  We describe an angularly asymmetric interface-scattering mechanism which
allows to spatially separate the electrons in the two low-energy valleys of
bilayer graphene. The effect occurs at electrostatically defined interfaces
separating regions of different pseudospin polarization, and is associated with
the helical winding of the pseudospin vector across the interface, which breaks
the reflection symmetry in each valley. Electrons are transmitted with a
preferred direction of up to 60 degree over a large energetic range in one of
the valleys, and down to -60 degree in the other. In a Y-junction geometry,
this can be used to create and detect valley polarization.
