Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

  • Article
  • Published:

Electric control of valley polarization in monolayer WSe2 using a van der Waals magnet

Nature Nanotechnology volume 17, pages 721–728 (2022)Cite this article

Subjects

Abstract

Electrical manipulation of the valley degree of freedom in transition metal dichalcogenides is central to developing valleytronics. Towards this end, ferromagnetic contacts, such as Ga(Mn)As and permalloy, have been exploited to inject spin-polarized carriers into transition metal dichalcogenides to realize valley-dependent polarization. However, these materials require either a high external magnetic field or complicated epitaxial growth steps, limiting their practical applications. Here we report van der Waals heterostructures based on a monolayer WSe2 and an Fe3GeTe2/hexagonal boron nitride ferromagnetic tunnelling contact that under a bias voltage can effectively inject spin-polarized holes into WSe2, leading to a population imbalance between ±K valleys, as confirmed by density functional theory calculations and helicity-dependent electroluminescence measurements. Under an external magnetic field, we observe that the helicity of electroluminescence flips its sign and exhibits a hysteresis loop in agreement with the magnetic hysteresis loop obtained from reflective magnetic circular dichroism characterizations on Fe3GeTe2. Our results could address key challenges of valleytronics and prove promising for van der Waals magnets for magneto-optoelectronics applications.

This is a preview of subscription content, access via your institution

Access options

Buy this article

  • Purchase on Springer Link
  • Instant access to full article PDF
Buy now

Prices may be subject to local taxes which are calculated during checkout

Fig. 1: Device structure and optical generation of valley polarization.
Fig. 2: Electrical properties and EL of vdW heterostructures.
Fig. 3: Electrical generation of valley polarization.
Fig. 4: Electronic structures of freestanding FGT monolayer.
Fig. 5: Magnetic field dependence of circular dichroism, EL and PL.

Similar content being viewed by others

Data availability

All other data that support the plots within this paper and other findings of this study are available from the corresponding authors upon reasonable request. Source data are provided with this paper.

References

  1. Xu, X. D., Yao, W., Xiao, D. & Heinz, T. F. Spin and pseudospins in layered transition metal dichalcogenides. Nat. Phys. 10, 343–350 (2014).

    Article  CAS  Google Scholar 

  2. Xiao, D., Liu, G. B., Feng, W. X., Xu, X. D. & Yao, W. Coupled spin and valley physics in monolayers of MoS2 and other group-VI dichalcogenides. Phys. Rev. Lett. 108, 196802 (2012).

    Article  CAS  Google Scholar 

  3. Mak, K. F., Xiao, D. & Shan, J. Light–valley interactions in 2D semiconductors. Nat. Photon. 12, 451–460 (2018).

    Article  CAS  Google Scholar 

  4. Zeng, H. L., Dai, J. F., Yao, W., Xiao, D. & Cui, X. D. Valley polarization in MoS2 monolayers by optical pumping. Nat. Nanotechnol. 7, 490–493 (2012).

    Article  CAS  Google Scholar 

  5. Mak, K. F., He, K. L., Shan, J. & Heinz, T. F. Control of valley polarization in monolayer MoS2 by optical helicity. Nat. Nanotechnol. 7, 494–498 (2012).

    Article  CAS  Google Scholar 

  6. Cao, T. et al. Valley-selective circular dichroism of monolayer molybdenum disulphide. Nat. Commun. 3, 887 (2012).

    Article  CAS  Google Scholar 

  7. Mak, K. F., McGill, K. L., Park, J. & McEuen, P. L. The valley Hall effect in MoS2 transistors. Science 344, 1489–1492 (2014).

    Article  CAS  Google Scholar 

  8. Onga, M., Zhang, Y. J., Ideue, T. & Iwasa, Y. Exciton Hall effect in monolayer MoS2. Nat. Mater. 16, 1193–1197 (2017).

    Article  CAS  Google Scholar 

  9. Ye, Y. et al. Electrical generation and control of the valley carriers in a monolayer transition metal dichalcogenide. Nat. Nanotechnol. 11, 598–602 (2016).

    Article  CAS  Google Scholar 

  10. Sanchez, O. L., Ovchinnikov, D., Misra, S., Allain, A. & Kis, A. Valley polarization by spin injection in a light-emitting van der Waals heterojunction. Nano Lett. 16, 5792–5797 (2016).

    Article  CAS  Google Scholar 

  11. Gong, C. & Zhang, X. Two-dimensional magnetic crystals and emergent heterostructure devices. Science 363, eaav4450 (2019).

    Article  CAS  Google Scholar 

  12. Gibertini, M., Koperski, M., Morpurgo, A. F. & Novoselov, K. S. Magnetic 2D materials and heterostructures. Nat. Nanotechnol. 14, 408–419 (2019).

    Article  CAS  Google Scholar 

  13. Burch, K. S., Mandrus, D. & Park, J. G. Magnetism in two-dimensional van der Waals materials. Nature 563, 47–52 (2018).

