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Li Y, Shang X, Zhou YH, Zheng X. The effect of light-irradiated area on the spin dependent photocurrent in zigzag graphene nanoribbon junctions. Phys Chem Chem Phys 2023; 25:24428-24435. [PMID: 37655683 DOI: 10.1039/d3cp01176c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/02/2023]
Abstract
In this work, we study the photogalvanic effect of a zigzag graphene nanoribbon junction with a centro-symmetrical structure which consists of 8 zigzag chains by density functional calculations. Specifically, we focus on the cases where the irradiated region is just part of the central region and located at different positions, with an aim to see how the spin dependent photocurrents will change and whether pure spin current can be obtained. It is found that the magnitude of the spin-dependent photocurrents increases with a gradual increase of the irradiated region and pure spin current is achieved when and only when the entire central region is irradiated. In addition, we studied the additive effect in this device to see that if we divide the central region into two parts, whether the sum of the spin current generated by irradiating the two parts individually is equal to that produced when the entire central region is irradiated. It is found that the sum of the spin currents produced by irradiating the two parts individually is smaller than that obtained by irradiating the whole central region, which means that the rule of "1 + 2 = 3" does not hold and the coupling effect between the two parts is important in photocurrent generation.
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Affiliation(s)
- Yuejun Li
- College of Science, East China Jiao Tong University, Nanchang 330013, China.
- College of Information Science and Technology, Nanjing Forestry University, Nanjing 210037, China.
| | - Xiaofei Shang
- College of Science, East China Jiao Tong University, Nanchang 330013, China.
| | - Yan-Hong Zhou
- College of Science, East China Jiao Tong University, Nanchang 330013, China.
| | - Xiaohong Zheng
- College of Information Science and Technology, Nanjing Forestry University, Nanjing 210037, China.
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2
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Najafi MN. Interaction-disorder-driven characteristic momentum in graphene, approach of multi-body distribution functions. Sci Rep 2019; 9:3624. [PMID: 30842596 PMCID: PMC6403372 DOI: 10.1038/s41598-019-39254-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2018] [Accepted: 01/17/2019] [Indexed: 11/25/2022] Open
Abstract
Multi-point probability measures along with the dielectric function of Dirac Fermions in mono-layer graphene containing particle-particle and white-noise (out-plane) disorder interactions on an equal footing in the Thomas-Fermi-Dirac approximation is investigated. By calculating the one-body carrier density probability measure of the graphene sheet, we show that the density fluctuation (ζ-1) is related to the disorder strength (ni), the interaction parameter (rs) and the average density ([Formula: see text]) via the relation [Formula: see text] for which [Formula: see text] leads to strong density inhomogeneities, i.e. electron-hole puddles (EHPs), in agreement with the previous works. The general equation governing the two-body distribution probability is obtained and analyzed. We present the analytical solution for some limits which is used for calculating density-density response function. We show that the resulting function shows power-law behaviors in terms of ζ with fractional exponents which are reported. The disorder-averaged polarization operator is shown to be a decreasing function of momentum like ordinary 2D parabolic band systems. It is seen that a disorder-driven momentum qch emerges in the system which controls the behaviors of the screened potential. We show that in small densities an instability occurs in which imaginary part of the dielectric function becomes negative and the screened potential changes sign. Corresponding to this instability, some oscillations in charge density along with a screening-anti-screening transition are observed. These effects become dominant in very low densities, strong disorders and strong interactions, the state in which EHPs appear. The total charge probability measure is another quantity which has been investigated in this paper. The resulting equation is analytically solved for large carrier densities, which admits the calculation of arbitrary-point correlation function.
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Affiliation(s)
- M N Najafi
- Department of Physics, University of Mohaghegh Ardabili, P.O. Box 179, Ardabil, Iran.
