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Chirality-dependent unidirectional routing of WS2 valley photons in a nanocircuit

Nature Nanotechnology volume 17, pages 1178–1182 (2022)Cite this article

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Abstract

Valleytronics is a promising candidate to address low-energy signal transport on chip, leveraging the valley pseudospin of electrons as a new degree of freedom to encode, process and store information1,2,3,4,5,6,7. However, valley-carrier nanocircuitry is still elusive, because it essentially requires valley transport that overcomes three simultaneous challenges: high fidelity, high directionality and room-temperature operation. Here we experimentally demonstrate a nanophotonic circuit that can route valley indices of a WS2 monolayer unidirectionally via the chirality of photons. Two propagating modes are supported in the gap area of the circuit and interfere with each other to generate beating patterns, which exhibit complementary profiles for circular dipoles of different handedness. Based on the spin-dependent beating patterns, we showcase valley fidelity of chiral photons up to 98%, and the circulation directionality is measured to be 0.44 ± 0.04 at room temperature. The proposed nanocircuit can not only enable the construction of large-scale valleytronic networks but also serve as an interactive interface to integrate valleytronics3,4,5, spintronics8,9,10 and integrated photonics11,12,13, opening new possibilities for hybrid spin-valley-photon ecosystems at the nanoscale.

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Fig. 1: Schematic of the nanophotonic circuit.
Fig. 2: Principle of valley preservation.
Fig. 3: Demonstration of directional valley router.
Fig. 4: Unidirectional valley circulation among multiple channels.

Data availability

The raw data underlying the graphs of this paper are available via Figshare at https://figshare.com/articles/dataset/RAW_data_for_NNANO-22061298A.rar/20515695. Further data that support the findings of this study are available from the corresponding authors upon reasonable request.

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Acknowledgements

Y.C. acknowledges support from the start-up funding of the University of Science and Technology of China and the CAS Talents Program. This work was supported by the National Natural Science Foundation of China (Nos. 12021004, 91850113, 11774115 and 11904271) and the Basic and Applied Basic Research Major Program of Guangdong Province (No. 2019B030302003). We thank the Center of Nano-Science and Technology of Wuhan University for their support in sample fabrication. This work was partially carried out at the USTC Center for Micro and Nanoscale Research and Fabrication. D.W. acknowledges support from the National Natural Science Foundation of China (No. 61927814). A.A. acknowledges financial support from the Air Force Office of Scientific Research with MURI grant no. FA9550-18-1-0379 and the Simons Foundation. C.-W.Q. acknowledges financial support from the National Research Foundation, Prime Minister’s Office, Singapore under Competitive Research Program Award NRF-CRP22-2019-0006. C.-W.Q. is also supported by a grant (A-0005947-16-00) from the Advanced Research and Technology Innovation Centre (ARTIC).

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Author notes

  1. These authors contributed equally: Yang Chen, Shuhang Qian.

Authors and Affiliations

  1. Wuhan National Laboratory for Optoelectronics and School of Physics, Huazhong University of Science and Technology, Wuhan, China

    Yang Chen, Shuhang Qian, Kai Wang, Xiangyuan Xing, Bing Wang & Peixiang Lu

  2. Chinese Academy of Sciences Key Laboratory of Mechanical Behavior and Design of Materials, Department of Precision Machinery and Precision Instrumentation, University of Science and Technology of China, Hefei, China

    Yang Chen, Dong Wu & Jiaru Chu

  3. Department of Electrical and Computer Engineering, National University of Singapore, Kent Ridge, Singapore

    Yang Chen & Cheng-Wei Qiu

  4. Optics Valley Laboratory, Wuhan, China

    Shuhang Qian, Kai Wang, Xiangyuan Xing, Bing Wang & Peixiang Lu

  5. Department of Physics, National University of Singapore, Kent Ridge, Singapore

    Andrew Wee

  6. Department of Chemistry, National University of Singapore, Kent Ridge, Singapore

    Kian Ping Loh

  7. Photonics Initiative, Advanced Science Research Center, City University of New York, New York, NY, USA

    Andrea Alu

  8. Physics Program, Graduate Center of the City University of New York, New York, NY, USA

    Andrea Alu

  9. Hubei Key Laboratory of Optical Information and Pattern Recognition, Wuhan Institute of Technology, Wuhan, China

    Peixiang Lu

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Contributions

Y.C. and C.-W.Q. conceived the idea and designed the experiments. K.W., P.L. and C.-W.Q. supervised the project. Y.C. conducted the simulations and theoretical analysis. S.Q., X.X and K.W. performed the experiments. Y.C., K.W., and C.-W.Q analysed the data. Y.C. drafted the paper with input from all authors.

Corresponding authors

Correspondence to Kai Wang, Peixiang Lu or Cheng-Wei Qiu.

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Nature Nanotechnology thanks Jorge Quereda and Xiaomu Wang for their contribution to the peer review of this work.

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Supplementary information

Supplementary Information

Supplementary Sections 1–9.

Supplementary Video 1

The encoding, transport and decoding of the word ‘LOVE’ by the valley-preserved nanocircuit.

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Chen, Y., Qian, S., Wang, K. et al. Chirality-dependent unidirectional routing of WS2 valley photons in a nanocircuit. Nat. Nanotechnol. 17, 1178–1182 (2022). https://doi.org/10.1038/s41565-022-01217-x

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