  We theoretically study the mechanical induction of the spin density via the
Rashba spin--orbit interaction (SOI). The spin density in the linear response
to lattice distortion dynamics is calculated based on the microscopic theory.
We reveal that there are two mechanisms of spin induction: one is the acoustic
Edelstein effect (AEE) from the acceleration of the lattice dynamics and the
other is caused by the Rashba spin--vorticity coupling (RSVC). We find that the
AEE induces a more efficient spin-to-charge conversion in comparison with the
conventional electric Edelstein effect. The induced spin density due to the
RSVC is expressed as a Berry curvature-like quantity; therefore, it can be
attributed to the spatial symmetry breaking due to the Rashba SOI. Our work
demonstrates high-efficiency spin generation in Rashba systems.
