Solid State Physics Laboratory , ETH Zürich , CH-8093 Zürich , Switzerland
| | - Jose L Lado
- Department of Applied Physics , Aalto University , Espoo , Finland
- Institute for Theoretical Physics , ETH Zurich , 8093 Zurich , Switzerland
| | - Yongjin Lee
- Solid State Physics Laboratory , ETH Zürich , CH-8093 Zürich , Switzerland
| | - Annika Kurzmann
- Solid State Physics Laboratory , ETH Zürich , CH-8093 Zürich , Switzerland
| | - Marius Eich
- Solid State Physics Laboratory , ETH Zürich , CH-8093 Zürich , Switzerland
| | - Riccardo Pisoni
- Solid State Physics Laboratory , ETH Zürich , CH-8093 Zürich , Switzerland
| | - Chuyao Tong
- Solid State Physics Laboratory , ETH Zürich , CH-8093 Zürich , Switzerland
| | - Rebekka Garreis
- Solid State Physics Laboratory , ETH Zürich , CH-8093 Zürich , Switzerland
| | - Carolin Gold
- Solid State Physics Laboratory , ETH Zürich , CH-8093 Zürich , Switzerland
| | - Michele Masseroni
- Solid State Physics Laboratory , ETH Zürich , CH-8093 Zürich , Switzerland
| | - Takashi Taniguchi
- National Institute for Material Science , 1-1 Namiki , Tsukuba 305-0044 , Japan
| | - Kenji Wantanabe
- National Institute for Material Science , 1-1 Namiki , Tsukuba 305-0044 , Japan
| | - Thomas Ihn
- Solid State Physics Laboratory , ETH Zürich , CH-8093 Zürich , Switzerland
| | - Klaus Ensslin
- Solid State Physics Laboratory , ETH Zürich , CH-8093 Zürich , Switzerland
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17
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Kurzmann A, Eich M, Overweg H, Mangold M, Herman F, Rickhaus P, Pisoni R, Lee Y, Garreis R, Tong C, Watanabe K, Taniguchi T, Ensslin K, Ihn T. Excited States in Bilayer Graphene Quantum Dots. PHYSICAL REVIEW LETTERS 2019; 123:026803. [PMID: 31386494 DOI: 10.1103/physrevlett.123.026803] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Indexed: 05/21/2023]
Abstract
We report ground- and excited-state transport through an electrostatically defined few-hole quantum dot in bilayer graphene in both parallel and perpendicular applied magnetic fields. A remarkably clear level scheme for the two-particle spectra is found by analyzing finite bias spectroscopy data within a two-particle model including spin and valley degrees of freedom. We identify the two-hole ground state to be a spin-triplet and valley-singlet state. This spin alignment can be seen as Hund's rule for a valley-degenerate system, which is fundamentally different from quantum dots in carbon nanotubes, where the two-particle ground state is a spin-singlet state. The spin-singlet excited states are found to be valley-triplet states by tilting the magnetic field with respect to the sample plane. We quantify the exchange energy to be 0.35 meV and measure a valley and spin g factor of 36 and 2, respectively.
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Affiliation(s)
- A Kurzmann
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - M Eich
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - H Overweg
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - M Mangold
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - F Herman
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - P Rickhaus
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - R Pisoni
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Y Lee
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - R Garreis
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - C Tong
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - K Watanabe
- National Institute for Material Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - T Taniguchi
- National Institute for Material Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - K Ensslin
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - T Ihn
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
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18
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Overweg H, Knothe A, Fabian T, Linhart L, Rickhaus P, Wernli L, Watanabe K, Taniguchi T, Sánchez D, Burgdörfer J, Libisch F, Fal'ko VI, Ensslin K, Ihn T. Topologically Nontrivial Valley States in Bilayer Graphene Quantum Point Contacts. PHYSICAL REVIEW LETTERS 2018; 121:257702. [PMID: 30608777 DOI: 10.1103/physrevlett.121.257702] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/06/2018] [Indexed: 06/09/2023]
Abstract
We present measurements of quantized conductance in electrostatically induced quantum point contacts in bilayer graphene. The application of a perpendicular magnetic field leads to an intricate pattern of lifted and restored degeneracies with increasing field: at zero magnetic field the degeneracy of quantized one-dimensional subbands is four, because of a twofold spin and a twofold valley degeneracy. By switching on the magnetic field, the valley degeneracy is lifted. Because of the Berry curvature, states from different valleys split linearly in magnetic field. In the quantum Hall regime fourfold degenerate conductance plateaus reemerge. During the adiabatic transition to the quantum Hall regime, levels from one valley shift by two in quantum number with respect to the other valley, forming an interweaving pattern that can be reproduced by numerical calculations.
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Affiliation(s)
- Hiske Overweg
- Solid State Physics Laboratory, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Angelika Knothe
- National Graphene Institute, University of Manchester, Manchester M13 9PL, United Kingdom
| | - Thomas Fabian
- Institute for Theoretical Physics, Vienna University of Technology, A-1040 Vienna, Austria
| | - Lukas Linhart
- Institute for Theoretical Physics, Vienna University of Technology, A-1040 Vienna, Austria
| | - Peter Rickhaus
- Solid State Physics Laboratory, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Lucien Wernli
- Solid State Physics Laboratory, ETH Zürich, CH-8093 Zürich, 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
| | - David Sánchez
- Institute for Cross-Disciplinary Physics and Complex Systems IFISC (UIB-CSIC), 07122 Palma de Mallorca, Spain
| | - Joachim Burgdörfer
- Institute for Theoretical Physics, Vienna University of Technology, A-1040 Vienna, Austria
| | - Florian Libisch
- Institute for Theoretical Physics, Vienna University of Technology, A-1040 Vienna, Austria
| | - 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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19
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Kraft R, Krainov IV, Gall V, Dmitriev AP, Krupke R, Gornyi IV, Danneau R. Valley Subband Splitting in Bilayer Graphene Quantum Point Contacts. PHYSICAL REVIEW LETTERS 2018; 121:257703. [PMID: 30608811 DOI: 10.1103/physrevlett.121.257703] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2018] [Indexed: 06/09/2023]
Abstract
We report a study of one-dimensional subband splitting in a bilayer graphene quantum point contact in which quantized conductance in steps of 4e^{2}/h is clearly defined down to the lowest subband. While our source-drain bias spectroscopy measurements reveal an unconventional confinement, we observe a full lifting of the valley degeneracy at high magnetic fields perpendicular to the bilayer graphene plane for the first two lowest subbands where confinement and Coulomb interactions are the strongest and a peculiar merging or mixing of K and K^{'} valleys from two nonadjacent subbands with indices (N,N+2), which are well described by our semiphenomenological model.
