Charge ordering in the electron-doped superconductor Nd_2-xCe_xCuO₄

In cuprate high-temperature superconductors, an antiferromagnetic Mott insulating state can be destabilized toward unconventional superconductivity by either hole or electron doping. In hole-doped (p-type) cuprates, a charge ordering (CO) instability competes with superconductivity inside the pseudogap state.We report resonant x-ray scattering measurements that demonstrate the presence of charge ordering in the n-type cuprate Nd_2-xCe_xCuO₄ near optimal doping. We find that the CO in Nd_2-xCe_xCuO₄ occurs with similar periodicity, and along the same direction, as in p-type cuprates. However, in contrast to the latter, the CO onset in Nd_2-xCe_xCuO₄ is higher than the pseudogap temperature, and is in the temperature range where antiferromagnetic fluctuations are first detected. Our discovery opens a parallel path to the study of CO and its relationship to antiferromagnetism and superconductivity.