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3
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Najafi MN, Ahadpour N, Cheraghalizadeh J, Dashti-Naserabadi H. Scaling properties of monolayer graphene away from the Dirac point. Phys Rev E 2018; 98:012111. [PMID: 30110865 DOI: 10.1103/physreve.98.012111] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2018] [Indexed: 06/08/2023]
Abstract
The statistical properties of the carrier density profile of graphene in the ground state in the presence of particle-particle interaction and random charged impurity in zero gate voltage has been recently obtained by Najafi et al. [Phys. Rev. E 95, 032112 (2017)2470-004510.1103/PhysRevE.95.032112]. The nonzero chemical potential (μ) in gated graphene has nontrivial effects on electron-hole puddles, since it generates mass in the Dirac action and destroys the scaling behaviors of the effective Thomas-Fermi-Dirac theory. We provide detailed analysis on the resulting spatially inhomogeneous system in the framework of the Thomas-Fermi-Dirac theory for the Gaussian (white noise) disorder potential. We show that the chemical potential in this system as a random surface destroys the self-similarity, and also the charge field is non-Gaussian. We find that the two-body correlation functions are factorized to two terms: a pure function of the chemical potential and a pure function of the distance. The spatial dependence of these correlation functions is double logarithmic, e.g., the two-point density correlation behaves like D_{2}(r,μ)∝μ^{2}exp[-(-a_{D}lnlnr^{β_{D}})^{α_{D}}] (α_{D}=1.82, β_{D}=0.263, and a_{D}=0.955). The Fourier power spectrum function also behaves like ln[S(q)]=-β_{S}^{-a_{S}}(lnq)^{a_{S}}+2lnμ (a_{S}=3.0±0.1 and β_{S}=2.08±0.03) in contrast to the ordinary Gaussian rough surfaces for which a_{S}=1 and β_{S}=1/2(1+α)^{-1} (α being the roughness exponent). The geometrical properties are, however, similar to the ungated (μ=0) case, with the exponents that are reported in the text.
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Affiliation(s)
- M N Najafi
- Department of Physics, University of Mohaghegh Ardabili, P.O. Box 179, Ardabil, Iran
| | - N Ahadpour
- Department of Physics, University of Mohaghegh Ardabili, P.O. Box 179, Ardabil, Iran
| | - J Cheraghalizadeh
- Department of Physics, University of Mohaghegh Ardabili, P.O. Box 179, Ardabil, Iran
| | - H Dashti-Naserabadi
- School of Physics, Korea Institute for Advanced Study, Seoul 130-722, South Korea
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4
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Lucas A, Fong KC. Hydrodynamics of electrons in graphene. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:053001. [PMID: 29251624 DOI: 10.1088/1361-648x/aaa274] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Generic interacting many-body quantum systems are believed to behave as classical fluids on long time and length scales. Due to rapid progress in growing exceptionally pure crystals, we are now able to experimentally observe this collective motion of electrons in solid-state systems, including graphene. We present a review of recent progress in understanding the hydrodynamic limit of electronic motion in graphene, written for physicists from diverse communities. We begin by discussing the 'phase diagram' of graphene, and the inevitable presence of impurities and phonons in experimental systems. We derive hydrodynamics, both from a phenomenological perspective and using kinetic theory. We then describe how hydrodynamic electron flow is visible in electronic transport measurements. Although we focus on graphene in this review, the broader framework naturally generalizes to other materials. We assume only basic knowledge of condensed matter physics, and no prior knowledge of hydrodynamics.
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Affiliation(s)
- Andrew Lucas
- Department of Physics, Stanford University, Stanford, CA 94305, United States of America
| | - Kin Chung Fong
- Raytheon BBN Technologies, Quantum Information Processing Group, Cambridge, MA 02138, United States of America
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5
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Ryu H, Hwang J, Wang D, Disa AS, Denlinger J, Zhang Y, Mo SK, Hwang C, Lanzara A. Temperature-Dependent Electron-Electron Interaction in Graphene on SrTiO 3. NANO LETTERS 2017; 17:5914-5918. [PMID: 28906124 DOI: 10.1021/acs.nanolett.7b01650] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The electron band structure of graphene on SrTiO3 substrate has been investigated as a function of temperature. The high-resolution angle-resolved photoemission study reveals that the spectral width at Fermi energy and the Fermi velocity of graphene on SrTiO3 are comparable to those of graphene on a BN substrate. Near the charge neutrality, the energy-momentum dispersion of graphene exhibits a strong deviation from the well-known linearity, which is magnified as temperature decreases. Such modification resembles the characteristics of enhanced electron-electron interaction. Our results not only suggest that SrTiO3 can be a plausible candidate as a substrate material for applications in graphene-based electronics but also provide a possible route toward the realization of a new type of strongly correlated electron phases in the prototypical two-dimensional system via the manipulation of temperature and a proper choice of dielectric substrates.
