Third‐Order Susceptibility of Lithium Niobate: Influence of Polarons and Bipolarons

• Published in: physica status solidi (b) 2023-02, Vol.260 (2), p.n/a
• Main Authors: Kozub, Agnieszka L., Gerstmann, Uwe, Schmidt, Wolf Gero
• Format: Article
• Language: English
• Subjects: density-functional theory; lithium niobate; polarons; third-harmonic generation
• ISSN: 0370-1972; 1521-3951
• DOI: 10.1002/pssb.202200453

The third‐order susceptibility χ(3) of lithium niobate (LiNbO3) is calculated within a Berry‐phase formulation of the dynamical polarization based on the electronic structure obtained within density‐functional theory (DFT). Maximum |χzzzz(3)| values of the order of 10−19 m2 V−2 are calculated for photon energies between 1.2 and 2 eV, i.e., in the lower half of the optical bandgap of lithium niobate. Both free and bound electron (bi)polarons are found to lead to a remarkable enhancement of the third‐order susceptibility for photon energies below 1 eV. The third‐order susceptibility χ3 of electron polarons in lithium niobate is calculated within a Berry‐phase formulation of the dynamical polarization based on density functional theory. Free and bound electron (bi)polarons lead to a remarkable enhancement of χ3 for photon energies below 1 eV, providing maximum values of the order of 2 × 10−19 m2 V−2.