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Generation, transport and detection of valley-locked spin photocurrent in WSe2–graphene–Bi2Se3 heterostructures

Nature Nanotechnology volume 13, pages910–914(2018)Cite this article

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Abstract

Quantum optoelectronic devices capable of isolating a target degree of freedom (DoF) from other DoFs have allowed for new applications in modern information technology. Many works on solid-state spintronics have focused on methods to disentangle the spin DoF from the charge DoF1, yet many related issues remain unresolved. Although the recent advent of atomically thin transition metal dichalcogenides (TMDs) has enabled the use of valley pseudospin as an alternative DoF2,3, it is nontrivial to separate the spin DoF from the valley DoF since the time-reversal valley DoF is intrinsically locked with the spin DoF4. Here, we demonstrate lateral TMD–graphene–topological insulator hetero-devices with the possibility of such a DoF-selective measurement. We generate the valley-locked spin DoF via a circular photogalvanic effect in an electric-double-layer WSe2 transistor. The valley-locked spin photocarriers then diffuse in a submicrometre-long graphene layer, and the spin DoF is measured separately in the topological insulator via non-local electrical detection using the characteristic spin–momentum locking. Operating at room temperature, our integrated devices exhibit a non-local spin polarization degree of higher than 0.5, providing the potential for coupled opto-spin–valleytronic applications that independently exploit the valley and spin DoFs.

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Fig. 1: Proposed device scheme and electrical characterization of WSe2–graphene–TI heterostructures
Fig. 2: Light-helicity-dependent local photocurrent response of WSe2 and Bi2Se3.
Fig. 3: Non-local CPGE measurements and gate-dependent local/non-local polarizability.

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Acknowledgements

This work was supported by Samsung Research Funding Centre of Samsung Electronics under project number SRFC-MA1402-02.

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Author notes

  1. These authors contributed equally: Soonyoung Cha, Minji Noh.

Affiliations

  1. School of Electrical and Electronic Engineering, Yonsei University, Seoul, Korea

    Soonyoung Cha, Minji Noh, Hyemin Bae, Doeon Lee, Jekwan Lee, Ho-Seung Shin, Sangwan Sim & Hyunyong Choi

  2. Department of Physics and Astronomy, Seoul National University, Seoul, Korea

    Jehyun Kim, Jangyup Son & Dohun Kim

  3. Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, USA

    Jangyup Son

  4. Department of Electrical and Computer Engineering, University of Virginia, Charlottesville, VA, USA

    Doeon Lee

  5. Department of Physics, Pohang University of Science and Technology (POSTECH), Pohang, Korea

    Hoil Kim & Jun Sung Kim

  6. Centre for Artificial Low Dimensional Electronic Systems, Institute for Basic Science (IBS), Pohang, Korea

    Hoil Kim, Sangwan Sim, Moon-Ho Jo & Jun Sung Kim

  7. KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul, Korea

    Seunghoon Yang & Chul-Ho Lee

  8. Department of Materials Science and Engineering, Yonsei University, Seoul, Korea

    Sooun Lee & Wooyoung Shim

  9. Division of Advanced Materials Science and Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang, Korea

    Moon-Ho Jo

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Contributions

S.C. and M.N. contributed equally to this work. H.C. conceived the main idea and designed the experimental protocols. S.C., M.N., J.-H.K., J.S., H.B., D.L., H.S., S.Y., S.L., W.S., C.-H.L., M.-H.J. and D.K. performed the sample fabrication. S.C., S.S., M.N. and J.L. performed the CPGE measurements. H.K. and J.K. provided single crystal Bi2Se3. H.C. supervised the project. S.C., M.N. and H.C. wrote the manuscript with input from all authors.

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Correspondence to Hyunyong Choi.

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Supplementary Figures 1–6, Supplementary Tables 1–3, Supplementary References

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Cha, S., Noh, M., Kim, J. et al. Generation, transport and detection of valley-locked spin photocurrent in WSe2–graphene–Bi2Se3 heterostructures. Nature Nanotech 13, 910–914 (2018). https://doi.org/10.1038/s41565-018-0195-y

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