Berlin 2024 – wissenschaftliches Programm
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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur
KFM 9: KFM Poster Session
KFM 9.37: Poster
Montag, 18. März 2024, 18:00–20:00, Poster E
Ultrafast small-polaron dynamics in lithium niobate tantalate solid solutions studied by fs-pump, supercontinuum-probe spectroscopy — •Niklas Dömer1, Julian Koelmann1, Anton Pfannstil1, Mirco Imlau1, and Steffen Ganschow2 — 1Inst. Physics, Barbarastr. 7, Osnabrück Univ., Germany — 2Leibniz-Institut für Kristallzüchtung, Max-Born-Straße 2, Berlin, Germany
The investigation of photo-excitation, transport and recombination dynamics of optically generated small polarons with strong coupling in the model system lithium niobate tantalate (LNT, LiNbxTa1−xO3 with 0≤x≤1) enables insight into the electronic and microscopic (defect) structure of the polar oxide mixed crystal. Recently, fs-pulse induced transient absorption in LNT was studied to explore the influence of a tunable (by the composition x) intrinsic defect structure on small polaron densities, revealing new 3D hopping transport phenomena. We extended our studies using a supercontinuum light source as a probe, offering nearly gap-free spectral access for observing UV-VIS-NIR induced absorption features. We thus are able to detect broad absorption bands being associated with optically-induced small polaron hopping and analyze our findings in conjuncture with transient absorption data on long time scales (up to seconds). A microscopic model based on the simultaneous presence of two types of intrinsic antisite defect centers, NbLi and TaLi, is deduced to explain the observation of two different polaron decay channels. Financial support by the DFG (project IM 37/12-1 within the research unit FOR 5044).