    Article  CAS  Google Scholar 

  14. Fei, Z. Y. et al. Two-dimensional itinerant ferromagnetism in atomically thin Fe3GeTe2. Nat. Mater. 17, 778–782 (2018).

    Article  CAS  Google Scholar 

  15. Tan, C. et al. Hard magnetic properties in nanoflake van der Waals Fe3GeTe2. Nat. Commun. 9, 1554 (2018).

    Article  CAS  Google Scholar 

  16. Deng, Y. J. et al. Gate-tunable room-temperature ferromagnetism in two-dimensional Fe3GeTe2. Nature 563, 94–99 (2018).

    Article  CAS  Google Scholar 

  17. Wang, Z. et al. Tunneling spin valves based on Fe3GeTe2/hBN/ Fe3GeTe2 van der Waals heterostructures. Nano Lett. 18, 4303–4308 (2018).

    Article  CAS  Google Scholar 

  18. Schaibley, J. R. et al. Valleytronics in 2D materials. Nat. Rev. Mater. 1, 16055 (2016).

    Article  CAS  Google Scholar 

  19. Withers, F. et al. Light-emitting diodes by band-structure engineering in van der Waals heterostructures. Nat. Mater. 14, 301–306 (2015).

    Article  CAS  Google Scholar 

  20. Liu, C. H. et al. Nanocavity integrated van der Waals heterostructure light-emitting tunneling diode. Nano Lett. 17, 200–205 (2017).

    Article  CAS  Google Scholar 

  21. Withers, F. et al. WSe2 light-emitting tunneling transistors with enhanced brightness at room temperature. Nano Lett. 15, 8223–8228 (2015).

    Article  CAS  Google Scholar 

  22. Jones, A. M. et al. Optical generation of excitonic valley coherence in monolayer WSe2. Nat. Nanotechnol. 8, 634–638 (2013).

    Article  CAS  Google Scholar 

  23. Huang, J. N., Hoang, T. B. & Mikkelsen, M. H. Probing the origin of excitonic states in monolayer WSe2. Sci. Rep. 6, 22414 (2016).

    Article  CAS  Google Scholar 

  24. Wang, G. et al. Valley dynamics probed through charged and neutral exciton emission in monolayer WSe2. Phys. Rev. B 90, 075413 (2014).

    Article  CAS  Google Scholar 

  25. Dey, P. et al. Gate-controlled spin–valley locking of resident carriers in WSe2 monolayers. Phys. Rev. Lett. 119, 137401 (2017).

    Article  CAS  Google Scholar 

  26. Liu, C. H., Zheng, J. J., Chen, Y. Y., Fryett, T. & Majumdar, A. Van der Waals materials integrated nanophotonic devices. Opt. Mater. Express 9, 384–399 (2019).

    Article  CAS  Google Scholar 

  27. Brar, V. W., Sherrott, M. C. & Jariwala, D. Emerging photonic architectures in two-dimensional opto-electronics. Chem. Soc. Rev. 47, 6824–6844 (2018).

    Article  CAS  Google Scholar 

  28. May, A. F. et al. Ferromagnetism near room temperature in the cleavable van der Waals crystal Fe5GeTe2. ACS Nano 13, 4436–4442 (2019).

    Article  CAS  Google Scholar 

  29. O’Hara, D. J. et al. Room temperature intrinsic ferromagnetism in epitaxial manganese selenide films in the monolayer limit. Nano Lett. 18, 3125–3131 (2018).

    Article  CAS  Google Scholar 

  30. Liu, S. et al. Room-temperature valley polarization in atomically thin semiconductors via chalcogenide alloying. ACS Nano 14, 9873–9883 (2020).

    Article  CAS  Google Scholar 

  31. Huang, P. et al. Recent advances in two-dimensional ferromagnetism: materials synthesis, physical properties and device applications. Nanoscale 12, 2309–2327 (2020).

    Article  CAS  Google Scholar 

  32. Roemer, R., Liu, C. & Zou, K. Robust ferromagnetism in wafer-scale monolayer and multilayer Fe3GeTe2. npj 2D Mater. Appl. 4, 33 (2020).

    Article  CAS  Google Scholar 

  33. Kang, K. et al. High-mobility three-atom-thick semiconducting films with wafer-scale homogeneity. Nature 520, 656–660 (2015).

    Article  CAS  Google Scholar 

  34. Yu, G. L. et al. Interaction phenomena in graphene seen through quantum capacitance. Proc. Natl Acad. Sci. USA 110, 3282–3286 (2013).

    Article  CAS  Google Scholar 

  35. McCreary, K. M., Currie, M., Hanbicki, A. T., Chuang, H. J. & Jonker, B. T. Understanding variations in circularly polarized photoluminescence in monolayer transition metal dichalcogenides. ACS Nano 11, 7988–7994 (2017).

    Article  CAS  Google Scholar 

  36. Liu, Y. et al. Van der Waals heterostructures and devices. Nat. Rev. Mater. 1, 16042 (2016).

    Article  CAS  Google Scholar 

  37. Katsuaki, S. Measurement of magneto-optical Kerr effect using piezo-birefringent modulator. Jpn J. Appl. Phys. 20, 2403 (1981).

