Integration of multi-junction absorbers and catalysts for efficient solar-driven artificial leaf structures : a physical and materials science perspective. - In: Solar RRL, ISSN 2367-198X, Bd. 0 (2024), 0, S. 1-88
Artificial leaves could be the breakthrough technology to overcome the limitations of storage and mobility through the synthesis of chemical fuels from sunlight, which will be an essential component of a sustainable future energy system. However, the realization of efficient solar-driven artificial leaf structures requires integrated specialized materials such as semiconductor absorbers, catalysts, interfacial passivation, and contact layers. To date, no competitive system has emerged due to a lack of scientific understanding, knowledge-based design rules, and scalable engineering strategies. Here, we will discuss competitive artificial leaf devices for water splitting, focusing on multi-absorber structures to achieve solar-to-hydrogen conversion efficiencies exceeding 15%. A key challenge is integrating photovoltaic and electrochemical functionalities in a single device. Additionally, optimal electrocatalysts for intermittent operation at photocurrent densities of 10-20 mA cm^-2 must be immobilized on the absorbers with specifically designed interfacial passivation and contact layers, so-called buried junctions. This minimizes voltage and current losses and prevents corrosive side reactions. Key challenges include understanding elementary steps, identifying suitable materials, and developing synthesis and processing techniques for all integrated components. This is crucial for efficient, robust, and scalable devices. Here, we discuss and report on corresponding research efforts to produce green hydrogen with unassisted solar-driven (photo-)electrochemical devices. This article is protected by copyright. All rights reserved.
https://doi.org/10.1002/solr.202301047
Efficient analytical evaluation of the singular BEM integrals for the three-dimensional Laplace and Stokes equations over polygonal elements. - In: Engineering analysis with boundary elements, ISSN 0955-7997, Bd. 161 (2024), S. 70-77
Singularities in the fundamental solutions pose a mathematical challenge for all applications of the boundary element method, if the source and field point lie on the same element. To avoid complex and error-prone numerical procedures, analytical solutions for the integrals that arise are desirable. In this work, easy and efficiently to implement analytical solutions are presented for the fundamental solutions of the three-dimensional Stokes equation as well as Laplace’s equation. Explicit expressions are derived for general triangular elements using constant shape functions. In addition, options for extending to arbitrary polygonal elements are shown. In particular, the three cases that the incenter, the centroid or the vertices of the triangles are used as source points for the calculation are addressed. The impressive numerical efficiency of the method is demonstrated by explicit examples.
https://doi.org/10.1016/j.enganabound.2024.01.013
Gold nanosponges: fascinating optical properties of a unique disorder-dominated system. - In: Journal of the Optical Society of America, ISSN 1520-8540, Bd. 40 (2023), 6, S. 1491-1509
Nanoporous gold is a three-dimensional bulk material that is percolated with a random network of nanometer-sized ligaments and made by selective corrosion of bimetallic alloys. It has intriguing geometric, catalytic, and optical properties that have fascinated scientists for many decades. When such a material is made into the form of small, 100-nm-sized particles, so-called nanosponges emerge that offer much flexibility in controlling their geometric, electronic, and optical properties. Importantly, these particles act as an antenna for light that can efficiently localize optical fields on a deep subwavelength scale in certain hotspots at the particle surface. This makes such nanosponges an interesting platform for plasmonic sensing, photocatalysis, and surface-enhanced Raman spectroscopy. Since the optical properties of these nanosponges can be controlled to a large degree by tuning their geometry and/or composition, they have attracted increasing attention in recent years. Here, we provide a concise overview of the current state of the art in this field, covering their fabrication, computational modeling, and specifically the linear and nonlinear optical properties of individual and hybrid nanosponges, for example, plasmon localization in randomly disordered hotspots with a size <10 nm and a long lifetime with an exceptionally high Purcell factor. The resulting nonlinear optical and photoemission properties are discussed for individual and hybrid nanosponges. The results presented have strong implications for further applications of such nanosponges in photonics and photocatalysis.
https://doi.org/10.1364/JOSAB.479739
Physics-guided machine learning techniques for improving temperature calculations of high-voltage transmission lines. - In: Die Energiewende beschleunigen, (2023), S. 353-360
The calculation of the temperature of high-voltage transmission lines is usually done by the commercially used standard models, the CIGRE Standard No. 601 and the IEEE Standard No. 738. These turn out to be prone to errors in application. Based on data analysis, new models based on machine learning techniques and their combination with physics-based models, called physics-guided machine learning techniques, were developed and compared with the results of the established physical models and measurement results. The improved models achieve a reduction of the mean absolute estimation error as well as a significant reduction of the values that deviate more than 5 K from the measured conductor temperature. Also, the mean underestimation of the conductor temperature was changed into an applicationtechnically unproblematic overestimation by the transition from the best standard to the best data-scientific model. The optimization of the models could be achieved by eliminating the incorrect determination of the physical parameters, a compensation of the conservative estimation of the physical effects as well as the consideration of the neglected thermal components of the heat balance. The investigations are based on measured data of the conductor temperature and electrical quantities from the grid area of 50Hertz Transmission GmbH.
3D passive microfluidic valves in silicon and glass using grayscale lithography and reactive ion etching transfer. - In: Microfluidics and nanofluidics, ISSN 1613-4990, Bd. 27 (2023), 8, 55, S. 1-12
A fabrication strategy for high-efficiency passive three-dimensional microfluidic valves with no mechanical parts fabricated in silicon and glass substrates is presented. 3D diffuser-nozzle valve structures were produced and characterized in their added value in comparison to conventional diffuser-nozzle valve designs with rectangular cross sections. A grayscale lithography approach for 3D photoresist structuring combined with a proportional transfer by reactive ion etching allowed to transfer 3D resist valve designs with high precision into the targeted substrate material. The efficiency with respect to the rectification characteristics or so-called diodicity of the studied valve designs is defined as the ratio of the pressure drops in backward and forward flow directions. The studied valve designs were characterized experimentally as well as numerically based on finite element simulations with overall matching results that demonstrate a significantly improved flow rectification of the 3D valves compared to the corresponding conventional structure. Our novel 3D valve structures show, for instance, even without systematic optimization a measured diodicity of up to 1.5 at low flow rates of only about 10 μl/s.
https://doi.org/10.1007/s10404-023-02663-2
Structural and optical properties of gold nanosponges revealed via 3D nano-reconstruction and phase-field models. - In: Communications materials, ISSN 2662-4443, Bd. 4 (2023), 1, 20, S. 1-13
Nanosponges are subject of intensive research due to their unique morphology, which leads among other effects to electrodynamic field localization generating a strongly nonlinear optical response at hot spots and thus enable a variety of applications. Accurate predictions of physical properties require detailed knowledge of the sponges’ chaotic nanometer-sized structure, posing a metrological challenge. A major goal is to obtain computer models with equivalent structural and optical properties. Here, to understand the sponges’ morphology, we present a procedure for their accurate 3D reconstruction using focused ion beam tomography. Additionally, we introduce a simulation method to create nanoporous sponge models with adjustable geometric properties. It is shown that if certain morphological parameters are similar for computer-generated and experimental sponges, their optical response, including magnitudes and hot spot locations, are also similar. Finally, we analyze the anisotropy of experimental sponges and present an easy-to-use method to reproduce arbitrary anisotropies in computer-generated sponges.
https://doi.org/10.1038/s43246-023-00346-7
Generalized modeling of photoluminescence transients. - In: Physica status solidi, ISSN 1521-3951, Bd. 260 (2023), 1, 2200339, S. 1-12
Time-resolved photoluminescence (TRPL) measurements and the extraction of meaningful parameters involve four key ingredients: a suitable sample such as a semiconductor double heterostructure, a state-of-the-art measurement setup, a kinetic model appropriate for the description of the sample behavior, and a general analysis method to extract the model parameters of interest from the measured TRPL transients. Until now, the last ingredient is limited to single curve fits, which are mostly based on simple models and least-squares fits. These are often insufficient for the parameter extraction in real-world applications. The goal of this article is to give the community a universal method for the analysis of TRPL measurements, which accounts for the Poisson distribution of photon counting events. The method can be used to fit multiple TRPL transients simultaneously using general kinematic models, but should also be used for single transient fits. To demonstrate this approach, multiple TRPL transients of a GaAs/AlGaAs heterostructure are fitted simultaneously using coupled rate equations. It is shown that the simultaneous fits of several TRPL traces supplemented by systematic error estimations allow for a more meaningful and more robust parameter determination. The statistical methods also quantify the quality of the description by the underlying physical model.
https://doi.org/10.1002/pssb.202200339
Multiphysics simulation of fluid interface shapes in microfluidic systems driven by electrowetting on dielectrics. - In: Journal of applied physics, ISSN 1089-7550, Bd. 132 (2022), 22, S. 224702-1-224702-17
We present a highly efficient simulation method for the calculation of three-dimensional quasi-static interface shapes under the influence of electric fields. The method is especially useful for the simulation of microfluidic systems driven by electrowetting on dielectrics because it accounts automatically and inherently for the highly non-trivial interface shape in the vicinity of the triple-phase contact. In particular, the voltage independence of the local contact angle predicted based on analytical considerations is correctly reproduced in all our simulations. For the calculation of the shape of the interface, the geometry is triangulated and the mesh nodes are shifted until the system energy becomes minimal. The same mesh is also used to calculate the electric field using the boundary-element method. Therefore, only the surface of the geometry needs to be meshed, and no volume meshes are involved. The method can be used for the simulation of closed systems with a constant volume (e.g., droplet-based microfluidics) while preserving the volume very precisely as well as open systems (e.g., the liquid-air interface within micro-cavities or capillaries). Additional effects, such as the influence of gravitational forces, can easily be taken into account. In contrast to other efficient simulations, such as the volume-of-fluid, level-set, or phase-field methods, ideally, sharp interfaces are obtained. We calculate interface shapes for exemplary systems and compare with analytical as well as experimental results.
https://doi.org/10.1063/5.0110149
P-terminated InP (001) surfaces: surface band bending and reactivity to water. - In: ACS applied materials & interfaces, ISSN 1944-8252, Bd. 14 (2022), 41, S. 47255-47261
Stable InP (001) surfaces are characterized by fully occupied and empty surface states close to the bulk valence and conduction band edges, respectively. The present photoemission data show, however, a surface Fermi level pinning only slightly below the midgap energy which gives rise to an appreciable surface band bending. By means of density functional theory calculations, it is shown that this apparent discrepancy is due to surface defects that form at finite temperature. In particular, the desorption of hydrogen from metalorganic vapor phase epitaxy grown P-rich InP (001) surfaces exposes partially filled P dangling bonds that give rise to band gap states. These defects are investigated with respect to surface reactivity in contact with molecular water by low-temperature water adsorption experiments using photoemission spectroscopy and are compared to our computational results. Interestingly, these hydrogen-related gap states are robust with respect to water adsorption, provided that water does not dissociate. Because significant water dissociation is expected to occur at steps rather than terraces, surface band bending of a flat InP (001) surface is not affected by water exposure.
https://doi.org/10.1021/acsami.2c13352
The ASi-Sii defect model of light-induced degradation (LID) in silicon: a discussion and review. - In: Physica status solidi, ISSN 1862-6319, Bd. 219 (2022), 19, 2200099, S. 1-10
The ASi-Sii defect model as one possible explanation for light-induced degradation (LID) in typically boron-doped silicon solar cells, detectors, and related systems is discussed and reviewed. Starting from the basic experiments which led to the ASi-Sii defect model, the ASi-Sii defect model (A: boron, or indium) is explained and contrasted to the assumption of a fast-diffusing so-called “boron interstitial.” An LID cycle of illumination and annealing is discussed within the conceptual frame of the ASi-Sii defect model. The dependence of the LID defect density on the interstitial oxygen concentration is explained within the ASi-Sii defect picture. By comparison of electron paramagnetic resonance data and minority carrier lifetime data related to the assumed fast diffusion of the “boron interstitial” and the annihilation of the fast LID component, respectively, the characteristic EPR signal Si-G28 in boron-doped silicon is related to a specific ASi-Sii defect state. Several other LID-related experiments are found to be consistent with an interpretation by an ASi-Sii defect.
https://doi.org/10.1002/pssa.202200099
Highly efficient passive Tesla valves for microfluidic applications. - In: Microsystems & nanoengineering, ISSN 2055-7434, Bd. 8 (2022), 1, 97, S. 1-12
A multistage optimization method is developed yielding Tesla valves that are efficient even at low flow rates, characteristic, e.g., for almost all microfluidic systems, where passive valves have intrinsic advantages over active ones. We report on optimized structures that show a diodicity of up to 1.8 already at flow rates of 20 μl s^-1 corresponding to a Reynolds number of 36. Centerpiece of the design is a topological optimization based on the finite element method. It is set-up to yield easy-to-fabricate valve structures with a small footprint that can be directly used in microfluidic systems. Our numerical two-dimensional optimization takes into account the finite height of the channel approximately by means of a so-called shallow-channel approximation. Based on the three-dimensionally extruded optimized designs, various test structures were fabricated using standard, widely available microsystem manufacturing techniques. The manufacturing process is described in detail since it can be used for the production of similar cost-effective microfluidic systems. For the experimentally fabricated chips, the efficiency of the different valve designs, i.e., the diodicity defined as the ratio of the measured pressure drops in backward and forward flow directions, respectively, is measured and compared to theoretical predictions obtained from full 3D calculations of the Tesla valves. Good agreement is found. In addition to the direct measurement of the diodicities, the flow profiles in the fabricated test structures are determined using a two-dimensional microscopic particle image velocimetry (μPIV) method. Again, a reasonable good agreement of the measured flow profiles with simulated predictions is observed.
https://doi.org/10.1038/s41378-022-00437-4
Reconstructions of the As-terminated GaAs(001) surface exposed to atomic hydrogen. - In: ACS omega, ISSN 2470-1343, Bd. 7 (2022), 6, S. 5064-5068
We explore the atomic structures and electronic properties of the As-terminated GaAs(001) surface in the presence of hydrogen based on ab initio density functional theory. We calculate a phase diagram dependent on the chemical potentials of As and H, showing which surface reconstruction is the most stable for a given set of chemical potentials. The findings are supported by the calculation of energy landscapes of the surfaces, which indicate possible H bonding sites as well as the density of states, which show the effect of hydrogen adsorption on the states near the fundamental band gap.
https://doi.org/10.1021/acsomega.1c06019
Physik-geführte NARXnets (PGNARXnets) zur Zeitreihenvorhersage. - In: Proceedings 31. Workshop Computational Intelligence, (2021), S. 235-261
Optical properties of nanoporous gold sponges using model structures obtained from three-dimensional phase-field Simulation. - In: 2021 Photonics & Electromagnetics Research Symposium (PIERS), (2021), S. 517-523
Nanoporous sponge structures show fascinating optical properties related to a strong spatial localization of field modes and a resulting strong field enhancement. In this work, a novel efficient method for the generation of three-dimensional nanoporous sponge structures using time-resolved phase-field simulations is presented. The algorithm for creating the geometries and the underlying equations are discussed. Different sponge geometries are generated and compared with sponges that have been experimentally measured using FIB tomography. Meaningful parameters are defined for the comparison of the geometric properties of the random sponge structures. In addition, the optical properties of the simulated sponges are compared with the experimentally measured sponges. It is shown that a description using effective media does not provide a good agreement to the actual spectra. This shows that the optical properties are largely determined by the local structures. In contrast, the numerically obtained spectra of the phase-field sponge models accounting for the real-space structure show excellent agreement with the spectra of the experimentally measured sponges.
https://doi.org/10.1109/PIERS53385.2021.9694971
Wafer-level fabrication of an EWOD-driven micropump. - In: MikroSystemTechnik, (2021), S. 574-577
Dimensioning and characterisation of an EWOD-driven chipintegrated micropump using time-resolved simulations. - In: MikroSystemTechnik, (2021), S. 531-534
Simulation model and dimensioning of a photoacoustic sensor for the detection of radiation-induced pressure surges. - In: MikroSystemTechnik, (2021), S. 523-526
Uphill and downhill charge generation from charge transfer to charge separated states in organic solar cells. - In: Journal of materials chemistry, ISSN 2050-7534, Bd. 9 (2021), 40, S. 14463-14489
It is common knowledge that molecular energy level offsets of a type II heterojunction formed at the donor-acceptor interface are considered to be the driving force for photoinduced charge transfer in organic solar cells. Usually, these offsets - present between molecular energy levels of the donor and acceptor - are obtained via cyclic voltammetry (CV) measurements of organic semiconductors cast in a film or dissolved in solution. Simply transferring such determined energy levels from solution or film of single materials to blend films may be obviously limited and not be possible in full generality. Herein, we report various cases of material combinations in which novel non-fullerene acceptors did not yield successful charge transfer, although energy levels obtained by CV on constituting single materials indicate a type II heterojunction. Whilst the integer charge transfer (ICT) model provides one explanation for a relative rise of molecular energy levels of acceptors, further details and other cases have not been studied so far in great detail. By applying energy-resolved electrochemical impedance spectroscopy (ER-EIS) on several donor-acceptor combinations, a Fano-like resonance feature associated with a distinctive molecular energy level of the acceptor as well as various relative molecular energy level shifts of different kinds could be observed. By analyzing ER-EIS and absorption spectra, not only the exciton binding energy within single materials could be determined, but also the commonly unknown binding energy of the CT state with regard to the joint density of states (jDOS) of the effective semiconductor. The latter is defined by transitions between the highest occupied molecular orbitals (HOMO) of the donor and the lowest unoccupied molecular orbitals (LUMO) of the acceptor. Using this technique among others, we identified cases in which charge generation may occur either via uphill or by downhill processes between the charge transfer exciton and the electronic gap of the effective semiconductor. Exceptionally high CT-exciton binding energies and thus low charge generation yields were obtained for a case in which the donor and acceptor yielded a too intimate blend morphology, indicating π-π stacking as a potential cause for unfavorable molecular energy level alignment.