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Affiliation(s)
- Hyejin Ryu
- Advanced Light Source, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States
- Max Planck-POSTECH/Hsinchu Center for Complex Phase Materials. Max Plank POSTECH/Korea Research Initiative (MPK) , Gyeongbuk 37673, South Korea
| | - Jinwoong Hwang
- Department of Physics, Pusan National University , Busan 46241, South Korea
| | - Debin Wang
- The Molecular Foundry, Lawrence Berkley National Laboratory , Berkeley, California 94720, United States
| | - Ankit S Disa
- Department of Applied Physics and Center for Interface Structures and Phenomena, Yale University , New Haven, Connecticut 06520, United States
| | - Jonathan Denlinger
- Advanced Light Source, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States
| | - Yuegang Zhang
- The Molecular Foundry, Lawrence Berkley National Laboratory , Berkeley, California 94720, United States
- Physics Department, Tsinghua University , Beijing 1000864, China
| | - Sung-Kwan Mo
- Advanced Light Source, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States
| | - Choongyu Hwang
- Department of Physics, Pusan National University , Busan 46241, South Korea
| | - Alessandra Lanzara
- Materials Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States
- Department of Physics, University of California , Berkeley, California 94720, United States
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Lundeberg MB, Gao Y, Asgari R, Tan C, Van Duppen B, Autore M, Alonso-González P, Woessner A, Watanabe K, Taniguchi T, Hillenbrand R, Hone J, Polini M, Koppens FHL. Tuning quantum nonlocal effects in graphene plasmonics. Science 2017; 357:187-191. [PMID: 28596312 DOI: 10.1126/science.aan2735] [Citation(s) in RCA: 221] [Impact Index Per Article: 31.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2017] [Accepted: 05/25/2017] [Indexed: 01/18/2023]
Abstract
The response of electron systems to electrodynamic fields that change rapidly in space is endowed by unique features, including an exquisite spatial nonlocality. This can reveal much about the materials' electronic structure that is invisible in standard probes that use gradually varying fields. Here, we use graphene plasmons, propagating at extremely slow velocities close to the electron Fermi velocity, to probe the nonlocal response of the graphene electron liquid. The near-field imaging experiments reveal a parameter-free match with the full quantum description of the massless Dirac electron gas, which involves three types of nonlocal quantum effects: single-particle velocity matching, interaction-enhanced Fermi velocity, and interaction-reduced compressibility. Our experimental approach can determine the full spatiotemporal response of an electron system.
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Affiliation(s)
- Mark B Lundeberg
- ICFO-Institut de Cinècies Fotòniques, The Barcelona Institute of Science and Technology, 08860 Castelldefels (Barcelona), Spain
| | - Yuanda Gao
- Department of Mechanical Engineering, Columbia University, New York, NY 10027, USA
| | - Reza Asgari
- School of Physics, Institute for Research in Fundamental Sciences (IPM), 19395-5531, Tehran, Iran.,School of Nano Science, Institute for Research in Fundamental Sciences (IPM), 19395-5531, Tehran
| | - Cheng Tan
- Department of Mechanical Engineering, Columbia University, New York, NY 10027, USA
| | - Ben Van Duppen
- Department of Physics, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp, Belgium
| | - Marta Autore
- CIC nanoGUNE, E-20018, Donostia-San Sebastián, Spain
| | - Pablo Alonso-González
- CIC nanoGUNE, E-20018, Donostia-San Sebastián, Spain.,Departamento de Física, Universidad de Oviedo, Oviedo 33007, Spain
| | - Achim Woessner
- ICFO-Institut de Cinècies Fotòniques, The Barcelona Institute of Science and Technology, 08860 Castelldefels (Barcelona), Spain
| | - Kenji Watanabe
- National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Rainer Hillenbrand
- CIC nanoGUNE and EHU/UPV, E-20018, Donostia-San Sebastián, Spain.,IKERBASQUE, Basque Foundation for Science, 48011 Bilbao, Spain
| | - James Hone
- Department of Mechanical Engineering, Columbia University, New York, NY 10027, USA
| | - Marco Polini
- Istituto Italiano di Tecnologia, Graphene Labs, Via Morego 30, I-16163 Genova, Italy.
