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Jones AJH, Gammelgaard L, Sauer MO, Biswas D, Koch RJ, Jozwiak C, Rotenberg E, Bostwick A, Watanabe K, Taniguchi T, Dean CR, Jauho AP, Bøggild P, Pedersen TG, Jessen BS, Ulstrup S. Nanoscale View of Engineered Massive Dirac Quasiparticles in Lithographic Superstructures. ACS NANO 2022; 16:19354-19362. [PMID: 36321616 DOI: 10.1021/acsnano.2c08929] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Massive Dirac fermions are low-energy electronic excitations characterized by a hyperbolic band dispersion. They play a central role in several emerging physical phenomena such as topological phase transitions, anomalous Hall effects, and superconductivity. This work demonstrates that massive Dirac fermions can be controllably induced by lithographically patterning superstructures of nanoscale holes in a graphene device. Their band dispersion is systematically visualized using angle-resolved photoemission spectroscopy with nanoscale spatial resolution. A linear scaling of effective mass with feature sizes is reported, underlining the Dirac nature of the superstructures. In situ electrostatic doping dramatically enhances the effective hole mass and leads to the direct observation of an electronic band gap that results in a peak-to-peak band separation of 0.64 ± 0.03 eV, which is shown via first-principles calculations to be strongly renormalized by carrier-induced screening. The methodology demonstrates band structure engineering guided by directly viewing structurally and electrically tunable massive Dirac quasiparticles in lithographic superstructures at the nanoscale.
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Affiliation(s)
- Alfred J H Jones
- Department of Physics and Astronomy, Aarhus University, 8000Aarhus C, Denmark
| | - Lene Gammelgaard
- DTU Physics, Technical University of Denmark, 2800Kgs. Lyngby, Denmark
- Center for Nanostructured Graphene, Technical University of Denmark, 2800Kgs. Lyngby, Denmark
| | - Mikkel O Sauer
- Department of Materials and Production, Aalborg University, 9220Aalborg Øst, Denmark
- Department of Mathematical Science, Aalborg University, 9220Aalborg Øst, Denmark
- Center for Nanostructured Graphene (CNG), 9220Aalborg Øst, Denmark
| | - Deepnarayan Biswas
- Department of Physics and Astronomy, Aarhus University, 8000Aarhus C, Denmark
| | - Roland J Koch
- Advanced Light Source, E. O. Lawrence Berkeley National Laboratory, Berkeley, California94720, United States
| | - Chris Jozwiak
- Advanced Light Source, E. O. Lawrence Berkeley National Laboratory, Berkeley, California94720, United States
| | - Eli Rotenberg
- Advanced Light Source, E. O. Lawrence Berkeley National Laboratory, Berkeley, California94720, United States
| | - Aaron Bostwick
- Advanced Light Source, E. O. Lawrence Berkeley National Laboratory, Berkeley, California94720, United States
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba305-0044, Japan
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba305-0044, Japan
| | - Cory R Dean
- Department of Physics, Columbia University, New York, New York10027, United States
| | - Antti-Pekka Jauho
- DTU Physics, Technical University of Denmark, 2800Kgs. Lyngby, Denmark
- Center for Nanostructured Graphene, Technical University of Denmark, 2800Kgs. Lyngby, Denmark
| | - Peter Bøggild
- DTU Physics, Technical University of Denmark, 2800Kgs. Lyngby, Denmark
- Center for Nanostructured Graphene, Technical University of Denmark, 2800Kgs. Lyngby, Denmark
| | - Thomas G Pedersen
- Department of Materials and Production, Aalborg University, 9220Aalborg Øst, Denmark
- Center for Nanostructured Graphene (CNG), 9220Aalborg Øst, Denmark
| | - Bjarke S Jessen
- Department of Physics, Columbia University, New York, New York10027, United States
| | - Søren Ulstrup
- Department of Physics and Astronomy, Aarhus University, 8000Aarhus C, Denmark
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2
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Heber M, Wind N, Kutnyakhov D, Pressacco F, Arion T, Roth F, Eberhardt W, Rossnagel K. Multispectral time-resolved energy-momentum microscopy using high-harmonic extreme ultraviolet radiation. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2022; 93:083905. [PMID: 36050085 DOI: 10.1063/5.0091003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2022] [Accepted: 07/18/2022] [Indexed: 06/15/2023]
Abstract
A 790-nm-driven high-harmonic generation source with a repetition rate of 6 kHz is combined with a toroidal-grating monochromator and a high-detection-efficiency photoelectron time-of-flight momentum microscope to enable time- and momentum-resolved photoemission spectroscopy over a spectral range of 23.6-45.5 eV with sub-100 fs time resolution. Three-dimensional (3D) Fermi surface mapping is demonstrated on graphene-covered Ir(111) with energy and momentum resolutions of ≲100 meV and ≲0.1 Å-1, respectively. The tabletop experiment sets the stage for measuring the kz-dependent ultrafast dynamics of 3D electronic structure, including band structure, Fermi surface, and carrier dynamics in 3D materials as well as 3D orbital dynamics in molecular layers.
