1
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Shilov AL, Kashchenko MA, Pantaleón Peralta PA, Wang Y, Kravtsov M, Kudriashov A, Zhan Z, Taniguchi T, Watanabe K, Slizovskiy S, Novoselov KS, Fal'ko VI, Guinea F, Bandurin DA. High-Mobility Compensated Semimetals, Orbital Magnetization, and Umklapp Scattering in Bilayer Graphene Moiré Superlattices. ACS Nano 2024; 18:11769-11777. [PMID: 38648369 DOI: 10.1021/acsnano.3c13212] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/25/2024]
Abstract
Twist-controlled moiré superlattices (MSs) have emerged as a versatile platform for realizing artificial systems with complex electronic spectra. The combination of Bernal-stacked bilayer graphene (BLG) and hexagonal boron nitride (hBN) can give rise to an interesting MS, which has recently featured a set of unexpected behaviors, such as unconventional ferroelectricity and the electronic ratchet effect. Yet, the understanding of the electronic properties of BLG/hBN MS has, at present, remained fairly limited. Here, we combine magneto-transport and low-energy sub-THz excitation to gain insights into the properties of this MS. We demonstrate that the alignment between BLG and hBN crystal lattices results in the emergence of compensated semimetals at some integer fillings of the moiré bands, separated by van Hove singularities where the Lifshitz transition occurs. A particularly pronounced semimetal develops when eight holes reside in the moiré unit cell, where coexisting high-mobility electron and hole systems feature strong magnetoresistance reaching 2350% already at B = 0.25 T. Next, by measuring the THz-driven Nernst effect in remote bands, we observe valley splitting, indicating an orbital magnetization characterized by a strongly enhanced effective gv-factor of 340. Finally, using THz photoresistance measurements, we show that the high-temperature conductivity of the BLG/hBN MS is limited by electron-electron umklapp processes. Our multifaceted analysis introduces THz-driven magnetotransport as a convenient tool to probe the band structure and interaction effects in van der Waals materials and provides a comprehensive understanding of the BLG/hBN MS.
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Affiliation(s)
- Artur L Shilov
- Department of Materials Science and Engineering, National University of Singapore, Singapore 117575, Singapore
| | - Mikhail A Kashchenko
- Programmable Functional Materials Lab, Center for Neurophysics and Neuromorphic Technologies, Moscow 127495, Russia
| | | | - Yibo Wang
- Institute for Functional Intelligent Materials, National University of Singapore, Singapore 117575, Singapore
| | - Mikhail Kravtsov
- Department of Materials Science and Engineering, National University of Singapore, Singapore 117575, Singapore
- Institute for Functional Intelligent Materials, National University of Singapore, Singapore 117575, Singapore
| | - Andrei Kudriashov
- Department of Materials Science and Engineering, National University of Singapore, Singapore 117575, Singapore
- Institute for Functional Intelligent Materials, National University of Singapore, Singapore 117575, Singapore
| | - Zhen Zhan
- IMDEA Nanoscience, Faraday 9, Madrid 28015, Spain
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute of Material Science, Tsukuba 305-0044, Japan
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute of Material Science, Tsukuba 305-0044, Japan
| | - Sergey Slizovskiy
- School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, U.K
| | - Kostya S Novoselov
- Institute for Functional Intelligent Materials, National University of Singapore, Singapore 117575, Singapore
| | - Vladimir I Fal'ko
- School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, U.K
| | - Francisco Guinea
- IMDEA Nanoscience, Faraday 9, Madrid 28015, Spain
- Donostia International Physics Center, Paseo Manuel de Lardizábal 4, San Sebastián 20018, Spain
| | - Denis A Bandurin
- Department of Materials Science and Engineering, National University of Singapore, Singapore 117575, Singapore
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2
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de Vries F, Slizovskiy S, Tomić P, Krishna Kumar R, Garcia-Ruiz A, Zheng G, Portolés E, Ponomarenko LA, Geim AK, Watanabe K, Taniguchi T, Fal’ko V, Ensslin K, Ihn T, Rickhaus P. Kagome Quantum Oscillations in Graphene Superlattices. Nano Lett 2024; 24:601-606. [PMID: 38180909 PMCID: PMC10797620 DOI: 10.1021/acs.nanolett.3c03524] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2023] [Revised: 12/17/2023] [Accepted: 12/19/2023] [Indexed: 01/07/2024]
Abstract
Electronic spectra of solids subjected to a magnetic field are often discussed in terms of Landau levels and Hofstadter-butterfly-style Brown-Zak minibands manifested by magneto-oscillations in two-dimensional electron systems. Here, we present the semiclassical precursors of these quantum magneto-oscillations which appear in graphene superlattices at low magnetic field near the Lifshitz transitions and persist at elevated temperatures. These oscillations originate from Aharonov-Bohm interference of electron waves following open trajectories that belong to a kagome-shaped network of paths characteristic for Lifshitz transitions in the moire superlattice minibands of twistronic graphenes.
