Local interpretation of time-resolved X-ray absorption in Mott insulators: Insights from nonequilibrium dynamical mean-field theory

TL;DR

This paper develops a formalism using nonequilibrium dynamical mean-field theory to compute time-resolved X-ray absorption spectra in photo-excited Mott insulators, revealing how local state populations influence the spectral signals.

Contribution

It introduces a novel formalism linking nonequilibrium DMFT with XAS calculations, enabling better interpretation of ultrafast spectroscopic data in correlated materials.

Findings

Atomic XAS spectra approximate full nonequilibrium DMFT results.

The formalism clarifies how local state populations affect XAS signals.

Potential to combine DMFT with cluster calculations for XAS analysis.

Abstract

We present a formalism based on nonequilibrium dynamical mean field theory (DMFT) which allows to compute the time-resolved X-ray absorption spectrum (XAS) of photo-excited solids. By applying this formalism to the photo-doped half-filled and quarter-filled two-orbital Hubbard models in the Mott insulating regime we clarify how the time-resolved XAS signal reflects the nonequilibrium population of different local states. Apart from the missing broadening associated with continuum excitations, the atomic XAS spectrum computed with the nonthermal state populations provides a good approximation to the full nonequilibrium DMFT result. This suggest a route to combine the accurate DMFT description of nonequilibrum states of solids with cluster calculations of the XAS signal.