[21p-C301-1~10] 3.12 Semiconductor optical devices (formerly 3.13)

▲ [21p-C301-4] Valley-selective excitations in TMD monolayer by ω+2ω pulses

〇(PC)Arqum Hashmi¹, Shunsuke Yamada¹, 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:TDDFT, TMD's, Valleytronics

Monolayer valley semiconductors, such as tungsten diselenide (WSe₂), possess valley pseudospin degrees of freedom that are optically addressable but degenerate in energy. Lifting the energy degeneracy by breaking time-reversal symmetry is vital for valley manipulation. So far, it has been believed that selective excitation of the desired valley in the Brillouin zone of a hexagonal two-dimensional material has to rely on using circularly polarized fields. By using the time-dependent density functional theory, we theoretically demonstrate that two-color pulses with a controlled carrier-envelope phase induce a high degree of valley polarization in the WSe₂ monolayer. The field consists of two linearly polarized components with orthogonal polarizations, while the frequencies are the fundamental (ω) and its second harmonic pulse (2ω). The carrier-envelope phase between two pulses is used to control valley polarization. Our results reveal a convenient new path toward the optical control of valley pseudospins.