Contribution of drift photocurrent in bulk and monolayer SnS2 probed by terahertz emission spectroscopy

We report the optical response of layered bulk and monolayer SnS2 at the surface. The physical mechanism for terahertz (THz) emission in bulk and monolayer SnS2 has been proposed. At 40° incident angle, the drift current accompanied by the surface nonlinear polarization concurrently contribute to THz surface emission in bulk SnS2. The THz radiation in monolayer SnS2 is mainly attributed to the drift photocurrent, which is insensitive to the crystalline symmetry and the pump polarization direction. The corresponding investigation could not only help to clarify the relationship of layer-dependent optical properties, but also make a significant contribution in understanding the nonlinear physical process in other transition metal dichalcogenides (TMDs) materials.