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Colossal enhancement of spin–orbit coupling in weakly hydrogenated graphene

Nature Physics volume 9, pages 284–287 (2013)Cite this article

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Abstract

Graphene’s extremely small intrinsic spin–orbit (SO) interaction1 makes the realization of many interesting phenomena such as topological/quantum spin Hall states2,3 and the spin Hall effect4 (SHE) practically impossible. Recently, it was predicted1,5,6,7 that the introduction of adatoms in graphene would enhance the SO interaction by the conversion of sp2 to sp3 bonds. However, introducing adatoms and yet keeping graphene metallic, that is, without creating electronic (Anderson) localization8, is experimentally challenging. Here, we show that the controlled addition of small amounts of covalently bonded hydrogen atoms is sufficient to induce a colossal enhancement of the SO interaction by three orders of magnitude. This results in a SHE at zero external magnetic fields at room temperature, with non-local spin signals up to 100 Ω; orders of magnitude larger than in metals9. The non-local SHE is, further, directly confirmed by Larmor spin-precession measurements. From this and the length dependence of the non-local signal we extract a spin relaxation length of ∼1 μm, a spin relaxation time of ∼ 90 ps and a SO strength of 2.5 meV.

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Figure 1: Device characterization.
Figure 2: Room-temperature measurements of non-local signal.
Figure 3: Magnetic field dependence of RNL.
Figure 4: Length and width dependence of RNL at room temperature.

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Acknowledgements

We thank A. Avsar, A. Pachoud, J. You and M. A. Cazalilla for their help and useful discussions. This work was supported by the Singapore National Research Foundation Fellowship award (RF2008-07-R-144-000-245-281), the NRF-CRP award ‘Novel 2D materials with tailored properties: beyond graphene’ (R-144-000-295-281) and the Singapore Millennium Foundation-NUS Research Horizons award (R-144-001-271-592; R-144-001-271-646).

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Author notes

  1. Manu Jaiswal

    Present address: Present address: Department of Physics, Indian Institute of Technology Madras, Chennai 600036, India,

  2. Jayakumar Balakrishnan and Gavin Kok Wai Koon: These authors contributed equally to this work

Authors and Affiliations

  1. Department of Physics, 2 Science Drive 3, National University of Singapore, Singapore 117542, Singapore

    Jayakumar Balakrishnan, Gavin Kok Wai Koon, Manu Jaiswal, A. H. Castro Neto & Barbaros Özyilmaz

  2. Graphene Research Centre, 6 Science Drive 2, National University of Singapore, Singapore 117546, Singapore

    Jayakumar Balakrishnan, Gavin Kok Wai Koon, Manu Jaiswal, A. H. Castro Neto & Barbaros Özyilmaz

  3. Nanocore, 4 Engineering Drive 3, National University of Singapore, Singapore 117576, Singapore

    Gavin Kok Wai Koon & Barbaros Özyilmaz

  4. NUS Graduate School for Integrative Sciences and Engineering (NGS), Centre for Life Sciences (CeLS), 28 Medical Drive, Singapore 117456, Singapore

    A. H. Castro Neto & Barbaros Özyilmaz

Authors
  1. Jayakumar Balakrishnan
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  2. Gavin Kok Wai Koon
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  3. Manu Jaiswal
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  4. A. H. Castro Neto
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Contributions

B.Ö. devised and supervised the project. J.B. and B.Ö. designed the experiments. J.B. and G.K.W.K. performed the experiments. A.H.C.N. provided the theoretical work. All authors carried out the data analysis and discussed the results. J.B., A.H.C.N. and B.Ö. co-wrote the paper.

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Correspondence to Barbaros Özyilmaz.

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Balakrishnan, J., Kok Wai Koon, G., Jaiswal, M. et al. Colossal enhancement of spin–orbit coupling in weakly hydrogenated graphene. Nature Phys 9, 284–287 (2013). https://doi.org/10.1038/nphys2576

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