Occurrence of a high-temperature superconducting phase in (CaCuO2)n/(SrTiO3)m superlattices

We report the occurrence of superconductivity, with maximum T-c = 40 K, in superlattices (SLs) based on two insulating oxides, namely CaCuO2 and SrTiO3. In these (CaCuO2)(n)/(SrTiO3)(m) SLs, the CuO2 planes belong only to CaCuO2 block, which is an antiferromagnetic insulator. Superconductivity, confined within a few unit cells at the CaCuO2/SrTiO3 interface, shows up only when the SLs are grown in a highly oxidizing atmosphere, because of extra oxygen ions entering at the interfaces. The hole doping is obtained by charge transfer from the interface layers, which thus act as charge reservoir.