Regensburg 2019 – scientific programme

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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 14: Postersession KFM

KFM 14.20: Poster

Wednesday, April 3, 2019, 16:00–18:30, Poster C

Influence of quasiparticle and excitonic effects on the optical signatures of polarons and bipolarons in LiNbO₃ from ab initio calculations — •Falko Schmidt, Uwe Gerstmann, Arno Schindlmayr, and Wolf Gero Schmidt — Universität Paderborn, Paderborn, Germany

Lithium niobate (LiNbO₃), a perovskite-structure ferroelectric, is widely employed in nonlinear optical applications. A direct comparison between experiment and theory is difficult, however, as this material exhibits a large concentration of intrinsic defects, which strongly influence the optical properties. To reproduce the so-called polaron and bipolaron peaks found in the experimental measurements of the absorption spectrum, we test different possible defect types embedded in a supercell. Starting from density-functional theory, we correct the Kohn-Sham band structure by GW quasiparticle shifts, while excitonic effects are incorporated by solving the Bethe-Salpeter equation. The results shed light on the possible origin of the observed peaks due to the different optical characteristics of the investigated defects.