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Spin–layer locking of interlayer excitons trapped in moiré potentials

Nature Materials volume 19, pages 630–636 (2020)Cite this article

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Abstract

Van der Waals heterostructures offer attractive opportunities to design quantum materials. For instance, transition metal dichalcogenides (TMDs) possess three quantum degrees of freedom: spin, valley index and layer index. Furthermore, twisted TMD heterobilayers can form moiré patterns that modulate the electronic band structure according to the atomic registry, leading to spatial confinement of interlayer excitons (IXs). Here we report the observation of spin–layer locking of IXs trapped in moiré potentials formed in a heterostructure of bilayer 2H-MoSe2 and monolayer WSe2. The phenomenon of locked electron spin and layer index leads to two quantum-confined IX species with distinct spin–layer–valley configurations. Furthermore, we observe that the atomic registries of the moiré trapping sites in the three layers are intrinsically locked together due to the 2H-type stacking characteristic of bilayer TMDs. These results identify the layer index as a useful degree of freedom to engineer tunable few-level quantum systems in two-dimensional heterostructures.

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Fig. 1: Spin–layer locking of moiré-trapped IXs in a van der Waals heterostructure.
Fig. 2: Optical spectroscopy properties of spin–layer-locked IXs trapped in moiré potentials.
Fig. 3: Magneto-optic properties of spin–layer-locked IXs trapped in moiré potentials.
Fig. 4: Optical selection rules of spin–layer-locked IXs trapped in moiré potentials.

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Data availability

Data described in this paper and presented in the Supplementary Information are available online at https://researchportal.hw.ac.uk/en/persons/brian-d-gerardot/datasets/.

References

  1. Geim, A. K. & Grigorieva, I. V. Van der Waals heterostructures. Nature 499, 419–425 (2013).

    Article  Google Scholar 

  2. Bistritzer, R. & MacDonald, A. H. Moiré bands in twisted double-layer graphene. Proc. Natl Acad. Sci. USA 108, 12233–12237 (2011).

    Article  CAS  Google Scholar 

  3. Zhang, C. et al. Interlayer couplings, Moiré patterns, and 2D electronic superlattices in MoS2/WSe2 hetero-bilayers. Sci. Adv. 3, e1601459 (2017).

    Article  Google Scholar 

  4. Cao, Y. et al. Unconventional superconductivity in magic-angle graphene superlattices. Nature 556, 43–50 (2018).

    Article  CAS  Google Scholar 

  5. Jin, C. et al. Observation of moiré excitons in WSe2/WS2 heterostructure superlattices. Nature 567, 76–80 (2019).

    Article  CAS  Google Scholar 

  6. Alexeev, E. M. et al. Resonantly hybridized excitons in moiré superlattices in van der Waals heterostructures. Nature 567, 81–86 (2019).

    Article  CAS  Google Scholar 

  7. Tong, Q. et al. Topological mosaics in moiré superlattices of van der Waals heterobilayers. Nat. Phys. 13, 356–362 (2017).

    Article  CAS  Google Scholar 

  8. Yankowitz, M. et al. Dynamic band-structure tuning of graphene moiré superlattices with pressure. Nature 557, 404–408 (2018).

    Article  CAS  Google Scholar 

  9. Yu, H., Liu, G.-B., Tang, J., Xu, X. & Yao, W. Moiré excitons: from programmable quantum emitter arrays to spin-orbit–coupled artificial lattices. Sci. Adv. 3, e1701696 (2017).

    Article  Google Scholar 

  10. Wu, F., Lovorn, T. & MacDonald, A. Theory of optical absorption by interlayer excitons in transition metal dichalcogenide heterobilayers. Phys. Rev. B 97, 035306 (2018).

    Article  CAS  Google Scholar 

  11. Yu, H., Liu, G.-B. & Yao, W. Brightened spin-triplet interlayer excitons and optical selection rules in van der Waals heterobilayers. 2D Mater. 5, 035021 (2018).

    Article  Google Scholar 

  12. Seyler, K. L. et al. Signatures of moiré-trapped valley excitons in MoSe2/WSe2 heterobilayers. Nature 567, 66–70 (2019).

