  We theoretically propose a novel spin-dependent electronic transport
mechanism in which the spin-unpolarized electron beam is split into different
directions depending on spins at an atomic domain boundary in non-magnetic
material. Specifically, we calculate the electronic transmission across a
boundary between monolayer and bilayer of the transition metal dichalcogenide,
and demonstrate that up-spin and down-spin electrons entering the boundary are
refracted and collimated to opposite directions. The phenomenon is attributed
to the strong spin-orbit interaction, the trigonally-warped Fermi surface, and
the different crystal symmetries between the monolayer and bilayer systems. The
spin-dependent refraction suggests a potential application for a spin splitter,
which spatially separates up-spin and down-spin electrons simply by passing the
electric current through the boundary.