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Affiliation(s)
- R Kraft
- Institute of Nanotechnology, Karlsruhe Institute of Technology, D-76021 Karlsruhe, Germany
| | - I V Krainov
- A.F. Ioffe Physico-Technical Institute, 194021 St. Petersburg, Russia
- Lappeenranta University of Technology, P.O. Box 20, 53851 Lappeenranta, Finland
| | - V Gall
- Institute of Nanotechnology, Karlsruhe Institute of Technology, D-76021 Karlsruhe, Germany
- Institute for Condensed Matter Theory, Karlsruhe Institute of Technology, D-76128 Karlsruhe, Germany
| | - A P Dmitriev
- A.F. Ioffe Physico-Technical Institute, 194021 St. Petersburg, Russia
| | - R Krupke
- Institute of Nanotechnology, Karlsruhe Institute of Technology, D-76021 Karlsruhe, Germany
- Department of Materials and Earth Sciences, Technical University Darmstadt, 64287 Darmstadt, Germany
| | - I V Gornyi
- Institute of Nanotechnology, Karlsruhe Institute of Technology, D-76021 Karlsruhe, Germany
- A.F. Ioffe Physico-Technical Institute, 194021 St. Petersburg, Russia
- Institute for Condensed Matter Theory, Karlsruhe Institute of Technology, D-76128 Karlsruhe, Germany
| | - R Danneau
- Institute of Nanotechnology, Karlsruhe Institute of Technology, D-76021 Karlsruhe, Germany
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20
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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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21
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Velasco J, Lee J, Wong D, Kahn S, Tsai HZ, Costello J, Umeda T, Taniguchi T, Watanabe K, Zettl A, Wang F, Crommie MF. Visualization and Control of Single-Electron Charging in Bilayer Graphene Quantum Dots. NANO LETTERS 2018; 18:5104-5110. [PMID: 30035544 DOI: 10.1021/acs.nanolett.8b01972] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Graphene p-n junctions provide an ideal platform for investigating novel behavior at the boundary between electronics and optics that arise from massless Dirac Fermions, such as whispering gallery modes and Veselago lensing. Bilayer graphene also hosts Dirac Fermions, but they differ from single-layer graphene charge carriers because they are massive, can be gapped by an applied perpendicular electric field, and have very different pseudospin selection rules across a p-n junction. Novel phenomena predicted for these massive Dirac Fermions at p-n junctions include anti-Klein tunneling, oscillatory Zener tunneling, and electron cloaked states. Despite these predictions there has been little experimental focus on the microscopic spatial behavior of massive Dirac Fermions in the presence of p-n junctions. Here we report the experimental manipulation and characterization of massive Dirac Fermions within bilayer graphene quantum dots defined by circular p-n junctions through the use of scanning tunneling microscopy-based (STM) methods. Our p-n junctions are created via a flexible technique that enables realization of exposed quantum dots in bilayer graphene/hBN heterostructures. These quantum dots exhibit sharp spectroscopic resonances that disperse in energy as a function of applied gate voltage. Spatial maps of these features show prominent concentric rings with diameters that can be tuned by an electrostatic gate. This behavior is explained by single-electron charging of localized states that arise from the quantum confinement of massive Dirac Fermions within our exposed bilayer graphene quantum dots.
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Affiliation(s)
- Jairo Velasco
- Department of Physics , University of California , Berkeley , California 94720 , United States
- Department of Physics , University of California , Santa Cruz , California 95064 , United States
| | - Juwon Lee
- Department of Physics , University of California , Berkeley , California 94720 , United States
| | - Dillon Wong
- Department of Physics , University of California , Berkeley , California 94720 , United States
| | - Salman Kahn
- Department of Physics , University of California , Berkeley , California 94720 , United States
| | - Hsin-Zon Tsai
- Department of Physics , University of California , Berkeley , California 94720 , United States
| | - Joseph Costello
- Department of Physics , University of California , Berkeley , California 94720 , United States
| | - Torben Umeda
- Department of Physics , University of California , Berkeley , California 94720 , United States
| | - Takashi Taniguchi
- National Institute for Materials Science , 1-1 Namiki , Tsukuba , 305-0044 , Japan
| | - Kenji Watanabe
- National Institute for Materials Science , 1-1 Namiki , Tsukuba , 305-0044 , Japan
| | - Alex Zettl
- Department of Physics , University of California , Berkeley , California 94720 , United States
- Materials Sciences Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
- Kavli Energy NanoSciences Institute at the University of California , Berkeley and the Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
| | - Feng Wang
- Department of Physics , University of California , Berkeley , California 94720 , United States
- Materials Sciences Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
- Kavli Energy NanoSciences Institute at the University of California , Berkeley and the Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
| | - Michael F Crommie
- Department of Physics , University of California , Berkeley , California 94720 , United States
- Materials Sciences Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
- Kavli Energy NanoSciences Institute at the University of California , Berkeley and the Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
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22
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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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23
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Eich M, Pisoni R, Pally A, Overweg H, Kurzmann A, Lee Y, Rickhaus P, Watanabe K, Taniguchi T, Ensslin K, Ihn T. Coupled Quantum Dots in Bilayer Graphene. NANO LETTERS 2018; 18:5042-5048. [PMID: 29985000 DOI: 10.1021/acs.nanolett.8b01859] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Electrostatic confinement of charge carriers in bilayer graphene provides a unique platform for carbon-based spin, charge, or exchange qubits. By exploiting the possibility to induce a band gap with electrostatic gating, we form a versatile and widely tunable multiquantum dot system. We demonstrate the formation of single, double and triple quantum dots that are free of any sign of disorder. In bilayer graphene, we have the possibility to form tunnel barriers using different mechanisms. We can exploit the ambipolar nature of bilayer graphene where pn-junctions form natural tunnel barriers. Alternatively, we can use gates to form tunnel barriers, where we can vary the tunnel coupling by more than 2 orders of magnitude tuning between a deeply Coulomb blockaded system and a Fabry-Pérot-like cavity. Demonstrating such tunability is an important step toward graphene-based quantum computation.
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Affiliation(s)
- Marius Eich
- Solid State Physics Laboratory , ETH Zurich , 8093 Zurich , Switzerland
| | - Riccardo Pisoni
- Solid State Physics Laboratory , ETH Zurich , 8093 Zurich , Switzerland
| | - Alessia Pally
- Solid State Physics Laboratory , ETH Zurich , 8093 Zurich , Switzerland
| | - Hiske Overweg
- Solid State Physics Laboratory , ETH Zurich , 8093 Zurich , Switzerland
| | - Annika Kurzmann
- Solid State Physics Laboratory , ETH Zurich , 8093 Zurich , Switzerland
| | - Yongjin Lee
- Solid State Physics Laboratory , ETH Zurich , 8093 Zurich , Switzerland
| | - Peter Rickhaus
- Solid State Physics Laboratory , ETH Zurich , 8093 Zurich , Switzerland
| | - Kenji Watanabe
- Advanced Materials Laboratory , NIMS , 1-1 Namiki , Tsukuba 305-0044 , Japan
| | - Takashi Taniguchi
- Advanced Materials Laboratory , NIMS , 1-1 Namiki , Tsukuba 305-0044 , Japan
| | - Klaus Ensslin
- Solid State Physics Laboratory , ETH Zurich , 8093 Zurich , Switzerland
| | - Thomas Ihn
- Solid State Physics Laboratory , ETH Zurich , 8093 Zurich , Switzerland
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24
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Hamer M, Tóvári E, Zhu M, Thompson MD, Mayorov A, Prance J, Lee Y, Haley RP, Kudrynskyi ZR, Patanè A, Terry D, Kovalyuk ZD, Ensslin K, Kretinin AV, Geim A, Gorbachev R. Gate-Defined Quantum Confinement in InSe-Based van der Waals Heterostructures. NANO LETTERS 2018; 18:3950-3955. [PMID: 29763556 DOI: 10.1021/acs.nanolett.8b01376] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Indium selenide, a post-transition metal chalcogenide, is a novel two-dimensional (2D) semiconductor with interesting electronic properties. Its tunable band gap and high electron mobility have already attracted considerable research interest. Here we demonstrate strong quantum confinement and manipulation of single electrons in devices made from few-layer crystals of InSe using electrostatic gating. We report on gate-controlled quantum dots in the Coulomb blockade regime as well as one-dimensional quantization in point contacts, revealing multiple plateaus. The work represents an important milestone in the development of quality devices based on 2D materials and makes InSe a prime candidate for relevant electronic and optoelectronic applications.
