Nonrelativistic spin splittings and altermagnetism in twisted bilayers of centrosymmetric antiferromagnets

Magnetism-driven nonrelativistic spin splittings (NRSS) are promising for highly efficient spintronics applications. Although 2D centrosymmetric (in four-dimensional spacetime) antiferromagnets are abundant, they have not received extensive research attention owing to symmetry-forbidden spin polarization and magnetization. Here, we demonstrate a paradigm to harness NRSS by twisting the bilayer of centrosymmetric antiferromagnets with commensurate twist angles. We observe $i$-wave altermagnetism and spin-momentum locking by first-principles simulations and symmetry analysis on prototypical MnPSe$_3$ and MnSe antiferromagnets. The strength of NRSS (up to 80 meV\AA) induced by twisting is comparable to SOC-induced linear Rashba-Dresselhaus effects. The results also demonstrate how applying biaxial strain and a vertical electric field tune the NRSS. The findings reveal the untapped potential of centrosymmetric antiferromagnets and thus expand the material's horizons in spintronics.