176 Works

Observing gravitational-wave transient GW150914 with minimal assumptions

B.P. Abbott, Bruce Allen, Peter Aufmuth, A. Bisht, Karsten Danzmann, T. Denker, M. Heurs, S. Kaufer, C. Krueger, J.D. Lough, Harald Lück, A. Sawadsky, D. Schütte, D. Steinmeyer, H. Vahlbruch, Benno Willke, M.H. Wimmer, H. Wittel, , & Virgo Collaboration
The gravitational-wave signal GW150914 was first identified on September 14, 2015, by searches for short-duration gravitational-wave transients. These searches identify time-correlated transients in multiple detectors with minimal assumptions about the signal morphology, allowing them to be sensitive to gravitational waves emitted by a wide range of sources including binary black hole mergers. Over the observational period from September 12 to October 20, 2015, these transient searches were sensitive to binary black hole mergers similar to...

Parametric amplification of matter waves in dipolar spinor Bose-Einstein condensates

Frank Deuretzbacher, Garu Gebreyesus, Oliver Topic, Manuel Scherer, Bernd Lücke, Wolfgang Ertmer, Jan J. Arlt, Carsten Klempt & Luis Santos
Spin-changing collisions may lead under proper conditions to the parametric amplification of matter waves in spinor Bose-Einstein condensates. Magnetic dipole-dipole interactions, although typically very weak in alkalimetal atoms, are shown to play a very relevant role in the amplification process. We show that these interactions may lead to a strong dependence of the amplification dynamics on the angle between the trap axis and the magnetic-field orientation. We analyze as well the important role played by...

Quantum magnetism without lattices in strongly interacting one-dimensional spinor gases

Frank Deuretzbacher, D. Becker, J. Bjerlin, S.M. Reimann & Luis Santos
We show that strongly interacting multicomponent gases in one dimension realize an effective spin chain, offering an alternative simple scenario for the study of one-dimensional (1D) quantum magnetism in cold gases in the absence of an optical lattice. The spin-chain model allows for an intuitive understanding of recent experiments and for a simple calculation of relevant observables. We analyze the adiabatic preparation of antiferromagnetic and ferromagnetic ground states, and show that many-body spin states may...

Momentum distributions and numerical methods for strongly interacting one-dimensional spinor gases

Frank Deuretzbacher, D. Becker & Luis Santos
One-dimensional spinor gases with strong δ interaction fermionize and form a spin chain. The spatial degrees of freedom of this atom chain can be described by a mapping to spinless noninteracting fermions and the spin degrees of freedom are described by a spin-chain model with nearest-neighbor interactions. Here, we compute momentum and occupation-number distributions of up to 16 strongly interacting spinor fermions and bosons as a function of their spin imbalance, the strength of an...

Longitudinal spin relaxation in simple stochastic models for disordered systems

P. Borgs, K.W. Kehr & Paul Heitjans
The relaxation of single probe spins was investigated for simple models of systems with quenched disorder. The spin relaxation was calculated for a two-site model with arbitrarily oriented magnetic fields and the result was averaged over various distributions of the fields, and of the hopping rates of the spin. On an intermediate time scale, a modified Kubo-Toyabe behavior is obtained for large hopping rates, in agreement with recent SR experiments. A stretched-exponential decay of the...

Fast dynamics of H2O in hydrous aluminosilicate glasses studied with quasielastic neutron scattering

Sylvio Indris, Paul Heitjans, Harald Behrens, Reiner Zorn & Bernhard Frick
We studied the dynamics of dissolved water in aluminosilicate glasses with the compositions NaAlSi3O8⋅0.3H2O, NaAlSi3O8⋅1.3H2O and Ca0.5AlSi3O8⋅1.3H2O using quasielastic neutron scattering. As shown by near-infrared spectroscopy on these samples, H2O molecules are the predominant hydrous species in the water-rich glasses whereas OH groups bound to tetrahedrally coordinated cations are predominant at low water contents. Backscattering and time-of-flight methods were combined to investigate motional correlation times in the range between 0.2ps and 2ns. For the water-rich...

