Electronic excitations probed with resonant inelastic X-ray scattering

Ishii, Kenji; Tsutsui, Kenji; Ikeuchi, Kazuhiko*; Jarrige, I.; Mizuki, Junichiro; Hiraka, Haruhiro*; Yamada, Kazuyoshi*; Toyama, Takami*; Maekawa, Sadamichi; Ishii, Hirofumi*; Cai, Y. Q.*; Endo, Yasuo*

It is widely recognized that inelastic scattering of neutron and X-ray is a powerful tool to investigate dynamical properties of electrons in the energy-momentum space. Especially, inelastic X-ray scattering has become available in the last decade by utilizing brilliant synchrotron radiation X-rays. When the incident X-ray energy is tuned to an absorption edge of a constituent element of materials, resonantly enhanced electronic excitations are observed, which is called resonant inelastic X-ray scattering (RIXS). An additional characteristic arises from the resonant process, namely, the specific element selectively get involved in the observed excitations. While neutron scattering is predominantly sensitive to spin excitations, one can complementarily measure various excitations of electronic degrees of freedom, charge, spin, and orbital, with the RIXS technique. In our presentation, we show an explicit application of the element selectivity: resonant inelastic X-ray scattering of Ni-substituted LaCuO and Cu-substituted LaNiO. Resonantly enhanced charge-transfer excitations are successfully observed by tuning the incident photon energy to the K-edge of the substituted element. Combined with theoretical calculations, we will discuss the local electronic states around the substituted element which are affected through the interaction with surrounding atoms.