Theory and experiment of orbital excitations in correlated oxides

Orbital excitations in orbital-ordered transition metal oxides are investigated theoretically and experimentally. Characteristic differences in the collective orbital excitations, termed orbital waves, between the e(g) and t(2g) systems are clarified. As a probe to detect the orbital excitations, the scattering processes for the Raman scattering and the resonant and non-resonant inelastic x-ray scatterings are proposed and their scattering cross-sections are calculated. The orbital excitations in hole-doped and undoped manganites are examined experimentally by using resonant inelastic x-ray scattering. The obtained experimental results are compared with the theoretical calculations.