1
|
Zheng Z, Shi Y, Zhou JJ, Prezhdo OV, Zheng Q, Zhao J. Ab initio real-time quantum dynamics of charge carriers in momentum space. NATURE COMPUTATIONAL SCIENCE 2023; 3:532-541. [PMID: 38177418 DOI: 10.1038/s43588-023-00456-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2022] [Accepted: 04/21/2023] [Indexed: 01/06/2024]
Abstract
Application of the non-adiabatic molecular dynamics (NAMD) approach is limited to studying carrier dynamics in the momentum space, as a supercell is required to sample the phonon excitation and electron-phonon (e-ph) interaction at different momenta in a molecular dynamics simulation. Here we develop an ab initio approach for the real-time charge carrier quantum dynamics in the momentum space (NAMD_k) by directly introducing e-ph coupling into the Hamiltonian based on the harmonic approximation. The NAMD_k approach maintains the zero-point energy and includes memory effects of carrier dynamics. The application of NAMD_k to the hot carrier dynamics in graphene reveals the phonon-specific relaxation mechanism. An energy threshold of 0.2 eV-defined by two optical phonon modes-separates the hot electron relaxation into fast and slow regions with lifetimes of pico- and nanoseconds, respectively. The NAMD_k approach provides an effective tool to understand real-time carrier dynamics in the momentum space for different materials.
Collapse
Affiliation(s)
- Zhenfa Zheng
- Department of Physics, ICQD/Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, China
| | - Yongliang Shi
- Department of Physics, ICQD/Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, China.
- Center for Spintonics and Quantum Systerms, State Key Laboratory for Mechanical Behavior of Materials, School of Materials Science and Engineering, Xi'an Jiaotong University, Xi'an, China.
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai, China.
| | - Jin-Jian Zhou
- School of Physics, Beijing Institute of Technology, Beijing, China
| | - Oleg V Prezhdo
- Departments of Chemistry, Physics, and Astronomy, University of Southern California, Los Angeles, CA, USA
| | - Qijing Zheng
- Department of Physics, ICQD/Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, China.
| | - Jin Zhao
- Department of Physics, ICQD/Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, China.
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA, USA.
- Hefei National Laboratory, University of Science and Technology of China, Hefei, China.
| |
Collapse
|
2
|
Rani C, Kandpal S, Ghosh T, Bansal L, Tanwar M, Kumar R. Energy dispersive anti-anharmonic effect in a Fano intervened semiconductor: revealed through temperature and wavelength-dependent Raman scattering. Phys Chem Chem Phys 2023; 25:1627-1631. [PMID: 36601877 DOI: 10.1039/d2cp04686e] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
It is always interesting to understand how the interplay between two perturbations, affects any physical process and gets manifested in a semiconductor. Temperature- and wavelength-dependent Raman Spectromicroscopy was performed on heavily-doped Si to reveal an unusual anti-anharmonic effect. Additionally, the energy dispersive behaviour of Fano coupling strength was also studied and its possible interrelation with the observed anti-anharmonic effect was explored. A systematic study revealed that at the different excitation wavelengths, the strength of the Fano interaction was different, where the involved electron-phonon (Fano-Fano-interferon) bound states were counted together with different energies. By understanding how the interplay manifests in terms of the Raman line shape, a method to calculate the Fano-interferon dissociation energy was developed. The slope of the Raman linewidth at different excitation wavelengths with temperature showed a negative temperature coefficient and sign reversal on decreasing the doping concentration. A wavelength-dependent empirical relation is proposed to calculate the required thermal energy, required to dissociate the electron-phonon bound state.
Collapse
Affiliation(s)
- Chanchal Rani
- Materials and Device Laboratory, Department of Physics, Indian Institute of Technology Indore, Simrol-453552, India.
| | - Suchita Kandpal
- Materials and Device Laboratory, Department of Physics, Indian Institute of Technology Indore, Simrol-453552, India.
| | - Tanushree Ghosh
- Materials and Device Laboratory, Department of Physics, Indian Institute of Technology Indore, Simrol-453552, India.
| | - Love Bansal
- Materials and Device Laboratory, Department of Physics, Indian Institute of Technology Indore, Simrol-453552, India.
| | - Manushree Tanwar
- Department of Chemistry, University of Pennsylvania, 231S, 34 Street, Philadelphia, PA 19104-6323, USA.
| | - Rajesh Kumar
- Materials and Device Laboratory, Department of Physics, Indian Institute of Technology Indore, Simrol-453552, India.
| |
Collapse
|
3
|
Gadelha AC, Nguyen VH, Neto EGS, Santana F, Raschke MB, Lamparski M, Meunier V, Charlier JC, Jorio A. Electron-Phonon Coupling in a Magic-Angle Twisted-Bilayer Graphene Device from Gate-Dependent Raman Spectroscopy and Atomistic Modeling. NANO LETTERS 2022; 22:6069-6074. [PMID: 35878122 DOI: 10.1021/acs.nanolett.2c00905] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
The importance of phonons in the strong correlation phenomena observed in twisted-bilayer graphene (TBG) at the so-called magic-angle is under debate. Here we apply gate-dependent micro-Raman spectroscopy to monitor the G band line width in TBG devices of twist angles θ = 0° (Bernal), ∼1.1° (magic-angle), and ∼7° (large-angle). The results show a broad and p-/n-asymmetric doping behavior at the magic angle, in clear contrast to the behavior observed in twist angles above and below this point. Atomistic modeling reproduces the experimental observations in close connection with the joint density of electronic states in the electron-phonon scattering process, revealing how the unique electronic structure of magic-angle TBGs influences the electron-phonon coupling and, consequently, the G band line width. Overall, the value of the G band line width in magic-angle TBG is larger when compared to that of the other samples, in qualitative agreement with our calculations.
