@article{15863, author = {{Vollbrecht, Joachim and Bock, Harald and Wiebeler, Christian and Schumacher, Stefan and Kitzerow, Heinz-Siegfried}}, issn = {{0947-6539}}, journal = {{Chemistry - A European Journal}}, pages = {{12026--12031}}, title = {{{Polycyclic Aromatic Hydrocarbons Obtained by Lateral Core Extension of Mesogenic Perylenes: Absorption and Optoelectronic Properties}}}, doi = {{10.1002/chem.201403287}}, year = {{2014}}, } @article{15861, author = {{Riesen, Hans and Wiebeler, Christian and Schumacher, Stefan}}, issn = {{1089-5639}}, journal = {{The Journal of Physical Chemistry A}}, pages = {{5189--5195}}, title = {{{Optical Spectroscopy of Graphene Quantum Dots: The Case of C132}}}, doi = {{10.1021/jp502753a}}, year = {{2014}}, } @article{15862, author = {{Wiebeler, Christian and Schumacher, Stefan}}, issn = {{1089-5639}}, journal = {{The Journal of Physical Chemistry A}}, pages = {{7816--7823}}, title = {{{Quantum Yields and Reaction Times of Photochromic Diarylethenes: Nonadiabatic Ab Initio Molecular Dynamics for Normal- and Inverse-Type}}}, doi = {{10.1021/jp506316w}}, year = {{2014}}, } @inbook{18471, abstract = {{Collective spin excitations form a fundamental class of excitations in magnetic materials. As their energy reaches down to only a few meV, they are present at all temperatures and substantially influence the properties of magnetic systems. To study the spin excitations in solids from first principles, we have developed a computational scheme based on many-body perturbation theory within the full-potential linearized augmented plane-wave (FLAPW) method. The main quantity of interest is the dynamical transverse spin susceptibility or magnetic response function, from which magnetic excitations, including single-particle spin-flip Stoner excitations and collective spin-wave modes as well as their lifetimes, can be obtained. In order to describe spin waves we include appropriate vertex corrections in the form of a multiple-scattering T matrix, which describes the coupling of electrons and holes with different spins. The electron–hole interaction incorporates the screening of the many-body system within the random-phase approximation. To reduce the numerical cost in evaluating the four-point T matrix, we exploit a transformation to maximally localized Wannier functions that takes advantage of the short spatial range of electronic correlation in the partially filled d or f orbitals of magnetic materials. The theory and the implementation are discussed in detail. In particular, we show how the magnetic response function can be evaluated for arbitrary k points. This enables the calculation of smooth dispersion curves, allowing one to study fine details in the k dependence of the spin-wave spectra. We also demonstrate how spatial and time-reversal symmetry can be exploited to accelerate substantially the computation of the four-point quantities. As an illustration, we present spin-wave spectra and dispersions for the elementary ferromagnet bcc Fe, B2-type tetragonal FeCo, and CrO2 calculated with our scheme. The results are in good agreement with available experimental data.}}, author = {{Friedrich, Christoph and Şaşıoğlu, Ersoy and Müller, Mathias and Schindlmayr, Arno and Blügel, Stefan}}, booktitle = {{First Principles Approaches to Spectroscopic Properties of Complex Materials}}, editor = {{Di Valentin, Cristiana and Botti, Silvana and Cococcioni, Matteo}}, isbn = {{978-3-642-55067-6}}, issn = {{1436-5049}}, pages = {{259--301}}, publisher = {{Springer}}, title = {{{Spin excitations in solids from many-body perturbation theory}}}, doi = {{10.1007/128_2013_518}}, volume = {{347}}, year = {{2014}}, } @inbook{18472, abstract = {{Many-body perturbation theory is a well-established ab initio electronic-structure method based on Green functions. Although computationally more demanding than density functional theory, it has the distinct advantage that the exact expressions for all relevant observables, including the ground-state total energy, in terms of the Green function are known explicitly. The most important application, however, lies in the