  Using first-principle many-body perturbation theory, we investigate the
optical properties of 8- borophene at two levels of approximations; the GW
method considering only the electron-electron interaction and the GW in
combination with the Bethe-Salpeter equation including electron-hole coupling.
The band structure exhibits anisotropic Dirac cones with semimetallic
character. The optical absorption spectra are obtained for different light
polarizations and we predict strong optical absorbance anisotropy. The
absorption peaks undergo a global redshift when the electron-hole interaction
is taken into account due to the formation of bound excitons which have an
anisotropic excitonic wave function.