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Affiliation(s)
| | - Sergey Slizovskiy
- National
Graphene Institute, University of Manchester, Manchester M13 9PL, United Kingdom
- Department
of Physics & Astronomy, University of
Manchester, Manchester M13 9PL, United Kingdom
| | - Petar Tomić
- Laboratory
for Solid State Physics, ETH Zürich, Zürich CH-8093, Switzerland
| | - Roshan Krishna Kumar
- National
Graphene Institute, University of Manchester, Manchester M13 9PL, United Kingdom
- Department
of Physics & Astronomy, University of
Manchester, Manchester M13 9PL, United Kingdom
- ICFO-Institut
de Ciencies Fotoniques, The Barcelona Institute
of Science and Technology, Barcelona 08028, Spain
| | - Aitor Garcia-Ruiz
- National
Graphene Institute, University of Manchester, Manchester M13 9PL, United Kingdom
- Department
of Physics & Astronomy, University of
Manchester, Manchester M13 9PL, United Kingdom
| | - Giulia Zheng
- Laboratory
for Solid State Physics, ETH Zürich, Zürich CH-8093, Switzerland
| | - Elías Portolés
- Laboratory
for Solid State Physics, ETH Zürich, Zürich CH-8093, Switzerland
| | | | - Andre K. Geim
- National
Graphene Institute, University of Manchester, Manchester M13 9PL, United Kingdom
- Department
of Physics & Astronomy, University of
Manchester, Manchester M13 9PL, United Kingdom
| | - Kenji Watanabe
- National
Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- National
Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Vladimir Fal’ko
- National
Graphene Institute, University of Manchester, Manchester M13 9PL, United Kingdom
- Department
of Physics & Astronomy, University of
Manchester, Manchester M13 9PL, United Kingdom
- Henry
Royce
Institute for Advanced Materials, Manchester M13 9PL, United Kingdom
| | - Klaus Ensslin
- Laboratory
for Solid State Physics, ETH Zürich, Zürich CH-8093, Switzerland
| | - Thomas Ihn
- Laboratory
for Solid State Physics, ETH Zürich, Zürich CH-8093, Switzerland
| | - Peter Rickhaus
- Laboratory
for Solid State Physics, ETH Zürich, Zürich CH-8093, Switzerland
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3
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Mullan C, Slizovskiy S, Yin J, Wang Z, Yang Q, Xu S, Yang Y, Piot BA, Hu S, Taniguchi T, Watanabe K, Novoselov KS, Geim AK, Fal'ko VI, Mishchenko A. Mixing of moiré-surface and bulk states in graphite. Nature 2023; 620:756-761. [PMID: 37468634 PMCID: PMC10447246 DOI: 10.1038/s41586-023-06264-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2022] [Accepted: 05/25/2023] [Indexed: 07/21/2023]
Abstract
Van der Waals assembly enables the design of electronic states in two-dimensional (2D) materials, often by superimposing a long-wavelength periodic potential on a crystal lattice using moiré superlattices1-9. This twistronics approach has resulted in numerous previously undescribed physics, including strong correlations and superconductivity in twisted bilayer graphene10-12, resonant excitons, charge ordering and Wigner crystallization in transition-metal chalcogenide moiré structures13-18 and Hofstadter's butterfly spectra and Brown-Zak quantum oscillations in graphene superlattices19-22. Moreover, twistronics has been used to modify near-surface states at the interface between van der Waals crystals23,24. Here we show that electronic states in three-dimensional (3D) crystals such as graphite can be tuned by a superlattice potential occurring at the interface with another crystal-namely, crystallographically aligned hexagonal boron nitride. This alignment results in several Lifshitz transitions and Brown-Zak oscillations arising from near-surface states, whereas, in high magnetic fields, fractal states of Hofstadter's butterfly draw deep into the bulk of graphite. Our work shows a way in which 3D spectra can be controlled using the approach of 2D twistronics.
