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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 14: Postersession KFM

KFM 14.34: Poster

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

Small bound polarons in LiTaO₃ — •Simone Sanna — Institut für Theoretische Physik, Justus-Liebig-Universität Gießen

The optical response of many oxide crystals including the electro-optic material LiNbO₃ has been successfully explained by the presence of small polarons. The latter are quasiparticles formed when the interaction of a charge carrier with the surrounding lattice is strong enough to trap the charge carrier at essentially one lattice site. While different kind of small polarons have been described [1] and demonstrated [2] in LiNbO₃, much less is known concerning the isomorphic and isoelectronic LiTaO₃. Although the existence of small bound polarons might be expected due to the high lattice polarizability, the verification of this assumption is still missing. In this work we provide the atomistic description of small bound polarons Ta_Li^5+/4+ in LiTaO₃. The calculations performed within density functional theory with Hubbard corrections predict the large lattice relaxation of the oxygen ligands associated to the electronic capture at the antisite center, which can be interpreted as due to the polaron formation. The charge distribution is localized within essentially one unit cell and resembles the atomic Fe d_z² orbitals, suggesting a scarce hybridization the Ta d orbitals.

[1] O. F. Schirmer et al., J. Phys.: Condens. Matter 21, 123201 (2009). [2] F. Freytag et al., Nature Scientific Reports 6, 36929 (2016).