Recurrence of superconductivity in thickness-gradient La1.81Ce0.19CuO4−δ film

We report a systematic study of the thickness effect on the superconductivity of overdoped $\mathrm{L}{\mathrm{a}}_{2-x}\mathrm{C}{\mathrm{e}}_x\mathrm{Cu}{\mathrm{O}}_{4-\delta }$ films. As the film thickness decreases, a recurrence of superconductivity is observed in the $x=0.19$ film, while this doping level is commonly expected to show Fermi liquid behavior. The superconducting critical temperatures exhibit a domelike shape with varying thickness. The magnetic susceptibility measurements suggest that the presence of superconductivity in thin films should be filamentary. The combined effect of stress and oxygen in the thickness-gradient films is proposed to comprehend the experimental observations. Our findings provide new perspectives on superconductivity in other systems, such as the hotly debated nickelate superconductors.