References of "Reichardt, Sven 50008600"
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See detailImpact of many-body effects on Landau levels in graphene
Sonntag, Jens; Reichardt, Sven UL; Wirtz, Ludger UL et al

in Physical Review Letters (2018), 120(18), 187701

We present magneto-Raman spectroscopy measurements on suspended graphene to investigate the charge carrier density-dependent electron-electron interaction in the presence of Landau levels. Utilizing gate ... [more ▼]

We present magneto-Raman spectroscopy measurements on suspended graphene to investigate the charge carrier density-dependent electron-electron interaction in the presence of Landau levels. Utilizing gate-tunable magnetophonon resonances, we extract the charge carrier density dependence of the Landau level transition energies and the associated effective Fermi velocity vF. In contrast to the logarithmic divergence of vF at zero magnetic field, we find a piecewise linear scaling of vF as a function of the charge carrier density, due to a magnetic-field-induced suppression of the long-range Coulomb interaction. We quantitatively confirm our experimental findings by performing tight-binding calculations on the level of the Hartree-Fock approximation, which also allow us to estimate an excitonic binding energy of ≈6  meV contained in the experimentally extracted Landau level transitions energies. [less ▲]

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See detailMany-Body Perturbation Theory Approach to Raman Spectroscopy and Its Application to 2D Materials
Reichardt, Sven UL

Doctoral thesis (2018)

Raman spectroscopy has become one of the most important techniques for the characterization of materials, as it allows the simultaneous probing of several properties, such as electronic and vibrational ... [more ▼]

Raman spectroscopy has become one of the most important techniques for the characterization of materials, as it allows the simultaneous probing of several properties, such as electronic and vibrational excitations, at once. This versatility, however, makes its theoretical description very challenging and, up to now, no fully satisfactory and general way for the calculation of Raman spectra from first principles exists. In this thesis, we aim to fill this gap and present a coherent theory of Raman scattering within the framework of many-body perturbation theory. We develop a novel and general, correlation function-based approach for the calculation of Raman scattering rates that can potentially also be applied to ultra-fast Raman spectroscopy out of equilibrium. Besides these theoretical developments, we present concrete computational recipes for the calculation of Raman intensities that allow the inclusion of both excitonic effects and non-adiabatic effects of lattice vibrations. The latter has so far not been possible with state-of-the-art methods, which can only take into account one of the two effects. As a first test case, we apply our theory to graphene, for which we use it to study the laser frequency and Fermi energy dependence of the Raman G-peak intensity. The flexibility of our approach also allows us to demonstrate that non-resonant processes and quantum mechanical interference effects play a significant role in Raman scattering. This applies not only to graphene but also to other two-dimensional materials of current interest, such as MoTe2 and MoS2. In addition to the development of a consistent and comprehensive description of Raman scattering, we derive a novel approach for the calculation of phonon frequencies and the screened electron-phonon coupling. It can be applied also to strongly correlated systems, for which the currently used methods are not entirely satisfactory or insufficient. Our new method goes beyond the limitations of the methods currently in use and will permit the computation of phonon-related quantities also in systems with strong correlation effects such as Kohn anomalies (e.g., graphene) or Peierls instabilities. Lastly, we present work on the application of (magneto-)Raman spectroscopy as a probe for many-body effects in graphene. Here we focus on the description of the phenomenon of magneto-phonon resonances and how it can be used to probe electronic excitation energies and to extract electron and phonon lifetimes. [less ▲]

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See detailTailoring mechanically tunable strain fields in graphene
Goldsche, Matthias; Sonntag, Jens; Khodkov, Tymofiy et al

in Nano Letters (2018), 18(3), 1707--1713

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See detailAb initio calculation of the G peak intensity of graphene: Laser-energy and Fermi-energy dependence and importance of quantum interference effects
Reichardt, Sven UL; Wirtz, Ludger UL

in Physical Review B (2017), 95(19), 195422

We present the results of a diagrammatic, fully ab initio calculation of the G peak intensity of graphene. The flexibility and generality of our approach enables us to go beyond the previous analytical ... [more ▼]

We present the results of a diagrammatic, fully ab initio calculation of the G peak intensity of graphene. The flexibility and generality of our approach enables us to go beyond the previous analytical calculations in the low-energy regime. We study the laser and Fermi energy dependence of the G peak intensity and analyze the contributions from resonant and nonresonant electronic transitions. In particular, we explicitly demonstrate the importance of quantum interference and nonresonant states for the G peak process. Our method of analysis and computational concept is completely general and can easily be applied to study other materials as well. [less ▲]

