Berlin 2015 – wissenschaftliches Programm

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DF: Fachverband Dielektrische Festkörper

DF 7: Focused Session on Ferroic Domain Walls II (DF with MA)

DF 7.8: Topical Talk

Dienstag, 17. März 2015, 12:30–13:00, EB 107

Electronic reconstruction and transport at ferroelectric domain walls — •Dennis Meier — ETH Zürich, Switzerland

Unusual electronic properties arise at ferroelectric domain walls due to the low local symmetry and hypersensitivity of these natural oxide interfaces to electrostatics and strain. Such domain walls can, for instance, be highly conducting even when the host material is rather insulating. A major challenge is to understand the complex domain wall physics at the nanoscale and gain control of their properties with the ultimate goal to exploit them for designing domain-wall-based next-generation devices. In my talk I will discuss the case of domain walls in so-called improper ferroelectrics, i.e., systems in which the ferroelectric domain formation is determined by a primary order parameter other than the polarization. Due to the secondary nature of the polarization unusual domain wall configurations are stabilized, which leads to novel degrees of freedom and functionalities. Here, the multiferroic hexagonal manganites are a striking example. I will show that both positively and negatively charged ferroelectric domain walls naturally form in the as-grown state. Driven by the polarity mismatch at these walls, a variety of exotic interface effects emerge giving rise to, e.g., orientation-dependent conduction properties as well as local variations in the electrochemical interface structure. Results gained by electron microscopy, scanning-probe microscopy, and nonlinear optics will be shown, providing novel insight to the domain-wall physics across all relevant length scales from the nanometer to the millimeter regime.