High-resolution vehicle headlamps: Technologies and scanning prototype

Gerolf Kloppenburg, Alexander Wolf & Roland Lachmayer
The introduction of adaptive front lighting systems for vehicles has increased road safety and drivers' comfort significantly within the last years. A next step in this development is the realization of higher resolution systems to further increase the functionality of vehicle headlamps toward fully adaptive front lighting systems. In this paper, we present a short overview on highly dynamic front lighting systems and the essential technologies for their realization. Different approaches are compared and evaluated...

Lithium motion in the anode material LiC6 as seen via time-domain 7Li NMR

J. Langer, Viktor Epp, Paul Heitjans, F.A. Mautner & Martin Wilkening
Since the commercialization of rechargeable lithium-ion energy storage systems in the early 1990s, graphite intercalation compounds (GICs) have served as the number one negative electrode material in most of today's batteries. During charging the performance of a battery is closely tied with facile Li insertion into the graphite host structure. So far, only occasionally time-domain nuclear magnetic resonance (NMR) measurements have been reported to study Li self-diffusion parameters in GICs. Here, we used several NMR...

Engineering interactions and anyon statistics by multicolor lattice-depth modulations

Lorenzo Cardarelli, Sebastian Greschner & Luis Santos
We show that a multicolor modulation of the depth of an optical lattice allows for a flexible independent control of correlated hopping, occupation-dependent gauge fields, effective on-site interactions without Feshbach resonances, and nearest-neighbor interactions. As a result, the lattice-depth modulation opens the possibility of engineering with minimal experimental complexity a broad class of lattice models in current experiments with ultracold atoms, including Hubbard models with correlated hopping, peculiar extended models, and two-component anyon-Hubbard models. ©...

Polar molecules in frustrated triangular ladders

Tapan Mishra, Sebastian Greschner & Luis Santos
Polar molecules in geometrically frustrated lattices may result in a very rich landscape of quantum phases, due to the nontrivial interplay between frustration, and two- and possibly three-body intersite interactions. In this paper we illustrate this intriguing physics for the case of hard-core polar molecules in frustrated triangular ladders. Whereas commensurate lattice fillings result in gapped phases with bond order and/or density-wave order, at incommensurate fillings we find chiral, two-component, and pair superfluids. We show...

Exploring unconventional hubbard models with doubly modulated lattice gases

Sebastian Greschner, Luis Santos & D. Poletti
Recent experiments show that periodic modulations of cold atoms in optical lattices may be used to engineer and explore interesting models. We show that double modulation combining lattice shaking and modulated interactions allows for the engineering of a much broader class of lattice with correlated hopping, which we study for the particular case of one-dimensional systems. We show, in particular, that by using this double modulation it is possible to study Hubbard models with asymmetric...

First all-sky search for continuous gravitational waves from unknown sources in binary systems

J. Aasi, Bruce Allen, Stefan Ast, Peter Aufmuth, Karsten Danzmann, S. Kaufer, Harald Lück, Tobias Meier, R. Schnabel, H. Vahlbruch, Benno Willke, , & Virgo Collaboration
We present the first results of an all-sky search for continuous gravitational waves from unknown spinning neutron stars in binary systems using LIGO and Virgo data. Using a specially developed analysis program, the TwoSpect algorithm, the search was carried out on data from the sixth LIGO science run and the second and third Virgo science runs. The search covers a range of frequencies from 20 Hz to 520 Hz, a range of orbital periods from...

Electron-spin relaxation in bulk GaAs for doping densities close to the metal-to-insulator transition

M. Römer, H. Bernien, G. Müller, D. Schuh, Jens Hübner & Michael Oestreich
We have measured the electron-spin-relaxation rate and the integrated spin noise power in n-doped GaAs for temperatures between 4 and 80 K and for doping concentrations ranging from 2.7×1015 to 8.8×1016 cm−3 using spin noise spectroscopy. The temperature-dependent measurements show a clear transition from localized to free electrons for the lower doped samples and confirm mainly free electrons at all temperatures for the highest doped sample. While the sample at the metal-to-insulator transition shows the longest...

