Symmetry breaking induced nonrelativistic spin splitting and spontaneous valley polarization in altermagnetic Ca(CoN)2 bilayer

Abstract

Two-dimensional altermagnet (AM) has attracted extensive attention due to its intriguing nonrelativistic spin-splitting combined with compensated magnetism. The manipulation of spin-splitting and valley polarization is crucial for both spintronic and valleytronic applications. Using first-principles calculations, we predict that the completely spin-polarized bands and intrinsic valley polarization can be realized in the Ca(CoN)2 altermagnet bilayer by modulating its stackings and magnetic configurations. The Ca(CoN)2 bilayer preserves AM magnetic configuration for each sublayer and antiferromagnetic interlayer coupling. We theoretically demonstrate the possibility of manipulating both spin splitting and valley polarization of the bilayer. Moreover, a valleytronic device based on the Ca(CoN)2 bilayer is proposed to achieve anomalous valley Hall effect. Our finding provides a route to obtain a distinct and tunable spin-splitting by using an altermagnetic bilayer, which could be helpful for the computational design of spintronic and valleytronic devices.