calculation of excited states, whose energies correspond directly to the poles of the Green function in the complex frequency plane. The accuracy of results obtained within this framework is only limited by the choice of the exchange-correlation self-energy, which must still be approximated in actual implementations. In this respect, the GW approximation has proved highly successful for systems governed by the Coulomb interaction. It yields band structures of solids, including the band gaps of semiconductors, as well as atomic and molecular ionization energies in very good quantitative agreement with experimental photoemission data.}}, author = {{Schindlmayr, Arno}}, booktitle = {{Many-Electron Approaches in Physics, Chemistry and Mathematics}}, editor = {{Bach, Volker and Delle Site, Luigi}}, isbn = {{978-3-319-06378-2}}, issn = {{2352-3905}}, pages = {{343--357}}, publisher = {{Springer}}, title = {{{The GW approximation for the electronic self-energy}}}, doi = {{10.1007/978-3-319-06379-9_19}}, volume = {{29}}, year = {{2014}}, } @article{18473, abstract = {{We investigate the band dispersion and related electronic properties of picene single crystals within the GW approximation for the electronic self-energy. The width of the upper highest occupied molecular orbital (HOMOu) band along the Γ–Y direction, corresponding to the b crystal axis in real space along which the molecules are stacked, is determined to be 0.60 eV and thus 0.11 eV larger than the value obtained from density-functional theory. As in our recent study of rubrene using the same methodology [S. Yanagisawa, Y. Morikawa, and A. Schindlmayr, Phys. Rev. B 88, 115438 (2013)], this increase in the bandwidth is due to the strong variation of the GW self-energy correction across the Brillouin zone, which in turn reflects the increasing hybridization of the HOMOu states of neighboring picene molecules from Γ to Y. In contrast, the width of the lower HOMO (HOMOl) band along Γ–Y remains almost unchanged, consistent with the fact that the HOMOl(Γ) and HOMOl(Y) states exhibit the same degree of hybridization, so that the nodal structure of the wave functions and the matrix elements of the self-energy correction are very similar.}}, author = {{Yanagisawa, Susumu and Morikawa, Yoshitada and Schindlmayr, Arno}}, issn = {{1347-4065}}, journal = {{Japanese Journal of Applied Physics}}, number = {{5S1}}, publisher = {{IOP Publishing and The Japan Society of Applied Physics}}, title = {{{Theoretical investigation of the band structure of picene single crystals within the GW approximation}}}, doi = {{10.7567/jjap.53.05fy02}}, volume = {{53}}, year = {{2014}}, } @inbook{18474, author = {{Friedrich, Christoph and Schindlmayr, Arno}}, booktitle = {{Computing Solids: Models, ab initio Methods and Supercomputing}}, editor = {{Blügel, Stefan and Helbig, Nicole and Meden, Volker and Wortmann, Daniel}}, isbn = {{978-3-89336-912-6}}, issn = {{1866-1807}}, location = {{Jülich}}, pages = {{A4.1--A4.21}}, publisher = {{Forschungszentrum Jülich}}, title = {{{Many-body perturbation theory: The GW approximation}}}, volume = {{74}}, year = {{2014}}, } @article{40400, author = {{Pérez, A. M. and Iskhakov, T. Sh. and Sharapova, Polina and Lemieux, S. and Tikhonova, O. V. and Chekhova, M. V. and Leuchs, G.}}, issn = {{0146-9592}}, journal = {{Optics Letters}}, keywords = {{Atomic and Molecular Physics, and Optics}}, number = {{8}}, publisher = {{The Optical Society}}, title = {{{Bright squeezed-vacuum source with 11 spatial mode}}}, doi = {{10.1364/ol.39.002403}}, volume = {{39}}, year = {{2014}}, } @article{43198, abstract = {{Ultrafast charge transport in strongly biased semiconductors is at the heart of high-speed electronics, electro-optics and fundamental solid-state physics1,2,3,4,5,6,7,8,9,10,11,12,13. Intense light pulses in the terahertz spectral range have opened fascinating vistas14,15,16,17,18,19,20,21. Because terahertz photon energies are far below typical electronic interband resonances, a stable electromagnetic waveform may serve as a precisely adjustable bias5,11,17,19. Novel quantum phenomena have been anticipated for terahertz