Collapse
Affiliation(s)
- Andreij C Gadelha
- Physics Department, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais 31270-901, Brazil
- Department of Physics, and JILA, University of Colorado at Boulder, Boulder, Colorado 80309, United States
| | - Viet-Hung Nguyen
- Institute of Condensed Matter and Nanosciences, Université Catholique de Louvain (UCLouvain), Louvain-la-Neuve 1348, Belgium
| | - Eliel G S Neto
- Physics Institute, Universidade Federal da Bahia, Salvador, Bahia 40170-115 Brazil
| | - Fabiano Santana
- Physics Department, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais 31270-901, Brazil
| | - Markus B Raschke
- Department of Physics, and JILA, University of Colorado at Boulder, Boulder, Colorado 80309, United States
| | - Michael Lamparski
- Department of Physics, Applied Physics, and Astronomy, Jonsson Rowland Science Center, Troy, New York 12180-3590, United States
| | - Vincent Meunier
- Department of Physics, Applied Physics, and Astronomy, Jonsson Rowland Science Center, Troy, New York 12180-3590, United States
| | - Jean-Christophe Charlier
- Institute of Condensed Matter and Nanosciences, Université Catholique de Louvain (UCLouvain), Louvain-la-Neuve 1348, Belgium
| | - Ado Jorio
- Physics Department, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais 31270-901, Brazil
| |
Collapse
|
4
|
Rani C, Tanwar M, Ghosh T, Kandpal S, Pathak DK, Chaudhary A, Yogi P, Saxena SK, Kumar R. Raman Spectroscopy as a Simple yet Effective Analytical Tool for Determining Fermi Energy and Temperature Dependent Fermi Shift in Silicon. Anal Chem 2022; 94:1510-1514. [DOI: 10.1021/acs.analchem.1c03624] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Chanchal Rani
- Materials and Device Laboratory, Department of Physics, Indian Institute of Technology Indore, Simrol 453552, India
| | - Manushree Tanwar
- Materials and Device Laboratory, Department of Physics, Indian Institute of Technology Indore, Simrol 453552, India
| | - Tanushree Ghosh
- Materials and Device Laboratory, Department of Physics, Indian Institute of Technology Indore, Simrol 453552, India
| | - Suchita Kandpal
- Materials and Device Laboratory, Department of Physics, Indian Institute of Technology Indore, Simrol 453552, India
| | - Devesh K. Pathak
- Materials and Device Laboratory, Department of Physics, Indian Institute of Technology Indore, Simrol 453552, India
| | - Anjali Chaudhary
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Priyanka Yogi
- Institut für Festkörperphysik, Leibniz Universität Hannover, Appelstraße 2, 30167 Hannover, Germany
| | | | - Rajesh Kumar
- Materials and Device Laboratory, Department of Physics, Indian Institute of Technology Indore, Simrol 453552, India
- Centre for Indian Scientific Knowledge Systems, Indian Institute of Technology Indore, Simrol 453552, India
| |
Collapse
|
5
|
Rahman MZ, Maity P, Mohammed OF, Gascon J. Insight into the role of reduced graphene oxide for enhancing photocatalytic hydrogen evolution in disordered carbon nitride. Phys Chem Chem Phys 2022; 24:11213-11221. [DOI: 10.1039/d2cp00200k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Compared to crystalline carbon nitride, the performance of disordered carbon nitride (d-CN) as a hydrogen production photocatalyst is extremely poor. Owing to disordered atomic orientation, it is prone to numerous...
Collapse
|
6
|
Inoshita T, Saito S, Hosono H. Floating Interlayer and Surface Electrons in 2D Materials: Graphite, Electrides, and Electrenes. SMALL SCIENCE 2021. [DOI: 10.1002/smsc.202100020] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Affiliation(s)
- Takeshi Inoshita
- Materials Research Center for Element Strategy Tokyo Institute of Technology 4259 Nagatsuta Kanagawa 226-8503 Japan
- Research Center for Functional Materials National Institute for Materials Science Tsukuba Ibaraki 305‐0044 Japan
| | - Susumu Saito
- Department of Physics Tokyo Institute of Technology 2-12-1 Oh-okayama, Meguro-ku Tokyo 152-8551 Japan
| | - Hideo Hosono
- Materials Research Center for Element Strategy Tokyo Institute of Technology 4259 Nagatsuta Kanagawa 226-8503 Japan
- International Center for Materials Nanoarchitectonics National Institute for Materials Science Tsukuba Ibaraki 305‐0044 Japan
| |
Collapse
|
7
|
Benedek G, Manson JR, Miret-Artés S. The electron-phonon coupling constant for single-layer graphene on metal substrates determined from He atom scattering. Phys Chem Chem Phys 2021; 23:7575-7585. [PMID: 33180894 DOI: 10.1039/d0cp04729e] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Recent theory has demonstrated that the value of the electron-phonon coupling strength λ can be extracted directly from the thermal attenuation (Debye-Waller factor) of helium atom scattering reflectivity. This theory is here extended to multivalley semimetal systems and applied to the case of graphene on different metal substrates and graphite. It is shown that λ rapidly increases for decreasing graphene-substrate binding strength. Two different calculational models are considered which produce qualitatively similar results for the dependence of λ on binding strength. These models predict, respectively, values of λHAS = 0.89 and 0.32 for a hypothetical flat free-standing single-layer graphene with cyclic boundary conditions. The method is suitable for analysis and characterization of not only the graphene overlayers considered here, but also other layered systems such as twisted graphene bilayers.
