Quasiparticle energies and excitonic effects of the two-dimensional carbon allotrope graphdiyne: Theory and experiment

We report the electronic structure and optical properties of the recently synthesized stable two-dimensional carbon allotrope graphdiyne based on first-principles calculations and experimental optical spectrum. Due to the enhanced Coulomb interaction in reduced dimensionality, the band gap of graphdiyne increases to 1.10 eV within the $GW$ many-body theory from a value of 0.44 eV within the density functional theory. The optical absorption is dominated by excitonic effects with a remarkable electron-hole binding energy of over 0.55 eV within the $GW$--Bethe-Salpeter equation calculation. Experimental optical absorption of graphdiyne films is performed, and comparison with the theoretical calculations is analyzed in detail.