Superconducting gap anisotropy in Nd1.85Ce0.15CuO4:: Results from photoemission

We have performed angle resolved photoelectron spectroscopy on the electron doped cuprate superconductor Nd1.85Ce0.15CuO4 A comparison of the leading edge midpoints between the superconducting and normal states reveals a small, but finite shift of 1.5-2 meV near the (pi ,0) position, but no observable shift along the zone diagonal near (pi /2,pi /2). This is interpreted as evidence For an anisotropic superconducting gap in the electron doped materials, which is consistent with the presence of d-wave superconducting order in this cuprate superconductor.