Colossal Spin Hall Conductivity in Charge-Massive Topologically Nontrivial Semimetal Phase of Bi<sub>1-<i>x</i></sub>Sb<sub><i>x</i></sub> (012).
basic_science · Level V
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- Record sourced from PubMed, PMID 41143713.
- Also identified by DOI 10.1021/acsnano.5c14715 and PMC identifier 12614200.
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Abstract
Topologically nontrivial semimetals (TSMs) possess spin-momentum locked topological surface states (TSS) with high charge conductivity (σ), offering a platform for low-power spintronic applications. However, its spin Hall conductivity (σ<sub>SH</sub>), another important factor for spintronic applications, remains largely unexplored. Here, we demonstrate that Bi<sub>1-<i>x</i></sub>Sb<sub><i>x</i></sub> in the TSM phase (<i>x</i> = 0.6-0.8), when grown along the distinct (012) orientation, exhibits a colossal σ<sub>SH</sub>, far exceeding that of Pt. The σ of Bi<sub>1-<i>x</i></sub>Sb<sub><i>x</i></sub> (012) in the TSM phase is also 1 to 2 orders of magnitude higher than that of conventional topological materials. We reveal a crystal orientation-selective activation of TSS in charge-to-spin conversion (CSC) of Bi<sub>1-<i>x</i></sub>Sb<sub><i>x</i></sub> (012), in contrast to Bi<sub>1-<i>x</i></sub>Sb<sub><i>x</i></sub> (001), where CSC is bulk-dominated. Our density functional theory calculations reveal multiple Dirac cones on the (012) surface, providing a compelling explanation for the observed colossal σ<sub>SH</sub> via a two-channel model that incorporates both bulk and surface contributions. Our findings suggest TSMs, particularly Bi<sub>1-<i>x</i></sub>Sb<sub><i>x</i></sub> (012), as an effective material system for next-generation low-power spintronic devices.