Microwave electrodynamics of the electron-doped cuprate superconductors Pr2-xCexCuO4-y and Nd2-xCexCuO4-y

The pairing-state symmetry of the electron-doped cuprate superconductors is thought to be s-wave in nature, in contrast with their hole-doped counterp arts which exhibit a d-wave symmetry. We re-examine this issue based on rec ent improvements in our electron-doped materials and our measurement techni ques. We report microwave cavity perturbation measurements of the temperatu re dependence of the penetration depth of Pr2-x Ce-x CUO4-y and Nd2-xCexCUO 4-y crystals. Our data suggest that these materials do not have a large, or standard, s-wave gap in their excitation spectrum.