| | - Frank H L Koppens
- ICFO-Institut de Cinècies Fotòniques, The Barcelona Institute of Science and Technology, 08860 Castelldefels (Barcelona), Spain. .,ICREA-Institució Catalana de Recerça i Estudis Avancats, 08010 Barcelona, Spain
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7
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Najafi MN, Nezhadhaghighi MG. Scale-invariant puddles in graphene: Geometric properties of electron-hole distribution at the Dirac point. Phys Rev E 2017; 95:032112. [PMID: 28415230 DOI: 10.1103/physreve.95.032112] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2016] [Indexed: 06/07/2023]
Abstract
We characterize the carrier density profile of the ground state of graphene in the presence of particle-particle interaction and random charged impurity in zero gate voltage. We provide detailed analysis on the resulting spatially inhomogeneous electron gas, taking into account the particle-particle interaction and the remote Coulomb disorder on an equal footing within the Thomas-Fermi-Dirac theory. We present some general features of the carrier density probability measure of the graphene sheet. We also show that, when viewed as a random surface, the electron-hole puddles at zero chemical potential show peculiar self-similar statistical properties. Although the disorder potential is chosen to be Gaussian, we show that the charge field is non-Gaussian with unusual Kondev relations, which can be regarded as a new class of two-dimensional random-field surfaces. Using Schramm-Loewner (SLE) evolution, we numerically demonstrate that the ungated graphene has conformal invariance and the random zero-charge density contours are SLE_{κ} with κ=1.8±0.2, consistent with c=-3 conformal field theory.
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Affiliation(s)
- M N Najafi
- Department of Physics, University of Mohaghegh Ardabili, P. O. Box 179, Ardabil, Iran
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8
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Liu B, Akis R, Ferry DK, Bohra G, Somphonsane R, Ramamoorthy H, Bird JP. Conductance fluctuations in graphene in the presence of long-range disorder. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2016; 28:135302. [PMID: 26941061 DOI: 10.1088/0953-8984/28/13/135302] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The fluctuations in the conductance of graphene that arise from a long-range disorder potential induced by random impurities are investigated with an atomic tight-binding lattice. The screened impurities lead to a slow variation of the background potential and this varies the overall potential landscape as the Fermi energy or an applied magnetic field is varied. As a result, the phase interference varies randomly and leads to fluctuations in the conductance. Recently, experiments have shown that an applied magnetic field produces a remarkable reduction in the amplitude of these conductance fluctuations. We find qualitative agreement with these experiments, and it appears that the reduction in magnetic field of the fluctuations arises from a field induced smoothing of the conductance landscape.
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Affiliation(s)
- Bobo Liu
- School of Electrical, Computer, and Energy Engineering, Arizona State University, Tempe, AZ 85287, USA
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9
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Ferrari AC, Bonaccorso F, Fal'ko V, Novoselov KS, Roche S, Bøggild P, Borini S, Koppens FHL, Palermo V, Pugno N, Garrido JA, Sordan R, Bianco A, Ballerini L, Prato M, Lidorikis E, Kivioja J, Marinelli C, Ryhänen T, Morpurgo A, Coleman JN, Nicolosi V, Colombo L, Fert A, Garcia-Hernandez M, Bachtold A, Schneider GF, Guinea F, Dekker C, Barbone M, Sun Z, Galiotis C, Grigorenko AN, Konstantatos G, Kis A, Katsnelson M, Vandersypen L, Loiseau A, Morandi V, Neumaier D, Treossi E, Pellegrini V, Polini M, Tredicucci A, Williams GM, Hong BH, Ahn JH, Kim JM, Zirath H, van Wees BJ, van der Zant H, Occhipinti L, Di Matteo A, Kinloch IA, Seyller T, Quesnel E, Feng X, Teo K, Rupesinghe N, Hakonen P, Neil SRT, Tannock Q, Löfwander T, Kinaret J. Science and technology roadmap for graphene, related two-dimensional crystals, and hybrid systems. NANOSCALE 2015; 7:4598-810. [PMID: 25707682 DOI: 10.1039/c4nr01600a] [Citation(s) in RCA: 991] [Impact Index Per Article: 110.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
We present the science and technology roadmap for graphene, related two-dimensional crystals, and hybrid systems, targeting an evolution in technology, that might lead to impacts and benefits reaching into most areas of society. This roadmap was developed within the framework of the European Graphene Flagship and outlines the main targets and research areas as best understood at the start of this ambitious project. We provide an overview of the key aspects of graphene and related materials (GRMs), ranging from fundamental research challenges to a variety of applications in a large number of sectors, highlighting the steps necessary to take GRMs from a state of raw potential to a point where they might revolutionize multiple industries. We also define an extensive list of acronyms in an effort to standardize the nomenclature in this emerging field.
