Temperature dependence of charge-to-spin conversion in rhombohedral (110) bismuth thin film

Abstract

The amplitude of charge-to-spin conversion, namely the spin Hall effect (SHE), in bismuth (Bi) strongly depends on its crystal orientation. The conversion efficiency at room temperature in rhombohedral (110) bismuth is notably large as expected from its large spin-orbit interaction, and such a large SHE is ascribed to the large effective g-factor in bismuth [N. Fukumoto et al., Proc. Nat. Acad. Sci. 120, e2215030120 (2023)]. Despite the successful observation of the large conversion efficiency, a more detailed physical mechanism of the SHE in (110) bismuth is still elusive and under debate. In this work, we investigate the temperature dependence of charge-to-spin conversion in an epitaxial Bi(110)/Ni bilayer system using the second harmonic Hall method, revealing that both spin Hall conductivity and spin diffusion length augment with decreasing temperature. This finding suggests that spin scattering in (110) bismuth is dominated by the Elliott-Yafet mechanism, and the charge-to-spin conversion is mainly attributed to skew scattering.