Effective transition operators for resonant inelastic X-ray scattering

TL;DR

This paper derives effective symmetry-based transition operators for RIXS, clarifying how polarization influences scattering between states and how these operators depend on symmetry and ground state nature.

Contribution

It introduces a method to derive effective transition operators for RIXS that account for symmetry and ground state effects, applicable to complex materials like iridium compounds.

Findings

Operators depend on symmetry and ground state properties.

Effective operators can be derived for lower symmetry systems.

Facilitates understanding of RIXS coupling to excitations.

Abstract

Effective symmetry-based transition operators for resonant inelastic X-ray scattering (RIXS) are derived that show how the scattering between different states depends on the polarization of the incoming and outgoing X-rays. In spherical symmetry, the effective operators can be rewritten in terms of spin operators, although the expressions depend on the nature of the ground state. For lower symmetries, the combined action of the crystal field and the spin-orbit interaction breaks up the spin space and spin operators are no longer appropiate operators. By taking iridium compounds as an example, it is demonstrated that effective scattering operators can still be obtained. These effective transition operators facilitate our understanding how RIXS couples to elementary excitations.