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Affiliation(s)
- Michael Heber
- Deutsches Elektronen-Synchrotron DESY, 22607 Hamburg, Germany
| | - Nils Wind
- Institut für Experimental Physik, Universität Hamburg, 22761 Hamburg, Germany
| | | | | | - Tiberiu Arion
- Centre for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron DESY, 22607 Hamburg, Germany
| | - Friedrich Roth
- Institute of Experimental Physics, TU Bergakademie Freiberg, 09599 Freiberg, Germany
| | - Wolfgang Eberhardt
- Centre for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron DESY, 22607 Hamburg, Germany
| | - Kai Rossnagel
- Ruprecht Haensel Laboratory, Deutsches Elektronen-Synchrotron DESY, 22607 Hamburg, Germany
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3
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Bao C, Li Q, Xu S, Zhou S, Zeng XY, Zhong H, Gao Q, Luo L, Sun D, Xia TL, Zhou S. Population Inversion and Dirac Fermion Cooling in 3D Dirac Semimetal Cd 3As 2. NANO LETTERS 2022; 22:1138-1144. [PMID: 35050626 DOI: 10.1021/acs.nanolett.1c04250] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Revealing the ultrafast dynamics of three-dimensional (3D) Dirac fermions is critical for both fundamental science and device applications. So far, how the cooling of 3D Dirac fermions differs from that of two-dimensional (2D) and whether there is population inversion are fundamental questions to be answered. Here we reveal the ultrafast dynamics of Dirac fermions in a model 3D Dirac semimetal Cd3As2 by time- and angle-resolved photoemission spectroscopy with a tunable probe photon energy. The energy- and momentum-resolved relaxation rate shows a linear dependence on the energy, suggesting Dirac fermion cooling through intraband relaxation. Moreover, a population inversion is reported based on the observation of accumulated photoexcited carriers in the conduction band with a lifetime of 3.0 ps. Our work provides direct experimental evidence for a long-lived population inversion in a 3D Dirac semimetal, which is in contrast to 2D graphene with a much shorter lifetime.