Optical orientation of electron spins in GaAs quantum wells

S. Pfalz, R. Winkler, T. Nowitzki, D. Reuter, A.D. Wieck, D. Hägele & Michael Oestreich
We present a detailed experimental and theoretical analysis of the optical orientation of electron spins in GaAs/AlAs quantum wells. Using time and polarization resolved photoluminescence excitation spectroscopy, the initial degree of electron-spin polarization is measured as a function of excitation energy for a sequence of quantum wells with well widths between 63 and 198 Å. The experimental results are compared with an accurate theory of excitonic absorption taking fully into account electron-hole Coulomb correlations and...

Skepsis als Weg zum Glück? Eine Untersuchung zum Zusammenhang von Urteilsenthaltung und Seelenruhe in der Antike und der Aufklärung

Anneke Meyer
Wezel stimmte 1776 ein Lob des Zweifels an, obwohl zu dieser Zeit der frühe neuzeitliche Zweifel längst vom Fortschrittsoptimismus der Wissenschaft abgelöst war. Zugleich behauptete er, dass eine skeptische Lebenshaltung zu einem ruhigen und gelassenen, womöglich sogar glücklichen Leben führen könne. (www.wehrhahn-verlag.de)

Gerhart Hauptmanns Erzählung Mignon. Mit Erstdruck der ersten Fassung und Materialien

Bernhard Tempel
Die Erzählung Mignon – zwischen 1939 und 1944 entstanden und 1947 posthum veröffentlicht – ist ein bislang unterschätztes Zeugnis für Gerhart Hauptmanns Goethe-Rezeption. Die vorliegende Studie rekonstruiert zunächst die Entstehungsgeschichte des Werks und legt eine Interpretation vor, die vor allem das Spannungsfeld von intertextuellen und autobiographischen Bezügen berücksichtigt Von den Entwurfsnotizen und der ersten Niederschrift, der sogenannten 'Stresa-Novelle', bis zur Endfassung ändert sich die Konzeption gravierend. Die Erzählung, die als „Biographie einer Geistererscheinung“ noch ganz...

Graduiertenkolleg beantragen

Anneke Meyer
Ein Graduiertenkolleg bei der Deutschen Forschungsgemeinschaft (DFG) zu beantragen, umfasst mehr als das Schreiben eines Antrags. So muss unter anderem die Rolle der Sprecherin oder des Sprechers aktiv ausgefüllt werden. Worauf Sie dabei unbedingt achten sollten, erfahren Sie auf den folgenden Seiten.

Fermi nesting between atomic wires with strong spin-orbit coupling

Christoph Tegenkamp, Daniel Lükermann, Herbert Pfnür, B. Slomski, G. Landolt & J.H. Dil
The mutual interplay between superlattice structures, band filling factors, and spin-orbit coupling results in a highly correlated electronic spin and charge state found for an array of atomic Pb wires grown on Si(557). By means of spin- and angle-resolved photoemission spectroscopy, the spin texture close to the Fermi surface was found to be alternating and equidistant; thus, Fermi nesting occurs in between bands with the same spin helicity, giving rise to spin-polarized charge-density waves in...

Planck-scale-modified dispersion relations in homogeneous and isotropic spacetimes

Leonardo Barcaroli, Lukas K. Brunkhorst, Giulia Gubitosi, Niccoló Loret & Christian Pfeifer
The covariant understanding of dispersion relations as level sets of Hamilton functions on phase space enables us to derive the most general dispersion relation compatible with homogeneous and isotropic spacetimes. We use this concept to present a Planck-scale deformation of the Hamiltonian of a particle in Friedman-Lemaître-Robertson-Walker (FLRW) geometry that is locally identical to the κ-Poincaré dispersion relation, in the same way as the dispersion relation of point particles in general relativity is locally identical...

