  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 t2g and eg orbitals resulting in the occupation of the eg
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 eg orbitals with lobes directed towards
the vacancy and interface dxy orbitals. The reconstruction generates a
two-dimensional interface magnetic state not observed in bulk SrTiO3. Using
generalized gradient approximation (LSDA) with intra-atomic Coulomb repulsion
(GGA+U), we find that this magnetic state is common for titanate surfaces and
interfaces.
