@article{40084, author = {{Röder, Th. and Paelke, L. and Held, N. and Vinzelberg, S. and Kitzerow, Heinz-Siegfried}}, issn = {{0034-6748}}, journal = {{Review of Scientific Instruments}}, keywords = {{Instrumentation}}, number = {{7}}, pages = {{2759--2764}}, publisher = {{AIP Publishing}}, title = {{{Imaging of liquid crystals using a new scanning near-field optical microscope with microfabricated tips and shear force detection}}}, doi = {{10.1063/1.1150688}}, volume = {{71}}, year = {{2000}}, } @article{40083, author = {{Glossmann, Jochen and Hoischen, Andreas and Roder, Thorsten and Kitzerow, Heinz-Siegfried}}, issn = {{0015-0193}}, journal = {{Ferroelectrics}}, keywords = {{Condensed Matter Physics, Electronic, Optical and Magnetic Materials}}, number = {{1}}, pages = {{95--106}}, publisher = {{Informa UK Limited}}, title = {{{Asymmetric switching and storage effects in ferroelectric and antiferroelectric gels and polymers}}}, doi = {{10.1080/00150190008008011}}, volume = {{243}}, year = {{2000}}, } @article{42051, author = {{Inglés, Sergio Escudero and Katzenstein, Armin and Schlenker, Wolfgang and Huber, Klaus}}, issn = {{0743-7463}}, journal = {{Langmuir}}, keywords = {{Electrochemistry, Spectroscopy, Surfaces and Interfaces, Condensed Matter Physics, General Materials Science}}, number = {{7}}, pages = {{3010--3018}}, publisher = {{American Chemical Society (ACS)}}, title = {{{Time-Resolved Recording of Ionic Dyestuff Aggregation by Static Light Scattering}}}, doi = {{10.1021/la9903649}}, volume = {{16}}, year = {{2000}}, } @article{26005, abstract = {{Mesostructured aluminophosphate/dodecyl phosphate composite materials were synthesized under aqueous and alcoholic conditions. The syntheses were monitored by temperature- and time-resolved in-situ small-angle X-ray scattering (SAXS). In the aqueous synthesis, a lamellar mesostructure is formed within the first few minutes of the reaction; this structure maintains a constant d spacing independent of the reaction time and temperature. The alcoholic synthesis at low temperature yields a mixture of a lamellar and a supposedly inverted hexagonal mesostructure. SAXS investigations show that these two phases evolve competitively. The lamellar structure is favored by higher temperatures and/or longer synthesis times; above ∼70 °C it is formed exclusively. Mixtures of both phases can be isolated as solid materials, but thermal analysis shows that the inverted hexagonal product transforms into the lamellar phase at ∼35−43 °C. The alcoholic synthesis is a highly cooperative reaction; the pure surfactant/alcohol systems are not lyotropic as long as the inorganic reactants are absent. In comparison, the surfactant/water system with the same surfactant concentrations as employed for the aqueous syntheses is lyotropic with a lamellar structure.}}, author = {{Tiemann, Michael and Fröba, M. and Rapp, G. and Funari, S. S.}}, issn = {{0897-4756}}, journal = {{Chemistry of Materials}}, pages = {{1342--1348}}, title = {{{Nonaqueous Synthesis of Mesostructured Aluminophosphate/Surfactant Composites:  Synthesis, Characterization, and In-Situ SAXS Studies}}}, doi = {{10.1021/cm991165d}}, year = {{2000}}, } @article{26004, abstract = {{The atomic structure of ordered mesostructured aluminophosphates with dodecyl phosphate as the structure-directing template was investigated by multinuclear solid-state NMR. Two different types of materials were studied:  one with the template headgroup as the only phosphate source and one where additionally phosphoric acid was used in the synthesis. All 31P and 27Al NMR resonances can be subdivided into three groups depending on the sample composition. Furthermore, 2D heteronuclear correlation NMR measurements allow a conclusive and unambiguous identification of the phosphate headgroup resonances of the template molecules and the determination of water and/or hydroxyl units. Most notably, there is an obvious correlation between the d001 values of the samples as measured by powder X-ray diffraction and the appearance of the various groups of 27Al and 31P resonances.}}, author = {{Schulz, M. and Tiemann, Michael and Fröba, M. and Jäger, C.}}, issn = {{1520-6106}}, journal = {{The Journal of Physical Chemistry B}}, pages = {{10473--10481}}, title = {{{NMR Characterization of Mesostructured Aluminophosphates}}}, doi = {{10.1021/jp000337n}}, year = {{2000}}, } @inbook{26006, abstract = {{Mesostructured aluminophosphate / surfactant composite materials were prepared from aqueous and alcoholic systems. Syntheses in ethanol or methanol, respectively, lead to mixtures of two nanostructured phases. One of these consists of hexagonally arranged rod-like assemblies of the surfactant molecules with the head groups located in the centres, encapsulating the inorganic aluminophosphate; the other is lamellar. The syntheses were monitored by in-situ temperature- and time-resolved small angle X-ray scattering (SAXS).