Abstract

Spatially tailored pseudo-magnetic fields (PMFs) can give rise to pseudo-Landau levels and the valley Hall effect in graphene. At an experimental level, it is highly challenging to create the specific strain texture that can generate PMFs over large areas. Here, we report that superposing graphene on multilayer black phosphorus creates shear-strained superlattices that generate a PMF over an entire graphene–black phosphorus heterostructure with edge size of tens of micrometres. The PMF is intertwined with the spatial period of the moiré pattern, and its spatial distribution and intensity can be modified by changing the relative orientation of the two materials. We show that the emerging pseudo-Landau levels influence the transport properties of graphene–black phosphorus field-effect transistor devices with Hall bar geometry. The application of an external magnetic field allows us to enhance or reduce the effective field depending on the valley polarization with the prospect of developing a valley filter.

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Acknowledgements

The authors thank L. Xin and Q. Su Ying for valuable suggestions. K.P.L. and S.A. acknowledge support from the Singapore Ministry of Education AcRF Tier 2 (MOE2017-T2-2-140).

Author information

Affiliations

  1. Department of Chemistry, National University of Singapore, Singapore, Singapore

    • Yanpeng Liu
    • , Linjun Li
    • , Yang Bao
    • , Hai Xu
    • , Jiong Lu
    •  & Kian Ping Loh
  2. Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, Singapore, Singapore

    • Yanpeng Liu
    • , J. N. B. Rodrigues
    • , Linjun Li
    • , Alexandra Carvalho
    • , Ming Yang
    • , Evan Laksono
    • , Junpeng Lu
    • , Yang Bao
    • , Hai Xu
    • , Chorng Haur Sow
    • , Yuan Ping Feng
    • , A. H. Castro Neto
    • , Shaffique Adam
    • , Jiong Lu
    •  & Kian Ping Loh
  3. Department of Physics, National University of Singapore, Singapore, Singapore

    • J. N. B. Rodrigues
    • , Yong Zheng Luo
    • , Alexandra Carvalho
    • , Ming Yang
    • , Evan Laksono
    • , Junpeng Lu
    • , Chorng Haur Sow
    • , Yuan Ping Feng
    • , A. H. Castro Neto
    •  & Shaffique Adam
  4. Institute of Materials Research and Engineering, Agency for Science, Technology and Research, Singapore, Singapore

    • Ming Yang
  5. NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, Singapore, Singapore

    • Sherman J. R. Tan
    •  & Zhizhan Qiu
  6. Yale-NUS College, Singapore, Singapore

    • Shaffique Adam

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Contributions

K.P.L. supervised the project. Y.L., K.P.L. and J.L. designed and performed the experiments. J.N.B.R., Y.Z.L. and E.L. performed calculations under the supervision of S.A. and Y.P.F. Y.L. and L.L. fabricated and measured the G–BP FET device. A.C. and M.Y. carried out DFT calculations under the supervision of A.H.C.N. and Y.P.F. J.L. helped to collect and analyse angle-resolved Raman experimental data under the supervision of C.H.S. H.X. Y.B. and Z.Q. helped to collect and analyse STM data. S.J.R.T. provided support for XPS and ARPES experiments. Y.L. and K.P.L. co-wrote the manuscript. All authors discussed the results and commented on the manuscript.

Competing interests

The authors declare no competing interests.

Corresponding authors

Correspondence to Shaffique Adam or Jiong Lu or Kian Ping Loh.

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DOI

https://doi.org/10.1038/s41565-018-0178-z