Momentum Dependence of Charge Excitations in the Electron-Doped Superconductor Nd_(1.85)Ce_(0.15)CuO_4: A Resonant Inelastic X-Ray Scattering Study

摘要

We report a resonant inelastic x-ray scattering (RIXS) study of charge excitations in the electron-doped high-T_c superconductor Nd_(1.85)Ce_(0.15)CuO_4. The intraband and interband excitations across the Fermi energy are separated for the first time by tuning the experimental conditions properly to measure charge excitations at low energy. A dispersion relation with q-dependent width emerges clearly in the intraband excitation, while the intensity of the interband excitation is concentrated around 2 eV near the zone center. The experimental results are consistent with theoretical calculation of the RIXS spectra based on the Hubbard model.