Resonant inelastic X-ray scattering study of electronic excitations in insulating KFeSe

絶縁体KFeSeにおける電子励起の共鳴非弾性X線散乱研究

Gretarsson, H.*; 野村 拓司; Jarrige, I.*; Lupascu, A.*; Upton, M. H.*; Kim, J.*; Casa, D.*; Gog, T.*; Yuan, R. H.*; Chen, Z. G.*; Wang, N. L.*; Kim, Y.-J.*

Gretarsson, H.*; Nomura, Takuji; Jarrige, I.*; Lupascu, A.*; Upton, M. H.*; Kim, J.*; Casa, D.*; Gog, T.*; Yuan, R. H.*; Chen, Z. G.*; Wang, N. L.*; Kim, Y.-J.*

We report an Fe -edge resonant inelastic X-ray scattering (RIXS) study of KFeSe. This material is an insulator, unlike many parent compounds of iron-based superconductors. We found a sharp excitation around 1 eV, which is resonantly enhanced when the incident photon energy is tuned near the pre-edge region of the absorption spectrum. The spectral weight and line shape of this excitation exhibit clear momentum dependence. In addition, we observe momentum-independent broad interband transitions at higher excitation energy of 3-7 eV. Calculations based on a 70 band orbital model, using a moderate = 2.5 eV, indicate that the 1 eV feature originates from the correlated Fe 3 electrons, with a dominant and orbital character. We find that a moderate yields a satisfying agreement with the experimental spectra, suggesting that the electron correlations in the insulating and metallic iron based superconductors are comparable.