Superconducting Gap Anisotropy inNd1.85Ce0.15CuO4: Results from Photoemission

We have performed angle resolved photoelectron spectroscopy on the electron doped cuprate superconductor ${\mathrm{Nd}}_{1.85}{\mathrm{Ce}}_{0.15}{\mathrm{CuO}}_4$. 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 ( $\pi /2\mathrm{}$, $\pi /2\mathrm{}$). 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.