  Manipulating the valley degree of freedom to encode information for potential
valleytronic devices has ignited a new direction in solid-state physics. A
significant, fundamental challenge in the field of valleytronics is how to
generate and regulate valley-polarized currents by practical ways. Here, we
discover a new mechanism of producing valley polarization in a monolayer
transition metal dichalcogenides superlattice, in which valley-resolved gaps
are formed at the supercell Brillouin zone boundaries and centers due to the
intervalley scattering. When the energy of the incident electron is in the
gaps, the available states are valley polarized, thus providing a
valley-polarized current from the superlattice. We show that the direction and
strength of the valley polarization may further be tuned by varying the
potential applied the superlattice. The transmission can have a net valley
polarization of 55% for a 4-period heterojunction. Moreover, such two valley
filters in series may function as an electrostatically controlled giant
valleyresistance device, representing a zero magnetic field counterpart to the
familiar giant magnetoresistance device.
