Possible pseudogap behavior of electron-doped high-temperature superconductors - art. no. 100507

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 tunneling spectroscopy. At zero magnetic field, for these optimum dop ed samples no excitation gap is observed in the tunneling spectra above the transition temperature T-c. In contrast, below T-c for applied magnetic fi elds well above the resistively determined upper critical field, a clear ex citation gap at the Fermi level is found which is comparable to the superco nducting energy gap below T-c. Possible interpretations of this observation are the existence of a normal-state pseudogap in the electron doped HTS or the existence of a spatially nonuniform superconducting state.