https://doi.org/10.1039/D1TC02351A
InP and AlInP(001)(2 × 4) surface oxidation from density functional theory. - In: ACS omega, ISSN 2470-1343, Bd. 6 (2021), 9, S. 6297-6304
The atomic structure and electronic properties of the InP and Al0.5In0.5P(001) surfaces at the initial stages of oxidation are investigated via density functional theory. Thereby, we focus on the mixed-dimer (2 × 4) surfaces stable for cation-rich preparation conditions. For InP, the top In-P dimer is the most favored adsorption site, while it is the second-layer Al-Al dimer for AlInP. The energetically favored adsorption sites yield group III-O bond-related states in the energy region of the bulk band gap, which may act as recombination centers. Consistently, the In p state density around the conduction edge is found to be reduced upon oxidation.
https://doi.org/10.1021/acsomega.0c06019
Programmable multiple plasmonic resonances of nanoparticle superlattice for enhancing photoelectrochemical activity. - In: Advanced functional materials, ISSN 1616-3028, Bd. 30 (2020), 48, 2005170, insges. 10 S.
https://doi.org/10.1002/adfm.202005170
First-principles study of the structural and electronic properties of the GaAsxP1-x surface. - In: DPG-Frühjahrstagung (DPG Spring Meeting) of the Condensed Matter Section (SKM) together with the DPG Division Environmental Physics and the Working Groups Accelerator Physics; Equal Opportunities; Energy; Industry and Business; Physics, Modern IT and Artificial Intelligence, Young DPG, (2020), HL 6.9
Impact of the upcoming "Nationale Forschungsdaten Infrastruktur NFDI" on the SKM Community. - In: DPG-Frühjahrstagung (DPG Spring Meeting) of the Condensed Matter Section (SKM) together with the DPG Division Environmental Physics and the Working Groups Accelerator Physics; Equal Opportunities; Energy; Industry and Business; Physics, Modern IT and Artificial Intelligence, Young DPG, (2020), PSV III
Fluctuation-modulated third harmonic deep ultraviolet emission from randomly disordered Si nanograss. - In: DPG-Frühjahrstagung (DPG Spring Meeting) of the Condensed Matter Section (SKM) together with the DPG Division Environmental Physics and the Working Groups Accelerator Physics; Equal Opportunities; Energy; Industry and Business; Physics, Modern IT and Artificial Intelligence, Young DPG, (2020), O 18.10
Nonlinear plasmon-exciton coupling enhances sum-frequency generation from a Au/ZnO nanohybrid. - In: DPG-Frühjahrstagung (DPG Spring Meeting) of the Condensed Matter Section (SKM) together with the DPG Division Environmental Physics and the Working Groups Accelerator Physics; Equal Opportunities; Energy; Industry and Business; Physics, Modern IT and Artificial Intelligence, Young DPG, (2020), O 18.9
Improved numerical reconstruction method for Metastable Induced Electron Spectra of molecules. - In: DPG-Frühjahrstagung (DPG Spring Meeting) of the Condensed Matter Section (SKM) together with the DPG Division Environmental Physics and the Working Groups Accelerator Physics; Equal Opportunities; Energy; Industry and Business; Physics, Modern IT and Artificial Intelligence, Young DPG, (2020), O 48.6
Properties of effective potentials obtained within the Localisation Landscape Theory of random potentials. - In: DPG-Frühjahrstagung (DPG Spring Meeting) of the Condensed Matter Section (SKM) together with the DPG Division Environmental Physics and the Working Groups Accelerator Physics; Equal Opportunities; Energy; Industry and Business; Physics, Modern IT and Artificial Intelligence, Young DPG, (2020), TT 47.2
Investigation of sub-molecular parts in blends for organic solar cells. - In: DPG-Frühjahrstagung (DPG Spring Meeting) of the Condensed Matter Section (SKM) together with the DPG Division Environmental Physics and the Working Groups Accelerator Physics; Equal Opportunities; Energy; Industry and Business; Physics, Modern IT and Artificial Intelligence, Young DPG, (2020), CPP 73.1
Theoretical and numerical investigation of an EWOD-driven micro pump. - In: DPG-Frühjahrstagung (DPG Spring Meeting) of the Condensed Matter Section (SKM) together with the DPG Division Environmental Physics and the Working Groups Accelerator Physics; Equal Opportunities; Energy; Industry and Business; Physics, Modern IT and Artificial Intelligence, Young DPG, (2020), DY 45.2
Ab-initio reconstruction of metastable-induced electron-emission spectra (MIES) for molecules. - In: Nuclear instruments & methods in physics research, Bd. 478 (2020), S. 62-69
https://doi.org/10.1016/j.nimb.2020.05.006
Nonlinear plasmon-exciton coupling enhances sum-frequency generation from a hybrid metal/semiconductor nanostructure. - In: Nature Communications, ISSN 2041-1723, Bd. 11 (2020), 1464, S. 1-10
https://doi.org/10.1038/s41467-020-15232-w
Natural cavities with huge Purcell factors in gold nano sponges. - In: Quantum science and information technologies, (2019), FM 85.8
Modellierung, Fertigung und Erprobung einer neuartigen EWOD-betriebenen Mikropumpe. - In: MikroSystemTechnik Kongress 2019, (2019), S. 378-381
Doubly resonant plasmonic hot spot-exciton coupling enhances second harmonic generation from Au/ZnO hybrid porous nanosponges. - In: ACS photonics, ISSN 2330-4022, Bd. 6 (2019), 11, S. 2779-2787
https://doi.org/10.1021/acsphotonics.9b00791
Observing nonlinear plasmon-exciton coupling for enhanced harmonic generation. - In: 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC), (2019), insges. 1 S.
https://doi.org/10.1109/CLEOE-EQEC.2019.8872963
Strong spatial and spectral localization of surface plasmons in individual randomly disordered gold nanosponges. - In: DPG-Frühjahrstagung 2019 (DPG Spring Meeting 2019) of the Condensed Matter Section (SKM) together with the Division Radiation and Medical Physics and the Working Groups Equal Opportunities, Industry and Business, Young DPG; Symposia, exhibition of scientific instruments and literature, (2019), O 76.8
New reconstruction method for Metastable Induced Electron Spectra of molecules on solid surfaces. - In: DPG-Frühjahrstagung 2019 (DPG Spring Meeting 2019) of the Condensed Matter Section (SKM) together with the Division Radiation and Medical Physics and the Working Groups Equal Opportunities, Industry and Business, Young DPG; Symposia, exhibition of scientific instruments and literature, (2019), O 34.7
First-principles study of the structural and electronic properties of the GaP surface and GaP/Si interface. - In: DPG-Frühjahrstagung 2019 (DPG Spring Meeting 2019) of the Condensed Matter Section (SKM) together with the Division Radiation and Medical Physics and the Working Groups Equal Opportunities, Industry and Business, Young DPG; Symposia, exhibition of scientific instruments and literature, (2019), HL 35.32
Fast calculation method for determining the shape of static liquid/liquid or liquid/vapor interfaces under the influence of electrical fields. - In: DPG-Frühjahrstagung 2019 (DPG Spring Meeting 2019) of the Condensed Matter Section (SKM) together with the Division Radiation and Medical Physics and the Working Groups Equal Opportunities, Industry and Business, Young DPG; Symposia, exhibition of scientific instruments and literature, (2019), DY 54.10
Enhanced second harmonic emission from zinc oxide nanoparticles infiltrated into the pores of gold nanosponges. - In: DPG-Frühjahrstagung 2019 (DPG Spring Meeting 2019) of the Condensed Matter Section (SKM) together with the Division Radiation and Medical Physics and the Working Groups Equal Opportunities, Industry and Business, Young DPG; Symposia, exhibition of scientific instruments and literature, (2019), CPP 27.7
Auch enthalten in: O 31.7
Being a PhD candidate in physics. - In: DPG-Frühjahrstagung 2019 (DPG Spring Meeting 2019) of the Condensed Matter Section (SKM) together with the Division Radiation and Medical Physics and the Working Groups Equal Opportunities, Industry and Business, Young DPG; Symposia, exhibition of scientific instruments and literature, (2019), PSV VIII
Metalorganic vapor phase epitaxy of III-V-on-silicon: experiment and theory. - In: Progress in crystal growth and characterization of materials, ISSN 1878-4208, Bd. 64 (2018), 4, S. 103-132
https://doi.org/10.1016/j.pcrysgrow.2018.07.002
Mechanism of twin-reduced III-V epitaxy on As-modified vicinal Si(111). - In: Physical review materials, ISSN 2475-9953, Bd. 2 (2018), 12, S. 124601
https://doi.org/10.1103/PhysRevMaterials.2.124601
Zooming in on the surface: numerics for localization of light on coated nanosponges. - In: Joint Meeting of the DPG and EPS Condensed Matter Divisions together with the Statistical and Nonlinear Physics Division of the EPS and the Working Groups: Equal Opportunities, Industry and Business, Young DPG, Philosophy of Physics, (all DPG) EPS Young Minds, EPS History of Physics Group, (2018), O 25.2
Rotational twins in III-V/Si(111) virtual substrates and their impact on subsequent III-V nanowire growth. - In: Joint Meeting of the DPG and EPS Condensed Matter Divisions together with the Statistical and Nonlinear Physics Division of the EPS and the Working Groups: Equal Opportunities, Industry and Business, Young DPG, Philosophy of Physics, (all DPG) EPS Young Minds, EPS History of Physics Group, (2018), HL 33.25
Numerical calculations of metastable induced electron spectra (MIES). - In: Joint Meeting of the DPG and EPS Condensed Matter Divisions together with the Statistical and Nonlinear Physics Division of the EPS and the Working Groups: Equal Opportunities, Industry and Business, Young DPG, Philosophy of Physics, (all DPG) EPS Young Minds, EPS History of Physics Group, (2018), O 51.6
Functionalized nanoporous Au particles for enhanced optical nonlinearities. - In: Joint Meeting of the DPG and EPS Condensed Matter Divisions together with the Statistical and Nonlinear Physics Division of the EPS and the Working Groups: Equal Opportunities, Industry and Business, Young DPG, Philosophy of Physics, (all DPG) EPS Young Minds, EPS History of Physics Group, (2018), HL 52.5
Strong spatial and spectral localization of surface plasmons in individual randomly disordered gold nanosponges. - In: Nano letters, ISSN 1530-6992, Bd. 18 (2018), 8, S. 4957-4964
https://doi.org/10.1021/acs.nanolett.8b01785
Towards optimal disorder in gold nanosponges for long-lived localized plasmonic modes. - In: Annalen der Physik, ISSN 1521-3889, Bd. 529 (2017), 12, 1600234, S. 1-6
https://doi.org/10.1002/andp.201600234
Long-lived electron emission reveals localized plasmon modes in disordered nanosponge antennas. - In: Light, ISSN 2047-7538, Bd. 6 (2017), (20. Okt.), e17075, insges. 8 S.
We report long-lived, highly spatially localized plasmon states on the surface of nanoporous gold nanoparticles-nanosponges-with high excitation efficiency. It is well known that disorder on the nanometer scale, particularly in two-dimensional systems, can lead to plasmon localization and large field enhancements, which can, in turn, be used to enhance nonlinear optical effects and to study and exploit quantum optical processes. Here, we introduce promising, three-dimensional model systems for light capture and plasmon localization as gold nanosponges that are formed by the dewetting of gold/ silver bilayers and dealloying. We study light-induced electron emission from single nanosponges, a nonlinear process with exponents of n approximate to 5...7, using ultrashort laser pulse excitation to achieve femtosecond time resolution. The long-lived electron emission process proves, in combination with optical extinction measurements and finite-difference time-domain calculations, the existence of localized modes with lifetimes of more than 20 fs. These electrons couple efficiently to the dipole antenna mode of each individual nanosponge, which in turn couples to the far-field. Thus, individual gold nanosponges are cheap and robust disordered nanoantennas with strong local resonances, and an ensemble of nanosponges constitutes a meta material with a strong polarization independent, nonlinear response over a wide frequency range.
https://doi.org/10.1038/lsa.2017.75
Impact of rotational twin boundaries and lattice mismatch on III-V nanowire growth. - In: ACS nano, ISSN 1936-086X, Bd. 11 (2017), 9, S. 8679-8689
https://doi.org/10.1021/acsnano.7b01228
(The road to) understanding localization of light in nanosponges. - In: DPG-Frühjahrstagung (DPG Spring Meeting) of the Condensed Matter Section (SKM), (2017), O 28.10
Auch enthalten in: HL 39.10
Long-lived electron emission reveals ultra-localized plasmon modes in gold nanosponges. - In: DPG-Frühjahrstagung (DPG Spring Meeting) of the Condensed Matter Section (SKM), (2017), O 59.22
Formation of GaP rotational twins at the interface to Si(111). - In: DPG-Frühjahrstagung (DPG Spring Meeting) of the Condensed Matter Section (SKM), (2017), O 73.1
Impact of rotational twin boundaries of GaP/Si(111) substrates on III-V nanowire growth. - In: DPG-Frühjahrstagung (DPG Spring Meeting) of the Condensed Matter Section (SKM), (2017), HL 63.76
DFT study on the intercalation of fullerenes and AnE-PV copolymers. - In: DPG-Frühjahrstagung (DPG Spring Meeting) of the Condensed Matter Section (SKM), (2017), CPP 59.6
The importance of interface step configurations in the GaP/Si(111):As system: towards a growth model for twin domain formation. - In: DPG-Frühjahrstagung (DPG Spring Meeting) of the Condensed Matter Section (SKM), (2017), HL 84.9
Density functional study on the intercalation of fullerenes into AnE-PV copolymer layers. - In: The journal of physical chemistry. Biophysics, biomaterials, liquids, and soft matter. - Washington, DC : Americal Chemical Society, 1997- , ISSN: 1520-5207 , ZDB-ID: 2006039-7, ISSN 1520-5207, Bd. 121 (2017), 9, S. 2202-2206
https://doi.org/10.1021/acs.jpcb.6b12106
Thermodynamic stability of mixed Pb:Sn methylammonium halide perovskites. - In: 80th Annual Meeting of the DPG and DPG-Frühjahrstagung (Spring Meeting) of the Condensed Matter Section (SKM), (2016), CPP 11.5, insges. 1 S.
Electrodynamics of gold nano-sponges. - In: 80th Annual Meeting of the DPG and DPG-Frühjahrstagung (Spring Meeting) of the Condensed Matter Section (SKM), (2016), O 23.22, insges. 1 S.
Optoelectronic properties of mixed Pb:Sn methyl-ammonium halide perovskites. - In: 80th Annual Meeting of the DPG and DPG-Frühjahrstagung (Spring Meeting) of the Condensed Matter Section (SKM), (2016), CPP 11.6, insges. 1 S.
Mixed Pb:Sn methyl-ammonium halide perovskites: thermodynamic stability and optoelectronic properties. - In: 80th Annual Meeting of the DPG and DPG-Frühjahrstagung (Spring Meeting) of the Condensed Matter Section (SKM), (2016), CPP 21.6, insges. 1 S.
Analysis of the radiation-induced degradation of the ionic liquid [EMIm]Tf2N by use of quantum-chemical fragment calculations. - In: 80th Annual Meeting of the DPG and DPG-Frühjahrstagung (Spring Meeting) of the Condensed Matter Section (SKM), (2016), CPP 26.8, insges. 1 S.
Plasmon dynamics on nanoporous gold particles revealed by strong field photoemission. - In: 80th Annual Meeting of the DPG and DPG-Frühjahrstagung (Spring Meeting) of the Condensed Matter Section (SKM), (2016), O 52.10, insges. 1 S.
Influence of order and disorder on some photovoltaic properties of AnE-PV polymers - a DFT study. - In: 80th Annual Meeting of the DPG and DPG-Frühjahrstagung (Spring Meeting) of the Condensed Matter Section (SKM), (2016), CPP 62.1, insges. 1 S.
