Infrared and Raman spectroscopy ofNd2CuO4-based superconductors

We report infrared and Raman measurements of phonons in the recently discovered electron-doped superconductors ${\mathrm{Nd}}_{2\mathrm{-}\mathit{x}}$(Ce,Th${)}_{\mathit{x}}$ ${\mathrm{CuO}}_4$, and undoped ${\mathrm{Nd}}_2$ ${\mathrm{CuO}}_4$. Utilizing data from ceramics and ab-plane single crystals, we have identified all of the expected infrared-active modes (3${\mathit{A}}_{2\mathit{u}}$+4${\mathit{E}}_{\mathit{u}}$). We have also observed the Raman modes for motion along the c axis in the pure and doped materials. Based on our data and group theory, we assign the observed phonons. Finally, we compare the phonons in this class of materials to those of the related hole superconductors based upon ${\mathrm{La}}_2$ ${\mathrm{CuO}}_4$.