  We investigate electronic excitations in La2-x(Br,Sr)xCuO4 using resonant
inelastic x-ray scattering (RIXS) at the oxygen K edge. RIXS spectra of the
hole-doped cuprates show clear momentum dependence below 1 eV. The spectral
weight exhibits positive dispersion and shifts to higher energy with increasing
hole concentration. Theoretical calculation of the dynamical charge structure
factor on oxygen orbitals in a three-band Hubbard model is consistent with the
experimental observation of the momentum and doping dependence, and therefore
the dispersive mode is ascribed to intraband charge excitations which have been
observed in electron-doped cuprates.
