Coexistence of large conventional and planar spin Hall effect with long spin diffusion length in a low-symmetry semimetal at room temperature

Abstract

The spin Hall effect (SHE) is usually observed as a bulk effect in high-symmetry crystals with substantial spin–orbit coupling (SOC), where the symmetric spin–orbit field imposes a widely encountered trade-off between spin Hall angle (θSH) and spin diffusion length (Lsf), and spin polarization, spin current and charge current are constrained to be mutually orthogonal. Here, we report a large θSH of 0.32 accompanied by a long Lsf of 2.2 μm at room temperature in a low-symmetry few-layered semimetal MoTe2, thus identifying it as an excellent candidate for simultaneous spin generation, transport and detection. In addition, we report that longitudinal spin current with out-of-plane polarization can be generated by both transverse and vertical charge current, due to the conventional and a newly observed planar SHE, respectively. Our study suggests that manipulation of crystalline symmetries and strong SOC opens access to new charge-spin interconversion configurations and spin–orbit torques for spintronic applications.

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Fig. 1: Crystal symmetry of bulk and few-layered MoTe2.
Fig. 2: Conventional SHE in MoTe2.
Fig. 3: Charge-induced out-of-plane spin current.
Fig. 4: Planar SHE and performance benchmark.
Fig. 5: DFT calculations of the SHE of MoTe2.

Data availability

The datasets generated by the present study are available from the corresponding author on request.

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Acknowledgements

We acknowledge S. Roche for insightful discussions. K.P.L. acknowledges the AME-IRG grant ‘Scalable Growth of Ultrathin Ferroelectric Materials for Memory Technologies’, no. A1938c0035, funded by the Agency for Science, Technology and Research, Singapore. P.S. thanks B. Özyilmaz for providing molecular-beam epitaxy slots and H. Chen for assistance in electron-beam lithography.

Author information

P.S. and K.P.L. conceived the project, P.S. performed device fabrication and electric measurements with help from Y.D. and Y.Z. C.H.H., H.L., V.M.P. and G.V. performed DFT calculations and theoretical modelling. M.Z. performed Raman measurements and exfoliation of h-BN, J.L. performed MBE deposition of Co, W.F. drew part of the schematics and Y.L. helped with figure processing. P.S., C.H.H., V.M.P. and K.P.L. wrote the manuscript with input from all authors.

Correspondence to Hsin Lin or Vitor M. Pereira or Kian Ping Loh.

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Supplementary Information

Supplementary Discussion, Figs. 1–15 and Table 1.

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Song, P., Hsu, C., Vignale, G. et al. Coexistence of large conventional and planar spin Hall effect with long spin diffusion length in a low-symmetry semimetal at room temperature. Nat. Mater. (2020). https://doi.org/10.1038/s41563-019-0600-4

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