Uncovering selective excitations using the resonant profile of indirect inelastic x-ray scattering in correlated materials: Observing two-magnon scattering and relation to the dynamical structure factor

TL;DR

This study uses exact diagonalization to analyze how the resonant profile in indirect RIXS reveals different elementary excitations in correlated materials, emphasizing the importance of incident photon energy selection.

Contribution

It provides a detailed theoretical analysis of the intermediate state effects in indirect RIXS using the Hubbard model, clarifying the connection to the dynamical structure factor and highlighting the role of core-hole screening.

Findings

RIXS spectra reduce to S(q,ω) without core-hole screening.

Two-magnon excitations are prominent at specific resonant energies.

Selecting the incident energy is crucial for targeting particular excitations.

Abstract

Resonant inelastic x-ray scattering (RIXS) is a spectroscopic technique which has been widely used to study various elementary excitations in correlated and other condensed matter systems. For strongly correlated materials, besides boosting the overall signal the dependence of the resonant profile on incident photon energy is still not fully understood. Previous endeavors in connecting indirect RIXS, such as Cu K-edge for example where scattering takes place only via the core-hole created as an intermediate state, with the charge dynamical structure factor S(q,\omega) neglected complicated dependence on the intermediate state configuration. To resolve this issue, we performed an exact diagonalization study of the RIXS cross-section using the single-band Hubbard model by fully addressing the intermediate state contribution. Our results are relevant to indirect RIXS in correlated materials, such as high Tc cuprates. We demonstrate that RIXS spectra can be reduced to S(q,\omega) when there is no screening channel for the core-hole potential in the intermediate state. We also show that two-magnon excitations are highlighted at the resonant photon energy when the core-hole potential in the corresponding intermediate state is poorly screened. Our results demonstrate that different elementary excitations can be emphasized at different intermediate states, such that selecting the exact incident energy is critical when trying to capture a particular elementary excitation.