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Affiliation(s)
- Andrea C Ferrari
- Cambridge Graphene Centre, University of Cambridge, Cambridge, CB3 0FA, UK.
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10
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Negative quantum capacitance induced by midgap states in single-layer graphene. Sci Rep 2014; 3:2041. [PMID: 23784258 PMCID: PMC3687226 DOI: 10.1038/srep02041] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2013] [Accepted: 05/28/2013] [Indexed: 11/24/2022] Open
Abstract
We demonstrate that single-layer graphene (SLG) decorated with a high density of Ag adatoms displays the unconventional phenomenon of negative quantum capacitance. The Ag adatoms act as resonant impurities and form nearly dispersionless resonant impurity bands near the charge neutrality point (CNP). Resonant impurities quench the kinetic energy and drive the electrons to the Coulomb energy dominated regime with negative compressibility. In the absence of a magnetic field, negative quantum capacitance is observed near the CNP. In the quantum Hall regime, negative quantum capacitance behavior at several Landau level positions is displayed, which is associated with the quenching of kinetic energy by the formation of Landau levels. The negative quantum capacitance effect near the CNP is further enhanced in the presence of Landau levels due to the magnetic-field-enhanced Coulomb interactions.
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Räsänen E, Rozzi CA, Pittalis S, Vignale G. Electron-electron interactions in artificial graphene. PHYSICAL REVIEW LETTERS 2012; 108:246803. [PMID: 23004308 DOI: 10.1103/physrevlett.108.246803] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2012] [Indexed: 06/01/2023]
Abstract
Recent advances in the creation and modulation of graphenelike systems are introducing a science of "designer Dirac materials". In its original definition, artificial graphene is a man-made nanostructure that consists of identical potential wells (quantum dots) arranged in an adjustable honeycomb lattice in the two-dimensional electron gas. As our ability to control the quality of artificial graphene samples improves, so grows the need for an accurate theory of its electronic properties, including the effects of electron-electron interactions. Here we determine those effects on the band structure and on the emergence of Dirac points.
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Affiliation(s)
- E Räsänen
- Nanoscience Center, Department of Physics, University of Jyväskylä, FI-40014 Jyväskylä, Finland.
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12
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Andrei EY, Li G, Du X. Electronic properties of graphene: a perspective from scanning tunneling microscopy and magnetotransport. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2012; 75:056501. [PMID: 22790587 DOI: 10.1088/0034-4885/75/5/056501] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
This review covers recent experimental progress in probing the electronic properties of graphene and how they are influenced by various substrates, by the presence of a magnetic field and by the proximity to a superconductor. The focus is on results obtained using scanning tunneling microscopy, spectroscopy, transport and magnetotransport techniques.
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Affiliation(s)
- Eva Y Andrei
- Department of Physics and Astronomy, Rutgers University, Piscataway, NJ 08855, USA
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13
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Trushin M, Schliemann J. Pseudospin in optical and transport properties of graphene. PHYSICAL REVIEW LETTERS 2011; 107:156801. [PMID: 22107311 DOI: 10.1103/physrevlett.107.156801] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/03/2011] [Indexed: 05/31/2023]
Abstract
We show that the pseudospin, being an additional degree of freedom for carriers in graphene, can be efficiently controlled by means of the electron-electron interactions which, in turn, can be manipulated by changing the substrate. In particular, an out-of-plane pseudospin component can occur leading to a zero-field Hall current as well as to polarization-sensitive interband optical absorption.