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Affiliation(s)
- Matthew Hamer
- School of Physics , University of Manchester , Oxford Road , Manchester , M13 9PL , U.K
- National Graphene Institute , University of Manchester , Oxford Road , Manchester , M13 9PL , U.K
| | - Endre Tóvári
- National Graphene Institute , University of Manchester , Oxford Road , Manchester , M13 9PL , U.K
| | - Mengjian Zhu
- School of Physics , University of Manchester , Oxford Road , Manchester , M13 9PL , U.K
| | - Michael D Thompson
- Department of Physics , University of Lancaster , Bailrigg , Lancaster , LA1 4YW , U.K
| | - Alexander Mayorov
- Centre for Advanced 2D Materials , National University of Singapore , 6 Science Drive 2 , Singapore 117546 , Singapore
| | - Jonathon Prance
- Department of Physics , University of Lancaster , Bailrigg , Lancaster , LA1 4YW , U.K
| | - Yongjin Lee
- Solid State Physics Laboratory , ETH Zurich , Otto-Stern-Weg 1 , 8093 Zürich , Switzerland
| | - Richard P Haley
- Department of Physics , University of Lancaster , Bailrigg , Lancaster , LA1 4YW , U.K
| | - Zakhar R Kudrynskyi
- School of Physics and Astronomy , University of Nottingham , Nottingham NG7 2RD , U.K
| | - Amalia Patanè
- School of Physics and Astronomy , University of Nottingham , Nottingham NG7 2RD , U.K
| | - Daniel Terry
- School of Physics , University of Manchester , Oxford Road , Manchester , M13 9PL , U.K
- National Graphene Institute , University of Manchester , Oxford Road , Manchester , M13 9PL , U.K
| | - Zakhar D Kovalyuk
- National Academy of Sciences of Ukraine , Institute for Problems of Materials Science , UA-58001 , Chernovtsy , Ukraine
| | - Klaus Ensslin
- Solid State Physics Laboratory , ETH Zurich , Otto-Stern-Weg 1 , 8093 Zürich , Switzerland
| | - Andrey V Kretinin
- National Graphene Institute , University of Manchester , Oxford Road , Manchester , M13 9PL , U.K
- School of Materials , University of Manchester , Oxford Road , Manchester M13 9PL , U.K
| | - Andre Geim
- School of Physics , University of Manchester , Oxford Road , Manchester , M13 9PL , U.K
| | - Roman Gorbachev
- School of Physics , University of Manchester , Oxford Road , Manchester , M13 9PL , U.K
- National Graphene Institute , University of Manchester , Oxford Road , Manchester , M13 9PL , U.K
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25
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Epping A, Banszerus L, Güttinger J, Krückeberg L, Watanabe K, Taniguchi T, Hassler F, Beschoten B, Stampfer C. Quantum transport through MoS 2 constrictions defined by photodoping. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:205001. [PMID: 29620021 DOI: 10.1088/1361-648x/aabbb8] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We present a device scheme to explore mesoscopic transport through molybdenum disulfide (MoS2) constrictions using photodoping. The devices are based on van-der-Waals heterostructures where few-layer MoS2 flakes are partially encapsulated by hexagonal boron nitride (hBN) and covered by a few-layer graphene flake to fabricate electrical contacts. Since the as-fabricated devices are insulating at low temperatures, we use photo-induced remote doping in the hBN substrate to create free charge carriers in the MoS2 layer. On top of the device, we place additional metal structures, which define the shape of the constriction and act as shadow masks during photodoping of the underlying MoS2/hBN heterostructure. Low temperature two- and four-terminal transport measurements show evidence of quantum confinement effects.
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Affiliation(s)
- Alexander Epping
- 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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26
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Freitag NM, Reisch T, Chizhova LA, Nemes-Incze P, Holl C, Woods CR, Gorbachev RV, Cao Y, Geim AK, Novoselov KS, Burgdörfer J, Libisch F, Morgenstern M. Large tunable valley splitting in edge-free graphene quantum dots on boron nitride. NATURE NANOTECHNOLOGY 2018; 13:392-397. [PMID: 29556008 DOI: 10.1038/s41565-018-0080-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2017] [Accepted: 01/25/2018] [Indexed: 06/08/2023]
Abstract
Coherent manipulation of the binary degrees of freedom is at the heart of modern quantum technologies. Graphene offers two binary degrees: the electron spin and the valley. Efficient spin control has been demonstrated in many solid-state systems, whereas exploitation of the valley has only recently been started, albeit without control at the single-electron level. Here, we show that van der Waals stacking of graphene onto hexagonal boron nitride offers a natural platform for valley control. We use a graphene quantum dot induced by the tip of a scanning tunnelling microscope and demonstrate valley splitting that is tunable from -5 to +10 meV (including valley inversion) by sub-10-nm displacements of the quantum dot position. This boosts the range of controlled valley splitting by about one order of magnitude. The tunable inversion of spin and valley states should enable coherent superposition of these degrees of freedom as a first step towards graphene-based qubits.
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Affiliation(s)
- Nils M Freitag
- II. Institute of Physics B, JARA-FIT, RWTH Aachen University, Aachen, Germany
| | - Tobias Reisch
- Institute for Theoretical Physics, TU Wien, Vienna, Austria
| | | | - Péter Nemes-Incze
- II. Institute of Physics B, JARA-FIT, RWTH Aachen University, Aachen, Germany
- Centre for Energy Research, Institute of Technical Physics and Materials Science, Budapest, Hungary
| | - Christian Holl
- II. Institute of Physics B, JARA-FIT, RWTH Aachen University, Aachen, Germany
| | - Colin R Woods
- School of Physics & Astronomy, University of Manchester, Manchester, UK
| | - Roman V Gorbachev
- School of Physics & Astronomy, University of Manchester, Manchester, UK
| | - Yang Cao
- School of Physics & Astronomy, University of Manchester, Manchester, UK
| | - Andre K Geim
- School of Physics & Astronomy, University of Manchester, Manchester, UK
| | | | | | | | - Markus Morgenstern
- II. Institute of Physics B, JARA-FIT, RWTH Aachen University, Aachen, Germany.
