Theory of x-ray scattering from optically pumped excitons in atomically thin semiconductors

TL;DR

This paper introduces a theoretical framework for analyzing x-ray scattering from optically pumped excitons in 2D semiconductors, enabling the investigation of their internal charge distribution and many-body interactions.

Contribution

It presents a novel approach to distinguish excitonic charge distributions in x-ray spectra, expanding understanding of quasiparticle dynamics in atomically thin materials.

Findings

New contribution of excitons to x-ray scattering spectra identified.

Differential spectra can isolate excitonic charge distribution.

Framework applicable to transition metal dichalcogenides (TMDCs).

Abstract

We propose a framework to explore the internal charge distribution of mesoscopic quasiparticles by inelastic x-ray scattering, while also accounting for the conventional scattering from electrons. Specifically, we investigate a new contribution of intrinsic and optically pumped excitons (bound electron-hole pairs) to the x-ray scattering spectrum of transition metal dichalcogenides (TMDCs). The optical excitation leads to the creation of Wannier exciton populations, adding new quasi-elastic processes beyond the conventional electronic features to the x-ray scattering spectra. Differential spectra (with and without optical pumping) can be used to isolate and identify the internal charge distribution of the optically pumped excitons in the scattering response, potentially offering insights into many-body interactions and quasi-particle dynamics in 2D systems.