Ultrafast femtosecond laser control of electron dynamics in two-dimensional strong spin-orbit coupling materials

点击翻译按钮获取中文摘要

By using Time-dependent density functional theory (TDDFT) based on the Maxwell-TDDFT scheme, the combined classical Maxwell plus time-dependent Kohn-Sham (TDKS) equations are used to describe the propagation of electromagnetic fields. Regarding the ultrafast electron dynamics in 2D layers of Transition metal dichalcogenides, I investigated the carrier dynamics in terms of valley polarization in WSe2 monolayer via single and two-color laser field.The valley selection rules suggest that linearly polarized light couples equally to both valleys and valley polarization cannot be achieved by a linearly polarized field. My study is focused on the above-mentioned argument and we aimed to induce valley asymmetry by linearly polarized pulses which are considered not achievable by a linearly polarized field.It is possible to create an asymmetric laser field by mixing a fundamental frequency and its second harmonic. The two pulses intensity ratio and the relative carrier-envelope phase (CEP) control the valley polarization. I compared the valley polarization results of two-color laser scheme results with the single color pulse. I found that the valley polarization via two-color control exceeds the single-color scheme by 1.2 times as the two-colors field exhibits more asymmetry in its temporal shape. The results reveal a convenient new path toward the optical control of valley pseudospins.