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27
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Caridad JM, Power SR, Lotz MR, Shylau AA, Thomsen JD, Gammelgaard L, Booth TJ, Jauho AP, Bøggild P. Conductance quantization suppression in the quantum Hall regime. Nat Commun 2018; 9:659. [PMID: 29440635 PMCID: PMC5811439 DOI: 10.1038/s41467-018-03064-8] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2017] [Accepted: 01/17/2018] [Indexed: 11/14/2022] Open
Abstract
Conductance quantization is the quintessential feature of electronic transport in non-interacting mesoscopic systems. This phenomenon is observed in quasi one-dimensional conductors at zero magnetic field B, and the formation of edge states at finite magnetic fields results in wider conductance plateaus within the quantum Hall regime. Electrostatic interactions can change this picture qualitatively. At finite B, screening mechanisms in narrow, gated ballistic conductors are predicted to give rise to an increase in conductance and a suppression of quantization due to the appearance of additional conduction channels. Despite being a universal effect, this regime has proven experimentally elusive because of difficulties in realizing one-dimensional systems with sufficiently hard-walled, disorder-free confinement. Here, we experimentally demonstrate the suppression of conductance quantization within the quantum Hall regime for graphene nanoconstrictions with low edge roughness. Our findings may have profound impact on fundamental studies of quantum transport in finite-size, two-dimensional crystals with low disorder. Conductance quantization is the hallmark of non-interacting confined systems. The authors show that the quantization in graphene nanoconstrictions with low edge disorder is suppressed in the quantum Hall regime. This is explained by the addition of new conductance channels due to electrostatic screening.
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Affiliation(s)
- José M Caridad
- Center for Nanostructured Graphene (CNG), Department of Micro- and Nanotechnology, Technical University of Denmark, 2800, Kongens Lyngby, Denmark.
| | - Stephen R Power
- Center for Nanostructured Graphene (CNG), Department of Micro- and Nanotechnology, Technical University of Denmark, 2800, Kongens Lyngby, Denmark.,Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and The Barcelona Institute of Science and Technology, Campus UAB, Bellaterra, Barcelona, 08193, Spain.,Universitat Autònoma de Barcelona, Bellaterra (Cerdanyola del Vallès), 08193, Spain
| | - Mikkel R Lotz
- Center for Nanostructured Graphene (CNG), Department of Micro- and Nanotechnology, Technical University of Denmark, 2800, Kongens Lyngby, Denmark
| | - Artsem A Shylau
- Center for Nanostructured Graphene (CNG), Department of Micro- and Nanotechnology, Technical University of Denmark, 2800, Kongens Lyngby, Denmark
| | - Joachim D Thomsen
- Center for Nanostructured Graphene (CNG), Department of Micro- and Nanotechnology, Technical University of Denmark, 2800, Kongens Lyngby, Denmark
| | - Lene Gammelgaard
- Center for Nanostructured Graphene (CNG), Department of Micro- and Nanotechnology, Technical University of Denmark, 2800, Kongens Lyngby, Denmark
| | - Timothy J Booth
- Center for Nanostructured Graphene (CNG), Department of Micro- and Nanotechnology, Technical University of Denmark, 2800, Kongens Lyngby, Denmark
| | - Antti-Pekka Jauho
- Center for Nanostructured Graphene (CNG), Department of Micro- and Nanotechnology, Technical University of Denmark, 2800, Kongens Lyngby, Denmark
| | - Peter Bøggild
- Center for Nanostructured Graphene (CNG), Department of Micro- and Nanotechnology, Technical University of Denmark, 2800, Kongens Lyngby, Denmark.
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28
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Trudeau C, Dion-Bertrand LI, Mukherjee S, Martel R, Cloutier SG. Electrostatic Deposition of Large-Surface Graphene. MATERIALS (BASEL, SWITZERLAND) 2018; 11:E116. [PMID: 29329220 PMCID: PMC5793614 DOI: 10.3390/ma11010116] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/29/2017] [Revised: 12/19/2017] [Accepted: 01/11/2018] [Indexed: 11/24/2022]
Abstract
This work describes a method for electrostatic deposition of graphene over a large area using controlled electrostatic exfoliation from a Highly Ordered Pyrolytic Graphite (HOPG) block. Deposition over 130 × 130 µm² with 96% coverage is achieved, which contrasts with sporadic micro-scale depositions of graphene with little control from previous works on electrostatic deposition. The deposition results are studied by Raman micro-spectroscopy and hyperspectral analysis using large fields of view to allow for the characterization of the whole deposition area. Results confirm that laser pre-patterning of the HOPG block prior to cleaving generates anchor points favoring a more homogeneous and defect-free HOPG surface, yielding larger and more uniform graphene depositions. We also demonstrate that a second patterning of the HOPG block just before exfoliation can yield features with precisely controlled geometries.
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Affiliation(s)
- Charles Trudeau
- Department of Electrical Engineering, École de Technologie Supérieure, 1100 Notre-Dame Ouest, Montréal, QC H3C 1K3, Canada.
| | | | - Sankha Mukherjee
- Department of Mechanical Engineering, McGill University, 845 Sherbrook Ouest, Montréal QC H3A 0G4, Canada.
| | - Richard Martel
- Department of Chemistry, Université de Montreal, 2900 Édouard-Montpetit, Montréal QC H3C 3J7, Canada.
| | - Sylvain G Cloutier
- Department of Electrical Engineering, École de Technologie Supérieure, 1100 Notre-Dame Ouest, Montréal, QC H3C 1K3, Canada.
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29
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Overweg H, Eggimann H, Chen X, Slizovskiy S, Eich M, Pisoni R, Lee Y, Rickhaus P, Watanabe K, Taniguchi T, Fal'ko V, Ihn T, Ensslin K. Electrostatically Induced Quantum Point Contacts in Bilayer Graphene. NANO LETTERS 2018; 18:553-559. [PMID: 29286668 DOI: 10.1021/acs.nanolett.7b04666] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We report the fabrication of electrostatically defined nanostructures in encapsulated bilayer graphene, with leakage resistances below depletion gates as high as R ∼ 10 GΩ. This exceeds previously reported values of R = 10-100 kΩ.1-3 We attribute this improvement to the use of a graphite back gate. We realize two split gate devices which define an electronic channel on the scale of the Fermi-wavelength. A channel gate covering the gap between the split gates varies the charge carrier density in the channel. We observe device-dependent conductance quantization of ΔG = 2e2/h and ΔG = 4e2/h. In quantizing magnetic fields normal to the sample plane, we recover the four-fold Landau level degeneracy of bilayer graphene. Unexpected mode crossings appear at the crossover between zero magnetic field and the quantum Hall regime.
