[25p-D316-1~14] 3.6 Ultrashort-pulse and high-intensity lasers

▲ [25p-D316-11] Ultrafast control of the valley and spin polarization in Transition-metal dichalcogenides

〇(PC)Arqum Hashmi¹, Shunsuke Yamada², Atsushi Yamada², Kazuhiro Yabana², Tomohito Otobe¹ (1.Kansai Photon Science Institute, National Institutes for Quantum Science and Technology (QST), Kizugawa, Kyoto 619-0215, Japan, 2.Center for Computational Sciences, University of Tsukuba, Tsukuba 305-8577, Japan)

Keywords:Nonlinear optics, Spin-orbit coupling, Valleytronics

Very short valley lifetimes (~10³–10⁶ femtoseconds (fs)) demand the ultrafast control of valley selection on fs time scale. In this work, we explore the possibility to induce valley asymmetry by single-cycle linearly polarized laser pulse in WSe₂ monolayer. The carrier-envelope phase (CEP) is the key factor to induce valley polarization by a linearly polarized single-cycle laser pulse. Our systematic study reveals that no valley asymmetry, as well as no CEP dependence, is observed in the linear-optics limit. Remarkably, linearly polarized pulse not only induces a high degree of valley polarization but also this valley polarization is robust against the field strength in the nonlinear-optics regime. Charge dynamics in the strong-field regime show quantum interference that gives rise to distinct node formation. Most importantly, we can control the position of the carrier density in the Brillouin zone by the CEP and laser intensity.