  Within the first principle calculations, we propose a boron and nitrogen
cluster incorporated graphene system for efficient valley polarization. The
broken spatial inversion symmetry results in high Berry curvature at K and K'
valleys of the hexagonal Brillouin zone in this semiconducting system. The
consideration of excitonic quasiparticles within GW approximation along with
their scattering processes within many-body Bethe-Salpeter equation gives rise
to an optical gap of 1.72 eV with an excitonic binding energy of 0.65 eV. Owing
to the negligible intervalley scattering, the electrons in opposite valleys are
selectively excited by left- and right-handed circular polarized lights, as
evident from the oscillator strength calculations. Therefore, this system can
exhibit circular-dichroism valley Hall effect in the presence of the in-plane
electric field. Moreover, such excitonic qubits can be exploited for
information processing.
