Efficient computation of optical excitations in two-dimensional materials with the Xatu code

TL;DR

This paper presents an efficient numerical method for calculating optical excitations in two-dimensional materials using a simplified Bethe-Salpeter equation implementation, enabling practical analysis beyond traditional computational limits.

Contribution

The authors introduce a computationally efficient approach for excitonic spectra in 2D materials using simplified models and local orbitals, compatible with tight-binding and DFT calculations.

Findings

Accurate excitonic spectra for hBN and MoS2

Comparable results to more complex first-principles methods

Enhanced computational efficiency for 2D materials

Abstract

Here we describe an efficient numerical implementation of the Bethe-Salpeter equation to obtain the excitonic spectrum of semiconductors. This is done on the electronic structure calculated either at the simplest tight-binding level or through density funcional theory calculations based on local orbitals. We use a simplified model for the electron-electron interactions which considers atomic orbitals as point-like orbitals and a phenomenological screening. The optical conductivity can then be optionally computed within the Kubo formalism. Our results for paradigmatic two-dimensional materials such as hBN and MoS2, when compared with those of more sophisticated first-principles methods, are excellent and envision a practical use of our implementation beyond the computational limitations of such methods.