Atomic and Electronic Structure of Twisted Ultrathin Perovskite Bilayers

The successes of van der Waals twistronics make it only natural to study similar twist-related moiré behavior in different crystal systems. One promising material family is the perovskite oxides, for which there is already experimental progress in synthesis and device fabrication. In particular, the n=1 Ruddlesden-Popper phase, A₂BO₄, forms a basic model of ultrathin perovskite bilayers. Based on the results of DFT calculations of commensurate twisted bilayers formed from A₂TiO₄ monolayers (A=Ca, Sr, Ba), with twist angles in the range of 8.8°-37°, we characterize the local environments formed by various stacking arrangements present in the full moiré structure. Furthermore, the explicit DFT calculation of the electronic structure is crucial for validation of the approximate models we construct based on the tight binding and configuration space formalism, which will be described in a companion presentation.