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Affiliation(s)
- Changhua Bao
- State Key Laboratory of Low-Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing 100084, P. R. China
| | - Qian Li
- State Key Laboratory of Low-Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing 100084, P. R. China
| | - Sheng Xu
- Department of Physics and Beijing Key Laboratory of Opto-electronic Functional Materials and Micro-nano Devices, Renmin University of China, Beijing 100872, P. R. China
| | - Shaohua Zhou
- State Key Laboratory of Low-Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing 100084, P. R. China
| | - Xiang-Yu Zeng
- Department of Physics and Beijing Key Laboratory of Opto-electronic Functional Materials and Micro-nano Devices, Renmin University of China, Beijing 100872, P. R. China
| | - Haoyuan Zhong
- State Key Laboratory of Low-Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing 100084, P. R. China
| | - Qixuan Gao
- State Key Laboratory of Low-Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing 100084, P. R. China
| | - Laipeng Luo
- State Key Laboratory of Low-Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing 100084, P. R. China
| | - Dong Sun
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, P. R. China
| | - Tian-Long Xia
- Department of Physics and Beijing Key Laboratory of Opto-electronic Functional Materials and Micro-nano Devices, Renmin University of China, Beijing 100872, P. R. China
| | - Shuyun Zhou
- State Key Laboratory of Low-Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing 100084, P. R. China
- Frontier Science Center for Quantum Information, Beijing 100084, P. R. China
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Pressacco F, Uhlíř V, Gatti M, Nicolaou A, Bendounan A, Arregi JA, Patel SKK, Fullerton EE, Krizmancic D, Sirotti F. Laser induced phase transition in epitaxial FeRh layers studied by pump-probe valence band photoemission. STRUCTURAL DYNAMICS (MELVILLE, N.Y.) 2018; 5:034501. [PMID: 29888296 PMCID: PMC5966309 DOI: 10.1063/1.5027809] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/06/2018] [Accepted: 04/27/2018] [Indexed: 06/08/2023]
Abstract
We use time-resolved X-ray photoelectron spectroscopy to probe the electronic and magnetization dynamics in FeRh films after ultrafast laser excitations. We present experimental and theoretical results which investigate the electronic structure of FeRh during the first-order phase transition, identifying a clear signature of the magnetic phase. We find that a spin polarized feature at the Fermi edge is a fingerprint of the magnetic status of the system that is independent of the long-range ferromagnetic alignment of the magnetic domains. We use this feature to follow the phase transition induced by a laser pulse in a pump-probe experiment and find that the magnetic transition occurs in less than 50 ps and reaches its maximum in 100 ps.
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Affiliation(s)
| | | | | | - Alessandro Nicolaou
- Synchrotron SOLEIL, Saint-Aubin, BP 48, F-91192 Gif-sur-Yvette Cedex, France
| | - Azzedine Bendounan
- Synchrotron SOLEIL, Saint-Aubin, BP 48, F-91192 Gif-sur-Yvette Cedex, France
| | - Jon Ander Arregi
- CEITEC BUT, Brno University of Technology, Purkyňova 123, 612 00 Brno, Czech Republic
| | - Sheena K K Patel
- Center for Memory and Recording Research, University of California, San Diego, La Jolla, California 92093-0401, USA
| | - Eric E Fullerton
- Center for Memory and Recording Research, University of California, San Diego, La Jolla, California 92093-0401, USA
| | - Damjan Krizmancic
- Instituto Officina dei Materiali (IOM)-CNR, Laboratorio TASC, in Area Science Park S.S.14, Km 163.5, I34149 Trieste, Italy
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5
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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.
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Affiliation(s)
- Isabella Gierz
- Center for Free Electron Laser Science, Max Planck Institute for the Structure and Dynamics of Matter , Hamburg, Germany
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6
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Gierz I, Calegari F, Aeschlimann S, Chávez Cervantes M, Cacho C, Chapman RT, Springate E, Link S, Starke U, Ast CR, Cavalleri A. Tracking Primary Thermalization Events in Graphene with Photoemission at Extreme Time Scales. PHYSICAL REVIEW LETTERS 2015; 115:086803. [PMID: 26340199 DOI: 10.1103/physrevlett.115.086803] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2015] [Indexed: 05/13/2023]
Abstract
Direct and inverse Auger scattering are amongst the primary processes that mediate the thermalization of hot carriers in semiconductors. These two processes involve the annihilation or generation of an electron-hole pair by exchanging energy with a third carrier, which is either accelerated or decelerated. Inverse Auger scattering is generally suppressed, as the decelerated carriers must have excess energies higher than the band gap itself. In graphene, which is gapless, inverse Auger scattering is, instead, predicted to be dominant at the earliest time delays. Here, <8 fs extreme-ultraviolet pulses are used to detect this imbalance, tracking both the number of excited electrons and their kinetic energy with time-and angle-resolved photoemission spectroscopy. Over a time window of approximately 25 fs after absorption of the pump pulse, we observe an increase in conduction band carrier density and a simultaneous decrease of the average carrier kinetic energy, revealing that relaxation is in fact dominated by inverse Auger scattering. Measurements of carrier scattering at extreme time scales by photoemission will serve as a guide to ultrafast control of electronic properties in solids for petahertz electronics.
