Growth and Electronic Structure of Copper Oxide Monolayer Epitaxial Films

Copper-based high-temperature superconductors share a common feature in their crystal structure, which is the presence of a CuO₂ plane, where superconductivity takes place. Therefore, important questions arise as to whether superconductivity can exist in a single layer of the CuO₂ plane and, if so, how such superconductivity in a single CuO₂ plane differs from that in a bulk cuprate system. To answer these questions, studies of the superconductivity in cuprate monolayers are necessary. In this study, we constructed a heterostructure system with a La_2-SrCuO₄ (LSCO) monolayer containing a single CuO₂ plane and measured the resulting electronic structures. Monolayer LSCO has metallic and bulk-like electronic structures. The hole doping ratio of the monolayer LSCO is found to depend on the underlying buffer layer due to the interface effect. Our work will provide a platform for research into ideal two-dimensional cuprate systems.