Collapse
Affiliation(s)
- Giorgio Benedek
- Donostia International Physics Center (DIPC), Paseo Manuel de Lardizabal, 4, 20018 Donostia-San Sebastián, Spain
| | | | | |
Collapse
|
8
|
Rezania H, Azizi F. The effects of electron-phonon coupling and magnetic field on charge structure factors of armchair graphene nanoribbons. Chem Phys 2020. [DOI: 10.1016/j.chemphys.2019.110592] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
|
9
|
Yang Z, Bhowmick S, Sen FG, Banerji A, Alpas AT. Roles of sliding-induced defects and dissociated water molecules on low friction of graphene. Sci Rep 2018; 8:121. [PMID: 29317658 PMCID: PMC5760666 DOI: 10.1038/s41598-017-17971-1] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2017] [Accepted: 12/04/2017] [Indexed: 11/09/2022] Open
Abstract
Sliding contact experiments and first-principles calculations were performed to elucidate the roles of structural defects and water dissociative adsorption process on the tribo-chemical mechanisms responsible for low friction of graphene. Sliding friction tests conducted in ambient air and under a dry N2 atmosphere showed that in both cases a high running-in coefficient of friction (COF) occurred initially but a low steady-state COF was reached only when the sliding was continued in air with moisture. Density functional theory (DFT) calculations indicated that the energy barrier (E b ) for dissociative adsorption of H2O was significantly lower in case of reconstructed graphene with a monovacancy compared to pristine graphene. Cross-sectional transmission electron microscopy of graphene transferred to the counterface revealed a partly amorphous structure incorporating damaged graphene layers with d-spacings larger than that of the original layers. DFT calculations on the reconstructed bilayer AB graphene systems revealed an increase of d-spacing due to the chemisorption of H, O, and OH at the vacancy sites and a reduction in the interlayer binding energy (E B ) between the bilayer graphene interfaces compared to pristine graphene. Thus, sliding induced defects facilitated dissociative adsorption of water molecules and reduced COF of graphene for sliding tests under ambient and humid environments but not under an inert atmosphere.
Collapse
Affiliation(s)
- Zaixiu Yang
- Engineering Materials Program, Mechanical, Automotive and Materials Engineering Department, University of Windsor, Windsor, Ontario, N9B 3P4, Canada
| | - Sukanta Bhowmick
- Engineering Materials Program, Mechanical, Automotive and Materials Engineering Department, University of Windsor, Windsor, Ontario, N9B 3P4, Canada
| | - Fatih G Sen
- Center for Nanoscale Materials, Argonne National Laboratory, Cass Ave, Lemont, IL, 60439, USA
| | - Anindya Banerji
- Engineering Materials Program, Mechanical, Automotive and Materials Engineering Department, University of Windsor, Windsor, Ontario, N9B 3P4, Canada
| | - Ahmet T Alpas
- Engineering Materials Program, Mechanical, Automotive and Materials Engineering Department, University of Windsor, Windsor, Ontario, N9B 3P4, Canada.
| |
Collapse
|
10
|
Zhang X, Zhou Y, Cui B, Zhao M, Liu F. Theoretical Discovery of a Superconducting Two-Dimensional Metal-Organic Framework. NANO LETTERS 2017; 17:6166-6170. [PMID: 28898086 DOI: 10.1021/acs.nanolett.7b02795] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Superconductivity is a fascinating quantum phenomenon characterized by zero electrical resistance and the Meissner effect. To date, several distinct families of superconductors (SCs) have been discovered. These include three-dimensional (3D) bulk SCs in both inorganic and organic materials as well as two-dimensional (2D) thin film SCs but only in inorganic materials. Here we predict superconductivity in 2D and 3D organic metal-organic frameworks by using first-principles calculations. We show that the highly conductive and recently synthesized Cu-benzenehexathial (BHT) is a Bardeen-Cooper-Schrieffer SC. Remarkably, the monolayer Cu-BHT has a critical temperature (Tc) of 4.43 K, while Tc of bulk Cu-BHT is 1.58 K. Different from the enhanced Tc in 2D inorganic SCs which is induced by interfacial effects, the Tc enhancement in this 2D organic SC is revealed to be the out-of-plane soft-mode vibrations, analogous to surface mode enhancement originally proposed by Ginzburg. Our findings not only shed new light on better understanding 2D superconductivity but also open a new direction to search for SCs by interface engineering with organic materials.
Collapse
Affiliation(s)
- Xiaoming Zhang
- School of Physics and State Key Laboratory of Crystal Materials, Shandong University , Jinan, Shandong 250100, China
- Department of Materials Science and Engineering, University of Utah , Salt Lake City, Utah 84112, United States
- Institute for Advanced Study, Tsinghua University , Beijing 100084, China
| | - Yinong Zhou
- Department of Materials Science and Engineering, University of Utah , Salt Lake City, Utah 84112, United States
| | - Bin Cui
- School of Physics and State Key Laboratory of Crystal Materials, Shandong University , Jinan, Shandong 250100, China
- Department of Materials Science and Engineering, University of Utah , Salt Lake City, Utah 84112, United States
| | - Mingwen Zhao
- School of Physics and State Key Laboratory of Crystal Materials, Shandong University , Jinan, Shandong 250100, China
| | - Feng Liu
- Department of Materials Science and Engineering, University of Utah , Salt Lake City, Utah 84112, United States
- Collaborative Innovation Center of Quantum Matter , Beijing 100084, China
| |
Collapse
|
11
|
Shanmugam M, Kim K. Electrodeposited gold dendrites at reduced graphene oxide as an electrocatalyst for nitrite and glucose oxidation. J Electroanal Chem (Lausanne) 2016. [DOI: 10.1016/j.jelechem.2016.06.009] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
|
12
|
Gierz I, Cavalleri A. Electronic-structural dynamics in graphene. STRUCTURAL DYNAMICS (MELVILLE, N.Y.) 2016; 3:051301. [PMID: 27822486 PMCID: PMC5074990 DOI: 10.1063/1.4964777] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/09/2016] [Accepted: 09/30/2016] [Indexed: 06/06/2023]
Abstract
We review our recent time- and angle-resolved photoemission spectroscopy experiments, which measure the transient electronic structure of optically driven graphene. For pump photon energies in the near infrared ([Formula: see text]), we have discovered the formation of a population-inverted state near the Dirac point, which may be of interest for the design of THz lasing devices and optical amplifiers. At lower pump photon energies ([Formula: see text]), for which interband absorption is not possible in doped samples, we find evidence for free carrier absorption. In addition, when mid-infrared pulses are made resonant with an infrared-active in-plane phonon of bilayer graphene ([Formula: see text]), a transient enhancement of the electron-phonon coupling constant is observed, providing interesting perspective for experiments that report light-enhanced superconductivity in doped fullerites in which a similar lattice mode was excited. All the studies reviewed here have important implications for applications of graphene in optoelectronic devices and for the dynamical engineering of electronic properties with light.