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Affiliation(s)
- Ciaran Mullan
- Department of Physics and Astronomy, University of Manchester, Manchester, UK
| | - Sergey Slizovskiy
- Department of Physics and Astronomy, University of Manchester, Manchester, UK
- National Graphene Institute, University of Manchester, Manchester, UK
| | - Jun Yin
- Department of Physics and Astronomy, University of Manchester, Manchester, UK.
- State Key Laboratory of Mechanics and Control for Aerospace Structures, Key Laboratory for Intelligent Nano Materials and Devices of Ministry of Education, Institute for Frontier Science, Nanjing University of Aeronautics and Astronautics, Nanjing, China.
| | - Ziwei Wang
- Department of Physics and Astronomy, University of Manchester, Manchester, UK
| | - Qian Yang
- Department of Physics and Astronomy, University of Manchester, Manchester, UK
- National Graphene Institute, University of Manchester, Manchester, UK
| | - Shuigang Xu
- National Graphene Institute, University of Manchester, Manchester, UK
- Key Laboratory for Quantum Materials of Zhejiang Province, Department of Physics, School of Science, Westlake University, Hangzhou, China
| | - Yaping Yang
- Department of Physics and Astronomy, University of Manchester, Manchester, UK
- National Graphene Institute, University of Manchester, Manchester, UK
| | - Benjamin A Piot
- Laboratoire National des Champs Magnétiques Intenses (LNCMI), CNRS Université Grenoble Alpes, Université Toulouse 3, INSA Toulouse, EMFL, Grenoble, France
| | - Sheng Hu
- National Graphene Institute, University of Manchester, Manchester, UK
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, China
| | | | - Kenji Watanabe
- National Institute for Materials Science, Tsukuba, Japan
| | - Kostya S Novoselov
- Department of Physics and Astronomy, University of Manchester, Manchester, UK
- National Graphene Institute, University of Manchester, Manchester, UK
- Institute for Functional Intelligent Materials, National University of Singapore, Singapore, Singapore
| | - A K Geim
- Department of Physics and Astronomy, University of Manchester, Manchester, UK
- National Graphene Institute, University of Manchester, Manchester, UK
| | - Vladimir I Fal'ko
- Department of Physics and Astronomy, University of Manchester, Manchester, UK.
- National Graphene Institute, University of Manchester, Manchester, UK.
- Henry Royce Institute for Advanced Materials, Manchester, UK.
| | - Artem Mishchenko
- Department of Physics and Astronomy, University of Manchester, Manchester, UK.
- National Graphene Institute, University of Manchester, Manchester, UK.
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4
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Ge Z, Slizovskiy S, Polizogopoulos P, Joshi T, Taniguchi T, Watanabe K, Lederman D, Fal'ko VI, Velasco J. Giant orbital magnetic moments and paramagnetic shift in artificial relativistic atoms and molecules. Nat Nanotechnol 2023; 18:250-256. [PMID: 36879123 DOI: 10.1038/s41565-023-01327-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Accepted: 01/13/2023] [Indexed: 06/18/2023]
Abstract
Materials such as graphene and topological insulators host massless Dirac fermions that enable the study of relativistic quantum phenomena. Single quantum dots and coupled quantum dots formed with massless Dirac fermions can be viewed as artificial relativistic atoms and molecules, respectively. Such structures offer a unique testbed to study atomic and molecular physics in the ultrarelativistic regime (particle speed close to the speed of light). Here we use a scanning tunnelling microscope to create and probe single and coupled electrostatically defined graphene quantum dots to unravel the magnetic-field responses of artificial relativistic nanostructures. We observe a giant orbital Zeeman splitting and orbital magnetic moment up to ~70 meV T-1 and ~600μB (μB, Bohr magneton) in single graphene quantum dots. For coupled graphene quantum dots, Aharonov-Bohm oscillations and a strong Van Vleck paramagnetic shift of ~20 meV T-2 are observed. Our findings provide fundamental insights into relativistic quantum dot states, which can be potentially leveraged for use in quantum information science.
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Affiliation(s)
- Zhehao Ge
- Department of Physics, University of California Santa Cruz, Santa Cruz, CA, USA
| | - Sergey Slizovskiy
- Department of Physics and Astronomy, University of Manchester, Manchester, UK
- National Graphene Institute, University of Manchester, Booth Street East, Manchester, UK
| | | | - Toyanath Joshi
- Department of Physics, University of California Santa Cruz, Santa Cruz, CA, USA
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics and National Institute for Materials Science, Tsukuba, Japan
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, Tsukuba, Japan
| | - David Lederman
- Department of Physics, University of California Santa Cruz, Santa Cruz, CA, USA
| | - Vladimir I Fal'ko
- Department of Physics and Astronomy, University of Manchester, Manchester, UK.