Thermodynamic stability of mixed Pb:Sn methyl-ammonium halide perovskites. - In: Physica status solidi. Basic solid state physics. - Weinheim : Wiley-VCH, [1971]- , ISSN: 1521-3951 , ZDB-ID: 1481096-7, ISSN 1521-3951, Bd. 253 (2016), 10, S. 1907-1915
http://dx.doi.org/10.1002/pssb.201600136
Density functional study of stacking structures and electronic behaviors of AnE-PV copolymer. - In: The journal of physical chemistry. Biophysics, biomaterials, liquids, and soft matter. - Washington, DC : Americal Chemical Society, 1997- , ISSN: 1520-5207 , ZDB-ID: 2006039-7, ISSN 1520-5207, Bd. 120 (2016), 41, S. 10854-10859
http://dx.doi.org/10.1021/acs.jpcb.6b07657
Near-field-assisted localization : effect of size and filling factor of randomly distributed zinc oxide nanoneedles on multiple scattering and localization of light. - In: Applied physics, ISSN 1432-0649, Bd. 122 (2016), 7, Article 181, insges. 11 S.
http://dx.doi.org/10.1007/s00340-016-6456-2
Effect of side chains on molecular conformation of anthracene-ethynylene-phenylene-vinylene oligomers: a comparative density functional study with and without dispersion interaction. - In: The journal of physical chemistry, ISSN 1520-5215, Bd. 120 (2016), 21, S. 3825-3841
http://dx.doi.org/10.1021/acs.jpca.6b01386
Theoretical reconstruction of photoelectron spectra and its application to ionic liquids. - Ilmenau : Universitätsbibliothek, 2016. - 1 Online-Ressource (198 Seiten)
Technische Universität Ilmenau, Dissertation 2016
Ionische Flüssigkeiten sind eine besondere Gruppe von Salzen, welche für Temperaturen unterhalb von 100 ˚C in flüssigem Aggregatzustand vorliegen und deren herausragende, einstellbare Eigenschaften zu einem breiten Anwendungsfeld führen. In der vorliegenden Arbeit wurde eine geeignete Rekonstruktionsmethode für die Röntgen- und Ultraviolett-Photoelektronenspektroskopie (XPS, UPS) von molekularen Systemen, zu welchen auch diese Flüssigkeiten zählen, entwickelt. Hierfür werden Atomorbital-spezifische Streuquerschnitte mit einer Intensitätsnäherung nach Gelius kombiniert. Diese Rekonstruktionsmethode baut auf quantenchemischen Berechnungen mittels Dichtefunktionaltheorie (DFT) unter Verwendung des Basissatzes 6-31G** und Hybrid-Funktion als B3-LYP auf. Zu diesem Zweck erfolgte die Berechnung von jeweils kleinsten bzw. kleinen ladungs- und spinkompensierten, molekularen Systemen für die anschließende Rekonstruktion. Die berechneten Bindungsenergien für die reinen ionischen Flüssigkeiten werden durch eine Reskalierung mit drei Parametern an die der experimentellen Spektren angepasst. Für jene Flüssigkeiten mit zusätzlichen Atomen oder Molekülen wird ein vierter Parameter eingeführt. Diese Methode findet für die Rekonstruktion von Rumpfniveau- und Valenzbandspektren von ionischen Flüssigkeiten Anwendung. Hierbei werden sowohl reine Imidazolium- und Pyrrolidinium-basierte ionische Flüssigkeiten als auch solche mit eingebauten Metallatomen oder aufgedampften Metall- bzw. Alkalimetallatomen untersucht. Die rekonstruierten Rumpfniveauspektren haben neuartige Einblicke in die chemische Umgebung, Wechselwirkungen zwischen den Ionen und Partialladungseffekte offenbart. Für die strahlungsinduzierte Degradation von ionischen Flüssigkeiten konnten deutliche Hinweise auf die zugrundeliegenden Mechanismen gewonnen werden. Der Vergleich zwischen experimentellen und rekonstruierten Spektren liefert erstmalig eine quantitative Bestimmung der ineinander verflochtenen Beiträge der einzelnen Ionen und der Elemente im Valenzband. Weiterhin lassen sich die Anordnung und Orientierung der Ionen und ihrer ausgewählten Bestandteile an der Oberfläche sowie deren bevorzugte Wechselwirkungen mittels der rekonstruierten Valenzbandspektren identifizieren.
http://www.db-thueringen.de/servlets/DocumentServlet?id=27395
Localization of light in ZnO nano-forests. - In: 79th Annual Meeting of the DPG and DPG-Frühjahrstagung (Spring Meeting) of the Condensed Matter Section (SKM) together with the Divisions: History of Physics, Gravitation and Relativity, Microprobes, Theoretical and Mathematical Physics, and Working Groups: Energy, Equal Opportunities, Information, Philosophy of Physics, Physics and Disarmament, young DPG ; March, 15 - 20, 2015, Technische Universität Berlin, 2015, O 50.9
Ab-initio calculation of scanning tunnelling spectra of Tin-Phthalocyanine multilayer structures. - In: 79th Annual Meeting of the DPG and DPG-Frühjahrstagung (Spring Meeting) of the Condensed Matter Section (SKM) together with the Divisions: History of Physics, Gravitation and Relativity, Microprobes, Theoretical and Mathematical Physics, and Working Groups: Energy, Equal Opportunities, Information, Philosophy of Physics, Physics and Disarmament, young DPG ; March, 15 - 20, 2015, Technische Universität Berlin, 2015, O 41.38
Plasmon-exciton coupling in stacked 2D perovskite semiconductors. - In: 79th Annual Meeting of the DPG and DPG-Frühjahrstagung (Spring Meeting) of the Condensed Matter Section (SKM) together with the Divisions: History of Physics, Gravitation and Relativity, Microprobes, Theoretical and Mathematical Physics, and Working Groups: Energy, Equal Opportunities, Information, Philosophy of Physics, Physics and Disarmament, young DPG ; March, 15 - 20, 2015, Technische Universität Berlin, 2015, HL 20.5
Quantum-chemical calculations of hybrid perovskites. - In: 79th Annual Meeting of the DPG and DPG-Frühjahrstagung (Spring Meeting) of the Condensed Matter Section (SKM) together with the Divisions: History of Physics, Gravitation and Relativity, Microprobes, Theoretical and Mathematical Physics, and Working Groups: Energy, Equal Opportunities, Information, Philosophy of Physics, Physics and Disarmament, young DPG ; March, 15 - 20, 2015, Technische Universität Berlin, 2015, CPP 60.8
Electronic and vibrational states of single tin-phthalocyanine molecules in double layers on Ag(111). - In: The journal of physical chemistry, ISSN 1932-7455, Bd. 119 (2015), 27, S. 15716-15722
Electronic and vibrational properties of the two stable molecular configurations of Sn-phthalocyanine adsorbed on an ultrathin Sn-phthalocyanine buffer film on Ag(111) have been investigated with scanning tunneling microscopy and density functional calculations. Complex submolecular patterns are experimentally observed in unoccupied states images. The calculations show that they result from a superposition of Sn p orbitals. Furthermore, the characteristic features in spectra of the differential conductance are reproduced by the calculations together with a remarkable difference between the two configurations. First-principles calculations show that rather than a single vibrational mode and its higher harmonics the excitations of different molecular vibrational quanta induce replica of orbital spectroscopic signatures. The replicated orbital features appear for the configuration with a low molecule-surface coupling. To model spectra of molecules with a larger coupling to the surface it is sufficient to consider elastic tunneling to orbital resonances alone.
https://doi.org/10.1021/acs.jpcc.5b03392
Origin of the individual basicity of corrole NH-tautomers: a quantum chemical study on molecular structure and dynamics, kinetics and thermodynamics. - In: The journal of physical chemistry, ISSN 1520-5215, Bd. 119 (2015), 26, S. 6875-6883
https://doi.org/10.1021/acs.jpca.5b02869
Image excitons and plasmon-exciton strong coupling in two-dimensional perovskite semiconductors. - In: Physical review. Condensed matter and materials physics / American Physical Society. - College Park, Md. : APS, 1970-2015 , ISSN: 1550-235X , ZDB-ID: 1473011-X, ISSN 1550-235X, Bd. 91 (2015), 16, S. 161303, insges. 5 S.
http://dx.doi.org/10.1103/PhysRevB.91.161303
Interaction of light and matter in metal-semiconductor hybrid nanostructures, 2015. - Online-Ressource (PDF-Datei: 98 S. S., 7,71 MB) Ilmenau : Techn. Univ., Diss., 2015
Ultraschnelle Nanooptik erforscht das Verhalten von Licht in nanostrukturierten Materialien auf Femtosekunden-Zeitskalen und könnte damit den nächste großen Durchbruch in der Datenverarbeitung bringen. Das Wissen aus diesem Forschungsbereich ist die Grundlage für zukünftige rein optische Schaltungstechnik, die Daten viel schneller als herkömmliche Elektronik verarbeiten kann. An nanostrukturierten Metalloberflächen können Oberflächenplasmonen (SPPs) angeregt werden. Dabei handelt es sich um kollektive Schwingungen des Elektronengases im Metall und des elektromagnetischen Feldes. SPPs können Licht auf einen räumlichen Bereich fokussieren der kleiner als das Abbe-Limit ist und propagieren immer entlang der Metalloberfläche. Damit sind sie als Informationsträger in nanooptischen Geräten besonders geeignet. Organische und anorganische Halbleiter sind eine weitere wichtige Komponente in nanooptischen Bauteilen. Sie ermöglichen die Licht-Licht und Licht-Materie Wechselwirkung, die notwendig ist, um Licht zu verstärken und zu schalten. Die vorliegende Arbeit beschreibt theoretische Berechnungen, die in enger Zusammenarbeit mit experimentellen Kollegen entstanden. Der Modellierungsprozeß, der eng mit der Wahl der numerischen Methoden in Zusammenhang steht, wird erörtert. Desweiteren werden Auswertungsmethoden beschrieben, die die numerischen Ergebnisse mit experimentell zugänglichen Größen verknüpfen. Die Ergebnisse der Berechnungen werden zuletzt experimentellen Ergebnissen vergleichend gegenübergestellt. In ihrem ersten Teil diskutiert die vorliegende Arbeit subtile Aspekte der Anregung von SPPs auf Metallgittern, bei denen die Symmetrie des Gitters von den einzelnen Streuern gebrochen wird. Thema des zweiten Teils der Arbeit ist ein Metallgitter, welches mit einem Farbstoff beschichtet wurde. In einem solchen System bilden SPPs und Exzitonen im Farbstoff kollektive, gekoppelte Moden, die auch Excimon oder Plexciton genannt werden. Dies kann an der vermiedenen Kreuzung der durch SPPs beziehungsweise Excitonen entstehenden Dips im winkelaufgelösten Reflektivitätsspektrum nachgewiesen werden. Im letzten Teil wird die Lokalisierung von Licht in Anordnungen von Zinkoxid Nanonaadeln diskutiert. Die Nanonaadeln sind dabei zufällig auf einem Substrat verteilt, stehen aber alle vertikal. Wegen ihres waldähnlichen Aussehens werden solche Anordnungen auch Nanowälder genannt. Einfallendes Licht erfährt in diesem System Vielfachstreuung an den Nanonaadeln. Es stellt sich heraus, dass ein Teil des Lichtes lokalisiert wird - es wird im Nanowald gefangen.
http://www.db-thueringen.de/servlets/DocumentServlet?id=26069
Quantum chemical insights into the dependence of porphyrin basicity on the meso-aryl substituents: thermodynamics, buckling, reaction sites and molecular flexibility. - In: Physical chemistry, chemical physics, ISSN 1463-9084, Bd. 17 (2015), 21, S. 14096-14106
http://dx.doi.org/10.1039/c5cp01808k
Smoothing and regularization strategies for optimization of hybrid dynamic systems. - In: Optimization and engineering, ISSN 1573-2924, Bd. 16 (2015), 3, S. 541-569
https://doi.org/10.1007/s11081-014-9261-y
Atom-by-atom dehalogenation of a porphyrin molecule adsorbed on Ag(111). - In: The journal of physical chemistry, ISSN 1932-7455, Bd. 118 (2014), 51, S. 30162-30169
Porphyrin molecules are ubiquitous and play an important role in chemical and biological processes. Their wide panoply of functions may be controlled by modifying their peripheral substituents. Electron injection from the tip of a scanning tunneling microscope into single 5,10,15,20-tetrakis(4-bromophenyl)-porphyrin-cobalt molecules adsorbed to Ag(111) was used to controllably remove Br atoms from the molecule periphery. Spectroscopy of the differential conductance, together with density functional calculations, assign spectral features to the spectroscopic signatures of molecular frontier orbitals. Different molecular orbitals are visible in the spectra of intact and dehalogenated molecules. These findings combine single-molecule chemistry with a characterization of each product's electronic structure.
http://dx.doi.org/10.1021/jp508165c
Steric and electronic contributions to the core reactivity of monoprotonated 5-phenylporphyrin: a DFT study. - In: Chemical physics letters, Bd. 603 (2014), S. 21-27
http://dx.doi.org/10.1016/j.cplett.2014.04.011
Optical spectroscopy of photovoltaic systems based on low-bandgap polymers. - In: Thin solid films, ISSN 1879-2731, Bd. 560 (2014), S. 77-81
http://dx.doi.org/10.1016/j.tsf.2013.11.025
Quantumchemical calculation of Zn-porphyrine-indolocarbazole-conjugates. - In: DPG-Frühjahrstagung (DPG Spring Meeting) of the Condensed Matter Section [SKM] together with the DPG Divisions: Microprobes, the Working Groups: Industry and Business, young DPG as well as the Committee Accelerator Physics ; March 30 - April 4, 2014, Technical University of Dresden, 2014, CPP 8.1
Photoelectron spectroscopy on ionic liquid surfaces - theory and experiment. - In: DPG-Frühjahrstagung (DPG Spring Meeting) of the Condensed Matter Section [SKM] together with the DPG Divisions: Microprobes, the Working Groups: Industry and Business, young DPG as well as the Committee Accelerator Physics ; March 30 - April 4, 2014, Technical University of Dresden, 2014, CPP 19.3
Ab-inito MD parameter estimation for Na diffusion in glasses. - In: DPG-Frühjahrstagung (DPG Spring Meeting) of the Condensed Matter Section [SKM] together with the DPG Divisions: Microprobes, the Working Groups: Industry and Business, young DPG as well as the Committee Accelerator Physics ; March 30 - April 4, 2014, Technical University of Dresden, 2014, DY 13.7
Optimizing binary profiles for metallic solar cell back-plane reflectors. - In: DPG-Frühjahrstagung (DPG Spring Meeting) of the Condensed Matter Section [SKM] together with the DPG Divisions: Microprobes, the Working Groups: Industry and Business, young DPG as well as the Committee Accelerator Physics ; March 30 - April 4, 2014, Technical University of Dresden, 2014, HL 81.6
Ab-initio calculation of the vibrational spectra of single molecules. - In: DPG-Frühjahrstagung (DPG Spring Meeting) of the Condensed Matter Section [SKM] together with the DPG Divisions: Microprobes, the Working Groups: Industry and Business, young DPG as well as the Committee Accelerator Physics ; March 30 - April 4, 2014, Technical University of Dresden, 2014, O 63.6
Coupled photon-exciton modes in CHPI-based devices. - In: DPG-Frühjahrstagung (DPG Spring Meeting) of the Condensed Matter Section [SKM] together with the DPG Divisions: Microprobes, the Working Groups: Industry and Business, young DPG as well as the Committee Accelerator Physics ; March 30 - April 4, 2014, Technical University of Dresden, 2014, O 79.9
Photoelectron spectroscopy on ionic liquid surfaces - theory and experiment. - In: Journal of molecular liquids, ISSN 1873-3166, Bd. 192 (2014), S. 77-86
http://dx.doi.org/10.1016/j.molliq.2014.01.007
Excitons and exciton-phonon coupling in the optical response of GaN. - In: Physica status solidi. Current topics in solid state physics. - Berlin : Wiley-VCH, 2002-2017 , ISSN: 1610-1642 , ZDB-ID: 2102966-0, ISSN 1610-1642, Bd. 11 (2014), 2, S. 297-301
http://dx.doi.org/10.1002/pssc.201300311
Molecular structures and absorption spectra assignment of corrole NH tautomers. - In: The journal of physical chemistry, ISSN 1520-5215, Bd. 118 (2014), 5, S. 862-871
https://doi.org/10.1021/jp411033h
Observing the localization of light in space and time by ultrafast second-harmonic microscopy. - In: DPG-Frühjahrstagung (DPG Spring Meeting) of the Condensed Matter Section [SKM], with its Divisions: Biological Physics, Chemical and Polymer Physics, Crystallography, Dielectric Solids, Dynamics and Statistical Physics, Low Temperature Physics, Magnetism, Metal and Material Physics, Physics of Socio-Economic Systems, Semiconductor Physics, Surface Science, Thin Fils, Vacuum Science and Technology, together with the Divisions: Microprobes, and Radiation and Medical Physics as well as the Working Groups: Industry and Business, and "Young DPG" ; March 10 - 15, 2013, University of Regensburg, 2013, O 36.35
Impact of 2D structures on the back surface of solar cells on the absorption processes in these cells. - In: DPG-Frühjahrstagung (DPG Spring Meeting) of the Condensed Matter Section [SKM], with its Divisions: Biological Physics, Chemical and Polymer Physics, Crystallography, Dielectric Solids, Dynamics and Statistical Physics, Low Temperature Physics, Magnetism, Metal and Material Physics, Physics of Socio-Economic Systems, Semiconductor Physics, Surface Science, Thin Fils, Vacuum Science and Technology, together with the Divisions: Microprobes, and Radiation and Medical Physics as well as the Working Groups: Industry and Business, and "Young DPG" ; March 10 - 15, 2013, University of Regensburg, 2013, O 36.7
Ultrafast local dynamics of two-dimensional light modes. - In: DPG-Frühjahrstagung (DPG Spring Meeting) of the Condensed Matter Section [SKM], with its Divisions: Biological Physics, Chemical and Polymer Physics, Crystallography, Dielectric Solids, Dynamics and Statistical Physics, Low Temperature Physics, Magnetism, Metal and Material Physics, Physics of Socio-Economic Systems, Semiconductor Physics, Surface Science, Thin Fils, Vacuum Science and Technology, together with the Divisions: Microprobes, and Radiation and Medical Physics as well as the Working Groups: Industry and Business, and "Young DPG" ; March 10 - 15, 2013, University of Regensburg, 2013, O 36.34
Sub-bandgap absorption in polythiophene-fullerene heterojunctions: experiment and theory. - In: DPG-Frühjahrstagung (DPG Spring Meeting) of the Condensed Matter Section [SKM], with its Divisions: Biological Physics, Chemical and Polymer Physics, Crystallography, Dielectric Solids, Dynamics and Statistical Physics, Low Temperature Physics, Magnetism, Metal and Material Physics, Physics of Socio-Economic Systems, Semiconductor Physics, Surface Science, Thin Fils, Vacuum Science and Technology, together with the Divisions: Microprobes, and Radiation and Medical Physics as well as the Working Groups: Industry and Business, and "Young DPG" ; March 10 - 15, 2013, University of Regensburg, 2013, CPP 39.8
Effect of size and shape of randomly distributed ZnO nanoneedle arrays on the localization of light fields. - In: DPG-Frühjahrstagung (DPG Spring Meeting) of the Condensed Matter Section [SKM], with its Divisions: Biological Physics, Chemical and Polymer Physics, Crystallography, Dielectric Solids, Dynamics and Statistical Physics, Low Temperature Physics, Magnetism, Metal and Material Physics, Physics of Socio-Economic Systems, Semiconductor Physics, Surface Science, Thin Fils, Vacuum Science and Technology, together with the Divisions: Microprobes, and Radiation and Medical Physics as well as the Working Groups: Industry and Business, and "Young DPG" ; March 10 - 15, 2013, University of Regensburg, 2013, O 86.8
Sub-bandgap absorption in organic solar cells: experiment and theory. - In: Physical chemistry, chemical physics, ISSN 1463-9084, Bd. 15 (2013), 39, S. 16494-16502
http://dx.doi.org/10.1039/C3CP42236D
Multivalence-band calculation of the excitonic dielectric function for hexagonal GaN. - In: Journal of physics, ISSN 1361-648X, Bd. 25 (2013), 17, S. 175801, insges. 12 S.
http://dx.doi.org/10.1088/0953-8984/25/17/175801
Strain-induced topological insulator phase transition in HgSe. - In: Physical review. Condensed matter and materials physics / American Physical Society. - College Park, Md. : APS, 1970-2015 , ISSN: 1550-235X , ZDB-ID: 1473011-X, ISSN 1550-235X, Bd. 87 (2013), 7, S. 075143, insges. 7 S.
http://dx.doi.org/10.1103/PhysRevB.87.075143
Entanglement enhancement in spatially inhomogeneous many-body systems. - In: Physical review. Atomic, molecular, and optical physics / American Physical Society. - College Park, Md. : [Verlag nicht ermittelbar], 1970-2015 , ISSN: 1094-1622 , ZDB-ID: 1472694-4, ISSN 1094-1622, Bd. 87 (2013), 3, S. 032311, insges. 5 S.
http://dx.doi.org/10.1103/PhysRevA.87.032311
Ultrafast dynamics of localized light modes. - In: Annalen der Physik, ISSN 1521-3889, Bd. 525 (2013), 1/2, S. 199-204
Multiple coherent scattering gives rise to a variety of localization phenomena. However, the localization of electromagnetic waves is notoriously hard to observe. Here, hotspots found in optical wavefunctions in the visible range in random zinc-oxide nano-needle arrays are discussed. In particular, results from 3D and 2D calculations of light localization in random arrays of dielectric cylinders are compared. While 3D calculations with periodic boundary conditions reproduce various aspects of the experimental results very well, open boundary 2D calculations proof the coexistence of propagating and lossy localized modes showing distinct hot-spots.
http://dx.doi.org/10.1002/andp.201200228
Simulation, parameter estimation and optimization of an industrial-scale evaporation system. - In: Simulation and modeling methodologies, technologies and applications, (2013), S. 71-84
Design and operation of complex industrial systems can be improved based on simulation and optimization using physical process models. However, this endeavor is particularly challenging for hybrid systems, where in addition to the continuous evolution described by differential algebraic equations the dynamic process shows instantaneous switches between different operating modes. In this study, we consider parameter estimation for an industrial evaporation system with discrete mode switches due to phase transitions. Simulation results of the hybrid evaporator model are compared with those of a smooth evaporator model. A smoothing approach is applied in order to modify the hybrid model such that the discrete transitions are integrated into the system of differential algebraic equations. This leads to exclusively smooth trajectories, making the model suitable for parameter estimation to be solved by means of gradient-based optimization methods. The dependence of the parameter estimation results on the smoothing parameter is investigated. Keywords: Parameter estimation, Nonlinear dynamic optimization, Large-scale hybrid systems.