    Article  Google Scholar 

  38. Wang, Z. et al. Electric-field control of magnetism in a few-layered van der Waals ferromagnetic semiconductor. Nat. Nanotechnol. 13, 554–559 (2018).

    Article  CAS  Google Scholar 

  39. Kresse, G. & Hafner, J. Ab-initio molecular-dynamics simulation of the liquid-metal amorphous–semiconductor transition in germanium. Phys. Rev. B 49, 14251–14269 (1994).

    Article  CAS  Google Scholar 

  40. Kresse, G. & Furthmuller, J. Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set. Phys. Rev. B 54, 11169–11186 (1996).

    Article  CAS  Google Scholar 

  41. Blöchl, P. E. Projector augmented-wave method. Phys. Rev. B 50, 17953–17979 (1994).

    Article  Google Scholar 

  42. Perdew, J. P., Burke, K. & Ernzerhof, M. Generalized gradient approximation made simple. Phys. Rev. Lett. 77, 3865–3868 (1996).

    Article  CAS  Google Scholar 

Download references

Acknowledgements

We thank K. L. Seyler for useful discussions and C.-B. Huang for sharing electronic instruments. C.-H.L. acknowledges support from the National Tsing Hua University (110QI039E1) and the Ministry of Science and Technology of Taiwan (107-2112-M-007-002-MY3, 109-2112-M-007-032-MY3). H.-T.J. acknowledges support from the Ministry of Science and Technology of Taiwan (109-2112-M-007-034-MY3). H.-T.J. also thanks NCHC, CINCNTU, AS-iMATE-109-13 and CQT-NTHU-MOE, Taiwan, for support.

Author information

Author notes

  1. These authors contributed equally: Jia-Xin Li, Wei-Qing Li, Sheng-Hsiung Hung.

Authors and Affiliations

  1. Institute of Photonics Technologies, National Tsing Hua University, Hsinchu, Taiwan

    Jia-Xin Li, Wei-Qing Li, Po-Liang Chen, Tian-Yun Chang & Chang-Hua Liu

  2. Department of Physics, National Tsing Hua University, Hsinchu, Taiwan

    Sheng-Hsiung Hung & Horng-Tay Jeng

  3. Department of Electrical Engineering, National Tsing Hua University, Hsinchu, Taiwan

    Yueh-Chiang Yang, Po-Wen Chiu & Chang-Hua Liu

  4. Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan

    Po-Wen Chiu

  5. Institute of Physics, Academia Sinica, Taipei, Taiwan

    Horng-Tay Jeng

  6. Physics Division, National Center for Theoretical Sciences, Hsinchu, Taiwan

    Horng-Tay Jeng

Authors
  1. Jia-Xin Li
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Wei-Qing Li
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Sheng-Hsiung Hung
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. Po-Liang Chen
    View author publications

    You can also search for this author in PubMed Google Scholar

  5. Yueh-Chiang Yang
    View author publications

    You can also search for this author in PubMed Google Scholar

  6. Tian-Yun Chang
    View author publications

    You can also search for this author in PubMed Google Scholar

  7. Po-Wen Chiu
    View author publications

    You can also search for this author in PubMed Google Scholar

  8. Horng-Tay Jeng
    View author publications

    You can also search for this author in PubMed Google Scholar

  9. Chang-Hua Liu
    View author publications

    You can also search for this author in PubMed Google Scholar

Contributions

C.-H.L. and H.-T.J. supervised the project. Y.-C.Y. synthesized CVD WSe2, assisted by P.-W.C. J.-X.L. and W.-Q.L. fabricated the vdW heterostructures, assisted by P.-L.C. C.-H.L. conceived the experiments. J.-X.L. and W.-Q.L. performed the measurements, assisted by T.-Y.C. and C.-H.L. S.-H.H. and H.-T.J. provided theoretical support. All authors contributed to the discussion of the data in the paper and Supplementary Information.

Corresponding authors

Correspondence to Horng-Tay Jeng or Chang-Hua Liu.

Ethics declarations

Competing interests

The authors declare no competing interests.

Peer review

Peer review information

Nature Nanotechnology thanks Zheng Han and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

Additional information

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary information

Supplementary Information

Supplementary Sections 1–11 and Figs. 1–13.

Source data

Source Data Fig. 1

Unprocessed data for Fig. 1.

Source Data Fig. 2

Unprocessed data for Fig. 2.

Source Data Fig. 3

Unprocessed data for Fig. 3.

Source Data Fig. 4

Unprocessed data for Fig. 4.

Source Data Fig. 5

Unprocessed data for Fig. 5.

Rights and permissions

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Li, JX., Li, WQ., Hung, SH. et al. Electric control of valley polarization in monolayer WSe2 using a van der Waals magnet. Nat. Nanotechnol. 17, 721–728 (2022). https://doi.org/10.1038/s41565-022-01115-2

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/s41565-022-01115-2

This article is cited by

Search

Advanced search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing