Spin Hall effect in a spin-1 chiral semimetal

The spin-1 chiral semimetal is a state of quantum matter hosting unconventional fermions that extend beyond the common Dirac and Weyl fermions. B20-type CoSi prototypal material accommodates such an exotic quasiparticle. To date, spin-transport properties in semimetals have not been thoroughly explored. In this work, we fabricated B20-CoSi thin films on sapphire $c$-plane substrates by magnetron sputtering studied spin Hall effect (SHE) combining experiments first-principles calculations. SHE was investigated using CoSi/CoFeB/MgO heterostructures via magnetoresistance harmonic measurements. First-principles calculations yield intrinsic conductivity (SHC) at Fermi level consistent with reveal its unique Fermi-energy dependence. Unlike fermion-mediated conductivities exhibit peaklike structure centering around topological node, SHC odd crosses zero node two antisymmetric local extrema opposite sign situated below above energy. Hybridization between Co $d$-Si $p$ orbitals spin-orbit coupling are essential for SHC, despite small (\ensuremath{\sim}1%) weight Si orbital near level. This work expands horizon spintronics highlights importance Fermi-level tuning order to fully exploit topology spin-current generation.