Enhancement of block-block entanglement due to localized impurities in the 1D Fermi-Hubbard model. - In: DPG-Frühjahrstagung, spring meeting of the Section AMOP (SAMOP) with the Divisions Atomic Physics, Extraterrestrial Physics, Mass Spectrometry, Molecular Physics, Plasma Physics, Quantum Optics and Photonics, Short Time-scale Physics, 2012, Q 54.78
Trapping light in random ZnO nanorod arrays - localization of light in space and time. - In: 76th Jahrestagung der DPG (76th annual conference of the DPG) and DPG-Frühjahrstagung (spring meeting) of the Condensed Matter Section (SKM) with further DPG Divisions: Environmental Physics, Microprobes, Radiation and Medical Physics, as well as the DPG working groups: Energy, Equal Opportunities, Industry and Business, Information, Philosophy of Physics, Physics and Disarmament, young DPG ; March 25 - 30, 2012, Technische Universität Berlin, 2012, O 3.4
Investigation of parametrizations for the valence band structure of GaN. - In: 76th Jahrestagung der DPG (76th annual conference of the DPG) and DPG-Frühjahrstagung (spring meeting) of the Condensed Matter Section (SKM) with further DPG Divisions: Environmental Physics, Microprobes, Radiation and Medical Physics, as well as the DPG working groups: Energy, Equal Opportunities, Industry and Business, Information, Philosophy of Physics, Physics and Disarmament, young DPG ; March 25 - 30, 2012, Technische Universität Berlin, 2012, HL 25.8
Electron spectroscopy study of the interaction of copper with [EMIm]Tf 2 N under the influence of aerobic conditions. - In: 76th Jahrestagung der DPG (76th annual conference of the DPG) and DPG-Frühjahrstagung (spring meeting) of the Condensed Matter Section (SKM) with further DPG Divisions: Environmental Physics, Microprobes, Radiation and Medical Physics, as well as the DPG working groups: Energy, Equal Opportunities, Industry and Business, Information, Philosophy of Physics, Physics and Disarmament, young DPG ; March 25 - 30, 2012, Technische Universität Berlin, 2012, CPP 16.32
DFT-reconstructed photoelectron spectra for metals in ionic liquids. - In: 76th Jahrestagung der DPG (76th annual conference of the DPG) and DPG-Frühjahrstagung (spring meeting) of the Condensed Matter Section (SKM) with further DPG Divisions: Environmental Physics, Microprobes, Radiation and Medical Physics, as well as the DPG working groups: Energy, Equal Opportunities, Industry and Business, Information, Philosophy of Physics, Physics and Disarmament, young DPG ; March 25 - 30, 2012, Technische Universität Berlin, 2012, CPP 16.46
Coherent control of the electron emission from metal nanotips due to ultrashort laser pulses. - In: 76th Jahrestagung der DPG (76th annual conference of the DPG) and DPG-Frühjahrstagung (spring meeting) of the Condensed Matter Section (SKM) with further DPG Divisions: Environmental Physics, Microprobes, Radiation and Medical Physics, as well as the DPG working groups: Energy, Equal Opportunities, Industry and Business, Information, Philosophy of Physics, Physics and Disarmament, young DPG ; March 25 - 30, 2012, Technische Universität Berlin, 2012, O 34.59
Far-field control of optical near-field enhancement. - In: 76th Jahrestagung der DPG (76th annual conference of the DPG) and DPG-Frühjahrstagung (spring meeting) of the Condensed Matter Section (SKM) with further DPG Divisions: Environmental Physics, Microprobes, Radiation and Medical Physics, as well as the DPG working groups: Energy, Equal Opportunities, Industry and Business, Information, Philosophy of Physics, Physics and Disarmament, young DPG ; March 25 - 30, 2012, Technische Universität Berlin, 2012, O 34.60
Localization of light-modes in disordered ZnO nanoneedle-arrays. - In: 76th Jahrestagung der DPG (76th annual conference of the DPG) and DPG-Frühjahrstagung (spring meeting) of the Condensed Matter Section (SKM) with further DPG Divisions: Environmental Physics, Microprobes, Radiation and Medical Physics, as well as the DPG working groups: Energy, Equal Opportunities, Industry and Business, Information, Philosophy of Physics, Physics and Disarmament, young DPG ; March 25 - 30, 2012, Technische Universität Berlin, 2012, HL 49.4
Origin of sub-bandgap absorption in P3HT:PCBM solar cells. - In: 76th Jahrestagung der DPG (76th annual conference of the DPG) and DPG-Frühjahrstagung (spring meeting) of the Condensed Matter Section (SKM) with further DPG Divisions: Environmental Physics, Microprobes, Radiation and Medical Physics, as well as the DPG working groups: Energy, Equal Opportunities, Industry and Business, Information, Philosophy of Physics, Physics and Disarmament, young DPG ; March 25 - 30, 2012, Technische Universität Berlin, 2012, CPP 18.6
The influence of meso-phenyl torsion on the chemical properties of porphyrine. - In: 76th Jahrestagung der DPG (76th annual conference of the DPG) and DPG-Frühjahrstagung (spring meeting) of the Condensed Matter Section (SKM) with further DPG Divisions: Environmental Physics, Microprobes, Radiation and Medical Physics, as well as the DPG working groups: Energy, Equal Opportunities, Industry and Business, Information, Philosophy of Physics, Physics and Disarmament, young DPG ; March 25 - 30, 2012, Technische Universität Berlin, 2012, CPP 24.20
Tuning the light induced charge separation in Ru(II) terpyridine complexes: a quantum chemical study. - In: 76th Jahrestagung der DPG (76th annual conference of the DPG) and DPG-Frühjahrstagung (spring meeting) of the Condensed Matter Section (SKM) with further DPG Divisions: Environmental Physics, Microprobes, Radiation and Medical Physics, as well as the DPG working groups: Energy, Equal Opportunities, Industry and Business, Information, Philosophy of Physics, Physics and Disarmament, young DPG ; March 25 - 30, 2012, Technische Universität Berlin, 2012, CPP 24.21
Coherent exciton-plasmon coupling in metal-dye hybrid nanostructures. - In: 76th Jahrestagung der DPG (76th annual conference of the DPG) and DPG-Frühjahrstagung (spring meeting) of the Condensed Matter Section (SKM) with further DPG Divisions: Environmental Physics, Microprobes, Radiation and Medical Physics, as well as the DPG working groups: Energy, Equal Opportunities, Industry and Business, Information, Philosophy of Physics, Physics and Disarmament, young DPG ; March 25 - 30, 2012, Technische Universität Berlin, 2012, O 40.2
A quantum chemical study of the dependency of absorption properties on meso-substituent conformations of two different corrole NH-tautomers. - In: 76th Jahrestagung der DPG (76th annual conference of the DPG) and DPG-Frühjahrstagung (spring meeting) of the Condensed Matter Section (SKM) with further DPG Divisions: Environmental Physics, Microprobes, Radiation and Medical Physics, as well as the DPG working groups: Energy, Equal Opportunities, Industry and Business, Information, Philosophy of Physics, Physics and Disarmament, young DPG ; March 25 - 30, 2012, Technische Universität Berlin, 2012, CPP 24.24
Synthesis and characterization of organically linked ZnO nanoparticles. - In: Physica status solidi, ISSN 1862-6319, Bd. 209 (2012), 11, S. 2212-2216
http://dx.doi.org/10.1002/pssa.201228205
Origin of sub-bandgap absorption in P3HT: PCBM solar cells. - In: Proceedings, (2012), S. 124
Parallel als Druckausg. erschienen
http://www.db-thueringen.de/servlets/DocumentServlet?id=20839
Influence of organic acids on device performance of P3HT : PCBM solar cells. - In: Proceedings, (2012), S. 164
Parallel als Druckausg. erschienen
http://www.db-thueringen.de/servlets/DocumentServlet?id=20839
Influence of phonon scattering on exciton and charge diffusion in polymer-fullerene solar cells. - In: Advanced energy materials, ISSN 1614-6840, Bd. 2 (2012), 8, S. 999-1003
http://dx.doi.org/10.1002/aenm.201100793
Sub-bandgap absorption in polymer-fullerene solar cells studied by temperature-dependent external quantum efficiency and absorption spectroscopy. - In: Chemical physics letters, Bd. 542 (2012), S. 70-73
http://dx.doi.org/10.1016/j.cplett.2012.05.063
Observing the localization of light in space and time by ultrafast second-harmonic microscopy. - In: Nature photonics, ISSN 1749-4893, Bd. 6 (2012), 5, S. 293-298
http://dx.doi.org/10.1038/nphoton.2012.69
Surface electronic structure of [XMIm]Cl probed by surface-sensitive spectroscopy. - In: ChemPhysChem, ISSN 1439-7641, Bd. 13 (2012), 7, S. 1718-1724
http://dx.doi.org/10.1002/cphc.201100972
Direct observation of optical excitation transfer based on resonant optical near-field interaction. - In: Applied physics. Lasers and optics. - Berlin : Springer, 1981- , ISSN: 1432-0649 , ZDB-ID: 1458437-2, ISSN 1432-0649, Bd. 107 (2012), 2, S. 257-262
http://dx.doi.org/10.1007/s00340-012-5009-6
Correlation between near infrared-visible absorption, intrinsic local and global sheet resistance of poly(3,4-ethylenedioxy-thiophene) poly(styrene sulfonate) thin films. - In: Applied physics letters, ISSN 1077-3118, Bd. 100 (2012), 15, S. 253301, insges. 3 S.
http://dx.doi.org/10.1063/1.3697402
Voltage-induced adsorbate damping of single gold nanorod plasmons in aqueous solution. - In: Nano letters, ISSN 1530-6992, Bd. 12 (2012), 3, S. 1247-1252
http://dx.doi.org/10.1021/nl203673g
Valence band structure of cellulose and lignin studied by XPS and DFT. - In: Cellulose, ISSN 1572-882X, Bd. 19 (2012), 3, S. 1005-1011
http://dx.doi.org/10.1007/s10570-012-9681-9
Parameter estimation of an industrial evaporator with hybrid dynamics by a smoothing approach. - In: Proceedings of 1st International Conference on Simulation and Modeling Methodologies, Technologies and Applications, ISBN 978-989-8425-78-2, (2011), S. 31-36
First-principles GW calculations for the DNA/RNA nucleobases and for molecules of interest for organic photovoltaics. - In: 75th Annual Meeting of the DPG and combined DPG Spring Meeting of the Condensed Matter Section and the Section AMOP, 2011, MO 2.5
Theoretical reconstruction of photoelectron-spectra for imidazolium-based ionic liquids. - In: 75th Annual Meeting of the DPG and combined DPG Spring Meeting of the Condensed Matter Section and the Section AMOP, 2011, CPP 6.3
Systematic analysis of the surface structure of ionic liquids using sum frequency generation (SFG). - In: 75th Annual Meeting of the DPG and combined DPG Spring Meeting of the Condensed Matter Section and the Section AMOP, 2011, CPP 6.4
Sub-bandgap absorption in polymer-fullerene solar cells. - In: 75th Annual Meeting of the DPG and combined DPG Spring Meeting of the Condensed Matter Section and the Section AMOP, 2011, CPP 12.3
Richtiger Name des Verf.: Harald Hoppe
Ultrafast optical nonlinearities in hybrid metal-semiconductor nanostructures. - In: 75th Annual Meeting of the DPG and combined DPG Spring Meeting of the Condensed Matter Section and the Section AMOP, 2011, O 41.3
Characteristics of the electron emission from metal nano-tips due to ultrashort laser pulses. - In: 75th Annual Meeting of the DPG and combined DPG Spring Meeting of the Condensed Matter Section and the Section AMOP, 2011, O 41.4
Localization of light in ZnO nano-needle arrays/ David Leipold; Christoph Minz and Erich Runge. - In: 75th Annual Meeting of the DPG and combined DPG Spring Meeting of the Condensed Matter Section and the Section AMOP, 2011, HL 57.1
Multi-plasmon enhancement of thin film organic solar cells. - In: 75th Annual Meeting of the DPG and combined DPG Spring Meeting of the Condensed Matter Section and the Section AMOP, 2011, O 59.10
Coupled exciton-plasmon modes in metal-dye hybrid systems. - In: 75th Annual Meeting of the DPG and combined DPG Spring Meeting of the Condensed Matter Section and the Section AMOP, 2011, O 60.75
Weak localization of light in ZnO nanorods in space and time. - In: 75th Annual Meeting of the DPG and combined DPG Spring Meeting of the Condensed Matter Section and the Section AMOP, 2011, O 76.3
Measured and simulated valence band structure of cellulose and lignin. - In: 75th Annual Meeting of the DPG and combined DPG Spring Meeting of the Condensed Matter Section and the Section AMOP, 2011, BP 29.12
Statistical properties of photon modes in random arrays of ZnO nano-needles. - In: 75th Annual Meeting of the DPG and combined DPG Spring Meeting of the Condensed Matter Section and the Section AMOP, 2011, HL 85.13
Ultrafast manipulation of the large Rabi splitting in metal-J-aggregate hybrid nanostructures. - In: Conference on Lasers and Electro-Optics Europe and 12th European Quantum Electronics Conference (CLEO Europe/EQEC), 2011, ISBN 978-1-4577-0533-5, (2011), insges. 1 S.
