L- edge bond spin-flip RIXS mechanism

Motivated by the observation of satellite intensity peaks above the single magnon dispersion in the L-edge resonant inelastic x-ray scattering (RIXS) spectrum, we propose a resonating valence bond (RVB) inspired RIXS mechanism that incorporates the local site ultrashort core-hole lifetime (UCL) expansion. Comparing and contrasting the RIXS spectrum calculations based on 1/S-interacting spin wave theory and Schwinger boson mean-field theory (SBMFT) formalism, we reveal that interacting spin wave theory fails to fully capture all the quantum correlations in the antiferromagnetic ordered phase. However, utilizing the SBMFT framework, with a ground state that combines Neel order and fluctuating RVB components, we demonstrate that a RIXS bond-flipping mechanism provides an alternative deeper physical explanation of the satellite intensities. Specifically, we find that the spin correlation spectra predicted by the fluctuating RVB mechanism aligns with higher order UCL expansion results. We further show that the satellite intensity above the single-magnon mode can originate both from a one-to-three-magnon hybridization vertex process and from condensed spinons exhibiting Higgs mechanism. These features reflect the interplay of quantum fluctuation, entanglement, and gauge interaction effects of quantum magnetism probed by RIXS.