Orbital-selective charge transfer at oxygen-deficient LaAlO ₃/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_xyorbitals, 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.