Richtiger Name des Verf.: Giovanni Cirmi
http://dx.doi.org/10.1109/CLEOE.2011.5943637
Ruthenium(II)-bis(4-(4-ethynylphenyl)-2,2:6, 2-terpyridine) - a versatile synthon in supramolecular chemistry : synthesis and characterization. - In: Central European journal of chemistry, ISSN 1644-3624, Bd. 9 (2011), 6, S. 990-999
http://dx.doi.org/10.2478/s11532-011-0087-6
The design of efficient surface-plasmon-enhanced ultra-thin polymer-based solar cells. - In: Applied physics letters, ISSN 1077-3118, Bd. 99 (2011), 9, S. 093307, insges. 3 S.
http://dx.doi.org/10.1063/1.3633349
Elektrisch geschaltete Mikrofluidsegmente für die "Segment-on-Demand"-Technik. - In: Proceedings, (2011), S. 70-73
Electron-phonon coupling in the C60 fullerene within the many-body GW approach. - In: Physical review. Condensed matter and materials physics / American Physical Society. - College Park, Md. : APS, 1970-2015 , ISSN: 1550-235X , ZDB-ID: 1473011-X, ISSN 1550-235X, Bd. 84 (2011), 15, S. 155104, insges. 5 S.
http://dx.doi.org/10.1103/PhysRevB.84.155104
Theoretical reconstruction and elementwise analysis of photoelectron spectra for imidazolium-based ionic liquids. - In: Physical chemistry, chemical physics, ISSN 1463-9084, Bd. 13 (2011), 43, S. 19526-19533
http://dx.doi.org/10.1039/C1CP22152C
Ultrafast manipulation of the Rabi splitting in metal-molecular aggregate hybrid nanostructures. - In: Physica status solidi, ISSN 1610-1642, Bd. 8 (2011), 4, S. 1113-1116
http://dx.doi.org/10.1002/pssc.201000858
Metal-mediated reaction modeled on nature: the activation of isothiocyanates initiated by zinc thiolate complexes. - In: Inorganic chemistry, ISSN 1520-510X, Bd. 50 (2011), 8, S. 3223-3233
http://dx.doi.org/10.1021/ic101464j
Localizing few-cycle light pulses in space and time in random dielectric media. - In: Ultrafast phenomena XVII, (2011), S. 643-645
Excitons in conjugated polymers : a theoretical study based on quantum chemistry. - 162 S. Ilmenau : Techn. Univ., Habil.-Schr., 2011
First-principles GW calculations for DNA and RNA nucleobases. - In: Physical review. Condensed matter and materials physics / American Physical Society. - College Park, Md. : APS, 1970-2015 , ISSN: 1550-235X , ZDB-ID: 1473011-X, ISSN 1550-235X, Bd. 83 (2011), 11, S. 115123, insges. 5 S.
http://dx.doi.org/10.1103/PhysRevB.83.115123
Study of sub-bandgap states in polymer-fullerene solar cells. - In: DPG Spring Meeting of the Condensed Matter Section with the divisions: Biological Physics, Chemical and Polymer Physics, Crystallography, Dielectric Solids, Dynamics and Statistical Physics, Low Temperature Physics, Magnetism, Metal and Material Physics, Physics of Socio-Economic Systems, Radiation and Medical Physics, Semiconductor Physics, Surface Science, Thin Films, Vacuum Science and Technology as well as the working group: Industry and Business, 2010, CPP 20.5
Ultrafast optical nonlinearities in hybrid metal-semiconductor nanostructures. - In: DPG Spring Meeting of the Condensed Matter Section with the divisions: Biological Physics, Chemical and Polymer Physics, Crystallography, Dielectric Solids, Dynamics and Statistical Physics, Low Temperature Physics, Magnetism, Metal and Material Physics, Physics of Socio-Economic Systems, Radiation and Medical Physics, Semiconductor Physics, Surface Science, Thin Films, Vacuum Science and Technology as well as the working group: Industry and Business, 2010, O 32.4
Excitonic dielectric function of hexagonal GaN. - In: DPG Spring Meeting of the Condensed Matter Section with the divisions: Biological Physics, Chemical and Polymer Physics, Crystallography, Dielectric Solids, Dynamics and Statistical Physics, Low Temperature Physics, Magnetism, Metal and Material Physics, Physics of Socio-Economic Systems, Radiation and Medical Physics, Semiconductor Physics, Surface Science, Thin Films, Vacuum Science and Technology as well as the working group: Industry and Business, 2010, HL 45.4
Ultrahigh temporal and spatial resolution imaging of second harmonic fields in random zinc oxide nanostructure arrays. - In: DPG Spring Meeting of the Condensed Matter Section with the divisions: Biological Physics, Chemical and Polymer Physics, Crystallography, Dielectric Solids, Dynamics and Statistical Physics, Low Temperature Physics, Magnetism, Metal and Material Physics, Physics of Socio-Economic Systems, Radiation and Medical Physics, Semiconductor Physics, Surface Science, Thin Films, Vacuum Science and Technology as well as the working group: Industry and Business, 2010, O 53.5
Simulation of the behaviour of surface plasmon polaritons on C 3 symmetric nano-holes arranged as C 4 symmetric arrays. - In: DPG Spring Meeting of the Condensed Matter Section with the divisions: Biological Physics, Chemical and Polymer Physics, Crystallography, Dielectric Solids, Dynamics and Statistical Physics, Low Temperature Physics, Magnetism, Metal and Material Physics, Physics of Socio-Economic Systems, Radiation and Medical Physics, Semiconductor Physics, Surface Science, Thin Films, Vacuum Science and Technology as well as the working group: Industry and Business, 2010, O 59.39
Coupled surface plasmon polariton - exciton modes for absorbing and pumped excitons. - In: DPG Spring Meeting of the Condensed Matter Section with the divisions: Biological Physics, Chemical and Polymer Physics, Crystallography, Dielectric Solids, Dynamics and Statistical Physics, Low Temperature Physics, Magnetism, Metal and Material Physics, Physics of Socio-Economic Systems, Radiation and Medical Physics, Semiconductor Physics, Surface Science, Thin Films, Vacuum Science and Technology as well as the working group: Industry and Business, 2010, O 59.37
Surface plasmon polaritons in a gold double-grating structure. - In: DPG Spring Meeting of the Condensed Matter Section with the divisions: Biological Physics, Chemical and Polymer Physics, Crystallography, Dielectric Solids, Dynamics and Statistical Physics, Low Temperature Physics, Magnetism, Metal and Material Physics, Physics of Socio-Economic Systems, Radiation and Medical Physics, Semiconductor Physics, Surface Science, Thin Films, Vacuum Science and Technology as well as the working group: Industry and Business, 2010, O 59.38
Theoretical investigation of the electron emission from metal nanotips. - In: DPG Spring Meeting of the Condensed Matter Section with the divisions: Biological Physics, Chemical and Polymer Physics, Crystallography, Dielectric Solids, Dynamics and Statistical Physics, Low Temperature Physics, Magnetism, Metal and Material Physics, Physics of Socio-Economic Systems, Radiation and Medical Physics, Semiconductor Physics, Surface Science, Thin Films, Vacuum Science and Technology as well as the working group: Industry and Business, 2010, O 63.2
Surface plasmon polaritons on arrays of nanostructures with three-fold symmetry. - In: DPG Spring Meeting of the Condensed Matter Section with the divisions: Biological Physics, Chemical and Polymer Physics, Crystallography, Dielectric Solids, Dynamics and Statistical Physics, Low Temperature Physics, Magnetism, Metal and Material Physics, Physics of Socio-Economic Systems, Radiation and Medical Physics, Semiconductor Physics, Surface Science, Thin Films, Vacuum Science and Technology as well as the working group: Industry and Business, 2010, O 72.1
Loss compensation of surface plasmon polaritons in multilayer structures with optically pumped gain media. - In: DPG Spring Meeting of the Condensed Matter Section with the divisions: Biological Physics, Chemical and Polymer Physics, Crystallography, Dielectric Solids, Dynamics and Statistical Physics, Low Temperature Physics, Magnetism, Metal and Material Physics, Physics of Socio-Economic Systems, Radiation and Medical Physics, Semiconductor Physics, Surface Science, Thin Films, Vacuum Science and Technology as well as the working group: Industry and Business, 2010, O 72.9
Electromagnetic polarisation twisting mediated by plasmon. - In: DPG Spring Meeting of the Condensed Matter Section with the divisions: Biological Physics, Chemical and Polymer Physics, Crystallography, Dielectric Solids, Dynamics and Statistical Physics, Low Temperature Physics, Magnetism, Metal and Material Physics, Physics of Socio-Economic Systems, Radiation and Medical Physics, Semiconductor Physics, Surface Science, Thin Films, Vacuum Science and Technology as well as the working group: Industry and Business, 2010, O 83.7
Surface plasmon polaritons on square-lattice arrays of three-fold symmetric nanostructures. - In: Photonics and nanostructures, ISSN 1569-4410, Bd. 8 (2010), 4, S. 297-302
http://dx.doi.org/10.1016/j.photonics.2010.04.009
Efficient optical excitation transfer in layered quantum dot nanostructures networked via optical near-field interactions. - In: Physical review. Condensed matter and materials physics / American Physical Society. - College Park, Md. : APS, 1970-2015 , ISSN: 1550-235X , ZDB-ID: 1473011-X, ISSN 1550-235X, Bd. 82 (2010), 12, S. 125417, insges. 8 S.
http://dx.doi.org/10.1103/PhysRevB.82.125417
Ultrafast manipulation of strong coupling in metal-molecular aggregate hybrid nanostructures. - In: ACS nano, ISSN 1936-086X, Bd. 4 (2010), 12, S. 7559-7565
http://dx.doi.org/10.1021/nn101973p
Subbandgap absorption in polymer-fullerene solar cells. - In: Applied physics letters, ISSN 1077-3118, Bd. 97 (2010), 25, S. 253302, insges. 3 S.
http://dx.doi.org/10.1063/1.3527077
Changes of the surface electronic structure of [EMIm]Tf 2 N room temperature ionic liquid induced by copper ions. - In: DPG Spring Meeting of the Condensed Matter Section with the divisions: Biological Physics, Chemical and Polymer Physics, Crystallography, Dielectric Solids, Dynamics and Statistical Physics, Low Temperature Physics, Magnetism, Metal and Material Physics, Physics of Socio-Economic Systems, Radiation and Medical Physics, Semiconductor Physics, Surface Science, Thin Films, Vacuum Science and Technology as well as the working group: Industry and Business, 2010, CPP 44.3
DFT-analysis of core levels from room-temperature Ionic Liquids. - In: DPG Spring Meeting of the Condensed Matter Section with the divisions: Biological Physics, Chemical and Polymer Physics, Crystallography, Dielectric Solids, Dynamics and Statistical Physics, Low Temperature Physics, Magnetism, Metal and Material Physics, Physics of Socio-Economic Systems, Radiation and Medical Physics, Semiconductor Physics, Surface Science, Thin Films, Vacuum Science and Technology as well as the working group: Industry and Business, 2010, CPP 44.4
German-Algerian university exchange from the perspective of students and teachers results of an intercultural survey. - In: Journal of studies in international education, ISSN 1552-7808, Bd. 14 (2010), 3, S. 240-258
http://dx.doi.org/10.1177/1028315308331293
Surface electronic structure of imidazolium-based ionic liquids studied by electron spectroscopy. - In: E-Journal of Surface Science and Nanotechnology, ISSN 1348-0391, Bd. 8 (2010), S. 241-245
http://dx.doi.org/10.1380/ejssnt.2010.241
Surface plasmon polariton - exciton interaction in metal-semiconductor and metal-dye nanostructures. - In: Journal of physics, ISSN 1742-6596, Bd. 210 (2010), S. 012001, insges. 4 S.
http://dx.doi.org/10.1088/1742-6596/210/1/012001
Calculation of exciton wave functions in electric fields. - In: Journal of physics, ISSN 1742-6596, Bd. 210 (2010), S. 012047, insges. 4 S.
http://dx.doi.org/10.1088/1742-6596/210/1/012047
Ultrafast optical nonlinearities in hybrid metal-J-aggregate nanostructures. - In: 2009 Conference on Lasers and Electro-Optics & Quantum Electronics and Laser Science Conference [i.e. International Quantum Electronics Conference], (2009), S. 2329-2330
Three-pulse photon echo beyond the impulsive limit - for example Nile-blue. - In: Frühjahrstagung 2009 der Sektion AMOP, 73. Jahrestagung der DPG mit Ordentlicher Mitgliederversammlung der DPG, mit den Fachverbänden Atomphysik, Massenspektrometrie, Molekülphysik, Quantenoptik und Photonik, Umweltphysik sowie den Arbeitskreisen Chancengleichheit, Energie und den Arbeitsgruppen Junge DPG, Information und Physik und Abrüstung, 2009, MO 9.6
Charge transport in classical geometrically frustrated systems. - In: DPG spring meeting of the Condensed Matter Section with the divisions: Biological Physics, Chemical and Polymer Physics, Dielectric Solids, Dynamics and Statistical Physics, Low Temperature Physics, Magnetism, Metal and Material Physics, Semiconductor Physics, Surface Science, Thin Films, Vacuum Science and Technology as well as the working groups: Industry and Business, Physics of Socio-Economic Systems, 2009, TT 6.4
Excitonic electroreflectance spectra of hexagonal GaN. - In: DPG spring meeting of the Condensed Matter Section with the divisions: Biological Physics, Chemical and Polymer Physics, Dielectric Solids, Dynamics and Statistical Physics, Low Temperature Physics, Magnetism, Metal and Material Physics, Semiconductor Physics, Surface Science, Thin Films, Vacuum Science and Technology as well as the working groups: Industry and Business, Physics of Socio-Economic Systems, 2009, HL 13.3
Surface plasmon polariton - exciton interaction in semiconductor-metal hybrids and dye-metal systems. - In: DPG spring meeting of the Condensed Matter Section with the divisions: Biological Physics, Chemical and Polymer Physics, Dielectric Solids, Dynamics and Statistical Physics, Low Temperature Physics, Magnetism, Metal and Material Physics, Semiconductor Physics, Surface Science, Thin Films, Vacuum Science and Technology as well as the working groups: Industry and Business, Physics of Socio-Economic Systems, 2009, O 20.8
Ultrafast optical nonlinearities in hybrid metal-J-aggregate nanostructures. - In: DPG spring meeting of the Condensed Matter Section with the divisions: Biological Physics, Chemical and Polymer Physics, Dielectric Solids, Dynamics and Statistical Physics, Low Temperature Physics, Magnetism, Metal and Material Physics, Semiconductor Physics, Surface Science, Thin Films, Vacuum Science and Technology as well as the working groups: Industry and Business, Physics of Socio-Economic Systems, 2009, O 20.9
Coherent exciton-surface plasmon polariton coupling in hybrid metal-J-aggregate. - In: DPG spring meeting of the Condensed Matter Section with the divisions: Biological Physics, Chemical and Polymer Physics, Dielectric Solids, Dynamics and Statistical Physics, Low Temperature Physics, Magnetism, Metal and Material Physics, Semiconductor Physics, Surface Science, Thin Films, Vacuum Science and Technology as well as the working groups: Industry and Business, Physics of Socio-Economic Systems, 2009, O 20.10
Calculation of optical near and far fields at metal-semiconductor hybrids/ Patrick Scholz; Stephan Schwieger; David Leipold and Erich Runge. - In: DPG spring meeting of the Condensed Matter Section with the divisions: Biological Physics, Chemical and Polymer Physics, Dielectric Solids, Dynamics and Statistical Physics, Low Temperature Physics, Magnetism, Metal and Material Physics, Semiconductor Physics, Surface Science, Thin Films, Vacuum Science and Technology as well as the working groups: Industry and Business, Physics of Socio-Economic Systems, 2009, O 27.73
Excitons in conjugated polymers - do we need a paradigma change. - In: DPG spring meeting of the Condensed Matter Section with the divisions: Biological Physics, Chemical and Polymer Physics, Dielectric Solids, Dynamics and Statistical Physics, Low Temperature Physics, Magnetism, Metal and Material Physics, Semiconductor Physics, Surface Science, Thin Films, Vacuum Science and Technology as well as the working groups: Industry and Business, Physics of Socio-Economic Systems, 2009, CPP 41.9
Surface plasmon polaritons on arrays of nanostructures with three-fold symmetry. - In: AIP conference proceedings, ISSN 1551-7616, Bd. 1176 (2009), S. 81-83
http://dx.doi.org/10.1063/1.3253937
Electronic properties of conjugated fullerenes using O-, NH-, or CH 2 -groups as bridges. - In: DPG spring meeting of the Condensed Matter Section with the divisions: Biological Physics, Chemical and Polymer Physics, Dielectric Solids, Dynamics and Statistical Physics, Low Temperature Physics, Magnetism, Metal and Material Physics, Semiconductor Physics, Surface Science, Thin Films, Vacuum Science and Technology as well as the working groups: Industry and Business, Physics of Socio-Economic Systems, 2009, CPP 43.1
Three-pulse photon echo beyond the impulsive limit. - In: DPG spring meeting of the Condensed Matter Section with the divisions: Biological Physics, Chemical and Polymer Physics, Dielectric Solids, Dynamics and Statistical Physics, Low Temperature Physics, Magnetism, Metal and Material Physics, Semiconductor Physics, Surface Science, Thin Films, Vacuum Science and Technology as well as the working groups: Industry and Business, Physics of Socio-Economic Systems, 2009, CPP 23.10
Ultra-fast nano-optics. - In: Laser & photonics reviews, ISSN 1863-8899, Bd. 3 (2009), 6, S. 483-507
https://doi.org/10.1002/lpor.200810064
Excitons in conjugated polymers: do we need a paradigma change?. - In: Physica status solidi. Applications and materials science. - Weinheim : Wiley-VCH, 2005- , ISSN: 1862-6319 , ZDB-ID: 1481091-8, ISSN 1862-6319, Bd. 206 (2009), 12, S. 2750-2756
http://dx.doi.org/10.1002/pssa.200925297
Ultrafast optical nonlinearities in hybrid metal-J-aggregate nanostructures. - In: European Conference on Lasers and Electro-Optics 2009 and the European Quantum Electronics Conference, ISBN 978-1-4244-4079-5, (2009), insges. 1 S.
http://dx.doi.org/10.1109/CLEOE-EQEC.2009.5194749
Calculation and interpretation of surface-plasmon-polariton features in the reflectivity of metallic nanowire arrays. - In: Condensed matter theories, volume 23, ISBN 978-981-283-661-8, (2009), S. 154-163
Coherent exciton-surface plasmon polariton interactions in hybrid metal semiconductor nanostructures. - In: Physica status solidi, ISSN 1610-1642, Bd. 6 (2009), 2, S. 466-469
http://dx.doi.org/10.1002/pssc.200880329
Photo-induced charge transfer in fullerene-oligothiophene dyads - a quantum-chemical study. - In: Chemical physics, Bd. 357 (2009), 1/3, S. 144-150
Erratum: Bd. 371 (2010), 1/3, Seite 96
The excited states of fullereneoligothiophene dyads were studied by quantum-chemical methods in respect of their theoretical suitability as solar-cell materials. Compared to the constituents a significant extension of the absorption spectra to the red has been found caused by optically excitable charge transfer states. These states seem to be responsible for the low energy conversion efficiency of fullereneoligothiophene dyads in photovoltaic devices.
