Momentum dependence of resonant inelastic x-ray scattering spectrum in insulating cuprates

The resonant inelastic x-ray scattering spectrum in insulating cuprates is examined by using the exact diagonalization technique on small clusters in the two-dimensional Hubbard model with second and third neighbor hopping te rms. When the incident photon energy is tuned near the Cu K absorption edge s, we find that the features of the unoccupied upper Hubbard band can be ex tracted from the spectrum through an anisotropic momentum dependence. They provide an opportunity for the understanding of the different behavior of h ole- and electron-doped superconductors.