The phonon dispersions of $\mathrm{ Nd_{ 1.86}Ce_{ 0.14}CuO_{ 4+\delta}}$ along the $[\xi,0,0]$ direction have been determined by inelastic x-ray scattering. Compared to the undoped parent compound, the two highest longitudinal phonon branches, associated with the Cu-O bond-stretching and out-of-plane oxygen vibration, are shifted to lower energies. Moreover, an anomalous softening of the bond-stretching band is observed around $\mathbf{ q}=(0.2,0,0)$. These signatures provide evidence for strong electron-phonon coupling in this electron-doped high-temperature superconductor.
Categories: cond-mat.supr-con cond-mat.str-el