http://dx.doi.org/10.1016/j.chemphys.2008.12.002
Near-field optics and plasmonic devices. - In: 1st Algerian-German International Conference on New Technologies and their Impact on Society, (2008), S. 8
Furan-bridged fullerenes - a new class of organic semiconductors?. - In: 72nd annual meeting and DPG spring meeting of the Condensed Matter Section and the divisions: Physics Education, History of Physics, Radiation and Medical Physics as well as the working groups: Equal Opportunities, Industry and Business, Information, Physics and Disarmament, Physics of Socio-Economic Systems, Young DPG, 2008, CPP 6.6
Charge transfer between covalently bound oligothiophenes and fullerene. - In: 72nd annual meeting and DPG spring meeting of the Condensed Matter Section and the divisions: Physics Education, History of Physics, Radiation and Medical Physics as well as the working groups: Equal Opportunities, Industry and Business, Information, Physics and Disarmament, Physics of Socio-Economic Systems, Young DPG, 2008, CPP 10.6
Simulation of 3-pulse photon echo with finite pulses. - In: 72nd annual meeting and DPG spring meeting of the Condensed Matter Section and the divisions: Physics Education, History of Physics, Radiation and Medical Physics as well as the working groups: Equal Opportunities, Industry and Business, Information, Physics and Disarmament, Physics of Socio-Economic Systems, Young DPG, 2008, CPP 8.8
Coherent exciton-surface plasmon polariton interaction in hybrid metal semiconductor nanostructures. - In: 72nd annual meeting and DPG spring meeting of the Condensed Matter Section and the divisions: Physics Education, History of Physics, Radiation and Medical Physics as well as the working groups: Equal Opportunities, Industry and Business, Information, Physics and Disarmament, Physics of Socio-Economic Systems, Young DPG, 2008, HL 22.1
Excitonic electroreflectance spectra of hexagonal GaN. - In: 72nd annual meeting and DPG spring meeting of the Condensed Matter Section and the divisions: Physics Education, History of Physics, Radiation and Medical Physics as well as the working groups: Equal Opportunities, Industry and Business, Information, Physics and Disarmament, Physics of Socio-Economic Systems, Young DPG, 2008, HL 31.3
Tunable quantum wires: new horizons in plasmonics. - In: 72nd annual meeting and DPG spring meeting of the Condensed Matter Section and the divisions: Physics Education, History of Physics, Radiation and Medical Physics as well as the working groups: Equal Opportunities, Industry and Business, Information, Physics and Disarmament, Physics of Socio-Economic Systems, Young DPG, 2008, O 66.2
Surface plasmon polaritons in metal-semiconductor hybrid structures. - In: 72nd annual meeting and DPG spring meeting of the Condensed Matter Section and the divisions: Physics Education, History of Physics, Radiation and Medical Physics as well as the working groups: Equal Opportunities, Industry and Business, Information, Physics and Disarmament, Physics of Socio-Economic Systems, Young DPG, 2008, HL 51.19
Theory of surface plasmon polariton-exciton interaction. - In: 72nd annual meeting and DPG spring meeting of the Condensed Matter Section and the divisions: Physics Education, History of Physics, Radiation and Medical Physics as well as the working groups: Equal Opportunities, Industry and Business, Information, Physics and Disarmament, Physics of Socio-Economic Systems, Young DPG, 2008, HL 53.13
Coherent exciton-surface plasmon polariton interactions in hybrid metal semiconductor nanostructures. - In: 2008 Conference on Lasers and Electro-Optics & Quantum Electronics and Laser Science Conference, (2008), S. 3457-3458
Cu cap layer on Ni8/Cu(001): reorientation and Tc-shift. - In: The European physical journal, ISSN 1434-6036, Bd. 65 (2008), 4, S. 499-504
Adding a non-magnetic Cu overlayer on Ni8/Cu(001) is known to induce the reorientation of the magnetic easy axis from in-plane to out-of-plane and to reduce the Curie temperature. In this paper both effects are described on the same footing using an effective Heisenberg trilayer. The model takes into account thermal fluctuations of the magnetization and allows to separate explicitly between two possible mechanisms behind the experimental observations, namely between a reduction of the magnetic moment by hybridization and a lattice relaxation at the Ni/Cu interface. Ferromagnetic resonance data for the reorientation and the decreased Curie temperature due to the Cu cap layer are best reproduced by assuming a reduction of the magnetic moment at the interface by approximately 1/3.
https://doi.org/10.1140/epjb/e2008-00368-5
Calculation and interpretation of surface-plasmon-polariton features in the reflectivity of metallic nanowire arrays. - In: International journal of modern physics, ISSN 1793-6578, Bd. 22 (2008), 25/26, S. 4442-4451
The far-field reflectivity of metallic nanowire arrays designed to show strong surface-plasmon-polariton (SPP) resonances is studied numerically. The results of calculations in time and frequency space as well as the results of semi-analytic theories using different approximative boundary conditions at the metal surfaces are evaluated and compared. Good agreement between all different methods is obtained in most cases. The SPP-related features are superimposed on a strongly varying background. Combining FDTD simulations, finite element results, and semi-analytical calculations, the microscopic origin of the background contribution is identified. Resonant transmission through sub-wavelength slits leads to pronounced oscillations in the far-field reflectivity as a function of the height of the nanowires.
http://dx.doi.org/10.1142/S021797920805019X
Strongly correlated electrons on frustrated lattices. - In: Iranian journal of physics research, Bd. 8 (2008), 2, S. 13-24
We give an overview of recent work on charge degrees of freedom of strongly correlated electrons on geometrically frustrated lattices. Special attention is paid to the checkerboard lattice, i.e., the two-dimensional version of a pyrochlore lattice and to the kagomé lattice. For the checkerboard lattice it is shown that at half filling when spin degrees of freedom are neglected and at quarter filling when they are included excitations with fractional charges ±e/2 may exist. The same holds true for the three-dimensional pyrochlore lattice. In the former case the fractional charges are confined. The origin of the weak, constant confining force is discussed and some similarities to quarks and to string theory are pointed out. For the checkerboard lattice a formulation in terms of a compact U(1) gauge theory is d escribed. Furthermore a new kinetic mechanism for ferromagnetism at special fillings of a kagomé lattice is discussed.
http://journals.iut.ac.ir/ijpr/efullv8n2y2008p13-24.pdf
The influence of wire shape on surface plasmon mode distribution. - In: Applied physics. Lasers and optics. - Berlin : Springer, 1981- , ISSN: 1432-0649 , ZDB-ID: 1458437-2, ISSN 1432-0649, Bd. 93 (2008), 1, S. 111-115
The influence of the nanowire shape on the excitation of surface plasmon polaritons at metallic nanowire arrays is studied numerically. For a system of silver nanowires housed on a polymer substrate, nanowires with rectangular and elliptical cross sections are compared. It was found that in the case of rectangular nanowires the excitation efficiency is higher for surface plasmons at the polymermetal interface than for surface plasmons at the airmetal interface. Conversely, in the case of elliptical nanowires the airmetal plasmon modes are stronger. Further, it is noted that the nanowire shape directly influences the position of the surface plasmon resonance.
http://dx.doi.org/10.1007/s00340-008-3208-y
Coherent exciton-surface-plasmon-polariton interaction in hybrid metal-semiconductor nanostructures. - In: Physical review letters, ISSN 1079-7114, Bd. 101 (2008), 11, 116801, insges. 4 S.
We report measurements of a coherent coupling between surface plasmon polaritons (SPP) and quantum well excitons in a hybrid metal-semiconductor nanostructure. The hybrid structure is designed to optimize the radiative exciton-SPP interaction which is probed by low-temperature, angle-resolved, far-field reflectivity spectroscopy. As a result of the coupling, a significant shift of ˜7 meV and an increase in broadening by ˜4 meV of the quantum well exciton resonance are observed. The experiments are corroborated by a phenomenological coupled-oscillator model predicting coupling strengths as large as 50 meV in structures with optimized detunings between the coupled exciton and SPP resonances. Such a strong interaction can, e.g., be used to enhance the luminescence yield of semiconductor quantum structures or to amplify SPP waves.
https://doi.org/10.1103/PhysRevLett.101.116801
Torsional broadening in absorption and emission spectra of bithiophene as calculated by time-dependent density functional theory. - In: Chemical physics, Bd. 349 (2008), 1/3, S. 250-255
The optimized geometries of bithiophene in the electronic ground and excited state have been calculated by time-dependent density functional theory using the hybrid functional B3-LYP. The dependence of the singlet excitation energies and transition dipoles on the torsion between the two thienyl groups has been determined and compared with the torsional potential curve previously found for biphenyl. Based on these data the torsional progressions in absorption and emission have been computed quantum-mechanically in order to show their contribution to the inhomogeneous broadening in the respective spectra of bithiophene.
http://dx.doi.org/10.1016/j.chemphys.2008.03.008
Theory of the surface plasmon polariton-exciton interaction in multi-layer systems. - In: Physica status solidi, ISSN 1521-3951, Bd. 245 (2008), 6, S. 1071-1075
A thorough theoretical understanding of the interaction of excitons and surface plasmon polaritons (SPP) in metal-semiconductor hybrid structures is of fundamental importance for the design of SPP-based devices. A theory to describe SPP-exciton interaction in a periodic multilayer film system is presented and demonstrated. In a hybrid system of gold nanowires on top of a GaAs/AlGaAs quantum well (QW), our calculations show the formation of coupled SPP-exciton modes. These are predicted to be observable in reflection spectra and by near-field scanning optical microscopy.
http://dx.doi.org/10.1002/pssb.200777608
Excited state properties of neutral and charged ter-fluorene with and without a keto-defect. - In: Physica status solidi, ISSN 1521-3951, Bd. 245 (2008), 5, S. 849-853
Stimulated by the recent experimental report of optical properties of charged oligofluorenes [S. Fratiloiu et al., J. Phys. Chem. B 110, 5984-5993 (2006)], we have used time-dependent density functional theory (TD-DFT) to study the electronic structure of neutral and charged ter-fluorene with and without keto-defect. We have characterized the excited states by site- and space-based representations of the density matrix. For the defectless neutral species we found typical excitons, while the first excited states of the corresponding charged species represent long-range oscillations of the electron or hole along the whole oligomer. For the neutral ketonized ter-fluorene we found trapping of the excited electron. Similarly, the unpaired electron of the anion ground state is trapped. The excited state properties of the cation, however, are insensitive to the keto-defect.
http://dx.doi.org/10.1002/pssb.200743442
Tunable quantum wires: new horizons in plasmonics. - In: 71st annual meeting of the DPG and spring meeting of the Condensed Matter Division and the sections: Biological Physics, Environmental Physics, Extraterrestrial Physics, History of Physics, Physics Education, Radiation and Medical Physics as well as the working groups: Energy Matters, Equal Opportunities, Industry and Economy, Information, Physics and Disarmament, Physics of Socio-Economic Systems, 2007, O 12.9
Green function theory vs. quantum Monte Carlo calculation for thin magnetic films. - In: 71st annual meeting of the DPG and spring meeting of the Condensed Matter Division and the sections: Biological Physics, Environmental Physics, Extraterrestrial Physics, History of Physics, Physics Education, Radiation and Medical Physics as well as the working groups: Energy Matters, Equal Opportunities, Industry and Economy, Information, Physics and Disarmament, Physics of Socio-Economic Systems, 2007, MA 15.31
Temperature driven spin reorientation transition in thin films. - In: 71st annual meeting of the DPG and spring meeting of the Condensed Matter Division and the sections: Biological Physics, Environmental Physics, Extraterrestrial Physics, History of Physics, Physics Education, Radiation and Medical Physics as well as the working groups: Energy Matters, Equal Opportunities, Industry and Economy, Information, Physics and Disarmament, Physics of Socio-Economic Systems, 2007, MA 15.140
Strongly correlated fermions on frustrated lattices. - In: 71st annual meeting of the DPG and spring meeting of the Condensed Matter Division and the sections: Biological Physics, Environmental Physics, Extraterrestrial Physics, History of Physics, Physics Education, Radiation and Medical Physics as well as the working groups: Energy Matters, Equal Opportunities, Industry and Economy, Information, Physics and Disarmament, Physics of Socio-Economic Systems, 2007, TT 14.7
Conformational disorder of conjugated polymers. - In: 71st annual meeting of the DPG and spring meeting of the Condensed Matter Division and the sections: Biological Physics, Environmental Physics, Extraterrestrial Physics, History of Physics, Physics Education, Radiation and Medical Physics as well as the working groups: Energy Matters, Equal Opportunities, Industry and Economy, Information, Physics and Disarmament, Physics of Socio-Economic Systems, 2007, SYOE 8.106
Vertically and relaxed excited state properties of neutral and charged oligofluorenses with and without keto-defect. - In: 71st annual meeting of the DPG and spring meeting of the Condensed Matter Division and the sections: Biological Physics, Environmental Physics, Extraterrestrial Physics, History of Physics, Physics Education, Radiation and Medical Physics as well as the working groups: Energy Matters, Equal Opportunities, Industry and Economy, Information, Physics and Disarmament, Physics of Socio-Economic Systems, 2007, SYOE 8.107
Coupling phenomena of surface plasmons. - In: 71st annual meeting of the DPG and spring meeting of the Condensed Matter Division and the sections: Biological Physics, Environmental Physics, Extraterrestrial Physics, History of Physics, Physics Education, Radiation and Medical Physics as well as the working groups: Energy Matters, Equal Opportunities, Industry and Economy, Information, Physics and Disarmament, Physics of Socio-Economic Systems, 2007, HL 33.3
Anisotropy and interlayer exchange coupling in thin magnetic films: beyond the Landau-Lifshitz evaluation of spin wave spectra. - In: 71st annual meeting of the DPG and spring meeting of the Condensed Matter Division and the sections: Biological Physics, Environmental Physics, Extraterrestrial Physics, History of Physics, Physics Education, Radiation and Medical Physics as well as the working groups: Energy Matters, Equal Opportunities, Industry and Economy, Information, Physics and Disarmament, Physics of Socio-Economic Systems, 2007, MA 26.1
Classical transport on lattices with frustrated interactions. - In: 71st annual meeting of the DPG and spring meeting of the Condensed Matter Division and the sections: Biological Physics, Environmental Physics, Extraterrestrial Physics, History of Physics, Physics Education, Radiation and Medical Physics as well as the working groups: Energy Matters, Equal Opportunities, Industry and Economy, Information, Physics and Disarmament, Physics of Socio-Economic Systems, 2007, TT 33.4
Coherent exciton-surface plasmon polariton interactions in hybrid metal semiconductor nanostructures. - In: International Workshop on Physics of Semiconductor Devices, 2007, ISBN 978-1-4244-1728-5, (2007), insges. 3 S.
http://dx.doi.org/10.1109/IWPSD.2007.4472531
Mechanism of temperature dependence of the magnetic anisotropy energy in ultrathin Cobalt and Nickel films. - In: Journal of magnetism and magnetic materials, ISSN 1873-4766, Bd. 316.2007, 2, e86-e89
Temperature dependent FMR-measurements of Ni and Co films are analysed using a microscopic theory for ultrathin metallic systems. The mechanism governing the temperature dependence of the magnetic anisotropy energy is identified and discussed. It is reduced with increasing temperature. This behavior is found to be solely caused by magnon excitations.
http://dx.doi.org/10.1016/j.jmmm.2007.02.134
Green function theory versus quantum Monte Carlo calculations for thin magnetic films. - In: Physical review. Condensed matter and materials physics / American Physical Society. - College Park, Md. : APS, 1970-2015 , ISSN: 1550-235X , ZDB-ID: 1473011-X, ISSN 1550-235X, Bd. 75 (2007), 21, S. 214401, insges. 8 S.
In this work we compare numerically exact quantum Monte Carlo QMC calculations and Green function theory GFT calculations of thin ferromagnetic films including second-order anisotropies. Thereby, we concentrate on easy-plane systems, i.e., systems for which the anisotropy favors a magnetization parallel to the film plane. We discuss these systems in perpendicular external field, i.e., B parallel to the film normal. GFT results are in good agreement with QMC for high enough fields and temperatures. Below a critical field or a critical temperature, no collinear stable magnetization exists in GFT. On the other hand, QMC gives finite magnetization even below those critical values. This indicates that there occurs a transition from noncollinear to collinear configurations with increasing field or temperature. For slightly tilted external fields, a rotation of magnetization from out-of-plane to in-plane orientation is found with decreasing temperature.
http://dx.doi.org/10.1103/PhysRevB.75.214401
Tunable nanowires: an additional degree of freedom in plasmonics. - In: Physical review. Condensed matter and materials physics / American Physical Society. - College Park, Md. : APS, 1970-2015 , ISSN: 1550-235X , ZDB-ID: 1473011-X, ISSN 1550-235X, Bd. 76 (2007), 8, S. 085420, insges. 4 S.
We report on the excitation of surface plasmon polaritons (SPP's) on a periodic arrangement of metallic ribbons with tunable periodicity. The ability to vary its lattice constant results in an additional degree of freedom, permitting excitation of SPP's for any combination of wavelength and angle of incidence within the tuning range of the system. Moreover, the designed smart material allows fundamental questions to be answered regarding SPP propagation and localization. Finally, the concept opens vistas in the development of other methodologies in spectroscopy including plasmonic sensors and chips.
http://dx.doi.org/10.1103/PhysRevB.76.085420
Charge degrees in the quarter-filled checkerboard lattice. - In: Journal of magnetism and magnetic materials, ISSN 1873-4766, Bd. 310.2007, 2, Pt. 2, S. 966-968
For a systematic study of charge degrees of freedom in lattices with geometric frustration, we consider spinless fermions on the checkerboard lattice with nearest-neighbor hopping t and nearest-neighbor repulsion V at quarter-filling. An effective Hamiltonian in the limit |t|<<V is given to lowest non-vanishing order by the ring exchange (tџ/Vø). We show that the system can equivalently be described by hard-core bosons and map the model to a confining U(1) lattice gauge theory.
http://dx.doi.org/10.1016/j.jmmm.2006.10.348
Fractionally charged excitations on frustrated lattices. - In: International journal of modern physics, ISSN 1793-6578, Bd. 21 (2007), 13/14, S. 2215-2231
Systems of strongly correlated fermions on certain geometrically frustrated lattices at particular filling factors support excitations with fractional charges ±e/2. We calculate quantum mechanical ground states, lowlying excitations and spectral functions of finite lattices by means of numerical diagonalization. The ground state of the most thorough-fully studied case, the criss-crossed checkerboard lattice, is degenerate and shows longrange order. Static fractional charges are confined by a weak linear force, most probably leading to bound states of large spatial extent. Consequently, the quasi-particle weight is reduced, which reflects the internal dynamics of the fractionally charged excitations. By using an additional parameter, we finetune the system to a special point at which fractional charges are manifestly deconfinedthe socalled RokhsarKivelson point. For a deeper understanding of the lowenergy physics of these models and fornumerical advantages, several conserved quantum numbers are identified.
http://dx.doi.org/10.1142/S0217979207043609
Temperature-dependent electronic and vibrational structure of the 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide room-temperature ionic liquid surface : a study with XPS, UPS, MIES, and HREELS. - In: The journal of physical chemistry, ISSN 1520-5207, Bd. 111 (2007), 18, S. 4801-4806
The near-surface structure of the room-temperature ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) amide has been investigated as a function of temperature between 100 and 620 K. We used a combination of photoelectron spectroscopies (XPS and UPS), metastable induced electron spectroscopy (MIES), and high-resolution electron energy loss spectroscopy (HREELS). The valence band and HREELS spectra are interpreted on the basis of density functional theory (DFT) calculations. At room temperature, the most pronounced structures in the HREELS, UPS, and MIES spectra are related to the CF3 group in the anion. Spectral changes observed at 100 K are interpreted as a change of the molecular orientation at the outermost surface, when the temperature is lowered. At elevated temperatures, early volatilization, starting at 350 K, is observed under reduced pressure.
http://dx.doi.org/10.1021/jp067136p
Temperature dependence of interlayer exchange coupling. - In: Journal of magnetism and magnetic materials, ISSN 1873-4766, Bd. 310.2007, 2, Pt. 3, S. 2301-2303
We use a microscopic model for ultrathin metallic films to analyze temperature dependent FMR measurements of exchange coupled NiCo films. The reduction of the interlayer exchange coupling with increasing temperature is investigated. We find that magnon excitations are the dominating cause of the temperature dependence.
http://dx.doi.org/10.1016/j.jmmm.2006.10.1038
Spin-wave excitations: the main source of the temperature dependence of interlayer exchange coupling in nanostructures. - In: Physical review letters, ISSN 1079-7114, Bd. 98 (2007), 5, 057205, insges. 4 S.