Collapse
Affiliation(s)
- Isabella Gierz
- Center for Free Electron Laser Science, Max Planck Institute for the Structure and Dynamics of Matter , Hamburg, Germany
| | | |
Collapse
|
13
|
Jung SW, Shin WJ, Kim J, Moreschini L, Yeom HW, Rotenberg E, Bostwick A, Kim KS. Sublattice Interference as the Origin of σ Band Kinks in Graphene. PHYSICAL REVIEW LETTERS 2016; 116:186802. [PMID: 27203340 DOI: 10.1103/physrevlett.116.186802] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2015] [Indexed: 06/05/2023]
Abstract
Kinks near the Fermi level observed in angle-resolved photoemission spectroscopy (ARPES) have been widely accepted to represent electronic coupling to collective excitations, but kinks at higher energies have eluded a unified description. We identify the mechanism leading to such kink features by means of ARPES and tight-binding band calculations on σ bands of graphene, where anomalous kinks at energies as high as ∼4 eV were reported recently [Phys. Rev. Lett. 111, 216806 (2013)]. We found that two σ bands show a strong intensity modulation with abruptly vanishing intensity near the kink features, which is due to sublattice interference. The interference induced local singularity in the matrix element is a critical factor that gives rise to apparent kink features, as confirmed by our spectral simulations without involving any coupling to collective excitations.
Collapse
Affiliation(s)
- Sung Won Jung
- Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science, Pohang 37673, Korea
- Department of Physics, Pohang University of Science and Technology, Pohang 37673, Korea
| | - Woo Jong Shin
- Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science, Pohang 37673, Korea
- Department of Physics, Pohang University of Science and Technology, Pohang 37673, Korea
| | - Jimin Kim
- Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science, Pohang 37673, Korea
- Department of Physics, Pohang University of Science and Technology, Pohang 37673, Korea
| | - Luca Moreschini
- Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science, Pohang 37673, Korea
- Advanced Light Source, E. O. Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Han Woong Yeom
- Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science, Pohang 37673, Korea
- Department of Physics, Pohang University of Science and Technology, Pohang 37673, Korea
| | - Eli Rotenberg
- Advanced Light Source, E. O. Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Aaron Bostwick
- Advanced Light Source, E. O. Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Keun Su Kim
- Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science, Pohang 37673, Korea
- Department of Physics, Pohang University of Science and Technology, Pohang 37673, Korea
| |
Collapse
|
14
|
Margine ER, Lambert H, Giustino F. Electron-phonon interaction and pairing mechanism in superconducting Ca-intercalated bilayer graphene. Sci Rep 2016; 6:21414. [PMID: 26892805 PMCID: PMC4759825 DOI: 10.1038/srep21414] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2015] [Accepted: 01/12/2016] [Indexed: 11/21/2022] Open
Abstract
Using the ab initio anisotropic Eliashberg theory including Coulomb interactions, we investigate the electron-phonon interaction and the pairing mechanism in the recently-reported superconducting Ca-intercalated bilayer graphene. We find that C6CaC6 can support phonon-mediated superconductivity with a critical temperature Tc = 6.8-8.1 K, in good agreement with experimental data. Our calculations indicate that the low-energy Caxy vibrations are critical to the pairing, and that it should be possible to resolve two distinct superconducting gaps on the electron and hole Fermi surface pockets.
Collapse
Affiliation(s)
- E. R. Margine
- Department of Physics, Applied Physics and Astronomy, Binghamton University, State University of New York, PO Box 6000, Binghamton, New York 13902-6000, USA
| | - Henry Lambert
- Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, United Kingdom
| | - Feliciano Giustino
- Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, United Kingdom
| |
Collapse
|
15
|
Verdi C, Giustino F. Fröhlich Electron-Phonon Vertex from First Principles. PHYSICAL REVIEW LETTERS 2015; 115:176401. [PMID: 26551127 DOI: 10.1103/physrevlett.115.176401] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2015] [Indexed: 06/05/2023]
Abstract
We develop a method for calculating the electron-phonon vertex in polar semiconductors and insulators from first principles. The present formalism generalizes the Fröhlich vertex to the case of anisotropic materials and multiple phonon branches, and can be used either as a postprocessing correction to standard electron-phonon calculations, or in conjunction with ab initio interpolation based on maximally localized Wannier functions. We demonstrate this formalism by investigating the electron-phonon interactions in anatase TiO(2), and show that the polar vertex significantly reduces the electron lifetimes and enhances the anisotropy of the coupling. The present work enables ab initio calculations of carrier mobilities, lifetimes, mass enhancement, and pairing in polar materials.
Collapse
Affiliation(s)
- Carla Verdi
- Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, United Kingdom
| | - Feliciano Giustino
- Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, United Kingdom
| |
Collapse
|
16
|
Gierz I, Mitrano M, Petersen JC, Cacho C, Turcu ICE, Springate E, Stöhr A, Köhler A, Starke U, Cavalleri A. Population inversion in monolayer and bilayer graphene. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:164204. [PMID: 25835083 DOI: 10.1088/0953-8984/27/16/164204] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The recent demonstration of saturable absorption and negative optical conductivity in the Terahertz range in graphene has opened up new opportunities for optoelectronic applications based on this and other low dimensional materials. Recently, population inversion across the Dirac point has been observed directly by time- and angle-resolved photoemission spectroscopy (tr-ARPES), revealing a relaxation time of only ∼130 femtoseconds. This severely limits the applicability of single layer graphene to, for example, Terahertz light amplification. Here we use tr-ARPES to demonstrate long-lived population inversion in bilayer graphene. The effect is attributed to the small band gap found in this compound. We propose a microscopic model for these observations and speculate that an enhancement of both the pump photon energy and the pump fluence may further increase this lifetime.
