Momentum dependent charge excitations in correlated electron systems studied by resonant inelastic X-ray scattering

相関電子系における運動量に依存した電荷励起の共鳴非弾性X線散乱による研究

石井 賢司

Ishii, Kenji

Resonant inelastic X-ray scattering (RIXS) in the hard X-ray regime is a developing experiment technique to measure charge excitations utilizing brilliant synchrotron radiation X-rays. It has a great advantage that the momentum dependence of electronic excitations can be measured unlike conventional optical method. In addition, RIXS gives element-selective excitation spectra by tuning the incident photon energy to an absorption edge of the element. There has been much activity in recent years using this technique, especially at the transition metal K-edge to study transition metal oxides. We have applied RIXS technique to correlated electron systems, such as cuprates and manganites, in order to understand their electronic structure and underlying correlation effects. In particular, electronic structure of correlated metals is in the focus of our RIXS study, because interesting phenomena, e.g. high-Tc superconductivity in cuprates and colossal magneto resistance in manganites, occur in the vicinity of metal-insulator transition by carrier doping. Here I would like to present our recent RIXS studies on high-Tc cuprates and related materials which were performed in close collaboration with theorists. Momentum and carrier-doping dependence of an interband excitation across the Mott gap and an intraband excitation below the gap will be discussed.