amplitudes, reaching atomic field strengths8,9,10. We exploit controlled (multi-)terahertz waveforms with peak fields of 72 MV cm−1 to drive coherent interband polarization combined with dynamical Bloch oscillations in semiconducting gallium selenide. These dynamics entail the emission of phase-stable high-harmonic transients, covering the entire terahertz-to-visible spectral domain between 0.1 and 675 THz. Quantum interference of different ionization paths of accelerated charge carriers is controlled via the waveform of the driving field and explained by a quantum theory of inter- and intraband dynamics. Our results pave the way towards all-coherent terahertz-rate electronics.}}, author = {{Meier, Torsten and Schubert, O. and Hohenleutner, M. and Langer, F. and Urbanek, B. and Lange, C. and Huttner, U. and Golde, D. and Kira, M. and Koch, S. W. and Huber, R.}}, journal = {{Nature Photonics}}, number = {{2}}, publisher = {{Nature Publishing Group}}, title = {{{Sub-cycle control of terahertz high-harmonic generation by dynamical Bloch oscillations}}}, doi = {{10.1038/nphoton.2013.349}}, volume = {{8}}, year = {{2014}}, } @article{43251, abstract = {{The nonadiabatic dynamics of a many-body system driven through a quantum critical point can be controlled using counterdiabatic driving, where the formation of excitations is suppressed by assisting the dynamics with auxiliary multiple-body nonlocal interactions. We propose an alternative scheme which circumvents practical challenges to realize shortcuts to adiabaticity in mesoscopic systems by tailoring the functional form of the auxiliary counterdiabatic interactions. A driving scheme resorting in short-range few-body interactions is shown to generate an effectively adiabatic dynamics.}}, author = {{Saberi, H. and Opatrný, T. and Mølmer, K. and del Campo,, A.}}, journal = {{Physical Review A}}, number = {{6}}, title = {{{Adiabatic tracking of quantum many-body dynamics}}}, doi = {{10.1103/PhysRevA.90.060301}}, volume = {{90}}, year = {{2014}}, } @article{41967, author = {{Decker, Claudia and Stroot, Thea}}, journal = {{Lehrerbildung heute – Impulse für Studium und Lehre}}, publisher = {{Hochschulrektorenkonferenz Projekt nexus}}, title = {{{Profilstudium „Umgang mit Heterogenität“. Wie Lehramtsstudierende der Universität Paderborn eigene Akzente setzen}}}, year = {{2014}}, } @article{36296, author = {{Vogelsang, Christoph and Reinhold, Peter}}, journal = {{Zeitschrift für Didaktik der Naturwissenschaften}}, pages = {{103--128}}, title = {{{Zur Handlungsvalidität von Tests zum professionellen Wissen von Lehrkräften}}}, volume = {{19}}, year = {{2013}}, } @article{13520, abstract = {{Atomistic simulations in the framework of the density functional theory have been used to model morphologic and vibrational properties of lithium niobate–lithium tantalate mixed crystals as a function of the [Nb]/[Ta] ratio. Structural parameters such as the crystal volume and the lattice parameters a and c vary roughly linearly from LiTaO3 to LiNbO3, showing only minor deviations from the Vegard behavior. Our ab initio calculations demonstrate that the TO1, TO2 and TO4 vibrational modes become harder with increasing Nb concentration. TO3 becomes softer with increasing Nb content, instead. Furthermore, the investigated zone center A1 -TO phonon modes are characterized by a pronounced stoichiometry dependence. Frequency shifts as large as 30 cm−1 are expected as the [Nb]/[Ta] ratio grows from 0 to 1. Therefore, spectroscopic techniques sensitive to the A1 modes (such as Raman spectroscopy), can be employed for a direct and non-destructive determination of the crystal composition.}}, author = {{Sanna, Simone and Riefer, A. and Neufeld, Sergej and Schmidt, Wolf Gero and Berth, Gerhard and Rüsing, Michael and Widhalm, A. and Zrenner, Artur}}, issn = {{0015-0193}}, journal = {{Ferroelectrics}}, keywords = {{Ferroelectrics, vibrational properties, LiNbO3, LiTaO3, mixed crystals}}, number = {{1}}, pages = {{63--68}}, title = {{{Vibrational Fingerprints of LiNbO3-LiTaO3Mixed Crystals}}}, doi = {{10.1080/00150193.2013.821893}}, volume = {{447}}, year = {{2013}}, } @phdthesis{52654, author = {{Geisler , J.