Collapse
Affiliation(s)
- Isabella Gierz
- Max Planck Institute for the Structure and Dynamics of Matter, Luruper Chaussee 149 22761, Hamburg, Germany
| | | | | | | | | | | | | | | | | | | |
Collapse
|
17
|
Gierz I, Mitrano M, Bromberger H, Cacho C, Chapman R, Springate E, Link S, Starke U, Sachs B, Eckstein M, Wehling TO, Katsnelson MI, Lichtenstein A, Cavalleri A. Phonon-pump extreme-ultraviolet-photoemission probe in graphene: anomalous heating of Dirac carriers by lattice deformation. PHYSICAL REVIEW LETTERS 2015; 114:125503. [PMID: 25860758 DOI: 10.1103/physrevlett.114.125503] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2014] [Indexed: 06/04/2023]
Abstract
We modulate the atomic structure of bilayer graphene by driving its lattice at resonance with the in-plane E_{1u} lattice vibration at 6.3 μm. Using time- and angle-resolved photoemission spectroscopy (tr-ARPES) with extreme-ultraviolet (XUV) pulses, we measure the response of the Dirac electrons near the K point. We observe that lattice modulation causes anomalous carrier dynamics, with the Dirac electrons reaching lower peak temperatures and relaxing at faster rate compared to when the excitation is applied away from the phonon resonance or in monolayer samples. Frozen phonon calculations predict dramatic band structure changes when the E_{1u} vibration is driven, which we use to explain the anomalous dynamics observed in the experiment.
Collapse
Affiliation(s)
- Isabella Gierz
- Max Planck Institute for the Structure and Dynamics of Matter, Center for Free Electron Laser Science, 22761 Hamburg, Germany
| | - Matteo Mitrano
- Max Planck Institute for the Structure and Dynamics of Matter, Center for Free Electron Laser Science, 22761 Hamburg, Germany
| | - Hubertus Bromberger
- Max Planck Institute for the Structure and Dynamics of Matter, Center for Free Electron Laser Science, 22761 Hamburg, Germany
| | - Cephise Cacho
- Central Laser Facility, STFC Rutherford Appleton Laboratory, OX11 0QX Harwell, United Kingdom
| | - Richard Chapman
- Central Laser Facility, STFC Rutherford Appleton Laboratory, OX11 0QX Harwell, United Kingdom
| | - Emma Springate
- Central Laser Facility, STFC Rutherford Appleton Laboratory, OX11 0QX Harwell, United Kingdom
| | - Stefan Link
- Max Planck Institute for Solid State Research, 70569 Stuttgart, Germany
| | - Ulrich Starke
- Max Planck Institute for Solid State Research, 70569 Stuttgart, Germany
| | - Burkhard Sachs
- I. Institut für Theoretische Physik, Universität Hamburg, 20355 Hamburg, Germany
| | - Martin Eckstein
- Max Planck Institute for the Structure and Dynamics of Matter, Center for Free Electron Laser Science, 22761 Hamburg, Germany
| | - Tim O Wehling
- Institut für Theoretische Physik, Universität Bremen, 28359 Bremen, Germany
| | - Mikhail I Katsnelson
- Institute for Molecules and Materials, Radboud University Nijmegen, 6525 HP Nijmegen, Netherlands
| | | | - Andrea Cavalleri
- Max Planck Institute for the Structure and Dynamics of Matter, Center for Free Electron Laser Science, 22761 Hamburg, Germany
- Department of Physics, Clarendon Laboratory, University of Oxford, OX1 3PU Oxford, United Kingdom
| |
Collapse
|
18
|
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: 985] [Impact Index Per Article: 109.4] [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.
Collapse
Affiliation(s)
- Andrea C Ferrari
- Cambridge Graphene Centre, University of Cambridge, Cambridge, CB3 0FA, UK.
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
19
|
Zhang XL, Liu WM. Electron-phonon coupling and its implication for the superconducting topological insulators. Sci Rep 2015; 5:8964. [PMID: 25753813 PMCID: PMC4354041 DOI: 10.1038/srep08964] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2014] [Accepted: 02/10/2015] [Indexed: 12/02/2022] Open
Abstract
The recent observation of superconductivity in doped topological insulators has sparked a flurry of interest due to the prospect of realizing the long-sought topological superconductors. Yet the understanding of underlying pairing mechanism in these systems is far from complete. Here we investigate this problem by providing robust first-principles calculations of the role of electron-phonon coupling for the superconducting pairing in the prime candidate CuxBi2Se3. Our results show that electron-phonon scattering process in this system is dominated by zone center and boundary optical modes, with coexistence of phonon stiffening and softening. While the calculated electron-phonon coupling constant λ suggests that Tc from electron-phonon coupling is 2 orders smaller than the ones reported on bulk inhomogeneous samples, suggesting that superconductivity may not come from pure electron-phonon coupling. We discuss the possible enhancement of superconducting transition temperature by local inhomogeneity introduced by doping.
Collapse
Affiliation(s)
- Xiao-Long Zhang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Wu-Ming Liu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| |
Collapse
|
20
|
Davenport AR, Hague JP. Bias free gap creation in bilayer graphene. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2014; 26:225601. [PMID: 24824315 DOI: 10.1088/0953-8984/26/22/225601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
For graphene to be utilized in the digital electronics industry the challenge is to create bandgaps of order 1 eV as simply as possible. The most successful methods for the creation of gaps in graphene are (a) confining the electrons in nanoribbons, which is technically difficult or (b) placing a potential difference across bilayer graphene, which is limited to gaps of around 300 meV for reasonably sized electric fields. Here we propose that electronic band gaps can be created without applying an external electric field, by using the electron-phonon interaction formed when bilayer graphene is sandwiched between highly polarisable ionic materials. We derive and solve self-consistent equations, finding that a large gap can be formed for intermediate electron-phonon coupling. The gap originates from the amplification of an intrinsic Coulomb interaction due to the proximity of carbon atoms in neighbouring planes.
