Nanoscale structure information via coherent resonant x-ray scattering
Static and dynamic structure on the nanoscale is a common theme of the proposed VI. These structures may arise via phase separation as in the case of complex solids with many degrees of freedom (spin, orbital, charge, lattice), they can be dynamically present at phase transitions in equilibrium or they may be transient after pumping a sample into a non-equilibrium state e.g. by laser excitation of the electronic system. This project is primarily devoted to advance our access to the spatial dimension on the nanometer scale scale in these cases. X‑ray scattering and imaging techniques take advantage of specific contrast mechanisms that allow us to see the property in question with high spatial resolution. Obviously, a contrast mechanism matched to the entities to be observed is needed. For example, X-ray circular dichroism enables us to see magnetic nanodomains. Contrast for other structures such as domains with common orbital or charge order are well established for spectroscopy (and exploited in this VI), but have not been integrated as contrast mechanisms into high resolution imaging techniques.
In this project, we want to develop methods joining spectroscopy (resonant electronic transitions) and scattering/imaging for “exotic” contrast mechanisms. The systems under study will like in other projects within the VI be mixed-valence systems with metal-insulator transition (P7, P8, and P9), magnetic domains after excitation of the electronic system (P9), titanates and manganites (P8) as well as liquids (P2). Imaging methods will be based on the use of coherent X-rays for coherent diffraction imaging and holography, which allows for particular flexibility in the sample environment required to stabilize the structures to be studied. Furthermore, these techniques are compatible with imaging at FEL sources such as FLASH, LCLS and XFEL. The methods developed will thus be transferable to FELs in order to investigate spatial aspects in ultrafast, sub-picosecond dynamics. First spatially resolved studies on fs‑dynamics in magnetic systems have been carried out at FLASH and LCLS by Grübel and Eisebitt. Complementary characterization by scanning force microscopy will be available.
The goal of the project is to exploit “exotic” resonant scattering contrast for the spatial observation of nanoscale structures in complex materials.
The Methods to be developed are applicable to various materials studied in the VI (P6, P7, P8, and P9). The scattering approach connects to the projects on ultrafast diffraction and imaging at XFEL and hard X-ray storage ring sources (P1, P4, P6, P7, P8 and Stöhr, Dürr) and is complementary to the projects with ultrafast spectroscopy (P2, P3, P7, and P9).
Clemens von Korff Schmissing
Jo Stöhr - LCLS
Hermann Dürr - PULSE