▎ 摘　　要

We study the effects of inversion asymmetry and tunable band gap on the transmission of particles in bilayer graphene junctions to propose a model for a valley-filter and valley-valve device. The device is made up of a series of two n-p-n (or p-n-p) junctions produced by electric gate potentials: one of them, being applied by an out-of-layer magnetic field, functions as a valley filter and the other as a valley valve. The valley filtering is based on the valley-dependent Zeeman interaction between the applied magnetic field and the orbital magnetic moment that can exist in a system with broken inversion symmetry. The valley valve is performed by varying the size of band gap via the gate potential that controls the flow of valley-polarized particles. We demonstrate that the device can achieve nearly perfect valley polarization and very high efficiency of valley-valve effect. By fixing magnetic field, the device can be operated by electric gate potentials only, and the tunable band gap makes a continuous control of valley-separate switching on and off possible.