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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 5: Poster Session KFM

KFM 5.11: Poster

Dienstag, 28. September 2021, 16:00–17:00, P

Comparative evaluation of polar oxide LiTaO₃ and LiNbO₃ by means of ultrafast transient absorption and luminescence spectroscopy — •Anton Pfannstiel, Andreas Krampf, and Mirco Imlau — Univ. of Osnabrück, School of Physics, Germany

The two model systems LiNbO₃ (LN) and LiTaO₃ (LT) are commonly assumed to show equivalent (nonlinear) optical and electrical response and that the possibility to generate self-localized quasiparticles, such as polarons and self-trapped excitons exists in both systems. The latter are thoroughly studied in LN however, for LT there is nearly no information available in literature so far. We have adressed this topic by a systematic study on pulse induced transient absorption and luminescence of LN and LT [A Krampf et al 2021 New J. Phys. 23 033016].

As a result, a qualitatively similar behavior is found that can be attributed to the presence of Nb_Li⁴⁺ and Ta_Li⁴⁺ polarons as-well-as to the formation of excitonic states localized at Nb-O-octahedra. But, a more closer inspection of the data set reveals significant differences in the temporal behavior. In particular, specific time constants are found for short- and long term relaxation.

Discussion of the results is based on the individual crystallographic characteristics, defects, optical features, but also in conjuncture with ab-initio modeling results for carrier self-localization in both systems. A conclusion for the ultrafast optical response in LiNb_xTa_1−xO₃ mixed crystals is deduced. Financial support by the DFG (IM 37/12-1, FOR5044, INST FUGG) is gratefully acknowledged.