SKM 2023 – wissenschaftliches Programm

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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 6: Poster

KFM 6.42: Poster

Dienstag, 28. März 2023, 17:00–19:00, P3

Small-polaron dynamics in lithium niobate tantalate solid solutions studied by means of fs-pump, cw-probe spectroscopy — •Niklas Dömer¹, Anton Pfannstiel¹, Mirco Imlau¹, and Steffen Ganschow² — ¹Inst. Physics, Barbarastr. 7, Osnabrück Univ. — ²Leibniz-Institut für Kristallzüchtung (IKZ), Berlin

The inspection of transport and recombination dynamics of optically generated small polarons with strong coupling enables far-reaching insight into the electronic and microscopic (defect) structure of polar oxide crystals using macroscopic measures. Here, we use the absorption cross-section of small polarons to relate fs-pulse induced transient absorption with the temporal evolution of small polaron number densities, i.e. with the 3D hopping transport of small polarons within a lattice with intrinsic defect structure. For the first time, fs-pump continuous-wave probe spectroscopy is applied to lithium niobate tantalate (LNT, LiNb_xTa_1−xO₃ with 0≤x≤1) solid solutions. Remarkably, a two-step decay with lifetimes in the order of microseconds and minutes is uncovered, which has not been observed in the widely studied edge compositions lithium niobate (LN, x=1) and lithium tantalate (LT, x=0). This finding is studied over the entire composition range (0≤x≤1) at distinct wavelengths according to the maxima of small polaron absorption features. A microscopic model based on the simultaneous presence of two types of intrinsic antisite defect centers, Nb_Li and Ta_Li, is deduced to explain two different polaron decay channels. Financial support by the DFG (project IM 37/12-1 and GA 2403/7-1, FOR 5044).