Quasiparticle energies and optical response of RbTiOPO4 and KTiOAsO4

Many-body perturbation theory based on density-functional theory calculations is used to determine the quasiparticle band structures and the dielectric functions of the isomorphic ferroelectrics rubidium titanyl phosphate (RbTiOPO4) and potassium titanyl arsenide (KTiOAsO4). Self-energy corrections of more than 2 eV are found to widen the transport band gaps of both materials considerably to 5.3 and 5.2 eV, respectively. At the same time, both materials are characterized by strong exciton binding energies of 1.4 and 1.5 eV, respectively. The solution of the Bethe-Salpeter equation based on the quasiparticle energies results in onsets of the optical absorption within the range of the measured data.

Automated summary

In this study, many-body perturbation theory based on density-functional theory calculations was used to investigate the quasiparticle band structures and dielectric functions of isomorphic ferroelectrics rubidium titanyl phosphate and potassium titanyl arsenide. The self-energy corrections were found to significantly increase the transport band gaps of both materials, while strong exciton binding energies were observed.