Waveform control of currents in graphene by chirped few-cycle lasers

The residual current density in monolayer graphene driven by an intense few-cycle chirped laser pulse is investigated via numerical solution of the time-dependent Schrödinger equation in the light-field-driven regime. Strikingly, it is found that a purely chirped laser pulse breaks the inversion symmetry in graphene, generating a residual directional current, which is absent for a Fourier-transform limited pulse (2017 Nature 550 224) and is attributed to the chirp-dependent Landau-Zener-Stückelberg interference among different quantum pathways in the reciprocal space. Moreover, the directionality of such a current changes with laser chirp rate following a sine-functional way, which possibly provides a novel application in ultrafast photo-electronics based on two-dimensional materials.