Antiferromagnetic superlattices: anisotropic band and spin-valley valve in buckled two-dimensional materials

Antiferromagnetic superlattices (AFSL) are proposed based on the buckled hexagonal two-dimensional materials, which can be realized by the proximity effect of the periodically deposited antiferromagnets. It is found that the AF proximity effect can give rise to valley-polarized minibands and conductance, which are not held under ferromagnetic proximity. The spin degeneracy and valley degeneracy are lifted simultaneously in the presence of AF proximity and electric field. In consequence, both minibands and conductance could be spin-valley polarized completely in AFSL. The symmetry of spin-valley polarization is analysed by considering the pseudospin rotation operations and spatial inversion operations. Furthermore, AFSL also induce a highly anisotropic band structure due to the spin-orbit coupling (SOC). In particular, the group velocity parallel to the periodic direction of AFSL is greatly renormalized, while the velocity perpendicular to the periodic direction remains unaffected, contrary to that observed in graphene superlattices. With the increase of SOC, the anisotropy becomes more prominent, leading to flattened band and electron supercollimation. The direction of anisotropy can be regulated by adjusting the potential and SOC. These findings offer an alternative approach to engineering anisotropic two-dimensional materials. As an application, the AFSL may well work as a symmetry-protected spin-valley valve easily controlled by the gate voltages.