The temperature evolution of the proximity effect in Au/La_2-xSr_xCuO₄ and La_1.55Sr_0.45CuO_4/La_2-xSr_xCuO₄ bilayers was investigated using scanning tunneling microscopy. Proximity induced gaps, centered at the chemical potential, were found to persist above the superconducting transition temperature, T_c, and up to nearly the pseudogap crossover temperature in both systems. Such independence of the spectra on the details of the normal metal cap layer is incompatible with a density-wave order origin. However, our results can be accounted for by a penetration of incoherent Cooper pairs into the normal metal above T_c.

In addition, we have investigated the spatial evolution of the anomalous c-axis zero bias conductance peak, discovered in a previous study by our group, in epitaxial La_1.88Sr_0.12CuO₄ thin films. We found an anisotropic spatial dependence of the corresponding low-energy density of states which complies with the predicted spectral features of an anti-phase ordering of the d-wave order parameter within the ab-plane. Such an ordering was recently suggested to account for the 1/8 anomaly in the high temperature superconductors and the dynamical layer decoupling recently reported to occur in the transport studies of La_15/8Ba_1/8CuO₄.