- National Graphene Institute, University of Manchester, Booth Street East, Manchester, UK.
- Henry Royce Institute for Advanced Materials, Manchester, UK.
| | - Jairo Velasco
- Department of Physics, University of California Santa Cruz, Santa Cruz, CA, USA.
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5
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Berdyugin AI, Xin N, Gao H, Slizovskiy S, Dong Z, Bhattacharjee S, Kumaravadivel P, Xu S, Ponomarenko LA, Holwill M, Bandurin DA, Kim M, Cao Y, Greenaway MT, Novoselov KS, Grigorieva IV, Watanabe K, Taniguchi T, Fal'ko VI, Levitov LS, Kumar RK, Geim AK. Out-of-equilibrium criticalities in graphene superlattices. Science 2022; 375:430-433. [PMID: 35084955 DOI: 10.1126/science.abi8627] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
In thermodynamic equilibrium, current in metallic systems is carried by electronic states near the Fermi energy, whereas the filled bands underneath contribute little to conduction. Here, we describe a very different regime in which carrier distribution in graphene and its superlattices is shifted so far from equilibrium that the filled bands start playing an essential role, leading to a critical-current behavior. The criticalities develop upon the velocity of electron flow reaching the Fermi velocity. Key signatures of the out-of-equilibrium state are current-voltage characteristics that resemble those of superconductors, sharp peaks in differential resistance, sign reversal of the Hall effect, and a marked anomaly caused by the Schwinger-like production of hot electron-hole plasma. The observed behavior is expected to be common to all graphene-based superlattices.
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Affiliation(s)
- Alexey I Berdyugin
- School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK.,National Graphene Institute, University of Manchester, Manchester M13 9PL, UK
| | - Na Xin
- School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK.,National Graphene Institute, University of Manchester, Manchester M13 9PL, UK
| | - Haoyang Gao
- Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Sergey Slizovskiy
- School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK.,National Graphene Institute, University of Manchester, Manchester M13 9PL, UK
| | - Zhiyu Dong
- Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Shubhadeep Bhattacharjee
- School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK.,National Graphene Institute, University of Manchester, Manchester M13 9PL, UK
| | - P Kumaravadivel
- School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK.,National Graphene Institute, University of Manchester, Manchester M13 9PL, UK
| | - Shuigang Xu
- School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK.,National Graphene Institute, University of Manchester, Manchester M13 9PL, UK
| | - L A Ponomarenko
- School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK.,Department of Physics, University of Lancaster, Lancaster LA1 4YW, UK
| | - Matthew Holwill
- School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK.,National Graphene Institute, University of Manchester, Manchester M13 9PL, UK
| | - D A Bandurin
- School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK.,National Graphene Institute, University of Manchester, Manchester M13 9PL, UK
| | - Minsoo Kim
- School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK.,National Graphene Institute, University of Manchester, Manchester M13 9PL, UK
| | - Yang Cao
- School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK.,National Graphene Institute, University of Manchester, Manchester M13 9PL, UK
| | - M T Greenaway
- Department of Physics, Loughborough University, Loughborough LE11 3TU, UK.,School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD, UK
| | - K S Novoselov
- National Graphene Institute, University of Manchester, Manchester M13 9PL, UK
| | - I V Grigorieva
- School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK
| | - K Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - T Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - V I Fal'ko
- School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK.,National Graphene Institute, University of Manchester, Manchester M13 9PL, UK.,Henry Royce Institute for Advanced Materials, Manchester M13 9PL, UK
| | - L S Levitov
- Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Roshan Krishna Kumar
- School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK.,National Graphene Institute, University of Manchester, Manchester M13 9PL, UK.,Institut de Ciencies Fotoniques (ICFO), Barcelona Institute of Science and Technology, 08860 Castelldefels, Barcelona, Spain
| | - A K Geim
- School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK.,National Graphene Institute, University of Manchester, Manchester M13 9PL, UK
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6
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Ge Z, Slizovskiy S, Joucken F, Quezada EA, Taniguchi T, Watanabe K, Fal'ko VI, Velasco J. Control of Giant Topological Magnetic Moment and Valley Splitting in Trilayer Graphene. Phys Rev Lett 2021; 127:136402. [PMID: 34623864 DOI: 10.1103/physrevlett.127.136402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2021] [Accepted: 08/17/2021] [Indexed: 06/13/2023]
Abstract
Bloch states of electrons in honeycomb two-dimensional crystals with multivalley band structure and broken inversion symmetry have orbital magnetic moments of a topological nature. In crystals with two degenerate valleys, a perpendicular magnetic field lifts the valley degeneracy via a Zeeman effect due to these magnetic moments, leading to magnetoelectric effects which can be leveraged for creating valleytronic devices. In this work, we demonstrate that trilayer graphene with Bernal stacking (ABA TLG), hosts topological magnetic moments with a large and widely tunable valley g factor (g_{ν}), reaching a value g_{ν}∼1050 at the extreme of the studied parametric range. The reported experiment consists in sublattice-resolved scanning tunneling spectroscopy under perpendicular electric and magnetic fields that control the TLG bands. The tunneling spectra agree very well with the results of theoretical modeling that includes the full details of the TLG tight-binding model and accounts for a quantum-dot-like potential profile formed electrostatically under the scanning tunneling microscope tip.