Collapse
Affiliation(s)
- A R Davenport
- Department of Physical Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK
| | | |
Collapse
|
21
|
Wang GS, Wu Y, Wei YZ, Zhang XJ, Li Y, Li LD, Wen B, Yin PG, Guo L, Cao MS. Fabrication of Reduced Graphene Oxide (RGO)/Co3O4Nanohybrid Particles and a RGO/Co3O4/Poly(vinylidene fluoride) Composite with Enhanced Wave-Absorption Properties. Chempluschem 2014; 79:375-381. [DOI: 10.1002/cplu.201300345] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2013] [Revised: 01/02/2014] [Indexed: 11/06/2022]
|
22
|
Cava CE, Persson C, Zarbin AJG, Roman LS. Resistive switching in iron-oxide-filled carbon nanotubes. NANOSCALE 2014; 6:378-384. [PMID: 24201829 DOI: 10.1039/c3nr04320g] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Iron-oxide-filled carbon nanotubes exhibit an intriguing charge bipolarization behavior which allows the material to be applied in resistive memory devices. Raman analysis conducted with an electric field applied in situ shows the Kohn anomalies and a strong modification of the electronic properties related to the applied voltage intensity. In addition, the I(D)/I(G) ratio indicated the reversibility of this process. The electrical characterization indicated an electronic transport governed by two main kinds of charge hopping, one between the filling and the nanotube and the other between the nanotube shells.
Collapse
Affiliation(s)
- Carlos E Cava
- Department of Materials Engineering, Universidade Tecnológica Federal do Paraná, CEP 86036-370, Londrina, PR, Brazil.
| | | | | | | |
Collapse
|
23
|
Probing Dirac Fermions in Graphene by Scanning Tunneling Microscopy and Spectroscopy. ACTA ACUST UNITED AC 2013. [DOI: 10.1007/978-3-319-02633-6_2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/20/2023]
|
24
|
Fischetti MV, Kim J, Narayanan S, Ong ZY, Sachs C, Ferry DK, Aboud SJ. Pseudopotential-based studies of electron transport in graphene and graphene nanoribbons. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2013; 25:473202. [PMID: 24135050 DOI: 10.1088/0953-8984/25/47/473202] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
The theoretical understanding of electron transport in graphene and graphene nanoribbons is reviewed, emphasizing the help provided by atomic pseudopotentials (self-consistent and empirical) in determining not only the band structure but also other fundamental transport parameters such as electron-phonon matrix elements and line-edge roughness scattering. Electron-phonon scattering in suspended graphene sheets, impurity and remote-phonon scattering in supported and gated graphene, electron-phonon and line-edge roughness scattering in armchair-edge nanoribbons are reviewed, keeping in mind the potential use of graphene in devices of the future very large scale integration technology.
Collapse
Affiliation(s)
- Massimo V Fischetti
- Department of Materials Science and Engineering, The University of Texas at Dallas, Richardson, TX 75080, USA
| | | | | | | | | | | | | |
Collapse
|
25
|
Odkhuu D, Shin D, Ruoff RS, Park N. Conversion of multilayer graphene into continuous ultrathin sp³-bonded carbon films on metal surfaces. Sci Rep 2013; 3:3276. [PMID: 24253851 PMCID: PMC3834869 DOI: 10.1038/srep03276] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2013] [Accepted: 11/04/2013] [Indexed: 11/09/2022] Open
Abstract
The conversion of multilayer graphenes into sp(3)-bonded carbon films on metal surfaces (through hydrogenation or fluorination of the outer surface of the top graphene layer) is indicated through first-principles computations. The main driving force for this conversion is the hybridization between sp(3) orbitals and metal surface dz(2) orbitals. The induced electronic gap states and spin moments in the carbon layers are confined in a region within 0.5 nm of the metal surface. Whether the conversion occurs depend on the fraction of hydrogenated (fluorinated) C atoms at the outer surface and on the number of stacked graphene layers. In the analysis of the Eliashberg spectral functions for the sp(3) carbon films on a metal surface that is diamagnetic, the strong covalent metal-sp(3) carbon bonds induce soft phonon modes that predominantly contribute to large electron-phonon couplings, suggesting the possibility of phonon-mediated superconductivity. Our computational results suggest a route to experimental realization of large-area ultrathin sp(3)-bonded carbon films on metal surfaces.
Collapse
Affiliation(s)
- Dorj Odkhuu
- Interdisciplinary School of Green Energy and Low Dimensional Carbon Materials Center, Ulsan 689-798, Korea
| | | | | | | |
Collapse
|
26
|
Unraveling the interlayer-related phonon self-energy renormalization in bilayer graphene. Sci Rep 2012; 2:1017. [PMID: 23264879 PMCID: PMC3527827 DOI: 10.1038/srep01017] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2012] [Accepted: 11/26/2012] [Indexed: 11/08/2022] Open
Abstract
In this letter, we present a step towards understanding the bilayer graphene (2LG) interlayer (IL)-related phonon combination modes and overtones as well as their phonon self-energy renormalizations by using both gate-modulated and laser-energy dependent inelastic scattering spectroscopy. We show that although the IL interactions are weak, their respective phonon renormalization response is significant. Particularly special, the IL interactions are mediated by Van der Waals forces and are fundamental for understanding low-energy phenomena such as transport and infrared optics. Our approach opens up a new route to understanding fundamental properties of IL interactions which can be extended to any graphene-like material, such as MoS2, WSe2, oxides and hydroxides. Furthermore, we report a previously elusive crossing between IL-related phonon combination modes in 2LG, which might have important technological applications.
Collapse
|
27
|
Araujo PT, Mafra DL, Sato K, Saito R, Kong J, Dresselhaus MS. Phonon self-energy corrections to nonzero wave-vector phonon modes in single-layer graphene. PHYSICAL REVIEW LETTERS 2012; 109:046801. [PMID: 23006101 DOI: 10.1103/physrevlett.109.046801] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2011] [Indexed: 06/01/2023]
Abstract
Phonon self-energy corrections have mostly been studied theoretically and experimentally for phonon modes with zone-center (q=0) wave vectors. Here, gate-modulated Raman scattering is used to study phonons of a single layer of graphene originating from a double-resonant Raman process with q≠0. The observed phonon renormalization effects are different from what is observed for the zone-center q=0 case. To explain our experimental findings, we explored the phonon self-energy for the phonons with nonzero wave vectors (q≠0) in single-layer graphene in which the frequencies and decay widths are expected to behave oppositely to the behavior observed in the corresponding zone-center q=0 processes. Within this framework, we resolve the identification of the phonon modes contributing to the G(⋆) Raman feature at 2450 cm(-1) to include the iTO+LA combination modes with q≠0 and also the 2iTO overtone modes with q=0, showing both to be associated with wave vectors near the high symmetry point K in the Brillouin zone.
