Using RIXS to Uncover Elementary Charge and Spin Excitations

• Published in: Physical review. X Vol. 6; no. 2; p. 021020
• Main Authors: Jia, Chunjing, Wohlfeld, Krzysztof, Wang, Yao, Moritz, Brian, Devereaux, Thomas P.
• Format: Journal Article
• Language: English
• Published: College Park American Physical Society 13.05.2016
• Subjects: CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; Complexity; Correlation; Cross-sections; Crystal lattices; Crystal structure; Cuprates; Elementary excitations; Excitation; Group 5A compounds; High temperature; Inelastic scattering; MATERIALS SCIENCE; Mathematical analysis; MATSCI; Numerical analysis; Particle spin; Photons; Resonance scattering; Spectra; Spin structure; Structure factor; Superconductors; X-ray scattering; X-rays
• ISSN: 2160-3308; 2160-3308
• DOI: 10.1103/PhysRevX.6.021020

Despite significant progress in resonant inelastic x-ray scattering (RIXS) experiments on cuprates at the Cu L -edge, a theoretical understanding of the cross section remains incomplete in terms of elementary excitations and the connection to both charge and spin structure factors. Here, we use state-of-the-art, unbiased numerical calculations to study the low-energy excitations probed by RIXS in the Hubbard model, relevant to the cuprates. The results highlight the importance of scattering geometry, in particular, both the incident and scattered x-ray photon polarization, and they demonstrate that on a qualitative level the RIXS spectral shape in the cross-polarized channel approximates that of the spin dynamical structure factor. However, in the parallel-polarized channel, the complexity of the RIXS process beyond a simple two-particle response complicates the analysis and demonstrates that approximations and expansions that attempt to relate RIXS to less complex correlation functions cannot reproduce the full diversity of RIXS spectral features.