Charge transfer mechanism for the formation of metallic states at the KTaO₃/SrTiO₃ interface

The electronic and optical properties of the KTaO₃/SrTiO ₃ heterointerface are analyzed by the full-potential linearized augmented plane-wave approach of density functional theory. Optimization of the atomic positions points at subordinate changes in the crystal structure and chemical bonding near the interface, which is due to a minimal lattice mismatch. The creation of metallic interface states thus is not affected by structural relaxation but can be explained by charge transfer between transition metal and oxygen atoms. It is to be expected that a charge transfer is likewise important for related interfaces such as LaAlO₃/SrTiO₃. The KTaO₃/SrTiO₃ system is ideal for disentangling the complex behavior of metallic interface states, since almost no structural relaxation takes place.