Quantum mechanical calculations based on an extended Heisenberg model are ompared with ferromagnetic resonance experiments on prototype trilayer systems Ni7/Cun/Co2/Cu(001)in order to determine and separate for the first time quantitatively the sources of the temperature dependence of interlayer exchange coupling. Magnon excitations are responsible for about 75% of the reduction of the coupling strength from zero to room temperature. The remaining 25% are due to temperature effects in the effective quantum well and the spacer-magnet interfaces.
https://doi.org/10.1103/PhysRevLett.98.057205
A comparative study on the electronic structure of the 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide RT-ionic liquid by electron spectroscopy and first principles calculations. - In: Zeitschrift für physikalische Chemie, ISSN 2196-7156, Bd. 220 (2006), 10, S. 1407-1416
The near-surface electronic structure of the room-temperature ionic liquid 1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide has been investigated with ultraviolet and X-ray photoelectron spectroscopy as well as metastable induced electron spectroscopy. The results have been compared with density functional theory calculations. The good agreement between the experimental and theoretical data provides detailed insight into the origin of the observed spectral features. In particular, we found that a simple composition of the spectra of the isolated ions does not suffice to fit to the experimental results, but interionic interactions have to be considered.
http://dx.doi.org/10.1524/zpch.2006.220.10.1407
A new type of temperature driven reorientation transition in magnetic thin films. - In: The European physical journal, ISSN 1434-6036, Bd. 53 (2006), 4, S. 463-469
We present a new type of temperature driven spin reorientation transition (SRT) in thin films. It can occur when the lattice and the shape anisotropy favor different easy directions of the magnetization. Due to different temperature dependencies of the two contributions the effective anisotropy may change its sign and thus the direction of the magnetization as a function of temperature may change. Contrary to the well-known reorientation transition caused by competing surface and bulk anisotropy contributions the reorientation that we discuss is also found in film systems with a uniform lattice anisotropy. The results of our theoretical model study may have experimental relevance for film systems with positive lattice anisotropy, as e.g. thin iron films grown on copper.
https://doi.org/10.1140/epjb/e2006-00410-8
Strong dispersion of the surface optical phonon of silicon carbide in the near vicinity of the surface Brillouin zone center. - In: Surface science, ISSN 1879-2758, Bd. 600 (2006), 14, S. 2886-2893
The surface optical or FuchsKliewer phonons of the (0 0 1) surface of 3C-SiC and the Si-terminated (0 0 0 1) surfaces of 4H- and 6H-SiC have been investigated with high resolution electron energy loss spectroscopy (HREELS). For each of the SiC polytypes the frequency of the surface optical phonon changes with surface reconstruction, indicating subtle differences in the static polarization at differently reconstructed surfaces. Due to their anisotropy, hexagonal surfaces exhibit a second, much weaker FuchsKliewer mode. For all surfaces under examination, a linear dispersion of the FuchsKliewer mode frequency has been found for wave vectors close to the Gamma-point. This dispersion can be explained by dynamical dipole coupling between atomic oscillators at the surface of the highly polar silicon carbide.
http://dx.doi.org/10.1016/j.susc.2006.05.031
Surface phonons of clean, hydrogen- and deuterium-terminated Si(0 0 1) surfaces. - In: Surface science, ISSN 1879-2758, Bd. 600 (2006), 17, S. 3446-3455
We present a comprehensive vibrational study of the clean and hydrogen- or deuterium-terminated silicon (0 0 1) surface. The modes related to the clean as well as to the H:Si, D:Si, and 2H:Si, 2D:Si surfaces are studied by means of high resolution electron energy loss spectroscopy (HREELS). We pay special attention to the modification of the phonon modes by the surface treatments and compare the data with reported experimental and theoretical results. The analysis of the relative phonon intensities of the clean, mono- and dihydride surfaces yields the assignment of the modes related to the dimer bonds. The isotopic shifts of vibrons related to the SiH and SiD bonds and to the surface phonon are discussed and applied to the characterisation of the surface excitations.
http://dx.doi.org/10.1016/j.susc.2006.06.030
Charge degrees of freedom on frustrated lattices, 2006. - Online Ressource : Ilmenau, Techn. Univ., Diss., 2006
Zsfassung in dt. Sprache. - urn:nbn:de:gbv:ilm1-2006000140
Elektronische Korrelationen spielen in der Physik der kondensierten Materie eine wichtige Rolle, sie führen zu Phänomenen wie Magnetismus oder dem Mott-Hubbard Metall-Isolator-Übergang. In dieser Arbeit wird eine neuartige Klasse von Modellen stark korrelierter Elektronen betrachtet [fulde2002]. Diese ermöglicht aufgrund des Wechselspiels zwischen starken Korrelationen und geometrischer Frustration das Auftreten fraktional geladener Teilchen in zwei Dimensionen (2D) und drei Dimensionen (3D). Geometrisch frustrierte Systeme sind durch eine hohe Dichte niedrig liegender Anregungen gekennzeichnet welche zu einer großen Suszeptibilität und somit zu interessanten physikalischen Effekten führen kann. Diese Arbeit enthält eine systematische Untersuchung von stark korrelierten spinlosen Fermionen auf bestimmten frustrierten Gittern. Insbesondere wird der interessante Grenzfall untersucht, in dem eine Wechselwirkung V zwischen benachbarten Plätzen groß gegenüber dem Hüpfmatrixelement |t| ist. In diesem Fall können fraktionale Ladungen \pm e/2 realisiert werden. Im klassischen Grenzfall (t=0) führt die geometrische Frustration zu einer makroskopischen Entartung und alle Grundzustände können, abhängig vom Füllfaktor, auf Schleifen- beziehungsweise Dimer-Konfigurationen auf Gittern abgebildet werden. Zum Beispiel können die klassischen Grundzustände des halb gefüllten Checkerboard-Gitters auf dicht gepackte Schleifen-Konfigurationen auf dem QuadratGitter abgebildet werden. Die Korrelationsfunktionen zwischen zwei Defekten (zwei fraktionalen Ladungen) werden jeweils für Schleifen- und Dimer-Modelle auf unterschiedlichen Gittern analytisch und numerisch berechnet. Die Ergebnisse zeigen eine algebraische Abnahme mit der Entfernung auf 2D bipartiten Gittern und eine exponentielle auf dem 2D Dreiecks-Gitter, welches nicht bipartit ist. Die Korrelationen auf dem 3D bipartiten Diamant-Gitter fallen exponentiell mit dem inversen Abstand ab. Die makroskopische Entartung des Grundzustandes im klassischen Grenzfall wird bei endlichem t durch Quantenfluktuationen aufgehoben. Wir berechnen mit Hilfe der numerischen Diagonalisierung den quantenmechanischen Grundzustand sowie die niedrig liegenden Anregungen auf kleinen Checkerboard-Clustern. Für den Fall |t|\ll V ist ein effektiver Hamilton-Operator in niedrigster Ordnung durch Ringaustausch um Hexagone (\sim t^{3}/V^{2}) gegeben [runge2004]. Eine Eichtransformation ermöglicht es, das fermionische Vorzeichenproblem für den Grundzustand und die niedrig liegenden Anregungen zu eliminieren. Folglich kann das System bezüglich dieser Anregungen durch ein äquivalentes bosonisches System beschrieben werden. Der quantenmechanische Grundzustand zeigt eine langreichweitige Ordnung. Zwei statische fraktionale Ladungen erfahren eine gegenseitige anziehende Kraft, welche unabhängig vom Abstand ist. Diese resultiert aus einer Reduktion der Quantenfluktuationen und der Polarisation des Vakuums entlang einer Linie, welche die beiden fraktionalen Ladungen miteinander verbindet. Die berechneten Spektralfunktionen zeigen im niedrig energetischen Bereich eine breite Struktur, welche durch die Dynamik der fraktional geladenen Anregungen entsteht. In den Spektralfunktionen zeigen sich Signaturen von Landau'schen Quasiteilchen mit großer räumlicher Ausdehnung (gebundene Paare von zwei fraktional geladenen Teilchen). Berechnungen der optischen Leitfähigkeit zeigen, wie fraktionale Ladungen zur elektrischen Leitfähigkeit beitragen. Durch eine geeignete Erweiterung unseres Modells kann man erreichen, dass es für einen Punkt im Parameterraum exakt lösbar wird. Dieser Punkt hat große Ähnlichkeit mit dem Rokhsar-Kivelson Punkt des Quanten-Dimer Modells [rokhsar1988]. An diesem Punkt sind die fraktionalen Ladungen ungebunden. Für ein tieferes Verständins des betrachteten Modells auf dem Checkerboard-Gitter führen wir eine Abbildung auf eine U(1) Gitter-Eichtheorie ein. Diese stellt einen Bezug zwischen fraktionalen Ladungen auf frustrierten Gittern und der kompakten Quantenelektrodynamik in 2+1 Dimensionen her. Des weiteren können wir mit Hilfe einer Dualitätstransformation unser Modell auf das Höhenmodell abbilden. Für eine erste Untersuchung eines 3D Systems mit fraktionalen Ladungen leiten wir einen effektiven Hamilton-Operator für das halb gefüllte Pyrochlor-Gitter her. Mit Hilfe von numerischen Diagonalisierungen berechnen wir den Grundzustand von kleinen Pyrochlor-Gittern. Qualitative Unterschiede und Ähnlichkeiten zum Grundzustand des oben beschriebenen Checkerboard-Gitters werden diskutiert.
http://d-nb.info/982205066/34
Conformational disorder of conjugated polymers. - In: The journal of chemical physics, ISSN 1089-7690, Bd. 125 (2006), 15, 154903, insges. 7 S.
Conformational disorder of conjugated polymers is an important issue to be understood and quantified. In this paper we present a new method to assess the chain conformation of conjugated polymers based on measurements of intrachain energy transfer. The chain conformation is modeled on the basis of monomer-monomer interactions, such as torsion, bending, and stretching of the connecting bond. The latter two potentials are assumed to be harmonic, while the torsional potential was calculated by density functional theory using B3-LYP functional with the SVP basis set. The energy transfer dynamics of excitons on these chains are quantitatively simulated using Förster-type line-dipole energy transfer. This allows us to compare the simulated ground state conformation of single polymer chains to ultrafast depolarization experiments of poly [3-(2,5-dioctylphenyl)thiophene] in solution. We identify torsional rotation as the main contributor to conformational disorder and find that this disorder is mainly controlled by the energy difference between syn and anti bonds.
https://doi.org/10.1063/1.2358682
Anomalous energy transfer dynamics due to torsional relaxation in a conjugated polymer. - In: Physical review letters, ISSN 1079-7114, Bd. 97 (2006), 16, 166804, insges. 4 S.
In isolated conjugated polymers two explanations are in discussion for the redshift of the emission on a picosecond time scaleexciton energy transfer (EET) between conjugated segments along the chains and conformational changes of these segments themselves, i.e., torsional relaxation. In order to resolve this question we perform femtosecond time-resolved transient absorption measurements of the energy relaxation of poly[3-(2,5-dioctylphenyl)thiophene] in toluene solution. We show that torsional relaxation can be distinguished from EET by site-selectively exciting low-energy conjugated segments. We present a unified model that integrates EET and torsional dynamics. In particular, comparison to ultrafast depolarization measurements shows that torsional dynamics cannot be neglected when analyzing EET dynamics and furthermore reveals that the exciton extends itself by about 2 monomer units during torsional relaxation.
https://doi.org/10.1103/PhysRevLett.97.166804
Comparison of the electronic structure of PPV and its derivative DIOXA-PPV. - In: Chemical physics, Bd. 327 (2006), 2/3, S. 474-484
Electronic structure of two conjugated polymers, PPV and its derivative DIOXA-PPV, are studied by quantum-chemistry methods. Good agreement between the calculations and available experimental data validates the applied methods and enables us to draw conclusions about properties of excitons and polarons in these polymers. In particular, simultaneous use of different correlation plots in atomic site representation and transition densities in real space representation reveals electronic structure and spatial localization of the elementary excitations. The properties of the DIOXA-PPV are discussed in context of possible applications in molecular electronics devices.
http://dx.doi.org/10.1016/j.chemphys.2006.05.031
Interpretation of near-field images of semiconductor nanostructures. - In: Applied physics. Lasers and optics. - Berlin : Springer, 1981- , ISSN: 1432-0649 , ZDB-ID: 1458437-2, ISSN 1432-0649, Bd. 84 (2006), 1/2, S. 103-110
We discuss near-field wave function imaging, introducing a model for high spatial resolution photoluminescence imaging of semiconductor nanostructures. The model is applied to optically bright and dark exciton and biexciton states in different quantum dot systems, explicitly taking the experimental imaging configuration into account. Our results show that direct imaging of the exciton density is only possible in collection mode experiments with nonresonant excitation in the high-resolution limit. For other geometries and for biexcitonic states, the images reflect not only the size and shape of the wave function and the spatial resolution of the near-field probe but also in particular the inherent optical nonlinearity of the imaging process. Different examples for the effects of this nonlinearity are discussed, providing new insight into the interpretation of existing experiments, and guidelines for designing novel experiments.
http://dx.doi.org/10.1007/s00340-006-2215-0
Spectral functions and optical conductivity of spinless fermions on a checkerboard lattice. - In: Physical review. Condensed matter and materials physics / American Physical Society. - College Park, Md. : APS, 1970-2015 , ISSN: 1550-235X , ZDB-ID: 1473011-X, ISSN 1550-235X, Bd. 73 (2006), 12, S. 125121, insges. 9 S.
We study the dynamical properties of spinless fermions on the checkerboard lattice. Our main interest is the limit of large nearest-neighbor repulsion V as compared with hopping |t|. The spectral functions show broad low-energy excitations which are due to the dynamics of fractionally charged excitations. Furthermore, it is shown that the fractional charges contribute to the electrical current density.
http://dx.doi.org/10.1103/PhysRevB.73.125121
Classical correlations of defects in lattices with geometrical frustration in the motion of a particle. - In: Physical review. Condensed matter and materials physics / American Physical Society. - College Park, Md. : APS, 1970-2015 , ISSN: 1550-235X , ZDB-ID: 1473011-X, ISSN 1550-235X, Bd. 73 (2006), 17, S. 174417, insges. 5 S.
We map certain highly correlated electron systems on lattices with geometrical frustration in the motion of added particles or holes to the spatial defect-defect correlations of dimer models in different geometries. These models are studied analytically and numerically. We consider different coverings for four different lattices: square, honeycomb, triangular, and diamond. In the case of a hard-core dimer covering, we verify the existing results for square and triangular lattices and obtain new ones for the honeycomb and diamond lattices while in the case of a loop covering we obtain new numerical results for all the lattices and use the existing analytical Liouville field theory for the case of a square lattice. The results show power-law correlations for the square and honeycomb lattices, while exponential decay with distance is found for the triangular lattice and exponential decay with the inverse distance on the diamond lattice. We relate this fact to the lack of bipartiteness of the triangular lattice and in the latter case to the three dimensionality of the diamond. The connection of our findings to the problem of fractionalized charge in such lattices is pointed out.
http://dx.doi.org/10.1103/PhysRevB.73.174417
Control of emission by intermolecular fluorescence resonance energy transfer and intermolecular charge transfer. - In: The journal of physical chemistry, ISSN 1520-5215, Bd. 110 (2006), 19, S. 6324-6328
Control of emission by intermolecular fluorescence resonant energy transfer (IFRET) and intermolecular charge transfer (ICT) is investigated with the quantum-chemistry method using two-dimensional (2D) and three-dimensional (3D) real space analysis methods. The work is based on the experiment of tunable emission from doped 1,3,5-triphenyl-2-pyrazoline (TPP) organic nanoparticles (Peng, A. D.; et al. Adv. Mater. 2005, 17, 2070). First, the excited-state properties of the molecules, which are studied (TPP and DCM) in that experiment, are investigated theoretically. The results of the 2D site representation reveal the electron-hole coherence and delocalization size on the excitation. The results of 3D cube representation analysis reveal the orientation and strength of the transition dipole moments and intramolecular or intermolecular charge transfer. Second, the photochemical quenching mechanism via IFRET is studied (here "resonance" means that the absorption spectrum of TPP overlaps with the fluorescence emission spectrum of DCM in the doping system) by comparing the orbital energies of the HOMO (highest occupied molecular orbital) and the LUMO (lowest unoccupied molecular orbital) of DCM and TPP in absorption and fluorescence. Third, for the DCM-TPP complex, the nonphotochemical quenching mechanism via ICT is investigated. The theoretical results show that the energetically lowest ICT state corresponds to a pure HOMO-LUMO transition, where the densities of the HOMO and LUMO are strictly located on the DCM and TPP moieties, respectively. Thus, the lowest ICT state corresponds to an excitation of an electron from the HOMO of DCM to the LUMO of TPP.
https://doi.org/10.1021/jp060275m
Quantum mechanical magnetic-field-gradient drift velocity: an analytically solvable model. - In: Physical review. Condensed matter and materials physics / American Physical Society. - College Park, Md. : APS, 1970-2015 , ISSN: 1550-235X , ZDB-ID: 1473011-X, ISSN 1550-235X, Bd. 72 (2005), 16, S. 161308, insges. 4 S.
http://dx.doi.org/10.1103/PhysRevB.72.161308
Surface reaction of C60 with atomic hydrogen: formation of a protecting hydrocarbon layer. - In: Fullerenes, nanotubes & carbon nanostructures, ISSN 1536-4046, Bd. 13.2005, Suppl. 1, S. 131-138
The interaction of a single domain C60/InP(0 0 1)-(2x4) film during exposure to atomic hydrogen was investigated. At low hydrogen dosing, a high reactivity of the C60 molecules was detected. Presumably, the cracking of fullerene cages follows from a fast destruction of the molecular order. High dosing leads, by chemical modification, to the formation of a stable coverage of hydrocarbons, which is promising for future technological applications.
http://dx.doi.org/10.1081/FST-200039235
Near-field wave-function spectroscopy of excitons and biexcitons. - In: Physical review. Condensed matter and materials physics / American Physical Society. - College Park, Md. : APS, 1970-2015 , ISSN: 1550-235X , ZDB-ID: 1473011-X, ISSN 1550-235X, Bd. 71 (2005), 3, S. 035347, insges. 5 S.
