  The band structure of a monolayer MoS$_2$ comprises of spin-split subbands,
owing to the mutual presence of broken inversion symmetry and strong spin-orbit
coupling. In the conduction band, spin-valley coupled subbands cross each other
at finite momenta, and they are valley-degenerate. When exposed to surface
acoustic waves, the emerging strain-induced effective magnetic field can give
rise to spin-flip transitions between the spin-split subbands in the vicinity
of subbands crossing point, resulting in the emergence of a spin-acoustic
resonance and the acoustoelectric current. An external magnetic field breaks
the valley degeneracy resulting in the valley-selective splitting of
spin-acoustic resonances both in surface acoustic wave absorption and
acoustoelectric current.
