Research Activities

The activities of our department are centered around researchers having an expertise of their own. They are trained as theorists or experimentalists, as physicists or chemists. They are leading a group and follow their scientific interests independently. Together they form a team that carries out projects in a collaborative manner. They complement each other and share a common interest in various aspects of correlated materials. At present we have the following group leaders and research groups:

 

Spectroscopy is applied in a wide variety of scientific disciplines to explore matter's electronic structure. We employ synchrotron-based spectroscopic techniques such as Angle-Resolved PhotoEmission Spectroscopy (ARPES), Hard X-ray PhotoEmission Spectroscopy (HAXPES), Resonant X-ray Scattering (RXS), Non-resonant Inelastic  X-ray Scattering (NIXS), and X-ray Absorption Spectroscopy (XAS).

The focus of our research are materials in thin film form, especially transition metal and rare-earth oxides which show metal-insulator transitions and interesting magnetic properties, as well as topological insulator compounds, materials having a full insulating gap in the bulk but a topologically protected conducting surface. The properties of these fascinating materials are governed by the interplay of complex interactions. Thin films and heterostructures offer a broad platform to tune these interactions, e.g. by strain, domain size, screening, proximity effects, and doping. This can provide important insights into the fundamental mechanisms that determine the properties of a material, and enables us to manipulate the characteristics of a material, for instance by inducing or suppressing phase transitions.  

Our state-of-art in-house ultra-high vacuum system allows for the growth and in-situ characterization of high-quality thin films. It includes two molecular beam epitaxy chambers: one for oxides and one for topological insulators. The films are investigated all under ultra-high vacuum conditions by structural characterization using electron diffraction techniques (RHEED, LEED), investigation of the electronic structure of the bulk and surface by photoelectron spectroscopy (XPS, ARPES), and temperature-dependent resistivity measurements.

Strong correlations in bulk and thin films - Magnetotransport - Nanometer-scale phase separation in manganites - Scanning tunneling microscopy / spectroscopy
The study of exciting physical properties within the quantum mechanical world of condensed matter physics starts with the synthesis of high quality single crystals. Especially for polarization dependent soft-X-ray absorption (XAS), X-ray photoelectron spectroscopy (PES) and neutron scattering experiments sizeable single crystals are required. My lab is equipped with two high end floating zone mirror furnace systems with complementary growth conditions. Thus, we are able to synthesize materials also under extreme conditions.

For the study of the nuclear structure of our synthesized materials a state-of-the-art single crystal X-ray diffracometer is available in my lab. Beyond that, neutron experiments can be performed in
spallation or reactor neutron sources (fission of Uranium) around the world. In contrast to X-rays, neutron scattering results from the nuclear interaction between neutrons and cores (and not from interaction with the electron shells) as well as the magnetic interaction of the neutrons magnetic moment with the moments of the atoms which gives rise to the observation of the spin structure as well as to the study of the intriguing spin excitation spectra within our systems.

The focus of our research is the synchrotron based investigation of the f orbital occupation in Heavy Fermion compounds.

Theoretical work is focused on the effect of electronic correlations on quasiparticle renormalization in f-electron compounds and appearance of broken symmetries.

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