First-principles calculation of photocurrent in monolayer silicene sheet under small voltages

We report a calculation of photocurrent in monolayer silicene generated by the illumination of linearly and circularly polarized lights based on density functional theory within the nonequilibrium Green's function formalism. In a photoenergy range from 0.1 to 2.0 eV, the silicene shows a robust photoresponse to the polarized light. There are two peaks located at 0.1 and 1.7 eV, corresponding to the strong photoexcitation in the M and K points in the Brillouin zone of the silicene. The peak photoresponse in the armchair direction is larger than that in zigzag direction, indicating the anisotropy in optics along these two directions. We also found that the photocurrent saturates at the voltages of 0.6 V for both the linear and circular lights in the zigzag and armchair directions.