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Affiliation(s)
- I Gierz
- Max Planck Institute for the Structure and Dynamics of Matter, Center for Free Electron Laser Science, 22761 Hamburg, Germany
| | - F Calegari
- Max Planck Institute for the Structure and Dynamics of Matter, Center for Free Electron Laser Science, 22761 Hamburg, Germany
- Institute for Photonics and Nanotechnologies, IFN-CNR, 20133 Milano, Italy
| | - S Aeschlimann
- Max Planck Institute for the Structure and Dynamics of Matter, Center for Free Electron Laser Science, 22761 Hamburg, Germany
| | - M Chávez Cervantes
- Max Planck Institute for the Structure and Dynamics of Matter, Center for Free Electron Laser Science, 22761 Hamburg, Germany
| | - C Cacho
- Central Laser Facility, STFC Rutherford Appleton Laboratory, OX11 0QX Harwell, United Kingdom
| | - R T Chapman
- Central Laser Facility, STFC Rutherford Appleton Laboratory, OX11 0QX Harwell, United Kingdom
| | - E Springate
- Central Laser Facility, STFC Rutherford Appleton Laboratory, OX11 0QX Harwell, United Kingdom
| | - S Link
- Max Planck Institute for Solid State Research, 70569 Stuttgart, Germany
| | - U Starke
- Max Planck Institute for Solid State Research, 70569 Stuttgart, Germany
| | - C R Ast
- Max Planck Institute for Solid State Research, 70569 Stuttgart, Germany
| | - A 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
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7
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Ulstrup S, Johannsen JC, Crepaldi A, Cilento F, Zacchigna M, Cacho C, Chapman RT, Springate E, Fromm F, Raidel C, Seyller T, Parmigiani F, Grioni M, Hofmann P. Ultrafast electron dynamics in epitaxial graphene investigated with time- and angle-resolved photoemission spectroscopy. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:164206. [PMID: 25835249 DOI: 10.1088/0953-8984/27/16/164206] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
In order to exploit the intriguing optical properties of graphene it is essential to gain a better understanding of the light-matter interaction in the material on ultrashort timescales. Exciting the Dirac fermions with intense ultrafast laser pulses triggers a series of processes involving interactions between electrons, phonons and impurities. Here we study these interactions in epitaxial graphene supported on silicon carbide (semiconducting) and iridium (metallic) substrates using ultrafast time- and angle-resolved photoemission spectroscopy (TR-ARPES) based on high harmonic generation. For the semiconducting substrate we reveal a complex hot carrier dynamics that manifests itself in an elevated electronic temperature and an increase in linewidth of the π band. By analyzing these effects we are able to disentangle electron relaxation channels in graphene. On the metal substrate this hot carrier dynamics is found to be severely perturbed by the presence of the metal, and we find that the electronic system is much harder to heat up than on the semiconductor due to screening of the laser field by the metal.
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Affiliation(s)
- Søren Ulstrup
- Department of Physics and Astronomy, Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Nordre Ringgade 1, 8000 Aarhus C, Denmark
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8
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Johannsen JC, Ulstrup S, Crepaldi A, Cilento F, Zacchigna M, Miwa JA, Cacho C, Chapman RT, Springate E, Fromm F, Raidel C, Seyller T, King PDC, Parmigiani F, Grioni M, Hofmann P. Tunable carrier multiplication and cooling in graphene. NANO LETTERS 2015; 15:326-331. [PMID: 25458168 DOI: 10.1021/nl503614v] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Time- and angle-resolved photoemission measurements on two doped graphene samples displaying different doping levels reveal remarkable differences in the ultrafast dynamics of the hot carriers in the Dirac cone. In the more strongly (n-)doped graphene, we observe larger carrier multiplication factors (>3) and a significantly faster phonon-mediated cooling of the carriers back to equilibrium compared to in the less (p-)doped graphene. These results suggest that a careful tuning of the doping level allows for an effective manipulation of graphene's dynamical response to a photoexcitation.
