Electronic reconstruction and enhanced superconductivity at La _1.6xNd _0.4Sr _xCuO ₄/La _1.55Sr _0.45CuO ₄ bilayer interface

We report enhanced superconductivity in bilayer thin films consisting of superconducting La _1.6xNd _0.4Sr _xCuO ₄ with 0.06x<0.20 and metallic but non-superconducting La _1.55Sr _0.45CuO ₄. These bilayers show a maximum increase in superconducting transition temperature (T _c) of more than 200% for x=0.06, while no change in T _c is observed for the bilayers with x0.20. The analysis of the critical current and kinetic inductance data suggests 2-3 unit cells thick interfacial layer electronically perturbed to have a higher T _c. A simple charge transfer model with cation intermixing explains the observed T _c in bilayers. Still the unusually large thickness of interfacial superconducting layers cannot be explained in terms of this model. We believe that the stripe relaxation as well as the proximity effect also influence the superconductivity of the interface.