Direct observation of a nonmonotonic dx2-y2 -: Wave superconducting gap in the electron-doped High-Tc superconductor Pr0.89LaCe0.11CuO4 -: art. no. 017003

We performed high-resolution angle-resolved photoemission spectroscopy on electron-doped high-T-c superconductor Pr0.89LaCe0.11CuO4 to study the anisotropy of the superconducting gap. The observed momentum dependence is basically consistent with the d(x2-y2)-wave symmetry, but obviously deviates from the monotonic d(x2-y2) gap function. The maximum gap is observed not at the zone boundary, but at the hot spot where the antiferromagnetic spin fluctuation strongly couples to the electrons on the Fermi surface. The present experimental results suggest the spin-mediated pairing mechanism in electron-doped high-T-c superconductors.