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See detailQuantum Interference Effects in Resonant Raman Spectroscopy of Single- and Triple-Layer MoTe2 from First-Principles
Pereira Coutada Miranda, Henrique UL; Reichardt, Sven UL; Froehlicher, Guillaume et al

in Nano Letters (2017), 17(4), 2381--2388

We present a combined experimental and theoretical study of resonant Raman spectroscopy in single- and triple-layer MoTe2. Raman intensities are computed entirely from first-principles by calculating ... [more ▼]

We present a combined experimental and theoretical study of resonant Raman spectroscopy in single- and triple-layer MoTe2. Raman intensities are computed entirely from first-principles by calculating finite differences of the dielectric susceptibility. In our analysis, we investigate the role of quantum interference effects and the electron−phonon coupling. With this method, we explain the experimentally observed intensity inversion of the A′1 vibrational modes in triple-layer MoTe2 with increasing laser photon energy. Finally, we show that a quantitative comparison with experimental data requires the proper inclusion of excitonic effects. [less ▲]

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See detailRaman Spectroscopy of Graphene
Reichardt, Sven UL; Wirtz, Ludger UL

in Binder, Rolf (Ed.) Optical Properties of Graphene (2017)

Raman spectroscopy of graphene is reviewed from a theoretical perspective. After an introduction of the building blocks (electronic band structure, phonon dispersion, electron-phonon interaction, electron ... [more ▼]

Raman spectroscopy of graphene is reviewed from a theoretical perspective. After an introduction of the building blocks (electronic band structure, phonon dispersion, electron-phonon interaction, electron-light coupling), Raman intensities are calculated using time-dependent perturbation theory. The analysis of the contributing terms allows for an intuitive understanding of the Raman peak positions and intensities. The Raman spectrum of pure graphene only displays two principle peaks. Yet, their variation as a function of internal and external parameters and the occur- rence of secondary, defect-related peaks, conveys a lot of information about the system. Thus, Raman spectroscopy is used routinely to analyze layer number, defects, doping and strain of graphene samples. At the same time, it is an intriguing playground to study the optical properties of graphene. [less ▲]

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See detailLine shape of the Raman 2D peak of graphene in van der Waals heterostructures
Neumann, Christoph; Banszerus, Luca; Schmitz, Michael et al

in Physica Status Solidi B. Basic Research (2016), 253(12), 2326--2330

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See detailModeling charge relaxation in graphene quantum dots induced by electron-phonon interaction
Reichardt, Sven UL; Stampfer, Christoph

in Physical Review B (2016), 93(24), 245423

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See detailCorrespondence: On the nature of strong piezoelectricity in graphene on SiO2
Stampfer, Christoph; Reichardt, Sven UL

in Nature Communications (2016), 7

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See detailSpatial control of laser-induced doping profiles in graphene on hexagonal boron nitride
Neumann, Christoph; Rizzi, Leo; Reichardt, Sven UL et al

in ACS Applied Materials and Interfaces (2016), 8(14), 9377-9383

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See detailTheoretical Study of the Raman G Peak Intensity of Graphene
Reichardt, Sven UL; Wirtz, Ludger UL

Poster (2016, February 18)

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See detailProbing electronic lifetimes and phonon anharmonicities in high-quality chemical vapor deposited graphene by magneto-Raman spectroscopy
Neumann, Christoph; Halpaap, Donatus; Reichardt, Sven UL et al

in Applied Physics Letters (2015), 107(23), 233105

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See detailRaman spectroscopy as probe of nanometre-scale strain variations in graphene
Neumann, Christoph; Reichardt, Sven UL; Venezuela, Pedro et al

in Nature Communications (2015), 6

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See detailRaman spectroscopy as probe of nanometre-scale strain variations in graphene
Neumann, Christoph; Reichardt, Sven UL; Venezuela, Pedro et al

Poster (2015, July 14)

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See detailLow B field magneto-phonon resonances in single-layer and bilayer graphene
Neumann, Christoph; Reichardt, Sven UL; Drögeler, Marc et al

in Nano Letters (2015), 15(3), 1547--1552

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See detailRelaxation times and electron-phonon interaction in graphene quantum dots
Reichardt, Sven UL; Volk, Christian; Neumann, Christoph et al

Poster (2014, November 07)

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See detailRaman spectroscopy on mechanically exfoliated pristine graphene ribbons
Terrés, Bernat; Reichardt, Sven UL; Neumann, Christoph et al

in Physica Status Solidi B. Basic Research (2014), 251(12), 2551--2555

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See detailImpact of thermal annealing on graphene devices encapsulated in hexagonal boron nitride
Engels, Stephan; Terrés, Bernat; Klein, Felix et al

in Physica Status Solidi B. Basic Research (2014), 251(12), 2545--2550

Detailed reference viewed: 73 (2 UL)
See detailRelaxation times and electron-phonon interaction in graphene quantum dots
Reichardt, Sven UL; Volk, Christian; Neumann, Christoph et al

Poster (2013, May 23)

Detailed reference viewed: 71 (1 UL)