Phonon RIXS calculations using Green's function Momentum Average technique

Spectroscopic experiments are the most extensively used probes for characterizing the physical properties of condensed matter. However, their understanding often requires a theoretical calculation of the spectra in question, usually starting from some simplified model of the underlying system. One of the problems that are key to the understanding of many properties of materials is the physics of phonons and their interaction with the conduction electrons. These are the issues lying at the base of conventional superconductivity and it is hoped that their better understanding in high temperature superconductors might help elucidate some of the mysteries still surrounding those materials. The RIXS spectroscopy is a novel, emerging technique, that only recently started to approach the resolving power necessary to observe the phononic features. Thus, theoretical predictions concerning phonon RIXS are now becoming timely in this rapidly progressing field of research. Our aim is to use the Momentum Average Green's function technique and apply it to the problem of phonon RIXS calculations, thus going beyond the current dichotomy of exact diagonalization vs. perturbative expansion methods that are the two dominating methodologies in RIXS theory.