Two-color laser control of photocurrent and high harmonics in graphene

We comprehensively investigate two-color-laser-driven photocurrent and high harmonic generation (HHG) in graphene models. By numerically solving the quantum master equation, we uniformly explore a broad parameter regime including both the weak (perturbative) and intense-laser (nonperturbative) cases while considering the dissipation effects. We demonstrate that the HHG spectra can be drastically altered by tuning the real-space path traced by the laser electric field. This controllability is explained by the dynamical symmetry argument. We also show that both the magnitude and the direction of photocurrent (zeroth order harmonics) can be controlled by varying the frequency, intensity, ellipticity, and relative phase of the two-color laser. Furthermore, the nature of photocurrent is shown to be classified into shift- or injection-current types, depending on the phase of two-color laser. Our findings indicate that even in centrosymmetric electron systems, photocurrent and HHG can be quantitatively controlled by adjusting various external parameters if we utilize multicolor laser with a lower spatial or temporal symmetry.