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Affiliation(s)
- Zhehao Ge
- Department of Physics, University of California, Santa Cruz, California 95064, USA
| | - Sergey Slizovskiy
- Department of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom
- National Graphene Institute, University of Manchester, Booth Street East, Manchester M13 9PL, United Kingdom
| | - Frédéric Joucken
- Department of Physics, University of California, Santa Cruz, California 95064, USA
| | - Eberth A Quezada
- Department of Physics, University of California, Santa Cruz, California 95064, USA
| | - 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
| | - Vladimir I Fal'ko
- Department of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom
- National Graphene Institute, University of Manchester, Booth Street East, Manchester M13 9PL, United Kingdom
- Henry Royce Institute for Advanced Materials, Manchester M13 9PL, United Kingdom
| | - Jairo Velasco
- Department of Physics, University of California, Santa Cruz, California 95064, USA
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7
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Slizovskiy S, Garcia-Ruiz A, Berdyugin A, Xin N, Taniguchi T, Watanabe K, Geim AK, Drummond ND, Fal’ko V. Out-of-Plane Dielectric Susceptibility of Graphene in Twistronic and Bernal Bilayers. Nano Lett 2021; 21:6678-6683. [PMID: 34296602 PMCID: PMC8361429 DOI: 10.1021/acs.nanolett.1c02211] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2021] [Revised: 07/14/2021] [Indexed: 05/27/2023]
Abstract
We describe how the out-of-plane dielectric polarizability of monolayer graphene influences the electrostatics of bilayer graphene-both Bernal (BLG) and twisted (tBLG). We compare the polarizability value computed using density functional theory with the output from previously published experimental data on the electrostatically controlled interlayer asymmetry potential in BLG and data on the on-layer density distribution in tBLG. We show that monolayers in tBLG are described well by polarizability αexp = 10.8 Å3 and effective out-of-plane dielectric susceptibility ϵz = 2.5, including their on-layer electron density distribution at zero magnetic field and the interlayer Landau level pinning at quantizing magnetic fields.
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Affiliation(s)
- Sergey Slizovskiy
- National
Graphene Institute, University of Manchester, Booth St.E., M13 9PL Manchester, U.K.
- Dept.
of Physics & Astronomy, University of
Manchester, Manchester M13 9PL, U.K.
| | - Aitor Garcia-Ruiz
- National
Graphene Institute, University of Manchester, Booth St.E., M13 9PL Manchester, U.K.
- Dept.
of Physics & Astronomy, University of
Manchester, Manchester M13 9PL, U.K.
| | - Alexey
I. Berdyugin
- National
Graphene Institute, University of Manchester, Booth St.E., M13 9PL Manchester, U.K.
- Dept.
of Physics & Astronomy, University of
Manchester, Manchester M13 9PL, U.K.
| | - Na Xin
- National
Graphene Institute, University of Manchester, Booth St.E., M13 9PL Manchester, U.K.
- Dept.
of Physics & Astronomy, University of
Manchester, Manchester M13 9PL, U.K.
| | - 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
| | - Andre K. Geim
- National
Graphene Institute, University of Manchester, Booth St.E., M13 9PL Manchester, U.K.
- Dept.
of Physics & Astronomy, University of
Manchester, Manchester M13 9PL, U.K.
| | - Neil D. Drummond
- Department
of Physics, Lancaster University, Lancaster LA1 4YB, U.K.
| | - Vladimir
I. Fal’ko
- National
Graphene Institute, University of Manchester, Booth St.E., M13 9PL Manchester, U.K.
- Dept.
of Physics & Astronomy, University of
Manchester, Manchester M13 9PL, U.K.
