Regensburg 2025 – scientific programme

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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 15: Crystal Structure Defects / Real Structure / Microstructure

KFM 15.7: Talk

Thursday, March 20, 2025, 11:30–11:45, H9

An EXAFS analysis of the laser-driven tetragonal to cubic phase-transition in BaTiO₃ — •Janosch Tasto¹, Rajdwip Bhar¹, Simon Rauls¹, Marco Reinhard², Dimosthenis Sokaras², Uwe Bovensiepen¹, and Heiko Wende¹ — ¹Faculty of Physics and CENIDE, University of Duisburg-Essen — ²SLAC National Accelerator Laboratory, Stanford University

This work aims to establish time-resolved Extended X-ray Absorption Fine Structure (tr-EXAFS) spectroscopy as a methodology for solids where the structural information of the EXAFS is combined with a pump-probe setup to study local dynamic lattice processes in the time domain. As a first step along this road, the information contained in a difference-EXAFS scan between the pumped and unpumped state is analyzed.
As proof of concept, the structural cubic to tetragonal phase transition in ferroelectric BaTiO₃ is analyzed. The coexistence of displacive and order-disorder phenomena accompanying this transition is debated in the literature of this widely investigated material. Difference-EXAFS scans at the Ti-K and Ba-L₃ edge between the tetragonal and cubic phase provide a direct way to investigate changes in structure and thermal induced disorder in the vicinity of the absorbing atom. We correlate our spectroscopic findings with ab initio multiple-scattering calculations using the FEFF10 code to quantify thermal and structural contributions.
We thank the Deutsche Forschungsgemeinschaft (in the framework of the Collaborative Research Center 1242) for financial support.

Keywords: XAS; EXAFS; barium titanate; structural phase-transition