Pseudogap like tunneling spectra in electron doped high-temperature superconductors

We have measured the low-energy quasiparticle excitation spectrum of the el ectron doped high-temperature superconductors (HTS) Nd1.85Ce0.15CuO4-y and Pr1.85Ce0.15CuO4-y as a function of temperature and applied magnetic field using grain-boundary junction tunneling spectroscopy. For these optimum dop ed samples, no excitation gap is observed in the tunneling spectra above th e superconducting critical temperature. In contrast, in applied magnetic fi elds above the resistively determined upper critical field. a clear excitat ion gap at the Fermi level of comparable size to the superconducting energy gap is present. One possible interpretation of this observation is the exi stence of a normal state pseudogap also in the electron doped HTS. (C) 2001 Elsevier Science B.V. All rights reserved.