Collapse
Affiliation(s)
- P T Araujo
- Department of Electrical Engineering and Computer Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139-4307, USA.
| | | | | | | | | | | |
Collapse
|
28
|
Hwang J, LeBlanc JPF, Carbotte JP. Optical self-energy in graphene due to correlations. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2012; 24:245601. [PMID: 22609689 DOI: 10.1088/0953-8984/24/24/245601] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
In highly correlated systems one can define an optical self-energy in analogy to its quasiparticle (QP) self-energy counterpart. This quantity provides useful information on the nature of the excitations involved in inelastic scattering processes. Here we calculate the self-energy of the intraband optical transitions in graphene originating in the electron-electron interaction (EEI) as well as electron-phonon interaction (EPI). Although optics involves an average over all momenta (k) of the charge carriers, the structure in the optical self-energy is nevertheless found to mirror mainly that of the corresponding quasiparticles for k equal to or near the Fermi momentum k(F). Consequently, plasmaronic structures which are associated with momenta near the Dirac point at k = 0 are not important in the intraband optical response. While the structure of the electron-phonon interaction (EPI) reflects the sharp peaks of the phonon density of states, the excitation spectrum associated with the electron-electron interaction is in comparison structureless and flat and extends over an energy range which scales linearly with the value of the chemical potential. We introduce a method whereby detailed quantitative information on such excitation spectra can be extracted from optical data. Modulations seen on the edge of the interband optical conductivity as it rises towards its universal background value are traced to structure in the quasiparticle self-energies around k(F) of the lower Dirac cone associated with the occupied states.
Collapse
Affiliation(s)
- J Hwang
- Department of Physics, Sungkyunkwan University, Suwon, Gyeonggi-do, Republic of Korea
| | | | | |
Collapse
|
29
|
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.
Collapse
Affiliation(s)
- Eva Y Andrei
- Department of Physics and Astronomy, Rutgers University, Piscataway, NJ 08855, USA
| | | | | |
Collapse
|
30
|
Late DJ, Maitra U, Panchakarla LS, Waghmare UV, Rao CNR. Temperature effects on the Raman spectra of graphenes: dependence on the number of layers and doping. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2011; 23:055303. [PMID: 21406907 DOI: 10.1088/0953-8984/23/5/055303] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Temperature effects on the various features in the Raman spectra of several graphene samples and graphene nanoribbons have been investigated over the temperature range 77-573 K. The temperature coefficient of the G and 2D band frequencies are found to depend on the number of layers, the former decreasing with the increase in the number of layers. The number of layers also affects the temperature coefficients of the FWHMs of these bands. Doping of graphene affects these Raman features significantly. The defect-related bands D and D(') bands are not sensitive to the number of layers or doping. We can understand the observed temperature effects on the basis of electron-phonon coupling, thermal expansion and anharmonic phonon-phonon interactions.
Collapse
Affiliation(s)
- Dattatray J Late
- Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur PO, Bangalore 560064, India
| | | | | | | | | |
Collapse
|
31
|
Kaloni TP, Cheng YC, Faccio R, Schwingenschlögl U. Oxidation of monovacancies in graphene by oxygen molecules. ACTA ACUST UNITED AC 2011. [DOI: 10.1039/c1jm12299a] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
32
|
Kaloni TP, Kahaly MU, Schwingenschlögl U. Induced magnetism in transition metal intercalated graphitic systems. ACTA ACUST UNITED AC 2011. [DOI: 10.1039/c1jm13527a] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
33
|
Savini G, Ferrari AC, Giustino F. First-principles prediction of doped graphane as a high-temperature electron-phonon superconductor. PHYSICAL REVIEW LETTERS 2010; 105:037002. [PMID: 20867792 DOI: 10.1103/physrevlett.105.037002] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2010] [Indexed: 05/29/2023]
Abstract
We predict by first-principles calculations that p-doped graphane is an electron-phonon superconductor with a critical temperature above the boiling point of liquid nitrogen. The unique strength of the chemical bonds between carbon atoms and the large density of electronic states at the Fermi energy arising from the reduced dimensionality give rise to a giant Kohn anomaly in the optical phonon dispersions and push the superconducting critical temperature above 90 K. As evidence of graphane was recently reported, and doping of related materials such as graphene, diamond, and carbon nanostructures is well established, superconducting graphane may be feasible.
Collapse
Affiliation(s)
- G Savini
- Department of Engineering, University of Cambridge, Cambridge, CB3 0FA, United Kingdom
| | | | | |
Collapse
|
34
|
Ferry DK, Huang L, Yang R, Lai YC, Akis R. Open quantum dots in graphene: Scaling relativistic pointer states. ACTA ACUST UNITED AC 2010. [DOI: 10.1088/1742-6596/220/1/012015] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
35
|
Essig S, Marquardt CW, Vijayaraghavan A, Ganzhorn M, Dehm S, Hennrich F, Ou F, Green AA, Sciascia C, Bonaccorso F, Bohnen KP, Löhneysen HV, Kappes MM, Ajayan PM, Hersam MC, Ferrari AC, Krupke R. Phonon-assisted electroluminescence from metallic carbon nanotubes and graphene. NANO LETTERS 2010; 10:1589-1594. [PMID: 20405819 DOI: 10.1021/nl9039795] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
We report on light emission from biased metallic single-wall carbon nanotube (SWNT), multiwall carbon nanotube (MWNT) and few-layer graphene (FLG) devices. SWNT devices were assembled from tubes with different diameters in the range 0.7-1.5 nm. They emit light in the visible spectrum with peaks at 1.4 and 1.8 eV. Similar peaks are observed for MWNT and FLG devices. We propose that this light emission is due to phonon-assisted radiative decay from populated pi* band states at the M point to the Fermi level at the K point. Since for most carbon nanotubes as well as for graphene the energy of unoccupied states at the M point is close to 1.6 eV, the observation of two emission peaks at approximately 1.6 +/- approximately 0.2 eV could indicate radiative decay under emission or absorption of optical phonons, respectively.
