Photoemission study of the superconducting-gap symmetry in electron-doped high-Tc superconductors

To study the superconducting-gap symmetry in electron-doped HTSC, we performed a high-resolution ARPES on Pr0.89LaCe0.11CuO4 (optimally-doped, Tc = 26 K). Obtained momentum dependence of the superconducting gap is basically consistent with the dx2-y2-wave symmetry, but obviously deviates from the monotonic form of the dx2-y2 gap function. The maximum superconducting gap is not located at the zone boundary as expected from a simple dx2-y2-wave, but observed at the so-called hot spot where the antiferromagnetic spin fluctuation strongly couples to the electrons on the Fermi surface. This ARPES result suggests that the spin-correlation plays an essential role in the pairing mechanism of electron-doped HTSC