- Henry
Royce Institute for Advanced Materials, Manchester M13 9PL, U.K.
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8
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Shi Y, Xu S, Yang Y, Slizovskiy S, Morozov SV, Son SK, Ozdemir S, Mullan C, Barrier J, Yin J, Berdyugin AI, Piot BA, Taniguchi T, Watanabe K, Fal’ko VI, Novoselov KS, Geim AK, Mishchenko A. Electronic phase separation in multilayer rhombohedral graphite. Nature 2020; 584:210-214. [DOI: 10.1038/s41586-020-2568-2] [Citation(s) in RCA: 48] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2019] [Accepted: 05/05/2020] [Indexed: 11/09/2022]
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9
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Kim M, Xu SG, Berdyugin AI, Principi A, Slizovskiy S, Xin N, Kumaravadivel P, Kuang W, Hamer M, Kumar RK, Gorbachev RV, Watanabe K, Taniguchi T, Grigorieva IV, Fal'ko VI, Polini M, Geim AK. Publisher Correction: Control of electron-electron interaction in graphene by proximity screening. Nat Commun 2020; 11:3054. [PMID: 32528007 PMCID: PMC7289850 DOI: 10.1038/s41467-020-16708-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Affiliation(s)
- M Kim
- School of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, UK
| | - S G Xu
- School of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, UK.,National Graphene Institute, University of Manchester, Manchester, M13 9PL, UK
| | - A I Berdyugin
- School of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, UK
| | - A Principi
- School of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, UK
| | - S Slizovskiy
- School of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, UK.,National Graphene Institute, University of Manchester, Manchester, M13 9PL, UK.,Saint-Petersburg INP, Gatchina, 188300, Russia
| | - N Xin
- School of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, UK.,National Graphene Institute, University of Manchester, Manchester, M13 9PL, UK
| | - P Kumaravadivel
- School of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, UK.,National Graphene Institute, University of Manchester, Manchester, M13 9PL, UK
| | - W Kuang
- School of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, UK
| | - M Hamer
- National Graphene Institute, University of Manchester, Manchester, M13 9PL, UK
| | - R Krishna Kumar
- School of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, UK
| | - R V Gorbachev
- National Graphene Institute, University of Manchester, Manchester, M13 9PL, UK
| | - K Watanabe
- National Institute for Materials Science, Tsukuba, 305-0044, Japan
| | - T Taniguchi
- National Institute for Materials Science, Tsukuba, 305-0044, Japan
| | - I V Grigorieva
- School of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, UK
| | - V I Fal'ko
- School of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, UK.,National Graphene Institute, University of Manchester, Manchester, M13 9PL, UK
| | - M Polini
- School of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, UK. .,Dipartimento di Fisica dell'Università di Pisa, Largo Bruno Pontecorvo 3, 56127, Pisa, Italy. .,Istituto Italiano di Tecnologia, Graphene Labs, Via Morego 30, 16163, Genova, Italy.
| | - A K Geim
- School of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, UK. .,National Graphene Institute, University of Manchester, Manchester, M13 9PL, UK.
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10
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García-Ruiz A, Slizovskiy S, Mucha-Kruczyński M, Fal’ko VI. Spectroscopic Signatures of Electronic Excitations in Raman Scattering in Thin Films of Rhombohedral Graphite. Nano Lett 2019; 19:6152-6156. [PMID: 31361497 PMCID: PMC7007278 DOI: 10.1021/acs.nanolett.9b02196] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/29/2019] [Revised: 07/22/2019] [Indexed: 06/10/2023]
Abstract
Rhombohedral graphite features peculiar electronic properties, including persistence of low-energy surface bands of a topological nature. Here, we study the contribution of electron-hole excitations toward inelastic light scattering in thin films of rhombohedral graphite. We show that, in contrast to the featureless electron-hole contribution toward Raman spectrum of graphitic films with Bernal stacking, the inelastic light scattering accompanied by electron-hole excitations in crystals with rhombohedral stacking produces distinct features in the Raman signal which can be used both to identify the stacking and to determine the number of layers in the film.
