Evidence Suggesting Superconductivity at 250 K in a Sequentially Deposited Cuprate Film

An artificial cuprate compound belonging to the BiSrCaCuO family with eight adjacent CuO$_2$ layers in each building block was deposited on a single crystal of SrTiO$_3$ by sequentially imposed layer epitaxy. This compound undergoes a five order of magnitude resistivity drop with an onset near 280 kelvin and an offset at 250 kelvin. It exhibits a diamagnetic variation of susceptibility and magnetization below 290 kelvin. Additional observed features, such as strongly nonlinear conductivity, suggests superconductivity as a plausible explanation of the properties of this compound.