Nonrelativistic Spin-Momentum Coupling in Antiferromagnetic Twisted Bilayers.

ABSTRACT

Spin-momentum coupling, which depends strongly on the relativistic effect of heavy elements in solids, is the basis of many phenomena in spintronics. In this Letter, we theoretically predict nonrelativistic spin-momentum coupling in two-dimensional materials. By proposing magnetic symmetry requirements for spin splitting in two-dimensional systems, we find that a simple twisting operation can realize nonrelativistic spin splitting in antiferromagnetic bilayers. Through first-principles calculations, we demonstrate that momentum-dependent spin splitting exists extensively in antiferromagnetic twisted bilayers with different crystal structures and twist angles. The size of the spin splitting caused by twisting is of the same order of magnitude as that arising from spin-orbit coupling. In particular, a transverse spin current with an extremely high charge-spin conversion ratio can be generated in twisted structures under an external electric field. The findings demonstrate the potential for achieving electrically controlled magnetism in materials without spin-orbit coupling.