Reentrance of interface superconductivity in a high-T_c cuprate heterostructure

Increasing the carrier density in a Mott insulator by chemical doping gives rise to a generic superconducting dome in high temperature superconductors. An intriguing question is whether a second superconducting dome may exist at higher dopings. Here we heavily overdope La_2-xSr_xCuO₄ (0.45 ≤ x ≤ 1.0) and discover an unprecedented reentrance of interface superconductivity in La_2-xSr_xCuO₄ /La₂CuO₄ heterostructures. As x increases, the superconductivity is weakened and completely fades away at x = 0.8; but it revives at higher doping and fully recovers at x = 1.0. This is shown to be correlated with the suppression of the interfacial charge transfer around x = 0.8 and the weak-to-strong localization crossover in the La_2-xSr_xCuO₄ layer. We further construct a theoretical model to account for the sophisticated relation between charge localization and interfacial charge transfer. Our work advances both the search for and control of new superconducting heterostructures.