The spin Hall effect of Bi-Sb alloys driven by thermally excited Dirac-like electrons.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 32181344.
- Also identified by DOI 10.1126/sciadv.aay2324 and PMC identifier 7060068.
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Abstract
We have studied the charge to spin conversion in Bi<sub>1-<i>x</i></sub> Sb <i><sub>x</sub></i> /CoFeB heterostructures. The spin Hall conductivity (SHC) of the sputter-deposited heterostructures exhibits a high plateau at Bi-rich compositions, corresponding to the topological insulator phase, followed by a decrease of SHC for Sb-richer alloys, in agreement with the calculated intrinsic spin Hall effect of Bi<sub>1-<i>x</i></sub> Sb <i><sub>x</sub></i> . The SHC increases with increasing Bi<sub>1-<i>x</i></sub> Sb <i><sub>x</sub></i> thickness before it saturates, indicating that it is the bulk of the alloy that predominantly contributes to the generation of spin current; the topological surface states, if present, play little role. Unexpectedly, the SHC is found to increase with increasing temperature, following the trend of carrier density. These results suggest that the large SHC at room temperature, with a spin Hall efficiency exceeding 1 and an extremely large spin current mobility, is due to increased number of thermally excited Dirac-like electrons in the <i>L</i> valley of the narrow gap Bi<sub>1-<i>x</i></sub> Sb <i><sub>x</sub></i> alloy.