}}, author = {{Tiemann, Michael and Fröba, M. and Rapp, G. and Funari, S.S.}}, booktitle = {{Nanoporous Materials II, Proceedings of the 2nd Conference on Access in Nanoporous Materials}}, issn = {{0167-2991}}, title = {{{In-situ small angle x-ray scattering (SAXS) studies on the formation of mesostructured aluminophosphate / surfactant composite materials}}}, doi = {{10.1016/s0167-2991(00)80258-x}}, year = {{2000}}, } @article{43318, abstract = {{The density-dependent absorption in the presence of incoherent occupations of excitons and electron–hole pairs is analyzed including many-body correlations represented by exciton to two-exciton transitions. At low temperatures the exciton resonance is bleached and shifts to higher energies with increasing density. For higher temperature, the blue shift disappears and pure bleaching is obtained.}}, author = {{Meier, Torsten and Koch, S.W.}}, journal = {{physica status solidi (b)}}, number = {{1}}, pages = {{211--214}}, publisher = {{WILEY‐VCH Verlag Berlin GmbH}}, title = {{{Analysis of Excitonic Absorption Changes Induced by Incoherent Exciton and Electron-Hole-Pair Populations}}}, doi = {{10.1002/1521-3951(200009)221:1<211::AID-PSSB211>3.0.CO;2-L}}, volume = {{221}}, year = {{2000}}, } @article{43314, abstract = {{Two phase-locked pulses are used to coherently excite excitonic polarizations. It is shown that the second pulse can either be strongly amplified by taking up energy gained from the destruction of the exciton polarization or can be decreased drastically by giving up all its energy to excitons. Both the temporal and the spectral signatures of the transmitted pulse shapes agree well with model calculations.}}, author = {{Meier, Torsten and Yee, D.S. and Yee, K.J. and Hohng, S.C. and Kim, D.S. and Koch, S.W.}}, journal = {{Physical review letters}}, number = {{15}}, publisher = {{American Physical Society}}, title = {{{Coherent Control of Absorption and Free Polarization Decay in GaAs Quantum Wells: Time and Spectral Domain Studies}}}, doi = {{10.1103/PhysRevLett.84.3474}}, volume = {{84}}, year = {{2000}}, } @inproceedings{44134, author = {{Meier, Torsten and Brick, P. and Ell, C. and Khitrova, G. and Gibbs, H.M. and Koch, S.W.}}, booktitle = {{Quantum Electronics and Laser Science Conference (QELS 2000)}}, isbn = {{1-55752-608-7}}, issn = {{1094-5695}}, location = {{San Francisco, California United States}}, title = {{{χ(5)-signatures in the optical Stark effect}}}, year = {{2000}}, } @article{44136, author = {{Meier, Torsten and Chernyak, V. and Tretiak, S. and Tsiper, EV.. and Mukamel, S.}}, journal = {{Condensed Matter Theories}}, pages = {{289--298}}, title = {{{Semiclassical Effective Hamiltonian For Coupled Electronic And Nuclear Optical Response}}}, volume = {{14}}, year = {{2000}}, } @article{43315, abstract = {{A microscopic many-body theory for the linear and nonlinear optical properties of semiconductor superlattices subjected to electric fields is presented. The approach has been used for the analysis of various processes related to the Bloch-oscillation dynamics of carriers in static fields and for investigating dynamical localization induced by alternating fields. It is shown that the theory describes very well experimental field-modulated absorption spectra of a strongly coupled superlattice. Furthermore, characteristic signatures, such as negative absorption in the short-pulse optical response of superlattices subjected simultaneously to static and alternating electric fields are predicted.}}, author = {{Meier, Torsten and Kolbe, H.J. and Thränhardt, A. and Weiser, G. and Thomas, P. and Koch, S.W.}}, journal = {{Physica E: Low-dimensional Systems and Nanostructures}}, number = {{1-2}}, pages = {{267--273 }}, publisher = {{North-Holland}}, title = {{{Coherent dynamics of photoexcited semiconductor superlattices in homogeneous electric fields}}}, doi = {{10.1016/S1386-9477(99)00274-X}}, volume = {{7}}, year = {{2000}}, } @article{43310, abstract = {{Local ultrafast optical excitation of electron–hole pairs in disordered semiconductors provides the possibility to observe experimentally interaction-assisted propagation of correlated quantum particles in a disordered environment. In addition to the interaction driven delocalization known for the conventional single-band TIP-(two-interacting-particles)-problem the semiconductor model has a richer variety of physical parameters that give rise to new features in the temporal dynamics. These include different masses, correlated versus anticorrelated disorder for the two particles, and dependence on spectral position of excitation pulse.