    Article  CAS  Google Scholar 

  13. Tran, K. et al. Evidence for moiré excitons in van der Waals heterostructures. Nature 567, 71–75 (2019).

    Article  CAS  Google Scholar 

  14. Xu, X., 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 

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

    Article  Google Scholar 

  16. Mak, K. F., He, K., 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 

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

    Article  CAS  Google Scholar 

  18. Aivazian, G. et al. Magnetic control of valley pseudospin in monolayer WSe2. Nat. Phys. 11, 148–152 (2015).

    Article  CAS  Google Scholar 

  19. Srivastava, A. et al. Valley Zeeman effect in elementary optical excitations of monolayer WSe2. Nat. Phys. 11, 141–147 (2015).

    Article  CAS  Google Scholar 

  20. Gong, Z. et al. Magnetoelectric effects and valley-controlled spin quantum gates in transition metal dichalcogenide bilayers. Nat. Commun. 4, 2053 (2013).

    Article  Google Scholar 

  21. Jones, A. M. et al. Spin–layer locking effects in optical orientation of exciton spin in bilayer WSe2. Nat. Phys. 10, 130–134 (2014).

    Article  CAS  Google Scholar 

  22. Riley, J. M. et al. Direct observation of spin-polarized bulk bands in an inversion-symmetric semiconductor. Nat. Phys. 10, 835–839 (2014).

    Article  CAS  Google Scholar 

  23. Chiu, M.-H. et al. Determination of band alignment in the single-layer MoS2/WSe2 heterojunction. Nat. Commun. 6, 7666 (2015).

    Article  CAS  Google Scholar 

  24. Wilson, N. R. et al. Determination of band offsets, hybridization, and exciton binding in 2D semiconductor heterostructures. Sci. Adv. 3, e1601832 (2017).

    Article  Google Scholar 

  25. Hong, X. et al. Ultrafast charge transfer in atomically thin MoS2/WS2 heterostructures. Nat. Nanotechnol. 9, 682–686 (2014).

    Article  CAS  Google Scholar 

  26. Yu, H., Wang, Y., Tong, Q., Xu, X. & Yao, W. Anomalous light cones and valley optical selection rules of interlayer excitons in twisted heterobilayers. Phys. Rev. Lett. 115, 187002 (2015).

    Article  Google Scholar 

  27. Rivera, P. et al. Observation of long-lived interlayer excitons in monolayer MoSe2–WSe2 heterostructures. Nat. Commun. 6, 6242 (2015).

    Article  CAS  Google Scholar 

  28. Rivera, P. et al. Valley-polarized exciton dynamics in a 2D semiconductor heterostructure. Science 351, 688–691 (2016).

    Article  CAS  Google Scholar 

  29. Hanbicki, A. T. et al. Double indirect interlayer exciton in a MoSe2/WSe2 van der Waals heterostructure. ACS Nano 12, 4719–4726 (2018).

    Article  CAS  Google Scholar 

  30. Ciarrocchi, A. et al. Polarization switching and electrical control of interlayer excitons in two-dimensional van der Waals heterostructures. Nat. Photon. 13, 131–136 (2019).

    Article  CAS  Google Scholar 

  31. Torun, E., Miranda, H. P. C., Molina-Sánchez, A. & Wirtz, L. Interlayer and intralayer excitons in MoS2/WS2 and MoSe2/WSe2 heterobilayers. Phys. Rev. B 97, 245427 (2018).

    Article  CAS  Google Scholar 

  32. Jiang, C. et al. Microsecond dark-exciton valley polarization memory in two-dimensional heterostructures. Nat. Commun. 9, 753 (2018).

    Article  Google Scholar 

  33. Srivastava, A. et al. Optically active quantum dots in monolayer WSe2. Nat. Nanotechnol. 10, 491–496 (2015).

    Article  CAS  Google Scholar 

  34. Tonndorf, P. et al. Single-photon emission from localized excitons in an atomically thin semiconductor. Optica 2, 347–352 (2015).