Interplay of Electron and Nuclear Spin Noise in n -Type GaAs

Fabian Berski, Jens Hübner, Michael Oestreich, Arne Ludwig, A.D. Wieck & Mikhail Glazov
We present spin-noise spectroscopy measurements on an ensemble of donor-bound electrons in ultrapure GaAs:Si covering temporal dynamics over 6 orders of magnitude from milliseconds to nanoseconds. The spin-noise spectra detected at the donor-bound exciton transition show the multifaceted dynamical regime of the ubiquitous mutual electron and nuclear spin interaction typical for III-V-based semiconductor systems. The experiment distinctly reveals the finite Overhauser shift of an electron spin precession at zero external magnetic field and a second...

Optical spin noise of a single hole spin localized in an (InGa)as quantum dot

Ramin Dahbashi, Jens Hübner, Fabian Berski, Klaus Pierz & Michael Oestreich
We advance spin noise spectroscopy to the ultimate limit of single spin detection. This technique enables the measurement of the spin dynamic of a single heavy hole localized in a flat (InGa)As quantum dot. Magnetic field and light intensity dependent studies reveal even at low magnetic fields a strong magnetic field dependence of the longitudinal heavy hole spin relaxation time with an extremely long T1 of ?180?s at 31 mT and 5 K. The wavelength...

Effect of symmetry reduction on the spin dynamics of (001)-oriented GaAs quantum wells

D.J. English, Jens Hübner, P.S. Eldridge, D. Taylor, M. Henini, R.T. Harley & Michael Oestreich
Spin quantum beat spectroscopy is employed to investigate the in-plane anisotropy of the spin dynamics in (001) GaAs/AlGaAs quantum wells induced by an external electric field. This technique allows the anisotropy of the spin relaxation rate Γs and the electron Landé g factor g* to be measured simultaneously. The measurements are compared to similar data from (001) GaAs/AlGaAs quantum wells with applied shear strain and asymmetric barrier growth. All of these operations act to reduce...

Lab-level and low-cost fabrication technique for polymer based micro-optical elements and holographic structures

Maik Rahlves, Maher Rezem, Christian Kelb, Kristian Boroz, Dina Gödeke, Sebastian Schlangen, Eduard Reithmeier & Bernhard Roth
Polymer based diffractive optical elements have gained increasing interest due to their potential to be used in various applications such as illumination technology, micro optics and holography. We present a novel production process to fabricate polymer based diffractive optical elements and holograms. The process is based on maskless lithography, which is used to fabricate optical elements in photoresist. We discuss several lab-made lithography setups based on digital mirror devices and liquid crystal devices with respect...

Optimization of novel phase separating IBS process

Marco Jupé, Thomas Willemsen, Sina Malobabic, Kornelia Schuba & Detlev Ristau
During the last years, optical low loss components gained more and more industrial interest and led to novel approaches for the production in optical coating technology. The application of filtered deposition technologies promises a significant reduction of particle contamination. Usually, filtered techniques are applied in combination with processes which produce a high level of undesired particles, like the cathodic arc deposition. In the present contribution, a magnetic field filter is applied in combination with a...

In situ static and dynamic light scattering and scanning electron microscopy study on the crystallization of the dense zinc imidazolate framework ZIF-zni

Todor Hikov, Christian A. Schröder, Janosch Cravillon, Michael Wiebcke & Klaus Huber
The kinetics and mechanism of crystallization of the dense zinc imidazolate framework with zni topology, from comparatively dilute methanol solutions containing Zn(NO3)·6H2O and imidazole with variation of the zinc-to-imidazole ratio, were followed in situ by time-resolved static and dynamic light scattering. The light scattering data revealed that metastable primary particles of about 100 nm in diameter form rapidly upon mixing the component solutions. After a lag time that is dependent on the imidazole concentration, the...

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