}}, author = {{Meier, Torsten and Thomas, P. and Varga, I. and Lemm, T. and Golub, J.E. and Maschke, K. and Koch, S.W.}}, journal = {{physica status solidi (b)}}, number = {{1}}, pages = {{125--132}}, publisher = {{WILEY‐VCH Verlag Berlin GmbH}}, title = {{{Propagation of Coulomb-Correlated Electron-Hole Pairs in Semiconductors with Correlated and Anticorrelated Disorder}}}, doi = {{10.1002/(SICI)1521-3951(200003)218:1<125::AID-PSSB125>3.0.CO;2-7}}, volume = {{218}}, year = {{2000}}, } @article{43311, abstract = {{First, we study coupling of excitons in different quantum-well islands by coherent excitation spectroscopy and find that excitons in different islands are not coherently coupled. Second, we investigate exciton and biexciton binding energies in inhomogeneously broadened (GaIn)As/Ga(PAs) multi quantum wells. A strong increase of the 1s–2s-splitting with increasing exciton localization is found, whereas the biexciton binding energy shows a very weak decrease with increasing localization.}}, author = {{Meier, Torsten and Euteneuer, A. and Finger, E. and Stolz, W. and Thomas, P. and Koch, S.W. and Hofmann, M. and Rühle, W.W. and Hey, R. and Ploog, K.H.}}, journal = {{physica status solidi (a)}}, number = {{1}}, pages = {{183--188}}, publisher = {{WILEY‐VCH Verlag Berlin GmbH}}, title = {{{Investigation of Disordered Semiconductor Quantum Wells by Coherent Excitation Spectroscopy}}}, doi = {{10.1002/1521-396X(200003)178:1<183::AID-PSSA183>3.0.CO;2-Q}}, volume = {{178}}, year = {{2000}}, } @article{43313, abstract = {{Microscopic calculations including energetic disorder and Coulomb correlations up to third order in the laser field are performed. The resulting four-wave-mixing signals show polarization-dependent dephasing induced by diagonal disorder. The correct modeling of this disorder-induced dephasing requires the proper inclusion of Coulomb correlations. The theoretical results are in good qualitative agreement with measurements performed on a variety of quantum-well samples.}}, author = {{Meier, Torsten and Weiser, S. and Möbius, J. and Euteneuer, A. and Mayer, E.J. and Stolz, W. and Hofmann, M. and Rühle, W.W. and Thomas, P. and Koch, S.W.}}, journal = {{Physical Review B}}, number = {{19}}, publisher = {{American Physical Society}}, title = {{{Disorder-induced Dephasing in Semiconductors}}}, doi = {{10.1103/PhysRevB.61.13088}}, volume = {{61}}, year = {{2000}}, } @inproceedings{44131, abstract = {{A number of experiments yielded a polarization-dependent decay of the time-integrated four-wavemixing (TI-FWM). Often, the TI-FWM decays more rapidly for linear perpendicular than for linear parallel polarized incident pulses. It was suspected that this difference in the decay times is related to the inhomogeneous linewidth of the exciton, i.e. to disorder [1], On the other hand, it was demonstrated in a large number of recent publications, that the understanding of polarization-dependent FWM and pump-probe experiments following excitonic excitation requires the treatment of Coulomb correlations beyond the Hartree-Fock level. For not too strong disorder, these correlations still remain important and influence the nonlinear optical response [2]. A meaningful analysis of disorder effects thus has to include correlations.}}, author = {{Meier, Torsten and Weiser, S. and Möbius, J. and Euteneuer, A. and Mayer, E.J. and Stolz, W. and Hofmann, M. and Rühle, W.W. and Thomas, P. and Koch, S.W.}}, booktitle = {{International Quantum Electronics Conference}}, isbn = {{0-7803-6318-3}}, location = {{Nice, France}}, publisher = {{IEEE}}, title = {{{Analysis of disorder-induced dephasing}}}, doi = {{10.1109/IQEC.2000.908038}}, year = {{2000}}, } @inproceedings{44132, abstract = {{Polarization dependent excitonic absorption changes have been studied recently for excitation with weak pump pulses [1]. It was shown, that for both resonant and off-resonant excitation even in the low-intensity χ(3)-limit many-body Coulomb correlations strongly contribute the optical response [1]. Here we investigate, how the coherent pump-induced absorption changes vary with the pump intensity, by analyzing the next higher, i.e. the fifth-order contributions.