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Affiliation(s)
- Aitor García-Ruiz
- Department
of Physics, University of Bath, Claverton Down, Bath BA2 3FL, United Kingdom
| | - Sergey Slizovskiy
- National
Graphene Institute, University of Manchester, Booth Street E, Manchester M13 9PL, United
Kingdom
- Department
of Physics and Astronomy, University of
Manchester, Oxford Road, Manchester M13 9PL, United Kingdom
| | - Marcin Mucha-Kruczyński
- Department
of Physics, University of Bath, Claverton Down, Bath BA2 3FL, United Kingdom
- Centre
for Nanoscience and Nanotechnology, University
of Bath, Claverton Down, Bath BA2 3FL, United Kingdom
| | - Vladimir I. Fal’ko
- National
Graphene Institute, University of Manchester, Booth Street E, Manchester M13 9PL, United
Kingdom
- Department
of Physics and Astronomy, University of
Manchester, Oxford Road, Manchester M13 9PL, United Kingdom
- Henry
Royce Institute, Manchester M13 9PL, United Kingdom
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11
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Rickhaus P, Wallbank J, Slizovskiy S, Pisoni R, Overweg H, Lee Y, Eich M, Liu MH, Watanabe K, Taniguchi T, Ihn T, Ensslin K. Transport Through a Network of Topological Channels in Twisted Bilayer Graphene. Nano Lett 2018; 18:6725-6730. [PMID: 30336041 DOI: 10.1021/acs.nanolett.8b02387] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We explore a network of electronic quantum valley Hall states in the moiré crystal of minimally twisted bilayer graphene. In our transport measurements, we observe Fabry-Pérot and Aharanov-Bohm oscillations that are robust in magnetic fields ranging from 0 to 8 T, which is in strong contrast to more conventional two-dimensional systems where trajectories in the bulk are bent by the Lorentz force. This persistence in magnetic field and the linear spacing in density indicate that charge carriers in the bulk flow in topologically protected, one-dimensional channels. With this work, we demonstrate coherent electronic transport in a lattice of topologically protected states.
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Affiliation(s)
- Peter Rickhaus
- Department of Physics , ETH Zürich , Otto-Stern-Weg 1 , 8093 Zürich , Switzerland
| | - John Wallbank
- Centre for Ecology and Hydrology , Maclean Building, Benson Lane , Crowmarsh Gifford, Wallingford, Oxfordshire , OX10 8BB , United Kingdom
| | | | - Riccardo Pisoni
- Department of Physics , ETH Zürich , Otto-Stern-Weg 1 , 8093 Zürich , Switzerland
| | - Hiske Overweg
- Department of Physics , ETH Zürich , Otto-Stern-Weg 1 , 8093 Zürich , Switzerland
| | - Yongjin Lee
- Department of Physics , ETH Zürich , Otto-Stern-Weg 1 , 8093 Zürich , Switzerland
| | - Marius Eich
- Department of Physics , ETH Zürich , Otto-Stern-Weg 1 , 8093 Zürich , Switzerland
| | - Ming-Hao Liu
- Department of Physics , National Cheng Kung University , Tainan 70101 , Taiwan
| | - 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
- Department of Physics , ETH Zürich , Otto-Stern-Weg 1 , 8093 Zürich , Switzerland
| | - Klaus Ensslin
- Department of Physics , ETH Zürich , Otto-Stern-Weg 1 , 8093 Zürich , Switzerland
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12
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Asshoff PU, Sambricio JL, Slizovskiy S, Rooney AP, Taniguchi T, Watanabe K, Haigh SJ, Fal'ko V, Grigorieva IV, Vera-Marun IJ. Magnetoresistance in Co-hBN-NiFe Tunnel Junctions Enhanced by Resonant Tunneling through Single Defects in Ultrathin hBN Barriers. Nano Lett 2018; 18:6954-6960. [PMID: 30372086 DOI: 10.1021/acs.nanolett.8b02866] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Hexagonal boron nitride (hBN) is a prototypical high-quality two-dimensional insulator and an ideal material to study tunneling phenomena, as it can be easily integrated in vertical van der Waals devices. For spintronic devices, its potential has been demonstrated both for efficient spin injection in lateral spin valves and as a barrier in magnetic tunnel junctions (MTJs). Here we reveal the effect of point defects inevitably present in mechanically exfoliated hBN on the tunnel magnetoresistance of Co-hBN-NiFe MTJs. We observe a clear enhancement of both the conductance and magnetoresistance of the junction at well-defined bias voltages, indicating resonant tunneling through magnetic (spin-polarized) defect states. The spin polarization of the defect states is attributed to exchange coupling of a paramagnetic impurity in the few-atomic-layer thick hBN to the ferromagnetic electrodes. This is confirmed by excellent agreement with theoretical modeling. Our findings should be taken into account in analyzing tunneling processes in hBN-based magnetic devices. More generally, our study shows the potential of using atomically thin hBN barriers with defects to engineer the magnetoresistance of MTJs and to achieve spin filtering, opening the door toward exploiting the spin degree of freedom in current studies of point defects as quantum emitters.