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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
| | - Xi Chen
- National Graphene Institute, University of Manchester , Manchester M13 9PL, United Kingdom
| | - Sergey Slizovskiy
- National Graphene Institute, University of Manchester , Manchester M13 9PL, United Kingdom
| | - Marius Eich
- Solid State Physics Laboratory, ETH Zürich , CH-8093 Zürich, Switzerland
| | - Riccardo Pisoni
- Solid State Physics Laboratory, ETH Zürich , CH-8093 Zürich, Switzerland
| | - Yongjin Lee
- Solid State Physics Laboratory, ETH Zürich , CH-8093 Zürich, Switzerland
| | - Peter Rickhaus
- Solid State Physics Laboratory, ETH Zürich , CH-8093 Zürich, 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
| | | | - Thomas Ihn
- Solid State Physics Laboratory, ETH Zürich , CH-8093 Zürich, Switzerland
| | - Klaus Ensslin
- Solid State Physics Laboratory, ETH Zürich , CH-8093 Zürich, Switzerland
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30
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Allen MT, Shtanko O, Fulga IC, Wang JIJ, Nurgaliev D, Watanabe K, Taniguchi T, Akhmerov AR, Jarillo-Herrero P, Levitov LS, Yacoby A. Observation of Electron Coherence and Fabry-Perot Standing Waves at a Graphene Edge. NANO LETTERS 2017; 17:7380-7386. [PMID: 29045153 DOI: 10.1021/acs.nanolett.7b03156] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Electron surface states in solids are typically confined to the outermost atomic layers and, due to surface disorder, have negligible impact on electronic transport. Here, we demonstrate a very different behavior for surface states in graphene. We probe the wavelike character of these states by Fabry-Perot (FP) interferometry and find that, in contrast to theoretical predictions, these states can propagate ballistically over micron-scale distances. This is achieved by embedding a graphene resonator formed by gate-defined p-n junctions within a graphene superconductor-normal-superconductor structure. By combining superconducting Aharanov-Bohm interferometry with Fourier methods, we visualize spatially resolved current flow and image FP resonances due to p-n-p cavity modes. The coherence of the standing-wave edge states is revealed by observing a new family of FP resonances, which coexist with the bulk resonances. The edge resonances have periodicity distinct from that of the bulk states manifest in a repeated spatial redistribution of current on and off the FP resonances. This behavior is accompanied by a modulation of the multiple Andreev reflection amplitude on-and-off resonance, indicating that electrons propagate ballistically in a fully coherent fashion. These results, which were not anticipated by theory, provide a practical route to developing electron analog of optical FP resonators at the graphene edge.
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Affiliation(s)
- Monica T Allen
- Department of Physics, Harvard University , 17 Oxford Street, Cambridge, Massachusetts 02138, United States
| | - Oles Shtanko
- Department of Physics, Massachusetts Institute of Technology , 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | - Ion C Fulga
- Department of Condensed Matter Physics, Weizmann Institute of Science , 234 Herzl Street, Rehovot 7610001, Israel
- Institute for Theoretical Solid State Physics, IFW Dresden , 01171 Dresden, Germany
| | - Joel I-J Wang
- Department of Physics, Massachusetts Institute of Technology , 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | - Daniyar Nurgaliev
- Department of Physics, Harvard University , 17 Oxford Street, Cambridge, Massachusetts 02138, United States
| | - Kenji Watanabe
- Environment and Energy Materials Division, National Institute for Materials Science , 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan
| | - Takashi Taniguchi
- Environment and Energy Materials Division, National Institute for Materials Science , 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan
| | - Anton R Akhmerov
- Kavli Institute of Nanoscience, Delft University of Technology , Lorentzweg 1, 2628 CJ Delft, The Netherlands
| | - Pablo Jarillo-Herrero
- Department of Physics, Massachusetts Institute of Technology , 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | - Leonid S Levitov
- Department of Physics, Massachusetts Institute of Technology , 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | - Amir Yacoby
- Department of Physics, Harvard University , 17 Oxford Street, Cambridge, Massachusetts 02138, United States
- Harvard John A. Paulson School of Engineering and Applied Sciences , Pierce Hall, 29 Oxford Street, Cambridge, Massachusetts 02138, United States
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31
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Zhang ZZ, Song XX, Luo G, Deng GW, Mosallanejad V, Taniguchi T, Watanabe K, Li HO, Cao G, Guo GC, Nori F, Guo GP. Electrotunable artificial molecules based on van der Waals heterostructures. SCIENCE ADVANCES 2017; 3:e1701699. [PMID: 29062893 PMCID: PMC5650488 DOI: 10.1126/sciadv.1701699] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2017] [Accepted: 09/25/2017] [Indexed: 06/02/2023]
Abstract
Quantum confinement has made it possible to detect and manipulate single-electron charge and spin states. The recent focus on two-dimensional (2D) materials has attracted significant interests on possible applications to quantum devices, including detecting and manipulating either single-electron charging behavior or spin and valley degrees of freedom. However, the most popular model systems, consisting of tunable double-quantum-dot molecules, are still extremely difficult to realize in these materials. We show that an artificial molecule can be reversibly formed in atomically thin MoS2 sandwiched in hexagonal boron nitride, with each artificial atom controlled separately by electrostatic gating. The extracted values for coupling energies at different regimes indicate a single-electron transport behavior, with the coupling strength between the quantum dots tuned monotonically. Moreover, in the low-density regime, we observe a decrease of the conductance with magnetic field, suggesting the observation of Coulomb blockade weak anti-localization. Our experiments demonstrate for the first time the realization of an artificial quantum-dot molecule in a gated MoS2 van der Waals heterostructure, which could be used to investigate spin-valley physics. The compatibility with large-scale production, gate controllability, electron-hole bipolarity, and new quantum degrees of freedom in the family of 2D materials opens new possibilities for quantum electronics and its applications.
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Affiliation(s)
- Zhuo-Zhi Zhang
- CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, Anhui 230026, China
- Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Xiang-Xiang Song
- CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, Anhui 230026, China
- Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Gang Luo
- CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, Anhui 230026, China
- Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Guang-Wei Deng
- CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, Anhui 230026, China
- Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Vahid Mosallanejad
- CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, Anhui 230026, China
- Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Takashi Taniguchi
- National Institute for Materials Science, Namiki 1-1, Ibaraki 305-0044, Japan
| | - Kenji Watanabe
- National Institute for Materials Science, Namiki 1-1, Ibaraki 305-0044, Japan
| | - Hai-Ou Li
- CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, Anhui 230026, China
- Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Gang Cao
- CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, Anhui 230026, China
- Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Guang-Can Guo
- CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, Anhui 230026, China
- Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Franco Nori
- CEMS, RIKEN, Wako-shi, Saitama 351-0198, Japan
- Department of Physics, University of Michigan, Ann Arbor, MI 48109–1040, USA
| | - Guo-Ping Guo
- CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, Anhui 230026, China
- Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
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32
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Realisation of topological zero-energy mode in bilayer graphene in zero magnetic field. Sci Rep 2017; 7:6466. [PMID: 28743948 PMCID: PMC5527089 DOI: 10.1038/s41598-017-06902-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2017] [Accepted: 06/20/2017] [Indexed: 12/03/2022] Open
Abstract
Bilayer graphene (BLG) gapped by a vertical electric field represents a valley-symmetry-protected topological insulating state. Emergence of a new topological zero-energy mode has been proposed in BLG at a boundary between regions of inverted band gaps induced by two oppositely polarized vertical electric fields. However, its realisation has been challenged by the enormous difficulty in arranging two pairs of accurately aligned split gates on the top and bottom surfaces of clean BLG. Here we report realisation of the topological zero-energy mode in ballistic BLG, with zero-bias differential conductance close to the ideal value of 4 e2/h (e is the electron charge and h is Planck’s constant) along a boundary channel between a pair of gate-defined inverted band gaps. This constitutes the bona fide electrical-gate-tuned generation of a valley-symmetry-protected topological boundary conducting channel in BLG in zero magnetic field, which is essential to valleytronics applications of BLG.
