Strong Intrinsic Spin Hall Effect in the TaAs Family of Weyl Semimetals

Since their discovery, topological insulators have been expected to be ideal\nspintronic materials owing to the spin currents carried by surface states with\nspin--momentum locking. However, the bulk doping problem remains an obstacle\nthat hinders such application. In this work, we predict that a newly discovered\nfamily of topological materials, the Weyl semimetals, exhibits large intrinsic\nspin Hall effects that can be utilized to generate and detect spin currents.\nOur $ab~initio$ calculations reveal a large spin Hall conductivity that is\ncomparable to that of $4d$ and $5d$ transition metals. The spin Hall effect\noriginates intrinsically from the bulk band structure of Weyl semimetals, which\nexhibit a large Berry curvature and spin--orbit coupling, so the bulk carrier\nproblem in the topological insulators is naturally avoided. Our work not only\npaves the way for employing Weyl semimetals in spintronics, but also proposes a\nnew guideline for searching for the spin Hall effect in various topological\nmaterials.\n