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Affiliation(s)
- Jens Christian Johannsen
- Institute of Condensed Matter Physics, École Polytechnique Fédérale de Lausanne (EPFL) , 1015 Lausanne, Switzerland
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9
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Ulstrup S, Johannsen JC, Cilento F, Miwa JA, Crepaldi A, Zacchigna M, Cacho C, Chapman R, Springate E, Mammadov S, Fromm F, Raidel C, Seyller T, Parmigiani F, Grioni M, King PDC, Hofmann P. Ultrafast dynamics of massive dirac fermions in bilayer graphene. PHYSICAL REVIEW LETTERS 2014; 112:257401. [PMID: 25014829 DOI: 10.1103/physrevlett.112.257401] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2014] [Indexed: 06/03/2023]
Abstract
Bilayer graphene is a highly promising material for electronic and optoelectronic applications since it is supporting massive Dirac fermions with a tunable band gap. However, no consistent picture of the gap's effect on the optical and transport behavior has emerged so far, and it has been proposed that the insulating nature of the gap could be compromised by unavoidable structural defects, by topological in-gap states, or that the electronic structure could be altogether changed by many-body effects. Here, we directly follow the excited carriers in bilayer graphene on a femtosecond time scale, using ultrafast time- and angle-resolved photoemission. We find a behavior consistent with a single-particle band gap. Compared to monolayer graphene, the existence of this band gap leads to an increased carrier lifetime in the minimum of the lowest conduction band. This is in sharp contrast to the second substate of the conduction band, in which the excited electrons decay through fast, phonon-assisted interband transitions.
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Affiliation(s)
- Søren Ulstrup
- Department of Physics and Astronomy, Interdisciplinary Nanoscience Center (iNANO), Aarhus University, 8000 Aarhus C, Denmark
| | - Jens Christian Johannsen
- Institute of Condensed Matter Physics, École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | | | - Jill A Miwa
- Department of Physics and Astronomy, Interdisciplinary Nanoscience Center (iNANO), Aarhus University, 8000 Aarhus C, Denmark
| | | | | | - Cephise Cacho
- Central Laser Facility, STFC Rutherford Appleton Laboratory, Didcot OX11 0QX, United Kingdom
| | - Richard Chapman
- Central Laser Facility, STFC Rutherford Appleton Laboratory, Didcot OX11 0QX, United Kingdom
| | - Emma Springate
- Central Laser Facility, STFC Rutherford Appleton Laboratory, Didcot OX11 0QX, United Kingdom
| | - Samir Mammadov
- Institut für Physik, Technische Universität Chemnitz, 09126 Chemnitz, Germany
| | - Felix Fromm
- Institut für Physik, Technische Universität Chemnitz, 09126 Chemnitz, Germany
| | - Christian Raidel
- Institut für Physik, Technische Universität Chemnitz, 09126 Chemnitz, Germany
| | - Thomas Seyller
- Institut für Physik, Technische Universität Chemnitz, 09126 Chemnitz, Germany
| | - Fulvio Parmigiani
- Sincrotrone Trieste, 34149 Trieste, Italy and Department of Physics, University of Trieste, 34127 Trieste, Italy
| | - Marco Grioni
- Institute of Condensed Matter Physics, École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Phil D C King
- SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews, Fife KY16 9SS, United Kingdom
| | - Philip Hofmann
- Department of Physics and Astronomy, Interdisciplinary Nanoscience Center (iNANO), Aarhus University, 8000 Aarhus C, Denmark
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