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Highly anisotropic spin transport in ultrathin black phosphorus

Nature Materials volume 23, pages 479–485 (2024)Cite this article

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Abstract

In anisotropic crystals, the direction-dependent effective mass of carriers can have a profound impact on spin transport dynamics. The puckered crystal structure of black phosphorus leads to direction-dependent charge transport and optical response, suggesting that it is an ideal system for studying anisotropic spin transport. To this end, we fabricate and characterize high-mobility encapsulated ultrathin black-phosphorus-based spin valves in a four-terminal geometry. Our measurements show that in-plane spin lifetimes are strongly gate tunable and exceed one nanosecond. Through high out-of-plane magnetic fields, we observe a fivefold enhancement in the out-of-plane spin signal case compared to in-plane and estimate a colossal spin-lifetime anisotropy of ∼6. This finding is further confirmed by oblique Hanle measurements. Additionally, we estimate an in-plane spin-lifetime anisotropy ratio of up to 1.8. Our observation of strongly anisotropic spin transport along three orthogonal axes in this pristine material could be exploited to realize directionally tunable spin transport.

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Fig. 1: Device fabrication and charge transport characterization.
Fig. 2: Nanosecond spin lifetimes and gate-dependent spin transport.
Fig. 3: Anisotropic spin relaxation.
Fig. 4: Indication of spin dephasing near zero in-plane field.

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Data availability

The datasets generated and/or analysed during this study are available from the corresponding authors upon reasonable request.

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Acknowledgements

We acknowledge helpful discussions with J. Fabian and A. Ciarrocchi. A.A. acknowledges support by the National Research Foundation, Prime Minister’s Office, Singapore (NRFF14-2022-0083). B.Ö. acknowledges support by the National Research Foundation, Prime Minister’s Office, Singapore, under its Competitive Research Program (CRP award no. NRF-CRP22-2019-8), National Research Foundation Investigatorship (NRFI award no. NRF-NRFI2018-08), MOE-AcRF-Tier 2 (grant no. MOE-T2EP50220-0017), Ministry of Education, Singapore, under its Research Centre of Excellence award to the Institute for Functional Intelligent Materials (Project No. EDUNC-33-18-279-V12) and the Medium-Sized Centre Programme. K.W. and T.T. acknowledge support from the Elemental Strategy Initiative conducted by the MEXT, Japan, and the JSPS KAKENHI (grant nos 21H05233 and 23H02052).

Author information

Authors and Affiliations

  1. School of Mathematics, Statistics and Physics, Newcastle University, Newcastle upon Tyne, United Kingdom

    Luke Cording & Ahmet Avsar

  2. Centre for Advanced 2D Materials, National University of Singapore, Singapore, Singapore

    Jiawei Liu, Jun You Tan, Ahmet Avsar & Barbaros Özyilmaz

  3. Research Center for Functional Materials, National Institute for Materials Science, Tsukuba, Japan

    Kenji Watanabe

  4. International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Japan

    Takashi Taniguchi

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

    Ahmet Avsar & Barbaros Özyilmaz

  6. Department of Materials Science and Engineering, National University of Singapore, Singapore, Singapore

    Ahmet Avsar & Barbaros Özyilmaz

  7. Institute for Functional Intelligent Materials, National University of Singapore, Singapore, Singapore

    Barbaros Özyilmaz

Authors
  1. Luke Cording
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  2. Jiawei Liu
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  3. Jun You Tan
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  6. Ahmet Avsar
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Contributions

A.A. and B.Ö. designed and coordinated the work. A.A. and J.Y.T. fabricated the samples. A.A. and J.L. performed transport measurements. L.C. and A.A. performed simulations. K.W. and T.T. grew the hBN and BP crystals. L.C., A.A. and B.Ö. analysed the results and wrote the paper with input from all authors.

Corresponding authors

Correspondence to Ahmet Avsar or Barbaros Özyilmaz.

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Nature Materials thanks Juan-Carlos Rojas-Sánchez and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary Figs. 1–6.

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Cording, L., Liu, J., Tan, J.Y. et al. Highly anisotropic spin transport in ultrathin black phosphorus. Nat. Mater. 23, 479–485 (2024). https://doi.org/10.1038/s41563-023-01779-8

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