Theoretical analysis of resonant inelastic x-ray scattering spectra inLaMnO3

Abstract

We analyze the resonant inelastic x-ray scattering (RIXS) spectra at the $K$ edge of Mn in the antiferromagnetic insulating manganite ${\text{LaMnO}}_{3}$. We make use of the Keldysh-type Green's function formalism, in which the RIXS intensity is described by a product of an incident-photon-dependent factor and a density-density correlation function in the $3d$ states. We calculate the former factor using the $4p$ density of states given by an ab initio band-structure calculation and the latter using a multiorbital tight-binding model. The ground state of the model Hamiltonian is evaluated within the Hartree-Fock approximation. Correlation effects are treated within the random-phase approximation (RPA). We obtain the RIXS intensity in a wide range of energy loss (2--15 eV). The spectral shape is strongly modified by the RPA correlation, showing good agreement with the experiments. The incident-photon-energy dependence also agrees well with the experiments. The present mechanism that the RIXS spectra arise from band-to-band transitions to screen the core-hole potential is quite different from the orbiton picture previously proposed, enabling a comprehensive understanding of the RIXS spectra.