  Twisted van der Waals bilayers offer ideal two-dimensional (2D) platforms for
exploring the intricate interplay between the spin and charge degrees of
freedom of electrons. By investigating twisted MoS2 bilayer, featuring two
distinct stackings but with identical commensurate supercell sizes, we reveal
an unusual dielectric response behavior inherent to this system. Our
first-principles calculations demonstrate that the application of an
out-of-plane electric field gives different responses in electronic
polarization. Upon further analysis, it becomes apparent that this dielectric
response comes from the planar charge redistribution associated with spin-orbit
coupling (SOC) effect. The underlying mechanism lies in the fact that the
external electric field tends to modify the internal pseudo-spin texture
\sigma, subsequently generating an out-of-plane (pseudo-) spin current j_s
\propto \sigma \times B_R as response to an in-plane pseudomagnetic field B_R
through Rashba SOC. It is found that the generated j_s is opposite for the two
distinct stackings, resulting in opposite in-plane electric susceptibility. As
a consequence, through magnetoelectric coupling within such nonmagnetic system,
there give rise to opposite tendency to redistribute charge, ultimately leading
to an amplified or suppressed dielectric response.
