The absorption spectra of single-layer GaSe and GaTe in the hexagonal phase feature exciton peaks with distinct polarization selectivity. We investigate these distinct features from first-principle calculations using the GW-BSE formalisms. We show that the brightness of the exciton absorption peaks is tunable with the polarization of the light. Due to the symmetry of the bands under z-axis mirror symmetry, the bound exciton states selectively couple to either in-plane or out-of-plane polarization of the light. In particular, for a p-polarized light absorption experiment, the absorption peaks of the s-like excitons emerge at large angle of incidence, while the overall absorbance reduces over the rest of the spectrum.
@article{arxiv.1711.02713,
title = {Orbital symmetry and the optical response of single-layer monochalcogenides},
author = {Gabriel Antonius and Diana Y. Qiu and Steven G. Louie},
journal= {arXiv preprint arXiv:1711.02713},
year = {2018}
}