Ultrafast field-driven currents in gapped graphene*

We study theoretically interaction of a linearly polarized ultrashort and ultrafast optical pulse with gapped graphene monolayer. A finite conduction band population and corresponding electric currents are generated during the pulse. In gapped graphene, inversion symmetry is broken, and while one axis, is still the axis of symmetry (y-axis), the other axis (x-axis) is no longer so, which results in generation of non-trivial currents. When the incident pulse is polarized along x-axis, both the longitudinal and transverse currents are generated. Our results show that both currents strongly depend on the bandgap. The generated electric currents transfer electrical charge and make the gapped graphene electrically polarized. The transferred charge in longitudinal direction has monotonic dependence on the field amplitude and weak dependence on the bandgap, while in transverse direction, the transferred charge shows non-monotonic dependence on the field amplitude.