Intraband motion impact to the polarization dynamics in 2D semiconductors

We consider the generation of microscopic polarization in two-dimensional semiconductors under intense optical fields in the nonresonant regime. We demonstrate that the intraband motion of quasiparticles, driven by the electric field of the laser pulse, contributes substantially to the system’s polarization. The effects of intraband motion are analyzed using the semiconductor Bloch equations. We propose a method for solving these equations by considering them in a reference frame moving along the trajectories of the quasiparticles in momentum space. We demonstrate the developed technique on transition metal dichalcogenide monolayers irradiated by strong circularly polarized infrared light. The solution is provided in the form of a power series expansion by a small parameter that naturally emerges in the system. The implications of the results are examined, and the limitations of the approach are discussed.