Incident energy and polarization-dependent resonant inelastic X-ray scattering study of LaCuO

Lu, L.*; Hancock, J. N.*; Chabot-Couture, G.*; Ishii, Kenji; Vajk, O. P.*; Yu, G.*; Mizuki, Junichiro; Casa, D.*; Gog, T.*; Greven, M.*

We present a detailed Cu -edge resonant inelastic X-ray scattering (RIXS) study of the Mott insulator LaCuO in the 1-7 eV energy loss range. As initially found for the high-temperature superconductor HgBaCuO, the spectra exhibit a multiplet of weakly dispersive electron-hole excitations, which are revealed by utilizing the subtle dependence of the cross section on the incident photon energy. The close similarity between the fine structures for in-plane and out-of-plane polarizations is indicative of the central role played by the 1s core hole in inducing charge excitations within the CuO planes. On the other hand, we observe a polarization dependence of the spectral weight, and careful analysis reveals two separate features near 2 eV that may be related to different charge-transfer processes. The polarization dependence indicates that the electrons contribute significantly to the RIXS cross section.