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

Luojun Du, Qian Zhang, Tingting Zhang, Zhiyan Jia, Jing Liang, Gui Bin Liu, Rong Yang, Dongxia Shi, Jianyong Xiang, Kaihui Liu, Zhipei Sun, Yugui Yao, Qingming Zhang, Guangyu Zhang

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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.

Original languageEnglish
Article number161404
JournalPhysical Review B
Volume100
Issue number16
DOIs
Publication statusPublished - 23 Oct 2019
MoE publication typeA1 Journal article-refereed

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  • Projects

    PREIN: Photonics Research and Innovation

    Mäkelä, K.

    01/01/201931/12/2022

    Project: Academy of Finland: Other research funding

    A-Photonics

    Pyymaki Perros, A., Rajamanickam, R., Sun, Z., Hedberg, D., Lau Kuen Yao, L., Kim, M., Dai, Y. & Du, M.

    01/01/201931/05/2021

    Project: Business Finland: New business from research ideas (TUTLI)

    Cite this

    Du, L., Zhang, Q., Zhang, T., Jia, Z., Liang, J., Liu, G. B., ... Zhang, G. (2019). Robust circular polarization of indirect Q-K transitions in bilayer 3R-W S2. Physical Review B, 100(16), [161404]. https://doi.org/10.1103/PhysRevB.100.161404