Electron polarons in lithium niobate: Charge localization, lattice deformation, and optical response

F. Schmidt, A. Kozub, U. Gerstmann, W.G. Schmidt, A. Schindlmayr, Crystals 11 (2021).

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Journal Article | Published | English
Abstract
Lithium niobate (LiNbO3), a material frequently used in optical applications, hosts different kinds of polarons that significantly affect many of its physical properties. In this study, a variety of electron polarons, namely free, bound, and bipolarons, are analyzed using first-principles calculations. We perform a full structural optimization based on density-functional theory for selected intrinsic defects with special attention to the role of symmetry-breaking distortions that lower the total energy. The cations hosting the various polarons relax to a different degree, with a larger relaxation corresponding to a larger gap between the defect level and the conduction-band edge. The projected density of states reveals that the polaron states are formerly empty Nb 4d states lowered into the band gap. Optical absorption spectra are derived within the independent-particle approximation, corrected by the GW approximation that yields a wider band gap and by including excitonic effects within the Bethe-Salpeter equation. Comparing the calculated spectra with the density of states, we find that the defect peak observed in the optical absorption stems from transitions between the defect level and a continuum of empty Nb 4d states. Signatures of polarons are further analyzed in the reflectivity and other experimentally measurable optical coefficients.
Publishing Year
Journal Title
Crystals
Volume
11
Issue
5
Article Number
542
eISSN
Financial disclosure
Article Processing Charge funded by the Deutsche Forschungsgemeinschaft and the Open Access Publication Fund of LibreCat University.
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Schmidt F, Kozub A, Gerstmann U, Schmidt WG, Schindlmayr A. Electron polarons in lithium niobate: Charge localization, lattice deformation, and optical response. Crystals. 2021;11(5). doi:10.3390/cryst11050542
Schmidt, F., Kozub, A., Gerstmann, U., Schmidt, W. G., & Schindlmayr, A. (2021). Electron polarons in lithium niobate: Charge localization, lattice deformation, and optical response. Crystals, 11(5). https://doi.org/10.3390/cryst11050542
@article{Schmidt_Kozub_Gerstmann_Schmidt_Schindlmayr_2021, title={Electron polarons in lithium niobate: Charge localization, lattice deformation, and optical response}, volume={11}, DOI={10.3390/cryst11050542}, number={5542}, journal={Crystals}, publisher={MDPI}, author={Schmidt, Falko and Kozub, Agnieszka and Gerstmann, Uwe and Schmidt, Wolf Gero and Schindlmayr, Arno}, year={2021} }
Schmidt, Falko, Agnieszka Kozub, Uwe Gerstmann, Wolf Gero Schmidt, and Arno Schindlmayr. “Electron Polarons in Lithium Niobate: Charge Localization, Lattice Deformation, and Optical Response.” Crystals 11, no. 5 (2021). https://doi.org/10.3390/cryst11050542.
F. Schmidt, A. Kozub, U. Gerstmann, W. G. Schmidt, and A. Schindlmayr, “Electron polarons in lithium niobate: Charge localization, lattice deformation, and optical response,” Crystals, vol. 11, no. 5, 2021.
Schmidt, Falko, et al. “Electron Polarons in Lithium Niobate: Charge Localization, Lattice Deformation, and Optical Response.” Crystals, vol. 11, no. 5, 542, MDPI, 2021, doi:10.3390/cryst11050542.
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Electron polarons in lithium niobate: Charge localization, lattice deformation, and optical response
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