Excitonic effects on the optical response of graphene and bilayer graphene.
We present first-principles calculations of many-electron effects on the optical response of graphene, bilayer graphene, and graphite employing the GW-Bethe Salpeter equation approach. We find that resonant excitons are formed in these two-dimensional semimetals. The resonant excitons give rise to a prominent peak in the absorption spectrum near 4.5 eV with a different line shape and significantly redshifted peak position from those of an absorption peak arising from interband transitions in an independent quasiparticle picture. In the infrared regime, our calculated optical absorbance per graphene layer is approximately a constant, 2.4%, in agreement with recent experiments; additional low frequency features are found for bilayer graphene because of band structure effects.
Yang
Li
L
Department of Physics, University of California at Berkeley, Berkeley, California 94720, USA.
Deslippe
Jack
J
Park
Cheol-Hwan
CH
Cohen
Marvin L
ML
Louie
Steven G
SG