The Ruddlesden-Popper (RP) homologous series Srn+1TinO3n+1 provides a useful template for the study and control of the effects of dimensionality and quantum confinement on the excited state properties of the complex oxide SrTiO3. We use ab initio many-body perturbation theory within the GW approximation and the Bethe-Salpeter equation approach to calculate quasiparticle energies and absorption spectra of Srn+1TinO3n+1 for n=1-5 and Our computed direct and indirect optical gaps are in excellent agreement with spectroscopic measurements. The calculated optical spectra reproduce the main experimental features and reveal excitonic structure near the gap edge. We find that electron-hole interactions are important across the series, leading to significant exciton binding energies that increase for small n and reach a value of 330 meV for n=1, a trend attributed to increased quantum confinement. We find that the lowest-energy singlet exciton of Sr2TiO4 (n=1) localizes in the two-dimensional plane defined by the TiO2 layer, and we explain the origin of its localization.
ASJC Scopus subject areas
- Condensed Matter Physics