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- DFT: molecular systems and transport
Ulrich Eckern
()

The goal of our project is the realistic description of electronic transport across complex structures, including transport through molecules. We will address this problem with two complementary methods. The density functional theory (DFT) within the local density approximation (LDA) is our method of choice to obtainNon-Equilibrium Green's function transport methods (NEGF). information for the electronic structure of the leads and the molecules. The transport properties are calculated with Non-Equilibrium Green's function transport methods (NEGF). - Electronic Structure at Interfaces
Ulrich Eckern
()

Applying density functional theory, we study a variety of interfaces. In one of the projects, we consider the interfaces between simple and correlated metals, for example, thin films of oxide high-temperature superconductors on metal substrates, in another one the metallic interface which may be formed between two insulators. Other important topics are organic/inorganic interfaces and the self-organisation of, for example, platinum chains on a germanium substrate. In addition, we investigate low-dimensional structures embedded in complex systems, like the spin chains in Sr_{14}Cu_{24}O_{41}. - DFT Calculations for Lattice Models
Ulrich Eckern
()

It is a well-known fact that the density functional theory provides a realistic description of a multitude of complex materials including interfaces and surfaces. This project aims at gaining new insights into the limitations of density functional theory. This is accomplished by studying simple lattice models whose properties are exactly known. - Dynamics of Quantum States and Phase transitions
Klaus Ziegler and collaborators
()

The properties of ultracold bosonic and fermionic gases are studied with analytic and numerical methods. Central questions are related to phase transitions (BEC-Mott transition in a Bose gas, spin-ordering transition in a fermionic gas), dynamics of quantum gases and the formation of vortices in a BEC of a strongly interacting Bose gas. - Organic Phosphorescent Area Light (OPAL 2008)
Prof. Dr. Wolfgang Brütting
(Experimentalphysik IV)

This project aims to develop optimised OLED structures on the basis of low-molecular materials for applications in lighting technology. By combining numerical simulations with experimental studies of the optical emission properties the structure of OLED with regard to a highly efficient, angle-independent emission of white light is to be optimized. - FOROXID: Magneto-Optical Sensorics
Prof. Dr. Bernd Stritzker
(Experimentalphysik IV)

This project aims to examine or develop magneto-optical sensors for analyzing the distribution of magnetic fields or electric power and to integrate them into a light microscope. The magneto-optic sensors are based on iron-garnet layers which are to be applied to suitable substrates by means of laser ablation. To ensure a high degree of sensibility it is important to obtain layers as thick as possible, which can only be realised by a multi-layer structure. In this connection we will study the origin, the type and dynamics of defects and phases of the films and their influence on magneto-optical properties. Based on the findings, a demonstrator device will be designed. For this purpose, the layers are additionally provided with high-quality mirror layers and protective layers. - Self-organized Nanostructures of Optically Active Materials
Prof. Dr. Bernd Stritzker
(Experimentalphysik IV)

The self-organized formation of a regularly nano-patterned light source with possible properties of a distributed feedback (DFB) laser is studied. To this end, the self-organized formation of 2-dimensional photonic crystals from colloidal particles on suitable solid surfaces is investigated. The filling of fluorescent materials within the open spaces of such colloidal crystals is examined, along with the emission properties of the light emitter and the light propagation modes in the photonic crystal. The aim is to achieve strong emission in the visible to UV range of the spectrum and single-mode extraction at specific wavelengths determined by the periodicity of the photonic crystal. Based on the experience with such systems, attempts will be made to replace the fluorescent material by organic LED structures, which can be electrically contacted and operated. - Ausscheidungsvorgang von SiC in Silizium
Prof. Bernd Stritzker
(Experimentalphysik IV)

Es wird eine Computersimulation entwickelt, die den Ausscheidungsvorgang von SiC in stark kohlenstoffdotiertem kristallinen Silizium beschreibt. Der zum großen Teil noch unverstandene Ausscheidungsvorgang soll dadurch nachvollziehbar und besser kontrollierbar werden. Insbesondere soll durch die Simulation die Kinetik der beim Ausscheidungsvorgang ablaufenden Strukturveränderungen sowohl in der Ausscheidung selbst als auch in deren kristalliner Umgebung einschließlich der Spannungszustände erstmals beobachtbar werden. Mit Hilfe von verfügbaren Potentialen für Silizium und Kohlenstoff aus der Gruppe von Kai Nordlund an der Universität von Helsinki und den weitläufigen Erfahrungen dieser Gruppe im Bereich der Simulation mit diesem Materialsystem wird eine molekulardynamische Simulation erarbeitet. Die per Simulation erzielten Ergebnisse werden mit numerisch auszuwertenden transmissionselektronenmikroskopischen Abbildungen des Si-Gitters in verschiedenen Phasen des Ausscheidungsvorgangs verglichen. - Cooperative Phenomena in Solids and Ordering of Microscopic Degrees of Freedom
Prof. Dr. Wolfgang Brütting
(Experimentalphysik IV)

This project focuses on field-effect experiments on the limit surface between organic semi-conductors and anorganic dielectrics with high polarization. We will examine basic questions with regard to the transport mechanism as well as theoretical forecasts on correlation effects occurring in high charge densities in such structures. - Quantum Hall systems in microwave fields
S. Mikhailov
()

Experimental studies of quantum Hall systems under the microwave irradiation have revealed a number of new types of magnetoresistance oscillations induced by the electromagnetic waves. Some of these new phenomena have been used for the creation of innovative devices such as frequency sensitive detectors and spectrometers of microwave and terahertz radiation. The goal of this project is to develop a theory of the interaction of microwaves with two-dimensional electron systems, to explain the observed phenomena and to find the ways of improving the new device operation. - Microwave photoresponse of two-dimensional electron systems: Interplay of collective and single-particle excitations
S. Mikhailov
()

The goal of the project is to theoretically study the microwave photoresponse of two-dimensional electron systems related to the excitation of the edge magnetoplasmons in them and the resulting detection and spectroscopy of microwave radiation. - Quasiclassical Methods for Correlated Electron Systems
Ulrich Eckern
()

In this project we apply quasiclassical methods to correlated electronic systems, i.e. systems in which dynamical fluctuations of the charges and the spins are of central importance. For example, we study the applicability of these methods to Luttinger liquids, in particular, in the presence of random defects. Indeed experimentally measured zero-bias anomalies in copper nano-bridges can be explained via dynamical charge fluctuations – while the role of the corresponding spin fluctuations is still an open question. In the next step we will investigate, with the help of the extended “quasiclassics”, thermo-electric effects in disordered metals.

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- 29.05.2007