Improved quasiparticle self-consistent electronic band structure and excitons in $\beta$-LiGaO$_2$

TL;DR

This paper presents advanced quasiparticle calculations of $eta$-LiGaO$_2$'s electronic structure, revealing a larger band gap, significant exciton binding energies, and a Rydberg-like exciton series, aligning well with experimental data.

Contribution

It introduces an improved QS$G ext{ extasciitilde}W$ method including electron-hole interactions, providing more accurate band gaps and exciton properties for $eta$-LiGaO$_2$.

Findings

Band gap of about 7.0 eV with improved convergence.

Exciton gap of about 6.0 eV after zero-point-motion correction.

Identification of a Rydberg-like exciton series modified by anisotropy.

Abstract

The band structure of $\beta$-LiGaO$_2$ is calculated using the quasiparticle self-consistent QS$G\hat W$ method where the screened Coulomb interaction $\hat W$ is evaluated including electron-hole interaction ladder diagrams and $G$ is the one-electron Green's function. Improved convergence compared to previous calculations leads to a significantly larger band gap of about 7.0 eV. However, exciton binding energies are found to be large and lead to an exciton gap of about 6.0 eV if also a zero-point-motion correction of about $-0.4$ eV is included. These results are in excellent agreement with recent experimental results on the onset of absorption. Besides the excitons observed thus far, the calculations indicate the existence of a Rydberg-like series of exciton excited states, which is however modified from the classical Wannier exciton model by the anisotropies of the material and the more complex mixing of Bloch states in the excitons resulting from the Bethe-Salpeter equation. The exciton fine structure and the exciton wave functions are visualized and analyzed in various ways.