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Affiliation(s)
- Pablo U Asshoff
- School of Physics and Astronomy , University of Manchester , Oxford Road , Manchester M13 9PL , United Kingdom
- National Graphene Institute , University of Manchester , Manchester M13 9PL , United Kingdom
| | - Jose L Sambricio
- School of Physics and Astronomy , University of Manchester , Oxford Road , Manchester M13 9PL , United Kingdom
- National Graphene Institute , University of Manchester , Manchester M13 9PL , United Kingdom
| | - Sergey Slizovskiy
- School of Physics and Astronomy , University of Manchester , Oxford Road , Manchester M13 9PL , United Kingdom
- National Graphene Institute , University of Manchester , Manchester M13 9PL , United Kingdom
| | - Aidan P Rooney
- School of Materials , University of Manchester , Oxford Road , Manchester M13 9PL , United Kingdom
| | - 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
| | - Sarah J Haigh
- School of Materials , University of Manchester , Oxford Road , Manchester M13 9PL , United Kingdom
| | - Vladimir Fal'ko
- School of Physics and Astronomy , University of Manchester , Oxford Road , Manchester M13 9PL , United Kingdom
- National Graphene Institute , University of Manchester , Manchester M13 9PL , United Kingdom
| | - Irina V Grigorieva
- School of Physics and Astronomy , University of Manchester , Oxford Road , Manchester M13 9PL , United Kingdom
- National Graphene Institute , University of Manchester , Manchester M13 9PL , United Kingdom
| | - Ivan J Vera-Marun
- School of Physics and Astronomy , University of Manchester , Oxford Road , Manchester M13 9PL , United Kingdom
- National Graphene Institute , University of Manchester , Manchester M13 9PL , United Kingdom
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13
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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 Lett 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] [What about the content of this article? (0)] [Affiliation(s)] [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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14
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Slizovskiy S, Chubukov AV, Betouras JJ. Magnetic fluctuations and specific heat in Na(x)CoO2 near a Lifshitz transition. Phys Rev Lett 2015; 114:066403. [PMID: 25723233 DOI: 10.1103/physrevlett.114.066403] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2014] [Indexed: 06/04/2023]
Abstract
We analyze the temperature and doping dependence of the specific heat C(T) in Na(x)CoO(2). This material was conjectured to undergo a Lifshitz-type topological transition at x=x(c)=0.62, in which a new electron Fermi pocket emerges at the Γ point, in addition to the existing hole pocket with large k(F). The data show that near x=x(c), the temperature dependence of C(T)/T at low T gets stronger as x approaches x(c) from below and then reverses the trend and changes sign at x≥x(c). We argue that this behavior can be quantitatively explained within the spin-fluctuation theory. We show that magnetic fluctuations are enhanced near x(c) at momenta around k(F), and their dynamics changes between x≤x(c) and x>x(c), when the new pocket forms. We demonstrate that this explains the temperature dependence of C(T)/T. We show that at larger x (x>0.65) the system enters a magnetic quantum critical regime where C(T)/T roughly scales as logT. This behavior extends to progressively lower T as x increases towards a magnetic instability at x≈0.75.
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Affiliation(s)
- Sergey Slizovskiy
- Department of Physics, Loughborough University, Loughborough LE11 3TU, United Kingdom
| | - Andrey V Chubukov
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Joseph J Betouras
- Department of Physics, Loughborough University, Loughborough LE11 3TU, United Kingdom
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15
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Slizovskiy S. Charging of graphene by a magnetic field and the mechanical effect of magnetic oscillations. J Phys Condens Matter 2013; 25:496007. [PMID: 24195970 DOI: 10.1088/0953-8984/25/49/496007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We discuss the fact that the quantum capacitance of graphene-based devices leads to variation of graphene charge density under changes of external magnetic field. The charge is conserved, but redistributes to the substrate or other graphene sheets. We derive an exact analytic expression for charge redistribution in the case of ideal graphene in a strong magnetic field. When we account for impurities and temperature, the effect decreases and the formulas reduce to standard quantum capacitance expressions. The importance of quantum capacitance for potential Casimir force experiments is emphasized and the corresponding corrections are worked out.
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Affiliation(s)
- Sergey Slizovskiy
- Department of Physics, Loughborough University, Loughborough LE11 3TU, UK. Petersburg Nuclear Physics Institute, Russia
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16
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