Free and defect-bound (bi)polarons in LiNbO3: Atomic structure and spectroscopic signatures from ab initio calculations

F. Schmidt, A. Kozub, T. Biktagirov, C. Eigner, C. Silberhorn, A. Schindlmayr, W.G. Schmidt, U. Gerstmann, Physical Review Research 2 (2020).

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Abstract
Polarons in dielectric crystals play a crucial role for applications in integrated electronics and optoelectronics. In this work, we use density-functional theory and Green's function methods to explore the microscopic structure and spectroscopic signatures of electron polarons in lithium niobate (LiNbO3). Total-energy calculations and the comparison of calculated electron paramagnetic resonance data with available measurements reveal the formation of bound polarons at Nb_Li antisite defects with a quasi-Jahn-Teller distorted, tilted configuration. The defect-formation energies further indicate that (bi)polarons may form not only at Nb_Li antisites but also at structures where the antisite Nb atom moves into a neighboring empty oxygen octahedron. Based on these structure models, and on the calculated charge-transition levels and potential-energy barriers, we propose two mechanisms for the optical and thermal splitting of bipolarons, which provide a natural explanation for the reported two-path recombination of bipolarons. Optical-response calculations based on the Bethe-Salpeter equation, in combination with available experimental data and new measurements of the optical absorption spectrum, further corroborate the geometries proposed here for free and defect-bound (bi)polarons.
Publishing Year
Journal Title
Physical Review Research
Volume
2
Issue
4
Article Number
043002
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Schmidt F, Kozub A, Biktagirov T, et al. Free and defect-bound (bi)polarons in LiNbO3: Atomic structure and spectroscopic signatures from ab initio calculations. Physical Review Research. 2020;2(4). doi:10.1103/PhysRevResearch.2.043002
Schmidt, F., Kozub, A., Biktagirov, T., Eigner, C., Silberhorn, C., Schindlmayr, A., … Gerstmann, U. (2020). Free and defect-bound (bi)polarons in LiNbO3: Atomic structure and spectroscopic signatures from ab initio calculations. Physical Review Research, 2(4). https://doi.org/10.1103/PhysRevResearch.2.043002
@article{Schmidt_Kozub_Biktagirov_Eigner_Silberhorn_Schindlmayr_Schmidt_Gerstmann_2020, title={Free and defect-bound (bi)polarons in LiNbO3: Atomic structure and spectroscopic signatures from ab initio calculations}, volume={2}, DOI={10.1103/PhysRevResearch.2.043002}, number={4043002}, journal={Physical Review Research}, publisher={American Physical Society}, author={Schmidt, Falko and Kozub, Agnieszka and Biktagirov, Timur and Eigner, Christof and Silberhorn, Christine and Schindlmayr, Arno and Schmidt, Wolf Gero and Gerstmann, Uwe}, year={2020} }
Schmidt, Falko, Agnieszka Kozub, Timur Biktagirov, Christof Eigner, Christine Silberhorn, Arno Schindlmayr, Wolf Gero Schmidt, and Uwe Gerstmann. “Free and Defect-Bound (Bi)Polarons in LiNbO3: Atomic Structure and Spectroscopic Signatures from Ab Initio Calculations.” Physical Review Research 2, no. 4 (2020). https://doi.org/10.1103/PhysRevResearch.2.043002.
F. Schmidt et al., “Free and defect-bound (bi)polarons in LiNbO3: Atomic structure and spectroscopic signatures from ab initio calculations,” Physical Review Research, vol. 2, no. 4, 2020.
Schmidt, Falko, et al. “Free and Defect-Bound (Bi)Polarons in LiNbO3: Atomic Structure and Spectroscopic Signatures from Ab Initio Calculations.” Physical Review Research, vol. 2, no. 4, 043002, American Physical Society, 2020, doi:10.1103/PhysRevResearch.2.043002.
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Free and defect-bound (bi)polarons in LiNbO3: Atomic structure and spectroscopic signatures from ab initio calculations
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