The theory of continuum charge excitations in high-valence transition-metal oxides revealed by resonant inelastic x-ray scattering

*Mathias Winder (1), Atsushi Hariki (1), and Jan Kuneš (1,2)
(1) Institute for Solid State Physics, TU Wien, 1040 Vienna, Austria, (2) Institute of Physics, Czech Academy of Sciences, Na Slovance 2, 182 21 Praha 8, Czechia

We present a computational study of L-edge resonant inelastic x-ray scattering (RIXS) in 3d high-valence transition-metal (TM) oxides: RNiO3 (R: rare-earth element); LaCuO3 and NaCuO2 [1]. We employ a theoretical approach based on local density approximation (LDA) and dynamical mean-field theory (DMFT), where the Anderson impurity model with DMFT hybridization function is extended to include TM 2p core orbitals. The heart of the present approach is the configuration-interaction-based exact-diagonalization impurity solver that allows to include the low-energy electron-hole pairs accurately, necessary to describe RIXS in the high-valence materials with negative charge-transfer energy. The LDA+DMFT approach enables to describe both bound and unbound electron-hole pair excitations in the RIXS spectra. In this talk, we discuss the behavior of the fluorescence-like (FL) feature and how it is connected to the low-energy valence states and crystal structure. Special attention will be paid to the selection rules for the visibility of the FL RIXS feature, that reflect the lattice geometry around the x-ray excited TM site. Our results reproduce the recent experimental data for RNiO3 [2].

[1] A. Hariki, M. Winder, and J. Kuneš, Phys. Rev. Lett. 121, 126403 (2018).

[2] V. Bisogni, S. Catalano, R. J. Green, M. Gibert, R. Scherwitzl, Y. Huang, V. N. Strocov, P. Zubko, S. Balandeh, J.-M. Triscone, G. Sawatzky, and T. Schmitt, Nat. Commun. 7, 13017 (2016).