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We use inelastic neutron scattering to probe magnetic excitations of an optimally electron-doped superconductor Nd$_{1.85}$Ce$_{0.15}$CuO$_{4-delta}$ above and below its superconducting transition temperature $T_c=25$ K. In addition to gradually opening a spin pseudo gap at the antiferromagnetic ordering wavevector ${bf Q}=(1/2,1/2,0)$, the effect of superconductivity is to form a resonance centered also at ${bf Q}=(1/2,1/2,0)$ but at energies above the spin pseudo gap. The intensity of the resonance develops like a superconducting order parameter, similar to those for hole-doped superconductors and electron-doped Pr$_{0.88}$LaCe$_{0.12}$CuO$_4$. The resonance is therefore a general phenomenon of cuprate superconductors, and must be fundamental to the mechanism of high-$T_c$ superconductivity.
High-resolution laser-based angle-resolved photoemission measurements have been carried out on the electron-doped (Nd$_{1.85}$Ce$_{0.15}$)CuO$_4$ high temperature superconductor. We have revealed a clear kink at $sim$60 meV in the dispersion along th
Results of low-temperature upper critical field measurements for Nd$_{2-x}$Ce$_x$CuO$_{4+delta}$ single crystals with various $x$ and nonstoichiometric disorder ($delta$) are presented. The coherence length of pair correlation $xi$ and the product $k
High-transition-temperature (high-Tc) superconductivity develops near antiferromagnetic phases, and it is possible that magnetic excitations contribute to the superconducting pairing mechanism. To assess the role of antiferromagnetism, it is essentia
We report on laser-excited angle-resolved photoemission spectroscopy (ARPES) in the electron-doped cuprate Sm(1.85)Ce(0.15)CuO(4-d). The data show the existence of a nodal hole-pocket Fermi-surface both in the normal and superconducting states. We pr
We report a study of the microwave conductivity of electron-doped Pr$_{1.85}$Ce$_{0.15}$CuO$_{4-delta}$ superconducting thin films using a cavity perturbation technique. The relative frequency shifts obtained for the samples placed at a maximum elect