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33
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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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34
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Luo G, Zhang ZZ, Deng GW, Li HO, Cao G, Xiao M, Guo GC, Guo GP. Coupling graphene nanomechanical motion to a single-electron transistor. NANOSCALE 2017; 9:5608-5614. [PMID: 28422197 DOI: 10.1039/c6nr09768e] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Graphene-based electromechanical resonators have attracted great interest recently because of the outstanding mechanical and electrical properties of graphene and their various applications. However, the coupling between mechanical motion and charge transport has not been explored in graphene. Herein, we studied the mechanical properties of a suspended 50 nm wide graphene nanoribbon, which also acts as a single-electron transistor (SET) at low temperatures. Using the SET as a sensitive detector, we found that the resonance frequency could be tuned from 82 MHz to 100 MHz and the quality factor exceeded 30 000. The strong charge-mechanical coupling was demonstrated by observing the SET induced ∼140 kHz resonance frequency shifts and mechanical damping. We also found that the SET can enhance the nonlinearity of the resonator. Our SET-coupled graphene mechanical resonator could approach an ultra-sensitive mass resolution of ∼0.55 × 10-21 g and a force sensitivity of ∼1.9 × 10-19 N (Hz)-1/2, and can be further improved. These properties indicate that our device is a good platform for both fundamental physical studies and potential applications.
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Affiliation(s)
- Gang Luo
- Key Laboratory of Quantum Information, University of Science and Technology of China, Chinese Academy of Sciences, Hefei 230026, China.
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35
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Rostami H, Asgari R, Guinea F. Edge modes in zigzag and armchair ribbons of monolayer MoS 2. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2016; 28:495001. [PMID: 27731311 DOI: 10.1088/0953-8984/28/49/495001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
We explore the electronic structure, orbital character and topological aspect of a monolayer MoS2 nanoribbon using tight-binding (TB) and low-energy ([Formula: see text]) models. We obtain a mid-gap edge mode in the zigzag ribbon of monolayer MoS2, which can be traced back to the topological properties of the bulk band structure. Monolayer MoS2 can be considered as a valley Hall insulator. The boundary conditions at armchair edges mix the valleys on the edges, and a gap is induced in the edge modes. The spin-orbit coupling in the valence band reduces the hybridization of the bulk states.
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Affiliation(s)
- Habib Rostami
- Istituto Italiano di Tecnologia, Graphene Labs, Via Morego 30, I-16163 Genova, Italy. School of Physics, Institute for Research in Fundamental Sciences (IPM), Tehran 19395-5531, Iran
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36
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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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37
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Freitag NM, Chizhova L, Nemes-Incze P, Woods CR, Gorbachev RV, Cao Y, Geim AK, Novoselov KS, Burgdörfer J, Libisch F, Morgenstern M. Electrostatically Confined Monolayer Graphene Quantum Dots with Orbital and Valley Splittings. NANO LETTERS 2016; 16:5798-805. [PMID: 27466881 PMCID: PMC5031393 DOI: 10.1021/acs.nanolett.6b02548] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2016] [Revised: 07/22/2016] [Indexed: 05/20/2023]
Abstract
The electrostatic confinement of massless charge carriers is hampered by Klein tunneling. Circumventing this problem in graphene mainly relies on carving out nanostructures or applying electric displacement fields to open a band gap in bilayer graphene. So far, these approaches suffer from edge disorder or insufficiently controlled localization of electrons. Here we realize an alternative strategy in monolayer graphene, by combining a homogeneous magnetic field and electrostatic confinement. Using the tip of a scanning tunneling microscope, we induce a confining potential in the Landau gaps of bulk graphene without the need for physical edges. Gating the localized states toward the Fermi energy leads to regular charging sequences with more than 40 Coulomb peaks exhibiting typical addition energies of 7-20 meV. Orbital splittings of 4-10 meV and a valley splitting of about 3 meV for the first orbital state can be deduced. These experimental observations are quantitatively reproduced by tight binding calculations, which include the interactions of the graphene with the aligned hexagonal boron nitride substrate. The demonstrated confinement approach appears suitable to create quantum dots with well-defined wave function properties beyond the reach of traditional techniques.
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Affiliation(s)
- Nils M. Freitag
- II. Institute of Physics B and JARA-FIT, RWTH Aachen University, Otto-Blumenthal-Straße, 52074 Aachen, Germany
| | - Larisa
A. Chizhova
- Institute for Theoretical Physics, TU Wien, Wiedner Hauptstraße 8-10, 1040 Vienna, Austria,
EU
| | - Peter Nemes-Incze
- II. Institute of Physics B and JARA-FIT, RWTH Aachen University, Otto-Blumenthal-Straße, 52074 Aachen, Germany
| | - Colin R. Woods
- School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, United Kingdom
| | - Roman V. Gorbachev
- School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, United Kingdom
| | - Yang Cao
- School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, United Kingdom
| | - 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
| | - Joachim Burgdörfer
- Institute for Theoretical Physics, TU Wien, Wiedner Hauptstraße 8-10, 1040 Vienna, Austria,
EU
| | - Florian Libisch
- Institute for Theoretical Physics, TU Wien, Wiedner Hauptstraße 8-10, 1040 Vienna, Austria,
EU
| | - Markus Morgenstern
- II. Institute of Physics B and JARA-FIT, RWTH Aachen University, Otto-Blumenthal-Straße, 52074 Aachen, Germany
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38
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Gehring P, Sadeghi H, Sangtarash S, Lau CS, Liu J, Ardavan A, Warner JH, Lambert CJ, Briggs GAD, Mol JA. Quantum Interference in Graphene Nanoconstrictions. NANO LETTERS 2016; 16:4210-6. [PMID: 27295198 DOI: 10.1021/acs.nanolett.6b01104] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
We report quantum interference effects in the electrical conductance of chemical vapor deposited graphene nanoconstrictions fabricated using feedback controlled electroburning. The observed multimode Fabry-Pérot interferences can be attributed to reflections at potential steps inside the channel. Sharp antiresonance features with a Fano line shape are observed. Theoretical modeling reveals that these Fano resonances are due to localized states inside the constriction, which couple to the delocalized states that also give rise to the Fabry-Pérot interference patterns. This study provides new insight into the interplay between two fundamental forms of quantum interference in graphene nanoconstrictions.
