Impact of hole polaron formation on excitonic transitions in MgO from first principles
Phys. Rev. Materials 9, 124605 – Published 18 December, 2025
DOI: https://doi.org/10.1103/mpb2-3wrb
Abstract
We present a first-principles investigation of the excitonic properties of magnesia (MgO), an ionic insulator known to host hole polarons. We combine a density functional theory-based approach for structural relaxation in the presence of the hole and many-body perturbation theory to describe the excitonic properties. We determine that the hole polaron introduces new in-gap occupied states 0.6–0.8 eV above the valence band maximum that lead to two low-energy peaks in the optical spectrum. The predicted redshift of the lowest-energy transition due to polaron formation of 0.8 eV agrees well with the experimental Stokes shift of 0.8–0.9 eV. Analysis of the exciton wave function indicates that the electron-hole pair consists of a localized hole and delocalized electron, but that the wave function retains its Wannier-Mott character even in the presence of the hole polaron. Our study demonstrates that combining these previously established methods allows for a relatively computationally inexpensive approach to studying the exciton polaron in materials where only one charge carrier forms a polaron.
