First-principles method of propagation of tightly bound excitons: exciton band structure of LiF and verification with inelastic x-ray scattering

TL;DR

This paper introduces a computationally efficient first-principles method to model tightly bound exciton propagation, validated by experiments on LiF, and applicable to complex materials and nanostructures.

Contribution

The authors develop a novel real-space approach using an exciton kinetic kernel to describe exciton dynamics across all binding energies, verified with experimental data.

Findings

Successfully predicts three exciton bands in LiF

Quantitative agreement with inelastic x-ray scattering data

Method enables study of exciton behavior in complex environments

Abstract

We propose a simple first-principles method to describe propagation of tightly bound excitons. By viewing the exciton as a composite object (an effective Frenkel exciton in Wannier orbitals), we define an exciton kinetic kernel to encapsulate the exciton propagation and decay for all binding energy. Applied to prototypical LiF, our approach produces three exciton bands, which we verified quantitatively via inelastic x-ray scattering. The proposed real-space picture is computationally inexpensive and thus enables study of the full exciton dynamics, even in the presence of surfaces and impurity scattering. It also provides intuitive understanding to facilitate practical exciton engineering in semiconductors, strongly correlated oxides, and their nanostructures.