We report on the observation of the acoustic spin Hall effect that facilitates lattice motion–induced spin current via spin-orbit interaction (SOI). Under excitation of surface acoustic wave (SAW), we find that a spin current flows orthogonal to the SAW propagation in nonmagnetic metals (NMs). The acoustic spin Hall effect manifests itself in a field-dependent acoustic voltage in NM/ferromagnetic metal bilayers. The acoustic voltage takes a maximum when the NM layer thickness is close to its spin diffusion length, vanishes for NM layers with weak SOI, and increases linearly with the SAW frequency. To account for these results, we find that the spin current must scale with the SOI and the time derivative of the lattice displacement. These results, which imply the strong coupling of electron spins with rotating lattices via the SOI, show the potential of lattice dynamics to supply spin current in strong spin-orbit metals.

No abstract

Generation of spin current from lattice distortion dynamics in metals is studied with special attention on the effect of spin-orbit coupling. Treating the lattice distortion by local coordinate transformation, we calculate spin current and spin accumulation with the linear response theory. It is found that there are two routes to the spin-current generation: one via the spin Hall effect and the other via the spin accumulation. The present effect due to spin-orbit coupling can be comparable to, or even larger than, the one based on the spin-vorticity coupling in systems with strong spin-orbit coupling.

No abstract