Bilayer graphene in strong ultrafast laser fields

We theoretically investigate the interaction of an ultrastrong femtosecond-long linearly polarized optical pulse with AB-stacked bilayer graphene (BLG). The pulse excite electrons from the valence into the conduction band (CB), resulting in finite CB population. Such a redistribution of electrons results in the generation of current which can be manipulated by the angle of incidence of the pulse. For the normal incidence, the current along a direction transverse to the polarization of the optical pulse is zero. However, the interlayer symmetry is broken up by a finite angle of incidence due to which BLG possesses a single axis of symmetry. Thus, for an oblique incidence, if the pulse is polarized normal to the symmetry axis then there is an induction of electric current in the direction perpendicular to the polarization of the pulse. We show that the magnitude and the direction of such a current as well as charge transfer along this direction can be manipulated by tuning the angle of incidence of the laser pulse. Further, the symmetry of the system prohibits the generation of transverse current if the pulse is polarized along the axis of symmetry of BLG.