Penetration depth of electron-doped infinite-layer Sr 0.88 La 0.12 CuO 2 + x thin films

The in-plane penetration depth of Sr0.88La0.12CuO2+x thin films at various doping obtained from oxygenreduction has been measured, using ac-susceptibility measurements. For the higher doping samples, the superfluiddensity deviates strongly from the s-wave behavior, suggesting, in analogy with other electron-dopedcuprates, a contribution from a nodal hole pocket, or a small gap on the Fermi surface such as an anisotropics-wave order parameter. The low value of the superfluid densities, likely due to a strong doping-induceddisorder, places the superconducting transition of our samples in the phase-fluctuation regime.