We show that oxygen vacancies at titanate interfaces induce a complex multiorbital reconstruction which involves a lowering of the local symmetry and an inversion of $t_{2g}$ and $e_g$ orbitals resulting in the occupation of the $e_g$ orbitals of Ti atoms neighboring the O vacancy. The orbital reconstruction depends strongly on the clustering of O vacancies and can be accompanied by a magnetic splitting between the local $e_g$ orbitals with lobes directed towards the vacancy and interface $d_{xy}$ orbitals. The reconstruction generates a two-dimensional interface magnetic state not observed in bulk SrTiO${}_3$. Using generalized gradient approximation with intra-atomic Coulomb repulsion ($\text{GGA}+U$), we find that this magnetic state is common for titanate surfaces and interfaces.

• Received 20 April 2012

DOI:https://doi.org/10.1103/PhysRevB.86.064431