Fabrication of high-temperature quasi-two-dimensional superconductors at the interface of a ferroelectric Ba${}_{0.8}$Sr${}_{0.2}$TiO${}_3$ film and an insulating parent compound of La${}_2$CuO${}_4$

We report the first observation of superconductivity in heterostructure consisting of an insulating ferroelectric film (Ba${}_{0.8}$Sr${}_{0.2}$TiO${}_3$) grown on an insulating parent compound of La${}_2$CuO${}_4$ with [001] orientation. The heterostructure was prepared by magnetron sputtering on a non-atomically-flat surface with inhomogeneities of the order of 1-2 nm. The measured superconducting transition temperature T${}_c$ is about 30K. We have shown that superconductivity is confined near the interface region. Application of a weak magnetic field perpendicular to the interface leads to the appearance of the finite resistance. That confirms the quasi-two-dimensional nature of the superconductive state. The proposed concept promises ferroelectrically controlled interface superconductivity which offers the possibility of novel design of electronic devices.