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Affiliation(s)
- Pascal Gehring
- Department of Materials, University of Oxford , 16 Parks Road, Oxford OX1 3PH, United Kindom
| | - Hatef Sadeghi
- Quantum Technology Centre, Physics Department, Lancaster University , Lancaster LA1 4YB, United Kingdom
| | - Sara Sangtarash
- Quantum Technology Centre, Physics Department, Lancaster University , Lancaster LA1 4YB, United Kingdom
| | - Chit Siong Lau
- Department of Materials, University of Oxford , 16 Parks Road, Oxford OX1 3PH, United Kindom
| | - Junjie Liu
- Department of Materials, University of Oxford , 16 Parks Road, Oxford OX1 3PH, United Kindom
| | - Arzhang Ardavan
- Clarendon Laboratory, Department of Physics, University of Oxford , Parks Road, Oxford OX1 3PU, United Kingdom
| | - Jamie H Warner
- Department of Materials, University of Oxford , 16 Parks Road, Oxford OX1 3PH, United Kindom
| | - Colin J Lambert
- Quantum Technology Centre, Physics Department, Lancaster University , Lancaster LA1 4YB, United Kingdom
| | - G Andrew D Briggs
- Department of Materials, University of Oxford , 16 Parks Road, Oxford OX1 3PH, United Kindom
| | - Jan A Mol
- Department of Materials, University of Oxford , 16 Parks Road, Oxford OX1 3PH, United Kindom
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39
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Tóvári E, Makk P, Rickhaus P, Schönenberger C, Csonka S. Signatures of single quantum dots in graphene nanoribbons within the quantum Hall regime. NANOSCALE 2016; 8:11480-11486. [PMID: 27198562 PMCID: PMC5315012 DOI: 10.1039/c6nr00187d] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2016] [Accepted: 05/04/2016] [Indexed: 05/29/2023]
Abstract
We report on the observation of periodic conductance oscillations near quantum Hall plateaus in suspended graphene nanoribbons. They are attributed to single quantum dots that are formed in the narrowest part of the ribbon, in the valleys and hills of a disorder potential. In a wide flake with two gates, a double-dot system's signature has been observed. Electrostatic confinement is enabled in single-layer graphene due to the gaps that are formed between the Landau levels, suggesting a way to create gate-defined quantum dots that can be accessed with quantum Hall edge states.
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Affiliation(s)
- Endre Tóvári
- Department of Physics, Budapest University of Technology and Economics, and Condensed Matter Research Group of the Hungarian Academy of Sciences, Budafoki út 8, 1111 Budapest, Hungary.
| | - Péter Makk
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
| | - Peter Rickhaus
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
| | - Christian Schönenberger
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
| | - Szabolcs Csonka
- Department of Physics, Budapest University of Technology and Economics, and Condensed Matter Research Group of the Hungarian Academy of Sciences, Budafoki út 8, 1111 Budapest, Hungary.
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40
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Electromechanical oscillations in bilayer graphene. Nat Commun 2015; 6:8582. [PMID: 26481767 PMCID: PMC4634209 DOI: 10.1038/ncomms9582] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2014] [Accepted: 09/08/2015] [Indexed: 01/15/2023] Open
Abstract
Nanoelectromechanical systems constitute a class of devices lying at the interface between fundamental research and technological applications. Realizing nanoelectromechanical devices based on novel materials such as graphene allows studying their mechanical and electromechanical characteristics at the nanoscale and addressing fundamental questions such as electron-phonon interaction and bandgap engineering. In this work, we realize electromechanical devices using single and bilayer graphene and probe the interplay between their mechanical and electrical properties. We show that the deflection of monolayer graphene nanoribbons results in a linear increase in their electrical resistance. Surprisingly, we observe oscillations in the electromechanical response of bilayer graphene. The proposed theoretical model suggests that these oscillations arise from quantum mechanical interference in the transition region induced by sliding of individual graphene layers with respect to each other. Our work shows that bilayer graphene conceals unexpectedly rich and novel physics with promising potential in applications based on nanoelectromechanical systems.
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41
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Rickhaus P, Liu MH, Makk P, Maurand R, Hess S, Zihlmann S, Weiss M, Richter K, Schönenberger C. Guiding of Electrons in a Few-Mode Ballistic Graphene Channel. NANO LETTERS 2015; 15:5819-5825. [PMID: 26280622 DOI: 10.1021/acs.nanolett.5b01877] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
In graphene, the extremely fast charge carriers can be controlled by electron-optical elements, such as waveguides, in which the transmissivity is tuned by the wavelength. In this work, charge carriers are guided in a suspended ballistic few-mode graphene channel, defined by electrostatic gating. By depleting the channel, a reduction of mode number and steps in the conductance are observed, until the channel is completely emptied. The measurements are supported by tight-binding transport calculations including the full electrostatics of the sample.
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Affiliation(s)
- Peter Rickhaus
- Department of Physics, University of Basel , Klingelbergstrasse 82, CH-4056 Basel, Switzerland
| | - Ming-Hao Liu
- Institut für Theoretische Physik, Universität Regensburg , D-93040 Regensburg, Germany
| | - Péter Makk
- Department of Physics, University of Basel , Klingelbergstrasse 82, CH-4056 Basel, Switzerland
| | - Romain Maurand
- Department of Physics, University of Basel , Klingelbergstrasse 82, CH-4056 Basel, Switzerland
- University Grenoble Alpes, CEA-INAC-SPSMS , F-38000 Grenoble, France
| | - Samuel Hess
- Department of Physics, University of Basel , Klingelbergstrasse 82, CH-4056 Basel, Switzerland
| | - Simon Zihlmann
- Department of Physics, University of Basel , Klingelbergstrasse 82, CH-4056 Basel, Switzerland
| | - Markus Weiss
- Department of Physics, University of Basel , Klingelbergstrasse 82, CH-4056 Basel, Switzerland
| | - Klaus Richter
- Institut für Theoretische Physik, Universität Regensburg , D-93040 Regensburg, Germany
| | - Christian Schönenberger
- Department of Physics, University of Basel , Klingelbergstrasse 82, CH-4056 Basel, Switzerland
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42
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Song XX, Li HO, You J, Han TY, Cao G, Tu T, Xiao M, Guo GC, Jiang HW, Guo GP. Suspending effect on low-frequency charge noise in graphene quantum dot. Sci Rep 2015; 5:8142. [PMID: 25634250 PMCID: PMC4311243 DOI: 10.1038/srep08142] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2014] [Accepted: 01/08/2015] [Indexed: 11/10/2022] Open
Abstract
Charge noise is critical in the performance of gate-controlled quantum dots (QDs). Such information is not yet available for QDs made out of the new material graphene, where both substrate and edge states are known to have important effects. Here we show the 1/f noise for a microscopic graphene QD is substantially larger than that for a macroscopic graphene field-effect transistor (FET), increasing linearly with temperature. To understand its origin, we suspended the graphene QD above the substrate. In contrast to large area graphene FETs, we find that a suspended graphene QD has an almost-identical noise level as an unsuspended one. Tracking noise levels around the Coulomb blockade peak as a function of gate voltage yields potential fluctuations of order 1 μeV, almost one order larger than in GaAs/GaAlAs QDs. Edge states and surface impurities rather than substrate-induced disorders, appear to dominate the 1/f noise, thus affecting the coherency of graphene nano-devices.
