Orbital-selective charge transfer at oxygen-deficient LaAlO3/SrTiO3(001) interfaces

Density-functional theory within the local density approximation + Hubbard U approach was used to study interface electronic structures in stoichiometric and oxygen-deficient LaAlO3/SrTiO3 (LAO/STO) superlattices with regularly spaced n-type and p-type interfaces. Asymmetric behaviors between complementary n-type and p-type interfaces were revealed in terms of orbital-selective charge transfer. Extra electrons induced by oxygen vacancies at the p-type interface easily spread to the n-type interface and occupy the Ti 3d(xy) orbitals, while those induced by the vacancies at the n-type interface are strictly confined and reside in Ti 3d(x2-y2) and/or 3d(3z2-r2) orbtials. The electronic behavior of oxygen vacancies at the LAO/STO interfaces and the possibility of distinguishing between intrinsic electronic states, which are induced by the polar catastrophe, and extrinsic states due to oxygen vacancies are discussed in detail.