Magnetic field dependence of high- Tc interface superconductivity in La1.55Sr0.45CuO4/La2CuO4 heterostructures

Heterostructures made of a layer of a cuprate insulator La2CuO4 on the top of a layer of a nonsuperconducting cuprate metal La1.55Sr0.45CuO4 show high-Tc interface superconductivity confined within a single CuO2 plane. Given this extreme quasi-two-dimensional quantum confinement, it is of interest to find out how interface superconductivity behaves when exposed to an external magnetic field. With this motivation, we have performed contactless tunnel-diode-oscillator-based measurements in pulsed magnetic fields up to 56 T as well as measurements of the complex mutual inductance between a spiral coil and the film in static fields up to 3 T. Remarkably, we observe that interface superconductivity survives up to very high perpendicular fields, in excess of 40 T. Additionally, the critical magnetic field Hm(T) reveals an upward divergence with decreasing temperature, in line with vortex melting as in bulk superconducting cuprates.