Enhanced valley polarization of graphene on h -BN under circularly polarized light irradiation

Abstract

Graphene on $h$-BN (G/hBN) has a long period moir\'e superstructure owing to the lattice mismatch between two materials. The long periodic potential caused by the moir\'e superstructure induces modulation of the electronic properties of the system. In this paper, we numerically calculate the optical conductivity of G/hBN under circularly polarized light irradiation. The lack of spatial inversion symmetry in G/hBN induces valley polarization. Furthermore, valley polarization becomes most pronounced in the infrared and terahertz regions if the twist angle between two materials is close to zero for the nondoping case, however, it is insensitive to the twist angle for the hole-doped case. These results will serve to design valleytronics devices using G/hBN.