Valley filter and giant magnetoresistance in zigzag α-T₃ nanoribbons

Due to opposite Berry phases for two valleys in the α-T₃ model, the quasiparticles in two valleys have different responses to a perpendicular magnetic field, such as different Landau levels in a strong magnetic field. In this work, we theoretically demonstrate the manipulation of the valley degree of freedom in the α-T₃ model via an external magnetic field. In zigzag α-T₃ nanoribbons with moderate α, we show that a weak magnetic field lifts the valley degeneracy of the spectrum and the ribbon acts as a valley filter. Furthermore, we propose a valley-valve which contains two successive magnetic sections. The valve exhibits a giant magnetoresistance and the on–off ratio reaches up to 10⁶. These findings should be useful to potential valleytronic applications and magnetic read heads based on α-T₃ materials. (paper)