▎ 摘　　要

We explore valley filtering in a two-terminal graphene system with a Dirac gap. For such a system with a constant Dirac gap, it is found that the presence of a valley-polarized output current requires both a magnetic barrier and an electric potential. For the magnetic-electric barrier generated by a single ferromagnetic stripe, a remarkable valley polarization can be achieved and is tunable by gate voltages. The generated valley polarization can be detected from the Hall measurement in the outgoing region [Phys. Rev. Lett. 99, 236809 (2007)].