    Article  CAS  Google Scholar 

  35. Brotons-Gisbert, M. et al. Coulomb blockade in an atomically thin quantum dot coupled to a tunable Fermi reservoir. Nat. Nanotechnol. 14, 442–446 (2019).

    Article  CAS  Google Scholar 

  36. Nagler, P. et al. Giant magnetic splitting inducing near-unity valley polarization in van der Waals heterostructures. Nat. Commun. 8, 1551 (2017).

    Article  Google Scholar 

  37. Yao, W., Xiao, D. & Niu, Q. Valley-dependent optoelectronics from inversion symmetry breaking. Phys. Rev. B 77, 235406 (2008).

    Article  Google Scholar 

  38. Kormányos, A. et al. k · p theory for two-dimensional transition metal dichalcogenide semiconductors. 2D Mater. 2, 022001 (2015).

    Article  Google Scholar 

  39. Larentis, S. et al. Large effective mass and interaction-enhanced Zeeman splitting of K-valley electrons in MoSe2. Phys. Rev. B 97, 201407 (2018).

    Article  CAS  Google Scholar 

  40. Goryca, M. et al. Revealing exciton masses and dielectric properties of monolayer semiconductors with high magnetic fields. Nat. Commun. 10, 4172 (2019).

    Article  CAS  Google Scholar 

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Acknowledgements

We thank J. J. Finley, K. Müller, M. Kremser and A. Högele for discussions. This work is supported by the EPSRC (grant no. EP/P029892/1 and EP/S000550/1), the ERC (grant no. 725920) and the EU Horizon 2020 research and innovation programme under grant agreement no. 820423. A.M.-S. acknowledges the Juan de la Cierva programme (grant IJCI-2015-25799; MINECO, Spain) and the Marie-Curie-COFUND programme Nano TRAIN For Growth II (grant agreement 713640). The computations were performed on the Tirant III cluster of the Servei d’Informàtica of the University of Valencia (project vlc82). Growth of hBN crystals by K.W. and T.T. was supported by the Elemental Strategy Initiative conducted by the MEXT, Japan and the CREST (JPMJCR15F3). B.D.G. is supported by a Wolfson Merit Award from the Royal Society and a Chair in Emerging Technology from the Royal Academy of Engineering.

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Author notes

  1. These authors contributed equally: Mauro Brotons-Gisbert, Hyeonjun Baek.

Authors and Affiliations

  1. Institute of Photonics and Quantum Sciences, SUPA, Heriot-Watt University, Edinburgh, UK

    Mauro Brotons-Gisbert, Hyeonjun Baek, Aidan Campbell, Eleanor Scerri, Daniel White, Cristian Bonato & Brian D. Gerardot

  2. Institute of Materials Science (ICMUV), University of Valencia, Valencia, Spain

    Alejandro Molina-Sánchez

  3. International Iberian Nanotechnology Laboratory (INL), Braga, Portugal

    Alejandro Molina-Sánchez

  4. National Institute for Materials Science, Tsukuba, Japan

    Kenji Watanabe & Takashi Taniguchi

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  1. Mauro Brotons-Gisbert
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Contributions

B.D.G. conceived and supervised the project. H.B. fabricated the samples. K.W. and T.T. supplied the hBN crystals. M.B.-G. and H.B. performed the experiments, assisted by A.C., C.B. and D.W.; M.B.-G. analysed the data, assisted by E.S. and B.D.G.; A.M.-S. performed the ab initio calculations. M.B.-G. and B.D.G. cowrote the paper with input from all authors. M.B.-G. and H.B. contributed equally to this work.

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Correspondence to Mauro Brotons-Gisbert, Hyeonjun Baek or Brian D. Gerardot.

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Supplementary Notes 1-8 and Figs. 1-10.

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Brotons-Gisbert, M., Baek, H., Molina-Sánchez, A. et al. Spin–layer locking of interlayer excitons trapped in moiré potentials. Nat. Mater. 19, 630–636 (2020). https://doi.org/10.1038/s41563-020-0687-7

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