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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 language | English |
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Article number | 161404 |
Journal | Physical Review B |
Volume | 100 |
Issue number | 16 |
DOIs | |
Publication status | Published - 23 Oct 2019 |
MoE publication type | A1 Journal article-refereed |
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PREIN: Photonics Research and Innovation
01/01/2019 → 31/12/2022
Project: Academy of Finland: Other research funding
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A-Photonics
Sun, Z., Hedberg, D., Dai, Y., Du, M., Kim, M., Pyymaki Perros, A., Lau Kuen Yao, L. & Rajamanickam, R.
01/01/2019 → 31/12/2020
Project: Business Finland: New business from research ideas (TUTLI)
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S2QUIP: Scalable Two-Dimensional Quantum Integrated Photonics
Sun, Z., Du, M., Bai, X., Mohsen, A., Wang, Y., Uddin, M., Turunen, M., Hu, X. & Yoon, H. H.
01/10/2018 → 31/03/2022
Project: EU: Framework programmes funding