}}, isbn = {{978-3-942647-39-7}}, title = {{{Selbstoptimierende Spurenführung für ein neuartiges Schienenfahrzeug }}}, volume = {{Band 320}}, year = {{2013}}, } @proceedings{25300, editor = {{Gausemeier, Jürgen and Dumitrescu, Roman and Rammig, Franz-Josef and Schäfer, Wilhelm and Trächtler, Ansgar}}, publisher = {{Heinz Nixdorf Institut, Verlagsschriftenreihe des Heinz Nixdorf Instituts, Paderborn}}, title = {{{9. Paderborner Workshop Entwurf mechatronischer Systeme}}}, volume = {{310}}, year = {{2013}}, } @phdthesis{25285, author = {{Montealegre, Norma}}, publisher = {{Verlagsschriftenreihe des Heinz Nixdorf Instituts, Paderborn, Band 315, Jul. 2013}}, title = {{{Immunorepairing of Hardware Systems}}}, year = {{2013}}, } @phdthesis{37569, abstract = {{Das Marktportfolio der Hinterachsen weist zwischen den Achskonzepten Schwertlenkerachse und Verbundlenkerachse sowohl im Bereich der fahrdynamischen Auslegungsmöglichkeiten als auch unter Kosten- und Gewichtsaspekten eine Lücke auf. Dieser vom Markt zur Zeit nicht gedeckte Bereich lässt sich durch eine gezielte elastokinematische Aufwertung von Verbundlenkerachsen schließen. Zur Aufwertung und Weiterentwicklung der Verbundlenkerachse ist eine elastokinematische Spurkorrektur unter Seitenkraft und unter Bremskraft sowie eine Verbesserung des Verhältnisses zwischen Seiten- und Längssteifigkeit notwendig. Die vorliegende Promotionsschrift beschreibt und analysiert zunächst die Eigenschaften bestehender Ansätze zur elastokinematischen Optimierung von Verbundlenkerachsen. Basierend auf den Erkenntnissen dieser Untersuchungen wird eine Verbundlenkerachse mit entkoppeltem Radträger entwickelt, welche sowohl unter wirtschaftlichen als auch unter performanten Gesichtspunkten zwischen einer regulären Verbundlenkerachse und einer Schwertlenkerachse platziert werden kann. Die Entwicklung erfolgt vom Konzeptentwurf bis zum auskonstruierten Bauteil auf Basis numerischer Simulation. Die entwickelte Konstruktion wird in einen Prototypen überführt, welcher in einen Ford Focus implementiert wird. In Fahr- und Komponentenversuchen wird das Verhalten des neuen Achskonzepts untersucht und mit konkurrierenden Achskonzepten verglichen.}}, author = {{Schultz, Erik}}, isbn = {{978-3-8440-2290-2}}, keywords = {{Verbundlenkerachse, Fahrwerk, Hinterachse, Elastokinematik, entkoppelter Radträger}}, pages = {{232}}, publisher = {{Shaker Verlag}}, title = {{{Analyse und Synthese elastokinematisch optimierter Verbundlenkerachsen - Entwicklung einer Verbundlenkerachse mit entkoppeltem Radträger}}}, volume = {{2013,3}}, year = {{2013}}, } @article{39717, author = {{Lorenz, Alexander and Zimmermann, Natalie and Kumar, Satyendra and Evans, Dean R. and Cook, Gary and Martínez, Manuel Fernández and Kitzerow, Heinz-Siegfried}}, issn = {{1559-128X}}, journal = {{Applied Optics}}, keywords = {{Atomic and Molecular Physics, and Optics, Engineering (miscellaneous), Electrical and Electronic Engineering}}, number = {{22}}, publisher = {{The Optical Society}}, title = {{{X-ray scattering of nematic liquid crystal nanodispersion with negative dielectric anisotropy [Invited]}}}, doi = {{10.1364/ao.52.0000e1}}, volume = {{52}}, year = {{2013}}, } @article{39715, author = {{Nordendorf, Gaby and Lorenz, Alexander and Hoischen, Andreas and Schmidtke, Jürgen and Kitzerow, Heinz-Siegfried and Wilkes, David and Wittek, Michael}}, issn = {{0021-8979}}, journal = {{Journal of Applied Physics}}, keywords = {{General Physics and Astronomy}}, number = {{17}}, publisher = {{AIP Publishing}}, title = {{{Hysteresis and memory factor of the Kerr effect in blue phases}}}, doi = {{10.1063/1.4828477}}, volume = {{114}}, year = {{2013}}, } @inproceedings{39712, author = {{Schmidtke, Juergen and Lu, Lu and Kitzerow, Heinz-Siegfried and Terentjev, Eugene M.}}, booktitle = {{SPIE Proceedings}}, editor = {{Chien, Liang-Chy and Broer, Dick J. and Chigrinov, Vladimir and Yoon, Tae-Hoon}}, issn = {{0277-786X}}, publisher = {{SPIE}}, title = {{{Liquid crystal lasers: recent advances}}}, doi = {{10.1117/12.2008373}}, year = {{2013}}, }