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Affiliation(s)
- Maxim Trushin
- Institute for Theoretical Physics, University of Regensburg, D-93040 Regensburg, Germany
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14
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Jiang Y, Qi Q, Wang R, Zhang J, Xue Q, Wang C, Jiang C, Qiu X. Direct observation and measurement of mobile charge carriers in a monolayer organic semiconductor on a dielectric substrate. ACS NANO 2011; 5:6195-6201. [PMID: 21740011 DOI: 10.1021/nn200760r] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We report the electrical characterization of a single layer of an organic semiconductor grown on a dielectric surface. The dynamic response of the charge carriers in the monolayer film of pentacene was characterized through the electrostatic interactions between an electric force microscope (EFM) probe and pentacene islands of various sizes. These islands were formed in situ by segmenting a coalesced pentacene monolayer into separated regions. The size-dependent dielectric responses of the pentacene islands suggest that mobile charges exist in the organic monolayer. Local capacitance spectroscopy revealed that the charge carriers in the p-type pentacene monolayer could be depleted at high bias voltages, enabling a further determination of the charge-carrier concentration in the organic semiconductor ultrathin film.
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Affiliation(s)
- Yeping Jiang
- National Center for Nanoscience and Technology, Beijing 100190, China
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15
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Reed JP, Uchoa B, Joe YI, Gan Y, Casa D, Fradkin E, Abbamonte P. The Effective Fine-Structure Constant of Freestanding Graphene Measured in Graphite. Science 2010; 330:805-8. [DOI: 10.1126/science.1190920] [Citation(s) in RCA: 103] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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16
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Maciel IO, Anderson N, Pimenta MA, Hartschuh A, Qian H, Terrones M, Terrones H, Campos-Delgado J, Rao AM, Novotny L, Jorio A. Electron and phonon renormalization near charged defects in carbon nanotubes. NATURE MATERIALS 2008; 7:878-83. [PMID: 18931672 DOI: 10.1038/nmat2296] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2008] [Accepted: 09/19/2008] [Indexed: 05/23/2023]
Abstract
Owing to their influence on electrons and phonons, defects can significantly alter electrical conductance, and optical, mechanical and thermal properties of a material. Thus, understanding and control of defects, including dopants in low-dimensional systems, hold great promise for engineered materials and nanoscale devices. Here, we characterize experimentally the effects of a single defect on electrons and phonons in single-wall carbon nanotubes. The effects demonstrated here are unusual in that they are not caused by defect-induced symmetry breaking. Electrons and phonons are strongly coupled in sp(2) carbon systems, and a defect causes renormalization of electron and phonon energies. We find that near a negatively charged defect, the electron velocity is increased, which in turn influences lattice vibrations locally. Combining measurements on nanotube ensembles and on single nanotubes, we capture the relation between atomic response and the readily accessible macroscopic behaviour.
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Affiliation(s)
- Indhira O Maciel
- Departamento de Física, Universidade Federal de Minas Gerais, Belo Horizonte, MG, 30123-970, Brazil
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17
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Rossi E, Das Sarma S. Ground state of graphene in the presence of random charged impurities. PHYSICAL REVIEW LETTERS 2008; 101:166803. [PMID: 18999700 DOI: 10.1103/physrevlett.101.166803] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2008] [Indexed: 05/27/2023]
Abstract
We calculate the carrier-density-dependent ground-state properties of graphene in the presence of random charged impurities in the substrate taking into account disorder and interaction effects nonperturbatively on an equal footing in a self-consistent theoretical formalism. We provide detailed quantitative results on the dependence of the disorder-induced spatially inhomogeneous two-dimensional carrier density distribution on the external gate bias, the impurity density, and the impurity location. We find that the interplay between disorder and interaction is strong, particularly at lower impurity densities. We show that, for the currently available typical graphene samples, inhomogeneity dominates graphene physics at low (< or approximately 10(12) cm(-2)) carrier density with the density fluctuations becoming larger than the average density.
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Affiliation(s)
- Enrico Rossi
- Condensed Matter Theory Center, Department of Physics, University of Maryland, College Park, MD 20742, USA
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