Theory of resonant inelastic X-ray scattering in transition-metal compounds

Nomura, Takuji; Igarashi, Junichi*; Takahashi, Manabu*

Recently, electronic excitation spectra have been observed in strongly correlated electron systems such as transition-metal compounds, by utilizing the highly brilliant synchrotron radiation. Among them, momentum dependent excitation spectra are observed in resonant inelastic X-ray scattering (RIXS) experiments at the transition-metal absorption -edge in the hard X-ray regime. The microscopic theory of RIXS constructed recently by the present authors is explained. An essential point is that RIXS spectrum is closely related to the dynamical density correlation function of correlated transition-metal electrons. Spectral shapes and momentum dependence observed in several transition-metaloxides are semiquantitatively explained.