Two-dimensional materials offer new opportunities for both fundamental science and technological applications, by exploiting the electron’s spin. Although graphene is very promising for spin communication due to its extraordinary electron mobility, the lack of a bandgap restricts its prospects for semiconducting spin devices such as spin diodes and bipolar spin transistors. The recent emergence of two-dimensional semiconductors could help overcome this basic challenge. In this letter we report an important step towards making two-dimensional semiconductor spin devices. We have fabricated a spin valve based on ultrathin (∼5 nm) semiconducting black phosphorus (bP), and established fundamental spin properties of this spin channel material, which supports all electrical spin injection, transport, precession and detection up to room temperature. In the non-local spin valve geometry we measure Hanle spin precession and observe spin relaxation times as high as 4 ns, with spin relaxation lengths exceeding 6 μm. Our experimental results are in a very good agreement with first-principles calculations and demonstrate that the Elliott–Yafet spin relaxation mechanism is dominant. We also show that spin transport in ultrathin bP depends strongly on the charge carrier concentration, and can be manipulated by the electric field effect.
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We thank S. Natarajan and Y. Yeo for their help. B.Ö. would like to acknowledge support by the National Research Foundation, Prime Minister’s Office, Singapore, under its Medium Sized Centre Programme and CRP award ‘Novel 2D materials with tailored properties: beyond graphene’ (Grant number R-144-000-295-281) and Competitive Research Programme (CRP Award No. NRF-CRP9-2011-3). M.K. acknowledges support from the DFG SPP 1538 and National Science Centre (NCN) grant DEC-2013/11/B/ST3/00824. M.G. and J.F. acknowledge support from DFG SFB 689 and GRK 1570. J.F. acknowledges support by the European Union’s Horizon 2020 research and innovation programme under Grant agreement No. 696656. K.W. and T.T. acknowledge support from the Elemental Strategy Initiative conducted by the MEXT, Japan and JSPS KAKENHI Grant Numbers JP26248061, JP15K21722 and JP25106006.
The authors declare no competing financial interests.
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Avsar, A., Tan, J., Kurpas, M. et al. Gate-tunable black phosphorus spin valve with nanosecond spin lifetimes. Nature Phys 13, 888–893 (2017) doi:10.1038/nphys4141
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