Research topics
Emmy Noether Research Group
The group investigates many-body effects in transition metal oxides (TMOs) and related heterostructures, which contain confined electronic systems. Focusing largely on the charge sector, the experimental approach is aiming at clarifying questions of high scientific relevance. The relation between charge inhomogeneities and charge dynamics in doped cuprates is one important issue. Another topic is the microscopic physics at the interfaces in TMO heterostructures, which triggers the unusual electronic properties of these systems. On the experimental site this also includes the advancement and development of new synchrotron radiation techniques like low-energy ARPES, RIXS and RSXS (see techniques).
Specifically, the current research projects include:
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electronic ordering and charge dynamics in two dimensions
The relation of charge dynamics and electronic ordering tendencies in two-dimensional correlated electron systems is subject of ongoing and intense world-wide research efforts. We want to address exactly this point by studying this relation in HTSCs and transition metal dichalcogenides (TMDs). The central questions addressed here are: What is the relation between charge inhomogeneities and charge dynamics in HTSCs and TMDs? Do charge inhomogeneities support or suppress superconductivity? What is the origin of the pseudogap in these compounds? What is the role played by electron-phonon and electron-spin interactions for the studied phenomena? The answers to these questions are currently debated intensively and of vital importance for the understanding of high-temperature superconductivity. Neutron scattering experiments have provided most important information about the spin dynamics in these systems. Here we apply novel synchrotron radiation based experiments to explore the charge sector in more detail.
- spin and charge dynamics in hole doped CuO2-chains
We will concentrate on Ca2+xY2-xCu5O10 (CYCO), but there are currently efforts being made to prepare further electrochemically doped materials containing CuO2-chains. CYCO is a well suited model system that allows studying the physics of different mixtures of Zhang-Rice singlets and spins in one dimension. In addition to this, we want to explore the charge ordering and spin ordering tendencies at different doping levels. The issues tackled here are directly related to the project described above. They concern the relation between electronic correlations, electronic ordering tendencies and charge dynamics as well as the coupling of spin, charge and lattice degrees of freedom. The goal is to significantly improve our understanding of the correlated electron behavior in the doped cuprates, by comparing the experimental data to realistic model calculations.
- spectroscopic studies of TMO-heterostructures
The goal here is to determine the microscopic mechanisms that dictate the electronic properties of interfaces in TMO heterostructures. More to the point, we want to study interface phenomena related to electronic and ionic reconstruction, broken symmetry and strain. This is a topic of high technological relevance. A very important point is that scientist nowadays manage to control interfaces in these TMO-heterostructures on an atomic level. The addressed questions include: How does the electronic charge density close to EF change at an interface? What roles play electronic ordering phenomena at an interface? How do the quasiparticle dynamics in a film change with respect to the bulk? How can we access the electronic structure of a buried interface?
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