Robust circular polarization of indirect Q-K transitions in bilayer 3R-W S2

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Volume Title
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Date
2019-10-23
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Language
en
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Physical Review B, Volume 100, issue 16
Abstract
Valley-contrasting Berry curvature and orbital magnetic moment have led to highly selective circular polarization of direct excitons at the K valleys in transition-metal dichalcogenides. In addition to K valleys, Q valleys, another critical point in the conduction band, also possess well-defined but distinct magnetic moment. Being akin to the direct excitons at K valleys, indirect excitons associated with Q (K) valleys in the conduction (valence) band could allow circular polarization in principle. Here, we report an experimental observation of the circular polarization of indirect Q-K transitions in noncentrosymmetric bilayer 3R-WS2. In stark contrast to the circular polarization of direct excitons which depolarizes with increasing lattice temperature, the circular polarization of indirect Q-K excitons is extremely robust and independent on the temperature. Such robust circular polarization can be understood as follows: The spin-orbit coupling in the Q valley is much stronger than that in the K point of the conduction band, significantly suppressing the temperature induced valley depolarization. Our results open up opportunities for exotic valleytronics and quantum information processing applications.
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| openaire: EC/H2020/820423/EU//S2QUIP
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Du, L, Zhang, Q, Zhang, T, Jia, Z, Liang, J, Liu, G B, Yang, R, Shi, D, Xiang, J, Liu, K, Sun, Z, Yao, Y, Zhang, Q & Zhang, G 2019, ' Robust circular polarization of indirect Q-K transitions in bilayer 3R-W S2 ', Physical Review B, vol. 100, no. 16, 161404 . https://doi.org/10.1103/PhysRevB.100.161404