Collapse
Affiliation(s)
- S Essig
- Institut für Nanotechnologie, Karlsruhe Institute of Technology, Karlsruhe, Germany
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
36
|
Attaccalite C, Wirtz L, Lazzeri M, Mauri F, Rubio A. Doped graphene as tunable electron-phonon coupling material. NANO LETTERS 2010; 10:1172-1176. [PMID: 20222744 DOI: 10.1021/nl9034626] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
We present a new way to tune the electron-phonon coupling (EPC) in graphene by changing the deformation potential with electron/hole doping. We show the EPC for highest optical branch at the high symmetry point K acquires a strong dependency on the doping level due to electron-electron correlation not accounted in mean-field approaches. Such a dependency influences the dispersion (with respect to the laser energy) of the Raman D and 2D lines and the splitting of the 2D peak in multilayer graphene. Finally this doping dependence opens the possibility to construct tunable electronic devices through external control of the EPC.
Collapse
Affiliation(s)
- Claudio Attaccalite
- ETSF Scientific Development Centre, Departamento Fisica de Materiales, Universidad del Pais Vasco, San Sebastian, Spain.
| | | | | | | | | |
Collapse
|
37
|
Xu Y, Li X, Dong J. Infrared and Raman spectra of AA-stacking bilayer graphene. NANOTECHNOLOGY 2010; 21:065711. [PMID: 20061600 DOI: 10.1088/0957-4484/21/6/065711] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The infrared (IR) absorption and resonant Raman spectra of the undoped AA-stacking bilayer graphene have been calculated using density-functional theory in the local density approximation. It is found that the undoped AA-stacking bilayer graphene exhibits a different characteristic jump and peak structure in its IR spectra, and a different G-band peak structure in its resonant Raman spectra, compared with those of the AB-stacking one, which are caused by the different interlayer coupling effects, due to different stacking types in both of them. Based upon the different IR and Raman spectra, a powerful experimental method can be proposed to identify accurately the stacking type and the layer number in future experiments.
Collapse
Affiliation(s)
- Yuehua Xu
- Group of Computational Condensed Matter Physics, National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing, People's Republic of China
| | | | | |
Collapse
|
38
|
Rao C, Sood A, Subrahmanyam K, Govindaraj A. Graphen, das neue zweidimensionale Nanomaterial. Angew Chem Int Ed Engl 2009. [DOI: 10.1002/ange.200901678] [Citation(s) in RCA: 196] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
|
39
|
Rao CNR, Sood AK, Subrahmanyam KS, Govindaraj A. Graphene: the new two-dimensional nanomaterial. Angew Chem Int Ed Engl 2009; 48:7752-77. [PMID: 19784976 DOI: 10.1002/anie.200901678] [Citation(s) in RCA: 1929] [Impact Index Per Article: 128.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Every few years, a new material with unique properties emerges and fascinates the scientific community, typical recent examples being high-temperature superconductors and carbon nanotubes. Graphene is the latest sensation with unusual properties, such as half-integer quantum Hall effect and ballistic electron transport. This two-dimensional material which is the parent of all graphitic carbon forms is strictly expected to comprise a single layer, but there is considerable interest in investigating two-layer and few-layer graphenes as well. Synthesis and characterization of graphenes pose challenges, but there has been considerable progress in the last year or so. Herein, we present the status of graphene research which includes aspects related to synthesis, characterization, structure, and properties.
Collapse
Affiliation(s)
- C N R Rao
- New Chemistry Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur P. O., Bangalore 560 064, India.
| | | | | | | |
Collapse
|
40
|
Kim KS, Yeom HW. Giant kink in electron dispersion of strongly coupled lead nanowires. NANO LETTERS 2009; 9:1916-1920. [PMID: 19331422 DOI: 10.1021/nl900052s] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Our photoelectron spectroscopy study shows a giant kink in the electron dispersion, a sign of high-energy manybody interactions of electrons, in a well-ordered Pb nanowire array self-assembled on a silicon substrate. We show that the unique electronic band structure due to the strong lateral coupling and the atomic structure of the nanowires drives an enhanced manybody interaction for kinked electron dispersion. The major giant kink mechanisms discussed previously, the magnetic and plasmonic excitations, are not relevant in the present system, supporting the recent kink theory based purely on electron-electron correlation. This suggests that tailored electronic band structures in nano array systems can provide unprecedented ways to study manybody interactions of electrons.
Collapse
Affiliation(s)
- Keun Su Kim
- Institute of Physics and Applied Physics and Center for Atomic Wires and Layers, Yonsei University, Seoul 120-749, Korea
| | | |
Collapse
|
41
|
Park CH, Giustino F, Spataru CD, Cohen ML, Louie SG. First-principles study of electron linewidths in graphene. PHYSICAL REVIEW LETTERS 2009; 102:076803. [PMID: 19257705 DOI: 10.1103/physrevlett.102.076803] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/24/2008] [Indexed: 05/27/2023]
Abstract
We present first-principles calculations of the linewidths of low-energy quasiparticles in n-doped graphene arising from both the electron-electron and the electron-phonon interactions. The contribution to the electron linewidth arising from the electron-electron interactions varies significantly with wave vector at fixed energy; in contrast, the electron-phonon contribution is virtually wave vector independent. These two contributions are comparable in magnitude at a binding energy of approximately 0.2 eV, corresponding to the optical phonon energy. The calculated linewidths, with both electron-electron and electron-phonon interactions included, explain to a large extent the linewidths seen in recent photoemission experiments.
Collapse
Affiliation(s)
- Cheol-Hwan Park
- Department of Physics, University of California at Berkeley, Berkeley, California 94720, USA
| | | | | | | | | |
Collapse
|