Nonequilibrium RIXS study of an electron-phonon model

TL;DR

This paper employs nonequilibrium dynamical mean field theory to analyze how electron-phonon interactions influence RIXS spectra in strongly correlated systems, revealing phonon-related features under various nonequilibrium conditions.

Contribution

It introduces a novel application of nonequilibrium DMFT to compute RIXS signals in an electron-phonon coupled model, highlighting the effects of electric fields and photo-doping.

Findings

Phonon subbands appear in spectral functions but not in RIXS in the atomic limit.

Electron hopping modifies charge excitation peaks with phonon effects.

Electric fields induce Wannier-Stark states with phonon sidebands.

Abstract

We use the nonequilibrium dynamical mean field theory formalism to compute the equilibrium and nonequilibrium resonant inelastic X-ray scattering (RIXS) signal of a strongly interacting fermionic lattice model with a coupling of dispersionless phonons to the total charge on a given site. In the atomic limit, this model produces phonon subbands in the spectral function, but not in the RIXS signal. Electron hopping processes however result in phonon-related modifications of the charge excitation peak. We discuss the equilibrium RIXS spectra and the characteristic features of nonequilibrium states induced by photo-doping and by the application of a static electric field. The latter produces features related to Wannier-Stark states, which are dressed with phonon sidebands. Thanks to the effect of field-induced localization, the phonon features can be clearly resolved even in systems with weak electron-phonon coupling.