Improvements in spatial resolution of near-field spectroscopy have recently allowed for wave-function imaging of single excitons and biexcitons localized in semiconductor quantum wells. Surprisingly, the apparent extent of the biexciton wave function was found to be considerably reduced compared to a single exciton. We analyze theoretically the image contrast in general near-field wave-function mapping, taking into account the finite spatial resolution of the experiment. In particular, we show that due to the nonlinear nature of biexciton spectroscopy, a smaller biexciton image size is expected even if the spatial resolution is insufficient to resolve the wave functions.
http://dx.doi.org/10.1103/PhysRevB.71.035347
Theory of field-induced spin reorientation transition in thin Heisenberg films. - In: Physical review. Condensed matter and materials physics / American Physical Society. - College Park, Md. : APS, 1970-2015 , ISSN: 1550-235X , ZDB-ID: 1473011-X, ISSN 1550-235X, Bd. 71 (2005), 2, S. 024428, insges. 7 S.
We consider the spin reorientation transition in a ferromagnetic Heisenberg monolayer with a second-order single-ion anisotropy as a function of temperature and external field. Up to now analytical methods give satisfying results only for the special case that the external field is aligned parallel to the easy axis of the crystal. We propose a theory based on a generalization of the Callen decoupling, which can be used for an arbritrary direction of the external field. Excellent agreement between our results and quantum Monte Carlo data is found for the field-induced reorientation at finite temperatures. Additionally, we discuss the temperature dependence of the transition in detail.
http://dx.doi.org/10.1103/PhysRevB.71.024428
Temperature dependence of interlayer exchange coupling: spin waves versus spacer effects. - In: Physical review. Condensed matter and materials physics / American Physical Society. - College Park, Md. : APS, 1970-2015 , ISSN: 1550-235X , ZDB-ID: 1473011-X, ISSN 1550-235X, Bd. 71 (2005), 17, S. 174441, insges. 9 S.
There are different mechanisms proposed to be responsible for the temperature dependence of the interlayer exchange coupling, namely, a smearing out of the spacer or interface Fermi surface and excitations and interactions of spin waves. We propose a possibility to separate both effects by calculating the excitation spectrum of an extended Heisenberg model and connecting the results with ferromagnetic resonance (FMR) experiments. To solve the Heisenberg model we use an approximation that was shown to yield excellent results. In this paper the main idea of this procedure is explained and a detailed investigation of the spin-wave contribution to the temperature dependence of FMR resonance frequencies and fields is carried out.
http://dx.doi.org/10.1103/PhysRevB.71.174441
Spectral broadening and diffusion by torsional motion in biphenyl. - In: The journal of chemical physics, ISSN 1089-7690, Bd. 123 (2005), 14, 144311, insges. 9 S.
We have studied biphenyl by time-dependent density-functional theory. In particular, we have analyzed the dependence of singlet excitation energies and transition dipoles on the torsional angle between the phenyl groups. The torsional spectrum has been computed quantum mechanically as well as semiclassically in order to understand how this influences the broadening of absorption and luminescence spectra. Our results are in best agreement with supersonic jet spectroscopy data, but also fit astonishingly well to spectra of biphenyl in condensed phase. Furthermore, we compare the torsional and vibrational relaxation and discuss qualitatively the general consequences for poly-para-phenylenes and related conjugated polymers as poly-thiophenes, considering, in particular, how side chains and solvents may affect the optical spectra.
https://doi.org/10.1063/1.2049269
Surface phonons of clean and hydrogen terminated Si(1 1 0) surfaces. - In: Surface science, ISSN 1879-2758, Bd. 582 (2005), 1/3, S. 159-172
We report an investigation of the dynamical properties of clean and monohydride-terminated Si(1 1 0) surfaces, measured by means of high resolution electron energy loss spectroscopy (HREELS). On both surfaces a number of surface phonons is observed and successfully assigned to predicted modes. A (1 x 5) reconstruction is found to be the stable surface phase corresponding to monohydride coverage of Si(1 1 0). For the SiH stretching and bending bands of this monohydride Si(1 1 0) surface we find a relatively strong dispersion along the [1 -1 0] direction. Apparently, this is related to the coupling of oscillators along the Si chains of the (1 1 0) surface. In addition, surface vibrations induced by adsorbed residual gases are measured and analysed.
http://dx.doi.org/10.1016/j.susc.2005.03.013
Charge degrees of freedom in frustrated lattice structures. - In: Physical review. Condensed matter and materials physics / American Physical Society. - College Park, Md. : APS, 1970-2015 , ISSN: 1550-235X , ZDB-ID: 1473011-X, ISSN 1550-235X, Bd. 70 (2004), 24, S. 245113, insges. 11 S.
We study numerically spinless fermions with strong nearest-neighbor repulsion V on frustrated lattice structures that show macroscopically many ground states in the absence of a kinetic energy term (hopping term). A finite hopping amplitude t lifts the macroscopic degeneracy and leads to a small number of degenerate ground states. These can be characterized by topological quantum numbers and transformation properties under symmetry operations such as particle-hole interchange. Results for the criss-crossed checkerboard lattice (two-dimensional pyrochlore lattice) with up to 32 fermions support the scenario that translational invariance is restored in the thermodynamic limit, making half-charged quasiparticles possible. A finite entropy of approximately (3?4)ln(4?3) per site is released at low temperatures kBT?tџ?Vø , much below the bare energies t,V . This is familiar from the widely studied models involving spins on frustrated lattices, but in a spinless-fermion model these low-energy excitations are necessarily related to charge degrees of freedom.
http://dx.doi.org/10.1103/PhysRevB.70.245113
About thermodynamics and statistics of moving charges. - In: Physica, ISSN 1873-2119, Bd. 324 (2003), 3/4, S. 589-605
https://doi.org/10.1016/S0378-4371(03)00055-4
Langwellige Magnonen und Phononen und rotonenähnliche Anregungen in amorphen Festkörpern, 2003. - Online-Ressource (PDF-Datei: 99 S., 1506 KB) : Ilmenau, Techn. Univ., Diss., 2003
Parallel als Druckausg. erschienen
Ausgedehnte Inhomogenitäten und Variation der Nächste-Nachbar-Abstände sind eine charakteristische Gemeinsamkeit amorpher Festkörper. Wesentliche Informationen über die (magnetische) Struktur amorpher Festkörper erhält man aus dem statischen Strukturfaktor bzw. der radialen Verteilungsfunktion. Für langwellige Magnonen und Phononen führen die Inhomogenitäten zur Dämpfung und Renormierung (Verringerung) der Stiffnesskonstanten bzw. der Schallgeschwindigkeit. Sehr langwellige Magnonen und Phononen werden an den Inhomogenitäten wie an Punktdefekten gestreut und man erhält eine Magnon- bzw. Phonon-Rayleigh-Streuung. Diese Ergebnisse folgen sowohl aus der Greenfunktionen-Theorie (Matsubara-Kaneyoshi-Formalismus) als auch - für Magnonen - aus einer quantemechanischen Störungsrechnung. Für Magnonen und Phononen mit Wellenlängen, die kürzer als die mittlere Ausdehnung der Inhomogenitäten sind, folgt eine scheinbare Gap-Energie infolge der Bildung von Wellenpaketen (Magnon-dressed Magnon bzw. Phonon-dressed Phonon). Die Zustandsdichte langwelliger Magnonen und Phononen wird einerseits durch die Renormierung der Energie und andererseits durch die Umverteilung der Zustände infolge der Inhomogenitäten sowie durch Amorphonen-Zustände geändert. Letztere sind eine neue Art von (bei kleinen Energien lokalisierten) Elementaranregungen, die aufgrund der amorphen Struktur entstehen. Die zusätzlichen Beiträge zur Zustandsdichte von niederenergetischen langwelligen Magnonen und Phononen werden als Beitrag zum Bosonen-Peak interpretiert. Die Wärmeleitfähigkeit und der inverse Wärmewiderstand der Magnonen und Phononen bei tiefen Temperaturen sinken mit wachsender Stärke und zunehmender räumlicher Ausdehnung der Inhomogenitäten. In amorphen Ferromagneten ist der Beitrag der Magnonen zur Wärmeleitfähigkeit nicht vernachlässigbar. Er kann sogar den Phononen-Beitrag überwiegen. Rotonenähnliche Anregungen (Magnon-Rotonen und Phonon-Rotonen) bilden als Wellenpakete spezifische Anregungszweige in amorphen Festkörpern, die in die erste Debye-Kugel vorreduziert werden können. Diese Vorreduktion wird als diffuser Umklapp-Prozeß an dem ersten scharfen Peak des statischen Strukturfaktors (FSDP) interpretiert. Die Magnon- und Phonon-Rotonen, dargestellt durch Wellenpakete, führen zu einer endlichen Gap- Energie im Rotonen-Minimum der Dispersionsrelation. Dabei hängt die Größe der Gap-Energie im Wesentlichen von der Breite des FSDP ab.Die vorreduzierte Dispersionsrelation der Phonon-Rotonen führt zu einem zusätzlichen Beitrag zur spezifischen Wärme amorpher Festkörper für Temperaturen oberhalb 1 K. Dieser wird als Super-Debye-Beitrag (excess specific heat) interpretiert,der für amorphe Festkörper charakteristisch ist. Die Gap-Energie des Phonon-Rotonen-Minimums bestimmt die Lage des Maximums des Super-Debye-Beitrages. - In amorphen Festkörpern besitzen die langwelligen Magnonen und Phononen einerseits und die Magnon- und Phonon-Rotonen andererseits weitreichende Gemeinsamkeiten, die auf die analogen Streu- Mechanismen für die langwelligen Anregungen bzw. die Wellenpaket-Natur der rotonenähnlichen Anregungen zurückzuführen sind.
http://www.db-thueringen.de/servlets/DocumentServlet?id=1190
Gerichtete Bewegung aus dem Chaos bei asymmetrischer Wechselwirkung unter Berücksichtigung der Translations-Rotations-Kopplung, 2002. - Online-Ressource (PDF-Datei: 130 S., 2463 KB) : Ilmenau, Techn. Univ., Diss., 2002
Parallel als Druckausg. erschienen
In der vorliegenden Dissertation wird das Verhalten von Testteilchen (TT) in einem stark verdünnten Gas von Medienteilchen (MT) analytisch und mittels Computersimulationen detailliert untersucht. Zur Vereinfachung wird das Modell eines flachen, diskusförmigen, räumlich fest orientierten TT eingeführt, um grundlegende physikalische Eigenschaften zu untersuchen. In diesemModell wird neben den drei Translationsfreiheitsgraden des TT ein zusätzlicher Rotationsfreiheitsgrad (um eine fest in Normalenrichtung orientierte Drehachse) berücksichtigt. Das Gas von MT befindet sich stets im thermodynamischen Gleichgewicht. Neben der spiegelnd-elastischen Reflexion werden besonders die nichtrivialen Wechselwirkungen: total diffus-elastische Reflexion und total inelastische Wechselwirkung (totale Akkomodation) untersucht. Im Mittelpunkt stehen TT, die im Falle einer Asymmetrie und unter bestimmten Nichtgleichgewichtsbedingungen, jedoch ohne Vorhandensein irgendwelcher Gradienten, eine kurzzeitige, gerichtete Bewegung aus dem weißen Rauschen heraus erfahren. Bei rotierenden, asymmetrischen TT (eine Seite spiegelnd-elastisch reflektierend, die andere Seite total diffus-elastisch reflektierend) treten in der systematischen Beschleunigung in Normalenrichtung neben Termen erster Ordnung auch Terme zweiter Ordnung in der Translationsgeschwindigkeit u und der Winkelgeschwindigkeit w auf. Diese Terme führen zu einer gerichteten Beschleunigung der TT, solange nicht alle Freiheitsgrade der TT zum thermodynamischen Gleichgewicht relaxiert sind. Diese systematische Beschleunigung ist proportional zu 2<u2z> - (<u2x> + <u2y>) + [<w2> - 1]. Die Terme in der eckigen Klammer, die bei nichtrotierenden TT fehlen, sind eine Folge der Translations-Rotations- Kopplung. Diese Terme werden für asymmetrische TT erstmalig erhalten. Aufgrund des Terms [<w2> - 1] zeigen asymmetrische TT, bei denen die Translationsfreiheitsgrade zum Startzeitpunkt maxwellverteilt sind und allein der Rotationsfreiheitsgrad sich im Nichtgleichgewicht befindet, eine gerichtete Beschleunigung. Zur Startzeit vollkommen ruhende TT mit einem Rotationsfreiheitsgrad erfahren eine größere gerichtete Beschleunigung als nichtrotierende TT. Für leichtere rotierende, asymmetrische TT wird erstmals ein System gekoppelter, nichtlinearer Langevin-Gleichungen hergeleitet. Diese werden mit Hilfe einer Störungsrechnung in erster Näherung gelöst. Für hinreichend schwere TT stimmt die analytische Näherungslösung für die mittlere Normalengeschwindigkeit der TT mit entsprechenden Resultaten der Computersimulation sehr gut überein. Darüber hinaus werden beidseitig spiegelnd-elastisch reflektierende, diskus- und kugelförmige TT betrachtet, die sich in einem Zylinder in Normalenrichtung bewegen können. Dabei sollen stets auf die linke bzw. rechte Seite des TT jeweils MT unterschiedlicher Masse auftreten, wobei der Druck auf beiden Seiten gleich sein soll. Daraus resultiert eine Asymmetrie der stochastischen Kraft bzgl. ihrer Stärke und Stoßfrequenz. Für diesen Fall folgt ebenfalls eine kurzzeitige, gerichtete Beschleunigung der TT, solange ihre Normalen-Freiheitsgrade nicht zum hermodynamischen Gleichgewicht relaxiert sind. Die gerichtete Beschleunigung diskusförmiger TT ist dabei größer als die kugelförmiger TT und deutlich größer, als die gerichtete Beschleunigung asymmetrischer TT.
http://www.db-thueringen.de/servlets/DocumentServlet?id=1169
Physiker als Namensgeber für die TU Ilmenau. - In: Beiträge aus dem wissenschaftlichen Leben, Bd. 5 (2001), S. 71-86
Aus dem Fachgebiet Theoretische Physik I. - In: Beiträge aus dem wissenschaftlichen Leben, Bd. 5 (2001), S. 41-43
Energy renormalization and damping of long-wavelength phonons in amorphous solids. - In: Physica status solidi, ISSN 0370-1972, Bd. 225 (2001), 2, S. 289-299
Self-energy and damping of long-wavelength magnons in amorphous ferromagnets. - In: Physica status solidi, ISSN 1521-3951, Bd. 216 (1999), 2, S. 1073-1088
http://dx.doi.org/10.1002/(SICI)1521-3951(199912)216:2<1073::AID-PSSB1073>3.0.CO;2-2
Friction coefficients and directed motion of asymmetric test particles. - In: Journal of statistical physics, ISSN 1572-9613, Bd. 86 (1997), 5/6, S. 1067-1087
http://dx.doi.org/10.1007/BF02183614
On von Weimarn's law in nucleation theory. - In: Journal of colloid and interface science, ISSN 1095-7103, Bd. 181 (1996), 2, S. 503-510
http://dx.doi.org/10.1006/jcis.1996.0407
Cluster formation and growth in segregation processes with constant rates of supply of monomers. - In: Zeitschrift für physikalische Chemie, ISSN 2196-7156, Bd. 192 (1995), S. 155-167
http://dx.doi.org/10.1524/zpch.1995.192.Part_2.155
Equilibrium properties of a polymer chain in an Euler fluid. - In: Physical review. Statistical, nonlinear, and soft matter physics / American Physical Society. - College Park, Md. : APS, January 1993-December 2015 , ISSN: 1550-2376 , ZDB-ID: 1472725-0, ISSN 1550-2376, Bd. 50 (1994), 3, S. 2139-2147
http://dx.doi.org/10.1103/PhysRevE.50.2139
General behavior of the quenched averaged spectral density with a change in the ensemble probability distribution. - In: Physical review. Statistical, nonlinear, and soft matter physics / American Physical Society. - College Park, Md. : APS, January 1993-December 2015 , ISSN: 1550-2376 , ZDB-ID: 1472725-0, ISSN 1550-2376, Bd. 47 (1993), 4, S. 2440-2443
http://dx.doi.org/10.1103/PhysRevE.47.2440