Interface hole doping in cuprate-titanate superlattices

The electronic structure of interfaces between YBa2Cu3O6 and SrTiO3 is studied using local spin density approximation (LSDA) with intra-atomic Coulomb repulsion (LSDA+U). We find a metallic state in cuprate-titanate heterostructures with the hole carriers concentrated substantially in the CuO2 layers and in the first interface TiO2 and SrO planes. This effective interface doping appears due to the polarity of interfaces, caused by the first incomplete copper oxide unit cell. Interface-induced high predoping of CuO2 layers is a key mechanism controlling the superconducting properties in engineered field-effect devices realized on the basis of cuprate-titanate superlattices.