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Affiliation(s)
- Xiang-Xiang Song
- 1] Key Laboratory of Quantum Information, CAS, University of Science and Technology of China, Hefei, Anhui 230026, China [2] Synergetic Innovation Center of Quantum Information &Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Hai-Ou Li
- 1] Key Laboratory of Quantum Information, CAS, University of Science and Technology of China, Hefei, Anhui 230026, China [2] Synergetic Innovation Center of Quantum Information &Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Jie You
- 1] Key Laboratory of Quantum Information, CAS, University of Science and Technology of China, Hefei, Anhui 230026, China [2] Synergetic Innovation Center of Quantum Information &Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Tian-Yi Han
- 1] Key Laboratory of Quantum Information, CAS, University of Science and Technology of China, Hefei, Anhui 230026, China [2] Synergetic Innovation Center of Quantum Information &Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Gang Cao
- 1] Key Laboratory of Quantum Information, CAS, University of Science and Technology of China, Hefei, Anhui 230026, China [2] Synergetic Innovation Center of Quantum Information &Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Tao Tu
- 1] Key Laboratory of Quantum Information, CAS, University of Science and Technology of China, Hefei, Anhui 230026, China [2] Synergetic Innovation Center of Quantum Information &Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Ming Xiao
- 1] Key Laboratory of Quantum Information, CAS, University of Science and Technology of China, Hefei, Anhui 230026, China [2] Synergetic Innovation Center of Quantum Information &Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Guang-Can Guo
- 1] Key Laboratory of Quantum Information, CAS, University of Science and Technology of China, Hefei, Anhui 230026, China [2] Synergetic Innovation Center of Quantum Information &Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Hong-Wen Jiang
- Department of Physics and Astronomy, University of California at Los Angeles, CA 90095, USA
| | - Guo-Ping Guo
- 1] Key Laboratory of Quantum Information, CAS, University of Science and Technology of China, Hefei, Anhui 230026, China [2] Synergetic Innovation Center of Quantum Information &Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
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43
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Bhadrachalam P, Subramanian R, Ray V, Ma LC, Wang W, Kim J, Cho K, Koh SJ. Energy-filtered cold electron transport at room temperature. Nat Commun 2014; 5:4745. [PMID: 25204839 PMCID: PMC4175579 DOI: 10.1038/ncomms5745] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2014] [Accepted: 07/18/2014] [Indexed: 11/25/2022] Open
Abstract
Fermi-Dirac electron thermal excitation is an intrinsic phenomenon that limits
functionality of various electron systems. Efforts to manipulate electron thermal
excitation have been successful when the entire system is cooled to cryogenic
temperatures, typically <1 K. Here we show that electron thermal
excitation can be effectively suppressed at room temperature, and energy-suppressed
electrons, whose energy distribution corresponds to an effective electron
temperature of ~45 K, can be transported throughout device
components without external cooling. This is accomplished using a discrete level of
a quantum well, which filters out thermally excited electrons and permits only
energy-suppressed electrons to participate in electron transport. The quantum well
(~2 nm of Cr2O3) is formed between source
(Cr) and tunnelling barrier
(SiO2) in a
double-barrier-tunnelling-junction structure having a quantum dot as the central
island. Cold electron transport is detected from extremely narrow differential
conductance peaks in electron tunnelling through CdSe quantum dots, with full widths at half maximum of only
~15 mV at room temperature. Electrons can behave as if they are at a temperature different from
that of the solid in which they are embedded. Here, the authors demonstrate a room
temperature device that can generate electrons with an effective temperature of
45 K by using quantum wells to filter out energetic particles.
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Affiliation(s)
- Pradeep Bhadrachalam
- 1] Department of Materials Science and Engineering, University of Texas at Arlington, Arlington, Texas 76019, USA [2] Nanotechnology Research Center, University of Texas at Arlington, Arlington, Texas 76019, USA
| | - Ramkumar Subramanian
- 1] Department of Materials Science and Engineering, University of Texas at Arlington, Arlington, Texas 76019, USA [2] Nanotechnology Research Center, University of Texas at Arlington, Arlington, Texas 76019, USA
| | - Vishva Ray
- 1] Department of Materials Science and Engineering, University of Texas at Arlington, Arlington, Texas 76019, USA [2] Nanotechnology Research Center, University of Texas at Arlington, Arlington, Texas 76019, USA
| | - Liang-Chieh Ma
- 1] Department of Materials Science and Engineering, University of Texas at Arlington, Arlington, Texas 76019, USA [2] Nanotechnology Research Center, University of Texas at Arlington, Arlington, Texas 76019, USA
| | - Weichao Wang
- Department of Materials Science and Engineering, University of Texas at Dallas, Richardson, Texas 75080, USA
| | - Jiyoung Kim
- Department of Materials Science and Engineering, University of Texas at Dallas, Richardson, Texas 75080, USA
| | - Kyeongjae Cho
- Department of Materials Science and Engineering, University of Texas at Dallas, Richardson, Texas 75080, USA
| | - Seong Jin Koh
- 1] Department of Materials Science and Engineering, University of Texas at Arlington, Arlington, Texas 76019, USA [2] Nanotechnology Research Center, University of Texas at Arlington, Arlington, Texas 76019, USA
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44
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Han Q, Yan B, Gao T, Meng J, Zhang Y, Liu Z, Wu X, Yu D. Boron nitride film as a buffer layer in deposition of dielectrics on graphene. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2014; 10:2293-2299. [PMID: 24599538 DOI: 10.1002/smll.201303697] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2013] [Revised: 01/24/2014] [Indexed: 06/03/2023]
Abstract
As a two-dimensional material, graphene is highly susceptible to environmental influences. It is therefore challenging to deposit dielectrics on graphene without affecting its electronic properties. It is demonstrated that the effect of the dielectric deposition on graphene can be reduced by using a multilayer hexagonal boron nitride film as a buffer layer. Particularly, the boron nitride layer provides significant protection in magnetron sputtering deposition. It also enables growth of uniform and charge trapping free high-k dielectrics by atomic layer deposition. The doping effect of various deposition methods on graphene has been discussed.
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Affiliation(s)
- Qi Han
- State Key Laboratory for Artificial Microstructure and Mesoscopic Physics, Peking University, Beijing, 100871, China; Collaborative Innovation Center of Quantum Matter, Beijing, 100871, China
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45
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Chang CP. An analytical approach for the energy spectrum and optical properties of gated bilayer graphene. RSC Adv 2014. [DOI: 10.1039/c4ra03430a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
An analytical approach is developed to access the exact energy spectrum, wave functions, dipole matrix element (Mfi) and absorption spectra (A(ω)) of gated Bernal bilayer graphene.
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Affiliation(s)
- Cheng-Peng Chang
- Center for General Education
- Tainan University of Technology
- 710 Tainan, Taiwan
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46
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Goossens ASM, Driessen SCM, Baart TA, Watanabe K, Taniguchi T, Vandersypen LMK. Gate-defined confinement in bilayer graphene-hexagonal boron nitride hybrid devices. NANO LETTERS 2012; 12:4656-4660. [PMID: 22906072 DOI: 10.1021/nl301986q] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We report on the fabrication and measurement of nanoscale devices that permit electrostatic confinement in bilayer graphene on a substrate. The graphene bilayer is sandwiched between hexagonal boron nitride bottom and top gate dielectrics. Top gates are patterned such that constrictions and islands can be electrostatically induced. The high quality of the devices becomes apparent from the smooth pinch-off characteristics of the constrictions at low temperature with features indicative of conductance quantization. The islands exhibit clear Coulomb blockade and single-electron transport.
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Affiliation(s)
- Augustinus Stijn M Goossens
- Kavli Institute of Nanoscience, Delft University of Technology, P.O. Box 5046, 2600 GA Delft, The Netherlands.
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