}}, author = {{Meier, Torsten and Koch, S.W. and Brick, P. and Ell, C. and Khitrova, G. and Gibbs, H.M.}}, booktitle = {{International Quantum Electronics Conference}}, isbn = {{0-7803-6318-3}}, location = {{Nice, France}}, publisher = {{IEEE}}, title = {{{Influence of correlations on intensity dependent excitonic absorption changes}}}, doi = {{10.1109/IQEC.2000.908034}}, year = {{2000}}, } @inproceedings{44133, abstract = {{by inherent disorder effects. Inhomogeneous broadening is the most obvious consequence of disorder and an inhomogeneously broadened exciton line might be considered as a superposition of homogeneously broadened subensembles of excitons. However, a possible coherent coustructures and lead to effects like disorder induced dephasing [1].}}, author = {{Meier, Torsten and Finger, E. and Kraft, S. and Euteneuer, A. and Hofmann, M. and Stolz, W. and Thomas, P. and Koch, S.W. and Rühle, W.W.}}, booktitle = {{International Quantum Electronics Conference}}, isbn = {{0-7803-6318-3}}, location = {{Nice, France}}, publisher = {{IEEE}}, title = {{{Coherent coupling in inhomogeneously broadened exciton ensembles}}}, doi = {{10.1109/IQEC.2000.908097}}, year = {{2000}}, } @article{43317, abstract = {{The intensity dependence of pump-induced excitonic absorption changes is studied in high-quality In0.04Ga0.96 As quantum wells for different detunings and polarization configurations. For resonant excitation with increasing pump intensity a saturation of both the exciton bleaching and the induced absorption due to two-exciton resonances is observed, whereas for pumping below the exciton a characteristic polarization dependence of higher-order contributions to the optical Stark effect is found. Microscopic calculations including Coulomb correlations show that the experimental observations can be described by the coherent dynamics of single- and two-exciton resonances up to fifth order in the optical field.}}, author = {{Meier, Torsten and Koch, S.W. and Brick, P. and Ell, C. and Khitrova, G. and Gibbs, H.M.}}, journal = {{Physical Review B}}, number = {{7}}, publisher = {{American Physical Society}}, title = {{{Signatures of Correlations in Intensity Dependent Excitonic Absorption Changes}}}, doi = {{10.1103/PhysRevB.62.4218}}, volume = {{62}}, year = {{2000}}, } @article{43323, abstract = {{The differential absorption of a GaAs single quantum well is studied for resonant pumping at either the heavy- or light-hole exciton resonances using different polarization configurations. For all excitation conditions the observed spectra show bleaching of both excitons, revealing strong coupling between the heavy- and light-hole excitons. Microscopic calculations which include four-particle correlations representing the various two-exciton states qualitatively reproduce the experimental findings. A mixed heavy-hole–light-hole biexciton is also clearly identified as an induced resonance in a GaAs system.}}, author = {{Meier, Torsten and Koch, S.W. and Phillips, M. and Wang, H.}}, journal = {{Physical Review B}}, number = {{19}}, publisher = {{American Physical Society}}, title = {{{Strong coupling of heavy- and light-hole excitons induced by many-body correlations}}}, doi = {{10.1103/PhysRevB.62.12605}}, volume = {{62}}, year = {{2000}}, } @article{43316, abstract = {{The phonon scattering assisted luminescence of semiconductor quantum well excitons after short pulse excitation is investigated. The presented analysis is based on the low-density limit of a set of equations for quantum correlation functions for electrons, phonons, and photons. The dynamics of the correlation functions describes the optical excitation and the decay of the coherent exciton polarization as well as the generation of an incoherent exciton occupation and its luminescence decay. Numerical solutions of the equations of motion demonstrate strong competition effects of the exciton-phonon and the exciton-photon interaction on a picosecond time scale and lead to a nonmonotonous temperature dependence of the time-resolved spontaneous emission. The angle resolved emission resembles the generation and decay dynamics of the exciton density for different in-plane momenta.}}, author = {{Meier, Torsten and Thränhardt, A. and Kuckenberg, S. and Knorr, A. and Koch, S.W.}}, journal = {{Physical Review B}}, number = {{4}}, pages = {{2706--2720}}, title = {{{Quantum theory of phonon-assisted exciton formation and luminescence in semiconductor quantum wells}}}, doi = {{10.1103/PhysRevB.62.2706}}, volume = {{62}}, year = {{2000}}, }